development of micromegas using sputtered resistive electrodes for atlas upgrade

Development of MicroMEGAS using sputtered resistive

electrodes for ATLAS upgrade

Atsuhiko Ochi1, Yasuhiro Homma1, Tsuyoshi Takemoto1, Fumiya Yamane1, Yousuke Kataoka2, Tatsuya Masubuchi2,

Yuki Kawanishi2, Shingo Terao2

Kobe University1, ICEPP2

05/07/2013 RD51 workshop @ Zaragoza

Introduction Prototype production of sputtered carbon

foil MM prototype and tests Feasibility for mass production Summary

05/07/2013A. Ochi, RD51 workshop 2

Outline

High position resolution for one dimension◦ <100 μm for eta direction.

(Resolution of a few cm is allowed for second coordinate.)

Tolerant for high rate HIP particles◦ ~ 5kHz/cm2

Resistive layer should be formed as strips

There should be a technology for large size production (~1m)

Mass production should be available◦ ~2000 board should be produced in

half year. Low cost


Requirements for ATLAS NSW MM

+HV

Mesh(GND)

Screen printing ◦ Already several prototypes (@ CERN and Japan) has been

produced.◦ Made from carbon loaded polymer.◦ Large size (>1m2) is available◦ 400 μm pitch was available for MAMMA production.

Sputtering with lift off process◦ New technique.

Just first two prototypes (10cm x 10cm MM) are available at last month.

◦ Fine pattern (~10μm) is available.◦ Large size (>1m2) is available in industrial facilities.◦ Production quality is very well.

It is not affected by production environment


Two option for resistive electrodes

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 using 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.)

Large size sputtering is available◦ 4.5m x 1m for flexible film


Sputtering facilities

Vacuum chamber (with Ar gas)

Rotating drum4.5 m round

Sample

Sputteringtarget

Be-Sputter Co. Ltd.(Kyoto Japan)


Prototype of resistive strips


Carbon (300-600Å)Tungsten (10-50Å)

Fine strip pitch of 200 μm is formed on 25μm polyimide foil.◦ More fine structure will be available.

Surface resistivity is controlled in 2M – 10M/sq.◦ Depend on carbon thickness◦ Low resistivity (~100k/sq.) will be

available with thicker carbon. (Will be available in next batch)

It keeps strong adhesion and stability of resistivity.

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)

◦ Mesh was formed by bulk MM technique.◦ There is no problem for making 10cm x 10cm.


Prototype MicroMEGAS production

Flexible foil (polyimide)

Rigid PCB (epoxy)

Resistive strips (sputtered)

Readout stripsBonding film

Mesh

Pillar

25μm

35μm

Two prototype chambers with 10cm x 10cm have been just delivered on June 2013.

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

Gain curve of 5.9 keV X-ray.◦ Drift = -300V◦ Drift spacing: 5mm◦ Gas: Ar(93%) + CO2(7%)

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 μAVery preliminary

4804905005105205305405505601000

10000

100000Gain

Very preliminary

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


Before and after test

Assumption:◦ Size of foils: 1000mm x 500mm◦ Quantity: 3000◦ Sputtering: W:10Å, C:600Å

500 foils / month can be produced◦ 8 foils can be sputtered

simultaneously in one batch.◦ Sputtering time is estimated 2

hours.(Including overhead, 3 hours / one batch)

◦ 24h/3h x 8 foils x 20days = 1280 foils / month(Applying safety factor >2 500 foils/month )

◦ It will take half year, for full production.

Cost estimation (Very rough, but probably upper limit)◦ Sputtering cost:

1k CHF / one batch (for spattering 8 foils)130 CHF / foil )

◦ It is not sure for the cost of liftoff process, but it is estimated around 200 CHF/foil

◦ Total 330 CHF/foil, 1M CHF for full production

Mass production feasibility

05/07/2013 14A. Ochi, RD51 workshop

Exposure machines in clean room

PCB/FPC production line in

Electro forming machines Etching machines

We can divide the production process of resistive strip from that of readout board.◦ Resistive strip is formed on thin foil◦ 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

MPGD electrodes using sputtering has been proposed firstly.

First prototype of MicroMEGAS using sputtered resistive electrodes are produced and tested, for ATLAS NSW detector development.

It works as same as conventional resistive strip MicroMEGAS◦ Gain curve, operation in HIP were tested. It’s OK.◦ We should check position/timing properties.

There is no damage after spark (big pulse) operation using fast neutron


Conclusion

development of micromegas using sputtered resistive electrodes for atlas upgrade

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