Transcript Slides - Indico

Results from harsh X-Ray irradiation
Stefan Rummel
MPI for Physics – Halbleiterlabor
International Workshop on DEPFET Detectors and Application
Heidelberg 12.09.09
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Outlook
● Overview of the previous Irradiations
● Measurement program / Setup
● Results
● Outlook
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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What happened up to now… (Talk 2007 Aachen)
●Single pixel structures with 6 micron gate length
●Using the single-pixel setup, with current based readout
●Characterization with respect to:
•Electric characteristics
•Leakage current
•Spectroscopic performance
Cl
D1
G1
S
G
2D2
Cl
PXD4-10 MO2
PXD4-5 M05
PXD4-2 J14
Type
Protons @ 30MeV
Neutrons @ 1-20MeV
Gammas - Co60
Dose
1.2 * 1012 n/cm²
1.6 * 1011 n/cm²
913kRad
3*1012
2.4*1011
1MeV n equivalent
DEPFET collaboration meeting, Aachen 12-13.02.2007
Stefan Rummel; MPI for Physics
Electrical characteristics
RD07 conference, June 27-29, 2007 - Florence
Stefan Rummel; MPI for Physics
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Setup / Measurement program
● DEPFET MATRIX fully biased while irradiation with clocked clear
● Irradiation stepwise with evaluation of
 Characteristics
•
•
•
Sub threshold slope
Threshold voltage
Gm
 Threshold voltage of the parasitic CCG transistor
 Clear-Clear isolation
● Statistics of four transistors
● Irradiation facility: X-Ray generator with Umax=80kV, 180kRad/h
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Setup
International DEPFET Workshop
Stefan Rummel; MPI für Physik
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Results – Threshold voltage shift
● At 8 MRad 14V threshold voltage shift – compatible with measurements with
Co60
● Annealing at RT around 2.5V
● Dispersion in Vthr increases with dose - > Student in Karlsruhe will evaluate
96 transistors
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Spectroscopic performance
Unbestrahlt:
τ=10µs T=RT
ENCnoi = 2.1e-
7.8MRad X-Ray
τ=10µs T=RT
ENCnoi = 4.6e-
• Leakage current in the pixel ~40 fA ( 10-22fA unirradiated)
•DEPFET works very well after 8MRad!
International DEPFET Workshop
Stefan Rummel; MPI für Physik
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Proton irradiation
● Irradiation of 128² Matrix at the cyclotron in Karlsruhe
 p irradiation up to 10^11 p/cm² 10MeV
 Matrix fully biased
•
Utilizing the poly-bias resistors in PXD5
● Matrix is still in the fridge – waiting for the S3B system for final measurements...
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Conclusion
● DEPFET matrix is working very well after 8MRad
No significant detoriation of gq
No Problems with Clear-Clear isolation
Leakage current ~40 fA
●Good spectroscopic resolution
●Parameter spread due to irradiation will be investigated further
●Noise Spectrum will be evaluated with improved Setup in Milano (10MHz)
soon
●Following questions need to be answered:


Inhomogenity of radiation?
Impact of inhomogenous irradiation to the efficiency S/N?
Thanks to Karlsruhe for providing the irradiation facility and the dosimetry!
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Backup
International DEPFET Workshop
Stefan Rummel; MPI for Physics
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Backup – Evaluation of THR shift
International meetion DEPFET app. In HEP
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Inhomogenities
International meetion DEPFET app. In HEP
Stefan Rummel; MPI for Physics
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Inhomogenities
● Assuming a spatial inhomogenity Δ, so the dose varies between
dose – dose*(1+Δ)
● Calculating Dispersion= Uthr(dose*(1+Δ))- Uthr(dose)
International meetion DEPFET app. In HEP
Stefan Rummel; MPI for Physics
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