Atsuhiko Ochi Kobe University 25/06/2013 New Small Wheel MicroMegas Mechanics and layout Workshop

Activity reports Kobe Univ. /ICEPP Tokyo

-- MicroMEGAS with sputtering anodes --

Atsuhiko OchiKobe University

25/06/2013 New Small Wheel MicroMegas Mechanics and layout Workshop

About sputtering micromegas First operation test for sputtering

micromegas. The mechanical structure ideas for large

size production Future plan

25/04/2013A. Ochi, MMM workshop 2

Outline

Screen printing is used for current prototypes (@ CERN and Japan)◦ 400 μm pitch was available, but less

pitch is very difficult (in our experience)

We have proposed new technique :Sputtering with lift off process◦ Less than half pitch of readout strips

can be formed We will not need to take care the

alignment between resistive strips and readouts.(We have to confirm it)


About sputtering MicroMEGAS

Readout strips

Resistive strips

The resistive strips are formed using sputtering and liftoff technology

Very fine structure (a few tens micro meter) can be formed using photo resist. (same as PCB)

Surface resistivity can be controlled by sputtering material and their thickness


Liftoff process with sputtering

Substrate (polyimide)

Photo resist(reverse pattern of surface strips)


Metal/Carbon

sputtering


Developing the resists

@PCB company(Laytech inc.)

@Sputtering company(Be-Sputter inc.)

@PCB company(Laytech inc.)

Sputtering company They have large

sputtering chamber◦ Φ1800 X H2000◦ 1m X 4.5m (flexible board)

can be sputtered They have special

technology for uniform sputtering for large area

Large size production

25/04/2013 5A. Ochi, MMM workshop





Outline

Two prototype chambers with 10cm x 10cm have been just delivered on 3 weeks before, and last Thursday.

These are first prototypes of MPGD using sputtering technique for resistive electrodes.


First operation test for sputtering micromegas

To confirm the detector operation using sputtering technologies◦ Most uncertain issue was, stability of ultra-thin resistive

strip (~ 300micron).◦ We should check whether small sparks and/or big pulse

destroy the electrodes or not. Using intense fast neutron, we can make big

pulses and sparks.◦ Also this condition is similar to ATLAS cavern.

The our first test for sputtering MM is the operation test under fast neutron.◦ Other properties, i.e. position/timing resolution, should be

checked. However, that stability test has top priority.


We should check…

Beam time: June 17-23 (until the day before yesterday)

Be(d, n)B reaction was used by tandem electro-static accelerator in Kobe University.

Staffs and students from Kobe Univ. and ICEPP have joined.


Neutron beamtest

Pulse height distribution of 5.9 keV X-ray.◦ Anode = 540V, Drift = -300V◦ Drift spacing: 5mm◦ Gas: Ar(93%) + CO2(7%)◦ Estimated gain ~ 15000

HV current log under intense neutron.◦ Same as above conditions◦ Neutron intense is about 105

cps/cm2.◦ 0.01V correspond to 1 μA

~600nA of base current was found while beam ON.


Signals and spark current

1 μA

No difference is observed on the resistive strips condition between before and after neutron test


Before and after test





Outline

The readout board consists of Readout strips (Rigid PCB) Resistive strip foil (Polyimide film)

◦ Substrate thickness is 60 μm(25μm polyimide base and 35μm bonding film)

◦ There is no problem for making 10cm x 10cm


The mechanical structure for sputtering MM

Flexible foil (polyimide)

Rigid PCB (epoxy)

Resistive strips (sputtered)

Readout strips

Bonding film

Mesh

Pillar

We can divide the production process of resistive strip from that of readout board.◦ Resistive strip is formed on thin foil◦ Because of fine pitch, < 200 micron, we don’t need fine

alignment between resistive strips and readout strips. Dividing those processes will make the yield of

production growing up.


MM PCB production with parallel process

Readout board

ResistiveStrip foil

Currently, industrial company says ◦ 50cm X 1m

Proposed design for 2m X 1m test chamber◦ Consists of 4 resistive strip films.

More inputs are needed for designing strip line and film shape.


Resistive strip film layout (idea)

Small size … it’s OK. Large size …

◦ Principally, we have not to care the fine alignment of polyimide film gluing.◦ we should research the affect of polyimide gap.

Does it become instability operation? ◦ How to deal with the boarder of the resistive film?◦ We need more inputs for deal with this gap


We need some studies for combining rigid PCB and polyimide

PCB board

Polyimide film

Readout strip

Resistive strip





Outline

Controlling surface resistivity◦ We need input for optimal resistivity to be set

Making lower resistivity, we need long deposition time.◦ In this summer

Produce and test one more small test chamber◦ To apply floating mesh method, lower resistivity.◦ September - October

Tests for basic properties◦ Position / Timing resolution

Using Cosmic muon, charged beam line◦ Stability for ling time operation

Under intense neutron◦ August - October

Large resistive foil test production◦ Foil production

September - October◦ Together with PCB readout and making large chamber

October - November


To do list and schedule

We have operate sputtering MicroMEGAS successfully.

There is no defect after intense neutron operation.◦ Of course, We need more studies for longtime

operation and aging. The production process attaching rigid PCB

and polyimide film◦ For small chamber … no problem so far.◦ We need some idea for large size chamber.


Summary

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Atsuhiko Ochi Kobe University 25/06/2013 New Small Wheel MicroMegas Mechanics and layout Workshop