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Development of cavity-type beam position monitor with a resolution of a few nano-meter
Si-Won Jang, Ae-young Heo, Ji-Gwang Hwang, Eun-San Kim*, Hyoung-Suk Kim, Hyangkyu Park Kyungpook National University, Daegu, Korea
INTRODUCTION OF LOW-Q IP-BPM ATF2 in KEK
-Accelerator Test Facility 2 for the International Linear Collider (ILC)
-The second goal: Achievement of nano-meter level beam position resolution for
beam stabilization.
The characteristics of Low-Q IP-BPM
- Achievement of higher beam position resolution (~nm)
- Short decay time (15ns for Y-port)
- Beam position measurement possibility of the bunch train
THE SCHEME OF BEAM POSITION
RESOLUTION TEST FOR LOW-Q IP-BPM
Measurement Scheme:
-A one Low-Q IP-BPM (KNU)
-Two High-Q IP-BPMs (KEK)
-Two sets of horizontal and
vertical movers
-Electronics for each IP-BPMs
-11bit oscilloscope
BEAM POSITION RESOLUTION
MEASUREMENT OF LOW-Q IP-BPM
I-Q tuning
X-port Y-port Reference
f0 (GHz) 5.712 6.426 6.426
β 8 9 0.0117
Q0 5900 6020 1170
Qext 730 670 100250
QL 656 602 1156
τ (ns) 18 15 29
We developed a low-Q cavity-type BPM system that includes electronics and data analysis. We have performed the beam
tests on the beam position resolution for the low-Q cavity-type BPM. Resolution tests for the low-Q BPM were
performed at KEK ATF2 in Jan. 2011. We got the results of beam position resolution of 70 nm and present the detailed
experimental procedures and test results, and upgrade plans that aims at a resolution of 2 nm.
Electronics (Right figure)
- Produce I-Q signal (90 degree difference)
- I-Q tuning by using phase shifter
- I-Q tuning by using phase shifter
- Signal process time = 20 ns
Installed appearance of Low-Q IP-BPM
and High-Q IP-BPMs in the ATF2
Electronics block diagram of
Low-Q IP-BPM
Calibration run
Resolution run
UPGRADE PLAN FOR 2nm RESOLUTION
Al LOW-Q IP-BPM
NEW ELECTRONICS
CONCLUSION We got the results of beam position resolution 70nm for the Low-Q IP-BPM in Jan. 2011. Three IP-BPMs will be fabricated to install at the IP region. The electronics of Low-Q IP-BPM was upgraded to get the high beam position resolution. The ultimate goal is to obtain a resolution of 2nm and orbit stabilization through beam feedback at the IP region.
Calibration run was performed to calibrate the
sensor cavity response to actual beam position. To
monitor the response of sensor cavities due to
vertical beam position, the electron beam was
swept against sensor cavities by vertical movers.
Calibration factor
(mV/nm)
Stat. Error
(mV/nm)
Low-Q IP-BPM
(40dB Amp.) 0.674 0.0264
High-Q IP-BPM 1 0.922 0.0451
High-Q IP-BPM 2 0.720 0.0260
Calibration factor = 0.674 mV/ nm
beam
)R/Q(Q
ZqV
ext
0 out2
2
2
0
228
ybab
LT)y(
Q
R
IF
Base plate
post
mover
IP-BPM
Beam signal calibration
X X X
Beam position prediction
X X X
Beam position measurement
Convert to residual
nm 70factorn Calibratio
ResidualFactor_lGeometricaResolution
Residual Gaussian fitting
Residual value = measured position – predicted position
Sampling number
I-Q tuning was performed by using oscilloscope.
When I signal shows the maximum position, Q signal
is set to zero position by using phase shifter. For this,
I & Q signal means the beam position signal and
angle signal, respectively. If we do not performed I-Q
tuning, the electronics will be easily saturated by large
beam angle signal. Thus we also can’t expect good
beam position resolution.
Port f0 (GHz) β Q0 Qext QL τ (ns)
X-port 5.7059 5.6 4955.64 884.83 750.78 20.94
Y-port 6.4228 7.5 4884.67 649.74 573.46 14.21
Port f0 (GHz) β Q0 Qext QL τ (ns)
X-port 5.7050 4.48 4005.53 894.80 731.41 20.40
Y-port 6.4217 6.17 3903.95 632.36 544.21 13.49
Copper ver.
Aluminum ver.
The aluminum Low-Q IP-BPM was designed to reduce weight and was simulated to compare with copper version IP-BPM. The performance of the designed Al Low-Q IP-BPM shows the similar result to copper version Low-Q IP-BPM. Nevertheless, the weight of Al Low-Q IP-BPM was reduced 1/3 of copper version Low-Q IPBPM.
BPFPA
Phase
shifter
Power
divider
Hybrid
CouplerBPFRing
CouplerMixer
LNA
LNA
LO
RF
RF
Detection
Power
divider
LNA
DA
IF1(I)
IF1(Q)
OPAMP
Phase
Control
LPF
BW : 40MHz
Atten. Atten.
LNA
Feature of new electronics 1. High conversion gain (70dB) 2. High isolation in the mixer 3. Remotable phase shifter 4. Short latency time