Linacs. Susan Smith. Daresbury Laboratory Mami and Beyond

Transcription

1 Energy Recovery Linacs Susan Smith ASTeC/Cockcroft Daresbury Laboratory Mami and Beyond

2 Introduction to ERLs Contents Operational ERLs Applications Challenges ERL Prototypes and R&D Summary 2

3 Introduction to Energy Recovery The Green Machines!

4 Energy Recovery Linac Arc FEL or Interaction point Energy Recovery Linac Compressor IR-FEL Photoinjector Laser Booster LINAC Linac Acceleration/Deceleration High brightness electron source

5 Characteristics of ERLs Advantage of ERL vs Storage Ring Non-equilibrium conditions Beam characteristics determined by injector Small emittance Ultra short bunches Storage Ring ERL Advantage of ERL vs Linacs Improvement in efficiency Electrons stored Enormous Increase in average current (CW) Reduced dump activation Energy stored 5

6 Operating ERLs

7 Oscillator FELs Require short intense bunches of electrons Disrupts the beam and induces large energy spread Storage rings can t provide the short intense bunches or cope with easily with the large induced energy spread LINAC can t provide the high average powers economically 7

8 ERLs Four ERLs all with oscillator FELs JLAB Daresbury BINP JAEA/JAERI 8

9 JLab Photoinjector Superconducting Linac First high current, energy recovery experiment at JLab FEL, 2000 RF Power Draw in Energy Recovery Energy Recovery Loop JLab ERL-based Free Electron Laser 1 MW class electron beam, (100 MeV x 10mA), comparable to beam power in CEBAF accelerator (1GeV x 1mA), but supported only by klystrons capable of accelerating kw electron beam. RF Power (kw/klys stron) Measured No Energy Recovery Max Klystron Output Measured w/ Energy Recovery Current (ma) 9

10 JLab Energy Recovered Linac (4GLS) facility schematic E = 150 MeV 135 pc pulses up to 75 MHz ~10 ma Beam current All sources are simultaneously produced for pump-probe studies 10 Thanks to George Neil

11 CEBAF-High energy demonstration of ER 500 MeV (Efinal / Einj) of 20:1 and 50:1) 50 MeV 500 MeV 500 MeV 500 MeV 50 MeV 1 GeV 1 GeV 11

12 NovoFEL Stage 1 Bunch repetition rate, 22.5 MHz Average electron current, 30 ma Maximum energy, 12 MeV RF Frequency Bunch length, 100 ps Normalized emittance, 30 mm*mrad mrad 12

13 Stage 2 Under Commissioning 13

14 Full Scale FEL 14

15 Genndy Successful 4 Pass Operation World s first demonstration of recirculation followed by deceleration in an ERL. 9 ma of beam at 20MeV Thanks to Gennady Kulipanov 15

16 ALICE Accelerator Layout Energy recovery demonstrated on ALICE 20 December Nominal Gun Energy 350 kev Injector Energy 8.35 MeV Circulating Beam Energy 35 MeV RF Frequency 1.3 GHz Bunch Repetition Rate MHz Nominal Bunch Charge 80 pc Average Current 6.5 ma (Over the 100 μs Bunch Train) 16

17 Parameters of Operational FELs JLAB * JAEA ALICE Daresbury Achieved/Design Novosibirsk THz FEL/Upgrade RF Frequency 1.5GHz 500MHz 1.3GHz 180 MHz E (MeV) /35 15/20 I (ma) ave ** 1.6/6.5 5** 40/9 ε n 7 30 /7 30/ Bunch 120 fs 12ps length (rms) (fwhm) /<1ps ns Bunch Repetition Rate (MHz) Duty Factor (%) / * Not all simultaneously ** In the macropulse 17

18 Summary 1 Existing ERL oscillator ERLs are excellent demonstrators of the ERL principle CW Average currents of up to ~10 ma (40 ma at thigh h emittance) High repetition rates:- 81MHz, 75MHz (CW) High efficiency > 99.97% Stable user operation High average photon power 18

19 Summary 2 Test bed for future ERL based sources (including CBAF ) Bench mark physics studies / simulations BBU, space charge, wakefields, longitudinal gymnastics High order transport measurements BBU observation, characterization, and suppression RF control tests at high Q L Beam loss measurements and control Resistive wall wakefield effects LSC and CSR effects Transverse and longitudinal acceptance of an ERL High FEL extraction efficiency studies ERL Diagnostics development Producing world leading sources of THz, IR 19

20 Applications

21 Proposed ERL Light Source Projects projects Oscillator FEL Kaeri Similar to JAERI FEL National High Magnetic Field Laboratory (Florida) PK-FEL MeV, 1 ma (avg), 5 mm mrad (TESLA cavities in Stanford/Rossendorf module c.f. ERLP) JLab 100 kw IR-FEL Spontaneous Emission MARs Cornell 5 GeV X-Ray ERL KEK 5 GeV ERL JAEA 6 GeV ERL at Naka site APS 7 GeV ARC-EN-CIEL SACLAY BERLin 21

22 courtesy Iva an Bazarov X-ray ERL e.g. Cornell ESRF ERL High flux 100 ma, 2 ps, 77 pc, norm emitt 0.3 mm mrad 25m undulators, small gap, short period undulators High coherence mode 25 ma, 2 ps, 19 pc, norm emitt mm mrad Ultra fast 1 ma, 50 fs, 1000 pc, norm emitt, 5 mm mrad ESRF 5GeV@100mA ERL 5GeV@100mA 16ps 100fs 2ps 22

23 Other ERL Applications Electron cooling of intense high energy ion beams Polarised electron beam for Electron-Ion Collider Generating very intense beams of γ-rays for many applications in HENP producing beams of rare isotopes polarized positrons transmutation of nuclear waste. 23

24 Electron Cooling 24

25 Electron-Ion Collider Electrons: Beam rep-rate [MHz] 14 Beam energy [GeV] 2-20 RMS normalized emittance [μm] 5-50 for Ne =1010 / 1011 e- per bunch β* ~ 1m, to fit beam-size of hadron beam RMS Bunch length [m] 0.01 Electrons per bunch Charge per bunch [nc] Average e-beam current [ma]

26 Applications Landscape APS Cornell 26

27 Challenges!!

28 Injectors DC photoinjector SC RF Photoinjector DCSC Photoinjectors Superconducting cavities HOM damping Challenges Beam break-up instability (BBU) RF control, of high Q cavities Beam transport Longitudinal space charge Coherent synchrotron radiation Halo and beam loss Longitudinal phase space manipulations (FELs) Resistive wall wakes (small gaps e.g. undulators) Beam stability 28

29 Prototypes and R&D

30 ALICE Injector upgrade ALICE photocathode gun equipped with a photocathode preparation & exchange facility Improved vacuum conditions Reduction of contamination from caesium ions Improved gun stability under high voltage Reduced time for photocathode th changeover, from weeks to hours Higher quantum efficiency Allows practical experiments with photocathodes activated to different electron affinity levels 30

31 ALICE Photocathode Research Emphasis on GaAs type of the photocathodes th (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 University of Mainz) Cathode testing ti and beam characterisation ti in situ ALICE) - enabled by the photogun upgrade Potential collaborations: TJNAF Institute of Semiconductor Physics, Novosibirsk University of Mainz Florida State t University it (Big Light) 31

32 High Current Cryomodule R&D Collaboration Realisation of a prototype superconducting CW cavity and cryo module for energy recovery, P M c Intosh et al, SRF07 Beijing 5 collaborating institutes ASTeC (UK) Cornell University (USA) Stanford University (USA) Lawrence Berkeley Laboratory (USA) FZD Rossendorf (Germany) 32

33 Cryomodule Upgrade ALICE Module 2 x 9-cell 1.3 GHz cavity 10 kw CW fixed coupling FPC 33

34 Example ALICE R&D Electro-optic optic longitudinal (temporal) profile monitors Improve capabilities beyond our already work leading demonstrations platform for rapid testing of new concepts move proven capability into realm of realistic accelerator technology (NLS) Beam arrival monitors test bed for fibre-laser driven BAMs... develop lower charge (<200pC) systems necessary for NLS develop pp peak-current BAMs (necessary for NLS ) Timing and synchronisation (sub picosecond) testing of long term reliability / capability of laser based clocks and timing distribution environmental impacts on timing/sync system Laser (& THz)-electron beam interactions ti test novel concepts for energy/density modulation imposed from laser based sources precursor to micro-bunching beam physics studies 34

35 Cornell Test Facility

36 Cornell Test Facility

37 Gun 37

38 Cornell Test Facility

39 Cornell Test Facility 39

40 Cornell Test Facility ma (at 1.3 GHz repetition rate) at 5 MeV All of the hardware is installed to run 100 ma at 5 MeV Running the gun at 250 kv due to problems with the HV ceramic Thanks to Bruce Dunham 40

41 BNL s R&D ERL 2 MeV Superconducting RF gun 20 MeV superconducting accelerating cavity Planned dto operate at t ampere CW 41

42 42

43 Status Gun cavity to be delivered in May Accelerating cavity tested at 20 MV with Q of Complete ERL test by Thanks to Ilan Ben-Zvi 43

44 JLAB Up-grade gun for FEL Facility kv 750 MHz, 100 ma gun High current module 750 MHz R&D towards 100 ma 100 kw FEL 44

45 BERLin-Pro Thanks to Bettina Kuske et. al. Spent Beam Extraction Main Linac SRF Module Merger Section 5-10 MeV SRF Booster Module SRF Gun 1.5 MeV Beam Dump Return Arc Beam Manipulation Undulator tests 100 MeV *h *short pulses mode at tincreased energy spread Parameter BERLinPro Parameter BERLinPro Beam Energy 100 MeV Normal. Emittance 1.0 π mm mrad Current 100 ma Rel. Energy Spread 10-3 Bunch Charge 77 pc Bunch Length 2 ps (100 fs)* Bunch Rep.-Rate 1.3 GHz 45

46 Summary

47 Summary Operating ERLs continue to reach higher performance and to serve as test-beds for accelerator science and technology development. The operation, performance, and R&D carried out in the existing ERLs provides invaluable guidance to the ERL field in general. Future applications of ERLs envisage more that an order of magnitude increase in beam current and two orders of magnitude in electron beam power. Prototyping is essential and the first extrapolation of performance of critical R&D is on the horizon (100 ma class machine!) The interest in using ERLs is worldwide and expanding What next? 47

48 MAMI and Beyond? 48

49 ERL09 Cornell June 8 th -12 th