Daniel S Levin UM/TAU/IS/ORNL meeting with GE Sept 27, 2012 University of Michigan

1. PPS Overview & Experimental Results Daniel S Levin UM/TAU/IS/ORNL meeting with GE Sept 27, 2012 University of Michigan D.S. Levin University of Michigan

2. Outline • Overview of desired PPS attributes • Basic physics of PPS • Proof-of-principle experiments & Establishing basic attributes • Laboratory setups and prototype testing • Hit rates with source and background • Signals, pixel capacitance, HV, Pashen potential etc • Cosmic Muons • Saturation measurement • Spatial measurements • Test Beam D.S. Levin University of Michigan

3. Plasma Panel Detector Overview • Inherits many operational and fabrication principles common to PDPs: • A dense micro-array of gas discharge cells or pixels • Pixels bias for gas electrical discharge- Geiger mode operation • Pixels are enclosed in hermetically-sealed glass panel • Uses non-reactive, radiation-hard materials: • glass substrates, refractory metal electrodes, inert gas mixtures. • Anticipate eventual device fabrication as low-mass detectors • Ahigh gain and inherently digital device • Potential for: • < 1 ns response times • high granularity • Position resolution < 100 um • low power consumption • large area with low cost • 2D readout D.S. Levin University of Michigan

4. Plasma Television Display Panel (PDP) • As a detector PPS remove or replace specific elements: • No phosphors • No MgO layer • No dielectric layers • We add a quench resistor to the pixels that terminates the discharge D.S. Levin University of Michigan

5. Single pixel: Principles of operation (-) High Voltage Muon track cathode anode 50-100  D.S. Levin University of Michigan

6. Single pixel: Principles of operation (-) High Voltage Muon track cathode Ionizing particle creates ion pair clusters along track Cluster formation dictated by Poisson statistics Cluster statistics: ni= >1 ion-pair. avg is about 3, with long exponential tail anode 50-100  D.S. Levin University of Michigan

7. Single pixel: Principles of operation (-) High Voltage Muon track cathode Electron drift & acceleration in initiates avalanche High E –fields lead to streamers & gas breakdown according to Paschen’s Law : + ++ ++++ +++ P= pressure d= gap size V=voltage a,b = gas specific parameters - -- ---- -- anode 50-100  D.S. Levin University of Michigan

8. Paschen discharge potential Wikipedia: Paschen entry. Minimum voltage occurs when Small variations in Penning gas mixtures can dramatically affect breakdown voltage A.K. Bhattacharya, GE Company, Nela Park, OH  Phys. Rev. A, 13,3 (1975) D.S. Levin University of Michigan

9. discharge cell: important gas processes primary ionization ion ejected electron Metastable ejection metastable generation Excitation Penning ionization photon emission Image from: Flat Panel Displays and CRTs (Chapter 10)    L. Tannas, Jr, D.S. Levin University of Michigan

10. Electrical description start with simplified schematic of single PPS discharge cell cathode - Rquench + anode Cpixel signal Rterm HV Supply During discharge cell becomes conductive The E field drops, discharge self-terminates The quench resistance on each pixel (or pixel chain) : impedes E field rise until ions and meta-stables are neutralized maintains HV on all other cells so that they are enabled for hits D.S. Levin University of Michigan

11. More realistic cell model include stray capacitances, line resistance, self inductance (More details in Robert Varner’s presentation) {ResNi} Cpixel D.S. Levin University of Michigan

12. Proof-of-principle & other tests with modified PDPs Formation of discharge above Paschen potential Self-termination Response to a source Gas hermetic envelope Signal characteristics Rate from radioactive source vs background Discharge spreading Response with various gases Detection of CR Muons Position sensitivity along a one coordinate axis Proton beam tests Response to multiple, simultaneous sources Yiftah Silver talk D.S. Levin University of Michigan

13. Lab setup collimator 90Sr 106Ru Panel A: Xe @ 650 torr Filled: Aug 2003 Panel B: Ar+ CO2 (7%, 1%) 22 cm SnO2 Ni Rout High Voltage Quench 50  Termination Discriminator @ 2-4 V Lecroy 574A bandwidth 1 GHz

14. Demonstration using Commercial DC-PDPs glass SnO2 280 m cathodes - - - Discharge gap 220-340 m dielectric Ni anode 800 m + + + + + + + + + glass E field at pixel (COMSOL calculation) D.S. Levin University of Michigan

15. proof-of-principle tests • At critical (Paschen) voltage (~700 V) discharges appear in Xe. • O(ns) rise time (for ~ 1 mm dimensions) • Large amplitude indicates discharge of 5-10 pf effective capacitance • Increase voltage  amplitude increase & hit rate increase (next slide) • Observed signals are single pulses  quenching works • Panel filled and sealed in 2003- gas containment works • Clear response to 90Sr (beta) source • Low discharge spreading: 2% to a single neighbor pixel in open structure Signal from Xe filled panel Signal (attenuated) from Ar-CO2 filled panel D.S. Levin University of Michigan

16. Rate Measurements using  source Response to Source vs HV Rate increases as expected with HV Response to source is ~100 Hz with very low background D.S. Levin University of Michigan

17. Rate Measurements using  source Response to Source vsRquench 1/Rquench Rquench Rate increases as expected with HV and depends on Quench resistance High Rquench(high RC time constant) causes pixel to saturate Response to source is ~100 Hz with very low background D.S. Levin University of Michigan

18. Detection Setup of Cosmic Ray Muons Panel tested with CF4 or SF6 at 600, 200 torr PMT1 PMT2 Scaler & waveform digitizer Events triggered with 3-fold coincidence Signals collected with DRS-4 fast waveform digitizer D.S. Levin University of Michigan

19. Arrival Time Measurement of Cosmic Ray Muons D.S. Levin University of Michigan • Both pure CF4 and SF6 gases shows a signal with a very fast response time. • Arrival time is defined with respect to the hodoscope trigger • Timing jitter is 5 ns

20. Detection of Cosmic Ray Muons & Efficiency • About 8% of triggers were associated with signal from the panel • This factor represents a convolution of several factors: • Geometric acceptance  ion-pair probability  intrinsic efficiency net = Ag  AE  P(l,p,r)  (r) = 8 % • Ag = geometric acceptance of pixel (wrt to trigger area*solid angle) • AE = Pixel area enhancement from fringe E field • P(l) = Probability to produce at least one ion-pair at distance R from anode • (r) = efficiency: probability to generate a discharge for ion-pair created at distance R from anode. D.S. Levin University of Michigan

21. Response to two simultaneous sources (setup) Side view Sr90 top Ru106 bottom RO lines HV=815V Top view D.S. Levin University of Michigan

22. Response to two simultaneous sources (setup) HV lines 1 20 100 110 128 RO 24 RO 1 Pickoff card 100x attenuation VPA 600 TorrAr 99%CO21% Filled Feb 15, 2012 Sr90 Ru106 HV=815V R=400 MΩ RO lines 3-6 Scalar Discriminator -150 mV OR Expectation: rate with two sources = sum of the two rates in single mode until the sources starts (partially) overlapping D.S. Levin University of Michigan

23. Response to 2 simultaneous sources (Results) Result: Panel responds independently to each source until they nearly overlap and saturate a line D.S. Levin University of Michigan

24. Summary • Using off-the-shelf commercial Plasma Panels we have demonstrated • Producing fast, self-terminating, high gain pulse • Sensitivity to charged particles betas (also muon, protons) • Good timing jitter using triggered muons • Sensitivity to independent sources • Spatial resolution commensurate with the high granularity of the electrode pitch (Yiftah’s talk) • Panels sealed with gas in 2003 produce signals 9 years later D.S. Levin University of Michigan