Novel Plastic Microchannel-Based Direct Fast Neutron Detection

Transcription

1 Novel Plastic Microchannel-Based Direct Fast Neutron Detection D. Beaulieu, P. de Rouffignac, D. Gorelikov, H. Klotzsch, J. Legere*, J. Ryan*, K. Saadatmand, K. Stenton, N. Sullivan, A. Tremsin Arradiance Inc., Sudbury MA * UNH EOS, Durham, NH Arradiance Inc. 142 North Road, Suite F-15 Sudbury, MA 1776 (8) Tel and Fax 28 Arradiance Corporation. All rights reserved.

2 Outline Microchannel plate (MCP) background Arradiance functional thin film technology Atomic Layer Deposition (ALD) Substrate independent MCP technology Secondary electron emissive films Conductive films Fast neutron MCP detector Concept Functionality Simulation Fast neutron MCP detector experimental Fast neutron MCP detector results Summary and Future Work 2 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary

3 MicroChannel Plate (MCP) Technology Mature (196s) MFG, Expensive, Bulk materials determine performance, High Z content, limited size (<1cm), difficult process control Event counting: >1 7 gain, <.1 c/cm 2 -s noise, high efficiency, <1µm spatial resolution, <5ps rms temporal resolution A. S. Tremsin, et al., Nucl. Instr. Meth. A 58, pp (27) Wiza, Nuclear Inst. & Meth., Vol 162, 1979, Arradiance Corporation. All rights reserved. Confidential and Proprietary

4 ALD MCP Technology MCP performance tied to glass composition ALD: Device optimization is decoupled from substrate. Semiconductor processes & process control. Materials engineering at the nanoscale Functional films composed of abundant,non-toxic materials. Advantages: High conformality (>5:1) Scalable to large areas Digital thickness control Pure films Control over film composition Low deposition temperatures (5-3 C) A Vapor inlets B Deposition region Alternating layers Thin film growth that relies on self-limiting surface reactions Gas A reacts with a surface excess precursor & reaction byproduct removed. Gas B is introduced to the evacuated chamber reacts with surface bound A excess precursor & reaction byproduct removed. Repetition of A B pulse sequence to build film layer-bylayer 4 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary

5 ALD Functional Films: Substrate Independent MCP SE yields >5 possible vs MCP < 3 Conductivity range > 7 orders of magnitude Ohmic conduction, Stable in applied E field, TCR < 1% Gain R (M ) 1 Gain Resistance MCP bias (V) 1 µm pore, Soda Lime glass substrate, 4:1 L/D, R~28 MW 5-1x gain increase vs. commercial MCPs 5 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary

6 Fast Neutron Detection Technology Fast Neutron Hydrogen-rich PMMA MCP Graded Temperature ALD Active films deposition at 14C Proton initiated electron cascade Output pulse electrons Standard readout electronics Recoil Proton Secondary Electrons V 1 V 2 1kV, ultra low current Counts μs per UV power supply specs Time, ms Timing histogram of events detected under 12Hz-modulated UV illumination Arradiance Corporation. All rights reserved. Confidential and Proprietary

7 Fast Neutron Detection Simulation: P1 and P2 Probabilities P1 probability P1 P detection = P 1 * P 2 * P 3 P 1 n-p recoil within the MCP substrate P 2 proton escape into MCP pore P 3 electron avalanche is formed (MCP ~1) P2 Pores are 5 m En = 2MeV Wall thickness ( m) P2 probability MeV neutron, 5 um pores Wall thickness ( m) P1 x P2 probability P1*P2*P3 Pores are 5 m En = 2 MeV Wall thickness ( m) P1 probability Pores are 5 m En = 1MeV P2 probability MeV neutron, 5 um pores P1 x P2 probability Pores are 5 m En = 1 MeV Wall thickness ( m) Wall thickness ( m) Arradiance Corporation. All rights reserved. Wall thickness Confidential ( m) and Proprietary

8 Fast Neutron Detection Simulation: P3 Probability and Event Timing Neutron Detection Stage Signal Amplification Stage Note: P3 Probability for Amplification Stage is 1. Timing for Amplification Stage is < 2 ps Operating at 12V Bias (Average Gain 47) P3 - Probability.9 for 1:1 LD 5 um Pores For 99.9% of events, we should expect a pulse timing uncertainty in coincidence mode of operation of ±1.5 ns For 9% of events, we should expect a pulse timing uncertainty in coincidence mode of operation of < ± 1. ns 8 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary

9 Detector Hardware Experimental Setup 2 & 5 mm PMMA MCP, ~5 µm pores, 2 µm walls, 5 o bias angle installed above a chevron stack of 5:1 L/D MCPs Phosphor screen readout Canberra preamp and postamplifier H-rich MCP Pb-glass MCP Chevron Readout 9 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary

10 Photons Isotope Sources: Experimental Setup Gamma (kev) Am-241 Cs-137 C-6 Cf mq 76 Q 43.7 Q 6, ; 1.33 Flux MCP/s 1.76x x x1 3 ~1 7 Isotopes ~15cm from liquid scintillator detector spectra collected over 11s (real time). Mesytec MPD-4. is used to record PMT data 1 9 Am Gain Pb Reduction of flux by filters Gamma Neutron Photons 1 9 Cs Gain Wax Gamma Neutron No filters 1 9 Cf Gain 1 28 Arradiance Corporation. All rights reserved. Confidential and Proprietary Photons 1 Pb Photons Photons 1 9 Cf-252 1"Pb Gain 2.5 Wax 1 9 Cf "Wax Gain

11 Gamma Isotope Sources MCP Results Summary Counts Co-6 Am Cs-137 isotopic sources Gamma E (ev) QE 1 4.E E E+5 2.6E E E-3 Gain (ADC Volts) PMMA, 2mm, > 1k 5 µm Pores, 2µm wall mm PMMA MCP, 5V bias QE E+ 5.E+5 1.E+6 1.5E+6 Gamma energy (ev) Arradiance Corporation. All rights reserved. Confidential and Proprietary

12 Cf-252 MCP Experimental Results Summary Counts in 96 seconds detected by PMMA MCP only (chevron subtracted) 1 1 5V-V 5V-V 1 5V-V 1 5V-V Counts No filter Gain (ADC Volts) Counts 1 1 1" Pb Gain (ADC Volts) Filter Count rate (cps/detector) no Pb wax 83 QE =.885 n QE = 3.28E-3 n QE well matched to simulation Gain (ADC Volts) Arradiance Corporation. All rights reserved. Confidential and Proprietary Counts " Wax 5V-V

13 D-T Source (Thermo 32) Experimental Setup Polyethylene shielding around the source Filters: Lead (2 ), polyethylene (1, 2 ), borated plastic (1 ) Lead shielding around the detector Source ~3 cm MCPs 5 mm PMMA MCP, ~5 µm pores, 2 µm walls, 5 o bias angle installed above a chevron stack of 5:1 L/D MCPs Arradiance Corporation. All rights reserved. Confidential and Proprietary

14 D-T Source Experimental Results Summary Predicted QE ~.8% P1xP Neutron energy (MeV) Conclusions: 1. QE to 14 MeV neutrons is ~1.2% 2. Believe n and counts are comparable at source settings 3. Timing better than 1.5 s (measurement limited by the source) 4. MCP dark count very low (~.3 c/cm 2 /s) Arradiance Corporation. All rights reserved. Confidential and Proprietary

15 Conclusions and Future Work Functional films Improved performance, substrate independence Emissive Layer - Optimized SE yield and tailored conductivity Conductive layer - Ohmic conduction, Low TCR First Plastic MCP results demonstrated Fast neutron detector demonstration > 1% Neutron detection simulation target 2mm MCP QE=.3 5mm MCP QE=.12 <.1% Gamma detection simulation target Energy dependence QE=9.26x x1-3 Future Work Optimization for Neutron QE > 1% Gamma Sensitivity Energy Sensitivity < 5 kev Demonstrate timing < 1.5ns Arradiance Corporation. All rights reserved. Confidential and Proprietary

16 Acknowledgements Prof. James Ryan Dr. Richard Lanza Arradiance Corporation. All rights reserved. Confidential and Proprietary