1. UM PPS Lab Activities PPS meeting October 9 and 16, 2012

2. A Gas Problem Last two panel filled (VPE and SP1) and the old VPD (Feb14, 2012) failed the same way: no response to the source until ~2kV where we see constant discharge Problem individuated in the gas line allowing air into the gas mixture and fixed (one loose connection) Reviewed gas filling procedure to minimize air contamination in the panel SP1 re-baked and re-filled (99%Ar 1%CO 2 ) and tested OK: clear response to the source at HV~100V below the same gas mixture in a larger panel October 9 & 16, 2012UM PPS Activities2

3. More On Preparing Panels VPE re-baked and filled with 99%Ar 1%CF 4 VPD re-baked and filled with 100%CF 4 Next Panel will be filled with 90%Ar 10%CF 4 Prepared the HV card for testing SP1 (1mm pitch panel); Curtis glued the holders, to be cut a little more Preparing a large RO card for TAU (attenuation x100) Received six 1mm pitch panels and 6 at 0.6mm and we are working to prepare – Gas connection (the valve cannot be mounted on top) – RO/HV card (smaller connector, new PCB,...) Curtis and Ethan are working on the gas mixing station. Goal: fill our bottles with our gas mix. Start with ArCO 2, inexpensive and comparable with the pre-mixed 1% and 7% CO 2. October 9 & 16, 2012UM PPS Activities3

4. Photo-Sensitivity October 9 & 16, 20124UM PPS Activities Counter test (threshold -150 mV) out of 15 adjacent HV x 24 RO lines VPA (600 Torr 99%Ar 1%CO 2,filled Feb 14, 2012) A)Lights OFF + window closed + box cover 37112 +- 193 CPM B)Lights ON + window opened + box cover 36915 +- 192 CPM C)Lights OFF + window opened + NO box 41448 +- 203 CPM D)Lights ON + window closed + NO box 48203 +- 220 CPM E)Lights ON + window opened + NO box 48117 +- 219 CPM F)Lights ON + window opened + covered top&bot 38246 +- 220 CPM G)Lights ON + window opened + covered top 39895 +- 200 CPM H)Lights ON + window opened + covered bottom 40097 +- 200 CPM Other measurements when we will get the 60 CO source, but a very different photon energy (1.17 and 1.33 MeV).

5. Photo-Sensitivity Comment The box over the panel shields it from the light (same result A and B) The window is far away: room lights OFF (test C)  window responsible for ~12% increment on CPM, but when the lights are ON (D and E) already bust the #hits by ~30% and the addition of the window seems negligible (E Vs. D) Covering both large sides (F) of the panel with an opaque material (even leaving the sides exposed) reduces the count to values close to the no lights configuration. The little areas not covered are likely responsible for the difference in rate between no lights (A and B) and very limited light (F) Covering either the top or the bottom (G and H) surprisingly does not change very much the result of the measurement with both sides covered. One would expect to have a rate between the 37K CPM without lights (A and B) and 48K CPM with full illumination (D, E). October 9 & 16, 2012UM PPS Activities5

6. Noise Runs Test Setup October 9 & 16, 2012 Two noise runs with the Ni-Ni Vishay Panel “A” (VPA) filled at 600 Torr on Feb 14, 2012 with 99%Ar 1%CO 2 on 24 RO x 15 HV lines(100 MOhm) #36-50 at 800V RO 24 RO 1 HV 1 HV 80 100. HV128 Pickoff card 100x attenuation R HV =100 MΩ VPD 600 Torr Ar:CO 2 99%:1% Filled Feb 29, 2012 Discriminator -150 mV OR TTCvi Trigger RO lines 1-24 CSM TTC Fiber Mezzanine (100x attenuation) DAQ GOL Fiber 6UM PPS Activities

7. Longer Noise Runs October 9 & 16, 2012 72858= Noise Run (Initial, burn-in) 72860= Noise Run (light off, after 24h of HV on the same HV lines as 72858) 7UM PPS Activities

8. Run 72858 October 9 & 16, 20128UM PPS Activities

9. Rate in time72858 (ADC>50, same Y-axis) October 9 & 16, 20129UM PPS Activities

10. Event Time 72860 October 9 & 16, 201210UM PPS Activities

11. Rate in Time Run 72860 (ADC>50, same Y-axis) October 9 & 16, 201211UM PPS Activities

12. Multiple 1 st -Hit on the Same Event October 9 & 16, 2012UM PPS Activities12

13. More on Noise VPA(24ROx24HV): counts coincidence/Hodoscope 1/47, 2/76, 3/178, 4/380, 6/906, 8/1040,... 22/4099  initially ~1/50 then ~1/100 and at the end ~1/200  the noise went up so detector dead for longer time BKG: 2.3 KHz (14:00) 2.55 KHz (17:00) 2.93 kHz (8:00) R=100 MΩ x C~10pF  ΔT~1ms, likely 2/3 times for HV recovery, enough for ion drift, meta-stables... We can have high BKG in a single trigger if there are “strings” of hits (from other HV lines!). A veto for t<<RC won’t change the rate, but eventually suppress other hits close in time (charge spreading) The 24-fold OR formatted 1μs wide and used as veto for the OR itself. October 9 & 16, 2012UM PPS Activities13 24HV12 HV every other12 HV every other‘ NO veto20.72,18124.512529.068.8 Veto21.61,1159.654.914.535.0

14. Multiple Hits on the Scope October 9 & 16, 2012UM PPS Activities14 NIM OR signal: double hits often ~700-1000 ns before the trigger pulse! Hold ~50 ns on the scope  if two triggers are closer than 50ns, only the first is recorded and the next one sees the missing hits as pre-hits! A single RO line has the same 1μs separation! With 2 and 3 HV lines no double hits seen! With 4 HV lines every other (or at least 5 close by) many of them around 300ns and 800-1300 ns

15. Possible Explanation The ion drift is too slow to explain the peak at 300 ns: v(Ar-ion)~200 times smaller v(e)~50 μm/ns, so V(Ar-ion)~250 μm/us  to the next cell neighbor (Δx~1mm) in around 4 μs, one order of magnitude more than measured (and double time with HV every other line) Hypothesis: UV photons spread. Why are needed three or more HV lines are connected? Argue/guess: since the capacitive coupling of the pixel reach a “saturation” after 5-6 lines per side, a discharge in one line affects also the coupled ones and its needed to go further away to have a fully active line. Photon propagation time negligible, but the streamer formation can take a few hundred ns and could explain the peak after 300 ns. This time is gas dependent, a faster gas (ex CF 4 ) should show a much closer secondary pulse. But, even more important, the two gasses have a different cross section of production and recombination of UV photons, so we may even not see at all the extra pulses. October 9 & 16, 2012UM PPS Activities15

16. More to come Modified Minidaq code to read out more than 1 pulse per channel (not just the first) Now modifying the analysis code to make the plots October 9 & 16, 2012UM PPS Activities16

17. Trying to See Cosmic Rays (Again) October 9 & 16, 2012UM PPS Activities17