Results from MPGDs with Protected Pixel Sensors as Active Anode MP33

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Results from MPGDs with Protected Pixel Sensors
asActive AnodeMP3-3

• Harry van der Graaf
• Nikhef, Amsterdam
• on behalf of the
• GridPix group
• IEEE-NSS Honolulu 2007

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Overview

• GridPix chambers
• InGrid the Integrated Grid
• SiProt the amorphous Si Protection layer
• Chamber results
• GridPix TimePix SiProt InGrid/Micromegas
• PSI-46 Pixel FE chip SiProt Micromegas
• TimePix SiProt Micromegas _at_ CEA/Saclay
• All-Gas detectors for trackers

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GridPix chamber principle
cathode
Micromegas or InGrid
Pixel chip
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Wafer post-processingInGrid
Hex / Pillars

• 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

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New Ingrid developments and results

• Process improvement grids much flatter
• Extremely good (record?) energy resolution
• 13.6 FWHM with 55Fe in P10
• Removal of Kß 6.5 keV line
• 11.7 _at_ 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

Ka escape
Kß escape
13.6 FWHM
Gap 50 µm Hole picth 32 µm,Ø 14 µm
Kß-filtered spectrum with Cr foil
11.7 FWHM
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Full post-processing of a TimePix

• Timepix chip Micromegas mesh

Moiré effects pillars
CERN

• Timepix chip SiProt Ingrid

Uniform
MESA
IMT Neuchatel
Charge mode
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A scratch occurred during the construction of
Ingrid Loose parts removed. Ingrid working!
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• 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

SiProt a low T deposited hydrogenated amorphous
silicon (aSiH) layer Up to 50 µm thick films,
1011 O.cm
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TimePix SiProt results
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setup
Next-1,2
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Status of Timepix application at Nikhef

• 13 dec. B05 with 3 µm SiProt Micromegas in He
  20 iC4H10
• 24 jan. Switch to Ar 20 iC4H10, chip died after
  2 days
• 20 mar. MediPix2 with 3 µm SiProt InGrid
  operated 4 days in He
• 17 apr. C08 with 3 µm SiProt Micromegas
• guard electrode (G.E.) in He
• 25 jul. Stop C08 after 3 months of continuous
  operation in He
• E09 with 20 µm SiProt InGrid placed
• in NEXT-1 chamber in He
• 22 aug. A06 with 20 µm SiProt Micromegas placed
• in NEXT-2 chamber in He
• 04 sep. Flush NEXT-2 (A06) with Ar, stable
  operation for 2 weeks
• 23 sep. Flush NEXT-1 (E09) with Ar, same nice
  results

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Fully sensitive detector
A long cosmic track
Timepix 20 µm thick Siprot Ingrid
Stable operation in He iC4H10
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Stable operation in Argon too!
Time mode
After 2 weeks of cosmic event recording, it was
time for a definitive assessment whether 20 µm
SiProt is enough to protect against discharges
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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 2.5.105 2.7.105 e- in
  Ar/iC4H10 80/20
• at -420 V on the grid, likely to trigger
  discharges

Charge mode
Since 1 week, some 5.104 alpha events recorded in
1 of which
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discharges are observed !

• For the 1st 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

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Discharge signals on grid directly measured on
scope
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proportional signals from alfas
discharges
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Qmax 1 2 fC Chip may die if Qmax gt 10 fQ
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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
replacement of (vertex) tracking detectors..
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GOSSIP Basics (PSI-46 Brico specific)
Use Pixel chip for readout, use gas layer for
detecting MIPs
50µm high support pillars
Gas 1.2 mm as detection medium 99 chance to
have at least 1 e- Gas amplification 25,000 in
90/10 Ar/CH4 Single electron sensitive All
signals arrive within 18 ns
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We can see tracks!
(Frame 17 is really great)
7.8mm
8mm
Animated GIF of 100 hits on the PSI46 brico, 30µm
SiProt. (if this does not animate, drop the
picture into a web browser)
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Since last week TimePix SiProt
Micromegas works in CEA/Saclay Paul Colas et
al.
55Fe events, enlarged
55Fe events
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Tracking of charged particles principle
Measurement of time and place of a charge signal
from detection material

• 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

• Consequences for future experiments
• ILC
• LHC Upgrade (Super LHC)
• All Gas detectors, followed by calorimeters

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Conclusions Plans

• InGrid is now a proven technology
• With a 20 µm SiProt layer, a chip in GridPix is
  spark proof
• GridPix has shown to work with Medipix-2, TimePix
  and PSI-46
• Next steps
• High-Resistive InGrid
• Build a larger area detector
• Chip tiling, wafer thinning through-via
  bounding, fast Gbit/s readout
• Build beam telescope and vertex detectors from
  PSI-46 chip
• 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 (SiO2, SiH4, SiCnHm)
• Absence of ageing measured up to 5 x 1015
  MIPs/cm2
• Extreme large rates and gas gains up to 500 k are
  possible, maintaining the proportional mode

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• 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