Cintiladores Gasosos Activos

F. A. F. Fraga, P. Mendes, L. M. S. Margato , M. M. F. R. Fraga, S. T. G. Fetal, Filipa Balau, R. Ferreira Marques, A.

J. P. L. Policarpo

LIP Coimbra, Universidade de Coimbra

Resumo

• Cintilação do GEM

• Operação de GEMs com conversores de comprimento de onda

• TPCs com GEMs com leitura óptica

• Simulação de um sistema de leitura de luz para GEMs com PMTs

• Polarímetro de raios-X

• Testes GEMs da 3M

• Projecto MILAND

The GEM - gas electron multiplier - a pre-amplifying structure

See http://gdd.web.cern.ch/GDD/

Pulse analysis of light signals• Our previous work has shown that light

pulses in He-CF4 are very fast (rise time less than ns)

• Can we estimate alpha track orientation from the light pulse structure collected with PMTs?

• System allows – precise definition of track angle

– simultaneous recording of

– CCD image - track oriention

– digitized light pulse

H.V.

47

mm

GEM 1

3 m

mTransparentWindow

5.

5mm

2 m

m

2 m

m

GEM 2GEM 3

CCD - Hamamatsu512x512 Pixel

24x24m

Drift Plane

241 Am

5mm

P-terphenyl absorption and emission

p-terphenyl

0

5000

10000

15000

20000

25000

30000

35000

40000

200 220 240 260 280 300 320 340 360 380 400 420 440

(nm)

Mo

lar

ext

inct

ion

co

eff.

(cm

-1/M

)

0

0.2

0.4

0.6

0.8

1

1.2

Fluorescence intensity (a.u.)

Conical GEMs

• Electron microscope cross-section of the double-conical or standard (a), conical (b) GEMs

Spectrum of Ar-TEA with GEMs coated and not coated with p-terphenyl

0%10%20%30%40%50%60%70%80%90%

100%110%

200 240 280 320 360 400 440 480 520 560 600 640 680 720 760 800 840 880

Wavelength (nm)

#PM

T/s

e no

rmal

ised

to T

EA

m

axim

um p

eak

Ar5%TEA 26-11-2002

Ar5%TEA p-terphenyl19-12-2002

No p-terphenylStep = 2 nm; Dl = 4,65 nm;Ed = 1kV/cm;Vgem = 260 V;Ei = 0 kV/cm;VRX = 10 kV;

IRX = 0,100 mA

P-terphenylStep = 2 nm; Dl = 4,65 nm;Ed = 1kV/cm;Vgem = 330 V;Ei = 0 kV/cm;VRX = 10 kV;

IRX = 0,500 mA

CCD images of uniformly irradiated GEMs

a) full spectrum

b) bandpass filter

Simulation of light signals in a PMT readout

• Monte Carlo simulation of localization by light centroid

• Light is emitted at the GEM plane and is punctual - no light diffusion and/or reflexion!

• Only the four nearby PMTs are considered

Light collection simulation3cm diameter PMTs

y

x

z

dPMT plane

GEM plane

3 2

14

PMT(1,3) assimetry

PMT(1,4) assimetry

Assimetry(1,3) statistics106 photons

Assimetry(1,4) statistics106 photons

Next steps

• Avalanche dimmensions

• PMT noise and non uniformity will be added

• Assembly of a system with four PMTs and a sweeping source

3M GEMs preliminary tests

• A First Mass Production of Gas Electron Multipliers , P.S. Barbeau J.I. Collar , J.D. Geissinger , J. Miyamoto , I. Shipsey and R. Yang

3M’s roll to roll flexible circuit manufacture in clean room conditions.

First tests using Ar -5% CO2

1

10

100

1000

200 250 300 350 400 450

Vgem (V)

Ga

in

CCD setup

-Vdrift

Front electrode Back electrode

GEM

Glass window

Scintillation image of a 2.5 cm diameter 3M GEM

• Ar5%CO2;

• IRX=1.000 mA;

• Lens detector distance = 21 cm

• Drift lenght= 7 mm;

• Ed= 1 kV/cm;

• Vgem=420 V(G~94)

• Kodak CCD

Scintillation image (zoom)

MIDLAND, Millimetre Resolution Large Area Neutron Detector

• 6th Framework Programme (FP6), (JRA2 Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy (NMI3)