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.................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 1 Fourier Series Pulse Compression Damping Ring Kicker: another Progress Report George Gollin University of Illinois at Urbana-Champaign Slide 2 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 2 The specs Dog bone (TESLA TDR) kicker specs: impulse: 100 G-m (3 MeV/c) 0.07 G-m (2 keV/c) residual (off) impulse: 0 0.07 G-m (2 keV/c) rise/fall time: < 20 ns Perhaps larger (but less precise) impulse at injection, smaller (but more precise) impulse at extraction will be desirable. Small ring kicker rise, fall times can be asymmetric: leading edge < 6 ns, trailing edge < 60 ns Slide 3 .................................... I PhysicsP I llinois 3 Fourier series pulse compression kicker Instead of a pulsed kicker, construct a kicking pulse from a sum of its Fourier components. Combine this with a pulse compression system to drive a small number of low-Q cavities. Illinois, Fermilab, Cornell are involved. Slide 4 .................................... I PhysicsP I llinois 4 Participants Univ. Illinois Joe Calvey Michael Davidsaver Justin Phillips George Gollin Mike Haney Jeremy Williams This project is part of the US university-based Linear Collider R&D effort (LCRD/UCLC) Cornell Gerry Dugan Joe Rogers Tug Arkan Euvgene Borissov Harry Carter Brian Chase David Finley Chris Jensen Timergali Khabiboulline George Krafczyk Shekhar Mishra Franois Ostiguy Ralph Pasquinelli Phillipe Piot John Reid Vladimir Shiltsev Nikolay Solyak Ding Sun Fermilab Slide 5 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 5 Fermilab/Illinois activities Initial studies: use Fermilab A0 photoinjector beam (16 MeV e - ) for studies: 1.concept and design studies of FSPC kicker 2.build a fast, simple strip line kicker 3.use the stripline kicker to study the timing/stability properties of the A0 beam 4.build a single-module pulse compression kicker 5.study its behavior at A0 6.perform more detailed studies in a higher energy, low emittance beam (ATF??) Slide 6 .................................... I PhysicsP I llinois 6 Right now: simulations and RF engineering discussions Slide 7 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 7 and writing it up so it is clearly described Slide 8 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 8 and building a stripline kicker. Start with a simple kicker whose properties are calculable and can be measured independently of its effects on the A0 electron beam. Most important: how well can we measure a devices amplitude and timing stability with the A0 beam? Fermilab just finished building this. Install next month (April, 2005). Slide 9 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 9 Test it in the FNAL A0 photoinjector beam 16 MeV electron beam, good spot size, emittance. EOI submitted to A0 group last spring. Space in beamline will be available ~January 2005 Slide 10 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 10 Performance modeling studies Functional units in the system, downstream to upstream: RF cavity, Q = 25 Waveguide RF amplifier Arbitrary function generator Modeling strategy is to study the consequences of: drifts in parameter values (e.g. Q of RF cavity) noise in RF power amplifier output signal nonlinearities: harmonic and intermodulation distortion Slide 11 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 11 Parameters in our studies ParameterSymbolValue Main linac bunch frequency f L ( L 2 f L ) 3 MHz Damping ring bunch frequency f DR ( DR 2 f DR ) 180 MHz RF structure center frequency f RF ( RF 2 f RF ) 1845 MHz RF structure QQ25 Waveguide cutoff frequencyf cutoff 1300 MHz Desired on field integralA(0)(100 .07) Gauss-meters Desired off field integralA(t)A(t)(0 .07) Gauss-meters f DR / f L N60 f RF / f DR 10.25 f RF / f L NN 615 Bunch length B or B 6 mm ~ 20 ps KarmaImpeccable Nothing has been optimized yet! Slide 12 .................................... I PhysicsP I llinois 12 RF cavity Q = 25 center frequency 1845 MHz Slide 13 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 13 RF cavity Q error Kick error caused by deviations in Q for the center, head, and tail of the kicked and first two unkicked bunches. Full vertical scale corresponds to 0.07 Gauss-meters (2.1 keV/c). Slide 14 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 14 RF cavity center-frequency error Kick error as a function of cavity center frequency error for kicked, first unkicked, and second unkicked bunches. Slide 15 .................................... I PhysicsP I llinois 15 Waveguide: 80 meters long for the time being 80 meters long 1300 MHz cutoff Slide 16 .................................... I PhysicsP I llinois 16 Waveguide compresses pulse Pulse compression! Maximum amplitudes: entering~0.016 exiting ~0.1 Slide 17 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 17 Waveguide length error Two contributions to problems: 1.change in flight time down the waveguide 2.relative phases of Fourier components are misaligned #1 dominates. Differences between delivered kicks and an ideal impulse for waveguides that are 5 mm, 10 mm, 15 mm, 20 mm, and 25 mm too long. The peaks in the kicks have been shifted in time to align with the peak in the ideal impulse that is centered at t = 0. In addition, the delivered kicks have been rescaled to have the same magnitude as the ideal impulse. Slide 18 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 18 Waveguide cutoff frequency error Correcting for time misalignment and change in overall pulse size helps considerably. Effects of cutoff frequency errors. The curves represent the difference between delivered and ideal impulses as functions of time after aligning the time of the peaks and rescaling the peak amplitudes. Full scale in the plot is 100 ps. Nominal f cutoff is 1.3 GHz. Errors in cutoff frequency for individual curves are indicated on the plot. Slide 19 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 19 Amplifier gain error For now, look at a linearly increasing error as a function of frequency Effects of an amplifier gain error that grows linearly with frequency. The curves represent the difference between delivered and ideal impulses as functions of time. The time region in the plot is centered on the arrival time of the kicked bunch. Slide 20 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 20 Amplifier phase error Use a linearly increasing error as a function of frequency here too. Effects of an amplifier phase error that grows linearly with frequency. The curves represent the difference between delivered and ideal impulses as functions of time. The time region in the plot is centered on the arrival time of the kicked bunch. Full (horizontal) scale is 100 ps. The impulse functions have been shifted in time to align the kicking peaks at t = 0 and rescaled to agree in amplitude with the nominal kick Slide 21 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 21 Amplifier noise Model as flat in frequency, from 300 MHz to 6 GHz for now. Cavity is insensitive to frequencies far from center frequency 10 -4 GHz -1/2 Slide 22 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 22 amplifier noise Generate in 300 kHz frequency bins, random phases. More work is needed Slide 23 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 23 Nonlinear effects: harmonic and intermodulation distortion Initial harmonic distortion studies are done. Now working on intermodulation distortion simulation. Slide 24 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 24 Harmonic distortion Slide 25 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 25 Intermodulation distortion Intermodulation distortion: third-order effects are most likely to be the most important. Under way Slide 26 .................................... I PhysicsP I llinois 26 Building a stripline kicker Slide 27 .................................... I PhysicsP I llinois 27 Looking inside the kicker Slide 28 .................................... I PhysicsP I llinois 28 Baking the kicker electrodes Kicker is now assembled, vacuum tested, high-potted. Installation in A0: mid-April. Slide 29 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 29 Measuring electrode positions Slide 30 .................................... I PhysicsP I llinois 30 Machineable ceramic supports Slide 31 .................................... I PhysicsP I llinois 31 UIUC students in A0 Slide 32 .................................... I PhysicsP I llinois 32 No data yet but weve started working on analysis tools. Our plan is to generate simple Monte Carlo data to test tools before we have real data. We bought a new computer: Slide 33 .................................... I PhysicsP I llinois 33 We started looking at (old) straight-through A0 data Slide 34 .................................... I PhysicsP I llinois 34 HV pulsers Start with a Fermilab linac chopper HV pulser: 750 V. Chris Jensen and colleagues just finished it. Slide 35 .................................... I PhysicsP I llinois 35 FID pulser Gerry Dugan is ordering a FID pulser: Maximum output into 50 Ohm: 1 kV Amplitude stability in burst mode 0.3 0.5% Pre- and after-pulses 0.3 0.5% Rise time 10-90% of amplitude 0.6 0.7 ns Pulse duration at 90% of Umax 2 2.5 ns Fall time 90-10% of amplitude 1 1.5 ns Maximum PRF in burst mode 3 MHz Maximum PRF in continuous mode 15 kHz Timing jitter, both output pulses vs. trigger 20 ps, max Power 110/220VAC, 50/60 Hz Slide 36 .................................... I PhysicsP I llinois George Gollin, Damping ring kicker report, March 9, 2005 36 UIUC/FNAL, longer term plans Design, then build one module using existing components. Fermilab RF group is involved UIUC HEP electronics design groups chief is too. So were making progress. Goals: install strip line kicker in A0 during April, 2005 understand A0 by summer, 2005 investigate small pulse compression system during summer, 2005