Development of GEM-based

Digital Hadron Calorimetry

Andy White

U.Texas at Arlington

(for J.Yu, J.Li, M.Sosebee, S.Habib, V.Kaushik)

GEM operation/features

First UTA GEM prototype

- structure, electronics

– results: cosmics, source

Multichannel prototype

Digital hadronic module ideas

Funding, collaboration

Outline

Double GEM schematic

From S.Bachmann et al. CERN-EP/2000-151

Create ionization

Multiplication

Signal induction

From CERN-open-2000-344, A. Sharma

GEM foil etching

GEM field and multiplication

70m140m

GEM foil hole size

GEM operations and features

Simple, robust Stackable (single, double, triple) Fast – electron signal 5ns Relatively low voltage (~400V/foil) Flexible – almost any anode design Durable – no aging in extended tests Gain 102 – 106

Design for DHCAL using Triple GEM

Ground to avoid cross-talk

Embeded onboard readout

First UTA GEM Prototype- Double GEM detector constructed using 10x10 cm2 foils from CERN.

- Single 1x2 cm2 anode pad.

- Charge preamp, then voltage amp.

- Cosmic trigger, small counters, low rate!

- Signal verification: no signal with (a) trigger counters displaced from anode pad, (b) air in GEM detector.

UTA GEM-based Digital Calorimeter Prototype

Anode pad

layout

1x2 cm2 pad

UTA GEM prototype – high voltage

GEM Prototype with preamp/voltage amp

Amptek charge pre-amplifier

GEM prototype – trigger counters

Single cosmic event: upper = trigger,

lower = preamp output

UTA GEM Calorimeter prototype

GEM cosmic signal distribution with Landau fit

GEM prototype – source tests

- Cs137 source, ~1 MeV electrons

- Wall of prototype thinned to allow electrons to reach ionization region of GEM, and use of thin trigger scintillators.

- Rate much higher than cosmics!

- Used secondary output of charge amplifier to generate ADC gate.

- Study signals, noise, gain,…

GEM prototype – source tests

Source signal

Noise

Landau Distribution from Cs137 Source

Signal Amplitude (mV)

GEM/MIP Signal Size Computation

-Double GEM – applied 419V/stage -Total Ionization (C): ~93 i.p./cm

48 e-/MIP (5mm gap)-Double GEM Intrinsic Gain: G-Charge preamp sensitivity (GC) : 0.25 V/e-

-Voltage amp. X10 (GV)

-Output signal = C x G x GC x GV

-Observed ~370mV signal (mean of Landau)

G = 3100 ± 20% (need better amplifier calibration)

CERN GDD group measurements

Measured UTA GEM Gain

UTA Prototype

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.

- Use e.g. HELIX chip for readout.

- Anode board built, prototype being reworked.

Nine Cell GEM Prototype Readout

GEM module ideas

- Start from basic TESLA detector layout

- Try simple design with GEM “drawers” slid into slots in absorber (formed from plates and spacers).

- GEM layer ~6mm, readout layer ?mm.

- Readout – amplifier, discriminator, register per channel close to anode pad. Multilayer board with multiple ground planes.

- Working on existence proof of readout, services, module boundaries, supports, …

TESLA – HCAL Layout

DHCAL/GEM Module concepts

Use half-size modules w.r.t. TESLA design

Design concept for sensitive layer

3mm ionization

layer

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 Module concepts

Bottom view

Side view

End view

DHCAL/GEM Module concepts

GEM layer slides into gap between absorber sheets

GEM operation in magnetic field

- Electrons drift along E-field lines which are ~radial in the overall detector frame.

- However, B-field exists in orthogonal direction.

- Forces on electron from E and B ~ equal

-> so…expect ~45 deg. drift.B

drift

E

Funding

• DoE ADR funding for year 1 completed-> Prototypes working, many simulation results (see talk by Jae Yu at this meeting)

• Request for two more subsequent years of ADR funding– First year of the two funded for ½ student

and ½ engineer/postdoc

• Equipment funds through ADR + LCRD– Allows us to contemplate construction of a

larger size GEM prototype

Collaboration

Discussions with Fermilab (Physics dept.) re support for development of:

- readout electronics (amplifier, discriminator, …)

- electronics “layer”

- GEM calorimeter stack for test beam

Agreement (June ’03) to proceed.

Conclusions

Built and operated first prototype

Cosmic and source results – gain OK

Multi-channel prototype being built

First ideas on module design

Funding in place for another year

Collaboration with Fermilab agreed.