Re-entrant BPM R&D for ILC Main Linac AWG8 LCWS11@Granada 09272011 Re-entrant BPM R&D for ILC Main Linac A. Heo, J.-Y. RYU, Y.-I. KIM, E.-S. KIM Department of Physics Kyungpook National University, Daegu, Korea H. Hayano KEK, Tsukuba, Ibaraki, Japan S.-Y. RYU, J.-K. Ahn Department of Physics Pusan National University, Pusan, Korea

Main Linac Cold-BPM in Cryomodule BPM chamber Quadrupole Magnet

Requirements for Main Linac Cold-BPM in Cryomodule (1) The BPM measures beam position in cryomodule, bunch by bunch, with a resolution of less than 1 µm at 2x1010 electrons/bunch. -> low Q value for fast signal damping at 2K circumference -> good signal-to-noise ratio for high resolution -> high precision on mechanical center definition and electrical center definition -> high common-mode rejection, high isolation for x-to-y coupling (2) The beam pipe diameter 78mm (big diameter). -> low frequency resonant-mode BPM -> no coupling to cavity HOM and no conflict with cavity dark-current exitation (3) BPM is installed inside of cryomodule, next to SC-cavity. -> simple structure with no contamination inside (clean-room compatible) -> HPR rinse applicable -> light weight for easy to handle and to install in clean-room Design Base : Saclay re-entrant BPM adding waveguide loading for CM-rejection and X-Y coupling rejection

Proto-type model (Cold-model) magnetic coupling pickups Material: SUS small holes for rinsing water outlet dipole mode: 2.04GHz

RF characteristics of prototype model Input port Output port f[GHz] Df [MHz] QL Q0 b t[sec] 1 3 2.049 9.90 205 335 0.635 6.69E-8 2 4 7.81 262 475 0.808 8.57E-8 Port Slot Isolation [dB] Transmission [dB] 1 2 -27.18 3 -8.54 4 -27.34 -27.19 -7.03 -29.49

Antenna scan of prototype model

Beam response test of prototype model at ATF-LINAC (1) using simple circuit (diode, amp, integration ADC)

BPM setups Proto-type BPM housing TM010 refernece cavity Inside of Proto-type BPM housing Proto-type BPM TM010 refernece cavity

Beam response Raw signal After 2.04GHz BPF FFT of Raw signal FFT of BPF output ATF LINAC beam 1.3GeV single bunch 1 x 1010 electron/bunch 1.5Hz repetition Diode detection output

Resolution estimation by (pedestral noise)/(response slope) setup (A) setup (C) beam scan pedestal distribution with gaussian fit beam scan red line shows response slope red line shows response slope setup (B) beam scan pedestal distribution with gaussian fit pedestal distribution with gaussian fit red line shows response slope electronics setup axis pedestal noise [count] response slope [counts/µm] estimated resolution [µm] (A) Hybrid+BPF+diode+LF-amp X 3.47 4.57 0.75 (B) Hybrid+BPF+RF-amp+diode+LF-amp Y 3.65 8.02 0.45 (C) Hybrid+BPF+RF-amp+diode 1.96 5.33 0.36

Beam response test of prototype model at ATF-LINAC (2) using phase detection circuit (phase between BPM cavity, Reference cavity) Electronics setup BEAM TEST on Jan 2011 Phase detector +side (CH 0) -side (CH 1) beam intensity (CH2) detection (CH 3) ADC 10dB att. Ref. BPF future plan : ---- 30dB amp. BPM hybrid X-ports or Y-ports att. S Δ 20dB att. LO: 1329MHz LO generator Down convertor Down convertor Both signal were down converted to 714MHz, then fed into the phase detector. Analog output of the phase detector were fed into integration ADC (charge ADC).

Waveforms in the phase detector circuit X RF IN(2043M) Y RF IN(2043M) Down convertor X RF IN(714M) Y RF IN(714M) REF IN(714M) Phase detector Ref. BPF Down convertor +side (CH 0) -side (CH 1) beam intensity (CH2) detection (CH 3) ADC future plan : ---- 30dB amp. BPM hybrid X-ports or Y-ports att. Ξ Δ changed LO: 1329MHz SCOPE (1) SCOPE (3) SCOPE (2) SCOPE (4) SCOPE (5) SCOPE (6) SCOPE (7) SCOPE (1) rawsignal_Ch1 SCOPE (5) phasedetection_2_Ch1 SCOPE (6) phasedetection_2_Ch2 SCOPE (3) downconverteroutput_Ch1 data_24Jan2011

Y-ports data with 28dB att. _27 Jan 2011 Resolution estimation : phase detector circuit Y-ports data with 28dB att. _27 Jan 2011 R2:0.98273 ATF LINAC beam 1.3GeV single bunch 0.5 x 1010 electron/bunch 1.5Hz repetition Resolution = noise level [counts]/ slope [counts/um] BPM signal with 28dB att. + side side Noise level [counts] 19.5452 24.3839 Gradient [counts/um] 58.1498 Resolution [um] 0.336118 0.419329

Vacuum-tight Model (hot-model)

Vacuum-tight model (Hot model) Hot model fabrication was completed on May 2011 Feed-through + loop-antenna are demountable for final adjustment

Cold model Measurement RF characteristics of Vacuum-tight model (Hot model) BPM Network analyzer QL β Isolation Data Hot model measurement 345.442 0.874 -20.7 2011. 06. 29 Cold model Measurement 210.643 0.350 -29.8 46 40 5 4.4 22 28.2 78.27 78.17 8 R5 2 4 4.27 14 Measured as 13.7 Waveguide cold-model hot-model Difference of isolation may come from loop position difference.

Preparation of mechanical center measurement for Vacuum-tight model (Hot model) <<<Measurement is not yet done.>>> A Z mover stage B XY mover stage C Rotational stage D Cavity E Goniometer Stage F Antenna G1,G2 edge measuring device H Flange Adapter 750 20 137 50 330 160 125 90 380 170 350 162 225 150 35 222 55 3 40 70 130 210 152 200 75 21 10 G1 F A G2 E B C D H Range110 5+100 H20.5 H14 H34.27 Antenna: X-Y-Z movement -> Antenna scan Cavity-BPM: on rotational stage with X-Y stage -> BPM 180deg. Rotation with keeping mechanical center z y x

Beam Experiment plan for Vacuum-tight model (Hot model) Reference cavity 3-BPM for resolution estimation Digital signal acquisition Down-converter(2043MHz ->93MHz) + ADC(14bits 400Ms/s) + FPGA

Summary of Re-entrant BPM R&D for ILC Main Linac The Re-entrant BPM was designed based on “Saclay re-entrant BPM” by waveguide loaded pickup. Demountable-cold-model was fabricated and tested. (2) Demountable-cold-model was fabricated and tested. -> RF characteristic: -27dB port isolation, 0.12mm mechanical-to-electrical center difference -> beam test for resolution estimation was done for two electronics setup. ~0.4mm resolution at 1x1010 electron/bunch in simple circuit, ~0.4mm resolution at 0.5x1010 electron/bunch in phase-detection circuit. (3) Hot model was fabricated and under test. -> port isolation became worse, it will be revised. -> mechanical-to-electrical center difference will be measured by the rotation stage setup. -> digital detection circuit is under design. -> 3 BPM setup for resolution estimation will be done in ATF extraction line. -> cool-down test and High-pressure-rinse test are under planning.