SwissFEL Diagnostics Layout

Transcription

1 Wir schaffen Wissen heute für morgen Paul Scherrer Institut Rasmus Ischebeck SwissFEL Diagnostics Layout PSI,May 02, 2010

2 P AUL SCHERRER INSTITUT SwissFEL Diagnostics Layout Rasmus Ischebeck Diagnostics Concept Beam Position Monitors Profile Monitors but wa Longitudinal Diagnostics!-%2,12#67&89 Photon Diagnostics

3 SwissFEL Layout Photocathode Laser Undulators Beamlines TDS 250 MeV 1.5 GeV GeV ACC1 BC1 ACC2 BC2 ACC3 6.4 GeV Aramis FEL-1 Gun 12 GHz Accelerating Spectrometer Structure Porthos nm FEL nm ACC: Accelerating Structures BC: Bunch Compressor FEL: Free Electron Laser FODO: Focusing - Drift - Defocusing - Drift HHG: High Harmonic Generation TDS: Transversely Deflecting Structure Seed Laser HHG D Artagnan Modulator Athos FEL nm A free electron laser for wavelengths from to 7 nm Two beam lines Low beam energy allows for a compact setup Rasmus Ischebeck

4 Comparison of XFELs Rasmus Ischebeck LCLS SCSS EU XFEL SwissFEL Wavelength nm Design Peak Brilliance * ** Electron Energy GeV Normalized Slice Design Emittance µm Undulator Period mm Gain Length m Saturation Length m Facility Length m Start of Operation Source LCLS TDR (SLAC-R-593) * number of photons / s mm 2 mrad 2 0.1% bandwidth ** calculated with Ming Xie formulae SCSS CDR (Highest photon energy XFEL at each location) XFEL TDR (DESY )

5 2(3) Beamlines, 5 Operating Modes Beamline 1 Aramis Beamline 2 Athos with d Artagnan Beamline 3 Porthos (upgrade) Wavelength nm nm nm Photon Energy kev kev kev Rasmus Ischebeck Tuning Electron Energy Undulator Gap Undulator Gap Undulator Type Cryo, in-vacuum APPLE APPLE Undulator Length m m m K-Value Period 15 mm 40 mm 40 mm Gap 4 mm mm mm Electron Energy GeV 2.1 / 3.4 GeV 2.1 / 3.4 GeV Normalized Slice Emittance 0.43 µm 0.43 µm 0.43 µm Electron Bunch Charge 200 / 10 pc 200 / 10 pc 200 / 10 pc

6 Undulators for the SwissFEL In-vacuum undulators for Aramis 15 mm period 4 mm gap Tunability: electron energy (small gap tunability for taper) NdFeB with diffused Dy U-19 undulator for the SLS APPLE undulators for Athos Variable polarization 40 mm period mm tunable gap APPLE-II undulator for variable polarization Rasmus Ischebeck Thomas Schmidt

7 Diagnostics Concept Overall layout SwissFEL: 2 dedicated diagnostics sections, to be ready 2016 After BC1 In the bypass to the low-energy undulator Presently, we are developing diagnostics for the SwissFEL Injector Test Facility Gun region After BC1 Some redundancy in SwissFEL Injector Test Facility, to decide, based on performance and reliability, what diagnostics for the SwissFEL will be implemented Based on competences of Diagnostics Section for other PSI accelerators Synergies with European XFEL developments (BPMs) 7

8 Beam Position Monitors Measure orbit in linac (avoid transverse wakefields) in undulator (overlap with photon beam) Measure energy in bunch compressor before dumps Use also for jitter studies position and energy feedback

9 Beam Position Monitors Distribution BPMs TD TD 1 BPM per quadrupole in linac sections To optimize for beam based alignment, place BPMs close to quadrupoles Additional BPMs: 10 BPMs 6 BPMs Energy measurement in bunch compressors in BC Diagnostic sections Model verification in FODO sections of the linacs Alignment into the undulators 6 BPMs in DIAG 20 BPMs = 4 BPMs for matching + 16 BPMs in 8 FODO cells 6 BPMs in BC 11 BP = 4 B for mat + 7 B in 3.5 FO 9

10 Beam Position Monitors Specifications Injector Linac Undulator Charge Bunch-to-bunch fluctuations (RMS pc pc 3 µm 1 µm Temperature drift 3 µm / K 1 µm / K Beam pipe diameter 38 mm 16 mm 8 mm Measurement range Orbit feedback convergence range ± 500 µm (< 20 pc: ± 5 mm) ± 19 mm ± 8 mm ± 4 mm Integral nonlinearity 2% 1% Bunch spacing 2.5 ms 50 ns Bunch-to-bunch crosstalk < noise x-y crosstalk < 1% 10

11 Beam Position Monitors Cavity BPMs for the SwissFEL Linac & Undulator Cavity BPMs designed in collaboration with the European XFEL Prototype for FLASH Boris Keil, D. Lipka 11

12 Beam Position Monitors Electronics RF frontend ADC, digital back end Feedback output: RocketIO EPICS readout via on-board CPU 34!5+6+#"(7# 89:+# FE!"8G/!H!I9*(+# 305 nm rms 1015 D X (n) (!m) D time (min) G. Marinkovic, M. Stadler 12

13 Beam Position Monitors Roadmap SwissFEL Injector Test Facility Resonant stripline BPMs installed Cavity BPMs will be installed next week for testing purposes SwissFEL Cavity BPMs and electronics will use an adapted European XFEL design Cavity prototype installed at the SLS linac is working Test of resolution to be performed at the SwissFEL Injector Test Facility 13

14 Profile Monitors Usage Matching to design optics Measure transverse phase space (phase space density, emittance) Overlap electron beam with seed laser / laser heater With transverse deflecting structure: measure timeresolved parameters Bunch length Slice emittance In dispersive regions Measure energy profile Project the 6-dimensional phase space on 1 or 2 dimensions Reconstruct the phase space by numerical methods

15 Profile Monitors Distribution Profile Monitors M TD M R ES TD FODO R&M M M M ES M M M M M M M M MM ES Monitors for dedicated measurements OTR M Matching ES Scintillator Energy Spectrum crystals R Reference (for Energy Spectrum) PS Wire Emittance scanners Measurement with Phase Scan FODO Slice Emittance Measurement in FODO Cells On-line monitors Synchrotron light monitors Monitors before beam dumps ES 15

16 Profile Monitors Scintillators, OTR Screens & Wire Scanners Alignment hole and calibration scale Wire scanner Fluorescent crystal (Ce:LuAG) OTR screen (Al-coated Si wafer) RF shield High Energy Screen Low Energy Screen F. Piffaretti 16

17 Profile Monitors Optics for Screen Readout OTR screen / scintillator is at an angle of 45º to the optical axis For overview camera (1:5.3 demagnification) Use Scheimpflug criterion to correct image plane orientation Commercial lens: PC Nikkor 85 mm f/2.8 Projected pixel size: 23 µm For 1:1 imaging Perspective control lens is not available commercially Only central part (~1 2 mm) of the screen can be imaged within depth of field Micro Nikkor 200 mm f/4 17

18 Resolution of the Two Nikkor Lenses Using ISO test image Contrast Micro Nikkor 200 mm PC Micro Nikkor 85 mm Analysis using the code sfrmat2 (P. Burns) Limiting resolution (according to ISO 12233): PC Nikkor 85 mm f/2.8, imaging 1: lp/mm Micro Nikkor 200 mm f/4, imaging 1: lp/mm Results achieved with uniform incoherent white light Spatial frequency [lp/mm] 18

19 Profile Monitors Sensors Room-temperature CCDs Sony ICX274AL QE = 22% Readout noise: 35 LSB / px Pixel size: 4.4 µm Cooled CCDs for 10 pc bunches Sony ICX285AL QE = 50 % Readout noise: 4 e rms / px Pixel size: 6.45 µm CMOS detector for 70 ns bunch spacing Texas Instruments MT9M413 QE = 20% Readout noise: 41 e rms / px Pixel size: 12 µm 19

20 Profile Monitors Coherent Optical Transition Radiation COTR has a Gaussian frequency distribution: 10 5 Single Sided Power Spectrum of y(t) Schematic Plot Y(f) Frequency (Hz) x Unfortunately, the simulation of this effect depends on the macroparticle charge No simulation has been performed to predict this for the SwissFEL We will gather experience at the SwissFEL Injector Test Facility Possibilities to mitigate COTR Shorter wavelength ( nm) Laser heater 20

21 Profile Monitors Developments Optical design for a high resolution setup for a broad wavelength range J. Neubert 21

22 Profile Monitors Roadmap Installation of screen monitors in the SwissFEL Injector Test Facility Development of high-resolution screen monitors for a wide wavelength range ongoing Integration of sensitive and fast detectors into the control system Coherent optical transition radiation may be emitted by compressed bunches If the cutoff frequency is below near UV, we can use mirror optics If the entire OTR is coherent, we will use wire scanner Only one-dimensional profiles can be measured No measurement of slice emittance 22

23 Longitudinal Diagnostics Distribution Longitudinal Diagnostics TD BPM Screen SR Camera EO TD BPM Screen SR Camera BAM FIR (CSR) BAM FIR (CSR) Screen Screen Feedback Feedback 23

24 Longitudinal Diagnostics Integral measurements Bunch arrival monitor Dual pickup Button for 200 pc operation Waveguide for 10 pc operation Resolution goal: < 10 fs rms but wa Electro-optical modulator *"+B'E)0#+C,!"#$"%&' Pickup Measure arrival time jitter before BC Measure energy by determining passage time through bunch compressor!-%2,12#67&89 σ δ = c σ t R Measure arrival time at undulators for seeding and user experiments V. Arsov 24

25 Bunch Arrival Time Monitors OMO laser pulses mod. EOM pick-up sig. - misalignment betw. laser pulses and pick-up signal causes pulse amplitude modulation - opt. delay line pos. indicates pulse misalignment (tune until AM=0) FO RX : pickup voltage laser pulse modulation: unmodulated (calibration) error bunch too early bunch in time error bunch too late time optical master oscillator fiber distribution phase stabilized FO links BAM opt. front-end (in tunnel) DCF/stab. pol. ctrl. Δτ pos. adj. EDFA readout electronics Δτ pulse shaping clock gen. FO RX FO RX FO links pick-up sig. EOM1 (coarse) att. limiter EOM1 (fine) Δτ Rasmus Ischebeck Stephan Hunziker

26 Synchronized Elements Photocathode laser RF accelerating cavities Transverse deflecting structures EO bunch length diagnostics Seed lasers Experiments Master Oscillator Timing Distribution SYNC-signal RF-signal RF-signal RF-signal RF-signal kly 1 kly 2 kly 3 kly 4 SYNC-signal RF-signal RF-signal RF-signal RF-signal kly 5 kly 15 kly 25 kly 31 SYNC-signal SYNC-signal SYNC-signal SYNC-signal SYNC-signal diagn. 1 diagn. 2 diagn. 3 seed laser diagn. 4 pump-probe laser gun laser RF-gun / injector 1 RF-gun / injector 2 booster linac 3 rd harm. structure bunch compression 1 / 2 collimation / diagnostics Main LINAC collimation diagnostics switchyard, beam distribution undulator sections beam dumps towards beam lines multiple experimental stations ~ 1.0 km Rasmus Ischebeck Volker Schlott

27 Optical Master Oscillator for the SwissFEL Mode-locked solid state laser Model OneFive Origami f 0 =900MHz int. timing jitter (700 Hz..10 MHz): 15 fs (1 khz..10 MHz): 11 fs power supply and controller noise 30cm shot/rx noise lim. (low P opt ) Rasmus Ischebeck Stephan Hunziker

28 Optical Fiber Link Stabilization Scheme laser master oscillator (mode-locked Er-fiber laser) low noise microwave oscillator isolator phase noise measurement 50:50 coupler piezo controlled fiber stretcher controller piezo driver SMF link (1-5 km) output coupler Faraday Mirror photodetection 12 fs closed loop performance (0.1 Hz 5 khz) coarse RF stabilization ~ 20 fs ultimate stabilization < 1 fs fine optical cross-correlator direct stabilization of group velocity in fiber temperature effects and vibrations are compensated (fiber temp. coefficient ~ 5 x 10-6 m -1 ) Rasmus Ischebeck Volker Schlott

29 Longitudinal Diagnostics Integral measurements Peak current sensor Golay cell / pyroelectric detector Measure coherent synchrotron radiation after 4th bunch compressor magnet 29

30 Transverse Deflecting Structure Time-dependent electric field deflects the particles according to their arrival time Beam optics adjusted to image the deflection angle to a position on the screen Resolution is determined by the ratio of the streaked to the unstreaked vertical size: σ y,streaked = V E/e ωrf c z cos φ RF β y,tds β y,screen sin( Ψ y ) σ y,unstreaked = ε y β y,screen Rasmus Ischebeck: Diagnostics for the SwissFEL

31 Longitudinal Diagostics Profile Measurements Transverse Deflecting Structure After the gun Slice resolution: 200 fs After BC1 Slice resolution: 20 fs G. Orlandi, A. Falone 31

32 Longitudinal Diagnostics Transverse Deflecting Structure Parameters 250 MeV Expected parameters of the 250 MeV TDS: ω RF = 2π 3 GHz V = 4.5 MV E = 250 MeV σ z = 58 µm σ t = 193 fs β y,tds = 20 m β y,screen = 6.5m Ψ y = σ y = V E/e ωrf c = 650 µm Unstreaked beam size on screen: 73 µm for an emittance of 0.4 µm Slice resolution: 20 fs z cos φ RF β y,tdc β y,screen sin( Ψ y ) Rasmus Ischebeck: Diagnostics for the SwissFEL M. Pedrozzi 32

33 Longitudinal Profile Monitors Compact Setup EO set-up and detection system presently developed for SLS FEMTO and 250 MeV PSI XFEL Injector consists of Yb-doped Fiber Laser with oscillator & amplifier UHV compatible crystal holder, laser transfer and detection line electron beam moveable crystal holder inside UHV FL transport & EO signal detection Rasmus Ischebeck Bernd Steffen, Felix Müller

34 Longitudinal Profile Monitors Fiber Laser Ytterbium-doped fiber laser: Oscillator power: mw rep-rate: 50 MHz wavelength: 1030 nm spectral BW: 50 nm Amplifier power: mw rep-rate: MHz pulse energy: nj pulse length: fs (sigma) wavelength: 1030 nm spectral BW: 100 nm Rasmus Ischebeck Bernd Steffen, Felix Müller

35 Longitudinal Profile Monitors Expected Resolution Gun (τ = 10ps / τ rise = 7 MeV) In front of BC-1 (τ = 250 MeV) Behind BC-1 (τ = 195fs 250 MeV) EO-crystal: 5 mm GaP, Laser pulse: 20 fs (initial) chirped to 5 ps EO-crystal: 2 mm GaP, Laser pulse: 20 fs (initial) chirped to 5 ps EO-crystal: 0.5 mm GaP, Laser pulse: 20 fs (initial) chirped to 0.5 ps measurement of longitudinal electron beam profiles in front of and behind the bunch compressor provides peak current and compression ratio additional information to compression monitor using CSR EO detection provides non-destructive, single-shot bunch length information redundant to TDS bunch length measurement but allows online monitoring and (long term) stability studies Rasmus Ischebeck Bernd Steffen, Felix Müller

36 Longitudinal Diagnostics Profile measurements Martin Puplett Interferometer Goal: provide a way to measure bunch length after final compression Measuring CSR after the 4th bend of the bunch compressor M. Rohrer 36

37 Longitudinal Diagnostics Roadmap Various systems will be tested at the SwissFEL Injector Test Facility Integrated measurements Beam position monitors in dispersive sections Bunch arrival monitors Peak current monitors Profile measurements Transverse deflecting structures Electro-optical monitor Martin-Puplett interferometer Concept for SwissFEL is depending on Experience with performance and reliability of these systems Specifications for measurement resolution at the different locations 37

38 Charge Measurements Monopole mode of Cavity BPMs Developing ICTs for < 1 pc noise floor (joint development with Bergoz Electronics)

39 Photon Diagnostics Beam orbit Alignment of undulator modules Photon diagnostics: Pulse energy Position Timing relative to laser Pulse length Spectrum Post-undulator e-diagnostics: Energy Energy spread Slice energy spread PhD is working in Diagnostics Group on a residual gas XBPM Investigating the possibility to install a TDS behind the undulator DESY

40 Photon Diagnostics Concept differential pump THz streak camera acoustic and thermal sensor spectrometer to experiment gas detector 16 electron time of flight detectors scintillating crystal measured quantities pulse energy position pulse energy position polarization pulse length arrival time pulse energy position transverse distribution spectrum Text Rasmus Ischebeck

41 SwissFEL Diagnostics Layout Summary Developing a variety of systems to be used at the SwissFEL Injector Test Facility: Beam position monitors Profile monitors Longitudinal diagnostics Multiple approaches, partially redundant Will evolve into a system for the SwissFEL Implementation decisions will depend on Refined requirements Performance at the SwissFEL Injector Test Facility Reliability at the SwissFEL Injector Test Facility Cost Transform experiments into diagnostics 41