ALICE Accelerators and Lasers in Combined Experiments

1
ALICE Accelerators and Lasers in Combined
Experiments
S.L.Smith and of course the rest of the ALICE
team!
2
Contents

• ALICE introduction
• Photoinjector commissioning
• Result highlights
• Superconducting module status
• Performance
• FE Radiation issues
• ALICE Light Sources
• Commissioning
• Future plans
• Future Accelerator Studies
• Future Photon Science plans
• Summary

3
Alice introduction

• ALICE introduction

4
Introduction

• ERLP (Energy Recovery Linac Prototype) at
  Daresbury Lab, UK
• conceived as a prototype of an energy recovery
  based 4th generation light source
• Beyond 4GLS !
• ALICE (Accelerators and Lasers in Combined
  Experiments)
• An RD facility dedicated to accelerator science
  and technology development
• Offers a unique combination of accelerator, laser
  and free-electron laser sources
• Enables essential studies of beam combination
  techniques
• Provides a suite of photon sources for scientific
  exploitation

• Reviewed Oct 2007
• Best matched ?
• UK requirements
• Funding 2011
• Science 2015

5
Why ERL?

• Advantage of Linac vs Storage Ring
• Non-equilibrium conditions
• Source characteristics determined by injector
• Shorter bunchesgtmore flexible bunch pattern

6
Why ERL?

• Advantage of ERL vs Linacs
• Improvement in efficiency
• Enormous Increase in average current (CW) and FEL
  power
• Reduced dump activation

• Advantage of ERL vs Storage Ring
• Non-equilibrium conditions
• Source characteristics determined by injector
• Shorter bunchesgtmore flexible bunch pattern

7
Accelerator Layout

• Nominal Gun Energy 350 keV
• Injector Energy 8.35 MeV
• Circulating Beam Energy 35 MeV
• RF Frequency 1.3 GHz
• Bunch Repetition Rate 81.25 MHz
• Nominal Bunch Charge 80 pC
• Average Current 6.5 mA
• (Over the 100 ms Bunch Train)

8
ALICE
9
Electron Source
10
Electron Source
LASER
11
ALICE
12
Acceleration
13
Acceleration
14
ALICE
15
Compression
16
Compression
17
ALICE
18
Wiggler/FEL
19
Wiggler/FEL
Encoders
Motor and In Line Gearbox
20
ALICE
21
ALICE Main Parameters
Gun DC Voltage 350kV Nominal bunch
charge 80pC Cathode NEA GaAs Laser
NdYVO4 532nm Laser spot 4.1mm FWHM Laser pulse
length 28ps FWHM Quantum Efficiency
1-3 --------------------------------------------
--------------------------------------- Injector
Energy 8.35MeV Total beam energy 35MeV RF
frequency 1.3GHz Bunch repetition
frequency 81.25MHz Train Length 0-100ms Train
repetition frequency 1-20Hz Compressed bunch
length lt1ps (_at_80pC) Peak current in compressed
bunch 150A Maximum Average Current 13mA Max
current within the train 6.5mA
22
Photoinjector

• Photoinjector

23
Photoinjector Introduction
JLab GA
Gun ceramic major source of delay at
Daresbury (1 year late)
Copper brazed joint!
First electrons August 2006
Three failures!
24
PI Commissioning Highlights

• Injector commissioning with dedicated diagnostic
  line

25
PI Results (1)
Bunch length at 10 of peak value vs. bunch
charge
RMS geometric emittance vs. bunch charge
40
ASTRA
Emittance (RMS), pi-mm-mrad
125ps
35
30
ASTRA
25
Bunch length _at_ 0.1 micro metres
20
15
10
5
28ps
0
80
0
10
20
30
40
50
60
70
Bunch Charge, pC
26
Gun Commissioning Summary

• Results
• The gun HV conditioned to 450kV. 250 kV operating
  voltage with smaller ceramics.
• QE above 3 are normally achieved after cathode
  activations (bunch charges of well above100pC
  have been achieved)
• The beam was fully characterised (emittance,
  bunch length, energy spectra) in a wide range of
  bunch charges from 1 to 80pC
• A good agreement between the ASTRA simulations
  and the experimental data was found in terms of
  the bunch length and the energy spread but not
  for the emittance.
• Remaining gun-related issues
• Ensure the absence of FE spots on the cathode
• Increase the cathode lifetime at QE level of
  gt1.5
• Transverse emittance is higher than expected (FE
  ? QE non-uniformity?) at 350 kV
• Reliable braze on large ceramic

27
Cryogenics and Superconducting RF

• Superconducting module status

28
Linac layout
Cavity 2, 12.9 MV/m
Cavity 1, 12.9 MV/m
29
Booster layout
Cavity 1, 4.8 MV/m
Cavity 2, 2.9 MV/m
30
Linac Module Performance
18
Cavity 1 (CW)
Power Limit
Cavity 1 (10 Duty)
16
Cavity 2 (CW)
14
Cavity 2 (10 Duty)
Operating gradient
12
10
Gradient (MV/m)
8
6
4
FE Quench
2
0
25/5/07 to 24/8/07
31
Field Emission Radiation Issue
Measurements from an ionisation chamber radiation
monitor, which is positioned 7 m away from the
Linac module, as the gradient in the cavity is
increased .
Even at 9 MV/m, which is the saturation point of
the rad monitor, it is predicted that the low
level RF electronics, close to the linac, would
have a lifetime of only around 1000 hrs. At the
operational gradient the lifetime would be much
shorter!
32
ALICE Accelerates Towards Energy Recovery

• October 23/24
• The electron beam was accelerated through the SC
  module to around 4 MeV.
• The next step will be to accelerate to full
  energy and circulate the beam to demonstrate
  energy recovery.
• The accelerator is now shutdown for four weeks,
  commissioning to energy recovery will commence in
  late November.

33
ALICE - not just an Energy Recovery Linac
E-BEAM
CBS X-ray
CBS
Phase I
EO diagnostic
532 nm
IR FEL
IR FEL
4-6um
4-6um
Phase II
THz
Photogun laser
TW Laser
34
ALICE Light Sources

• ALICE
• Light Sources

35
THz source parameters
Photons per pulse per 0.1 bandwidth into a
60mrad extraction aperture for a model 0.6ps
(rms) Gaussian bunch.
Pulse length (FWHM) 1.4ps THz Peak Power
0.07MW Rep Rate 81.25MHz Train Length / PRF
100ms / 20Hz Average Power 0.023W
thanks to M. Surman
36
TW Laser
Peak power 10 TW Pulse length 100 / 35
fs Wavelength 802nm Bandwidth 13nm PRF 10Hz
Pulse energy 0.8J (after compressor) Average
power 10W Focal spot 10mm Peak power density
gt1018 W/cm2
thanks to G. Priebe
37
Compton Back Scattering on ALICE
The energy of X-rays
38
CBS Phases I II
PHASE I
PHASE II
Side-on 90o photon-electron collisions
Head on 180o photon-electron collisions
39
IR FEL
IR l 4.3mm Peak Power 15MW Pulse Energy
10mJ Pulse Length FWHM 0.5ps
Good temporal transverse coherence
E-beamEnergy 35MeV, en10 mm-mrad,
sE/E0.1, st0.6ps
Option of a tunable IR FEL (see below )
40
Tunable IR FEL

• Tunability by varying
• electron energy (24-35MeV)
• undulator gap (12-20mm)

Motor and In Line Gearbox
l 4-12 mm
Encoders
41
NWSF Mobile Laser System
Pulse Length lt100fs l 240-1100nm gaps
333-360nm and 500-695nm f 81.25 MHz
(ALICE) Peak energy per pulse (_at_ 800nm)
gt30nJ
Pulse Length lt100fs l 240nm
-20mm continuously with OPA f up to 1 kHz
(e.g 20Hz ALICE) Peak energy per pulse gt1 mJ
(from TiSapphire amplifier)

• Output Wavelengths

TiSapphire Oscillator / Nonlinear Frequency
Conversion stage
TiSapphire Amplifier / Optical Parametric
Conversion stage
thanks to D. Graham
42

• Commissioning ALICE

43
ALICE Programme 2008 - 2009
First energy recovery Dec/Jan 2008/9 ALICE
fine tuning Jan-Feb 2009 ALICE short pulse
studies Jan 09 - --- THz research
programme Feb 2008 - E/O technique
profile and time-of-flight measurements Feb 2008
IRUVX WR 8.1 Synchronisation March 2008 -
IRUVX WR 8.2 Longitudinal profile
feedback March 2008 - --- CBS experiment
Phase I. March 08 - May 09 --- IR FEL
installation Commissioning May 2009 Energy
recovery with FEL June 2009 FEL Research
Programme July 2009 - --- Gun upgrade
Aug-Oct 2009 Gun beamline
upgrade Aug-Oct 2009 Improved high current
ERL cryomodule ? --- CBS experiment Phase
II Oct-Dec 2009
44
Beyond 2009
Setting ALICE for EMMA operation Nov - Dec
2009 EMMA research Jan Sep
2010 Photocathode research LINAC Transfer
matrix systematic investigation Beam losses and
halo investigation in ERLs Bunch slicing with
unipolar THz sources Beam tomography at high
bunch charge and low energy Electron bunch
preparation for laser wakefield experiments Laser
wakefield acceleration with external
injection IR FEL / TW laser / THZ pump-probe
based research and many more
45
ALICE First Energy Recovery

• ALICE first energy recovery
• no undulator installed
• minimal energy spread (acceleration on crest)
• not concerned with longitudinal phase space,
  bunching and de-bunching
• nothing particularly difficult here
• major ALICE milestone

46
ALICE Fine Tuning

• Achieving full energy and beam power (35MeV,
  80pC)
• Injector tuning
• minimal emittance (slit quad scans)
• optimisation of booster cavities phases settings
• buncher electric field optimisation
• etc
• Difference orbit measurements
• Setting the required linac phases and beam
  transport
• Optimising beam transport
• Measurements
• emittance
• Twiss parameters
• bunch length (zero-crossing and E/O methods)
• energy spectra

Transverse emittance as measured during the gun
commissioning ( too high due to field emission
from the cathode and non-uniform QE map ?)
47
ALICE Short Pulse Commissioning

• Initially, no FEL still not installed yet
• Longitudinal dynamics
• Linac phases tuning
• R56 tuning in ARC 1 ARC 2
• sextupole tuning
• longitudinal bunch compression setup
• min bunch length
• Phase transfer measurements
• using either BPMs or E/O
• THz measurements
• E/O bunch length measurements

48
EO beamline section
Beam profile monitor
Beam position monitor
Synchrotron radiation diagnostics
EO diagnostics table
Laser room
49
ALICE Short Pulse Commissioning
ALICE short pulse commissioning Longitudinal
Dynamics no FEL though
50
Short Pulse Commissioning with FEL
Transverse Alignment Align 3 principal axes
Magnetic, e-Beam, Optical Align Magnetic Axis to
nominal Survey in alignment wedges within
undulator Align Optical Axis to Magnetic Axis
Set Transverse and Angular mirror alignment by
adjusting mirrors so that HeNe alignment laser
steered through holes in wedges Align e-Beam to
Magnetic Axis Steer electron beam through holes
in wedges
Longitudinal Alignment Monitor spontaneous
emission signal and adjust cavity length to get
pulse stacking
thanks to N. Thompson
51
Short Pulse Commissioning with FEL
Modes of FEL operation
Normal Mode normal operation optimised output
power - hole outcoupling - angular alignment
tolerance 10mrad - jitter in e-beam position
30mm Commissioning Mode for achieving first
lasing - hole outcoupling on both ends of FEL -
smaller (x2) holes to minimise mode distortion -
no need to steer the IR to diagnostic
room Failsafe Mode in case the first two do not
work! - transmissive outcoupling - mode
distortion (due to holes) removed - angular
alignment tolerance increased (x4) - transverse
e-beam jitter tolerance increased (x2) - e-bunch
time-of-arrival jitter tolerance increased (x2) -
1.2ps e-bunch
thanks to N. Thompson
52
ALICE Energy recovery with FEL
Energy recovery with FEL

• Dealing with large energy spread after FEL
• Manipulations with R56 in ARC 2
• (bunch decompression)
• Achieving near full energy recovery
• Completion of ALICE commissioning
• First light !

The first Compton FEL in the UK will become
operational !
53
Electro-optic sampling of Coulomb field
probe laser co-propagates with bunch (with
transverse offset)
Coulomb field of relativistic bunch
probe laser
encoding of bunch information into laser
decoding of information from laser pulse
thanks to S. Jamison
54
Electro-optic technique for bunch profile and
time-of-arrival measurements
UK has leading position in EO longitudinal
diagnostics highest time resolution demonstrated
by UK/Dutch/German collaboration at FLASH
ALICE test-bed
For testing of modified concepts for real system
integration

• cost-vs-capability becoming a driver
  gt200k for our best resolution system! (cost
  mostly in the laser)
• investigate migration of techniques to fibre
  laser systems
• integration with timing distribution systems
  -profile info highly desirable for even
  arrival time diagnostics

EU-IRUVX funding for further prototype of EO
system on ALICE
Tests for external laboratories...
thanks to S. Jamison
55
ALICE Timing and synchronisation RD
Major issue in future/next-generation light
sources
require lt10fs timing stability for both machine
and user operation
leading solution...
Optical master clock and timing distribution

• single pulse circulating within cavity
• pulse repetition rate set by cavity
  round trip time...
• Cavity length / laser pulse train locked to
  accelerator master RF

cavity length susceptible to low frequency
noise/drifts...
Cavity frequency and phase actively stabilised
by locking to stable RF reference...
but.. very low noise at high frequencies
More stable than best RF oscillators
thanks to S. Jamison
56
ALICE Fibre Lasers Oscillators / Clocks RD
in-house build...
commercial system...
gain medium (Er fibre)
pump laser diodes
fibre stretcher (cavity length feedback)
polarising elements
plus..
Active length stabilisation of distribution
optical fibre..
Compare arrival time of outgoing and round trip
pulses - RF phase
detection 20fs sensitivity
- optical cross-correlation 1fs (?)
thanks to S. Jamison
57
ALICE Timing Synchronisation systems
ALICE test bed for timing synchronisation
systems
Tests to be implemented on ALICE in 2008-2009
(EU-IRUVX funding)

• installation of fibre oscillators in ALICE
  diagnostic room
• stabilised fibre distribution to accelerator
  area (initially to EO station)

We will investigate

• Environmental effects (vibration, radiation,
  temperature...)
• Long term stability / reliability

thanks to S. Jamison
58
ALICE Longitudinal profile feedback studies
concept recently proven at FLASH
Arrival time
phase or amplitude
Arrival of what? charge mean or peak current ?
development through EU/Marie Curie (in proposal
stage)
E0, j
E0, j
Arrival time beam profile (partial?)
more profile data ? more knobs available
motivation behind IR-UVX EO profile
investigations
We can do it on ALICE !
thanks to S. Jamison
59
THz Research Programme
THz Light for ALICE Diagnostics
When the electron bunches are short compared with
the wavelength of light, light is emitted
coherently. There is therefore a massive increase
in the power emitted at long wavelength. The
onset of this coherent emission is characteristic
of the bunch length, and the intensity, which
scales quadratically with number of electrons in
the bunch, gives a measurement of bunch charge A
Martin-Puplett FTIR system build in collaboration
with RAL Space science at RAL will be used to
obtain the THz spectrum of light from ALICE.
Conventional Synchrotron Light I a N
Coherently Enhanced Synchrotron Light I a N2
thanks to M. Surman
60
CBS experiment Phase I
Head on 180o photon-electron collisions
(relaxed synchronisation requirements)

• X-ray source characterisation
• spectrum
• X-ray pulse duration
• brightness (number of photons Np )
• Electron bunch / laser pulse time jitter
• shot-to-shot variations in energy spectra and Np
• better resolution expected in
  phase II
• First pump/probe experiment
• (but this more likely to be done during phase II)

• -Laser pulse travels through the length of the
  electron bunch
• X-ray pulse length electron bunch length
• relaxed synchronisation requirements

First X-ray pulses, Feb 2009
61
Future Plans

• Future Plans

62
Science Beyond Energy Recovery

• Accelerator physics research
• Photoinjector upgrade, load lock system and
  diagnostics line
• High average current accelerator module
• Photocathode research and testing (using the
  upgraded gun)
• Linac Transfer Matrix Investigation
• Beam Tomography _at_ High Bunch Charges and Low
  Energy
• Laser slicing
• Laser Wakefield Acceleration (LWFA) on ALICE
• EMMA the first NS FFAG
• CBS X-ray source
• IR and THz research programme
• Tissue Culture Laboratory _at_ ALICE
• Exciting pump probe research programme with all
  ALICE light sources
• TW laser (10TW, 100 / 35 fs, 10Hz)
• IR FEL (4mm, 15MW peak, 1ps, 10mJ)
• fs tunable laser
• THz radiation (broadband)
• CBS X-ray source (15-30keV, 107 108
  photons/pulse, lt1ps)

63
Injector upgrade

• Improved vacuum conditions
• Reduction of contamination from caesium ions
• Improved gun stability under high voltage
• Reduced time for photocathode changeover, from
  weeks to hours
• Higher quantum efficiency
• Allows practical experiments with photocathodes
  activated to different electron affinity levels

64
Photocathode Research
Emphasis on GaAs type of the photocathodes (inc
GaAsP)

• Photocathode structures for
• fast response time
• low energy spread (hence low thermal emittance)
• low field emission
• Preparation procedures for high QE, high
  lifetime and low field emission
• Experiments with Positive Electron Affinity
  photocathodes
• faster response time
• Photocathode tests on the Photocathode Testing
  Facility at DL
• Response time measurements (_at_ University of
  Mainz)
• Cathode testing and beam characterisation in
  situ (_at_ ALICE)
• - enabled by the photogun upgrade

• Potential collaborations
• TJNAF
• Institute of Semiconductor Physics, Novosibirsk
• University of Mainz
• Florida State University (Big Light)

65
ALICE Gun Beamline Upgrade (?)
1st booster cell
the diagnostic beamline has disappeared after
booster installation - was used for a
comprehensive e-bunch characterisation, setting
the buncher etc. - missed greatly now !! (and
JLab too )

• Returning the diagnostic BL will allow
• photocathode research in situ
• greater ALICE flexibility in beam parameters
• better overall beam quality
• incorporation of ion trapping devices

The effect on the bunch quality is still to be
calculated
66
High Current Cryomodule RD Collaboration
Realisation of a prototype superconducting CW
cavity and cryo module for energy recovery, P
McIntosh et al, SRF07 Beijing

• 5 collaborating institutes
• ASTeC (UK)
• Cornell University (USA)
• Stanford University (USA)
• Lawrence Berkeley Laboratory (USA)
• FZD Rossendorf (Germany)

67
Cryomodule
2 x 9-cell 1.3 GHz cavity
ERLP Module
10 kW CW fixed coupling FPC
68
ALICE EMMA First NS FFAG
Electron Machine with Many Applications
PROOF-OF-PRINCIPLE EXPERIMENT
EMMA Non Scaling Fixed Field Alternating
Gradient Accelerator
Construction of a Non-scaling FFAG for Oncology,
Research and Medicine CONFORM Project
(Basic Technology grant international
collaboration)

• Why FFAG ?
• fast acceleration (e.g. muons)
• high power beam acceleration
• variable electron energy

• Why Non Scaling ?
• compact beamline vacuum chamber
• hence, compact magnets

• Applications
• medical (oncology)
• muon acceleration
• Accelerator Driven Sub-critical Reactor (ADSR)

69
ALICE EMMA First NS FFAG

• Preparing ALICE for Emma
• Set energy 10 25 MeV (Alice nominal is 8 27
  35 MeV)
• Beam characterisation
• Bunch length / Charge / Emittance / Energy
  spread
• Q1pC and nominal (e.g. 16 or 32pC)
• Hardware and system commissioning
• EMMA Controls online model commissioning

• Proof-of-Principle quick acceleration large
  acceptance
• Orbit establishment
• Injection extraction studies
• Tune measurements
• bunch circulation for many (1000) turns without
  RF
• Aperture survey
• Resonance crossing studies
• Outside bucket acceleration studies
• Space charge and beam loading (if any) effects
• EMMA model validation

70
Bunch Slicing with Laser Driven THz sources
Traditional bunch slicing...
spatial separation through dispersion
Energy modulation imposed by ultrafast laser
FEL gain modified (attosecond schemes)
50 fs envelopein energy spread
2.6 fs oscillations
THz driven bunch slicing... (the concept)
small R56

• tunable quasi-monochromatic THz generated with
  TiS laser
• phase of THz under experimental control

thanks to S. Jamison
71
Bunch Slicing with Laser Driven THz sources
Laser Wakefield acceleration bunch preparation

• plasma charge density gradients from pondermotive
  laser force...
• relativistic electrons injected into correct
  phase of accelerating medium

plasma oscillation wavelength lp 100-30
micron Ne 1017 - 1018 cm-3
50fs duration laser pulse
Ideally require
Injected bunch length lt lp

• injected bunch sz ltlt lp
• femtosecond synchronisation between plasma wake
  and injected bunch peak current

These requirements could in principal be
delivered by laser-THz bunching
thanks to S. Jamison
72

• Some Photon Science

73
THz Programme Tissue Culture Facility
A world-unique facility allowing the effect of
high peak power / high rep rate THz on living
cells to be investigated. Weightman et
al University of Liverpool University of
Nottingham
THz has important role in security screening
74
THz Programme new solar cells
The solar energy problem
Global power requirements currently 13 TW set to
double by 2050, Most optimistic estimates of
capabilities renewables exc. solar 2-4 TW
(currently lt1 TW) nuclear fission 3-5 TW
(currently ca. 1 TW) Power reaching Earth from
Sun 100 000 TW Multiple exciton generation (MEG)
offers the potential for huge increases in solar
cell efficiency What is the mechanism of
MEG? How are carriers transported through these
cells? Need to measure initial charge injection,
exciton evolution and transport on ultra-fast
timescales
W.R. Flavell et al University of Manchester
75
THz Programme new solar cells
Laser pump THz probe measurements of internal
exciton transitions understanding MEG

• Internal energy levels of excitons accessible to
  THz (meV energies)
• Monitor the evolution of conductivity and
  dielectric constant as the initial single excited
  exciton produces multiple excitons on ps
  timescales

• Pump provided by NWSF-funded laser system (90 fs,
  Ti-sapphire oscillator and amplifier)
• Follows on from the successful programme of
  laser/SR pump-probe activity on the SRS

thanks to M. Surman
76
More exploitation projects on ALICEs table

• Gas Phase Science
• Field-free alignment and orientation of complex
  molecules
• Double resonance experiments on biomolecules

• Bioscience
• Multi-disciplinary consortium (Leeds, Imperial
  College, Manchester) exists and relies
• on light sources from ALICE
• Electron/proton transfer in Soluble enzymes
• Photosynthetic complexes and light driven
  proteins
• Extracellular matrix complex studies
• A number of other related experiments

• Condensed Matter Science
• IR FEL (pump) THz (probe) experiments on
  materials in strong magnetic fields
• Big Light / ALICE collaboration
• Initiation of surface reactions with THz light
• trial experiments (part of the catalysis
  research programme)

77
More exploitation projects on ALICEs table

• Nanoparticles and nanocells
• Laser/THz pump-probe studies of nanoparticles
  inc. photovoltaics and LED devices
• funded by NWSF
• crucial to NLS (accelerator/laser
  synchronisation)
• New high efficiency hybrid solar cell for
  roof-top microgeneration
• consortium led by Manchester Uni and Imperial
  College
• funded by EPSRC (from April 2007 for 4 years)
• A prototype solar nanocell for tandem
  photosynthesis of carbon monoxide and methanol
• Manchester/York/Nottingham/East Anglia
  consortium
• funded by EPSRC (from June 2008 for 3 years)
• TW laser applications
• MeV Electron Diffraction
• numerous !

78
Summary

• Accelerator commissioning has now reached a
  critical stage
• ALICE has provided the UK with an opportunity to
  develop generic technologies and skills important
  to delivery of advance accelerator driven
  facilities
• Photoinjector, SC RF, cryogenics etc.
• ALICE will provide a unique RD facility in
  Europe, dedicated to accelerator science
  technology development
• Offering a unique combination of accelerator,
  laser and free-electron laser sources
• Enabling essential studies of beam combination
  techniques
• Providing a suite of photon sources for
  scientific exploitation

Many thanks to all contributors to this
presentation