m PIC with Resistive Cathode Atsuhiko Ochi Kobe University 4102012 10 th RD51 collaboration meeting More stabilities and robustness is neede d for some application Operation in high ionized particle HIP ID: 530521
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Slide1
Developments and tests of
m-PIC with Resistive Cathode
Atsuhiko OchiKobe University
4/10/2012 10
th
RD51 collaboration meeting Slide2
More stabilities and robustness is needed for some applicationOperation in high ionized particle (HIP)Very high gain for detecting single electron
The electron density may excess the Raether limit
(107-8)Continuous sparks will destroy the electrodes easily because of existence of substrates near electrodes.Dead time due to resuming HV is also problem.
There are two approaches for stable operation
Reducing the sparkMaking spark tolerant structureSelf quench mechanism for sparks will be added, using MPGD (m-PIC) electrodes1st trial: Metal cathodes are covered by high resistivity material.This report: Cathodes are made from resistive material, and cathode signals are read using induced charge.
Requirements for more stability
A. Ochi, 10th RD51 meeting
2012/10/4
2Slide3
Previous trial: m-PIC with resistive overcoat
Resistive kapton is on the cathodes of m-PIC.We can detect signals using 55Fe, but there found no spark reduction
Gas gain < 10000
R
R
R
+HV
100
m
m
25
m
m
Cathode
Resistive sheet
An
ode
400
m
m
Drift plane
-
HV
~1cm
Detection area
: filled by gas
25μm
25μm
Anode
Resistive
film
Cathode
E-field will be dropped by spark current.
A. Ochi, 10th RD51 meeting
2012/10/4
3Slide4
At January 2012
(have been reported at 9
th
RD51 meeting)
All cathodes are made from carbon-polyimide
Pickup electrodes are lied under cathodes and insulator
We have
two
dimensional signals
However, it is difficult to operate in high gain (> 10000), and there is no spark
reductoin
There are many extra holes, cause from the miss alignment
The connectivity of anode pixels were also poor
m
-PIC with resistive cathode and capacitive readout: First trial
2012/10/4
A. Ochi, 10th RD51 meeting
4
Cathode-pickup
Anode
Insulator (polyimide)
Resistive cathode
Pickup
readout
AnodeSlide5
Improvements for manufacturingManufactured by
Raytech Inc.
2012/10/4
5
A. Ochi, 10th RD51 meetingTop patternCathode patternDouble side mask
Anode
pattern
Anode pattern etching
Anode PI etching
Anode plating
Resistive PI baking
PI stacking
Anode drilling by laser
Cu spattering from rear
Anode plating Slide6
Very good accuracy (compared with previous samples)
Surface resistivityAbout 50MW / strip (10cm)
2012/10/4
A. Ochi, 10th RD51 meeting
6
Micro scope picture of a prototype (RC27)Slide7
2012/10/4
A. Ochi, 10th RD51 meeting
7
Signal of 55Fe
(about 0.5V/
pC
)
Conditions
:
Ar:C2H6=7:3 mixture gas
Drift field: 3.3kV/cm
Va
= 660V, Gain ~ 20000
Cathode (pickup)
Anode
300mVSlide8
ConditionsDrift field = 3.3kV/cm55Fe (5.9keV)
Using the signal from cathode pickup electrodesResultsHigh gain (>60000) was achieved, and operation was stable
(in case of Ar:C2H6=7:3)There found small discharges over the maximum gain in right figure.
However, no big sparks have been found around maximum gain.
2012/10/4
A. Ochi, 10th RD51 meeting
8
Gain curve
Gain
Anode voltage [V]Slide9
Potential of electrodes:Cathodes (resistive): 0V Negative HVAnodes : Positive HV 0V
No HV on anodesAC coupling capacitors and HV resistors are not neededResult:High gain ( ~ 50000) was achieved as well as previous setup
Novel Operation condition with applying HV to resistive cathode
2012/10/4
A. Ochi, 10th RD51 meeting9- Cathode voltage
(0V)
R
+HV(~600V)
New operation
-HV(~-600V)
Direct connection to readout
Previous operationSlide10
A few MeV – few tenth MeV neutron will produce recoiled nucleon inside detectorsThat produce great amount of energy deposit (a few
MeV/mm2) in gaseous volume.The concerned problem for gas detector“Raether limit” … the electron cluster more than 10
7-8 cause the detector to discharge.We can evaluate the spark probability for HIP by measuring the spark rate dependencies on neutron irradiationNeutron sourceTandem nucleon accelerator (3MeV deuteron) + Beryllium target.
(Kobe University, Maritime dept.)
d+ 9Be n + 10BNeutron energy: mainly 2MeVSpark test using fast neutron2012/10/4A. Ochi, 10th RD51 meeting
10Slide11
HV current on anodes are monitored while neutrons are irradiatedWe found strong spark reduction using resistive cathode !!
Spark probability measurements
2012/10/4A. Ochi, 10th RD51 meeting
11
Normal m-PIC (metal cathodes) Gain = 15000
Irradiation: 2.4×103 neutron/sec
Resistive cathode
m-PIC
Gain = 15000
irradiation: 1.9×10
6
neutron/sec
[
m
A
]
10
8
6
4
2
0
[
m
A
] 10
8 6
4 2
0
neutron
Drift
-HV
(~1kV)
Cathode
= 0V
A
+HV
(~600V)
Anode
Voltage
recorderSlide12
2012/10/4
A. Ochi, 10th RD51 meeting
12
Spark probability for fast neutron (~2MeV)
Conditions
Gas: Ar+C
2
H
6
(7:3)
Drift field:
3.3kV/cm
Definition of the sparks:
Current monitor of HV module shows more than 2
m
A or 0.5
m
A.
Spark probability = [Spark counts] / neutron
T
he
spark rates on normal
m
-PIC are
are
also plotted as comparison (cyan, magenta plots)
.
Results
Reduction of sparks are obviously found.
The rate was 10
3-5
times less than normal
m
-PIC
case at same gas gain.
Spark reductionSlide13
m-PIC with resistive cathodes and capacitive readout is newly developed and tested.More than 60000 of gas gain is achieved stably using 55Fe source under Ar(70%)+ethane(30%) gas.
Sparks are reduced strongly. The spark rate under fast neutron (2MeV) is suppressed 105 times smaller than that of normal m-PIC.It can continue to run under intense (~10
6 n/cm2/s) neutron at high gain (~104).More improvement of the production is needed.To operate it at all detection area in order to use as imaging devise.
2012/10/4
A. Ochi, 10th RD51 meeting
13
Conclusion and future prospects
These researches are supported by
Japan MPGD Basic R&D Team.
Grant-in-Aid for Scientific Research (No.23340072)
RD51 collaboration