CCD Readout of GEM Based Neutron DetectorsCCD Readout of GEM Based Neutron Detectors

F.A.F. Fraga, L.M.S. Margato, S.T.G. Fetal, M.M.F.R. Fraga, R. F.A.F. Fraga, L.M.S. Margato, S.T.G. Fetal, M.M.F.R. Fraga, R. Ferreira Marques, A.J.P.L Policarpo, B. Guerard, A. Oed, G. Ferreira Marques, A.J.P.L Policarpo, B. Guerard, A. Oed, G. Manzini and T. van VuureManzini and T. van Vuure LIP - Coimbra and Departamento de Física da Universidade de coimbra, 3004-LIP - Coimbra and Departamento de Física da Universidade de coimbra, 3004-516 Coimbra, Portugal516 Coimbra, Portugal

IInstitute Laue Langevin, BP 156X, F-38042 Grenoble Cedex, Francenstitute Laue Langevin, BP 156X, F-38042 Grenoble Cedex, France

DDelft University of Technology, IRI-ISO, Mekelweg 15, NL 2629 JB Delft, The elft University of Technology, IRI-ISO, Mekelweg 15, NL 2629 JB Delft, The

NetherlandsNetherlands

SummarySummary

• Gaseous detectors: GEMs and CCDs

• Experimental setup

• Gain and scintillation for GEMs with different diameters holes

• Electron transparency and transfer with GEMs

• Neutron detection in 3He-CF4

• High pressure Xe/TMA

• Conclusions

A

A

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H.V.

PowerSupply

CC

D

30 Cm

A

Keithley 602electrometer

X - RayTube

Schematic view of the system used in GEMs study

The GEM - gas electron multiplierThe GEM - gas electron multiplier

• CCD camera: QUANTIX 1400 (PHOTOMETRICS)

• Number of pixels 1317 x 1035 (6.8 x 6.8 m2 pixels)

• Binning - 2x2 up to 7x7

- less position resolution but lower noise!

• Nikon f50 d1.8 photographic lens with C mount adapter

• Quantum efficiency of the Quantix 1400 camera versus wavelength

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Wavelength (nm)

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CCD readout of GEM scintillationCCD readout of GEM scintillation

References “Quality control of GEM detectors using scintillation techniques”, F.A.F.

Fraga , et. al ., NIM 442(2000)417. "X-ray imaging detectors based on the Gas Electron Multiplier

scintillation light", F.A.F. Fraga, et. al., accepted for publication in IEEE 1999 TNS.

“Performance of a Tracking Device Based on the GEM Scintillation”, F.A.F. Fraga, L.M.S. Margato, S.T.G. Fetal, R. Ferreira Marques and A.J.P.L Policarpo, presented at the IEEE2000, Lyon, France.

Alpha and cosmic ray tracks taken with Ar-40%CFAlpha and cosmic ray tracks taken with Ar-40%CF44

Triple GEM, VGEM=450V, g=82, ED=1kV/cm, ET=3.4 kV/cm, b=7x7, EC=0.

241Am alpha particles energy = 5.48 Mev Range of 241Am alpha particles in Ar-40%CF4 = 3.4 cm

Tracking devicesimager built with a double

GEM with Ar-5%CF4

Range of alpha particles (5.48MeV) in Argon (1bar)= 44.9mm

E/R122keV/mm

Range of protons (573 keV) in CF4 (1bar)= 0.43cm Ep/Rp 133keV/mm

Double GEM :

Ar+5% CF4 Light Yield (detected photon/primary electron) 0.68

Triple GEM :

Ar+5% CF4 Light Yield 8 (detected photon/primary electron)

He+40% CF4 Light Yield 1 (detected photon/primary electron)

Related workRelated work

GEMs OptimizationGEMs Optimization• GEMs parameters:

– pitch 140 m,

– kapton thickness: 50 m

– holes diameter: 80, 60 and 45 m copper, 70, 50and 35m kapton, respectively

• The tests were performed with:

– CF4 and He-CF4

– drift field ED= 1 kV/cm

– X-ray tube high voltage 15 kV; energy ~12keV;

– collection field EC=0

• Gain = IS / IP

• Scintillation yield (a.u.) = CCD counts per second / secondary current

Field strength along the GEM channel for equal measured gains in GEMs with different metal hole size

-200 -100 0 100 200

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60 Gem 80/70 Gem 60/50 Gem 45/35

E (

kV/c

m)

z (micron)

Electric field simulationElectric field simulation

• Profile of the magnitude of the field at a surface at Z=0 for GEMs of different metal hole size

The energy deposition along the proton

and triton track in 1 bar CF4

Thermal neutron detection in Thermal neutron detection in 33He-CFHe-CF44

•Thermal neutron capture in 3He:

(3He, 1.8 Å )=5333 barns

3He + n p + 3H + 764 keV

•CF4

– proton(573keV) range= 4.4bar.mm

– triton(191keV) range= 1.6bar.mm

• fwhm = 0.7 RP

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VGEM (V)

Gai

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GEM 140/80: He-CF4 (600/400 mbar)GEM 140/60: He-CF4 (600/400 mbar)GEM 140/45: He-CF4 (600/400 mbar)

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1E-05

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VGEM (V)

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a.u

./e)

100%CF4GEM 140/80: He-CF4 (0,6/0,4 bar)

GEM 140/60: He-CF4 (0,6/0,4 bar)GEM 140/45: He-CF4 (0,6/0,4 bar)

Gain and Scintillation for different Gain and Scintillation for different diameters holes GEMsdiameters holes GEMs

• Data on CF4 + He, CF4 pressure = 400mbar, He pressure = 600mbar

Electron transparency and transfer Electron transparency and transfer with GEMs (He-CFwith GEMs (He-CF44))

GEM 80, 60 and 45 micron (He-400mbar CF4)

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GEM 80 to GEM 60 transfer (He-400mbar CF 4)

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Transf. x Transp.

Clean GEM chamber - stainless steel

GEMs 5 x 5cm2 with double conical holes

50mm diameter transparent window

Carbon fiber window or aluminium cover

Conversion region = 6mm deep

Distance between the GEMs = 2mm

Neutron detectorNeutron detector

Details of the clean GEM chamber

Images of proton and triton tracks in Images of proton and triton tracks in 33He- 400 mbar CFHe- 400 mbar CF44

Triple GEM camera

– two 80 m, one 60 m metal hole

– absorption space 3 mm

– ED (drift field) =1KV/cm,

– ET (transfer field) = 3.25 kV/cm,

– EC (collection field) = 0

– VGEM1 =VGEM2 = VGEM3 = 350V.

– Binning 7x7

– AmBe source with Polyethylene shielding

Images of proton and triton tracks in Images of proton and triton tracks in 33He- 400 mbar CFHe- 400 mbar CF44

• Projection of the light intensity along the track as measured by the CCD

High pressure Xe with TMAHigh pressure Xe with TMA

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Gain

Xe +2.5%TMA (3bar)

Xe+5%CF4 (3bar)

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150 200 250 300 350 400 450 500VGEM (V)

Gain

Xe +5%TMA (1bar)

Xe +2.5%TMA (3bar)

Xe +2.5%TMA (5bar)

Charge gain on GEM voltage and pressure measured for GEMs with 60 m hole diameter.

Measured spectra of some gaseous Measured spectra of some gaseous mixturesmixtures

Step=2nmSlit aperture=1mm

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(nm)

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He+40%CF4-1barAr+5%CF4-1barXe+5%TMA-1bar

(not corrected for PM quantum efficiency)

Quantum efficiency of some Quantum efficiency of some available CCDsavailable CCDs

ConclusionsConclusions

Optical readout of 3He neutron GEM detectors has been done

Information about charge deposits along the tracks can be easily read from the images

Higher CF4 pressures Improves spatial resolution (ILL)

Pressurized Xenon mixtures X-ray Synchrotron radiation

Photon counting/ Alternative readout with APDs and position sensitive PMTs