1. Lee Jones Accelerator Physics Group ASTeC STFC Daresbury Laboratory
ALICE Energy Recovery Linac Prototype: Current Status and Commissioning Successes
Lee Jones
Accelerator Physics Group
ASTeC
STFC Daresbury Laboratory

2. ALICE ERL Prototype status update: Content
Introduction
Project status
Ongoing work
Photon science on the ALICE (formerly known as ERLP)
The EMMA NS-FFAG project
Injector commissioning results
Future plans

3. ALICE ERL Prototype: Technical priorities
Primary Goals:
Foremost: Demonstrate energy recovery
Produce and maintain bright electron bunches from a photoinjector
Operate a superconducting Linac
Produce short electron bunches from a compressor
Further Development Goals:
Demonstrate energy recovery during FEL operation (with an insertion device that significantly disrupts the electron beam)
Develop a FEL activity programme which is suitable to investigate the expected synchronisation challenges and demands of 4GLS/NLS
Produce simultaneous photon pulses from a laser and an ERL photon source which are synchronised at or below the 1 ps level

4. ALICE ERL Prototype: Location

5. ALICE ERL Prototype: Layout
Nominal gun energy 350 keV
Injector energy MeV
Circulating beam energy 35 MeV
Linac RF frequency 1.3 GHz
Bunch repetition rate MHz
Max bunch charge 80 pC
Bunch train 100 ms
Maximum average current 13 µA
All the components of an advance energy recovery machine
High brightness photoinjector
Super-conducting cavities
TBA arc
Magnetic chicane for bunch compression
FEL
Return arc Recovery and Dump

6. Construction status

7. Construction status
Photoinjector laser system operating since April 2006
Gun installed and commissioned into a dedicated diagnostic beamline over a period of several months during three commissioning phases
Accel superconducting modules undergoing commissioning
Cryogenic system installed by Linde and DeMaco, and used to cool accelerating modules down to 1.8 K
All of the electron beam transport system has been installed and is under vacuum
Installation work proceeding for various photon beam transport systems

8. Drive laser: Summary Diode-pumped Nd:YVO4
Wavelength: 1064 nm, doubled to 532 nm
Pulse repetition rate: MHz
Pulse duration: 7, 13, 28 ps FWHM
Pulse energy: up to 45 nJ (at cathode)
Macrobunch duration: Hz
Duty cycle: 0.2% (maximum)
Timing jitter: < 1 ps (specified) < 650 fs (measured)
Spatial profile: Circular top-hat on photocathode
Laser system commissioned at Rutherford Lab in 2005, then moved to Daresbury in 2006
L.B. Jones, Status of the ERLP Photoinjector driver laser, ERL ’07 proceedings

9. Gun Assembly JLab design Cs:GaAs cathode 500 kV DC supply Cathode ball
Single bulk-doped ceramic, manufactured by WESGO
Cathode ball
Cathode
Ceramic
SF6
Vessel removed
Electrons
Laser
XHV
Support Stem
Power supply commissioned 2005
Ceramic delivery March 2006
Spare ceramic delivered Nov 2006
Anode Plate

10. Gun Commissioning Status
Electron gun operated Jul-Aug ‘06, Jan-Apr ‘07 & Oct-Nov ‘07
Problems experienced with cathode activation. Q.E. poor
First beam from the gun recorded at 01:08 on Wednesday 16th August 2006, with the gun operating at 250 kV
Operating at 350 kV soon afterwards
Routinely conditioning gun to 450 kV
Steady improvement in both Q.E. & lifetime
Problems encountered with beam halo, field emission and high voltage breakdown
Improved bakeout º Better vacuum
Repeated failure of ceramic, now using Stanford spare

11. Design criteria demonstrated so far ……
Beam energy: 350 keV ü
Bunch charge: > 80 pC ü
Quantum Efficiency (Q.E.): % with 1/e lifetime of ~100 hours ü
Bunch train length: Single 7 ps pulse to 100 µs ü
Train repetition rate: Operated up to 20 Hz ü

12. Cryosystem & accelerating modules
2006
Apr – 1st Accelerating module delivered
May - 4 K cryo commissioning carried out
Jul – 2nd Accelerating module delivered
Oct - Linac cooled to 2 K
Nov – Booster cooled to 2 K
Dec - Modules cooled together
Simulated a dynamic resistive heat load of ~ 112 W in both modules
Achieved a pressure stability of ± 0.03 mbar at full (simulated) dynamic load in both of the modules at 2 K
Achieved ± 0.10 mbar at 1.8 K

13. ScRF Accelerating modules
2 × Stanford/Rossendorf cryomodules, one configured as the Booster and the other as the Main Linac, also using the JLab HOM coupler
2 × 9 - Cell 1.3 GHz cavities per module
Booster module:
4 MV/m gradient
52 kW RF power
Main Linac module:
13.5 MV/m gradient
16 kW RF power
Quality factor, Q0 ~ 5 × 109
Total cryogenic load:
~ 180 W at 2 K

14. ScRF Accelerating modules
2 × Stanford/Rossendorf cryomodules, one configured as the Booster and the other as the Main Linac, also using the JLab HOM coupler
2 × 9 - Cell 1.3 GHz cavities per module
Booster module:
4 MV/m gradient
52 kW RF power
Main Linac module:
13.5 MV/m gradient
16 kW RF power
Quality factor, Q0 ~ 5 × 109
Total cryogenic load:
~ 180 W at 2 K
Booster
Linac
Cavity 1
Cavity 2
Vertical tests at DESY, July - December 2005
Eacc (MV/m)
18.9
20.8
17.1
20.4 Qo
5 × 109
Acceptance tests at Daresbury Laboratory, May - September 2007
Max Eacc (MV/m)
10.8
13.5
16.4
12.8
Measured Qo
3.5 ×
8.2 MV/m
1.3 ×
11 MV/m
1.9 ×
14.8 MV/m
7.0 ×
9.8 MV/m
Limitation
FE Quench
RF Power

15. Electron beam transport system
Dipole Magnet
Quadrupole Magnet
OTR
Girder
All modules now installed and under vacuum. Ready for beam !
Corrector Coil and EBPM Assembly
Ion Pump

16. Current / ongoing work
Preparing for 4th phase of gun commissioning
1st phase of beam comissioning
RF Conditioning of accelerating modules
Optimising of the cryogenic system with RF present
Commissioning of high-power RF & PLC control systems
Commissioning of electron BTS sub-systems:
Controls / Diagnostics
Beam Loss Monitor
Machine Protection System
Installation of the photon BTS for THz, FEL, EO & CBS

17. ALICE ERLp Photon science:
North West Science Fund award of £3m over 3 years
ALICE ERLp Photon science:
X-rays:
Time resolved X-ray diffraction studies probing shock compression of matter on sub-picosecond timescales.
90º focus mirror
X-rays
Probe
Pump IR
180º focus mirror
CBS Interaction Point
THz
THz:
Ultrahigh intensity, broadband THz radiation to be utilised for the study of live tissues.
25TW Laser
Started Dec 2005
Laser-SR synergy:
Pump-probe expts with table-top laser and SR

18. Accelerator Hall Laser Room Diagnostics Room 2.2 mJ, 35 fs
at 1 kHz for EO
800 mJ, 100 fs
at 10 Hz for CBS
Diagnostics Room
Courtesy G. Priebe, DL

19. Compton Back-Scattering Þ X-rays
8 TW in 100 fs Hz
Side-on Collision
Peak Energy
≈ 15 keV
X-ray Flux
8 × 106 phs-1
Pulse Duration
~ Laser Pulse Length
Source Size
10 μm × 20 μm
8 TW in 100 fs Hz
Head-on Collision
Peak Energy
≈ 30 keV
X-ray Flux
15 × 106 phs-1
Pulse Duration
~ Electron Bunch Length
Source Size
50 μm × 20 μm
Courtesy J. Boyce, JLab
Courtesy DL
Engineering Office

20. High Harmonic Generation Þ UV
Courtesy G. Priebe, DL
Current [A]
energy [eV]

21. Longitudinal diagnostics:
Electro-Optic concept
Longitudinal diagnostics:
encoding
(bunch profile into optical pulse)
probe laser
bunch
to laser diagnostic
decoding (optical pulse into profile measurement)
Courtesy S. Jamison, DL

22. Tunable Free-Electron Laser
Encoders
JLab Wiggler
(on loan)
FEL Tunability by varying:
electron energy (24-35 MeV range)
undulator gap (12-20 mm range)
l = mm

23. The EMMA Project
EMMA

24. Awarded £6.9m over 3½ years to design and build EMMA
BASROC :
British Accelerator Science and Radiation Oncology Consortium
EMMA
The long-term aim of BASROC is to build a complete hadron therapy facility using Non-Scaling Fixed-Field Alternating Gradient accelerator technology (NS-FFAG), combining the best features of cyclotron and synchrotron accelerators
An FFAG combines the intensity and ease-of-use of cyclotrons coupled with the benefits of synchrotrons, specifically beam control and the ability to accelerate proton and heavy ion beams to various energies
EMMA: The Electron Model of Many Applications will use ALICE as an injector at 10 MeV, accelerating electrons to 20 MeV. The goal is to learn how to design NS-FFAGs for various applications, including hadron therapy
PAMELA: The Particle Accelerator for MEdicaL Applications will be a MeV proton NS-FFAG, itself a prototype to demonstrate the potential use of NS-FFAGs in hadron therapy, thus strengthening the case for hadron therapy
Leading to a complete facility for the treatment of patients using hadron beams
Awarded £6.9m over 3½ years to design and build EMMA

25. EMMA on the ALICE ERL Parameter Design Value Energy range 10 to 20 MeV
Number of cells 42
Lattice
Doublet
Cell length
393 mm
Circumference m
Height from ground
1.4 m
Repetition rate
1 Hz
Orbit swing
3 cm

26. ALICE Gun diagnostic beamline
transverse RMS emittance measured by double-slit scans at positions ‘A’ and ‘B’
bunch length with slit ‘A’ and kicker cavity
Courtesy Y. Saveliev, DL

27. RMS Geometric emittance (function of bunch charge)
RMS geometric emittance as a function of bunch charge:
- Horizontal ( )
- Vertical ( )
ALICE ERLp target was specified as 1·p mm-mrad by ASTRA for Q = 80 pC
Some factors are missing from the ASTRA model 1,2
1 I.V. Bazarov et al., Proceedings of PAC’07, Albuquerque, 2007, pp
2 F. Zhou et al., Phys. Rev. ST - AB 5, , 2003.

28. Bunch length (function of bunch charge, at 10% level)
Bunch length at 10% of the peak value used due to non-uniformity of the longitudinal profile.
Data were obtained with the RF transverse kicker (full circles), “energy mapping method” (square) and zero-crossing method (triangle).
Open circles are the results from the ASTRA model.

29. Total and tilt-compensated energy spread

30. FWHM Beam size for Q = 54 pC First solenoid Second solenoid
B1 , G
B2 , G
First solenoid
Second solenoid
Comparison of predicted and measured beam sizes [mm] as a function of solenoid field strength [guass] for Q = 54 pC

31. ASTRA Longitudinal phase space predictions
PI Gun driven by differing laser pulse durations
Experiment
ASTRA model
28 ps
7 ps
flat
top
two
pulse
single
ex, mm
1.95
1.91
0.56
0.80
0.49
ey, mm
1.43
1.47
Dz, mm
19.1
18.6
23.8
23.5
25.5
DEtot, keV
24.4
29.7
22.5 23 28
DEcomp, keV
5.1
2.8
6.0
7.2
1.3
DEtot/Dz, keV/mm
1.28
1.60
0.95
0.98
1.10
ASTRA Longitudinal phase space predictions

32. Longitudinal drive laser profile
PI Gun driven by differing laser pulse durations
Experiment
ASTRA model
28 ps
7 ps
flat
top
two
pulse
single
ex, mm
1.95
1.91
0.56
0.80
0.49
ey, mm
1.43
1.47
Dz, mm
19.1
18.6
23.8
23.5
25.5
DEtot, keV
24.4
29.7
22.5 23 28
DEcomp, keV
5.1
2.8
6.0
7.2
1.3
DEtot/Dz, keV/mm
1.28
1.60
0.95
0.98
1.10
Longitudinal drive laser profile

33. PI Gun driven by differing laser pulse durations
Experiment
ASTRA model
28 ps
7 ps
flat
top
two
pulse
single
ex, mm
1.95
1.91
0.56
0.80
0.49
ey, mm
1.43
1.47
Dz, mm
19.1
18.6
23.8
23.5
25.5
DEtot, keV
24.4
29.7
22.5 23 28
DEcomp, keV
5.1
2.8
6.0
7.2
1.3
DEtot/Dz, keV/mm
1.28
1.60
0.95
0.98
1.10

34. PI Gun driven by differing laser pulse durations
Experiment
ASTRA model
28 ps
7 ps
flat
top
two
pulse
single
ex, mm
1.95
1.91
0.56
0.80
0.49
ey, mm
1.43
1.47
Dz, mm
19.1
18.6
23.8
23.5
25.5
DEtot, keV
24.4
29.7
22.5 23 28
DEcomp, keV
5.1
2.8
6.0
7.2
1.3
DEtot/Dz, keV/mm
1.28
1.60
0.95
0.98
1.10

35. PI Gun driven by differing laser pulse durations
Experiment
ASTRA model
28 ps
7 ps
flat
top
two
pulse
single
ex, mm
1.95
1.91
0.56
0.80
0.49
ey, mm
1.43
1.47
Dz, mm
19.1
18.6
23.8
23.5
25.5
DEtot, keV
24.4
29.7
22.5 23 28
DEcomp, keV
5.1
2.8
6.0
7.2
1.3
DEtot/Dz, keV/mm
1.28
1.60
0.95
0.98
1.10
Conclusion: Longer laser pulses do not confer significant benefits below ~ 20 pC when compared to short pulses in terms of bunch length & energy spectra.

36. Immediate / future plans
Beam through the booster, main linac and arcs
Demonstrate energy recovery
Followed by:
Fine tuning of the machine: tune injector for minimum emittance, optimisation of energy recovery at nominal beam parameters, extensive beam measurements
Short pulse commissioning: longitudinal dynamics, EO diagnostics
Energy recovery with FEL and first IR light from the FEL
Simultaneously:
THz & IR-FEL research programmes will start, as will CBS X-ray production using head-on electron-photon collisions
Future:
Load-lock gun upgrade and possible re-design for vertical ceramic
Re-installation of gun diagnostic line
Installation of an improved high-current cryomodule
Current position on all 4GLS related activities 4GLS design ERLP lessons
Have to keep strictly to time as there’s a bottle of alcoholic content resting on it isn’t there Trevor.
Some of the overheads might well appear as subliminal messages…

37. Questions ? Thank you for listening …… Acknowledgements:
EPAC ’08 Proceedings:
Y.M. Saveliev et al., Results from ALICE (ERLP) DC photoinjector gun commissioning, MOPC062, pages
Y.M. Saveliev et al., Characterisation of electron bunches from ALICE (ERLP) DC photoinjector gun at two different laser pulse lengths, MOPC063, pages
Linac ’08 proceedings:
D.J. Holder on behalf of the ALICE team, First results from the ERL prototype (ALICE) at Daresbury
Acknowledgements:
K.J. Middleman Y.M. Saveliev D.J. Holder S.P. Jamison S.L. Smith
B.L. Militsyn B.D. Muratori G. Priebe N.R. Thompson J.W. McKenzie
Questions ?