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CCD Readout of GEM Based Neutron Detectors

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Presentation on theme: "CCD Readout of GEM Based Neutron Detectors"— Presentation transcript:

1 CCD Readout of GEM Based Neutron Detectors
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. Manzini and T. van Vuure LIP - Coimbra and Departamento de Física da Universidade de coimbra, Coimbra, Portugal Institute Laue Langevin, BP 156X, F Grenoble Cedex, France Delft University of Technology, IRI-ISO, Mekelweg 15, NL 2629 JB Delft, The Netherlands

2 Summary 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

3 The GEM - gas electron multiplier
Schematic view of the system used in GEMs study

4 - less position resolution but lower noise!
CCD readout of GEM scintillation 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

5 Related work Tracking devices imager built with a double GEM with Ar-5%CF4 Range of alpha particles (5.48MeV) in Argon (1bar)= 44.9mm E/R122keV/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) Alpha and cosmic ray tracks taken with Ar-40%CF4 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 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.

6 GEMs Optimization GEMs parameters: pitch 140 m,
kapton thickness: 50 m holes diameter: 80, 60 and 45 m copper, 70, 50and 35m 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

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

8 Thermal neutron detection in 3He-CF4
Thermal neutron capture in 3He: (3He, 1.8 Å )=5333 barns 3He + n  p + 3H keV CF4 proton(573keV) range= 4.4bar.mm triton(191keV) range= 1.6bar.mm fwhm = 0.7 RP The energy deposition along the proton and triton track in 1 bar CF4

9 Gain and Scintillation for different diameters holes GEMs
Data on CF4 + He, CF4 pressure = 400mbar, He pressure = 600mbar

10 Electron transparency and transfer with GEMs (He-CF4)

11 Details of the clean GEM chamber
Neutron detector 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 Details of the clean GEM chamber

12 Images of proton and triton tracks in 3He- 400 mbar CF4
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

13 Images of proton and triton tracks in 3He- 400 mbar CF4
Projection of the light intensity along the track as measured by the CCD

14 High pressure Xe with TMA
Charge gain on GEM voltage and pressure measured for GEMs with 60 m hole diameter.

15 (not corrected for PM quantum efficiency)
Measured spectra of some gaseous mixtures (not corrected for PM quantum efficiency)

16 Quantum efficiency of some available CCDs

17 Conclusions 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


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