R & D at BHU

B.K. Singh

(On behalf of HEP Group)

Outlines

• Introduction

• Past Experience

• Present Plan

• Status

Brief History of Gas Detectors

Gaseous Detectors

• Good spatial resolution

• Fast & big signals

• Good dE/dx

• Two tracks resolution

• Large area coverage

• Many possible detector configuration

• Low cost

Simulation Tools:• Maxwell (Ansoft)

electrical field maps in 2D and 3D, finite elements calculations for arbitrary electrodes and dielectrics

• HEED (I. Smirnov)Energy loss, Ionization

• MAGBOLTZ (Steve Biagi)(electron transport properties: drift, diffusion, multiplication )

• GARFIELD (R. Veenhof) (Fields, drift properties, signals: interfaced to above

program )

These tools allow to simulate accurately detector configurations before constructions.

Gaseous Photomultiplier:

MICROPATTERN GAS DETECTORS (GEM)

Photocathodes (UV/Visible region)

Past Experience:

Microstrip Gas Chamber

Multiwire Proportional Chamber

GEM

Micromegasμcat, μGroove, μDot

Typical cell size>1 mm

Typical cell size ~ 100μm

Due to small dimensions, Streamers develop easily into sparks!

Multiplication of electrons induced by radiation in gas or from solid converters (e.g. a photocathode)

Multiplication inside holes reduces secondary effects. (No Photon feedback) THGEMs screen the

photocathode

Edrift

EHole

Etrans

Semi-transparent photocathode

Reflectivephotocathode

ALICE/HMPID concept of CsI RICH

- liquid C6 F14 radiator- proximity focussing geometry- small gap MWPC (~2 mm)

- cathode pads coated with CsI

1st generation gas based photodetector

with CsI photocathodes (PCs)

History

Late 1980ies:

J.Séguinot & T. Ypsilantis (CERN)

Searching for an alternative for

TMAE: successful R&D on small

samples of reflective CsI PC for UV

detectionEarly 1990ies: F.Piuz et al. CERN / RD26

Study development of large area

CsI photo-cathodes for RICH-id. for

Heavy Ion Physics NA44 / TIC @ CERN (0.3 m2) finishedSTAR / RICH @ BNL (1 m2) finishedHALL-A / RICH @ JLab (0.7 m2) runningHADES / RICH @ GSI (1.5 m2) runningALICE / HMPID @ CERN (11m2) next yearCOMPASS / RICH1 @ CERN (5.8 m2) running

Experiments with CsI RICH(active area m2)

MWPC

front-end electronics

pad cathode covered with CsI film

Requirements for large PCs

good flatness & stiffness

high & reproducible QE on large area

no contact with humidity (i.e. air)

during its full lifetime

Photodetector must be leaktight

(as should be all utilities)

substrate preparation

PC transfer & storage

detector assembly, operation & evaluation

PC deposition & quality

evaluation

PHOTOCATHODES: processing under vacuum and detector assembly & operation under gas

Need state of the art technologies:

- vacuum technology

- multi-source thin film coating

- quality evaluation

- in situ encapsulation

- cleanroom facilities

Technology of photocathodes

Recent papers:

BK Singh et al., NIM A454 (2000) 364

E.Shefer, J. App. Phys 92 (2002) 4758

Sealed visible gaseous photomultiplier

D. Mormann et al., NIMA 504 (2003) 93.M. Balcerzyk et al., IEEE Trans. Nucl. Sc. NS 50 (2003)847

. Sealed Gaseous Detector

. Triple GEMs (Kapton made)

. Semitransparent K-Cs-Sb photocathode

. Stable for few months

Simulation of the avalanche process in a single THGEM

• Ar/CO2 (70:30) 760 Torr

VTHGEM=600 V

ecoll = e- collected in the holes

e- produced above the holes

Fextrac = e- extracted from the holes

e- produced in the holes

GEM Hardware Plan

Efficient operation of GEM/THGEM needs: VGEM

- (focussing, Gain, backscattering etc)• Eextr

• Etrans

• Geometry (GEM/THGEM)• Gas/Gas purity

- low backscattering and sufficient Gain

GEM Hardware Plan

NIM CrateSpectroscopy

Amplifier (Ortec 672)HVPS (CAEN N471

A)THGEM foilGas etc

√ Preamplifier (142 AH/IH)

√ MCA 8K card with software

√ Chamber (plexiglass made)

√ Oscilloscope (600 Mhz)

√ Laminar flow table• Mesh/ R/O PCB• Source (55Fe) 10 mCi