Developments and tests of - PowerPoint Presentation

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

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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)

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A. Ochi, 10th RD51 meeting

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Micro scope picture of a prototype (RC27)Slide7

2012/10/4

A. Ochi, 10th RD51 meeting

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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

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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

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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

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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