accelerator research: future directions and opportunities · 2010-08-13 · accelerator research:...

Accelerator Research: FutureDirections and Opportunities

Prof. Tor RaubenheimerStanford University & SLAC National Accelerator Lab

August 9th, 2010

2010 DOE SCGF Research Conference

Outline

• What are accelerators?• What is Accelerator Research?• Main challenges in Accelerator Research• Examples:

– Collimating the LHC beam (Beam power)– Challenges for a Muon Collider (Beam brightness)– Ultra-high gradient R&D (Beam energy)

• Accelerator R&D across the DOE


What are accelerators?

• Wikipedia: A particle accelerator is a device that useselectromagnetic fields to propel charged particles to highspeeds and to contain them in well-defined beams– CRT’s x-ray tubes SRS Large Hadron Collider– Velocity = 0.999999999986 x speed of light at LEP2

• ~26,000 accelerators worldwide– ~44% are for radiotherapy,– ~41% for ion implantation,– ~9% for industrial processing and research,– ~4% for biomedical and other low-energy research,– ~1% with energies > 1 GeV for discovery science and research


Types of High Energy Accelerators

• Colliding beam storage rings:– ISR; SPEAR; PEP/PETRA; TRISTAN; LEP; RHIC; Tevatron; LHC; …

• Linacs– SLAC fixed target; SLC linear collider; ILC/CLIC; …– SNS; TRIUMF; PSI; FAIR; FRIB; ESS; …

• Synchrotron radiation– Large number of facilities

around the world– Storage rings and

linacs

• Web resourceshttp://www.lightsources.org/cms/http://www.interactions.org/cms/


CERN Large Hadron Collider

• 14 TeV p/p collider• 27 km circumference• 8 Tesla SC magnets• >350 MJ stored beam

Fermilab Main Injector and Recycler Ring

• Recycler low costpermanent magnetring for storingbeams beforeinjection to MI

• Main Injectoraccelerates p and pto 120 GeV forinjection to Tevatron

-

Tevatron

SLAC Linac and LCLS

• SLAC 3 km long linacproduced 50 GeV e+ ande- and undulator hall forLCLS x-ray laser

Field of Accelerator Physics

• Broad field ranging fromengineering some of thelargest scientific instrumentsto rf design to materialsphysics to nonlinear dynamics– Advances come from both

fundamental research anddirected R&D aimed atapplications

• Field offers opportunity for‘small-scale’ experiments atlarge science facilities– Small groups:

• Individuals can engage intheory, simulation,and experimental results

LHC

Tevatron

LEP-II

SLCHERA

Primary Challenge for Accelerator R&D

Goal: achieve high energy with high luminosity (interaction flux)

1. Beam power average luminosity or brightness– Power (average current times energy) is frequently measured in

megawatts and has both technical and physical limitations

2. Beam brightness and control peak luminosity andradiation source brightness– Brightness is flux divided by 6-D phase space volume (emittance)

which should be conserved after beam creation

3. Beam energy energy reach or radiation wavelength– Critical problem for HEP requiring new cost-effective concepts– Novel concepts will enable new applications elsewhere as well

• Cost-effective approaches are needed across the field2010 DOE SCGF Research Conference

1. Beam Power Challenges

• Many critical technologies– Targets, collimators and dumps, materials, MPS, SCRF, …

• SCRF highpower proton beams for anumber of new applications:– Neutrino beams– Neutrino factory & Muon Collider– Accelerator Driven Systems

and transmutation of waste

• LHC beams will be ~700 MJ– Beam collimation is difficult!Yi

eld

of IL

C 1

.3 G

Hz

cavi

ties

USS Iowa at30 kn ~ LHCbeams

LHC Collimators

• Three main requirements on beam collimation systems:– Protect accelerator (and themselves) from errant beams– Scrape away beam tails to prevent loses in magnets or detectors– Have minimal effect on beam core (small transverse impedances)

• Understand normal operation losses– Population of beam halos due to nonlinear fields and collective

effects

Expected to be 1st luminositylimitation at LHC

Consumable LHC Collimator Prototype

• Challenges:– Model LHC to understand losses

and collimator impact on beam– Develop mechanical system to

align collimators at micron-level– Understand long-term behavior

of irradiated materials

E field

B field

2. Beam Brightness Challenge

• Beam brightness most tightly tied to ‘beam physics’– Some of the hot topics over the years:

• Rf guns, final focus systems, emittance pres.,electron cloud, emittance exchange, …

• New e- guns 1000x brighter than beststorage/damping rings– Development pushed by FEL community– How can HEP benefit?

• High luminosity 1036 B-factories– Limits of colliding beam physics

• Require very bright beamswith novel collision schemes

• New limits in beam collectiveeffects, control and feedback


Muon Collider

• Muon Collider = LeptonCollider withoutsynchrotron radiation– LEP-II ring was 27 km

Compact (and hopefully)low-cost lepton collider

Main Challenge: Muon Cooling

• Ionization cooling is thecritical technology for muoncollider

– Multiple concepts beingstudied

Stages of Muon cooling

Ionization Cooling

Liquid Hydrogen

• Requires 106 reduction of6-dimensional emittance

6-D Muon Cooling

• Complicated problem involving magnetic transport,interaction with matter and rf fields– Needs to be done quickly to prevent muons from decaying

Helical Cooling Channel

– A number of possible strategiesbeing investigated

– Intermix absorbers, rf andmagnetic fields

– See R. Palmer, AAC’2010

Guggenheim Cooling Channel

RF Breakdown Issues

• Muon Collider needs high accelerating fields to minimizetime muons are at low energy and can decay– Rf gradients of 100 MV/m are possible at ~10 GHz but lower

gradients at lower rf frequencies– Operating gradients further decrease in solenoidal magnetic fields

• Working tounderstandbreakdownphenomena anddevelop solutions

Example of ‘magneticinsulation’

Breakdown effects in Cooling Channel cavities

High Performance ComputingDOE Computing Resources:NERSC at LBNL - Franklin Cray XT4, 38,642

compute cores, 77 TBytes memory,355 Tflops

NCCS at ORNL - Jaguar Cray XT5, 224,256compute cores, 300 TBytes memory,2331 Tflops,600 TBytes disk space

Dark current @ 3 pulse risetimes

Data

-- 10 nsec-- 15 nsec-- 20 nsec

Track3P

Track3P: dark currentsimulations

Dissipation of transversewakefields in dielectricloads: eps=13, tan(d)=0.2

T3P – CLIC PETS Bunch Transit

Breakdown Modeling

• Rf breakdown common problem:– Accelerator designs– Fusion physics– Satellite systems– Industry

• Analytic and simulation modeling compared with experiments

10 m

50 nm

Simulated

Measured

Simple model of breakdown

Measuring Breakdown Limits

• The combination of analytic modeling, simulation andexperiments have made great progress in understanding

Doebert &Adolphsen

Tantawi &Dolgashev

Understanding Accelerator RF Materials


TE01 Mode Pulse Heating Ring

Intergranular fractures 500X

|E| |H|

material sample

axis

RF Cavity for T Studies

Investigating Cu and Cu-alloysMo, Ti, …

High Field Magnets: Superconducting Wire

From Palmer, AAC’2010


Schematic of40 T magnet

3. Beam Energy Challenge• Size of a facility is a large cost driver

1. Recirculating systems, e.g. Muon Collider vs. Linear Collider2. High field magnets 3. High gradient acceleration

• High field magnets– Examples abound: LHC, LEHC, MC

• 20T for LEHC and 50T for MC– Continuous improvement in fields

relies on fundamental research anddirected magnet R&D

LARP Nb3Sn magnet 35T Bitter magnet

High Gradient Acceleration• High gradient acceleration requires high peak power and

structures that can sustain high fields– Beams and lasers can be generated with high peak power– Dielectrics and plasmas can withstand high fields

• Many paths towards high gradient acceleration– RF source driven metallic structures– Beam-driven metallic structures– Laser-driven dielectric structures– Beam-driven dielectric structures– Laser-driven plasmas– Beam-driven plasmas

~100 MV/m

~1 GV/m

~10 GV/m


Dielectric Structures

• Unlike Cu, dielectric structures have higher breakdownlimits approaching 1 GV/m at THz frequencies– Making damage measurements to characterize materials– Structures can be either laser driven or beam driven (wakefield)

• Beam-driven structures– Frequencies are in GHz regime and

dimensions are cm-level– Higher gradients than metallic

structures but more difficult wakes

• Laser-driven structures– Use lasers to excite structures similar to

microwave accelerators but with optical-scale features, i.e. 10,000x smaller sizes


(ANL, UT-A, UCLA)

(SLAC/Stanford, UMD)

SLAC Laser Acceleration Facilities

Cl. 10,000 Laser RoomNew Expt. Chamber

e-

Photonic CrystalAccelerator Structures

RF Photoinjector

Inside the Experimental Hall

Photonic Crystal-BasedDielectric Laser-Driven Accelerators

• High Gradient 0.5 GeV/m (~30 x SLAC)• Unparalleled compactness• Photonic Crystals and fibers• Attosecond pulse generation & diagnosis• Leverages telecomm, laser, andsemiconductor industry R&D advances

NLCTA Facility

E163 Area

Scientific Goal: Investigate physical and technical issues ofScientific Goal: Investigate physical and technical issues oflaser acceleration using dielectric structureslaser acceleration using dielectric structures

Tests of Dielectric PBG Fibers

420 T/m Quads

Fiber Holder

SEM image of HC-1550 fiber

10 µm

Knife Edge Measurement

Extracted RMS spot size: 8µm

e-beam profile imageat PMQ focus

8 x 8 µm RMS

e-beam

Experiment being built and operated bypostdoc and graduate students


Fabrication of 3-D PBG StructureSilicon woodpile structure produced at the

Stanford Nanofabrication Facility (SNF)Detailed Tolerance Studies of CDs

Best achieved:Width Variation:

<40 nm RMS(~ /125)

Layer Thickness:

<65 nm RMS (~ /75)

Layer Alignment:

<65 nm RMS(~ /75)

MeasurementTechniqueGranularity: 7nm

Process Version Rod width base Rod width top Taper Angle Layer Thickness Alignment Offset Period3 389 486 9.89624641 556 142.5 18343 402 507 10.69429961 660 146 18273 486 583 10.01988665 549 161.5 18343 486 583 10.01988665 688 102.5 18083 311 441 9.575247964 516 20133 280 391 11.1759075 658 17213 379 509 11.04285784 5593 348 485 10.49147701 7022 438 556 13.12686302 506 412.5 18442 419 506 9.755861898 681 400 18382 469 525 5.75140209 556 522 18132 450 544 9.595956437 545 516 18572 384 455 7.092112957 643 18702 366 446 6.301068652 580 18322 446 527 5.850496153 5272 464 518 8.7379923241 434 529 10.43182293 542 18181 503 669 15.86761887 516 17891 483 649 15.86761887 5841 480 690 19.90374954 580

average 420.85 529.95 10.55991867 586.7368421 300.375 1835.571std 62.16808709 76.49594072 3.503712238 64.14206637 179.4061135 62.12112version 3 mean 390.4285714 500 10.34633323 598 138.125 1839.5version 3 std 74.27062003 65.09649431 0.57608771 73.11243787 25.14416765 95.24022version 2 mean 429.5 509.625 8.276469191 576.8571429 462.625 1842.333version 2 std 37.27887184 39.6157887 2.542079837 63.49128174 65.34188932 19.84607

Fabricated by graduate students


Injector for Micron-Sized Accelerators


I ~ 11 e- per optical cycle 500 mAB > 1013 A / m2 sr2

Laser-Driven Dielectric Accelerator(Accelerator-on-a-chip)

Fiber coupledinput

=2 m20 J/pulse1 ps laser pulse

Distribution, delay, and mode shaping lines

Leff=2mm

Silicon Chip

4-layer Structure Fabrication(completed at SNF)

~8 cm

Cutaway sketch ofcoupler region

beam beam

Image courtesy of B. Cowan,Tech-X.

input

Inputwaveguide

beam

Image courtesy of C.McGuinness, Stanford.

32 MeV Energy Gain


Plasma Acceleration(Beam-driven or Laser-driven)

• 50 GV/m demonstrated– Potential use for linear

colliders and radiationsources

Simulation of 25GeV PWFA stage

Drive bunch

Witnessbunch

Laserpulse or

HPC 3-D PICSimulations

Beam-Driven Plasma Acceleration at SLACFACET Experimental Facility for Advanced Accelerator R&D

Laser Plasma Acceleration at LBNL

• Presently building 1 PW 1Hz laser system for 10 GeV beam• New BELLA facility to demonstrate scalable technology

World-Wide Interest in Plasma Acc.Plasma Acceleration on the Globe from T. Katsuoleas

Compact Plasma Accelerators

• Plasma accelerators have many potential applications– Experiments at MPQ, Imperial College, Univ. of Edinburgh, JAERI,

… aimed at generating a compact laser plasma-based FEL• Working on beam quality, stability, etc

– Many other labs around the world have similar goals

Laser-driven soft-X-ray undulator sourceFuchs et al, Nature Physics (2009)

Incoherentundulator radiation


Concept of a Plasma Linear Collider

W. Leemans, et al.,Physics Today, March 2009


DOE SC Accelerator R&D(A selection of the programs)

• SLAC (Stanford, …)– Ultra-high gradient acceleration using -wave, lasers & plasmas– Free Electron Lasers inc. high brightness sources, FEL physics,

beam-laser interactions– e+/e- collider science and technology (LC and Super-B)

• Fermilab (U Chicago, IIT, …)– SCRF development; Magnet R&D– Muon collider concepts;– Hadron collider science and technology

• UCLA– High brightness beams and advanced accelerator R&D

• Cornell University– Energy Recovery Linacs (ERLs); SCRF development


DOE SC Accelerator R&D(A selection of the programs)

• LBNL (UCB, …)– Broad program: FELs, Laser-plasma acceleration; heavy ion fusion

• LLNL (UCB, UC Davis, …)– Laser-plasma acceleration and Inverse-Compton Scattering sources

• Argonne (UC, IIT, …)– SCRF development and dielectric wakefield acceleration

• Brookhaven (SUNY Stony Brook, …)– Magnet development; RHIC; SCRF; NSLS-II; FELs

• Jefferson Lab– SCRF development; ERLs; FELs

• Oak Ridge (SNS)– High power beams; SCRF development; Laser stripping


Summary

• Accelerator research:– Broad field ranging from engineering to mathematical physics and

from fundamental science to applied development– Field impacts discovery science programs as well as security,

industry and medicine– Largely ‘small science’ in big science laboratories

• Many exciting research topics– Tied to state-of-the-art accelerators (LHC, LCLS, SNS, NSLS-II, …)– New accelerator designs (FRIB, ILC, Muon Collider, …)– Advanced accelerator concepts (dielectrics, lasers, plasmas, …)– HPC modeling of accelerators and beam dynamics

• More resources:– www.interactions.org www.lightsources.org

– http://www.acceleratorsamerica.org/– http://www.ireap.umd.edu/AAC2010/welcome.htm

accelerator research: future directions and opportunities · 2010-08-13 · accelerator research:...

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