erlp overview hywel owen astec daresbury laboratory
TRANSCRIPT
ERLP Overview
Hywel Owen
ASTeC Daresbury Laboratory
Light Source Hierarchy
First generation - parasitic SR beamlines on high-energy physics accelerators; e.g. the SRF on NINA.
Second generation - dedicated particle accelerators providing synchrotron radiation from bending (dipole) magnets.
Third generation - dedicated particle accelerators providing synchrotron radiation from special magnets (insertion devices) placed between the dipole magnets.
Fourth generation - FEL-based (could be linac, storage ring)
The Solution - a Linac-Based Light Source
Linac can deliver a very high quality electron beam (now) Electrons are required only once then dumped. Temporal pulse pattern flexibility.
Features: High average brightness gun. Normal or superconducting linear accelerator. One or more FELs. Energy Recovery required for economy
(55 MW power in 4GLS CW branch).
ERLP - A Prototype Accelerator for 4GLS
EMMAFor more information, and Conceptual Report,See www.4gls.ac.uk
electrons
electrons
anode
ERLP DC Electron Gun
Electrons
XHV
CeramicCathode SF6Vessel removed
Cathode ball
Stem
laser
Anode Plate
• Text
Glassman PK500N008GD5
Voltage -500 kV
Current 8 mA
Cockcroft-Walton based multiplier
Delivered December 2003
Gun Power Supply
Superconducting Modules
Delivery April/July 2006
JLab HOM coupler design adopted for the LINAC module
2 x Stanford/Rossendorf cryomodules – 1 Booster and 1 Main LINAC.
Booster module: 4 MV/m gradient 32 kW RF power
Main LINAC module: 14 MV/m gradient 16 kW RF power
ERLP Cavity Test Results
Booster Cavity1 Linac Cavity1
Booster Cavity2 Linac Cavity2
Specification of > 15MV/m at Qo > 5 x 109
Goal Goal
Goal
Goal
ERLP as an Injector for EMMA
2 x 1.3 GHz Superconducting Modules
ERLP Parameters
Parameter Value
Nominal Gun Energy 350 keV
Max. Booster Volts 8 MV
TL 2 Energy 8.33 MeV
Max. Linac Volts 26.67 MV
Max. Energy 35 MeV
Linac RF Frequency 1.300 GHz (+/- 1 MHz)
Bunch Repetition Rate 81.25 MHz
Bunch Spacing 12.3 ns
Max Bunch Charge 80 pC (risk variable)
Particles per Bunch 5 x 108
Bunches per
Extraction Energy 10 to 20 MeV (need to check lower limit)
Extraction Emittance 5-20 mm mrad (various issues)
ERLP Operating as an Injector for EMMA
8.00 MV (2x4 MV)(standard)
8.35 MeV(standard)
0.35 MeV(fixed)
10-20 MeV(variable)
1.65-11.65 MV(variable)
Later we will need to consider adapted injector (post-4GLS construction)
Bunch Shapes in ERLP (B.Muratori presentation)
Sextupoles also needed in return arc Optimise energy spread after deceleration Allow clean extraction of beam to dump
ERLP Laser Paths – Injector, FEL, THz, EO
ERLP Photoinjector and Laser
LASER ROOM
ACCELERATORHALL
Shield wall
Optical Table
DC GunBased on
Jlab design
Commercial 500kV(350kV)8mA DC Power Supply(Glassman Europe)Power supply and gun enveloped by 0.8 Bar SF6 environment
Booster Cavity
Laser Beam Transport System
ERLP Laser Pulse Output Characteristics
Cathode material Cs:GaAs
Electron bunch charge 80 pC
Bunch length 20 ps
Bunch repetition rate 81.25 MHz
Pulse train length 1 bunch and 20-100 s
Pulse train repetition rate Single shot and 1-20 Hz
Cathode efficiency 1 %
Laser wavelength 532 nm
Laser pulse energy at cathode 20 nJ
Average power at cathode <4 mW
Pulse length <20 ps
Beam diameter at cathode 2-6 mm (FWHM)
Nd:Vanadate Laser material
- -
- -
81.25 MHz Pulse repetition rate
- -
Cw mode-locked Pulse train rep. rate
- -
1064 / 532 nm Laser wavelength
61.5 nJ
532nm output energy per pulse
5 W Average power
7 ps Pulse length (FWHM)
0.6 mmBeam diameter output
The commercial solutionRequirements
ERLP Laser
ChopperChopper• To generate 60-140 s long trains of pulses
with 100 Hz repetition rate• To decrease the thermal load on the electro-optic
modulator (Pockels cell)
Mechanical shutterMechanical shutter• To select pulsetrains with 1-20 Hz• To decrease the thermal load on the Pockels cell
PockelsPockels cellcell•To clean up the rising and falling edges•To select down to single pulse
Injection and Extraction Timing Structure
Standard ERLP injector 12.3 ns bunch spacing Up to ~160 pC per bunch Up to 2 bunches Total charge <0.32 nC Spec is 1 bunch, 80 pC
Pulse-stacking (adapted injector) Down to 0.77 ns spacing Up to ~80 pC per bunch Up to 18 bunches Total charge? Costs more!
Revolution time 55 ns (16.5 m)
risetime
falltimeInjection flat-top time
(top is not really flat)
12.3 ns (81.25 MHz)
~15 ns
~20 ns
Revolution time 55 ns (16.5 m)
0.77 ns (1.3 GHz)max. 18 bunches
RF frequency in injector can be changed by ~1 MHz – not enough!
~20 ns
risetime
falltimeInjection flat-top time
~15 ns
~20 ns ~20 ns
Faro Laser Tracker
Repeatability 1m +1 m /m
Accuracy 10 m + 0.8 m /m
Uncertainty ≈ 10 m /m
Portable
Robust
Spatial Analyzer Metrology Software
Error Simulations
Multiple instruments/types
Automation
ERLP and EMMA Survey – see talk by John Strachan
Simulation of reference grid in SA
76 Grid reference points
40 Instrument positions
Each point measured by a minimum of 3 instrument locations
Faro Tracker
Grid reference points
ERLP Hall Survey and Alignment
Installation Progress
Photoinjector laser operating since April ’06 Gun installed with a dedicated gun diagnostic beamline Both superconducting modules delivered from Accel Cryosystem installed and used to cool accelerating modules down to 2K All beam transport modules now installed – one area under vacuum Most hardware components now installed
Performance Achieved So Far
Gun operating voltage 350 kV (spec value)
Output bunch charge 5 pC (target 80 pC)
Cathode quantum efficiency In gun: 0.4% In the lab: 3.5% (spec is ~few percent)
Bunch train length 100 µs (spec value)
Train repetition rate 20 Hz (spec value)
Parameter Value Nominal Gun Energy 350 keV Max. Booster Volts 8 MV TL 2 Energy 8.33 MeV Max. Linac Volts 26.67 MV Max. Energy 35 MeV Linac RF Frequency 1.300 GHz Bunch Repetition Rate 81.25 MHz Bunch Spacing 12.3 ns Max Bunch Charge 80 pC Particles per Bunch 5 x 10^8 Bunches per Extraction Energy 10 to 20 MeV Extraction Emittance 5-20 mm
mrad
350 keVTest line screen
Ongoing Work
Cleaning and re-assembly of the gun Understanding and testing the cryogenic system Installation and testing of all RF systems Commissioning of the booster and linac modules BTS Installation/Commissioning Laser room modification to accept the terawatt laser
2007 Schedule
Gun & diag line studies finished 3rd April Re-configure booster 16th April Full BTS Pumpdown 25th April RF Systems ready 25th May Beam through Module 1 (8.35 MeV) June Beam through Module 2 (35 MeV) June onwards Energy recovery demonstrated October
Install wiggler Energy recovery from FEL-disrupted beam Produce output from the FEL