Dual-Stage Gas Proportional Scintillation Counter – New Developments A.F.V. Cortez, C.A.N. Conde, S.J.C. do Carmo, F.I.G.M. Borges Contact: andre.cortez@coimbra.lip.pt Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy)
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Co Contents ntents Objectives and Motivation Development of a new HPXe-GPSC Working Principle and Experimental Setup Results Simulation Experimental Conclusions and Future Work 2
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Objec jectives tives and nd Moti otivatio ation Deve evelop lop a new new hi high gh-pre ressur ssure, e, xenon enon-base ased gase gaseous ous radia radiati tion on det detec ector tor of of the the GPS GPSC type ype for for hard X-ray and and gamm mma-ray ay spect ctromet rometry ry. Here are some reasons why use HPXe GPSC SC? *Energy resolution; *Operation at room temperature; *Lower cost; *Large detection area; *Flexibility in the geometry definition; 3
1. 1. Ga Gas s Proportional oportional Scinti ntillation llation Co Counter ter – The e De Detector ector Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy)
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) The he De Detect tector or – MGHP GHP GP GPSC 17 cm Anode (tens of keV) Shielding grid (grounded) Alpha particles 30 cm support structure 0.5 cm (for initial tests) 0.5 cm 5.5 cm 2 cm Photocathode (grounded) Collecting grid (few keV) 1.5 cm 0.5 cm 5
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Working king Princi nciple ple Signal Formation The HPXe detectors of the MGHP-GPSC type consist of four distinct regions: B B A C D A C D γ D • A - Absorption/Drift Region; • B - Secondary Scintillation Region; • C - Electric Field Barrier Region; • D - Photoelectron Collecting Region; VUV photon 𝑈 𝑝𝑞𝑢 - Grids optical transm. Photon Charge 𝐻𝑏𝑗𝑜 = 𝑂 𝑇 . 𝑈 𝑝𝑞𝑢 . 𝑅𝐹. η QE - Quantum Efficiency Amplification • Incident energy (Er) • Solid angle η - Extract. Efficiency • w-value • Opt. Transmission • E/p at the anode 𝑈 𝑝𝑞𝑢 = 𝑈 𝑡ℎ𝑗𝑓𝑚𝑒 . 𝑈 𝑑𝑝𝑚𝑚𝑓𝑑𝑢. • Gas • Quantum Efficiency • Pressure • Extraction Efficiency • Gas ( η ) 2π − 2θ(𝑠) Ω(𝑠, 𝑨) 𝑂 𝑇 = 𝐵𝐹 𝑇 𝑠 − 𝑞𝐶 𝑒𝑠 𝑒𝑨 Energy Collection 2π 4π deposition Region B Region D Region A Charge Photon production Anode shadow Solid angle 5
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Plana nar vs Cyli lind ndrica rical l Geometry metry Energy Range: 100 keV – 1 MeV Regions E/p Length Length V.cm -1 torr -1 Cylindrical Planar Absorption/Drift 0,03<1 30x5,4 cm 4,0 cm Scintillation 1 – 6 0,5 cm 0,7 cm B A C D γ Optical - - 1,2 cm transmission Electric field barrier - 2,0 cm 2,4 cm Photoelectron <1 0,5 cm 1 cm collection Cha haracter eristics Cylind ndrical geom eometry (Planar) Comparing both geometries, the Pressure Range <20 atm cylindrical presents: (<10 atm) Detect. Efficiency ~20% • Improved Solid Angle (662 keV/15 atm) (<4%) B A C D • Improved Detect. Efficiency Solid Angle ( Ω /4 π ) 0,48-0,87 (0,12) • Improved Active Volume of Detection 3369 cm 3 Detector Active • Optical Transmission (726 cm 3 ) Volume • Lower Biasing Voltage for the same gain Detector gain 10 - 30 phe-/e- (~10 phe-/e-) 7
2. Simu mulation lation and d Expe perimental rimental Re Resu sults lts Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy)
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Tests sts with th Alpha lpha Particle ticles - Simulation mulation 241 Energy of the Am – 5.486 MeV Deterioration due to the Mylar window 6,0 25 Energy Alpha particles (after Mylar) 5,0 Energy Resolution 20 4,0 E α (MeV) 15 R % 3,0 𝐺𝑋𝐼𝑁 𝑁𝑧𝑚𝑏𝑠 ~0.23 % 10 6,00 2,0 Max incidence angle 5,00 5 Combined effect 1,0 Energy (MeV) 4,00 of about 2% in the 3,00 energy dispersion 0,0 0 𝐺𝑋𝐼𝑁 𝑁𝑧𝑚𝑏𝑠 ~2 % 0 5 10 15 20 25 30 2,00 Mylar window width ( μ m) Energy of the Alpha-particles 1,00 Am 241 - Alpha-particle energy Alpha particles end up with only 4.486 MeV 0,00 Energy degradation after crossing the Mylar window + energy 0 10 20 30 40 50 60 70 80 90 Incidence angle (degrees) dispersion. 9
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Experimen Ex perimental tal Tests sts wi with h Alpha pha Pa Parti ticl cles es Signal E/p anode E/p collecting region E/p (V.cm -1 .Torr -1 ) 0 4 8 12 16 20 • • Positive • Extended scintillation Increasing Signal Amplitude (mV) 2500 E/p at the feedback in • region ( small extraction Scintillation above 2000 anode surface ionization due to the the collect. 2 V.cm-1.Torr-1 at efficiency 1500 the anode radial electric field ) region 1000 • Positive feedback 500 observed above Improves Signal increases 0 1 V.cm-1.Torr-1 greatly the gain (more light being produced) 0 3 6 9 12 15 5 E/p (kV.cm -1 .bar -1 ) 1 V.cm-1.Torr-1 E/p (V.cm -1 .Torr -1 ) 4 Theor. Gain 0 0,3 0,6 0,9 1,2 1,5 1,8 1.05 bar Signal amplitude (mV) 1.33 V.cm-1.Torr-1 6000 1.3 bar 3 E/p in the Gain 2.0 bar 4500 collecting region 2 2.5 bar 3000 3.0 bar 1 1500 0 0 0 0,3 0,6 0,9 1,2 1,5 1 1,5 2 2,5 3 Pressure (bar) E/p (kV.cm -1 .bar -1 ) 10
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Experimen Ex perimental tal Tests sts wi with h Alpha pha Particle ticles Energy Resolution vs E/p MCA spectra 15 13 5000 1.05 bar E/p anode 4.95 5.49 6.04 2 bar 4000 11 R % • Counts R% improves with 3000 9 3 bar E/p at the anode 2000 7 surface above 1000 E/p at the anode surface ionization 5 0 threshold 2 4 6 8 10 12 0 20 40 60 80 100 E/p (V.cm -1 .Torr -1 ) MCA Channel 15 1.05 bar 5000 E/p Collect. 13 4000 0.84 Counts 1.021.11 2 bar 11 • 3000 R% improves with R % 3 bar 2000 E/p in the collect. 9 1000 slightly above 7 E/p in the collecting region 0 scintillation 5 0 20 40 60 80 threshold 0,6 0,8 1 1,2 1,4 1,6 MCA Channel E/p (V.cm -1 .Torr -1 ) 11
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Ex Experim perimental ntal Tests sts with h Alpha pha Parti ticl cles es Simulation and First Experimental Measurements 700 Best R% for alpha particles (experimental) P = 1,35 bar (Xe) Very first result: 600 T = 295 K pure Xe 500 R = 6.8% (for 4.486 MeV) Counts 400 R(FWHM) ~10 10% 300 200 100 0 We can see a trend towards R=5.6% 60 110 160 210 260 310 360 410 460 510 Channel 15 How far are we from the energy resolution 13 (R) limit for the detector with alpha 1.05 bar 11 2 bar particles? R % 3 bar 9 7 Expected 5 Limit 5.6% 2 4 6 8 10 12 E/p (V.cm -1 .Torr -1 ) 12
André Cortez - Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy) Experim Ex perimental ntal Tests sts with h Alpha pha Parti ticl cles es Simulation and First Experimental Measurements 700 Factors contributing for the Radiation not P = 1,35 bar (Xe) Very first result: 600 Energy Resolution limit monoenergetic T = 295 K pure Xe 500 Counts 400 R(FWHM) ~10 10% 𝐹𝑂𝐷 2 300 1 + σ 𝑟 𝑆 = 2,355 𝐺 𝑜 + 1 𝑜 × 𝐾 + 1 + σ 𝑜 2 𝑓 + 200 𝑂 𝑂 𝑓 𝐻 𝑟 𝑜𝐻 𝑜 𝑇 100 0 e- photosensor electronics energy ampl. 60 110 160 210 260 310 360 410 460 510 20 Channel 15 15 R % 13 10 1.05 bar 11 2 bar R % 5 3 bar 9 Expected 0 Limit 7 Gain 0 10 20 30 5 Experimental Radiation monoenergetic R = 6.8% (for 4.486 MeV) 2 4 6 8 10 12 G=30 Theor. limits R = 2.73% (for 662 keV) E/p (V.cm -1 .Torr -1 ) R = 4.8% (for 4.486 MeV) 13
3. Co Conclus lusion ion and d Future ture Wo Work Pisa Meeting on Advanced Detectors 2018, May 27- June 2, 2018 - Isola d’Elba (Italy)
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