111 Development of Plasma Panel Based Neutron Micropattern Detectors Yan Benhammou Tel Aviv University for the PPS Collaboration Oct 15, /10/13Y. Benhammou Tel Aviv University

2222 Collaborators University of Michigan, Department of Physics Robert Ball, J. W. Chapman, Claudio Ferretti, Daniel Levin (PI), Curtis Weaverdyck, Riley Wetzel, Bing Zhou Integrated Sensors, LLC Peter Friedman (PI) Oak Ridge National Laboratory, Physics Division Robert Varner (PI), James Beene Tel Aviv University (Israel), School of Physics & Astronomy Yan Benhammou, Meny Ben Moshe, Erez Etzion (PI), Yiftah Silver General Electric Company, Reuter-Stokes Division (Twinsburg, OH) Kevin McKinny (PI), Thomas Anderson Ion Beam Applications S.A. (IBA, Belgium) Hassan Bentefour (PI) 14/10/13Y. Benhammou Tel Aviv University

3333 Outline Motivation Plasma panel operational principles and description Neutrons detection Summary 14/10/13Y. Benhammou Tel Aviv University

444 Motivations Hermetically sealed – no gas flow – no expensive and cumbersome gas system Over 40 years of plasma panel manufacturing & cost reductions ( $ 0.03/cm 2 for plasma panel TVs) Potential for scalable dimensions, low mass profile, long life – meter size with thin substrate capability Potential to achieve contemporary performance benchmarks – Timing resolution  approx 1 ns – Granularity (cell pitch)  µm – Spatial resolution  tens of µm Potential applications in – Nuclear and high energy physics, medical imaging, homeland security, etc 14/10/13Y. Benhammou Tel Aviv University

5555 TV Plasma Panel Structure A Display panel is complicated structure with – MgO layer – dielectrics/rib – phosphors – protective layer 14/10/13Y. Benhammou Tel Aviv University

6666 TV Plasma Panel Structure For detector, a simplified version with readout & quench resistor – No MgO layer – No dielectric/rib – No phosphors – No protective layer 14/10/13Y. Benhammou Tel Aviv University

777 Commercial Plasma Panel Columnar Discharge (CD) – Pixels at intersections of orthogonal electrode array Electrodes sizes and pitch vary between different panels 14/10/13Y. Benhammou Tel Aviv University 220 – 450 µm

88888 Principles of Operation Accelerated electrons begin avalanche Large electric field leads to streamers Streamers lead to breakdown - roughly follows Paschen’s law. “A Theory of Spark Discharge”, J. M. Meek, Phys. Rev. 57, 1940 anode cathode Charged particle track HV(-)  M  Gas volume in pixel 250 µm -1mm 50 µ m -1mm Gas gap becomes conductive Voltage drops on quench resistor E-field inside the pixel drops Discharge terminates 14/10/13Y. Benhammou Tel Aviv University

9999 Modified Commercial Panel (fill-factor 23.5%, cell pitch 2.5 mm) “Refillable” gas shut-off valve for R&D testing 14/10/13Y. Benhammou Tel Aviv University

10 Signals from Panel 1.Signals amplitudes: volts 2.Good signal to noise ratios. 3.Fast rise times O(ns) 4.Pulse shape uniform for a given panel design  pulse from Xe fill 2003, tested 2010  panel sealed & tested in 2013, pulse from neutron source & 3 He fill 30 V 14/10/13Y. Benhammou Tel Aviv University 1 mm electrode pitch 2.5 mm electrode pitch

Neutron Detection in collaboration with GE, Reuter-Stokes 14/10/13Y. Benhammou Tel Aviv University11 Objectives: high efficiency neutron detectors with high  rejection develop alternate to 3 He as neutron interaction medium This test: explore PPS as a general detector structure for converting neutrons using thin gap 3 He gas mixture Gas fill: 80% 3 He + 20% CF 4 at 730 Torr Panel: 2.5 mm pitch large panel used for CR muons Instrumented pixels = 600, Area: 6 in 2 Method: irradiate panel with thermal neutrons from various sources high activity (10 mrem/hr) gammas conduct count rates experiment with & w/o neutron mask plates.

14/10/13Y. Benhammou Tel Aviv University12 neutron sources 252 Cf, 241 Am-Be, 239 Pu-Be nested in stainless capsule, Pb cylinder, high density polyethylene (HDPE) Gamma transparent, neutron blocking plates (~ 0.1% transmission )  PPS panel Setup

Signal from neutrons 14/10/13Y. Benhammou Tel Aviv University13 Pulse “arrival” time (includes arbitrary trigger offset)  = timing resolution (jitter) of the detector ~ 3ns 5 ns

14/10/13Y. Benhammou Tel Aviv University14 Results PPS panel Neutron blocking plate neutron source ( 252 Cf ) Background subtracted data is neutrons only efficiency plateau Background:  from source

results GE Geant4 simulation of the neutron capture rate based on source activity: 0.70 ± 0.14 Hz PPS measured rate: 0.67 ± 0.02 Hz 14/10/13Y. Benhammou Tel Aviv University15 Approximately 100% of the captured neutrons were detected

14/10/13Y. Benhammou Tel Aviv University16 PPS panel 3x10 5  /sec at instrumented region  source ( 137 Cs ) Reasonably good  rejection before any optimizations offered by: thin substrates lower gas pressure thinner metallization Improving internal dielectrics around pixels VPE HV (V)  detection rate Hz  efficiency e e e-05  Rejection

14/10/13Y. Benhammou Tel Aviv University17 Spatial Position PPS panel blocking plate with 5 mm slit neutron source ( 239 Pu-Be)

18 Summary We have demonstrated functioning of modified plasma displays as highly pixelated arrays of micro-discharge counters – Sensitive neutrons [with appropriate conversion ( 3 He ) ] & high  rejection – Timing resolution less than 3 ns – Spatial response at level of pixel granularity – New PPS devices start to be designed to replace the He-3 panel tested using B-10 and Gd-157 conversion layers. They should use much thinner substrates to improve gamma/neutron discrimination ratio. Should be ready next year. 14/10/13Y. Benhammou Tel Aviv University

19 Microcavity-PPS 14/10/13Y. Benhammou Tel Aviv University

20 Microcavity Concept 20 E-field glass Equipotential lines COMSOL simulation: 14/10/13Y. Benhammou Tel Aviv University radial discharge gaps cavity depth  longer path lengths individually quenched cells isolation from neighbors

21 Microcavity Prototype (Back Plate) Via Plug 14/10/13Y. Benhammou Tel Aviv University

22 Position Sensitivity 14/10/13Y. Benhammou Tel Aviv University22

23 Collimated Source Position Scan Motorized X-Y tableTest Panel Light-tight, RF shielded box 1 mm pitch panel 20 readout lines 1.25 mm wide graphite collimator 106 Ru collimated source 14/10/13Y. Benhammou Tel Aviv University

24 Source Moved in 0.1 mm Increments (1 mm pitch panel) 14/10/13Y. Benhammou Tel Aviv University

25 PPS Position Scan Mean fit for β-source moved in 0.1 mm increments * *Electrode Pitch 1.0 mm Centroid measurement consistent with electrode pitch 14/10/13Y. Benhammou Tel Aviv University

26 PPS Proton Test Beam March 2012 IBA ProCure Facility - Chicago 14/10/13Y. Benhammou Tel Aviv University

27 Beam energy 226 MeV, Gaussian distributed with 0.5 cm width Proton rate was larger than 1 GHz on the entire spread of the beam IBA Proton Beam Test 14/10/13Y. Benhammou Tel Aviv University

28 Position Scan Two position scans (panel filled with 1% CO 2 in Ar at 600 Torr) – 1 cm steps - using brass collimator with 1 cm hole, 2.5 cm from beam center – 1 mm steps with 1 mm hole directly in beam center Rate of protons thru 1 mm hole in center of beam was measured at 2 MHz The Panel 14/10/13Y. Benhammou Tel Aviv University

29 1 mm Scan Number of hits per channel Reconstructed centroid of hit map vs. PDP relative displacement with respect to the panel’s initial position 14/10/13Y. Benhammou Tel Aviv University

30 PPS Cosmic-Ray Muon Results 14/10/13Y. Benhammou Tel Aviv University

31 Cosmic Muon Measurement Setup 30 HV lines 24 RO channels Trigger is 3” x 4’’ scintillation pads 14/10/13Y. Benhammou Tel Aviv University

32 Time Spectrum Pulse “arrival” time (includes arbitrary trigger offset)  = timing resolution (jitter) of the detector We repeat this measurement with various gases and voltages Ar / 1% CF4 at 730 Torr 1100V 14/10/13Y. Benhammou Tel Aviv University  = 40.1  0.9

Time Spectrum 33 Ar / 1% CF 4 at 730 Torr 14/10/13Y. Benhammou Tel Aviv University

14/10/13Y. Benhammou Tel Aviv University34 Timing Resolution using 65% He 35 % CF4 at 730 Torr HV =1290 V  ~ 10 ns trigger time subtracted; arbitrary cable offset

PPS Muon Test Beam November 2012 H8 at CERN

36 Setup 180 GeV BEAM 2 scintillation pads 4 cm 2 each Ni-SnO 2 PPS Ar / 7% CO Torr HV = 1090 V 16 channels 8 HV lines 100 MΩ quenched Panel active area is 2 cm x 4 cm ANDOR AND 14/10/13Y. Benhammou Tel Aviv University

37 Time Resolution Timing resolution with Ar-CO 2 better than 10 nsec Geometrical acceptance times efficiency ≈ 2% (pixel efficiency is much higher). Did not have beam time to optimize or even raise the voltage! Active area fill-factor for PPS detector is 23.5% 14/10/13Y. Benhammou Tel Aviv University