Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 1
Some recents resultsSome recents resultsat NIKHEFat NIKHEF
M. Chefdeville, E. Bilevych, H. van de Graaf, J. Timmermans
D. Attié, P. Colas
Medipix meeting, CERN – 13 September 2007
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 2
Overview
•Pixel readout of gaseous detectors using Micromegas-like structures
•Adding functionalities to pixel readout chips by wafer post-processing
–Gas gain grids: Ingrid–Discharge protection: Siprot
•Results with some Timepix chambers, 65k channel μTPC– 55Fe source–Cosmic rays data– 90Sr source in TOT and Time modes
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 3
Processing Ingrids
(MESA+, Univ. Twente)
• Substrate can be:– Si wafer with a patterned anode– Pixel readout chip
• Photo-resist coating & exposure– Define the amplification gap (tens of μm)– Define the supports (pillars/walls)
• Metal film deposition & patterning– Define the grid geometry
• Dissolve the un-exposed resist– + some cleaning
substrate
photo-resist
20 μm pitch
50 μm pitch
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 4
New Ingrid developments and results
• Process improvement: grids much flatter
– Extremely good energy resolution:13.6 % FWHM with 55Fe in P10
– Removal of Kβ 6.5 keV line:11.7 % @ 5.9 keV in P10
– With F=0.17 and Ne = 229 gain fluctuation ~ 0.5
• New wafer masks:hole pitches down to 20 μmwith various diameters and gaps
– Investigate Micromegas geometry– Test of the ion backflow theory
feasible
• Until now: 1 μm thin Albut can now be increased to 5 μm by electrolysisExpect less damaged from sparks
Kα escapeKβ escape
13.6 % FWHM
Kβ-filtered spectrum with Cr foil
11.7% FWHM
Max Chefdeville (NIKHEF/Saclay) + Twente Univ.
Gap: 50 μm; Hole picth: 32 μm,Ø: 14 μm
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 5
Status of Timepix usage at NIKHEF
• 1st Timepix (+ 3 μm Siprot):“under HV” Dec-Jan 2006 for 40 days He/isoButane 80/20 then died after ONE day with Ar/isoButane
• “Old” detector: (Timepix C08-W0014 + 3 μm Siprot): was “under HV” with He/isoButane 80/20 since 24 April (for 3 months!)
• Detector Next-1: (Timepix E09-W0014 + 20 μm Siprot + Ingrid): under HV for > one month with He/isoButane
• Detector Next-2: (Timepix + 20 μm Siprot + Ingrid):just started on Ar/isoButane
• Detector Next-3: (Medipix2.1 + 30 μm Siprot + Ingrid):gain 200k reached
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 6
NIKHEF setup (on 24 Aug. 2007)
Next-3
Next-1,2 “old”
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 7
Irradiation: 90Sr source
• Timepix chip + Micromegas mesh:
• Timepix chip + SiProt + Ingrid:
Moiré effects
“Uniform”MESA+
IMT Neuchatel
CERN
TOT mode
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 8
Cosmic rays
A “long” cosmic track
Timepix +
20 μm thick Siprot
+
Ingrid
time
He/Iso (80:20)
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 9
Irradiation: 90Sr source
TOT mode
Timepix+
20 μm Siprot+
Ingrid
in Next-1
5 ms/frameHe/Iso (80:20)
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 10
Irradiation: 90Sr source
Time mode
118 μs/frame
Timepix+
20 μm Siprot+
Ingrid
in Next-1
He/Iso (80:20)
Timepix at NIKHEF Medipix meeting, CERN – 13.09.2007 11
• Chip tiling: large(r) detector surfaces (2x2, 2x4 chips)• Through Si connectivity: avoiding bonding wires• Fast readout technology: ~5 Gb/s
RELAXD project (Dutch/Belgian)NIKHEF, Panalytical, IMEC, Canberra:
Hope for “through Si vias” (with Medipix chips) later this year!
Further Developments