Pixel Chamber m PIC with resistive cathode amp capacitive readout Atsuhiko Ochi Kobe University 9 th RD51 meeting CERN 21st February 2012 The m PIC is now quite stable ID: 235357
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Slide1
Micro Pixel Chamber (m-PIC) with resistive cathode & capacitive readout
Atsuhiko OchiKobe University
9
th
RD51 meeting
@
CERN
21st February, 2012Slide2
The m-PIC is now quite stableBy improvement of the productionHowever, more stabilities and robustness is needed for some applicationOperation in heavy ionized particle
Very high gain for detecting single electron The electron density may excess the R
aether
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.For muon detector in the LHC (HL-LHC) detector, those stability studies are very important!There are two approaches for stable operationReducing the sparkMaking spark tolerant structureNew IdeaSelf 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 9th RD51 meeting
21 Feb 2012Slide3
First trial: m-PIC with resistive overcoatResistive kapton
is on the cathodes of m-PIC.Large current from spark reduce the e-field, and spark will be quenched.
Huge signal beyond the “
Raether limit” will also be suppressedSignal from low energy deposit will observed with higher gas gainThis design provide one promising possibility of MIP detector under hadronic backgroundRR
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 9th RD51 meeting
21 Feb 2012Slide4
Setup for first prototypeVd = 2kV (2kV/cm)Vac = 500 – 620VGas: Ar+C2H6 = 1:1
10cm x 10cm
A. Ochi 9th RD51 meeting
10cm400
mm
21 Feb 2012Slide5
Improvements for production
10cm
First prototype
Sparks on cracks
4th prototype
Cracks are on substrate
No crack, but
bad quality
5
th
prototype
Qualities are
getting better
A. Ochi 9th RD51 meeting
Signal can be found, but slightly
improvements for stability was found.
21 Feb 2012Slide6
Remnant problems and new design
Sparks are still occurred on resistive
m
-PICMore precise manufacturing are neededProblems for alignment of anode and cathode position Dual page mask + liquid resistive captonDual page mask Both anodes and cathode images are printed simultaneouslyTo make higher resistivity between anodes and cathodesNew structure using capacitive readout from cathodes.
(Thanks to R. Olivaira)Spark will be suppressed more
strong
A. Ochi 9th RD51 meeting
First
resistive
m
-PIC
New resistive
m
-PIC
Connect to one pad
R
+HV(~500V)
R
(0V
)
Capacitive readout
For second coordination
21 Feb 2012Slide7
Start
from
PI
film with
cupper layer
Nickel plating on top
Double side photo exposure
Double side etching
PI etching from bottom
Cu pattern etching (second coordinate)
Prototype production process
for
new resistive
m
-PIC (
Raytech
inc.
)
A. Ochi 9th RD51 meeting
Polyimide (25mm)
Cupper
Ni
Photo mask
21 Feb 2012Slide8
SPB (50um)
Anode post plating with Nickel
Surface etching ( cathode pattern )
Resistive polyimide coating and baking
Grinding a surface resistive polyimide and attaching bottom substrate
Production process (cont’d)
A. Ochi 9th RD51 meeting
PI (50um)
21 Feb 2012Slide9
Making holes from bottom using laser drillingHole plating after Cu spatter
Etching the surface metal. Top of anodes and resistive cathodes are remained on surface.
Production process (cont’d)
A. Ochi 9th RD51 meeting
21 Feb 2012Slide10
Delivered at 8th Feb, 2012 from RaytechThis is second trial for capacitive readoutAnode pixel is well aligned at center of cathode
10cm x 10cm (400 micron pitch) has been producedTwo samples were producedSurface resistivity (mean of all surface) :0.7MW
1.2M
WSurface picture of a prototypeA. Ochi 9th RD51 meeting21 Feb 2012Slide11
Only one of two sample provides signals using 55Fe.Gas: Ar+C2H6 = 7:3Sparks are found because of parasite holes of anode pixels. (next slide.)
Operation tests (very2 preliminary)
A. Ochi 9th RD51 meeting
Cathode signals21 Feb 2012(Trigger from anode signals)Slide12
There found parasite holes …Laser drilling for anode pixels are not in right place due to deformation of the substrate.At the surface resistive polyimide baking.We need more improvements of process.
Problems
A. Ochi 9th RD51 meeting
Parasite hole
21 Feb 2012Slide13
m-PIC with resistive cathodes and capacitive readout is newly developed.We confirmed a operation principlyThe 55Fe signals are
read from both anodes and capacitive readouts.There remain some problems in production process.To improve the quality of production, we are considering following methods
Changing surface resistive materials
Some other organic material, or very thin metal layer, without baking for fixing it.Considering the process for makingNew operation condition with applying HV to resistive cathodeThere are no HV on anode No coupling capacitor is needed for anode readoutSummary and future prospectsA. Ochi 9th RD51 meeting
(0V
)
R
+HV(~500V)
New resistive
m
-PIC
-HV(~-500V
)
Direct connection to readout
21 Feb 2012