UM PPS Lab Activities

1. UM PPS Lab Activities PPS meeting July 18, 2013 Claudio, Curtis, Dan, Riley, Theo

2. He Mixtures Test Recap • VPE He:CF4 90:10 at 730 Torr • small signal (~6mV x 100) and slow (~25 rise time) • At 680V BKG rate << source, but already at 685V they are close • Efficiency(682V)=0.26%, 10 time lower than the worst ArCF4 90:10 • At 682V arrival Time jitter larger than 100 ns • VPE He:CF499:1 at 735 Torr: signal not seen on the scope while varying the HV. • At 335 V current ~ 7μA not stable  at least 1 pixel discharging • At 333.5V current=0 μA • For HV [333.5,335]V current not null but not stable, likely bursts • To be eventually re-tested with the zero attenuation RO card • VPE He:Xe 90:10 at 731 Torr: Bkgdand source rate very similar (1V at the time) • Initial voltage when the current is not null 500V  at 505V bursts • Problem with the long lived Xemetastables • VPE He:Xe 90:10 at 730 Torr: signal not seen on the scope not even with the RO card without attenuation and 1 mV/div. Current not null at 308V • Currently pumping down, sucking and heating VPE to be filled with 90%He 10% CO2 UM PPS Activities

3. Intrinsic Resolution • Basic relationship: σ2Measured = σ2source + σ2intrinsic • The “source” is the convolution of the distributions • primary beta’s at the entrance of the gas volume, that’s after the MS in the glass (in principle this should be part of the intrinsic resolution of the panel)  Geant • secondary electrons from gamma’s radiated by the primary ones, much wider and not irrelevant  plot • Detailed modeling of the collimated source and all the systematics (asymmetric slit, rotational misalignments, vertical separation collimator-panel, …) affecting either 1) or 2) or both • The “intrinsic” is due to: • spreading in the glass (we included in the “source”) • the (pixel) location of the primary electron-ion pair (Riley’s simulation shows a FWHM increase of 300-400 μm) • which pixel actually discharges generating a hit (this contribution would require a knowledge of the full E-field, …) UM PPS Activities

4. MP1 Collimated 106Ru + 8.75 mm Plexiglas ~1/3 of the hits are not primary electrons UM PPS Activities

5. Resolution Open Questions • Why the newer Geant simulations, with a lower energy beta distribution and (hopefully) extra thickness taking into account the metallic electrode and/or dielectric produce a distribution narrower than previous ones ? • How smaller is the width when we go to higher HV? MP1 filled at 600 torr 90%Ar 10% CF4 Position scans give at 860V FWHM~5 mm, at 870V FWHM~4 mm, at 880V FWHM ~3.1 mm. Does higher pressure (forcing higher HV) shrink the typical hit dispersion? • What is the effect of the distance slit-panel? It might affect the width of secondary betas since they are likely produced by gamma conversions near the glass-air interface • How large is the contribution of a misaligned slit? UM PPS Activities

6. VPE 99%Ar 1%CF4 600 Torr 4/20/13 UM PPS Activities

7. Different Fits (Re-binned plot) Landau better than Gaussian. but not good yet. Next Crystal-Ball UM PPS Activities

8. Channel Gaussian Fit Mean Two classes of channels (same result with the geometrical mean). Variation much larger than the spread to be measured  we likely mis-assign the first hit to the wrong channel  we need to measure a channel by channel T0 and correct for it! UM PPS Activities

9. Two Arrival Times Trigger Subtracted UM PPS Activities

10. Arrival Time Trigger Subtracted In these conditions the trigger time subtraction does not improve the arrival time spread! UM PPS Activities

11. Trigger Time 2748 events with Panel hits and Trigger Only 4 with hits and No trigger recorded in the event UM PPS Activities

12. VPE 90%Ar 10%CF4 730 Torr5/7/13 310 events with Panel hits and Trigger 243 with hits and No trigger recorded in the event. Wrong threshold for the trigger channel? UM PPS Activities

13. Arrival Time Trigger Subtracted Only events whit both Panel hit and trigger are present Here the trigger time subtraction helps and σ<10 ns, but still outliers! UM PPS Activities

14. Conclusions • He test to be completed (with 10% CO2). Signals are much smaller and slower than with Ar as host gas. So far the only working mixture is with 10% CF4 • The panel intrinsic resolution result needs still some work: secondary beta’s contribution, HV (and P) dependency and estimation of the systematics • The arrival time dispersion quoted so far from the lab experiment with the 106Ru is overestimated because of the missing trigger time subtraction • Discovered a relevant channel dependence of the arrival time, leading to likely often mis-assigning the first hit of the event. Once measured these channel by channel times and compensated for, we should find smaller arrival time spread • The presence of a large fraction of PPS hits without trigger associated in the event should be understood UM PPS Activities

15. Arrival Time Per Channel UM PPS Activities

16. Two Classes Much Closer UM PPS Activities