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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)
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