alice energy recovery linac prototype : current status and commissioning successes
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ALICE Energy Recovery Linac Prototype : Current Status and Commissioning Successes. Lee Jones Accelerator Physics Group ASTeC STFC Daresbury Laboratory. ALICE ERL Prototype status update: Content. Introduction Project status Ongoing work - PowerPoint PPT PresentationTRANSCRIPT
ALICE Energy Recovery Linac Prototype:Current Status and
Commissioning Successes
Lee JonesAccelerator Physics Group
ASTeCSTFC Daresbury Laboratory
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
ALICE ERL Prototype: Technical priorities
Primary Goals:
1. Foremost: Demonstrate energy recovery
2. Produce and maintain bright electron bunches from a photoinjector
3. Operate a superconducting Linac
4. Produce short electron bunches from a compressor
Further Development Goals:
1. Demonstrate energy recovery during FEL operation (with an insertion device that significantly disrupts the electron beam)
2. Develop a FEL activity programme which is suitable to investigate the expected synchronisation challenges and demands of 4GLS/NLS
3. Produce simultaneous photon pulses from a laser and an ERL photon source which are synchronised at or below the 1 ps level
ALICE ERL Prototype: Location
Nominal gun energy 350 keV
Injector energy 8.35 MeV
Circulating beam energy 35 MeV Linac RF frequency 1.3
GHz Bunch repetition rate 81.25 MHz Max bunch charge 80 pC Bunch train 100 s Maximum average current 13 µA
ALICE ERL Prototype: Layout
Construction status
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
Drive laser: Summary
Diode-pumped Nd:YVO4
Wavelength: 1064 nm, doubled to 532 nm Pulse repetition rate: 81.25 MHz Pulse duration: 7, 13, 28 ps FWHM Pulse energy: up to 45 nJ (at cathode) Macrobunch duration: 100 s @ 20 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
Electron
s
XHV
CeramicCathode
SF6Vessel removed
Cathode ball
Support Stem
Laser
Anode Plate
• JLab design Cs:GaAs cathode
• 500 kV DC supply
• Single bulk-doped ceramic,
manufactured by WESGO
Power supply commissioned 2005
Ceramic delivery March 2006
Spare ceramic delivered Nov 2006
Gun Assembly
• 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 Better vacuum
• Repeated failure of ceramic,
now using Stanford spare
Gun Commissioning Status
• Beam energy: 350 keV • Bunch charge: > 80 pC • Quantum Efficiency (Q.E.):
3.7% with 1/e lifetime of ~100 hours • Bunch train length: Single 7 ps pulse to 100 µs • Train repetition rate: Operated up to 20 Hz
Design criteria demonstrated so far ……
• 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
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
2006
Cryosystem & 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
ScRF Accelerating modules
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
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
ScRF Accelerating modules
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 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 5 × 109 5 × 109 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 × 109 @ 8.2 MV/m
1.3 × 109 @ 11 MV/m
1.9 × 109 @ 14.8 MV/m
7.0 × 109 @ 9.8 MV/m
Limitation FE Quench FE Quench RF Power FE Quench
Girder
IonPump
Quadrupole Magnet
OTR
Corrector Coil and EBPM Assembly
DipoleMagnet
All modules now installed andunder vacuum. Ready for beam !
Electron beam transport system
• 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
Current / ongoing work
25TW
Lase
r
CBSInteraction
Point
90º focus mirror
180º focus mirror
Pump
Probe
X-rays
THz
IR
Started Dec 2005Laser-SR synergy: Pump-probe expts with table-top laser and SR
X-rays:Time resolved X-ray diffraction
studies probing shock compression of matter on sub-picosecond timescales.
THz:Ultrahigh intensity, broadband
THz radiation to be utilised for the study of live tissues.
ALICE ERLp Photon science: North West Science Fund award of £3m over 3 years
Diagnostics Room
Laser Room
Acce
lera
tor
Hall
2.2 mJ, 35 fsat 1 kHz for EO
800 mJ, 100 fsat 10 Hz for CBS
Courtesy G. Priebe, DL
Courtesy J. Boyce, JLab
Courtesy DLEngineering Office
Compton Back-Scattering X-rays
8 TW in 100 fs pulses @10 Hz
Head-onCollision
Peak Energy ≈ 30 keV
X-ray Flux 15 × 106 phs-1
Pulse Duration
~ Electron Bunch Length
Source Size 50 μm × 20 μm
8 TW in 100 fs pulses @10 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
High Harmonic Generation UV
energy [eV]
Curr
ent
[A]
Courtesy G. Priebe, DL
Longitudinal diagnostics:
probe laser
bunch
to laser diagnostic
encoding(bunch profile into optical pulse)
decoding(optical pulse into profile measurement)
Electro-Optic concept
Courtesy S. Jamison, DL
Encoders
FEL Tunability by varying:• electron energy (24-35 MeV range)• undulator gap (12-20 mm range)
= 4 - 12 m
JLabWiggler
(on loan)
Tunable Free-Electron Laser
The EMMA ProjectEMMAEMMA
BASROC :
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 70-100 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
British Accelerator Science and Radiation Oncology Consortium
Awarded
£6.9m over 3½ years
to design and build
EMMAEMMAEMMA
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 16.519 m
Height from ground
1.4 m
Repetition rate 1 Hz
Orbit swing 3 cm
EMMAEMMA
ALICE Gun diagnostic beamline
BUNCHERC
DE
A
BSOLENOID 1 SOLENOID 2
LASERTRANSVERSEKICKER
DIPOLE
FARADAYCUPS
• 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
RMS geometric emittance as a function of bunch charge:
- Horizontal ( )
- Vertical ( )
ALICE ERLp target was specified as 1· mm-mrad by ASTRA for Q = 80 pC
Some factors are missing from the ASTRA model 1,2
0
1
2
3
4
5
0 10 20 30 40 50 60 70 80
GE
OM
ET
RIC
EM
ITT
AN
CE
(R
MS
),
mm
-mra
d
BUNCH CHARGE, pC
1 I.V. Bazarov et al., Proceedings of PAC’07, Albuquerque, 2007, pp. 1221-1223. 2 F. Zhou et al., Phys. Rev. ST - AB 5, 094203, 2003.
RMS Geometric emittance (function of bunch charge)
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80
dZdZ-fitdZ-ASTRAMappingZero-cross
BU
NC
H L
EN
GT
H @
0.1
, m
m
BUNCH CHARGE, pC
28ps
125ps
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.
Bunch length (function of bunch charge, at 10% level)
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80
EN
ER
GY
SP
RE
AD
@ 0
.1 ,
keV
BUNCH CHARGE, pC
TOTAL
COMPENSATED
MODEL
MODEL
Total and tilt-compensated energy spread
0
5
10
15
20
300 320 340 360 380 400
SQRT (XY)FWHM (Astra)
SQ
RT
(X
Y),
mm
B1, G
SOL-01 scanBeam size (FWHM) on YAG "A"Q = 54pC (#712)
Comparison of predicted and measured beam sizes [mm]as a function of solenoid field strength [guass] for Q = 54 pC
0
1
2
3
4
5
6
7
200 220 240 260 280 300 320
SQRT (XY)FWHM (Astra)
SQ
RT
(X
Y),
mm
B2, G
SOL-02 scanBeam size (FWHM) on YAG "B"Q = 54pC (#712) B1 = -348G
FWHM Beam size for Q = 54 pC
First solenoid Second solenoid
B1 , G B2 , G
Experiment ASTRA model
28 ps 7 ps flattop
twopulse
single
ex, mm 1.95 1.91 0.56 0.80 0.49
ey, mm 1.43 1.47 0.56 0.80 0.49
z, mm 19.1 18.6 23.8 23.5 25.5
Etot, keV 24.4 29.7 22.5 23 28
Ecomp,
keV5.1 2.8 6.0 7.2 1.3
Etot/z,
keV/mm1.28 1.60 0.95 0.98 1.10
-20
-15
-10
-5
0
5
10
15
-10 -5 0 5 10
two-pulsesingle-pulseflat-top
EN
ER
GY
(ke
V/c
)
z, mm
"TWO-PULSE"
"SINGLE PULSE"
"FLAT TOP"
PI Gun driven by differing laser pulse durations
ASTRA Longitudinal phase space predictions
Experiment ASTRA model
28 ps 7 ps flattop
twopulse
single
ex, mm 1.95 1.91 0.56 0.80 0.49
ey, mm 1.43 1.47 0.56 0.80 0.49
z, mm 19.1 18.6 23.8 23.5 25.5
Etot, keV 24.4 29.7 22.5 23 28
Ecomp,
keV5.1 2.8 6.0 7.2 1.3
Etot/z,
keV/mm1.28 1.60 0.95 0.98 1.10
PI Gun driven by differing laser pulse durations
Longitudinal drive laser profile
Experiment ASTRA model
28 ps 7 ps flattop
twopulse
single
ex, mm 1.95 1.91 0.56 0.80 0.49
ey, mm 1.43 1.47 0.56 0.80 0.49
z, mm 19.1 18.6 23.8 23.5 25.5
Etot, keV 24.4 29.7 22.5 23 28
Ecomp,
keV5.1 2.8 6.0 7.2 1.3
Etot/z,
keV/mm1.28 1.60 0.95 0.98 1.10
PI Gun driven by differing laser pulse durations
0
0.2
0.4
0.6
0.8
1
1.2
-20 -10 0 10 20
28ps7ps
z, mm
INT
EN
SIT
Y,
a.u.
28ps
7ps
Experiment ASTRA model
28 ps 7 ps flattop
twopulse
single
ex, mm 1.95 1.91 0.56 0.80 0.49
ey, mm 1.43 1.47 0.56 0.80 0.49
z, mm 19.1 18.6 23.8 23.5 25.5
Etot, keV 24.4 29.7 22.5 23 28
Ecomp,
keV5.1 2.8 6.0 7.2 1.3
Etot/z,
keV/mm1.28 1.60 0.95 0.98 1.10
PI Gun driven by differing laser pulse durations
0
10
20
30
40
50
60
70
80
-20 -15 -10 -5 0 5 10 15 20
28ps (395)28ps(401)28ps(405)
INT
EN
SIT
Y,
a.u.
ENERGY, keV
28ps
0
10
20
30
40
50
60
70
80
-20 -15 -10 -5 0 5 10 15 20
7ps (393)7ps (398)7ps (403)7ps (408)
INT
EN
SIT
Y,
a.u.
ENERGY, keV
7ps
Experiment ASTRA model
28 ps 7 ps flattop
twopulse
single
ex, mm 1.95 1.91 0.56 0.80 0.49
ey, mm 1.43 1.47 0.56 0.80 0.49
z, mm 19.1 18.6 23.8 23.5 25.5
Etot, keV 24.4 29.7 22.5 23 28
Ecomp,
keV5.1 2.8 6.0 7.2 1.3
Etot/z,
keV/mm1.28 1.60 0.95 0.98 1.10
PI Gun driven by differing laser pulse durations
0
0.2
0.4
0.6
0.8
1
1.2
-4 -3 -2 -1 0 1 2 3 4
28ps Pb=525W7ps Pb=960W
ENERGY, keV
INT
EN
SIT
Y,
a.u.
28ps
7ps
Conclusion: Longer laser pulses do not confer significant benefits below ~ 20 pC when compared to short pulses in terms of bunch length & energy spectra.
Immediate: 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
Immediate / future plans
Thank you for listening ……
Acknowledgements:
K.J. MiddlemanY.M. SavelievD.J. HolderS.P. JamisonS.L. Smith
B.L. MilitsynB.D. MuratoriG. PriebeN.R. ThompsonJ.W. McKenzie
Questions ?
EPAC ’08 Proceedings:
Y.M. Saveliev et al., Results from ALICE (ERLP) DC photoinjector gun commissioning, MOPC062, pages 208-210
Y.M. Saveliev et al., Characterisation of electron bunches from ALICE (ERLP) DC photoinjector gun at two different laser pulse lengths, MOPC063, pages 211-213
Linac ’08 proceedings:
D.J. Holder on behalf of the ALICE team, First results from the ERL prototype (ALICE) at Daresbury