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Booster bpm’s

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.

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Booster bpm’s

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  1. Booster bpm’s Jim Crisp 3/29/06

  2. 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)

  3. 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

  4. 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

  5. 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)

  6. 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

  7. rf modules MI rf module, similar for booster (MI 0.48db/mm Hor, 0.42db/mm Ver)

  8. 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)

  9. 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

  10. Cross section • Proposed design • Type N feed through on one end • Short other end • 16” long plates

  11. 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

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