ERLP / ALICE: a bit of history

Yuri Saveliev

... how all this started

SRS

DIAMOND

ERLP

4GLS

... to greener pastures

.... Oh yes !We get there ...

.... Hmmmm Not quite ....

ERLP: test bed and a learning tool

New accelerator technologies for the UK

First SCRF linac operating in the UK

First DC photoinjector gun in the UK

First ERL in Europe

First IR-FEL driven by energy recovery accelerator in Europe

... lots of help from all around the world

... BIG THANKS to all and , especially, to colleagues from JLab !!

The ALICE (ERLP) Facility @ Daresbury Laboratory

Tower or lab picture

EMMA

superconducting linac DC gun

photoinjectorlaserFree Electron

Laser

superconductingbooster

The ALICE Facility @ Daresbury Laboratory

Accelerators and Lasers In Combined Experiments

An accelerator R&D facility based on a superconducting energy recovery linac

ALICE Machine Description

DC Gun + Photo Injector Laser230 kV GaAs cathode Up to 100 pC bunch charge Up to 81.25 MHz rep rate

RF SystemSuperconducting booster + linac9-cell cavities. 1.3 GHz, ~10 MV/m. Pulsed up to 10 Hz, 100 μS bunch trains

Beam transport system. Triple bend achromatic arcs. First arc isochronousBunch compression chicane R56 = 28 cm

Diagnostics

YAG/OTR screens + stripline BPMs

Electro-optic bunch profile monitor

UndulatorOscillator type FEL.Variable gap

TW laserFor Compton Backscatteringand EO~70 fS duration, 10 HzTi Sapphire

ERLP : infancy • 2003

- Project conceived and funded- calls for tenders; placing orders started

• 2004 - PI laser system (commissioning at RAL)- machine specification completed - magnets, IOTs, gun, SF6 vessels, DC HV ...

• 2005- Gun HV PS assembled- ... problems

(gun ceramic, buncher etc) - NWSF project starts

(TW laser and CBS project)

2006: Gun commissioning & first beam- conditioning resistor failure- gun instability in 260-310kV range of voltages- low and rapidly deteriorating QE (~0.5% max and ~0.1% most of the time)- gun vacuum/current leakage problems after one of the cathode activations

FIRST BEAM

... and 2K cryogenic system commissioned !

2007: fighting gun problems - strong field emission from the new cathode- rapidly deteriorating QE (from initially >1%)- highly non-uniform QE map (due to wafer heating problems)- mechanical failure inside the cathode ball (flap)

New cathode installed- rapid QE deterioration - strong gun contamination after each cathode activation- gun disassembled for wafer change then ...

vacuum leak discovered

Cat

hode

Ano

de

GateValve

Ligh

t Box

BPM-01

SOL-01VCOR-01HCOR-01

Buncher

A BFC 1

Tran

sver

seK

icke

r

C

DE

FC 2Dimensions: Survey data (A0-183-11686 dated 14/07/06)

ERLP Injector test beamline v2.5 (29/08/2006)

SOL-02VCOR-02HCOR-02

VCOR-06HCOR-06 YAG-01

3030

50

HSLT-01 VSLT-01

50

-22 200

-59 500

30-16 500

-54 060

-55 400

-18 500

-60 260

-22 700

ANMAG-01

YAG-02

YAG-03 YAG-04

"a"

Sections schematics when looking downstream (i.e. from the gun)

Eventually (end of 2007) :• The beam from PI gun fully characterised at 350keV • > 100pC achieved (QE>3%)

Meanwhile ... ERLP continues to take its shape

2008: Energy recovery !• Booster cryo modules repair at ACCEL (January-March)• Stanford ceramic installed in the PI gun (June) 230kV only • First beam through the booster (October) • First beam through the linac (December) • ... And finally

... Just before Christmas Full energy recovery

(20.8MeV; at a few pC of bunch charge only)

2009: continuous improvements Starting conditions:

• strong beam loading limitations in SC linacs and strong field emission in main linac ~20pC and ~20MeV

• pitiful photoelectron cathode lifetime (20pC was a blessing rather than norm )

• strong field emitters on cathode and cathode ball (hence 200kV only)

Progress:

• full cathode re-activation and elimination of a minute vacuum leak QE ~ 4% ; >80pC ; long lifetime

• Kr based “plasma cleaning” of the gun removed the most annoying FE on cathode ball

• LLRF optimisation to alleviate beam loading 40pC; 81MHz; 100us

• RF cavities conditioning and RF pulse optimisation operation at up to 30MeV possible !

2009: further milestones : THz

Coherently enhanced broadband THz radiation generated (Feb)

-0.5

0

0.5

1

1.5

2

2.5

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3.5

0 2 4 6 8 10

#1016

THz, V

TH

z, V

Q, pC

Compton backscattering demonstrated on ALICE: November 2009

... Just two days before the start of the shutdown !!!

Electron beam

Laser beam

X-rays

Camera:Pixelfly QE

ScintillatorBe window

Interaction region

2009: further milestones : CBS exp.

2010: “accelerating”

He processing by ASTeC RF + cryogenic groups with assistance from T. Powers (Jlab)

0

100

200

300

400

500

600

700

800

4 5 6 7 8 9 10 11 12

RA

DIA

TIO

N,

uSv/

h

ACCELERATING GRADIENT, MV/m

• Helium processing of linac cavities(March)

• PI laser burst generator allows < 81MHz operation enables Q=60pC as standard

• THz cells exposures started in April

(in an incubator located in the accelerator hall)

• EMMA ring completed and commissioned ... many-many turns (August)

• IR FEL : first lasing !! (October)

23rd October 2010: ALICE FEL First Lasing

First Lasing Data: 23/10/10

-5 0 5 10 15 20 250

2

4

6

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10

12

14

Cavity Length Detuning (m)

Out

coup

led

Ave

rage

Po

wer

(m

W)

Lasing 100-40 pC @ 16.25 MHz

5 5.5 6 6.5 7 7.5 8 8.50

0.2

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0.8

1

P(

)(a

.u.)

(m)

g = 16 mmg = 15 mmg = 14 mmg = 13 mmg = 12 mm

Continuous tuning 5.7-8.0 µm, varying undulator gap.

The peak power ~3 MW

Single pass gain ~20 %

2011: EMMA • First extraction of beam from the ring (March)• First acceleration in EMMA (March) • Acceleration by EMMA : 12 21MeV (April) • Proof-of-principle demonstrated • Paper to Nature Physics submitted (and accepted ?) • ... to be continued

First NS FFAG “EMMA”: Successful International Collaboration

2011: FEL and FELIS

• FEL beam transported to the Diagnostic room (March) • Scanning Near-field Optical Microscope (SNOM) installed

received from Vanderbuilt Uni. • Free Electron Laser integration with

Scanning Near-field Optical Microscope FELIS • First SNOM image (September) • Short e-bunch characterisation with EO diagnostic

Electro-optic bunch profile measurement (ZnTe crystal probed by Ti Sapphire laser)

2011: THz for biology

• THz beam transported to the TCL (Tissue Culture Lab) that’s ~ 30m away from chicane

• Biological experiments in TCL started (June)

Research program to determine safe limits of exposure of human cells to THz and effect of THz on differentiation of stem cells

Estimate > 10 KW in single THz pulse with ~ 20% transport efficiency to TCL

ALICE : a source of high power broadband coherently enhanced THz radiation

2011: Other developments • Quantum dots studies for novel solar cells (with Manchester Uni.) - employs high power THz from ALICE

• Timing and synchronisation experiments - fibre-ring-laser-based system; - aims for sub-10fs timing distribution for future light sources • Digital LLRF development • Experiments on interaction of short electron bunches with high power

electromagnetic radiation • Photocathode research

• DICC: International collaboration on SC cryomodule development

sample

fs UV pulse

ALICE Milestones: still growing .... exponentially