International DEPFET Workshop Stefan Rummel; MPI for Physics 1 Results from harsh X-Ray irradiation Stefan Rummel MPI for Physics – Halbleiterlabor International Workshop on DEPFET Detectors and Application Heidelberg
International DEPFET Workshop Stefan Rummel; MPI for Physics 2 Outlook ● Overview of the previous Irradiations ●Measurement program / Setup ●Results ●Outlook
DEPFET collaboration meeting, Aachen Stefan Rummel; MPI for Physics 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 D1 D2 S G1 G2G2 Cl PXD4-10 MO2PXD4-5 M05PXD4-2 J MeVGammas - Co60 Dose1.2 * n/cm²1.6 * n/cm² 913kRad 1MeV n equivalent3* *10 11
RD07 conference, June 27-29, Florence Stefan Rummel; MPI for Physics 4 Electrical characteristics
International DEPFET Workshop Stefan Rummel; MPI for Physics 5 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
Setup International DEPFET Workshop Stefan Rummel; MPI für Physik 6
International DEPFET Workshop Stefan Rummel; MPI for Physics 7 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 für Physik 8 Spectroscopic performance Unbestrahlt: τ=10µs T=RT ENC noi = 2.1e - 7.8MRad X-Ray τ=10µs T=RT ENC noi = 4.6e - Leakage current in the pixel ~40 fA ( 10-22fA unirradiated) DEPFET works very well after 8MRad!
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 9
International DEPFET Workshop Stefan Rummel; MPI for Physics 10 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!
Backup International DEPFET Workshop Stefan Rummel; MPI for Physics 11
Backup – Evaluation of THR shift International meetion DEPFET app. In HEP Stefan Rummel; MPI for Physics 12
Inhomogenities International meetion DEPFET app. In HEP Stefan Rummel; MPI for Physics 13
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 14