RF Control for the DESY UV-FEL Stefan Simrock DESY DESY CASA Seminar 2/6/04 Stefan Simrock
• DESY UV-FEL • Configuration of the RF Systems • Requirements for RF Control • Design of the LLRF • Issues for the European X-FEL • Outlook DESY CASA Seminar 2/6/04 Stefan Simrock
Status of beamline installations RF gun M2 M3 M1 M4 M5 M6 M7 undulator s bunch bunch FEL collimator bypass compressor Laser compressor experimenta 1000 MeV l area 4 MeV 150 MeV 450 MeV 250 m 21 Jan. 2004 J. Rossbach: TTF2 Status Report 3
General LLRF Requirements • Set and maintain accelerating fields during TTF II operation as • UV FEL user facility • Tesla Test Facility • Cavities to be controlled: • RF Gun (nc) • 3rd harmonic cavity (3.9 GHz) • Vector-sum of cryomodule 1 • Vector-sum of cryomodules 2+3 • Vector-sum of cryomodules 4,5,6,(7) • S-Band cavity (nc) at 2.856 GHz • Provide stable phase reference for Laser, and diagnostics DESY CASA Seminar 2/6/04 Stefan Simrock
Electron gun for minimum emittance: PITZ PITZ gun installed into TTF Jan 2004 21 Jan. 2004 J. Rossbach: TTF2 Status Report 4
TTF2 RF GUNAT PITZ Jean-Paul Carneiro Behavior of the TTF2 RF with long pulses and high repetition rates.
TTF 2 Laser Upgrade • Together with Max-Born-Institute, Berlin (I. Will et al.) • Upgrade has been tested at PITZ Note: longitudinal flat Diode-pumped profile by pulse Pulse shaper stacker only Nd:YLF oscillator (T = 5%) diode-pumped AOM EOM AOM Nd:YLF preamplifier f round trip = 27 MHz Faraday pulse pump pump pump pump diode diode diode diode picker Pulse micro = 16 µ J micro = 200 µ J E E Stacker P = 16 W P = 200 W 20 ps flat-top fourth pulse 4 ps edges harm. fast fast picker current current control control E micro = 30 µ J pump pump pump pump diode diode diode diode E burst = 24 mJ UV (262 nm) 2-stage diode-pumped 2-stage flashlamp-pumped Nd:YLF amplifier Nd:YLF booster amplifier shot-to-shot optimizer 21 Jan. 2004 J. Rossbach: TTF2 Status Report 5
Transverse Emittance Measurement @ PITZ - 1. 7 1. 5 21 Jan. 2004 J. Rossbach: TTF2 Status Report 8
Fine Tuning of Laser Parameters ( measured in UV ) transverse profile ( D=1.2 mm ) σ 0.55 0.02 mm x � � σ 0.61 0.02 mm y � � FWHM � 21 ps; rise/fall time � 7 ps Frank Stephan TESLA meeting, Zeuthen, Jan. 2004 21
General LLRF Requirements (Cont’d) • The LLRF System for the FEL user facility must be • Reliable • Operable • Reproducible • Maintainable • Well Understood • Meet (technical) performance goals • The LLRF System for the TESLA Test facility must • demonstrate high gradient operation at 35 MV/m - requires piezo tuners for Lorentz force compensation - requires operation close to klystron saturation - exception handling • Demonstrate of operation with electronics installed in tun- nel DESY CASA Seminar 2/6/04 Stefan Simrock
LLRF Requirements: Support by: ELHEP Group Warsaw University of Technology Institute Electronic System Team: About 20 people scientists, engineers and students (Ph.D. and M.Sc.) working at: Warsaw, CERN, DESY 21 Jan. 2004 J. Rossbach: TTF2 Status Report 10
Amplitude and Phase Stability • Typically requirements are • σ A /A < 10 -3 amplitude • σ φ < 0.3 deg. for phase (fast fluctuations) • Must distinguish correlated and uncorrelated errors, intra-pulse, inter-pulse, and long-term (thermal > minutes). Long term stability of better than 1 deg. is difficult to achieve. • Other requirements • ACC1: cav. 1-4 at 12.5 MV/m, cav. 5-8 at 20 MV/m phase of accelerating field -10.8 deg. • ACC39 at 14 MV/m at 183 deg. • S-Band cavity at 2856 MHz phase stability < 1 deg. • RF Gun operation without field probe. Rep. rate, pulse length and power must be variable. DESY CASA Seminar 2/6/04 Stefan Simrock
TTF2 linac RF-Gun M2 M3 M4 M5 M6 M7 M1 undulators collimator bypass 1 st bunch compressor 2 nd bunch compressor Laser (internally called BC2) (internally called BC3) bunch compressor (internally called BC2) 250 m
Magnetic chicane for longitudinal compression 21 Jan. 2004 J. Rossbach: TTF2 Status Report 30
Temporary beamline for seeding Beam dump 21 Jan. 2004 J. Rossbach: TTF2 Status Report 33
Longitudinal bunch shape measurements at TTF2 • Streak camera –FESCA 200 (Hamamatsu) • Transverse deflecting cavity –S-band travelling wave cavity from SLAC • Coherent radiation –Interferometer from RWTH Aachen • Electro-optical sampling 21 Jan. 2004 J. Rossbach: TTF2 Status Report 24
LOLA Shipment from SLAC to DESY • Vertically deflecting cavity for bunch length measurements at TTF2 • Built in the late 60ies by G. Loew et al. • SLAC contribution to TTF2 “Intra-Beam Streak Camera” RF RF 3.66 m 3.66 m ‘streak’ ‘streak’ V ( ( t t ) ) V σ y σ y e − − e S - -band band S β p β σ z σ p z transverse RF deflector transverse RF deflector ∆ ψ ψ y ∆ β c β y c 21 Jan. 2004 J. Rossbach: TTF2 Status Report 25
LOLA shipment LOLA installed 21 Jan. 2004 J. Rossbach: TTF2 Status Report 26
Electro-optical sampling at TTF1 • Ti:Saphire laser (15 fs) and ZnTe crystal • Electron bunch can be scanned by varying the delay of the laser • Polarization of the laser changes depending on the amplitude of the “beam fields“ Signal 21 Jan. 2004 J. Rossbach: TTF2 Status Report 29
Jan '04 Feb '04 Mar '04 Apr '04 May '04 Jun '04 Jul '04 Aug '04 Sep '04 Oct '04 Nov '04 Dec '04 Jan '05 Feb '05 Task Name 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 1 11 21 vacuum installation ACC1 string assembly ACC1 tunnel installation coupler conditioning (warm) cool down coupler conditioning (cold) cavity conditioning gun commissioning (nighttime) gun commissioning with beam injector commissioning incl. BC2 tunnel closed 4/21 beam through ACC1 final installation commssioning entire machine 9/11 beam through bypass into dump 9/27 beam through undulator into dum 12/10 first lasing (30 nm) 2 FEL saturation (30 nm) Major schedule for TTF2 installation and commissioning More detailed schedule (400 items) to be presented in WG3 by M. Körfer 21 Jan. 2004 J. Rossbach: TTF2 Status Report 35
Typical Parameters in a Pulsed Linac flat-top fill ampl. accelerating voltage Beam Loading incident power beam pulse ... time cavity phase Beam pulse pattern cavity detuning (micro and midi pulse structure) DESY JLAB, Nov. 2001 Stefan Simrock
Sources of Perturbations o Beam loading o Cavity dynamics - Beam current fluctuations - cavity filling - Pulsed beam transients - settling time of field - Multipacting and field emission - Excitation of HOMs o Cavity resonance frequency change - Excitation of other passband modes - thermal effects (power dependent) - Wake fields - Microphonics - Lorentz force detuning o Cavity drive signal - HV- Pulse flatness o Other - HV PS ripple - Response of feedback system - Phase noise from master oscillator - Interlock trips - Timing signal jitter - Thermal drifts (electronics, power - Mismatch in power distribution amplifiers, cables, power transmission system) DESY JLAB, Nov. 2001 Stefan Simrock
Pulsed Operation at High Gradients short pulse Cavity Gradients (First Cryomodule) Cavity Phases (First Cryomodule) 25 150 -22.5 MV/m 20 100 50 15 phase [deg.] E acc [MV/m] +140deg./ms 0 µ s flattop -100deg./ms 0 900 µ s flattop 10 −50 −100 5 −150 0 0 0.5 1 1.5 2 0 0.5 1 1.5 2 time [ms] time [ms] Phase (8 cavities) Gradient (8 cavities) DESY JLAB, Nov. 2001 Stefan Simrock
Measurement of Cavity Q L and Detuning 2 150 10 1 – - - - slope: 140 τ slope: d ϕ 130 - - - - - - 1 10 dt 120 110 field decay: ~ e -t/ τ phase [deg] log( E_acc ) 0 100 10 QL phase with respect to LO 90 ⇒ ∆ω = d ϕ τ = - - - - - - - - - - - 2 π ∆ f ⋅ 80 π ⋅ - - - - - - = −1 f 10 dt 70 rel. error < 1% rel. error < 2 Hz 60 −2 50 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0 200 400 600 800 1000 1200 1400 1600 1800 2000 time [us] time [us] Detuning Loaded Q DESY JLAB, Nov. 2001 Stefan Simrock
Lorentz Force Detuning Lorentz Force Detuning of D39 in Chechia 300 15 MV/m 20 MV/m 200 25 MV/m 30 MV/m 100 detuning [Hz] 0 flat-top −100 fill decay fill: 500 µ s −200 flat: 800 µ s −300 0 500 1000 1500 2000 time [ µ s] DESY JLAB, Nov. 2001 Stefan Simrock
Digital Control at the TTF vector master modulator klystron oscillator power transmission line 1.3 GHz ... Cavity 1 Cavity 8 Cavity 25 Cavity 32 8x 8x ...... ...... Im Re cryomodule 4 cryomodule 1 1.3GHz DAC DAC field probe 1.3 GHz LO LO LO LO + 250 kHz 250 kHz ... clock ADC ADC ADC ADC . . . . . . . . f = 1 MHz s ( ) ( ) ( ) a -b ( ) a -b a -b a -b a a b a b a b b 1 8 32 25 Σ vector-sum Re Im digital + + low pass filter Re Im Re Im Re Im feed DSP gain setpoint forward system table table table DESY JLAB, Nov. 2001 Stefan Simrock
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