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A new design of the Micro Pixel Chamber using DLC electrodes
Speaker: F. YamaneA
A. OchiA, Y. HommaA, T. KawamotoB, T. MasubuchiB, Y. KataokaB, H. HasegawaA, N. NagasakaA, K. MatayoshiA, K. OgawaA
Kobe Univ. A
Tokyo ICEPPB
22/05/2017 MPGD2017, Temple Univ. 1
22/05/2017 MPGD2017, Temple Univ. 2
Outline• μ-PIC with resistive cathodes• The new design• First results of new μ-PICs
μ-PIC with resistive cathodes
22/05/2017 MPGD2017, Temple Univ. 3
μ-PIC with resistive cathodes
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➢ Property of the μ-PIC• Made by PCB techniques• 2D readout with Anode/Cathode strips (400um
pitch)• Enough gas gain to detect MIPs
• Any floating structures are not needed• Arranging μ-PICs to tile form -> Large area
➢ The μ-PIC with resistive cathodes• Resistive material for cathodes (105~7Ω/sq.)• High tolerance of discharges compared to
standard μ-PICs (10-3~4)• Induced charges are read from resistive cathodes
• Any capacitors for readout are not needed• Diamond Like Carbon (DLC) (details in the backup)
• Noble material made by carbon sputtering• Fine patterning (
Design of the resistive μ-PIC
22/05/2017 MPGD2017, Temple Univ. 5
25um
50umDF
FPC
↑Pickup Cathode
Resistive cathodeAnode➢ Production: RAYTECH Inc.➢ Carbon sputtering: Be-Sputter Co., Ltd➢ 256 channels -> 10cm x 10cm➢ The top layer: FPC (25um)
• Resistive & pickup cathodes are patterned each side on the FPC
➢ The bottom layer: Dry film (50um)• 256×256 pixels are well aligned
by photolithography. Anode strips are connected to the surface.
➢ 2 years ago (MPGD2015)• Anode strips were not connected
to the surface because of the remaining dry resist in the FPC layer.
• This problem has been solved by filling the holes with nickel pattern.
↑Anode Strip
MPGD2015Remaining dry resist
Black: DLCBrown: CupperGray: NickelRed: Sputtered nichrome
Operation tests
22/05/2017 MPGD2017, Temple Univ. 6
100
1000
10000
540 560 580 600 620 640 660Anode Voltage [V]
Cathode signalAnode signal
➢ Gas gain measurement using 55Fe source• Gas mixture: Ar:C2H6=90:10• Preamp: ATLAS ASD (0.8V/pC, τ=16ns)• Gas gains of > 10000 were obtained by
both anodes and cathodes readout.
➢ Fast neutrons irradiation test• Tandem Van de Graaff facility in Kobe Univ.• Neutron energy: ~2MeV• Neutron flux: >1MHz/cm2
• The μ-PIC could be operated stably in the irradiation environment of fast neutrons.
Current monitor on anodes
Beam on Beam offA
no
de
curr
ent
[nA
]
The new design
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Problem for all channels readout
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➢ In the current design, 16 strips were united to 1ch for simplification
➢ In order to read signals from all 256 channels, 256 RC circuits are needed.
➢ However, the large board for putting 256 resisters and capacitors is needed like bottom left picture.
Inside of the gas package
Backside of the gas package
μ-PIC
10cm
Detector
x 256
Equivalent circuits by DLC & PCB technique
22/05/2017 MPGD2017, Temple Univ. 9
Rigid Board↑Pickup Anode
Polyimide Gluing sheet
25um
50um
35um
DF
FPC
↑Pickup Cathode
↑Anode Strip
DLC CathodeAnode
➢ Bias resisters -> DLC• 400um pitch DLC bias resisters were
patterned on FPC➢ Capacitors -> Polyimide gluing sheet
• The μ-PIC were glued on the PCB which has readout strips correspond to anodes.
• The gluing sheet behaves as capacitors for respective strips (~22pF/strip)
DLC bias resisters x256
The new μ-PIC board
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μ-PIC
10cm
➢ DLC and PCB techniques have enabled all RC circuits to be put in the μ-PIC board (10cm x 10cm)
Detector
x 256
μ-PIC
PCB with anodereadout strips
First results of new μ-PICs
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The spectrum of 55Fe source
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➢ Gas mixture: Ar:C2H6=90:10➢ Preamp: ATLAS ASD(0.8V/pC, τ=16ns)➢ Noise level is very low. Clear signals of
5.9keV and 3.2keV could be seen. ➢ Energy resolution: ~20%(FWHM)@5.9keV
Anode signal Cathode signal
Gas gains of new μ-PICs
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Previous: 40umNew chambers: 75um
➢ Gas gains of >10000 were obtained on the anodes readout.
➢ New chambers could identify very small signals which have reached the lowest limit of MCA
➢ Difference of operation voltage is due to the size of anode diameter
➢ Difference of the anode diameter affects not only gas gains but also optimum drift field
100
1000
10000
460 480 500 520 540 560 580 600 620 640
The gain map of resistive μ-PICs
New uPIC1
New Upic2
Previous uPIC
Performance test using cosmic muons
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➢ Last week, new μ-PICs have succeeded to detect cosmic muons• New μ-PICs are compatible with
SRS-APV readout• mmDAQ was used for data
aquisition
Hit map of cosmic muons
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Hit map Hit map Hit timingHit timing ADCADC
➢ Left: Hit map of anodes• Empty spaces are correspond to 32strips where voltage were not applied.
➢ Right: Hit map of cathodes• RC38 could not detect signals.• This inefficiency must be studied.
Anodes Cathodes
RC37
RC38
RC41
RC37
RC38
RC41
Position resolution (1D)
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➢ Position resolution (1D) of the μ-PIC was measured by the residual method.• Operation gas gain: ~4000• 1519 events were obtained in 12 hours run.• Building cluster by uniting hit strips.• Hit position -> Center of the cluster mass• Requiring 1 hit on each chamber ->
169events• Residual: x2 - (x1 + x3)/2• Position resolution: σ/√(1.5) = 133um• Theoretical value: 400um/√12 =115.5um• However statistics are little, new μ-PICs
have showed good value
➢ 2D readout operation (2FECs needed) will be performed in the near future.
RC37 RC38RC41
Cosmic muon
x1 x2 x3
Preliminary
Summary & Future prospects
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Summary➢ The μ-PIC with resistive cathodes has been developed.➢ Resistive cathodes were made by Diamond Like Carbon.➢ DLC and PCB techniques have enabled all RC circuits to be put in the μ-PIC
board (10cm x 10cm)➢ Operation test
• Gas gains > 10000• Energy resolution ~ 20%(FWHM) @ 5.9keV• Position resolution of 133um was obtained on anode direction using cosmic
muons which is consistent with the theoretical value (preliminary)
Future prospects➢ 2D resolution, 2D imaging, 3D tracking➢ Optimization of parameters (operation voltage, resistivity, anode diameter)
Backup
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Diamond Like Carbon
2017/5/21 19
➢ Diamond Like Carbon (DLC): Noble resistive material composed of sp2 & sp3 amorphous carbon.
➢ Made by sputtering technique.➢ Developed by Kobe Univ. from 2012➢ Property
• Fine patterning (
Comparison: Gas mixture
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100
1000
10000
400 450 500 550 600 650 700
Gai
n
Anode Voltage [V]
Ar:C2H6=90:10
Ar:C2H6=80:20
Ar:C2H6=70:30
➢ Drift field: 1kV/5mm = 2kV/cm➢ Gas: Ar:C2H6=90:10, 80:20, 70:30➢ The maximum gain was achieved at gas mixture of Ar:C2H6 = 90:10
Comparison: Anode or Cathode
22/05/2017 MPGD2017, Temple Univ. 21
100
1000
10000
440 490 540 590
Gai
n
Anode Voltage [V]
Anode Readout
Cathode Readout
➢ Drift field: 930V/3mm=3100V/cm➢ Gas: Ar:C2H6=90:10➢ The gain of cathodes became larger than that of anodes.➢ The gluing sheet (35um thickness, 22pF/strip) may not have enough capacitance.
カソード信号の位置依存
2016/12/10 第13回MPGD研究会@ポーアイ 22
1~8 9~16 17~24 25~32 33~40 41~48 49~56
65~72 73~80 81~88 89~96 97~104 113~120
129~136 137~144
57~64
145~152 153~160 161~168 169~176 177~184 185~192
121~128105~112
193~200 201~208 209~216 217~224 225~232 233~240 241~248 249~256
アノード電圧印加範囲: 33~64strip→各測定範囲: 32strips×8strips
Neutron irradiation test
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D+ beam
Discharges in the pixel
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➢ Carbon like deposits were seen between the anode and the cathode.➢ This deposits have thickness about 10um.➢ This deposits could be removed by blowing or wiping.➢ This deposition seems to be originated from quenching gas.
Conductive passage
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➢ High voltage was applied on the damaged pixel.➢ Compared to the left picture (before), the passage between the anode and
the cathode is clearly seen in the right picture (after).➢ This passage could not be removed.➢ This passage was made by carbonization of polyimide.
Cutting dead pixels
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➢ Cutting resistive strips around dead pixels (right pic)• This will not affect the readout
because readout strips are under the FPC layer.
• Thanks to the ladder connections, voltage can be applied to other pixels. (bottom pic)