1 KEK Cavity BPM Hitoshi Hayano Development of Cavity BPM for Q-magnet attachment, Aiming; compact design, 0.2µm resolution, BPM center error (between electrical and mechanical) <10µm, Simple & cheap electronics design Vide-meeting 3/24/2005 ILC-Asia

2 Design concept Use dipole mode excitation in a pill-box cavity principle Concept of Q-mag attachment

3 Measurement of center difference between electrical and mechanical Alignment and scanning device Cavity cold Model Excitation antenna Cold model cavity on the measuring device アンテナ スキャン結果

4 Proto-type of Cavity BPM pickup Feature ： frequency ： 6.55GHz(TM110) magnetic coupling by 4 slots into resonant wave-guide 4-port pickup by antenna(electrical field) (additional common-mode rejection by external combiner ） reference cavity attached: 6.55GHz(TM010)

5 Detail of inner structure (low-power model) same as hot-model

6 Electronics for position detection (Analog signal process type) Frequency converter 6.5GHz -> 714MHz Phase detector 714MHz burst -> pulse signal Charge ADC

7 3 BPM setup for resolution measurement in ATF L1L1 L2L2 x1x1 x2x2 x3x3 X 2 esti =(L 2 x 1 + L 1 x 3 )/(L 1 +L 2 ) X 2 esti x2x2 X’ Y’ Y’ =(x 2 - x 2 esti )/sqrt(2) 45deg axis rotation, and projection to Y’ Sigma;  Y’ =sqrt(  x2 2 + (L 2 /(L 1 +L 2 )) 2  x1 2 + (L 1 /(L 1 +L 2 )) 2  x3 2 )/sqrt(2) If L 1 =L 2,  x1 =  x2 =  x3 =  x ;  Y’ = sqrt(3)/2  x beam resolution Measured spread (45deg projection) Achieved resolution ： 0.07 μ ｍ

8 Development Status Developed Item （ ）： １． Electrical center measurement device (2µm precision) ２． Cold model 1 set ３． Hot model 3 BPMs ４． Electronics 3 sets This year plan （ 2005 ）： １． Improvement of scanning antenna of center measurement device ２． Improvement of electronics; limiter amplifier before phase detection, more signal gain, reduce thermal noise, etc.

9 For ATF2 Quad-BPM Q-BPM ： １． ready to install in Oct. 2006, ready to operate in Feb ２． BPM pickup : Total 21(?), (by PAL?) ３． Electronics : digital conversion(?), (by SLAC?) 4 ． drawings : supply by KEK(?) 5 ． feedthrough : supply by KEK Pickup design plan ： １． Use existing KEK-cavity BPM design? X-Y isolation only 20dB, signal tend to small, coupling slot too large?, resonant waveguide working or not?, … or ２． Develop new design? (modify KEK-cavity?) start HFSS calculation, make cold model, antenna scan measurement, then hot model….