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HB2008
Aug. 26, 2008
Beam loss monitoring using proportional counters at J-PARC
T. Toyama, K. Satou, S. Lee,
A. Akiyama, Y. Hashimoto, N. Hayashi, H. Nakagawa
J.Odagiri, T. Suzuki, M. Tejima, K. Yamamoto, N. Yamamoto
KEK
Contents(1) Using proportional conters at the KEK-PS
(2) Improvements to use in J-PARC
(3) Beam loss monitor system at the J-PARC MR
(4) Experience at the J-PARC MR
(5) Conclusion
(1) Using proportional conters at the KEK-PS
KEK-PS Booster (500 MeV) Yamaguchi, Someya et al.
Fast response turn by turn
Amplifier using electron tube (impedance conversion)
Contributed to finding H- injection inefficiency
using @gain = 2 - 100
Life time ? (gain degradation?)
Linearity ? Qu
ickTim
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Gas: Argon 90%, CH4 10%
50ns/div
(2) ImprovementsLonger life time
Gas : Ar 99%, CO2 1 %60Co irradiation test
Improved with Ar 99%, CO2 1 %
A
rbitr
ary
A
rbitr
ary
MR collimator
Linearity
Dose estimate
around the collimator
by MARS
Vertical Horizontal
QBeam
3-50BT collimator
RCS collimator
Dose calculation at 3-50BT Colliamator by MARS Neutral Fluence Distribution Charged Fluence Distribution
Point loss
Uniformloss
Instantaneous pulsed dose at the collimator
Uniform loss ~ 0.012 Gy = 1.2 radPoint loss ~ 0.15 Gy/shot = 15 rad
1 shot ~ 8.5 1011 p: equivalent to 450 W loss (limit)
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right
left right
BLM
~Gy
~mGy
logscale
Dose at the collimator downstream (Ar )
Gain curve obtained with cosmic ray
For the collimators working at high intensitiesIonization chamber may be appropriate
will be prepared, complement prop. counter
Positive ion space charge depresses gas gain
Preliminary
@HV= -1.6 kV
0.5 Wcontinuous loss
Instantaneus lossfar beyond
simplified calculationR.W.Hendricks,Rev.Sci.Inst. 40 (1969) p.1216.(factor “” is corrected)
800 mm
Anode wire 50 m Pt
HV cathod I.D. 23 mm stainless steel
Effective areaAr 99% + CO2 1%: 1.1 atm
Sensitivity
200 nC / rad x gain (calculation)
gain ~ 60000 (~2 kV)
200 nC / rad x 1.2 rad / shot x gain= 240 nC / shot x gain
(3) Beam loss monitor system at the J-PARC MR
24 S-BLM : Inj. / Ext.90 P-BLM : Ring20 AIC-BLM : Ring
12 S-BLM : RFQ-DTL105 P-BLM : DTL-L3BT12 AIC-BLM : DTL-L3BT
~300 P-BLM : Ring / 3-50BT
21 AIC-BLM : Ring / 3-50BT
HV PS
HV checking
Analog circuit
Vref
Div
ider
+LP
F
Proportional counters
ADC 100Hz,12bit
MPS/ABORT ( Raw )
Reference voltage
MPS/ABORT ( Integrated )
MPS/ABORT
Reference voltage
Zin, gain control
Fast ADC
Reset
積分器
Loss Abort<10μs
238 BLM’s @MR50 BLM’s @3-50 BT
800 mm
Anode wire 50 m Pt
HV cathod I.D. 23 mm stainless steel
Effective areaAr 99% + CO2 1%: 1.1 atm
Response rise time ~ 100nsIntegrated Zin = 50Ω, gain = 10, HV = −1.6 kV
(4) Experience at the J-PARC MR
1stturn
2ndturn
downstreamof 1st collimator
downstreamof 3rd collimator
RG59/u 8DFB
Cosmic ray
Sensitivity
200 nC / rad x gain (calculation with MIP)
gain ~ 60000 (~2 kV)
Linearity
Cosmic ray
point-like loss <100ns@3-50BT collimator
Saturation of the processing circuit, NOT of the head (?)
Translate the signal charge to loss amountusing MARS result of point loss
To be checked
Preliminary
Sensitivity with the beam
zoom in
Number of loss particles
0 50 100 150 200
0
0.5
1
1.5
2
2.5(×1010)
10 20 30 40 50 60 700
0.51
1.52
2.5(×1010)
QM#
QM#
QM#
QM#
80 90 100 110 120 130 1400
0.5
1
1.5(×109)
βx βy
η
A B C
A
B
C η=0
η=0
η=0
150 160 170 180 190 200 2100
0.51
1.52(×1010)
P
roto
n lo
ss
0.5 W/m loss :0.1% 5.7x1012 ppp (@ 3GeV)
1.7% 3.4x1011 ppp (@50GeV)
0.5 W loss (point loss): 3.7x109 ppp (@ 3GeV)2.2x108 ppp (@50GeV)
Su
m o
f a
ll B
LM
’s
Integrated Zin = 10kΩ, gain = 10, HV = −1.6 kV
normalizeby lost NB
DCCT
sensitivity ~ 108 protons loss
preliminary
(5) Conclusion
Sensitivity ( 1 MIP @ HV = -2kV) - ~108 p loss equivalent @HV = -1.6kVdepend on the HV (gain)
Response ~ 100 ns
Linearity < ~ 1010 p(complemented with ion chambers at lossive area as collimators, extraction area ... )
Radiation hardnesslittle problem in principle
J-PARC uses PE connector outside the gas-sheel
small gain degradation
to be examined more with the beam
to be confirmed