2.8 GHz cavity design

1
2.8 GHz cavity design

• Robustness vs. high sensitivity and compactness
  optimum
• Tuning to 2876 MHz
• Reduced Q to keep the decay time small
• Use nanoBPM analysis keep similar processed
  signal properties
• Almost the same sensitivity as for BPMs in
  nanoBPM experiment at ATF beam, expect a
  resolution lt 100 nm in the ESA

2
Prototype Al model

• Planning to do cold tests before producing a
  vacuum prototype, a model is being produced in
  UCL workshop
• Going to introduce an asymmetry (one slot will be
  off axis), also reduced the waveguide length in
  order to see the monopole mode coupling this
  should allow us to set reasonable tolerances,
  benchmark the simulation code, and choose a
  reasonable waveguide length

3
Prototype simulation

• Tests to predict the properties of the BPM
  prototype (50 mm waveguide length)Calculation
  with the slot offset by 0.4 mm
• mode 4 f 1.8967e9 A 6.246 R/Q 229 115
  Ohm Q0 4980
• mode 6 f 2.8759e9 A 4450 R/Q 0.71/2 0.36
  Ohm Q0 5220
• Equivalent offset 25 um -gt 12 um for a 0.2 mm
  slot offset

4
Some comments

• Al prototype expected mid/end September (delayed
  and delayed)
• Design of the vacuum prototype by end September
• Equipment for the tests of the prototype is set
  up (BPM test bench, UCL) or on its way to the lab
  (NVA, RHUL)
• 2 (think 3) months to produce a vacuum prototype
  still possible to do before the next ESA run
• Should start ordering components for the
  electronics and feedthroughs to avoid delays

5
Electronics

• Basically, same stuff we are using already
• Add a switch for the calibration tone
• Use an electronic attenuator to save time on the
  accesses
• 10 BW front-end filter to reduce the first
  monopole kick (have to check for the second
  monopole)

6
Electronics simulation
TM010
TM110 (20 nm signal) Noise
Noise (time and frequency domain)