The First Year of Exploitation of CLARA Phase 1 - Deepa... · to-VELA beamline. • Cerenkov radiation produced when beam passes through optical fibres on the outside of the beam

The First Year of Exploitation of CLARA Phase 1

Deepa Angal-Kalinin

STFC Daresbury Laboratory & The Cockcroft Institute

IoP PAB Annual Meeting, RAL, 26th April 2019

Accelerators in a new light

Compact Linear Accelerator for Research and Applications (CLARA)

• A flexible high brightness test facility enabling the broad range

of accelerator and FEL R&D necessary to ensure a future UK FEL

facility is world leading.

• Will address many scientific and technology challenges for

future large scale UK X-FEL facility

• Will establish key technologies

– Photoinjectors and photocathodes

– Novel undulators (short period, superconducting….)

– New accelerating structures: X-Band etc ...

– Advanced single bunch diagnostics.

2

CLARA: Layout and Status

PH

ASE

1

PHASE 1:50 MeV, 100 pC at 10 Hz ACHIEVED

• Beam characterisation, machine development and beam exploitation

• RF Conditioning of 400Hz gun on VELA line

PHASE 2

PHASE 2:250 MeV, BEING PROCURED AND ASSEMBLED

• 2018: Module assembly offline

• 2019: Shielding changes

• 2021: Installation

• Still need some funding to complete

PHASE 3

PHASE 3:100 nm FEL

NOT YET FUNDED

• Will take ~ 3-4 years till Lasing when funded

FEBE

CLARA Phase 1 Accelerator Hall

CLARA Exploitation Call Process• An open call was made for access to CLARA beamtime in May 2018.

• Beamtime allocation panel:

– Andy Wolski, Liverpool University, CI (Chair)

– Phil Burrows, Oxford University, JAI

– Jim Clarke, ASTeC/STFC

– Tim Noakes (technical assessment), ASTeC/STFC

• 20 proposals submitted, 12 approved

– Total number of shifts requested = 135

– Total number of shifts allocated = 70

• Every proposal was judged to be worthy of beamtime

Discipline Area Number submitted Number approved

Accelerator Diagnostics Development 7 4

Accelerator Technology Development 3 2

Light Generation 2 1

Beam Physics 1 0

Novel Acceleration 4 3

Medical Applications 2 2

Space Applications 1 0

Total 20 12

Beam Area 1

~40 MeV

100 pC, 10 Hz~40 MeV

100 pC,10 Hz

VHEE (2)

SCU

Beam Loss Monitor

5 experiments in the accelerator hall & 7 in BA1 (4 using TW laser). Separate enclosure allowed exploitation experiments in the accelerator hall while setting up experiments in BA1.

Beam Area 2, ~25 MeV,

100 pC, 10 Hz

DWA, THz acceleration and deflection,De-chirperCTR/CDR, Plasma

wall

wallCBPM

CLARA/VELA – Exploitation Experiments

Continuously Tunable Dielectric Wakefield THz Source Y. Saveliev, T. Pacey et al., ASTeC/CI

• First demonstration of continuously tunable THz generation with dielectric wakefield structure

• Narrow-band single mode spectra (negligible HOMs)• Frequency range of 0.55-0.95 THz • High THz energy per pulse (even at low charge ~70pC

electron bunches) … pyro detectors to be cross-calibrated

• Limitations on frequency range and corresponding THz power studied

• Good match with theory and CST simulations • Paper to PRL in final stages of preparation

Dielectric Dechirper StudiesY. Saveliev, T. Pacey et al, ASTeC/CI

• First dielectric wakefield experiments (UK)• Demonstrated “capability” to conduct Dielectric

Wakefield Acceleration R&D on CLARA• All dechirper effects demonstrated• 7.5MV/m decelerating field measured

(~30MV/m accelerating field assuming no beam losses in structure and TR=2)

CLARA Phase II

dechirper

Beam deceleration

DechirpingStreakingEnergy modulation

Basis for future developments :• CLARA Phase II dechirper

implementation• DWA structure as bunch length

diagnostic• Transverse beam dynamics and BBU• International collaborations

Coherent Cherenkov Diffraction Radiation for Longitudinal Bunch Profile Diagnostics

P. Karataev, K. Fedorov et al, RHUL/JAI

The radiation spectrum has been measured using Martin-Pupplet Interferometer

Initial spectrumSingle electron spectrumNormalized spectrum

Longitudinal profile obtained via Kramers-Kronig method measured for two RF phases

-6 deg -11 deg

Beam Loss Monitor Commissioning

• Optical BLM installed along CLARA-to-VELA beamline.

• Cerenkov radiation produced when beam passes through optical fibres on the outside of the beam pipe, detected by SiPMs.

• Multiple losses at any location can be detected simultaneously.

A. Alexandrova, A. Brynes, F. Jackson et al ULIV, ASTeC/CI

Four points of beam loss detected by BLMs

GUI used for on-line commissioning

VHEE Dosimetry on CLARA and CLEAR (CERN) Facility

CLARA beam was used to resolve earlier observed discrepancy of factor of 7 in Gafchromic film-based calibration experiments at Christie hospital and experimental dose ICT-based measurements at CERN’s CLEAR facility.

R. M. Jones, A. Lagzda et al, UMAN, Christie, ASTeC/CI

Rescale the CERN results by a factor of 10 • DL – no more than 9.4 %

discrepancy!• CERN – now no more than 5.3%

discrepancy!

Plasmid Proportion vs. Dose for 20 MeV Electrons Plasmid Proportion vs. Dose for 30 MeV Electrons

Model μ (Mbp-1 Gy-1) φ (Mbp-1 Gy-1)

McMahon 8.18 0.22

Cowan 8.17 0.24

Model μ (Mbp-1 Gy-1) φ (Mbp-1 Gy-1)

McMahon 9.94 1.98

Cowan 9.91 2.29

μ is representative of Single Strand Breaks (SSB), Φ is representative of Double Strand Breaks (DSB)

VHEE DNA SSB/DSB EXPERIMENT at CLARAR. M. Jones, K. Small et al, UMAN, Christie, ASTeC/CI

Supercoiled

Open-Circular

Linear

Based on these fractional components the SSB (Single Strand Break) and DSB (Double Strand Break) rates are determined

Plasmid Constituents

THz Driven Deflector Structures With Beam

Resonator excited by THz pulse

THz generated by optical rectification

35 MeV e- beam to be streaked

Electric field

E- beam passing

through 20 um gap

Holder with resonator and various screens to allow alignment of resonator gap, the beam and the THz pulse

Experimental setup inside the chamber: THz pulse gets fed from the back. Beam passes from right to left

Raw experimental data:Variation of beam position and size

versus pulse delay showing the streaking action

The principleTHz resonator

M. Dehler et al, PSI/CI – ARIES TN Access

Plasma Afterglow Attosecond MetrologyA. Knetsch1, O. Apsimon2, L. Boulton1,3, A. Gleeson5, H. Jones2, G. G. Manahan3, A. Nutter3, T. Pacey5, L. Reid4, P. Scherkl3, E. Snedden5, D. Ullmann3, D. Walsh5, L. Corner4, B. Hidding3 DESY/CI, ARIES TN Access

A.

OTR

screen

Gas jet

TW laser

No Interaction with plasma

Interaction with plasma

• Successful synchronisation and alignment oflaser, electron beam and gas jet.

• First interaction of CLARA electron beam with laser-ionized plasma.

Industrialisation of Cavity BPMs for FELs

• Cavity BPM designed for 10..100 pC FEL beams

• Successor of development of precision diagnostics for linear colliders

• In partnership with FMB-Oxford, interest from iTech

• Simple cost-effective design• Complete system with electronics and

processing• 3 position and 1 reference cavities now

being tested in VELA/CLARA beamline• First beam data obtained, analysis

underway

A. Lyapin, A. Rimmer, RHUL/FMB-Oxford

4 cavities in the beamline

Analogue electronics

Digitiser system

Test of an In-Vacuum Superconducting Undulator

Our SCUPeriod = 15.5 mmBeam Gap = 7.4 mmNo. Periods = 16Peak field at 340A = 1TWorld’s first In Vacuum type

B vs Gap for different undulatortechnologies (15mm period)

J. Clarke, B. Shepherd et al

• ASTeC, Technology Department and

Diamond have all worked together to

design and build a prototype in-vacuum

SCU

• The advantage over other technologies

is shown on the graph

SCU - Experimental Results

• Demonstrate that the SCU can operate with beam without incident. YES

• Measure the thermal behaviour of the undulator with beam. YES

• Measure the spectrum of the photon beam to confirm the magnetic field

strength of the undulator and some insight into the quality of the

undulator (e.g. phase error). NO

• The SCU exhibited a large dipole field which steered the electron beam

significantly off axis – had to install extra steering magnets to get

electrons through the SCU – could not detect any light

– We measured the steering effect as a function of SCU current up to full field (340A,

~1T)

Preliminary Analysis:The influence of magnetic material in the vicinity of SCU is the likely cause.

We plan to make some simple changes to the SCU in the coming months to confirm this and then reapply for beam time to complete the tests.

J. Clarke, B. Shepherd et al

• First beam exploitation period with higher energy beam has been highly successful. Almost all experiments achieved excellent results.

• Fantastic team effort and technical support provided by ASTeC/Technology staff going the extra mile!

• The experiments performed were crucial for at least 10 PhD students.

• Some high impact journal publications are imminent. • CLARA is proving to be unique test facility – not only for the UK

but also for international collaborators.

Summary – CLARA 18/19 Exploitation

Acknowledgements to

the CLARA Team