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Nano beams in the ATF extraction line

This project aims to prove that nanometer-sized beams can be kept in collision by studying beam stability and designing a BPM with 1 nanometer resolution. It also explores stabilization methods for the ATF extraction line beam.

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Nano beams in the ATF extraction line

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  1. Nano beams in the ATF extraction line Linear collider challenges: Energy Emittance source Stability ATF – well suited for RD on emittance and stability Marc Ross

  2. Goal – ATF Nano-BPM project • Prove that nanometer sized beams can be kept in collision • short time scales – vibration • long time scales – thermal drift • Steps: • Measure with nanometer resolution • design and test a BPM that has ~ 1 nanometer resolution • Study beam stability • study the stability of the ATF extraction line beam • Stabilize with active movers/sensors • Stabilize the magnets that focus the beam (they probably need it) • Stabilize the BPM itself

  3. Multi-bunch feedback – final step • There will still be some instability from the ring / extraction kicker • It may be possible to stabilize the trajectory within a long pulse train • need good – multibunch – BPM’s • ‘FONT’ experiment at NLCTA 4. Use a long extracted pulse and stabilize the back section of the train FONT = Feedback On Nanosecond Timescales

  4. IP fast feedback scheme JLC/

  5. FONT setup in NLCTA • Feedback on the back 2/3 of a 170 ns train • 60 ns latency

  6. 1) Nano-BPM test – ATF extraction line • Mechanically connect several BPM’s (4 – 5?) • Must control cavity position and angle • Electronics similar to tiltmeter – optimized for best possible resolution • ATF ext line (BINP) – 250 nm • FFTB (Shintake) – 25 nm • Joe Frisch, Steve Smith, T. Shintake

  7. Cavity properties: For 1010 Electrons, single bunch (assumed short compared to C-band). Assume cavity time constant of 100 nanoseconds (1.6MHz bandwidth) (guess) Assume beta >> 1 for cavity. (All power is coupled out). Thermal noise energy is kT or 4x10-21 Thermal noise position (ideal) = 0.4nm Note that deposited energy goes as offset^2 and as beam charge ^2. Signal: A 1nm offset deposits 2.4x10-20 J in the cavity. Output power for 1 nm offset is 2.4x10-13 Watt. Output power for 1 cm offset (cavity aperture?) is ~25 Watts (maximum single bunch) Output power for 10 bunch train can be 2500 Watts! (Need to terminate for multi-bunch operation) C-band BPM limiting resolution (Vogel/BINP)

  8. Thermal noise = -168dBm/Hz. Assume signal loss before amplifier = 3dB. 1.2x10-13 Watt = -99dBm Signal power after amplifier for 1nm offset = -79 dBm Dynamic range at amplifier output = 91 dB, or ~35,000:1 position, or 25 microns. Assume maximum signal into mixer (13dBm LO) = ~8dBm. (Joe thinks this should be ~0 dBm) Full range (1 dB compression): 8 dBm into mixer (Note: for good linearity, probably want –20 dBm into mixer, or ~1 micron range) Mixer conversion loss ~8dB. Maximum output = 0 dBm Front end broad band amplifier – 20 dB Assume noise figure = 3dB (better available) = -165dBm/Hz input noise. Front end amplifier bandwidth = 10GHz -> -65dBm noise input. Front end gain = 20dB -> -45 dBm noise power output (OK). IF amplifier – 30 dB Final bandwidth = 1.6 MHz. Noise in band power after amplifier = -83 dBm Electronics, Noise and Dynamic range

  9. Equipment • Cavities - assume existing C band BPMs • Filters: Approximately Q=10 to help limiter. May not need if fast limiter is available. • Limiters: Available from Advanced Control. 100W peak input, Limit to about 15dBm output. Try ACLM-4700F feedback limiter 0.8dB loss, 100W max pulse input, 13.5dBm max output. Unknown speed. Also see ACLM-47000 0.7dB loss, 100W input, 20dBm max output. • Amplifier: Available from Hittite with ~3dB noise figure. Stage to get ~30dB Gain. NOTE: need to find an amplifier which can survive the 15dBm output from the limiter. Hittite parts seem to only handle 5dBm. (Maybe OK pulsed?) Amplifiers available from Miteq ($$$?) with 0.8dB noise figure and 20dBm allowable input power: JS2-02000800-08-0A (for future upgrade). • Mixer: Use Hittite GaAs parts - likely to be radiation resistant. • IF amplifier. 30dB gain, 0.1-50 MHz. Various options from Mini Circuits or Analog modules. Need Noise Figure << 10dB. > 2V p-p swing.

  10. Support electronic equipment / software • Digitizer: Use spare SIS (VME) units from 8-pack LLRF system. Each is 100Ms/s, 12 bit, +/-1 V (?) input signal. • C-band source: Use existing ATF synthesizer. Does not need to be locked. • C-band distribution amplifier. Need to drive 8 x 13dBm references. Approximately 25dBm output (including losses). Use existing ZVE-8G amplifier (purchased for tiltmeter • work). • C-band distribution splitter: 1:8 splitter. Probably exists, otherwise mini-circuits. • Control System: Use existing 68040 controller and existing crate. Linda thinks it is easy to interface this to Matlab on a PC for data analysis. • Matlab software: Use modified version of tiltmeter software. Digitizes decaying signal from cavity BPMs and reference signal, with stripline BPM as time reference. Does not require phase locked reference, or good frequency match between cavities.

  11. Mechanical • X/Y Tilt Stage: Check Newport U400 mirror mounts (~$300 each). May be strong enough to move cavity. • X/Y Tilt stage drive: Use picomotors (~$450/channel motor + ~300/channel for driver), or steppers (??/channel). Steppers would provide position read back. • X/Y translation stage: Use existing stages.

  12. Mechanics • Mechanical Issues • The ATF beam has a position jitter of ~1 micron. In order to demonstrate 1nm bpm resolution, we need to do line fits between 3 (or more) bpms. This requires a position stability for these bpms of <1nm for several pulses (10-30 seconds). • For bpms spaced by meters, the ground motion and vibration will be substantially larger than this, probably hundreds of nanometers. For the final measurement the bpms must be mounted from a common reference block. That reference block must be on supports which are sufficiently soft to not transmit vibrations which can excite internal modes in the block, probably a 10Hz mechanical support frequency is reasonable. • Thermal expansion of metals is ~2x10-5/C. For a 30cm scale length, this requires temperature stability of 2x10-4C in a measurement time (~1 minute). With insulation and in the controlled ATF environment this may be possible. Use if Invar or a similar low expansion mounting frame may provide a factor of 10 relaxation in this requirement. (Not more, since it is impractical to make to cavities or cavity mounts out of Invar. • If the temperature requirements cannot be met, an interferometer (or "queensgate" style capacitive system) will need to be used relative to an Invar or Zerodur reference block.

  13. Plan 2) Study beam stability – pulse to pulse and long term – using nanoBPM Assume that the ATF beam is not stable at the nanometer level and cannot be made stable 3) Use the FONT feedback on a long multi-bunch train (coll with UK group) requires: • increasing the bandwidth of the nano BPM to ~20 MHz (from 1.5 MHz) • Extra long trains – lengthen the train by extracting 3 trains that were injected in a sequence • Installation of the FONT feedback kicker and sampler • Can we stabilize the back section to the nanometer level?

  14. SLAC- KEK/ATF team:Damping rings and Final focus Karl Bane Joe Frisch Keith Jobe Doug McCormick Bobby McKee Janice Nelson Tonee Smith Jim Turner Mark Woodley P. Karataev

  15. Noise output = -91dBm in 1.6MHz bandwidth. Low pass filter for ~50MHz bandwidth (anti alias) assume loss 2dB. Input to IF amplifier -10dBm Maximum signal, -93dBm noise signal. Maximum signal 20dBm (2 V Pk - Pk) Digitizer: 12 bit, 100Ms/s 10 samples during decay time. Dynamic range = 13,000:1 Input level +/- 1 V peak. Electronics - digitizer

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