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