Direct charge digital readout of dual phase Time Projection Chambers with GridPix

1. Direct charge digital readout ofdual phase Time Projection Chambers with GridPix M. Alfonsi, N. van Bakel, A. P. Colijn, M. P. Decowski, H. van der Graaf, R. Schön, A. Tiseni, C. Tunnell • MPGD 2013 Conference,Zaragoza July 1-4, 2012

2. The GridPix detector • Micro-Pattern Gaseous Detector with pixel readout • Aluminum mesh supported by pillars (50 µm gap) • Wafer post-processing (MEMS) • Timepix readout (256x256 pixels, 55 µm pitch) • 4-8 µm resistive layer (spark protection) M. Alfonsi

3. The GridPix detector • Micro-Pattern Gaseous Detector with pixel readout • Aluminum mesh supported by pillars (50 µm gap) • Wafer post-processing (MEMS) • Timepix readout (256x256 pixels, 55 µm pitch) • 4-8 µm resistive layer (spark protection) • Single electron detection efficiency > 98% • < 20 µm spatial resolution • Time coordinate (µTPC) • Low noise (no dark counts) M. Alfonsi

4. Dual phase noble gas TPC • Prompt light (S1) is collected by photodetectors arrays, electrons drift to liquid surface • Charge is converted to light in the gas phase by proportional scintillation (S2) • Time Projection Chamber: Z from S2 – S1 time delay • S1/S2 ratio: large discrimination power between electronic and nuclear recoils M. Alfonsi

5. Direct charge readout • Within the DARWIN Consortium [arXiv:1012.4767], we investigate GridPix as direct charge readout • High spatial resolution • digital readout approach(high energy resolution at few e-) • Low noise (no dark counts) • Small device, mainly silicon, manufacturing processes: • Radiopurity • Low outgassing M. Alfonsi

6. Digital readout approach M. Alfonsi

7. Electroluminescence gain • Energy deposits from nuclear recoils up to 40 keV(e.g. Dark Matter searches) ~ few to 200 ionization electrons (depending on setup) make the S2 M. Alfonsi

8. Electroluminescence gain • Energy deposits from nuclear recoils up to 40 keV(e.g. Dark Matter searches) ~ few to 200 ionization electrons (depending on setup) make the S2 • Fluctuations to S2 due to: • Electroluminescence gain (proportional) • Light Collection Efficiency & PMT quantum efficiency (5-20% typical) Xenon Gain 31.4sigma 7.5 M. Alfonsi

9. Electroluminescence gain • Energy deposits from nuclear recoils up to 40 keV(e.g. Dark Matter searches) ~ few to 200 ionization electrons (depending on setup) make the S2 • Fluctuations to S2 due to: • Electroluminescence gain (proportional) • Light Collection Efficiency & PMT quantum efficiency (5-20% typical) Xenon Gain 31.4sigma 7.5 Xenon Gain 31.4sigma 7.5 M. Alfonsi

10. Digital readout with pixels • Counting the number of hit pixels M. Alfonsi

11. Digital readout with pixels • Counting the number of hit pixels • Caveat: • Every electron in a different hole • 100% single electron detection efficiency • (1) depends on pixel pitch and diffusion along the drift distance in the vapor phase. • Toy MC for the case of xenon (diffusion coefficients from Garfield/Magboltz) M. Alfonsi

12. Pixel pitch & diffusion in xenon Pressure 1.0757 bar absolute • 10kV, 55µm pixel pitch, 1.0 cm path M. Alfonsi

13. Pixel pitch & diffusion in xenon Pressure 1.0757 bar absolute • 10kV, 55µm pixel pitch, 1.0 cm path • 10kV, 55µm pixel pitch, 3.0 cm path M. Alfonsi

14. Pixel pitch & diffusion in xenon Pressure 1.0757 bar absolute • 10kV, 55µm pixel pitch, 1.0 cm path • 10kV, 55µm pixel pitch, 3.0 cm path • 2kV, 55µm pixel pitch, 1.0 cm path M. Alfonsi

15. Pixel pitch & diffusion in xenon Pressure 1.0757 bar absolute • 10kV, 55µm pixel pitch, 1.0 cm path • 10kV, 55µm pixel pitch, 3.0 cm path • 2kV, 55µm pixel pitch, 1.0 cm path • 2kV, 55µm pixel pitch, 1.0 cm path,95% efficiency M. Alfonsi

16. Application to large areadual phase TPC ? M. Alfonsi

17. Large Area dual phase TPC? M. Alfonsi

18. Large Area dual phase TPC? • Maybe! • Recent production on 8” wafers prospects industrialization and large volume at reduced cost. M. Alfonsi

19. A small-sizehigh-impact application M. Alfonsi

20. Light & charge yield in xenon • The response of the medium, i.e. the scintillation light (Ly) and the ionisation charge (Qy) yield, must be measured for electronic and nuclear recoils Scheme from Manzur et al., Phys.Rev.C81 (2010) 025808 M. Alfonsi

21. Light & charge yield in xenon • The response of the medium, i.e. the scintillation light (Ly) and the ionisation charge (Qy) yield, must be measured for electronic and nuclear recoils From G. Plante et al., arXiv:1104.2587 Adapted from Manzur et al., Phys.Rev.C81 (2010) 025808 M. Alfonsi

22. Ly & Qy measurements Dedicated measurements: • neutron elastic scattering for nuclear recoils • Compton scattering for electronic recoils • small size noble liquid target detector θ Neutron / Gamma generator M. Alfonsi

23. Ly & Qy measurements Dedicated measurements: • neutron elastic scattering for nuclear recoils • Compton scattering for electronic recoils • small size noble liquid target Systematic uncertainty from the unknown position within target or double scatters. • GridPix adds high resolution position reconstruction and digital charge readout! detector θ Neutron / Gamma generator M. Alfonsi

24. Xe TPC @ Nikhef M. Alfonsi

25. Measurementswith GridPix M. Alfonsi

26. Cryogenic robustness M. Alfonsi

27. New geometries under test New geometries for the dykes (the “perimeter support” for the mesh). Pillars with additional extended structures. (NIM A718 (2013) 446-449) Dummy wafers (full anode instead of Timepix) under test. M. Alfonsi

28. Pure nobles gasses • Measurements at CERN in 2011 in a gaseous and dual phase argon TPC • Measurements at Nikhef in a gaseous argon or xenon TPC Nikhef CERN 2011 M. Alfonsi

29. Pure noble gasses • Stable operation with a reasonable charge amplification only with non ultra-pure gas (e.g. industrial standard argon 99.997%). • With argon 99.9999% or xenon 99.999% we observe a sharp transition between a too small gas amplification region and the discharge regime M. Alfonsi

30. Future plans M. Alfonsi

31. Towards full ceramics • Full ceramics devices under study: • SiO2 as insulator • Si-rich Si3N4as the resistive material • Matching thermal expansion properties • Low Outgassing and high radiopurity M. Alfonsi

32. Towards full ceramics • Full ceramics devices under study: • SiO2 as insulator • SiRN is the resistive material • Matching thermal expansion properties • Low Outgassing and high radiopurity • A resistive grid can limit the charge available for a spark to only one cell. • An embedded conductive network can distribute voltage uniformly M. Alfonsi

33. In the meanwhile… • A more sensitive pixel electronics would be helpful • Recent literature keeps emphasizing that closed structure and confined amplification region are the key of success • Producing and testing GridPix with any GEM-like or other specific amplification structure can be time / money consuming • “Test the water” placing the amplification structure very close to a bare TimePix • Investigate some specific quencher that does not spoil the scintillation signal M. Alfonsi

34. Thanks for your attention! M. Alfonsi

35. Spare slides M. Alfonsi

36. CERN 2011 • In collaboration with the ETH Zurich: • gaseous warm / cold argon TPC. • dual phase argon TPC. • IEEE NSS-MIC Conf. Rec. 2011, 92-98 M. Alfonsi

37. CERN 2011: cold argon gas The amplification of the GridPix can be verified with the light detected by PMT. Average waveform (A.U.) M. Alfonsi

38. CERN 2011: cold argon gas Average waveform (A.U.) Average waveform (A.U.) Average waveform (A.U.) Average waveform (A.U.) M. Alfonsi

39. M. Alfonsi