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The CLEAR test facilityCERN Linear Electron Accelerator for Research
Erik Adli
Department of Physics, University of Oslo, Norway and CERN
With the CLEAR team: W. Farabolini, D. Gamba, R. Corsini, S. Curt, S. Doebert
K. N. Sjøbæk, G. McMonagle, P. Skowronski, F, Tecker …
Special thanks to CLEAR technical support people, groups and services involved in the modification/re-commissioning of CTF3 (RF, BI, CO, EN, TE/VSC, …)
CERN A&T seminar, November 30, 2017
https://clear.web.cern.ch
CLIC Test Facility and CLEAR
30 A, 140 ns
120 MeV
30 A, 140 ns60 MeV
3
CLEAR consists of the experimental hall, CLEX, housing the 200 MeV S-band electron CALIFES linac.
The test facility shut down at the end of 2017, after completing main targets.
CLIC Test Facility and CLEAR
History• Interest from external users, outside and within the CLIC,
project to keep an electron test beam facility at CERN• Should be open to all users, not only CLIC or linear
collider related activities• Workshop to poll interest from outside community held
in September 2016; more than 90 participants from different laboratories and different research fields
• Approved by CERN management for 2+2 years operation• Modification and some upgrades first half of 2017• First beam: August 18, 2017
From DG's New Year address January 2017 :
CLEAR parameters
Energy
Bunch-length(rms)
Present and planned European electron test beams(not complete)
10 MeV
1 fs
1 ps
100 MeV 1 GeV
10 ps
Open user facilityOpen through collaborationNot open for users (yet)
CLEAR (CERN) 2017
SINBAD (DESY H.) 2018
PRAE (Orsay) 2020
SPARC LAB (INFN Frascati) online
Flash Forward(DESY H.) 2017
CLARA (Daresbury)Online@50 MeV
MaxIV injector(MaxIV) ?
PITZ (DESY Z.) online
More details can be found at https://goo.gl/sn4dqP
FLUTE (KIT) 201?
CLEAR parameters
CTF3 Two Beam Module area (as it was)
CLIC Two
Beam Module
CALIFES(about 23 m long)
Spectrometer and
diagnostic
The idea: add some more space for new experiments
Exhange of RF StationsSignificant RF replacement and upgrades for the preparation of CLEAR
• The Modulator/Klystron MKS30 is being transferred to AWAKE.
• The RF network of MKS11 and MKS15 (compatible with requirements from TE/EPC andBE/CO), was reconfigured to feed the CLEAR linac.
G. McMonagle
CLEAR: “making of”Montage by D. Gamba
CLEAR completed due to heroic effort by Wilfrid Farabolini and Davide Gamba.
CLEAR experimental beam-line(s) (as it is)
Plasma Lens
former
CLIC Module
Available test space
Spectrometer and in-air test stand
CALIFES
injector
VESPER
Highlight from the 2017 run
M. Talis, R. Garcia Alia,
W. Farabolini et al.
Operation resumed in September:• Using dark current only• 10 pC total charge• 5 Hz repetition rate• Energy from 60 to 180 MeV
Successful measurements with
ESA and TRAD in week 46!
Overnight and over weekendoperation possible.
VESPER
First tests at VESPER: European Space Agency (ESA)
Beam homogenity - 175 MeV, 8 pC/pulse
Radionsensitive film ESA SEU monitor
First tests have been performed with ESA SEU monitor, results compatible with previous years :
50, 115, 175 MeVESA SEU monitor + AlRadiosensitive films
From Maris Tali
A.Lyapin (R. Holloway), J. Nadenau (Juelich), M. Wendt(CERN), R. Lillestøl (Oslo), E. Adli (Oslo), K.N.Sjøbæk (Oslo) et al.
Experiments resumed last week!
Former CLIC module: cavity BPM and wake field monitor tests
New installations for CLIC Wakefield monitors in CLEAR: • Combined cavity BPM and WFM measurements• variable phase shifter measurements on WFMs
Data from last week (to be analysed in detail)
A. E. Dyson, C. Thornton, and S. M. Hooker, Rev. Sci. Instrum. 87, 093302 (2016)
Active plasma lens studies
Oxford Compact Marx Bank: Inexpensive and precise source of ~20 kV, ~500 A discharges
Capillary and holder design by DESY, based on experience from DESY and Oxford
Overall experiment design, and assembly, integration and test, by Oslo.
Goal: strong, linear radial focusing from driving current a gas discharge.
Novelty for CTF3:- Gas in beamline- HV in beamline- New materials- Thin-foil vacuum
barriers
Plasma lens:Integrations and tests in the lab completed(August 2017)
C.A. LindstrømJ.H. RøckemannA. Dyson
Huge amount of work (integration of gas, HV, vacuum, beam windows),but, CLEAR vacuum integration now completed.
First electron beam sent cleanly through capillary end September. Marx bank outside
vacuum, but close to capillary.
Clean beam observed on downstream OTR
OTRIntegrated incapillary holder
Plasma lens:Latest commissioning results, from last night (30/11, 23h30)
Possible first focusing effect observed!(no analysis done, very preliminary!)
However, we still have a problem with sparks to ground.-Currently working on increasing gas path length to ground- Also changing from He to Ar
(No Champagne yet :( )
Reference shot: no discharge
”Late night crew”
BI Activities
T. Lefevre, et al.
Many activities planned (most ongoing).
Two main goals:
1) Consolidate and improve beam
instrumentation for CLEAR
2) Diagnostics R&D
OTRI setup
BI Activities
T. Lefevre, et al.
Several beam diagnostics recovered from CTF3, and adapted to CLEAR needs.
Will assess performances, modify if needed, eventually extend numbers.
WCM
Inductive
BPM
Beam Phase
monitor,
WG monitor
(bunch length)
OTR, ChR, ChDR
setup
Successfully seen first signals on
modified instrumentation.
To be continued!
AWAKE spectrometer, BPMsTest and calibration of AWAKE electron spectrometer, for electron commissioning Dec 2017. AWAKE BPMs also tested in CLEAR/CTF.
o Rapid advances in compact high-gradient (> 𝟏𝟎𝟎MV/m) accelerator technology in recent years CLIC (> 100 MV/m) NLC (~70MV/m), W-band (> 200MV/m)*
• Superior dose deposition properties compared to MV photons
• High dose-reach in tissue
• High dose rate (compared to photons)
• More reliable beam delivery around inhomogeneous media
• Better sparing of surrounding healthy tissue
• Particle steering
VHEE
𝟓𝟎𝐌𝐞𝐕 𝐕𝐇𝐄𝐄
𝟐𝟓𝟎𝐌𝐞𝐕 𝐕𝐇𝐄𝐄
Dose maps of wide (𝝈 = 𝟐𝟎𝐦𝐦) VHEE beams in water
50 MeV
150 MeV
Dose maps of narrow (𝝈 = 𝟓𝐦𝐦) VHEE beams in water
250 MeV
M. Bazalova-Carter et al, «Treatment planning for radiotherapy with very high-energy electron beams and comparison of VHEE and VMAT plans», Medical Physics, vol. 42(5), 2015.
VHE
E
VMA
T
Absorbed dose histograms for surrounding organs-at-risk.
• Clinical studies by M. Bazalova-Carter et al.
(2015) have compared 100 MeV VHEE with conventional (𝟔 and 𝟏𝟓MV) VMAT (Volumetric Modulated Arc Therapy) photon radiotherapy plans
• Pediatric brain tumour, lung and prostate cases
• VHEE therapy plan showed a decrease of dose up to 70% in surrounding organs-at-risk (OARs)
• VHEE plan was found to be more conformal than VMAT plan
*V. Dolgashev, HG2016
Brain tumour dose maps for 100 MeV VHEE and 6 MV volumetric modulated arc photon therapy (VMAT) .
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VHEE: Very High Energy Electron Radiotherapy
Manchester University: A. Lagzda, R. Jones and other- Project to characterize VHEE irradation on radiosensitive films
VHEE experiments at CLEAR
Beam parameter (end of linac)
Value range
Energy 197 MeVEnergy spread < 0.5 MeV FWHMBunch charge 0.5 nCTrain length 50 bunchesBeam spot size 1 mmCharge Jitter ≈ 20 %Relative energy spread 1 %
• Beam dosimetry experiments in water tank with radiosensitive films.
• Preliminary studies was done December 2016.• Planned for CLEAR/VESPER week 49, 2017.
BeamToroid
Beam alignmnent
screensMoving stage
Water tank with films
30 cm
46 cm
• 100 bunches of 50 pC/shot spaced by ~1 sec. at 8 cm distance corresponds to 100 Gy.
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A. Lagzda et al., IPAC’19
Injector optimisation
• Collaboration with LAL colleagues.
• Aim to:– Verify the theoretical best
performance achievable (0.1 ps bunch length, 5 mm-mrad possible?)
– Crosscheck of ASTRA simulations.– Guide the optimisation of our injector.
26 Oct 2017
CLEAR operation 2017
Week
33First beam!August 18
34Cont’dcommissioning
35Cont’dcommissioning
36First beam to usersVESPER
37Installation ofplasma lens
38Beam throughplasma lens
39VESPER
40Beam tuning,plasma lens
41BCM improvementWFM
42WFMFirst sparkplasma lens
43Inductive BPMsLAL: injector optimisation
44Cavity BPMs
45Laser spot studyVESPER
46ESA at VESPERTHz studies
47CombinedWFM and Cavity BPMs
48AWAKE screen
49: VHEE50-51: Plasma lens, instrumentation, THz….
Upcoming activities
In vacuum test space• About 1.5 m available space.• Possibility to install equipment on remotely controllable transverse mover (>10 mm range)
Transverse mover
End-of-line in-air test space
Ready to be exploited!
Novel accelerator techniques: THz
Steve Jamison, CLIC Workshop, CERN, March 2017 :
Study of THz generation (2017+) : THz acceleration (2018+ ?) :
Collaboration CLEAR – STFC/U. Rome being discussed. If moving forward: significant amount of resources (manpower, hardware, diagnostics ) to CLEAR starting from ~ 2018.
This effort would also profit other CLEAR experiments.
M. Petrarca, CLIC Workshop, CERN, March 2017 :
(from the 2016 workshop)
• Reviewing possibilities for generating coherent
THz pulses using short electron bunches
1. Coherent Transition and Diffraction
Radiation from metallic foils or slits (nJ to uJ)
• Discussing Simulation tools:• i.e. CST, Magic, Vsim
• Defining a plan for having first tests on CLEAR of Coherent radiation
by the end of 2017 up to frequencies of 0.1GHz
• Defining a roadmap for having short electron bunches available on
CLEAR in 2018
2. Higher power using Coherent Smith-Purcell Radiation in grating or Coherent
Cherenkov Radiation in dielectrics and meta-material
Coherent Cherenkov radiation in prismastic target with Magic
First topical CLEAR user workshop: THz (40 people, 13 talks)
https://indico.cern.ch/event/672235/
From T. Lefevre, CERN
• THz for beam diagnostics measuring short bunches,
e.g. in AWAKE measuring coherent radiation up to
320GHz
• A THz platform on CLEAR for developing THz sources and THz
detectors : i.e. in contact with PSI and universite of Chambery
• THz for acceleration using beam-based and laser-based THz
generation techniques
Example with the in-air testing area at
the end of the CLEAR
Identifying THz Applications and Synergies
New CERN fast Wire scanners for PSB, PS, SPS and LHC
From T. Lefevre, CERN
2018: test of wire scanners with beam.Measure fields on antenna in tank.
X-band and high-gradient R&D
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CLEAR: may get access to 12 GHz 50 MW RF power supply (X-box 1). Could be connected to CLEAR in 2018. Would increase energy to 250-300 MeV
Could be used for generic high-gradient studies, beneficial for CLIC, FEL, medical etc :1. The effect of a beam on the high-gradient behavior of a structure : Example: beam
loading effect on gradient (17% less output field with beam). A CLEAR program allows new studies such as effect of controlled beam loss on gradient, as well as continuation of tests of beam loading.
2. The effect of high-gradient acceleration on the beam. Example: further understand effect of break down and dark current on beam quality and luminosity.
3. Further Wake-fields and structure-based beam measurements. Example: resolution measurements with X-band acceleration mode
Possible upgrades:Towards a unique test-facility
To fit all proposed experiments, both space and downstream compability may be very challenging to handle with a single beam line. Space and hardware exists for a second beam line. Probable push to prepare the second line sometime in 2018 (but pending review of all requests).
Several users also ask for shorter bunches (fraction of a ps). Bunch compressions could be built into dogleg (studies have started).
AWAKE, CLEAR synergy:short pulse electron injector
• Interesting option for AWAKE 2nd run and CLEAR upgrade, using x-band technology for acompact injector
• Much of the X-band hardware might be available, X-band expertise exists in the CLIC project• The possibility of ultra short bunches could be a big asset for the future test facility
AWAKE Run 2 requirements:E. Adli et al., WEPMY008, IPAC’16
Design is taking shape,S. Doebert, CERN and M. Kelisani, IPM
S. Doebert, EAAC 2017 :Ultra-short bunch injector for AWAKE RUN2
How to become a CLEAR user
CLEAR Scientific Board
2017: most users contributed with ideas/proposal at ”CALIFES workshop 2016”
From 2018 proposals for experiments or test beam will pass by the CLEAR Scientific board.
The CLEAR Scientific Board will meet about meet 2-3 times per year to review the progress of the experimental program, and to referee the new proposals of the experimental teams on the basis of their physics interest and of the availability of the facility.
First meeting will be around the CLIC workshop 2018.
A Technical board will also meet at the same frequency, in order to review the technical, safety and radio-protection issues on the experiments recommended by the Scientific Committee, and fit them in the facility schedule.
Similar structure to HiRadMat.
CLEAR Experimental Requests
https://clear.web.cern.ch/sites/clear.web.cern.ch/files/documents/CLEAR_Experiment_Request_Form.docx
The experimental teams should also provide manpower to integrate experiments into the beam line and control system, and to help operate them during beam time.
Questions: CLEAR-Info@cern.ch
Conclusions• CLEAR: 200 MeV electron beam test facility at CERN
• Started operation August 18, 2017
• A mix of existing users - including CLIC, AWAKE [- and new users are already using CLEAR
• Instrumentation, linear collider technology, novel acceleration technology, irradiation…
• Interested users are encouraged to take contact with the CLEAR team, fill out experimental requests
• With added short bunch injector and two beam lines, CLEAR would have unique test-facility characteristics in Europe
Thanks a lot to Davide Gamba, Wilfrid Farabolini, Robert Corsini, Thibaut Lefevreand many others, for providing material for this presentation.
Extra
CERN ABP Impedance studies. first candidate: study of SPS wire scanner heating. Complexity of problem makes numerical studies and bench measurements. possibilities for CLEAR tests in 2017-2018.
Other interests in CLEAR
Impedance studies Electron irradiation studies
CLEAR: open facility, all user/communities welcome to propose experiments.
R2E: Tests for ESA space missions (Juice)(ESA, Jyvaskyla and others)
Tests for VHEE radiation therapy(Cockcroft)
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