Nano beams in the ATF extraction line

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 BPMs
• 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 BPMs (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
C-band BPM limiting resolution (Vogel/BINP)

• 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 gtgt 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 offset2 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)

8
Electronics, Noise and Dynamic range

• 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
  35,0001 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 -gt -65dBm
  noise input.
• Front end gain 20dB -gt -45 dBm noise power
  output (OK).
• IF amplifier 30 dB
• Final bandwidth 1.6 MHz. Noise in band power
  after amplifier -83 dBm

9
Equipment

• Cavities - assume existing C band BPMs
• Filters Approximately Q10 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 ltlt 10dB. gt 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 18 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 lt1nm 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 teamDamping 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
Electronics - digitizer

• 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 13,0001
• Input level /- 1 V peak.