1. The GridPix and Gossip gaseous detectors for the ATLAS Upgraded ‘SC’T Harry van der Graaf Nikhef, Amsterdam on behalf of the GridPix/Gossip group ATLAS Tracker Upgrade Workshop Valencia, Dec 12, 2007

2. Si (vertex) track detector GOSSIP CMOS chip Si depletion layer V bias Si strip detectors Si pixel detectors MAPs CCDs Gas: 1 mm as detection medium 99 % chance to have at least 1 e- Gas amplification ~ 1000: Single electron sensitive All signals arrive within 20 ns Cluster3 Cathode (drift) plane Integrated Grid (InGrid) Cluster2 Cluster1 Slimmed Silicon Readout chip Input pixel 1mm, 100V 50um, 400V 50um

3. Wafer post-processing:InGrid InGrid: an Integrated Grid on Si (wafers or chips) perfect alignment of grid holes and pixel pads small pillars Ø, hidden pillars, full pixel area coverage Sub-micron precision: homogeneity Monolitic readout device: integrated gas amplificator Grids Silicon wafer HV biasing Hex / Pillars

4. Full post-processing of a TimePix Timepix chip + Micromegas mesh: Timepix chip + SiProt + Ingrid: Moiré effects + pillars “Uniform” MESA+ IMT Neuchatel CERN Charge mode

5. A “scratch” occurred during the construction of Ingrid; Loose parts removed. Ingrid working!

6. New Ingrid developments and results Process improvement: grids much flatter –Extremely good (record?) energy resolution: 13.6 % FWHM with 55 Fe in P10 –Removal of K β 6.5 keV line: 11.7 % @ 5.9 keV in P10 New wafer masks: hole pitches down to 20 μm with various diameters and gaps –Investigate Micromegas geometry –Test of the ion backflow theory Until now: 1 μm thin Al but can now be increased to 5 μm by electrolysis Expect less damaged from sparks K α escape K β escape 13.6 % FWHM K β -filtered spectrum with Cr foil 11.7% FWHM Gap: 50 μm; Hole picth: 32 μm,Ø: 14 μm

7. setup Next-1,2

8. A “long” cosmic track Timepix + 20 μm thick Siprot + Ingrid drifttime Stable operation in He iC4H10 10 mm cathode @ - 1500 V 14 mm

9. Stable operation in Argon too! After 2 weeks of cosmic event recording, it was time for a definitive assessment whether 20 µm SiProt is enough to protect against discharges… Time mode

10. Gossip: replacement of Si tracker

11. GOSSIP-Brico: PSI-46 First prototype of GOSSIP on a PSI46 is working: 30µm layer of SiProt 1.2 mm Drift gap Uses MicroMegas MicroMegas grid used as trigger We can see tracks

12. Gas: 1.2 mm as detection medium 99 % chance to have at least 1 e- Gas amplification ~ 25,000 in 90/10 Ar/CH 4 : Single electron sensitive All signals arrive within 18 ns Cluster3 Cathode (drift) plane MigroMegas Grid Cluster2 Cluster1 Silicon Readout chip Input pixel 1.2mm, 120V 50um, 430V 50um GOSSIP Basics (PSI-46 Brico specific) Use Pixel chip for readout, use gas layer for detecting MIPs 50µm high support pillars

13. Animated GIF of 100 hits on the PSI46 brico, 30µm SiProt. (if this does not animate, drop the picture into a web browser) 8mm 7.8mm We can see tracks! (Frame # 17 is really great)

14. For tracking, gas is a better detection material than Si: - it is light - primary electrons can simply be multiplied: gas amplification - gas can be exchanged: no radiation damage - gas has a low ε r : with small voxels the source capacity can be small (10 fF) allowing fast, low-noise, and low-power preamps - gas is usually cheap - [high electron mobility: fast signals, high count rates are possible] - ageing: must be solved and must be understood / under control - discharges/sparks: readout system should be spark proof - diffusion: limits max. drift length

15. Tracking of charged particles: principle Gas compared with Si as detector material cheap exchangeable: therefore no radiation damage readout requires [much] less power [thus detector mass] no bias current low source capacity low mass electron multiplication light but: discharges: now solved! chamber ageing Measurement of time and place of a charge signal from detection material Consequences for future experiments: ILC LHC Upgrade (Super LHC) All Gas detectors, followed by calorimeters

16. Un-coated anode Coated anode SiProt: a low T deposited hydrogenated amorphous silicon (aSi:H) layer Up to 50 μm thick films, ~10 11 Ω.cm SiProt protection against: hot spark plasma Too large charge in pixel circuitry [Principle of RPCs] local reduction of E-field: quenching widening discharge funnel: signal dilution increased distance of ‘influention’

17. TimePix + SiProt results

18. setup Next-1,2

19. Fully sensitive detector A “long” cosmic track Timepix + 20 μm thick Siprot + Ingrid drifttime Stable operation in He iC4H10

20. Final assessment: spark-proofness Provoke discharges by introducing small amount of Thorium in the Ar gas – Thorium decays to Radon 222 which emits 2 alphas of 6.3 & 6.8 MeV – Depose on average 2.5.10 5 & 2.7.10 5 e- in Ar/iC 4 H 10 80/20 at -420 V on the grid, likely to trigger discharges Since 1 week, some 5.10 4 alpha events recorded in 1% of which … Charge mode

21. … discharges are observed ! For the 1 st time: image of discharges are being recorded Round-shaped pattern of some 100 overflow pixels Perturbations in the concerned column pixels – Threshold? – Power? Chip keeps working

22. Discharge signals on grid directly measured on scope

23. proportional signals from alfas discharges

24. Q max ~ 1 – 2 fC Chip may die if Q max > 10 fQ

25. set up ageing test

29. Ageing: - due low low gas gain ‘classical’ ageing (eq. ~ 1 C/cm2) not problematic - Panalytical measurement: confirms ‘risk’ - Two measurements show no classical ageing - HV trips indicate problem: cause not known at this moment Continue ageing tests Study of ageing processes by means of non-ageing set-up

30. Upgraded SCT: Gossip/GridPix could replace: - Pixel vertex detector: Gossip - Si Strip detectors: replace by Gossip Strixel detectors - TRT: use GridPix as tracker/TR X-ray detector Essentials: - power dissipation: 60 mW/cm 2 - intrinsic mass: 0.06 % radiation length [ 50 μm Si] - low cost: 10 $ / cm 2

31. - Ladder strings fixed to end cones - Integration of beam pipe, end cones & pixel vertex detector - 5 double layers seems feasible Virtual goal: ATLAS pixel vertex

32. Stainless steel tube: - string - power - CO 2 cooling Gossip chip + InGrid drift gap cathode foil ladder cross section data lines (Cu/kapton) casted aluminium ladder side view ladder top view

33. Upgraded SCT: Gossip/GridPix could replace: - Pixel vertex detector: Gossip - Si Strip detectors: replace by Gossip Strixel detectors - TRT: use GridPix as tracker/TR X-ray detector Essentials: - power dissipation: 60 mW/cm 2 - intrinsic mass: 0.06 % radiation length [ 50 μm Si] - low cost: 10 $ / cm 2

34. Upgraded SCT: Gossip/GridPix could replace: - Pixel vertex detector: Gossip - Si Strip detectors: replace by Gossip Strixel detectors - TRT: use GridPix as tracker/TR X-ray detector strixels/strips preamp channels Essentials: - power dissipation: 1/16 x 60 mW/cm 2 = 4 mW/cm 2 !Gas cooling feasible! - intrinsic mass: 0.06 % radiation length [ 50 μm Si] - low cost: 10 $ / cm 2 ~ 20 mm

35. Upgraded SCT: Gossip/GridPix could replace: - Pixel vertex detector: Gossip - Si Strip detectors: replace by Gossip Strixel detectors - TRT: use GridPix as tracker/TR X-ray detector Essential: - high position-resolution tracker throughout SCT - low mass, low cost detector - Efficient TRD possible with 17 mm Xe layers

36. A few comments about taken data. L=30 mm 0.05 mm  Vo=480, 520 V V1=2800 V, E drift = 760 V/cm According figures shown on the next pictures We should see: Total drift time ~ 2.1  s Maximum diffusion 6  *√3=6*150  m*1.7= 1600  m V0V0 V1V1 Set up and operating parameters

37. More samples pions (left) and electrons (right) Particle Identification

38. 5 – 10 layer Gossip Pixel 5 layer Gossip Strixel 4 layers GridPix TRT

39. Conclusions and plans GridPix has shown to work with Medipix-2, TimePix and PSI-46 Gossip has been demonstrated to work with the PSI-46 CMS Pixel FE chip Next steps: – Build from PSI-46 + SiProt + InGrid Demo ‘beam telescope’ ATLAS Muon Calibrator Demo B-layer: to be installed in hot spot in ATLAS near beam pipe – More tests to quantify the detector performances Beam tests for spatial and time resolution measurements GridPix as Transition Radiation Tracker Tests in magnetic field for measurements of dE/dx and gas diffusion – Gas ageing studies: testing Si containing compounds (SiO 2, SiH 4, SiC n H m ) Absence of ageing measured up to 5 x 10**16 MIPs/cm2 Extreme large rates and gas gains up to 500 k are possible, maintaining the proportional mode – In framework of CERN R&D project RD51: Simulations Development of general purpose GridPix chip TimePix-2

40. NIKHEF Harry van der Graaf, Max Chefdeville, Fred Hartjes, Jan Timmermans, Jan Visschers, Marten Bosma, Martin Fransen, Yevgen Bilevych, Wim Gotink, Joop Rovekamp University of Twente Cora Salm, Joost Melai, Jurriaan Schmitz, Sander Smits, Victor Blanco Carballo University of Nijmegen Michael Rogers, Thei Wijnen, Adriaan Konig, Jan Dijkema, Nicolo de Groot CEA/DAPNIA Saclay D. Attié, P. Colas, I. Giomataris CERN M. Campbell, X. Llopart University of Neuchatel/MTI Nicolas Wyrsch