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SLAC NATIONAL ACCELERATOR LABORATORYACCELERATOR RESEARCH DIVISION

April, 2011

FY2011-Q2 Quarterly Report (Jan-Mar, 2011)* department mission statements and function in blue, publications in dark red

Table of Contents:

1. ARD Administration 2

2. Advanced Accelerator Research Department 3 AARD – Microwave 3 AARD – Plasma 4 AARD – Laser 4 AARD – Feedback & Dynamics 6

3. Beam Physics Department 6 Collective Effects 6 FEL Physics 8 Advanced Computation 10 Beam Optics & Non-Linear Dynamics 11

4. Accelerator Design Department 13 ILC Systems R&D 13 ILC RF Systems 15 FNAL Project-X 16 X-Band 16 LARP 17 SuperB 18 End Station A 18

5. Accelerator Physics & Engineering Department 20 ATF2 21 CTF3 21 FACET 21 LCLS 22 LCLS-II 23 LHC 23 NLCTA 23

6. Test Facilities Department 23 ASTA 24 NLCTA 24 FACET User Area 25 End Station A 25 End Station B 25 ECHO Experiments 25

A U.S. Department of Energy Research Facility Operated Under Contract by Stanford University

Accelerator Research Division Quarterly Report – 2001/Q1

1. ARD Administration

The Accelerator Research Division (ARD) is a division within SLAC’s Accelerator Directorate. The division is supported with an annual budget of roughly 40 M$ from the US Department of Energy, Offices of Basic Energy Science and High Energy Physics. It consists of roughly 110 physicists, engineers and technicians, including 5 Stanford faculty members, and is divided into five departments:

Advanced Accelerator Research Beam Physics Accelerator Design Accelerator Physics and Engineering Test Facilities

ARD’s mission is to develop accelerator science and technology that will enable new accelerators in photon science and high energy physics as well as other fields of science, medicine and industry with R&D aimed at near-term, mid-term, and long-term development. It has a world renowned research program in advanced acceleration techniques and is engaged in R&D on some of the most advanced accelerators in the world including the Large Hadron Collider at CERN and the Linac Coherent Light Source at SLAC. The division operates three test facilities dedicated to accelerator research: the Accelerator Structure Test Area, the NLC Test Accelerator and the FACET facility.

This report is intended to highlight ARD’s research program and describe progress and advances made in the previous fiscal quarter. Its intended audience is the Directorate and Laboratory management. In addition it is will help ARD staff understand the breadth and strength of the division research program and work that their colleagues are engaged in.

General and more specific information about ARD can be found in:

slacportal.slac.stanford.edu/sites/ard_public/Pages/Default.aspx

and the ARD organization chart is shown in:

slacportal.slac.stanford.edu/sites/ard_public/SiteCollectionDocuments/ARDOrgChart-feb-2011-v2.pdf.

The Invited Accelerator Seminars during the quarter were: Mike Borland, APS, “A Comparison of Ultimate Storage Rings as Next Generation X-ray

Sources” Claudio Pellegrini, UCLA, “Fifth Generation FEL Light Sources” David Robin, LBL, “Novel Design of Gantry Optics for Carbon Cancer Therapy Accelerator” Pietro Musumeci, UCLA, “The Development of Relativistic Ultrafast Electron Diffraction: Using

Particle Accelerators to Watch Atoms Move in Real Time” Steve Geer, FNAL, “Muon Collider R&D”

These talks are posted on slacportal.slac.stanford.edu/sites/ard_public/ardhq/seminars/Pages/default.aspx.

FACET Construction At the end of the Q1, the FACET project was 80% complete and held 1.3M$ of management reserve on an estimated cost to complete of 2.6M$. Mechanical installation in Sector 20 began in late Q1 and continued through Q2. At the end of March the project was 93% complete and held 400K$ of reserve on an estimated cost to complete of 1M$. It is expected that FACET construction will be complete in early May, 2011 with first beam in mid-June.

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https://portal.slac.stanford.edu/sites/ard_public/ardhq/seminars/Pages/default.aspx

https://portal.slac.stanford.edu/sites/ard_public/SiteCollectionDocuments/ARDOrgChart-feb-2011-v2.pdf

https://portal.slac.stanford.edu/sites/ard_public/Pages/Default.aspx


2. Advanced Accelerator Research Department

The Advanced Accelerator Research Department (AARD) is dedicated to basic and applied research in accelerator science with the goals of advancing the state-of-the-art and educating accelerator scientists. Our investigations lie at the forefront of accelerator physics, and incorporate a wide variety of fields ranging from microwave engineering, plasma physics, electromagnetic theory, and ultra-fast lasers to physical optics, materials science, formal control theory, ultrafast electronics, and nanofabrication engineering and design. AARD efforts focus on understanding and extending the limits of accelerator technology to expand capabilities in energy, luminosity, beam power, and timescale to extend the reach of discovery science. Primarily developed for High Energy Physics and Basic Energy Science, these accelerator technologies will also benefit medicine, food safety, biology, and homeland security.

The department consists of four groups focusing on the four main research directions:

Microwave : Development of normal conducting accelerators and power sources, with a focus on understanding the limitations in high-gradient and high-frequency microwave structures.

Plasma: Use of short, intense pulses of electrons and positrons to create waves in a plasma (ionized gas) capable of producing orders of magnitude higher accelerating gradients than traditional accelerators

Laser: Investigation of techniques for accelerating electrons and positrons using lasers and dielectric microstructures, with acceleration gradients orders of magnitude larger than traditional accelerators

Feedback & Dynamics: Development of novel ultrafast and wide-bandwidth electronic circuits, signal processing systems, and laboratory measurement techniques for particle accelerators

AARD – Microwave Group:

Structure Manufacturing Technology (Collaborative work with CERN & KEK)o Coordinated the work for two TD24_VG1.8 structures. Finished construction: Structure with

SLAC flanges will be vacuum backed and tested at NLCTA, Structure with KEK flanges will be held pending discussions with KEK.

o Completed one each from deflector structures T11 and T27. They have been installed at NLCTA for the Echo-7 experiment.

o Worked to produce a T105 accelerator structure: Job submitted, needed machined parts sent for quotation, mechanical design for the copper is ongoing.

Novel Structure Designs o Working on a Mechanical design structure for test of optimized shaped cavity (three cells –

optimized cavity cell and two coupling cells)o Completed realistic design including initial mechanical design of accelerator cavity geometry

to be used in parallel-fed standing-wave accelerator structure.o Finalized the design and now manufacturing a cryogenic system to test normal-conducting

accelerating structures at cryo-temperatures are progressing.

High-Gradient Experimentso Testing a New PBG structureo Tested Hard-copper highest-shunt-impedance 1C-SW-A2.65-T2.0-Clamped-Cu-SLAC-#1.o Tested T18 Structure with a resonant ring

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Manufactured and delivered to collaborators:o Reiterated on hard-copper-cells for advanced coating to Yale.o Delivered Mode launchers for Argonne National Lab.

RF Undulatorso Tested RF undulator structure and compared it to simulations with exceptional agreements. o Designed a new type of end wall termination for the undulator with reduced fieldso Started looking a beam dynamics

Superconducting Material Researcho Continue testing new stratified media based on MgB2o Continue testing new Nb sampleso Testing the newly fabricated structure cavity for testing residual resistance.

Publicationso Roark A. Marsh Michael A. Shapiro, Richard J. Temkin, Valery A. Dolgashev, Lisa L.

Laurent, James R. Lewandowski, A. Dian Yeremian, Sami G. Tantawi, “X-Band Photonic Bandgap (PBG) Accelerator Structure Breakdown Experiment,” Phys. Rev. ST Accel. Beams 14, 021301 (2011) [11 pages].

o Lisa Laurent, Sami Tantawi, Valery Dolgashev, Chris Nantista, Yasuo Higashi, Markus Aicheler, Samuli Heikkinen, and Walter Wuensch, “Experimental Study of RF Pulsed Heating,” Phys. Rev. ST Accel. Beams – (accepted for publication).

AARD – Plasma Group:

Worked with TFD to develop an integrated layout of the FACET IP area that accommodates several experimental groups without the need for removal of experimental hardware between runs.

Worked with TFD and controls department to experimental protection system (EPS) and necessary interlocks and controls for the plasma oven.

Worked with beam physics department to develop alternate FACET optics to produce shaped drive bunches for high transformer ratio PWFA experiments at FACET.

Worked with beam physics department to develop optics multi-knobs to introduce x-z and y-z correlations on the beam at the plasma entrance to make parametric measurement of the electron hose instability.

Developed a configuration for installation of a one-meter long x-band deflecting cavity in the FACET beamline upstream of the IP that provides the required experimental resolution (30 fs) with existing infrastructure and nominal optics.

Completed SAREC review of FACET proposals – PWFA proposal received the highest possible rank from the committee (Excellent).

Delivered Two oral presentations, 6 posters and 7 presentations at PAC11 New York. Hosted FACET satellite meeting at PAC11 with 35 attendees.

AARD – Laser Group:

NLCTA Beam Testso Successfully detected wakefield radiation in 4 different photonic crystal test fibers excited by

the NLCTA electron beam.

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o A near-IR spectrometer was used to spectrally analyze the radiation from one of the commercial fibers within the bandgap region, providing first demonstration of e-beam coupling to TM modes in an optical scale photonic crystal structure.

A Mach-Zehnder Interferometer was adapted for use with a free-space TEM01* mode, with the intention of measuring phase length dependence on temperature for TM rather than TE fiber modes. A TM mode was successfully excited and observed.

Designs completed and parts ordered for construction of a tunable optical parametric oscillator (OPO) to be used for alignment testing of prototype silicon woodpile accelerator structures in the 4 to 5 micron wavelength region.

Silica gratings with the proper aspect ratio and line spacing for 800nm wavelength operation were successfully fabricated, and techniques were explored for making a spacer layer to separate two gratings to create a prototype accelerator structure.

Simulations conducted of newly proposed laser-driven dielectric structure for transverse confinement of electron beams showing successful excitation of focusing fields by an externally coupled Gaussian laser pulse.

Simulations performed to model various components of coupling schemes for the woodpile accelerator structure, indicating up to 70% coupling efficiency from free space Gaussian mode to on-chip silicon waveguides and 95% efficiency for coupling to accelerating channel by a side-coupled photonic crystal waveguide T-junction.

Publications and Talks:o Invited Talk at PAC11 Conference, "Experiment to Demonstrate Acceleration in Optical

Photonic Bandgap Structures," R. J. England, et. al.o E. R. Colby et al., "A Laser-Driven Linear Collider: Sample Machine Parameters and

Configuration," PAC11 proceedings.o C. M. McGuinness, et al., "Fabrication and Measurement of a Silicon Woodpile Accelerator

Structure," PAC11 proceedings.o J. E. Spencer, et al., "Coupler Studies for a PBG Fiber Accelerator," PAC11 proceedings.o K. Soong, et al., "Experimental Determination of Damage Threshold Characteristics of IR

Compatible Optical Materials," PAC11 proceedings.o R. Laouar, et al., "Measurement of Thermal, Stress, and Field Dependencies of PBG Fiber

Properties," PAC11 proceedings.o E. Peralta, et al., "Fabrication and Measurement of Silica Grating Accelerator Structures,"

PAC11 proceedings.o Z. Wu, et al., "Design of On-Chip Power Transport and Coupling Components for a Silicon

Woodpile Accelerator", PAC11 proceedings.

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AARD – Feedback and Dynamics Group:

Integration of realistic feedback model into CMAD particle dynamics code - allows evaluation of instability dynamics, impact of realistic feedback ( bandwidth limits, offsets, noise)

Testing of 100W 1 GHz amplifiers for upcoming SPS MD - intergration of power stages into 4 GS/sec. excitation system

LHC MD results focused on longitudinal diffusion from RF system noise

Sho Uemura ( Stanford Physics) has joined the group as a student RA.

Publications and Talks:

o Themis Mastorides presented his contributed talk "Studies of RF Noise Induced Bunch Lengthening at the LHC", PAC11

o Ozhan Turgut, "Estimation of Ecloud and TMCI Driven Vertical Instability Dynamics from SPS MD Measurements - Implications for Feedback Control”, PAC11

o C. Rivetta, J. Fox, T. Mastorides, M. Pivi, O. Turgut, W. Hofle, R. Secondo, J-L. Vay."Mathematical Models of Feedback Systems for control of intra-bunch instabilities driven by E-Clouds and TMCI", PAC11

3. Beam Physics Department

The mission of the Beam Physics Department (BPD) is primarily focused on beam theory. There are three beam dynamics groups: Collective Effects, FEL Physics, and Beam Optics & Nonlinear Dynamics. These groups supports the operating accelerators at SLAC and studies beam physics that can enable or limit future accelerators and its members work closely with other ARD groups and programs. BPD also contains the Advanced Computation Group. This group develops massively parallel computing techniques to solve problems in beam physics. It supports accelerator programs at SLAC as well as across the US. The R&D enables improved understanding of accelerator phenomena through simulation and allows a cost-effective accelerator design process through extensive calculation.

Collective Effects:

Daniel Ratner successfully graduated with thesis defense. Systematic studies of the emittance exchange. A method is proposed to achieve exact phase space

exchange, i.e. mapping x to z, x' to delta, z to x and delta to x'. The work is documented in a PAC11 proceedings paper.

A triple modulator-chicane scheme for seeding FELs is proposed. The scheme has the advantage that ultrahigh harmonics can be generated while simultaneously keeping the energy spread growth much smaller than beam's initial slice energy spread. The paper is submitted to New Journal of Physics.

Work on noise and coulomb collision effects in the EEHG. Work continued on ECHO-7 commissioning. The 5th harmonic at 318 nm with the EEHG

technique was observed in January 2011 and in the following months the in-vacuum UV spectrometer was tested and observed coherent harmonic radiation at 266 nm from the 800 nm seed laser.

Work on foil emittance partitioning.

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Work on CSR calculations using direct numerical solution of Maxwell’s equations. Work on wakefield calculation in the interaction region of the ILC. Study dynamic aperture on low emittance (7nm) optics of SPEAR3; Study of synchrotron oscillation on cross-correlation on the bunch length measurement in

SPEAR3 Study of the beam ion instability in SPEAR3 Principle study on LCLS fs bunch length measurement using ionization electrons Simulation of electron cloud in CESRTA

Talks and papers (with abstracts):

o G. Stupakov, K. Bane and I. Zagorodnov. “Impedance scaling for small angle transitions”, Phys. Rev. ST Accel. Beams 14, 014402 (2011). Abstract: Based on the parabolic equation approach to Maxwell’s equations, we have derived scaling properties of impedance that apply either to (1) structures of general shape at high frequencies, or (2) small angle transitions at all frequencies. Applying these scaling properties to impedance/wakefield calculation of long, small angle, beam pipe transitions, like one often finds in insertion regions of storage rings, one can greatly reduce the computer resource required. We have tested the scaling with wakefield simulations of 2D and 3D models of such transitions, and have found that it appears to work well.

o Michael P. Dunning et al. "Status and Upgrades of the NLCTA for Studies of Advanced Beam Acceleration, Dynamics, and Manipulation", PAC 2011. Abstract: The Next Linear Collider Test Accelerator (NLCTA) is a low-energy electron accelerator (120 MeV) at SLAC that is used for ultra-high gradient X-band RF structure testing and advanced accelerator research. Here we give an overview of the current program at the facility, including the E-163 direct laser acceleration experiment, the echo-enabled harmonic generation (EEHG) FEL experiment, narrow-band THz generation, coherent optical transition radiation (COTR) studies, microbunching instability studies, and X-band structure testing. We also present the upgrades that are currently underway and some future programs utilizing these upgrades, including extension of the EEHG experiments to higher harmonics, and an emittance exchange experiment.

o Dao Xiang et al. "Experimental Demonstration of the Echo-enabled Harmonic Generation Technique for Seeded FELs", PAC 2011. Abstract: Recently the scheme of echo-enabled harmonic generation (EEHG) was proposed for short wavelength seeded FELs. This scheme allows far higher harmonic numbers to be accessed and makes the generation of coherent soft x-ray directly from a UV seed laser in a single stage possible. In this paper we present the experimental demonstration of this echo harmonic technique at the Next Linear Collider Test Accelerator (NLCTA) at SLAC, where the coherent radiation at the harmonic frequency of the seed laser is generated using the 120 MeV electron beam. The experiment confirms the physics behind this technique and paves the way for applying it for seeded x-ray FELs.

o B. Podobedov and G. Stupakov. "Calculating Point-Charge Wakefields from Finite Length Bunch Wake-Potentials", PAC 2011. Abstract: Starting from analytical properties of high frequency geometric impedance we show how one can accurately calculate short bunch wake-potentials (and even point-charge wakefields ) from time domain calculations performed with a much longer bunch. In many practical instances this drastically reduces the need for computer resources, speeds up the calculations, and improves their accuracy. To illustrate this method we give examples for accelerator structures of various complexities in both 2D and 3D.

o A. Novokhatski. "CSR Fields from using a Direct Numerical Solution of Maxwell's Equations", PAC 2011. Abstract: Using a previously developed method to numerically

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calculate electromagnetic fields of very short bunches we simulate coherent synchrotron radiation (CSR) in a rectangular bending magnet vacuum chamber. Initial results clearly show the first part of the CSR - magnet edge radiation. The transverse shape of this part looks very similar to the screen images, seen after the dump magnets at the SLAC LCLS. As an ultra-relativistic bunch and the CSR fields have almost the same propagation velocity they essentially move together and interact for a long time until the bunch goes into another beam chamber. The CSR edge radiation part continues to propagate straight ahead.

o A. Novokhatski. "Wake Potentials in the ILC Interaction Region", PAC 2011. Abstract: The vacuum chamber of the ILC Interaction Region (IR) is optimized for best detector performance. It has special shaping to minimize additional backgrounds due to the metal part of the chamber. Also, for the same reason this thin vacuum chamber does not have water cooling. Therefore, small amounts of power, which may be deposited in the chamber, can be enough to raise the chamber to a high temperature. One of the sources of “heating” power is the electromagnetic field of the beam. We will consider three ways in which power can be transferred from the beam. They are: image current losses, losses due to propagating wake fields, which stay for a short time in the IR and losses from trapped modes, which may stay for a long time. To calculate these effects we use analytical formulas; wake field code NOVO and Eigen mode calculations with MAFIA.

FEL Physics:

Finalized LCLS-II CDR and prepared for CDR review.

A single-shot electron bunch length measurement technique has been tested on the LCLS with ~1 fs resolution achieved.

A new method is developed to measure the ultra-short soft x-rays pulse length through the analysis of the statistical properties of the SASE FEL spectra. The method has been experimentally demonstrated at LCLS. Different x-ray bunch lengths have been measured keeping the electron bunch charge fixed at 250 pC and manipulating the peak current from 1.5 kA to 3kA. Bunch length has been also measured for different number of undulators. Finally using the slotted foil to obtain shorter pulses, x-ray pulse lengths down to 13 fs FWHM have been measured.

Investigated the use of x-band deflector to measure single-shot fs electron and x-ray pulse duration that is applicable to wide operating conditions.

Worked on optimizing the undulator tapering in a self-seeding scheme to reach terawatts (TW) FEL for LCLS-II. Empirical solution to have a TW FEL is found to be feasible within the planned upgrade scheme for the LCLS-II undulator system. Analytical estimate and simulation code development within Genesis are ongoing.

Studied the scheme of introducing density modulation on the electron bunch before it enters the undulator. The density modulation period has been compressed to nm level to generate coherent soft X-rays.

Developed a general 3D FEL theory when the transverse beam size varies in the undulator.

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Paper published or submitted:o “GENERATION OF COHERENT X-RAY RADIATION THROUGH MODULATION

COMPRESSION” Ji Qiang (LBL), J. Wu, Nuclear Instruments and Methods A, 2011.03.020. Abstract: In this paper, we propose a scheme to generate tunable coherent X-ray radiation for future light source applications. This scheme uses an energy chirped electron beam, a laser modulator, a laser chirper and two bunch compressors to generate a prebunched kilo-Ampere current electron beam from a few tens Ampere electron beam out of a linac. The initial modulation energy wavelength can be compressed by a factor of 1+hbRa56 in phase space, where hb is the energy bunch length chirp introduced by the laser chirper, Ra56 is the momentum compaction factor of the first bunch compressor. As an illustration, we present an example to generate more than 400 MW, 170 attoseconds pulse, 1 nm coherent X-ray radiation using a 60 A electron beam out of the linac and 200 nm laser seed. Both the final wavelength and the radiation pulse length in the proposed scheme are tunable by adjusting the compression factor and the laser parameters.

o “MEASUREMENT OF FEMTOSECOND LCLS BUNCHES USING THE SLAC A-LINE SPECTROMETER” Z. Huang et al., PAC2011 proceedings. Abstract: We describe a novel technique and the preliminary experimental results to measure the ultrashort bunch length produced by the LCLS low-charge, highly compressed electron bunch. The technique involves adjusting the LCLS second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result, the time coordinate of the bunch is directly mapped onto the energy coordinate at the end of the linac. A high-resolution energy spectrometer located at an existing transport line (A-line) is then commissioned to image the energy profile of the bunch in order to retrieve its temporal information. We present measurements of the single-digit femtosecond LCLS bunch length using the A-line as a spectrometer and compare the results with the transverse cavity measurement as well as numerical simulations.

o “TECHNICAL CHALLENGES IN THE LINAC COHERENT LIGHT SOURCE, COMMISSIONING AND UPGRADES” J. Galayda, Z. Huang et al, invited talk at PAC2011. Abstract: Five months after first lasing in April 2009, the Linac Coherent Light Source (LCLS) began its first round of x-ray experiments. The facility rapidly attained and surpassed its design goals in terms of spectral tuning range, peak power, energy per pulse and pulse duration. There is an ongoing effort to further expand capabilities while supporting a heavily subscribed user program. The facility continues to work toward new capabilities such as multiple-pulse operation, pulse durations in the femtosecond range, and production of >16 keV photons by means of a second-harmonic “afterburner” undulator. Future upgrades will include self-seeding and polarization control. The facility is already planning to construct a major expansion, with two new undulator sources and space for four new experiment stations.

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Advanced Computation Group

Three talks were given in PAC11, including an invited talk about the simulation of the two-beam acceleration system.

o Invited talk: “NUMERICAL VERIFICATION OF THE POWER TRANSFER AND WAKEFIELD COUPLING IN THE CLIC TWO-BEAMACCELERATOR” A. Candel, Z. Li, C. Ng, V. Rawat, G. Schussman and K. Ko, SLAC I. Syratchev, A. Grudiev and W. Wuensch, CERN Abstract: The Compact Linear Collider (CLIC) provides a path to a multi-TeV accelerator to explore the energy frontier of High Energy Physics. Its two-beam accelerator (TBA) concept envisions complex 3D structures, which must be modeled to high accuracy so that simulation results can be directly used to prepare CAD drawings for machining. The required simulations include not only the fundamental mode properties of the accelerating structures but also the Power Extraction and Transfer Structure (PETS), as well as the coupling between the two systems. Time-domain simulations will be performed to understand pulse formation, wakefield damping, fundamental power transfer and wakefield coupling in these structures. Applying SLAC’s parallel finite element code suite, these large-scale problems will be solved on some of the largest supercomputers available. The results will help to identify potential issues and provide new insights on the design, leading to further improvements on the novel two-beam accelerator scheme.

o “High Fidelity Calculation of Wakefields for Short Bunches” C.-K. Ng, A.E. Candel, K. Ko, V. Rawat, G.L. Schussman, L. Xiao, SLAC, Menlo Park, California. Abstract: The determination of wakefields for short bunches in accelerator structures with complex geometries and large spatial dimensions requires significant computational resources. The time domain code T3P developed at SLAC employs the higher-order finite element method for high fidelity modeling and parallel computation for large-scale simulation on state-of-the-art supercomputers. To facilitate wakefield calculation for short bunches, T3P has been enhanced through the implementation of a moving window technique which reduces computing resource requirements by orders of magnitude. For local refinement in the moving window, both a finer unstructured mesh and higher-order finite element basis functions can be employed. Applications demonstrating the efficacy of the technique include wakefield calculations of shallow tapers in storage rings, complex and long vacuum chamber transitions in energy recovery linacs (ERL) and higher-order-mode (HOM) couplers in superconducting rf cavities.

o “On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams”, Zenghai Li, Feng Zhou, Arnold Vlieks and Chris Adolphsen, SLAC. Abstract: The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun, being jointly designed with LLNL, and the X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.

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Beam Optics & Non-Linear Dynamics

We have completed the ERL configuration study. The results of the study were documented in two papers presented in the PAC 11.

We continued to design an ultimate storage ring based on the PEP tunnel. Since the last report, we have added damping wigglers to reduce the equilibrium emittance further down to 15 pm-rad . Emittance growth due to the intra-beam scattering was about a factor of two at 200 mA beam current. This extremely low emittance makes the Touschek lifetime much longer than one hour. That is significant improvement from the baseline design. Currently, we are optimizing the dynamic aperture of the lattice.

Publications and Talks

o R. Hettel et al. "Status of the PEP-X Light Source Design Study", PAC 2011. Abstract: The SLAC Beam Physics group and collaborators continue to study options for implementing a near diffraction-limited ring-based light source in the 2.2-km PEP-II tunnel that will serve the SSRL scientific program in the future. The study team has completed the baseline design for a 4.5-GeV storage ring having 160-pm-rad emittance with stored beam current of 1.5 A, providing >1022 brightness for multi-keV photon beams from 3.5-m undulator sources. The team is now investigating possible 5-GeV ERL configurations which, similar to the Cornell and KEK ERL plans, would have ~30 pm-rad emittance with 100 mA current, and ~10 pm-rad emittance with 25 mA or less. In the next year, a diffraction-limited storage ring using on-axis injection in order to reach 30 pm-rad or less emittance will be investigated. An overview of the PEP-X design study and SSRL’s plans for defining the performance parameters that will guide the choice of implementation options is presented.

o “OPTICS TUNING KNOBS FOR FACET” Y. Nosochkov, M.J. Hogan, W. Wittmer: Abstract: FACET is a new facility under construction at the SLAC National Accelerator Laboratory. The FACET beam line is designed to provide 23 GeV tightly focused and compressed electron and positron bunches for beam driven plasma wakefield acceleration research and other experiments. Achieving optimal beam parameters for various experimental conditions requires the optics capability for tuning in a sufficiently wide range. This will be achieved by using optics tuning systems (knobs). Design of such systems for FACET is discussed.

o “LATTICE DESIGN FOR ERL OPTIONS AT SLAC” Y. Nosochkov, Y. Cai, X. Huang, M.-H. Wang: Abstract: SLAC is investigating long-range options for building a high performance light source machine while reusing the existing linac and PEP-II tunnels. One previously studied option is the PEP-X low emittance storage ring. The alternative option is based on a superconducting Energy Recovery Linac (ERL) and the PEP-X design. The ERL advantages are the low beam emittance, short bunch length and small energy spread leading to better qualities of the X-ray beams. Two ERL configurations differed by the location of the linac have been studied. Details of the lattice design and the results of beam transport simulations with the coherent synchrotron radiation effects are presented.

o “COMPENSATION OF DETECTOR SOLENOID IN SUPER-B” Y. Nosochkov, K. Bertsche, M. Sullivan. Abstract: The SUPER-B detector solenoid has a strong 1.5 T field in the Interaction Region (IR) area, and its tails extend over the range of several meters. The main effect of the solenoid field is coupling of the horizontal and vertical betatron motion

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which must be corrected in order to preserve the small design beam size at the Interaction Point. The additional effects are orbit and dispersion caused by the angle between the solenoid and beam trajectories. The proposed correction system provides local compensation of the solenoid effects independently for each side of the IR. It includes “bucking” solenoids to remove the solenoid field tails and a set of skew quadrupoles, dipole correctors and anti-solenoids to cancel linear perturbations to the optics. Details of the correction system are presented.

o “FACET Emittance Growth” J. Frederico, M. J. Hogan, Y. Nosochkov, M. Litos, T. Raubenheimer. Abstract: FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to ~20 micrometer long and ~10 micrometer wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.

o “SYNCHROTRON LIGHT OPTIONS AT SUPER-B” Walter Wittmer, Yuri Nosochkov, Alexander Novokhatski, John Seeman, Michael K. Sullivan (SLAC), Maria Enrica Biagini, Pantaleo Raimondi (INFN/LNF). Abstract: The Super-B facility will collide electron and positron beams with different characteristics as done in the past at PEP-II and KEKB. The ring and electron (positron) beam characteristic of both high and low energy rings of the Super-B are comparable to NSLS-II and other state of the art synchrotron light sources. This suggests the use of this facility, either parasitically or in dedicated runs, as light source. In this paper we compare the characteristics of the synchrotron light generated at Super-B with existing, in construction and proposed facilities. We investigate different schemes to incorporate the generation of synchrotron radiation in the collider lattice design and look at different beam line layouts for users.

o “SUPERB: THE NEXT-GENERATION e+e- B-FACTORY COLLIDER” W. Wittmer, A. Novokhatski, K. Bertsche, Y. Nosochkov, J. Seeman, M. K. Sullivan, U. Wienands (SLAC), A.V. Bogomyagkov, E. Levichev, S. Nikitin, P. Piminov, D. Shatilov, S. Sinyatkin, P. Vobly, I.N. Okunev (BINP), B. Bolzon, L. Brunetti, A. Jeremie (IN2P3 LAPP), M.E. Biagini, R. Boni, M. Boscolo, T. Demma, A. Drago, M. Esposito, S. Guiducci, S. Liuzzo, M. Preger, P. Raimondi, S. Tomassini, M. Zobov, E. Paoloni, P. Fabbricatore, R. Musenich, S. Farinon (INFN/LNF), S. Bettoni (CERN), F. Poirier, C. Rimbault, A. Variola (LAL), M. Baylac, O. Bourrion, N. Monseu, C. Vescovi (LPSC), A. Chanc (CEA). Abstract: The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10^36 cm^-2 sec^-1. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the upsilon(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low betay. without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a

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higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications.

4. Accelerator Design Department

The Accelerator Design Department (ADD) is focused on the design of normal conducting and superconducting linear colliders and the development of the required technology. In addition, the department investigates applications of these technologies that may enable other facilities such as Project-X as well as other SLAC facilities. This R&D is aimed at a next generation TeV-scale linear collider but may have application to compact light sources, industrial and medical accelerators.

ILC Systems R&D:

o In FY11, about 20 SLAC physicists attended the IWLC meeting in Geneva in October, and 12 SLAC physicists attended the ALCPG meeting in Eugene in March. They also attended meetings of the IDAG and AAP and participated in the change control review process.

o Electron Source: The group received the KMLabs laser produced under an SBIR at the end of Q1. A pair of 18W, 515 nm pump lasers will be incorporated into the final stage amplifier of the KMLabs system to increase the laser output to 3 MHz.

o Damping Rings: The electron cloud Working Group gave a preliminary recommendation for ecloud mitigation in Q1. The WG is now preparing a detailed report due by early 2012. There was also work on the 3.2 km damping ring design, including optics, dynamic aperture and simulations to assess the impact of reducing the bunch spacing to 3ns. For the CesrTA program, there was continued work on ecloud build-up simulations and on instability simulations. This work will be part of the CesrTA phase I report.

o Accelerator Physics: In FY11, this has mainly involved studies related to the proposed cost-saving changes to the baseline design that impact the linacs. In particular, studies were done on the (1) rf overhead needed to accommodate the ~ 20% spread in sustainable cavity gradients, (2) configuration of the KCS and RDR rf distribution systems for operation with half the number of bunches per pulse and (3) operation at higher repetition rates at lower beam energies, in particular, running at 10 Hz with 125 GeV per beam ‘collision’ pulses interleaved with 150 GeV electron beam pulses that produce positrons at the end of the electron linac.

o Machine Detector Interface: The MDI group continued to study the performance of a platform-based support for the SiD detector and concluded that such a solution was indeed allowable, given the inter-bunch feedback system. A document “Functional Requirements of a SiD Platform” was presented at the ALCPG meeting in Eugene Oregon in March 2011. Progress on this front was labeled one of the most significant accomplishments of the meeting.

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An analysis of HOM induced heating near the IP was completed and presented at the ALCPG, taking into account the detailed engineering design of the beam pipe in the 7m surrounding the interaction point. For the ILC bunch structure and bunch length, neither trapped mode nor resistive wall heating appears to be a problem.

The paperwork required to transfer funds to the University of Michigan to develop a frequency scanning interferometer based alignment system was completed. Results from new hardware should be available by the time of the next report.

o ATF2 Test Facility : At least 2 members of the SLAC ATF2 team participated in all beam operations during January – March 2011. Beam operations stopped March 11 due to the M9.0 earthquake in Eastern Japan; we expect full operations to commence again from fall, 2011, after reconstruction and realignment work is completed. There was an ATF2 collaboration meeting at SLAC in January to discuss progress towards the main ATF2 goals.

The targets on the 4 OTR systems were replaced with Al and Aluminized Kapton targets. The OTR system is now fully operational and routinely used during tuning operations with a measurement time of <2 mins (compared with many hours with the wirescanner system).

SLAC is taking a leading role in the development of the readout system for the IP region cavity BPMs which need to read out the position of the electron beam at the IP waist to very high precision; ideally <2nm vertically. This will be based on the SLAC digitizer boards developed for LCLS BPMS

SLAC has worked together with magnet engineers at KEK to now have an accurate computer model of the ATF2 beamline including a precise description of the measured sextupole and octupole fields in all the ATF2 magnets. This data will be used to optimize the ATF2 optics to account for these fields and develop a new magnetic configuration of the machine for future runs.

o Ultra-fast ATF2 Extraction Kicker: Progress has been made on demonstrating a new topology to eliminate the pre-pulse and there was a brassboard circuit demonstration of the output pulse. A vendor to fabricate a second generation hybrid has been identified and a conceptual design for an ultra-fast discrete component driver developed.

o High Availability Controls: The Marx P2 interlock design requirements, design and prototype fabrication are complete except for high level software. The companion analog Rear Transition Module board is designed and beginning layout.

The major labs in the MicroTCA Standards collaboration now include CERN, DESY, FNAL, IHEP, IPFN, ITER, LBNL and SLAC, with ESSB (European Spallation Neutron Source Bilbao) in process of joining. Standards are being reviewed for the MicroTCA extension now known as PICMG MTCA.4, for the Rear Transition Module (RTM) interface ATCA PICMG3.8, and on a guideline for a distribution system for precise timing and triggers on the large-system backplane. The operating system under Linux is developed and operational including hot-swap capability. MicroTCA was proposed both for the RF and main linac upgrades needed for LCLS I&II and future experiments using the linac.

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ILC RF system: The SLAC effort is focused mainly on developing lower cost and more reliable rf components for the main linacs. Areas of research include:

o Marx Modulator: The P1 Marx backplane was replaced with a more robust version to reduce corona damage. Also, the P1 Marx continued operation 24/7 at half pulse width while the capacitor lifetime problem was being studied in a separate test stand. During the > 1000 hours of operation of the P1 at this narrower pulse width, there have been few faults and no measureable loss of capacitance. All of the major components for the P2 Marx have been purchased, and the upgrade of DTI Marx has started.

o Global RF Distribution: The windows and some of the rectangular waveguide were upgraded on the 10 m ‘Big Pipe’ section. It recently ran for over 100 hours with no breakdown at 265 MW (at the 280 MW design power, there is a breakdown every few hours). With HEEC approval, the pipe pressure will be increased from 15 psig to at least 18 psig to see if this allows for stable operation at higher power. For Phase II of this project, requests for bids for 80 m of new pipe (rated for 30 psig) were placed and a preliminary design completed for a support system to mount the pipe. Also, the rf design for the required 90 degree waveguide bend is nearly complete.

o Local RF Distribution: A second generation, 8-feed, variable power rf distribution system is being built for FNAL’s second cryomodule. This version has remote-controlled phase shifters to adjust the power split among the cavities. The first two- feed sub-unit has been cold tested and will be high power tested soon.

o Couplers: Two failed cold coupler sections returned to SLAC by FNAL were extensively examined. These couplers had been returned to CPI for repair after initial inspection at SLAC, and their resulting ‘fixes’ seem to have caused damage that lead to subsequent breakdown and copper removal problems at FNAL when they were eventually used to power SC cavities. Currently, the issue of copper particles coming loose during ultrasonic cleaning of the copper plated couplers is be examined. For this purpose, various samples (pure copper, CPI plated copper with and without bead blasting, and SLAC-plated copper) are being ultrasonically cleaned and the number of copper particles that come loose are being measured.

o For the ILC Electron Sources, a Kapteyn-Murnane Laboratories (KMLabs) ILC laser was shipped to SLAC in Q1 FY11. This laser system was developed by KMLabs under a SBIR Phase II proposal. Prior to shipment, this laser was observed to produce a full energy ILC source laser pulse train at 1.5 MHz. A pair of 18W, 515 nm pump lasers will be incorporated into the final stage amplifier of the KMLabs system to increase the laser output to 3 MHz. The plan developed in conjunction with JLab to demonstrate an ILC specification source beam at SLAC in FY11 and then at JLab in FY12 has been modified. SLAC will continue with the ILC source laser development while JLab continues development of a high voltage, high gradient ILC dc photogun. It has been agreed that SLAC will take the lead in the writing of the Electron Source chapter for the ILC Technical Design Report.

o For the ILC Damping Rings, SLAC is coordinating the international Working Group on the electron cloud R&D. The Working Group gave a preliminary recommendation for the electron cloud mitigation in October and it is now preparing a detailed report document due by early 2012. In collaboration with INFN Frascati, we worked on the DR optics and on the dynamic aperture for the selection of a baseline 3.2 km damping ring design to be included in

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the TDR-II. For the CesrTA program, we worked on build-up simulations for quadrupole and wiggler regions and worked on instability simulations to include radiation damping and more realistic electron cloud distributions over the CesrTA ring. This work will be part of the CesrTA Phase I report.

o For the ILC Machine Detector Interface (MDI) in FY11-Q2, seven MDI meetings took place and the results were presented at the ALCPG meeting in Eugene, Oregon in March 2011. Details of the weekly meetings are available at http://ilcagenda.linearcollider.org/categoryDisplay.py?categId=188.

At the ALCPG meeting the SiD collaboration committed itself to the concept of using a platform to accomplish push pull operations with the ILD detector. A list of functional requirements for the platform was developed and presented as input to the ILC Conventional Facilities group, who are responsible for the detailed engineering of the system. Work continued on measuring the vibration properties of various concrete blocks to validate the analysis models, a Frequency Scanning Interferometry (FSI) based alignment system, a re-evaluation of SR backgrounds, and an analysis of HOM induced heating near the IP. A grant request by U. Michigan for FSI work that was submitted to SLAC was finalized.

FNAL Project X: SLAC received 400 k$ in PX funding from FNAL for FY11. It will be used in part to study possible 650 MHz, 30 kW rf sources for the PX CW linac, in particular, to examine solid state sources, which are becoming cost competitive with IOTs. Recently, two US vendors provided cost estimates for 30 kW and 2 kW 650 MHz solid state sources. For the 3-8 GeV PX pulsed linac, possible long pulse (up to 25 ms) klystrons and modulators will be examined – currently design and cost studies of Marx modulators for this application are being done.

X-Band: The SLAC X-band program includes testing CLIC prototype structures, developing and testing a Dual Mode Cavity to better understand breakdown limitations, developing an X-band gun (with LLNL) and associated test beamline (XTA), upgrading the X-band systems at NLCTA in support of other programs there, developing X-band linac designs for light source applications and designing a more robust 50 MW XL4 klystron. Progress is summarized below.

o CLIC: The T24 structure was operated for an additional 100 hours longer but no improvement in breakdown rate was observed. The TD24 structure was assembled using cells provided by KEK, and will be tested next.

o Dual Mode Cavity: Stn 1 and Stn 2 were configured to power the two cavity modes independently. The results showed that the breakdown rate increased significantly for a fixed surface electric field when the pulsed heating from the TE mode was increased above about 50 degC. These results were presented at PAC11.

o X-band Gun: Construction was started for the 5.59 cell X-band gun (Mark 1) and assembly was completed of a partially fabricated gun (the 5.5 cell Mark 0) from an earlier project. This latter gun will be tested without beam in ASTA in FY11-Q3 to measure breakdown rates and dark currents. At LCLS, studies were done to improve the bunch emittance from their S-band gun by using a truncated-Gaussian-shaped laser pulse.

o XTA: A new beamline in NLCTA (called XTA) is being constructed to test X-band rf guns. The design for this beamline is nearly complete, a number of the parts have been ordered and

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http://ilcagenda.linearcollider.org/categoryDisplay.py?categId=188


the control system, which will use many of the data acquisition modules developed for LCLS, has been mostly defined.

o NLCTA Upgrades: The spectrometer magnet bend angle was increased (from 12 to 30 degrees) to improve resolution. Also, the fabrication of two deflecting cavities was completed and waveguide and other rf components (e.g., phase shifters and loads) that will power them from Stn 1 and Stn 3 were prepared.

o Light Sources: For an all-X-band linac, bunch energy linearization can be achieved using the T566 component of the first bunch compressor chicane if higher harmonic rf is not available. Several options for such a linearization system were simulated and shown to provide high current bunches similar to those in LCLS.

o Linac Optimization: A study was completed of optimized S, C and X-band TW structures for the cases of short (50 ns) and long (1250 ns) bunch train operation with low beam loading. The latter case is applicable to the proposed MaRIE project at LANL (they visited SLAC and we visited LANL this Quarter to discuss this project). The results show that X-band has the advantage of providing a higher gradient with equal (long pulse) or higher (short pulse) rf-to-beam efficiency. This work was presented in an invited talk at PAC11.

o XL4 Klystron: A program was started to design a longer (6 cell vs 4 cell) output section for the XL4 klystron with the goal reducing the surface fields by about 15% - this will hopefully lead to more robust operation of the tube at 50 MW. A design has been completed and currently studies are underway to see if other modes will be excited by the beam.

LARP: For the collimator project in FY11 Q2, we:

o Finished the final rotation tests of the 20-sided rotatable collimator jaws in test mode. Test mode means that the jaws were free to rotate without their cooling tubes attached to fixed points and forced to wind up during rotation. The baseplate with now welded steel jaw supports was lowered onto the two jaws while they rested on a granite table. The jaws were attached with the final version of the rotation bearing housing, nuts and spacers. The final versions of the rotation drives, anti-backlash pawl assemblies, rhodium coated RF "wipers", BeCu RF foils and thermistors holders were attached to the jaw ends. These last 3 items are designed to provide 0.1 mOhm resistance between the jaw surface and the end of the vacuum tank for each rotation of the jaw. This was tested and after considerable tuning, achieved. The post which holds the claw that actuates the rotation mechanism was welded to the baseplate. The jaw translation drive mechanism was checked for limits of travel and limit switches and various hard stops tuned for proper interaction with the actuator. The rotation actuation was reconfirmed under load. A fixture to rotate the entire assembly in phi was designed, built & installed. This allowed us to put the baseplate in the correct position for each test in a very safe and controlled manner. At this point everything was disassembled. Each end of each facet of each jaw had 3 lines scribed to allow for optical alignment through ports in the vacuum vessel and the jaw facets numbered with a punch. The cooling tubes coming out of the collimator jaws were carefully bent to 90 degrees.

o Completed final assembly and rotation tests in a mode where the tubes must be twisted during rotation (and thus the number of such tests are limited). The baseplate was lowered onto the jaws for a final time capturing the cooling tubes through minimal clearance feedthroughs in the baseplate. The jaws were reattached to their moveable supports with the bearing housings and then the unit rotated to its normal orientation of jaws up, baseplate

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down. The housings were tack welded in place. The rotation drives and pawls were remounted. The RF foils and thermistor holders with thermistors were attached and functioning verified. The first rotation test with tube twist was performed; alignment was excellent before and after; gear functioning was flawless. Resistance measurements were as before. Then the molybdenum rotation housing was tack welded via steel support wire to prevent any future movement and its mounting screws welded to each other with a thin steel plate. The actuator claw was tack welded to its support post. A second pair of rotation tests were performed successfully and the decision to place the unit inside its vacuum vessel was made.

o Welded the vacuum tank to the baseplate and leak checked, sealing the cooling tube penetrations with 4 cylinder-covers equipped with O-rings. Leak rates of 1e-10 mbar-l/sec were achieved. The rest of the period was spent arranging for someone to do the copper tube-copper feedthrough TIG brazes.

o Other LARP efforts: A wide-band feedback system is proposed to stabilize intra-bunch instabilities driven by electron-clouds or transverse mode coupling (TMCI) in the CERN SPS. In support of this project, SLAC has started to work on incorporating into the C-MAD code a detailed and realistic model of the intra-bunch feedback system to analyze its impact on the beam emittance and stability. The objective is to simulate the feedback control by using 16 samples per bunch to process the feedback algorithm, which is equivalent to a 2.6 Giga-Samples/sec sampling frequency in the ADC/DACs and processing channel, which is at the limit of the available technology. With a realistic model of the hardware, it will be possible to design a feedback system suitable for suppressing electron cloud and TMCI.

A grooved insert has been installed into in a dedicated test area of the CERN SPS beam line. We received the preliminary results of short tests made in March. The measured electron cloud current signal for the grooved insert was a factor of 2 to 15 lower, depending on the beam parameters, than a reference smooth metallic surface of the same material.

SuperB: No further work was done on the Super-B project pending direction from the DOE.

End Station A: We (Mauro Pivi and the Test Facilities Department) are working on re-establishing the End Station A Test Beam (ESTB) at SLAC. A small fraction of the 13.6 GeV electron bunches from the Linac Coherent Light Source (LCLS) will provide test beam capabilities in the large End Station A (ESA) experimental hall for accelerator instrumentation tests, accelerator R&D, particle and particle astrophysics detector research, linear collider machine and detector interface studies, radiation-hard detector development and material damage studies.

Currently the plan includes the installation of one kicker magnet with a stainless steel chamber in the Beam Switch Yard during Spring 2011. This will allow early commissioning of the kicker system with the bunches deflected into a beam line upstream of End Station A. As soon as a new Personal Protection System for ESA is completed later this summer, and a new beam dump is installed in ESA, a low energy beam will be run into ESA to start commissioning of the complete test beamline. In late October, we will install four new kicker magnets with ceramics chambers (to reduce eddy currents) in the Beam Switch Yard and start operating the ESTB at higher beam energy in November.

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In March, we hosted the first ESTB Workshop, which attracted 50 attendees from 16 outside institutions, underlining the broad interest by the community for a beam test facility. Ahead of the workshop, we received eight proposals with requests for beam time.

Publications

o M.A. Kemp, A. Benwell, C. Burkhart, R. Larsen, D. MacNair, M. Nguyen, J. Olsen, “Design of the second-generation ILC Marx modulator,” LINAC10.

o M.A. Kemp, A. Benwell, C. Burkhart, J. Hugyik, R. Larsen, K. Macken, D. MacNair, M. Nguyen, J. Olsen, “The ILC P2 Marx and application of the Marx topology to future accelerators,” PAC11.

o David MacNair, Mark A. Kemp, Koen Macken, Minh N. Nguyen, Jeff Olsen, “SLAC P2 Marx control system and regulation scheme,” PAC11.

o K.J.P. Macken, D. MacNair, M.N. Nguyen, J. Hugyik, J. Olsen, and M. Kemp, “IGBT PEBB technology for future high energy physics machine operation applications,” APEC2011.

o Faya Wang, “Design and Optimization of Future X-Ray FELS Based on Advanced High Frequency Linacs,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o Novokhatski et al., “SuperB: Next-Generation e+e- B-factory Collider,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o S. Novokhatski, “Wake potentials in the ILC interaction region”, PAC2011, SLAC-PUB-14260

o K.J. Bertsche et al., “Vibration Budget for SuperB,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o Y. Nosochkov et al., “Compensation of Detector Solenoid in SUPER-B,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o Lisa Laurent et al., “Experimental Study of RF Pulsed Heating,” Phys. Rev. ST - Accel. Beams, vol. 14, 041001 (2011), April 2011, 21 pp.

o Faya Wang, Chris Adolphsen, and Christopher Nantista, “Performance Limiting Effects in X-Band Accelerators,” Phys. Rev. ST - Accel. Beams, vol. 14, 010401 (2011), January 2011, 5 pp.

o Faya Wang, Chris Adolphsen, and Christopher Nantista, “Initial High-Power Test Results of an X-Band Dual-Moded Coaxial Cavity,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o M.P. Dunning et al., “Status and Upgrades of the NLCTA for Studies of Advanced Beam Acceleration, Dynamics, and Manipulation,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

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o S.G. Anderson et al., “An Optimized X-band Photoinjector Design for the LLNL MEGa-Ray Project,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o R.A. Marsh et al., “X-Band RF Photoinjector Research and Development at LLNL,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o T.L. Houck et al., “50 MW X-Band RF System for a Photoinjector Test Station at LLNL,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o Z. Li et al., “On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o F.V. Hartemann et al., “Overview of Current Progress on the LLNL Center for Nuclear Photonics and Mono-energetic Gamma-ray Source,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.

o C. Rivetta et al., “Mathematical Models of Feedback Systems for Control of Intra-bunch Instabilities driven by TMCI”, PAC2011

o M. Pivi, C-MAD USER’S MANUAL, SLAC-PUB-14443

o K. G. Sonnad, et al., “Simulations of Electron Cloud Induced Instabilities and Emittance Growth for CESRTA”, PAC2011

o M. Pivi, et al., “ILC Damping Ring Electron Cloud R&D Effort”, ECLOUD10 Workshop

o M. Pivi,K. Sonnad, “Single-Bunch Instability Simulations in CESRTA”, ECLOUD10 Workshop

o K. Sonnad, et al., “An Update on Simulation of Beam Dynamics with Electron Cloud Effects”, ECLOUD10 Workshop

o L. Wang, M. Pivi, “Trapping of Electron Cloud in ILC/CESRTA Quadrupole and Sextupole Magnets”, ECLOUD10 Workshop

o J. Calvi et al., “Electron Cloud Mitigation Investigations at CESR-TA”, ECLOUD10 Workshop

o C. M. Spencer, et al., “A Project to Design and Build the Magnets for a New Test Beamline, the ATF2, at KEK”, IEEE Trans.Appl.Supercond., SLAC-PUB-14339

o Y. Sun, C. Adolphsen, “Linac alignment: 1-to-1 correction”, SLAC-PUB-14322

o Y. Sun, C. Adolphsen, “Emittance growth in the NLCTA first chicane”, SLAC-PUB-14323

o Y. Sun, C. Adolphsen, “A new linac steering algorithm”, SLAC-PUB-14466.

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5. Accelerator Physics & Engineering Department

The mission of the Accelerator Physics & Engineering Department (APE) is to “Make Accelerators Work”. APE works in the gap between what is traditionally considered physics and engineering for the design and operation of existing and near term accelerator facilities. This includes accelerator design and modeling, beam tuning and control, diagnostics, accelerator commissioning and operations. The department core competency is generated by people who combine physics, engineering and accelerator operations expertise.

APE supports a variety of accelerator projects with substantial efforts in:

ATF2: The ATF2 is a test facility designed to demonstrate the linear collider final focus optics using the low emittance beam from the ATF damping ring at KEK in Japan

o The ATF2 non-linear optical system requires the development of new tuning algorithms which are tested on a simulator, then implemented on the accelerator. A new tuning algorithm that does not require an operating spot size monitor was developed and tested in simulation because the laser spot size monitor (developed by Tokyo University) has been unreliable in recent runs.

o The ATF2 uses 37 C-band cavity BPMs with electronics designed by SLAC, cavities constructed by KEK and Pohang and algorithms and software developed at RHUL. The cavity BPM system including the IP BPMs were commissioned this quarter.

o Work at the ATF2 was halted by the disastrous March 11 earthquake which caused some damage to ATF ring and ATF2. This quarter we expect to find out KEK’s plans for ATF2.

o CLIC has become more heavily involved with ATF2 and is doing optics optimization using MADX/MAPCLASS and investigating ultra-low beta* / ultra-high chromaticity optics, and new final focus quads.

CTF3: The CTF3 facility at CERN is designed to demonstrate the high current drive beam generation and two-beam acceleration required for the CLIC collider

o The CLIC drive beam BPM design was completed and prototypes are being fabricated. o The CLIC main beam BPMs conceptual design is underway with possibilities of a common

design with LCLS_II and the Pohang XFEL.o Studies of the transverse and longitudinal wakes of both main beam and drive beam BPMs

were doneo Conceptual design of readout electronics for CLIC beam instrumentation is underway. o Calculation of beam impedances for damping ring, combiner ring, and drive beam turnaround

tapered stripline kickers is underway. o Writing of Conceptual Design Report (CDR) sections on BPMs and beam instrumentation is

underway. o An initial feasibility study is underway for a CLIC quadrupole stabilization demonstration

experiment at JLAB. The CLIC design requires main beam quadrupole magnetic field centers to be stabilized to less than 2nm rms in a bandwidth 2 - 25 Hz. This is considered a “feasibility issue” and performance should be demonstrated.

FACET: FACET is a SLAC project to use the front 2 km of the linac, damping rings and positron system to generate high peak current test beams for plasma wakefield acceleration and other experiments.

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o The preparation of the Sector 0-20 systems, damping rings and FACET experimental area is continuing and is completed in time for the scheduled turn-on.

o FACET feedbacks are under development and expected to be ready to start commissioning for beam turn-on.

o The Pyroelectric detectors for the FACET bunch length monitors have been fabricated and the remainder of the system is expected to be completed next quarter.

o The SAREC committee decided that the FACET THz source required more science motivation. The THz power produced at FACET will be measured, but plans to transport the THz to an experimental area are on hold.

o Beamline models and MAD decks are being updated.

LCLS: The SLAC X-ray FEL system, now providing user beams.

o Due to a calculation error, the X-ray beam divergence from the LCLS is 2x larger than originally estimated and overfills the hard X-ray mirrors. A design was developed to install a Be focusing lens in the X-ray diagnostics chamber (“ST0”). Unfortunately the commercial UHV motion system was delivered very contaminated and could not be installed. We expect to have parts from an alternate vendor installed next quarter.

o The phase cavity timing noise problem that developed last quarter was tracked down to a loose cable in a RF chasis and has been corrected. New phase cavity electronics designed to operate at low charge have been installed and will be ready for operation at the end of the down.

o Short bunch (few-femtosecond) operation of the LCLS based on low charge (20-40pc) and the slotted spoiler is regularly used by experimenters, however the existing diagnostics cannot resolve bunches below 20 femtoseconds. A conceptual and optical design of a single shot broad-band (6-50um) infra-red spectrometer for bunch length measurement was completed. Fabrication of this system has been delayed by parts delivery times, but tests are expected to begin next quarter.

o The slotted-foil ultra-short X-ray pulse generation system is being upgraded with a new high precision foil to allow shorter pulses and more flexibility.

o The thermal-acoustic X-ray energy monitor has passed vacuum testing and will be ready for beam operation after the down.

o The LCLS THz source was used to demonstrate both linear and non-linear autocorrelation scans.

o A THz pump / X-ray probe test is being designed to be installed in the Undulator hall. This will demonstrate the feasibility of this type of experiment before the THz line to the NEH is constructed.

o The Be solid attenuators are being replaced with diamond and Silicon to reduce beam distortions. Some attenuators will be ready at beam turn-on, others are waiting for material delivery.

o The noise performance of the LCLS gas attenuator was found to be partially due to issues with photomultiplier saturation and pulse timing changes with beam energy / gas pressure. The PMTs are being replaced with high-signal tubes and the software is being modified to allow gate timing and PMT high voltage to be automatically adjusted for different operating conditions. A wiring problem on the gas detector solenoids was also found and corrected. This work is expected to be completed next quarter.

o The LCLS orbit response calculation is now able to fit BPM gain and roll angles of BPMs, quadrupoles and corrector magnets. This will allow better characterization of the LCLS optics.

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o A high resolution screen and optics were installed in PR18 in the A-line which allowed few-femtosecond temporal resolution measurements.

o A total of 4 thin Be foils have been damaged in the undulator / beam dump area. APE is investigating alternatives to Be in these applications and has put a hold on installing more Be foils in the vacuum chamber.

o APE has been supporting the LINAC upgrade project to convert the RF system from SLC to EPICS.

o The fast feedback pulse by pulse control system is being used to develop semi-noninvasive pulse-stealing diagnostics.

LCLS_II: The LCLS_II is a project to construct a new XFEL facility at SLAC to provide additional capacity for more simultaneous user experiments.

o The LCLS_II CDR was completed and presentations for the CD-1 review are being finalized.

LHC: Large Hadron Collider at CERN.

o The LHC synchrotron light monitor is used to measure beam profiles and to detect particles in the abort gap. Upgrades to the optical system were installed during the shutdown this winter.

o The forward proton detector system at LHC requires few-picosecond timing stability over several hundred meters. Last quarter a copy of the coax distribution system developed for LCLS demonstrated the required stability (scaled with cable length). Further development is waiting for funding from LHC or LLNL.

o In 2010 the DCCT used to measure average current in the LHC rings showed fill-pattern sensitivity. The modifications implemented during the year-end shutdown, a repartioning of gain and bandwidth profiles and an improvement of RF bypassing, appears to have solved saturation problems. Beam tests this quarter have shown sufficient available headroom to meet LHC needs until the 2013 shutdown. Additional benefits include improved signal monitor bandwidth and improvement in matching of behavior of the devices in the accelerator with the one in the lab. The LHC fast current transformer showed position sensitivity, the cause of which has been identified, and a proposed solution is seen to work in the lab, but has not yet been implemented

NLCTA: Test accelerator using X-band RFo The operation of the NLCTA has been limited by the lack of automated tuning and feedback

systems which has made it difficult to reproduce beam conditions. Scripts and high level applications from LCLS are being adapted for use at NCLTA. These include profile monitor and emittance GUIs and the Schottky scan script.

o NLCTA / ECHO decks and models are being updated to include the new spectrometer and X-band TCAVs

6. Test Facilities

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The mission of the Test Facilities Department (TFD) is to operate and support the test facilities at SLAC that are utilized to develop and test near-term solutions for accelerator issues. RF structures and power sources as well as beam optical, diagnostic and collimation systems are tested in these facilities. The major test facilities are the Next Linear Collider Test Accelerator (NLCTA), Accelerator Structure Test Area (ASTA), and L-band RF test facilities at End Station B. TFD also supports the operation of FACET, End Station A (ESA), and the ATF/ATF2 program at KEK and works closely with the Klystron and the Power Conversion R&D groups.

ASTA report: The ASTA facility includes two s-band 50 MW klystrons who output can be combined, a variable length pulse compressor with an output of up to 500 MW and an extremely flexible RF system that is well suited for fast turnaround of experiments. The ASTA bunker’s shielding is rated for up 100 MeV beam energies. At present is used extensively for testing of all sorts of short RF structures and for testing materials that can be used in RF structure manufacture. With a modest upgrade ASTA can be used to test RF guns. The past quarter activities in ASTA were:

o Operations for the High Gradient structure tests (see also AARD-Microwave report, PETS2 and C10-VG0.7.5).

o Planning for relocation of the cryogenic test stand into the ASTA vault.o Planning for upgrading facility for 24/7 and for remote operations from the NLCTA

control room. 24/7 operation requires design and installation of a fire-suppression system for the modulators. Remote operations require upgrading the ASTA control system to EPICS and upgrading the monitoring systems for remote readout and display. Parts for the remote operation of ASTA have been purchased and are being installed. The fire suppression system is under design review by SLAC.

o A design for a spectrometer magnet can be use to characterize dark current coming out of an RF gun.

o Continuation as last quarter

NLCTA report: The NLCTA facility is housed in End Station B (ESB). At its heart is a former 320 MeV x-band linac (from the NLC project) with an s-band injector and an output beam line and dump. The accelerator components are in their own enclosure inside the ESB hall. The past quarter activities using NLCTA were:

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o Provide beam for E163 and the ECHO experiments (see also AARD-Laser for more E163 information).

o Provide a home for testing x-band RF. (see???)o Continued to rebuild the x-band two-pack for future use in the NLCTA accelerator as

power source for one transverse cavity, and long term testing of XL4 klystron tubes.o Continued upgrading the NLCTA beam line with addition of two transverse cavities for

increasing the beam energy spread and improved slice emittance measurement for the ECHO-7 experiment.

o Refurbished the dump spectrometer to a factor 3 better resolution.o Started to convert the NLCTA control system to EPICS, which will allow a more

homogeneous integration with higher level beam applications provided by the controls department.

o Continued the design of a new x-band test station in the beam dump area. This station will have an x-band gun and some beam acceleration capability.

FACET User Area report: In anticipation of FACET construction completion (see status in ARD Administration section), planning on the experimental user area and the purchase of a trailer for FACET users is proceeding. Detailed installation planning for the user experiments has started.

End Station A: It is planned to have a new electron test beam in ESA (End Station Test Beam, ESTB). Comissioning of the ESTB is expected in Winter of 2011. This test beam will provide the full range of electron energies up to 13.6 GeV, and intensities from single particles to .25 nC/ bunch. It will be used primarily for detector R&D and machine developments. The designs for kicker magnets and ceramic beam pipes to extract and transport beam from the LCLS linac to ESA have been completed and are being fabricated. The implementation of the PPS system for ESA has been started. A one day workshop on March 17, 2011 was met with overwhelming response of 50 participants from 16 institutions. Eight test beam requests were submitted. The first official user run is now scheduled for February 2012.

End Station B: In addition to housing the NLCTA, ESB also supports a range of high power RF source development activities (in collaboration with the Accelerator Design Department and others).

o MARX modulator testing. The failure of the MARX modulator capacitors under full load has led to a study to measure capacitor aging. In the meanwhile the MARX modulator is being run at reduced pulse width but with same power.

o The Cluster-Klystron concept prototype was installed on the NLCTA enclosure roof and tested. Planning for a full scale test (160 meter big pipe) installed in the ESB has started.

o The two-pack system LLRF has been upgraded and modulator mods have been made to facilitate design testing by AED’s Power Conversion Department. A fire suppression system for the two-pack system has been installed.

o TTF3 coupler testing.

o Continuation as last quarter

ECHO Experiment: Echo-7 is a proof-of-principle echo-enabled harmonic generation (EEHG) experiment which is being performed at the NLCTA at SLAC. The experiment aims to test the physics of the EEHG concept and demonstrate scaling. The 3rd, 4th, 5th, 7th, and possibly 15th harmonic of a 1590nm seed laser will be generated through the EEHG scheme. In contrast to other schemes for generating harmonic bunching (e.g. HGHG), higher harmonics can potentially

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be reached with EEHG; in fact, due to the remarkable up-conversion efficiency, soft x-rays may be reached directly from a UV seed laser.

o After a successful summer 2010 run which provided a qualitative confirmation of the ECHO theory, planning for an experiment aimed at making quantitative measurements by summer of 2011 are underway

o Continuation as last quartero For technical improvements: see NLCTA

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