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

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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