# Presentation: 828581

## Booster bpm’s	

- Jim Crisp
- 3/29/06

## Plate width and linearity

- with the response linearized along the axis
- 	60 and 20 degree plates become nonlinear in the corners
- 	40 degree plates have the least distortion
- 	calculate 0.5db/mm    (booster bpm’s are 0.52db/mm)

## 50 or 25 ohms

- The even mode impedance is most important
- 50 ohm 40 degree plates won’t fit in the proposed magnet   (60 degree plates worse)
- 3.916” plate ID for 5.465” bpm OD
- 25 ohm, 40 degree plates will fit
- 4.5” plate ID    5.228” bpm OD  with 1/8” wall

## Equivalent bpm

- Current booster bpm’s
- 4.625” plate ID, 60 degrees wide, 6” long, 6” bpm OD,
- 52.9 ohms even,  44.2ohms odd mode
- Vplate/Ibeam 1.4 ohms at 53MHz
- 0.52db/mm 30-50MHz and 0.48db/mm at 200MHz
- Proposed bpm
- 4.5” plate ID,  40 degrees wide, 16” long
- Ideal (60/40)(50/25)6” = 18”   correction magnet 17.5” flange to flange
- 25 ohms even 24.2 ohms odd
- Vplate/Ibeam = 1.25 ohms at 53MHz  (about 10% less)
- 0.50db/mm

## Beam intensity range

- 25 ohms,  40 degrees wide,  16” long
- (Correction magnet is 17.5” flange to flange)
- Rf module dynamic range -23.5 to +18.5dbm
- -35 to +27dbm for AM to PM rf module
- +1.5db for 100ft RG8 cable
- +/-10db for +/-20mm position
- working range of beam intensity
- 8.4 to 1060e10
- (about the same as now)

## Frequency response

- Peak at wl/c = pi/2     (plates 1/4 wavelength long)
- 185MHz for 16” and 492MHz for 6” plates
- Same response for terminated, open, or shorted stripline
- 200MHz   linac beam    5.00/2.75 ohms    (present/proposed)
- 37.9MHz  at 400MeV    1.06/0.93 ohms
- 52.8MHz  at 8GeV        1.40/1.20 ohms

- Use 50ohms at bpm output to terminate stripline

## rf modules

- (MI 0.48db/mm Hor, 0.42db/mm Ver)

- MI rf module, similar for booster

## Wall thickness and magnetic fields

- magnetic fields will be attenuated and delayed inside bpm
- round pipe acts like low pass filter    (approximate)
- n = 2 for dipole    (4 for quadrupole etc)
- ρ = 9.0e-7 ohm-m for stainless steel
- R = 3” radius
- t = 1/8” wall thickness
- f ~ 942Hz      t ~ 170usec
- The 4 plates will also distort a changing magnetic field above this frequency
- Frequency where 1/8” = skin depth
- f = 22.6KHz
- What are the frequency components of the correction fields?
- (30-50MHz external magnetic fields will never reach the plates)

## Measured fields in pipe

- 1/8” wall 2” ID Aluminum pipe
- Solid is calculated using Mafia – Ostiguy
- Red curve from simple formula
- Points are measured with hall probe

## Cross section

- Proposed design
- Type N feed through on one end
- Short other end
- 16” long plates

## A few details

- Proj 22  Task 1.02.03.01
- deliver nearly the same signal to the rf modules
- Lowest intensity 1 turn of 30mA or about 40e10
- 24 long and 24 short locations  (use same bpm)  60 magnets will be made
- Need survey fiducials to measure bpm location in tunnel
- Use same fiducials on bpm test stand
- survey position and rotation tolerances?
- Allowable wall thickness / bandwidth of correction fields
- Rise times of 2 msec
- Eddy current heating may be a problem (correctors ramped at 15Hz)
- radiation exposure over the expected life time?
- Few locations measured at 20KRad/month  (MRad/lifetime)
- Vacuum acceptance criteria
- Flanges should be angled to match bend magnet
- Assembly may require a bellows
- Bpm should be made very reliable and thoroughly tested before installation, requires replacing magnet to change
- May request cable strain relief bracket on magnet
- Prototype bpm for test June 2006
- First 24 required February – April 2007
- Installation June 2007