Presentation on theme: "Jim Clarke ASTeC and Cockcroft Institute ALPHA-X Workshop, May 2013"— Presentation transcript:
1 Jim Clarke ASTeC and Cockcroft Institute ALPHA-X Workshop, May 2013 Overview of CLARAJim ClarkeASTeC and Cockcroft InstituteALPHA-X Workshop, May 2013
2 Update:Versatile Electron Linear Accelerator VELA is the new name for EBTFHigh brightness RF PhotoinjectorEssential technology for advanced electron facilitiesLight sourcesCollidersFirst RF Photoinjector in the UKNew tool for industry to develop new accelerator-based technologiesHealthcareSecurity scannersWater treatment….Two independent beam areas availableFunded August 2011
3 VELA Beam Transport Layout Beam InjectorBeamEnclosure 1BeamEnclosure 2
6 VELA Status VELA Approval – August 2011 VELA hardware commissioning started – Oct 2012RF Conditioning started – 30th Nov5.3 MW peak power achieved – 20th DecRF window vacuum leak identified – 11th Jan 2013RF Conditioning restarted – 21st FebMultipactoring observed as solenoid powered4.8 MW, RF window cracked – 6th MarchCeramic window fitted (Strathclyde)RF Conditioning restarted – 19th Mar5.7 MW peak power achieved – 2nd AprFirst electrons – 5th Apr 2013Shutdown for installation of all systems
7 CLARA Major upgrade of VELA Compact Linear Accelerator for Research and ApplicationsMajor upgrade of VELAA world class FEL test facility that can try out new ideas so they can be implemented directly into a future light source facility – we know there is a strong demand for these improvements from the NLS Science Case and direct interactions with usersIn parallel we will also be able test advanced accelerator technologiesThe investment in CLARA will pay for itself by reducing future risk and timescalesMore importantly, it will also make any UK future light source a world beater !
8 4th Generation Light Sources Free Electron LasersUltra high peak intensityVery short pulses of lightTuneableBasic FEL unstable in intensity and wavelengthImmature as a technology, plenty of scope for improvementFortunately lots of ideas exist for improving FEL stability (wavelength and intensity) and to make even shorter pulses of light but very few have been testedCan’t propose a major new facility based on an untested idea! Need test facility
9 Reviewing the field – Facilities Currently there are only five (soon to be three?) dedicated single pass FEL test facilities worldwide, two in the US (NLCTA and SDU), one in Asia (SDUV-FEL) and two in Europe (SPARC and MAX).Highest current priority for FELs is improving temporal coherence.Reducing size and cost is another common theme.An opportunity exists for a new FEL test facility looking at next frontiers.Extract from:A Review of Worldwide Test Facilities for Free Electron LasersDavid Dunning, ASTeC
10 Ultimate aims of CLARATo develop a normal conducting test accelerator able to generate longitudinally and transversely bright electron bunches and to use these bunches in the experimental production of stable, synchronised, ultra short photon pulses of coherent light from a single pass FEL with techniques directly applicable to the future generation of light source facilities.Stable in terms of transverse position, angle, and intensity from shot to shot.A target synchronisation level for the photon pulse ‘arrival time’ of better than 10 fs rms is proposed.In this context “ultra short” means less than the FEL cooperation length, which is typically ~100 wavelengths long (i.e. this equates to a pulse length of 400 as at 1keV, or 40 as at 10 keV). A SASE FEL normally generates pulses that are dictated by the electron bunch length, which can be orders of magnitude larger than the cooperation length.
11 Other Aims and Prerequisites To deliver the ultimate objectives of CLARA will encompass development across many areas:Generation and control of bright electron bunchesmanipulation by externally injected radiation fieldsmitigation against unwanted short electron bunch effectsLow charge single bunch diagnosticsNC RF photoinjectors andseed laser systemsHigh temporal coherence and wavelength stability through seeding or other methodsSynchronisation systemsGeneration of coherent higher harmonics of a seed sourceAdvanced digital low level RF systemsPhoton pulse diagnostics for single shot characterisation and arrival time monitoringNovel short period undulators
12 Goals, Opportunities and Benefits The proof of principle demonstrations of ultra-short photon pulse generation using schemes which are applicable to X-ray FELs and with extreme levels of synchronisation.The ability to test other novel schemes for increasing the intrinsic FEL output intensity stability, wavelength stability, or the longitudinal coherence using external seeding, self-seeding or other methods.The ability to generate higher harmonic radiation of a seed source using EEHG, HGHG, etc.The generation and characterisation of very bright (in 6D) electron bunches and the manipulation of the bunch properties with externally injected lasers.The development of advanced accelerator technologies, such as a high repetition rate NCRF photoinjector, single bunch low charge diagnostics, and novel photocathode materials and preparation techniques.The enhancement of VELA, in terms of energy, beam power, and repetition rate.The development of vital skills within the UK accelerator community, including providing excellent opportunities for PhD students and post docs to work on a world class accelerator test facility.To use the electron beam for other applications: ultrafast electron diffraction, plasma wakefield accelerator research, Compton scattering source of X-rays or gamma photons, and other novel acceleration schemes such as dielectric wakefield accelerators.
13 Flexible FEL LayoutBy implementing a flexible FEL layout, especially in the modulator region, it will be possible to test several of the most promising schemes.We are carefully comparing the various schemes and their detailed requirements – we do not anticipate testing them all!We are designing in this flexibility from the start.
14 EXAMPLES OF FEL SCHEMES ON CLARA SINGLE SPIKE SASE 100pC tracked bunch compressed via velocity bunchingSLICING + CHIRP/TAPER Short pulse generation using an energy chirped electron bunch and a tapered undulator E. L. Saldin et al, Phys. Rev. STAB 9, , 2006MODE-LOCKING Mode-locked amplifier FEL using the standard CLARA lattice with electron beam delays between undulators N. R. Thompson and B. W. J. McNeil, Phys. Rev. Lett. 100, , 2008MATCHED MODE-LOCKING Electron beam delays matched to the rms electron bunch length to distinguish a single spike from the pulse trainPlots courtesy of Ian Martin and Neil Thompson
15 Slicing Scheme Example Few-cycle seed laser is used to modulate the electron beam energy to an amplitude greater than the natural bandwidth of the FEL.By tapering the gap of the undulator, only the sections of the electron bunch where the energy chirp is correctly matched to the undulator taper will experience high FEL gain.CLARA Example:50 mm, 10 mJ, 500 fs seed laser
16 ParametersThe parameters have now been broken down to cover 5 different operating modes. This helps us understand which parameters we need simultaneously.25FEL output wavelengths from 400nm to 100nmCan make use of 800nm laser for harmonic generation experimentsCan use well established laser diagnostics for single shot pulse length measurementsNo need for long photon beamlines, can deflect by 90 degrees
17 RF Frequency & Rep RateThe current VELA gun (ALPHA-X) and the DLS 1 kHz gun are both SEUThere is significant effort within Europe on advanced RF guns using SEUCLARA will have an SEU gun and an SEU linac with an XEU linearizing cavityHigher rep rates (>100 Hz) will be useful forIndustrial applicationsFeedback systems for stabilizationSharing pulses amongst multiple facilitiesTechnology demonstration and leadershipA future national facilityCLARA has a maximum energy specified to be 250 MeV but it is not necessary (or even important) to attain this energy at the highest rep ratesThe vast majority of industrial users will be satisfied with 100 MeVWe have proposed that CLARA should have a repetition rate of 400 Hz but at a reduced linac gradient (and so beam energy). The infrastructure (eg RF modulators, lasers) should therefore be capable of up to 400 Hz operation. Full beam energy should be possible at 100 Hz.
18 High Repetition Rate NCRF Initial EBTF gun cavity (ALPHA-X) will operate at up to 10 Hz repetition rateHigh Rep Rate Gun DevelopmentScaled to S-band FLASH/XFEL gun cavity fabricated by DLS could be tested at up to 400 Hz with EBTF/CLARA (no RF pick up)New design is being generated and compared against DLS solutionCLARA LinacAssuming use of 3 x SwissFEL Injector linac structures ( to 25 MeV/m, 10MeV/m, 4.3 m long)A study on practical realisation of high gradient, 20 to 25 MeV/m, 400 Hz linac structures has carried out by AES – solution proposed looks feasible and realisticX-Band RF Source Collaboration initiated with CERNDevelopment of low cost RF source for linearising cavity
19 CLARA Layout 4th Harmonic Cavity Further exploitation line Photon DiagnosticsGun4m linacFEL afterburnerLaser Heater2m linac4m linacs70MeV250MeVBunch CompressorTDC2FEL radiatorsTDC1FEL modulatorDumpEBTF exploitation areaTotal Length ~ 90m
21 Impact on VELA CLARA axis is offset by 1m from VELA CLARA Front EndCLARA axis is offset by 1m from VELAVELA photoinjector laser/RF system used by CLARA gun (VELA gun cavity initially as well)Existing VELA beamline will stay in place (after first 5m)CLARA will then feed VELA at up to 25MeV (cf 5MeV)Option for new themionic gun for VELA available if required
22 Other Opportunities Time Resolved Electron Diffraction Grant proposal submitted for ultrafast electron diffractionWill be incorporated into existing VELA for demo experiments, aiming to incorporate within CLARA laterPlasma accelerator researchsee next talkTHz source for scienceCompton fs gamma or X-ray sourceHigh energy beamline for industrial exploitationDielectric Wakefield Acceleration ExperimentsExotic storage rings (eg optical stochastic cooling, non-equilibrium light source, integrable optics lattice)
23 Next Steps CDR now being drafted TDR will follow CLARA funding still to be securedSwissFEL linacs released Jan 2015If procurement starts April 2014 then could install in first half of 2016CLARA first commissioning – mid 2016
25 AcknowledgementMany thanks to colleagues from ASTeC, Technology Department, Strathclyde University, SwissFEL, LAL, the Cockcroft Institute, the John Adams Institute, and Diamond Light Source for their contributions to this talk and the CLARA project