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					UPDATE ON GEM/DHCAL
DEVELOPMENT AT UTA


       Andy White
   U.Texas at Arlington
(for J.Yu, J.Li, M.Sosebee,
    S.Habib, V.Kaushik)
         9/15/03
       Recent developments

 Moving to multi-channel prototypes
 GEM foil production
 Electronics – prototypes
 Module design concepts
     Double GEM schematic


                            Create ionization


                            Multiplication

                             Signal induction



From S.Bachmann et al. CERN-EP/2000-151
     Design for DHCAL using Triple
                 GEM


Embeded
onboard
readout


Ground to
avoid
cross-talk
          Multichannel prototype


- Next step: a 3 x 3 array of 1 cm2 pads.

- Allows one central pad with neighbors for
cross-talk tests.
- Use a single layer board for simplicity.
- Anode board built, prototype reworked.
- First results.
Nine Cell GEM Prototype Readout
Landau Distribution from Cs137 Source




                          Signal Amplitude (mV)
Readout electronics for DHCAL/GEM


 - Single channel electronics for first tests
  (high gain charge preamp + x10 voltage amp.)
 - Useful for initial development, but not cost
 effective for larger scale, multi-channel
 prototypes.
GEM Prototype with preamp/voltage amp
Amptek charge
 pre-amplifier
Readout electronics for DHCAL/GEM

- Discussions with Fermilab/PPD (Ray Yarema)
- Short-term use of electronics developed for
silicon readout. (T.Zimmerman)
- 32 channel boards. Now at UTA.
- Gain within factor of 3 of present single
channel system.
- Investigating DHCAL/GEM specific design
- Coherence with DHCAL/RPC – VME/daughter?
Fermilab preamp
for multi-channel
tests
          GEM Foil Production
- Original production at CERN – but slow, low
volume, manpower intensive and expensive.
- Interest in U.S. domestic foil production by
LC tracking developers and GEM/DHCAL.
- 3M Corporation (Microinterconnect Systems
Division), Austin, Texas has tried additive and
subtractive approaches.
- Foil production on 16 inch wide, 500 feet
long roll.
             GEM Foil Production
     Chicago-Purdue-3M
     P.S. Barbeau J.I. Collar J. Miyamoto I.P.J. Shipsey

Our Motivation:
Micro Pattern Gas Detectors (MPGD) in Particle & Astro-Particle Physics
TPC readout for LC (GEM or MICROMEGAS)
Tracking device at SLHC or VLHC
Low-background applications (e.g. coherent neutrino scattering)
& WIMP searches


+ DHCAL/GEM developments
+ Medical imaging potential
+?
                                    Mass Production is based on a 3M Proprietary
                                    Flex Circuit Manufacturing Technique
• 3M Microinterconnect
Systems Division Reel-to-reel                                          Reel to reel
process, rolls of 16”’x16”                                             flex circuit
 templates of detachable GEMs in any                                   manufacture
 pattern. Optional processes possible.
                                                                       in clean room
• First batch of 1,980 GEMs recently
 produced. Low cost per unit!
                                                                       conditions
 (~2 USD/GEM not counting R&D)
• Two fabrication techniques (additive,
 substractive) tested.




                                                                            Single
                                                                            roll of
                                                                            ~1,000
                                                                            GEMS




                                                                       hep-ex/0304013
                  Two fabrication techniques
        Subtractive           Additive




                              Additive
Subtractive (etching)
                              Cu added to patterned photo resist
(similar to CERN made GEMs)
                              on Kapton
                      3M Process Quality                            hep-ex/0304013


1. Subtractive: Clean hole structure, microcrystals, a small part of the batch have
     problems with adhesion of Cu on Kapton

                                   Cu
                                   microcrystal



2. Additive: Some holes not perfectly round  create hole to hole gain variation, a
small part of the batch have problems with adhesion of Cu on Kapton

                                                                       Additive
                                                                       method
                                                                       needs
                                                                       improvement
                                                                       to be useful
           Subtractive 3M Mass Produced GEM



Chicago
Purdue
3M
GEM



SEM
Courtesy
Fabio
Sauli
           Hole Profile


Chicago
Purdue
3M
GEM



SEM
Courtesy
Fabio
Sauli
                   GEM Performance

                     So far characterization focused on subtractive GEMs


      3M GEm                Typical 55Fe spectrum uncolllimated
      E/E = 16%            source.
                            Ar + 5% CH4 Lower GEM electrode.
                            E/E = 16% typical energy resolution as
                            good
                            as 14% observed.
hep-ex/0304013



      CERN GEM
                                       3M GEM and CERN GEM
      E/E = 18%
                                       Have comparable E/E = 16%


                        http://gdd.web.cern.ch/GDD/
                 Gas Gain
                                             Gain measured
                                             on PCB below GEM
Gain
measured
on lower          Ar/DME 9:1
GEM                               Ar/CO2 7:3
electrode
 CERN
                                         x
                                     x
                                                CERN GEM *
                                                   (*) S. Bachmann et al.
                                                   NIM A479 (2002) 294
                 Gains of 5,000 in Ar/CO2 7:3 & Ar/DME 9:1

        Gain almost identical to CERN made GEMS in same gas
                                             hep-ex/0304013
      GEM Foil Production

- Latest production 2 x 2 pattern of
10x10 cm2 foils.
- Use for DHCAL small prototypes and
module development
- 3M can make any pattern within the
roll parameters (~$2K for artwork)
Development of module concepts

     TESLA – HCAL Layout
    DHCAL/GEM Module concepts




Use half-size modules
 w.r.t. TESLA design
       DHCAL/GEM Module concepts


End                                Side
view                               view




       Bottom
        view
DHCAL/GEM Module concepts




                        GEM layer
                        slides into
                        gap between
                        absorber
                        sheets
   DHCAL-GEM Layer structure

- GEM layer -> 6mm
- Electronics layer ~3mm
- Absorber thickness 16mm x 40 layers
-> ~ 4 interaction lengths for HCAL
- 10x10 mm2 cell size -> ~1.5 x 107
channels for DHCAL-GEM
        DHCAL/GEM active layer

- Basic layer structure is clear
- Practical issues:
  - minimizing thickness, readout layer, ground
  plane(s) ??
  - stretching foils, foil separators, wall
  thickness
  - gas in/outlets, electrical services
       DHCAL/GEM active layer

- Exploring using the absorber steel gap to
provide active layer rigidity.
- Build jig to construct active layer with
stretch foil layers, thin side walls.
- Test transfer/sliding of non-rigid active
layer into steel gap.
- Start with available width foils from 3M
Design concept for sensitive layer




3mm ionization
   layer
          CONCLUSIONS

 Further prototype development
Exploring electronics solutions with
Fermilab/PPD
Availability of U.S. domestic GEM foils
 Investigating active layer construction
techniques

				
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