GridPix application to dual phase TPCs

1. GridPix application todual phase TPCs Matteo Alfonsi, N. van Bakel, A. P. Colijn,M. P. Decowski, H. van der Graaf, R. Schön, A. Tiseni 6th Symposium on large TPCs forlow energy rare event detection,Paris December 17-19, 2012

2. The GridPix detector • The GridPix is a Micro-Pattern Gaseous Detector made of an aluminum mesh (grid) built over a Timepix, a pixelated CMOS chip. • Gas amplification is produced in the 50 µm gap between the grid and the chip. • The Timepixchip provides readout with a matrix of 256 x 256 pixels, 55 µm pitch.A thin resistive layer protects the chip against discharges. Large TPCs for low energy rare event detection, Paris December 19th, 2012

3. GridPix features • Single electron detection efficiency > 98 % • < 20 µm spatial resolution • Timecoordinate (µTPC) • Low noise electronics: threshold ~1000 electrons Large TPCs for low energy rare event detection, Paris December 19th, 2012

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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

6. Light & charge yield 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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

7. Light & charge yield 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 A. Manzur et al., Phys.Rev.C81 (2010) 025808 • From G. Planteet al., arXiv:1104.2587 Large TPCs for low energy rare event detection, Paris December 19th, 2012

8. 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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

9. 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 Systematic uncertainty from the unknown position within target or double scatters. • GridPix adds high resolution position reconstruction! Large TPCs for low energy rare event detection, Paris December 19th, 2012

10. 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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

11. CERN 2011: cold argon gas The amplification of the GridPix can be verified with the light detected by PMT. Average waveform (A.U.) Large TPCs for low energy rare event detection, Paris December 19th, 2012

12. CERN 2011: cold argon gas Average waveform (A.U.) Average waveform (A.U.) Average waveform (A.U.) Average waveform (A.U.) Large TPCs for low energy rare event detection, Paris December 19th, 2012

13. CERN 2011: damaged grid After filling with liquid argon… The reason of the damage could not easily be inferred (during the warm up? the liquid argon during filling? even before?) Large TPCs for low energy rare event detection, Paris December 19th, 2012

14. Cryogenics robustness We continued with systematic studies of cryogenic robustness(dry atmosphere and fine temperature control). Large TPCs for low energy rare event detection, Paris December 19th, 2012

15. Cryogenics robustness Large TPCs for low energy rare event detection, Paris December 19th, 2012

16. Thermal stress simulation FEM simulations: thermal stress on the gaps between the “dykes” that support the grid along the sides Large TPCs for low energy rare event detection, Paris December 19th, 2012

17. New geometries New geometries for the dykes. Pillars with additional extended structures. (doi 10.1016/j.nima.2012.11.054) Dummy wafers (anode plane instead of Timepix) in production. Large TPCs for low energy rare event detection, Paris December 19th, 2012

18. 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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

19. 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 Large TPCs for low energy rare event detection, Paris December 19th, 2012

20. Gridpix production New production on 8’’ wafer: • Demonstrate industrialization of the production • Cut the cost per device to few hundred euro • Solve the shortage of GridPix  Yield of good quality devices to be improved, defects seem related to scratches on Timepix wafer surface Large TPCs for low energy rare event detection, Paris December 19th, 2012

21. Operation in noble gas Setup in pressured vessel: • Measurements at higher pressure to simulate cold gas. • Possibility to evacuate (turbo-pump) and to bake the vessel. • Equipped with spectrometer to analyse residual gasses. Large TPCs for low energy rare event detection, Paris December 19th, 2012

22. Operation in noble gas Signal on the grid read with a preamplifier: • trigger for the pixel readout • total charge Measurements plan: • Argon 4.7, Argon 6.0 • Xenon • Xenon/methane 98/2 Large TPCs for low energy rare event detection, Paris December 19th, 2012

23. Xe TPC @ Nikhef Original project from Columbia U. and Shangai U. Large TPCs for low energy rare event detection, Paris December 19th, 2012

24. Xe TPC @ Nikhef Large TPCs for low energy rare event detection, Paris December 19th, 2012

25. Xe TPC @ Nikhef Large TPCs for low energy rare event detection, Paris December 19th, 2012

26. Conclusion and prospects • GridPix as direct charge readout of dual phase TPC: • improved energy resolution, low noise, low radioactivity; • improve Ly andQymeasurements. • New geometries robust at cryogenics temperature investigated. First dummy devices in production. • General development on fully ceramic GridPix. • Production on 8’’ wafers • Characterisation of GridPix operation in noble gasses • A dual phase TPC installed soon at Nikhef Large TPCs for low energy rare event detection, Paris December 19th, 2012

27. Acknowledgements • AndréRubbia’s Zurich ETH group, especially FilippoResnati and DevisLussi • B. vd Heijden, H. Boterenbrood, V. v Beveren, J. Rövekamp, B. Munneke, P. d Groen, P. Thobe, F. Hartjes, J. Uher, R. Rosing • Jurriaan Schmitz, YevgenBilevych, Sanser Smits .. and thanks for your attention! Large TPCs for low energy rare event detection, Paris December 19th, 2012

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