1. UM PPS Lab Activities - HV Readout Long Run - Single Source Saturation Test PPS meeting April 30, 2012

2. Waveforms from 1 Run Last Week 4/30/2012UM PPS Activities2

3. HV Readout Long Run Setup HV board with 11 lines [90,100] at 815V 7 out of 11 lines with the circuitry to read them out 4 consecutive HV lines 94-97 connected to the DRS Signal attenuation of 32 dB (40 times on amplitude) Source sitting on top of the 1 mm slit graphite collimator aligned over a single HV line (#96) DRS threshold very low (60 mV) so that no matter what line had a pulse, the trigger line fired (Fan-in/Fan-out not OK)  at the analysis lever a much harder threshold (200 mV) was used to select real hit-lines Trick: DRS channel 3 signals is always smaller so 32  30 dB 4/30/2012UM PPS Activities3

4. Number of HV Pulses/Event 4/30/2012UM PPS Activities4 125 2

5. HV Pulses Multiplicity per Channel 4/30/2012UM PPS Activities5 Last week result on the left quite different from this long run: now almost only the closest line has hits, and they have a comparable rate. Important to check with a larger number of lines (small improvement the same test with the source on one of the two extreme lines)

6. HV Pulse Amplitude 4/30/2012UM PPS Activities6 The trigger line (#3) has larger amplitude pulses (and #4 smaller)

7. HV Pulse Rise Time (10%-90%) 4/30/2012UM PPS Activities7

8. HV Pulse Width 4/30/2012UM PPS Activities8

9. HV Pulse Pseudo-Charge=|A|*W 4/30/2012UM PPS Activities9

10. Time Between Events 4/30/2012UM PPS Activities10 Why this structure?

11. Saturation Test Saturation: rate of incoming ionizing particles larger than the inverse of the pixel recovery time (R HV *C pixel ) limiting the number of discharges PDP geometry fixes C pixel measured ~10pF, and with HV quench resistor 200 MΩ  RC~ 2ms  max rate O(kHz) Sources measured with a Geiger counter after one layer of glass: (1R=2.58*10 -4 C/kg ~2.1*10 9 ion couples) – 106 Ru~130 mR/h ~7 ·10 4 ions/sec – 90 Sr~170 mR/h ~ 10 5 ions/sec over the entire source area ~1.3 cm 2 (pixel ~1.5 mm 2 ) Idea: single HV line x 4 RO lines increasing the HV to maximize the probability of a plasma discharge in the gas. Above a certain threshold higher voltage should not produce more hits Background events/rates are measured without any source and the data runs are only with 106 Ru 4/30/2012UM PPS Activities11

12. Test with R(HV)=200 MΩ 4/30/2012UM PPS Activities12 Based on the fit results at R(HV)=200 MΩ with C(pixel)=10 pF  RC= 2 ms  saturation @ 500 Hz reached at 1900.6 V

13. Test with R(HV)=1 GΩ 4/30/2012UM PPS Activities13 Behavior not very linear. Hint of saturation at HV>930V (different HV line but same rate as before once R HV =200 MΩ s used)

14. Extended Test with R(HV)=1 GΩ 4/30/2012UM PPS Activities14 The behavior seems more linear (except the first points) and the hint of saturation at HV>930V has disappeared

15. Full Test with R(HV)=1 GΩ 4/30/2012UM PPS Activities15 Second set of points the day after: no hints of saturation! Jump of background events more and more important at higher HV

16. No Saturation. Really?! 4/30/2012UM PPS Activities16 The ratio of the data rates with the two R HV values agrees with the ratio of the maximum rates based on the recovery time  we were saturated the whole time!

17. Conclusions The HV readout long test shows that almost always only one line has a pulse (are the nearby dead?) A few features (like ΔT between events) not yet understood Increasing the HV maybe/likely – increases the active pixel area – increases the active distance in the gas gap to have plasma discharges – reduces the recovery voltage to have a new discharge (only for low values of HV it is needed more than one recovery time to have back the line to a voltage high enough to produce another plasma discharge) To test the saturation effect we will keep the voltage fixed and just change the quench resistor. We expect that starting from low R HV the rate will increase until a certain value after which it is constant 4/30/2012UM PPS Activities17