TCT measurements with irradiated strip detectors Igor Mandić 1, Vladimir Cindro 1, Andrej Gorišek 1, Gregor Kramberger 1, Marko Milovanović 1, Marko Mikuž 1,2, Marko Zavrtanik 1 1 Jožef Stefan Institute, Ljubljana, Slovenia 2 Faculty of Mathematics and Physics, University of Ljubljana, Slovenia Most measurements made by diploma student Mitja Krnel 1

TCT with focused IR laser light focused IR laser light directed on the surface of strip detectors: Top-TCT “Spaghetti” detectors produced by Micron: p-type, FZ, 300 µm thick, 4x4 mm 2 - strip pitch: 80 µm - implant width: 20 µm, DC coupled - spaghetti: all strips connected on one side  E field as in strip detector, weighting field as in pad detector T1 type  500 µm of implant not covered by metal detectors irradiated to 1∙10 15, 2∙10 15 and 5∙10 15 n/cm 2 measurments after several annealing steps at 60°C up to total annealing of 5120 minutes at 60 C!! Motivation: check the uniformity of response  laser measurement possible also under implants Introduction: 2

Setup Detector box Cooled support y table Laser Laser driver detector HV Peltier controller z tablex table 1GHz oscilloscope cooling pipes fast current amplifier trigger line optical fiber & focusing system width of light pulses ~ 100 ps, repetition rate 200 Hz beam diameter in the silicon FWHM~7  m Bias-T 3

4 All strips connected together  E field as in strip detector  weighting field as pad detector  signal is a summ of currents induced on all strips Last 500 µm of implants not covered with metal Detector

Signals Before irradiation Bias = 100 V scan laser spot across the the surface 5 Signals induced by laser beam at different locations: No metal metal Guard ring

6 Before irradiation Bias = 100 V (depleted) Metal End of implants Guardring Charge = integral of current pulse (offline)

7 Some signal also when beam on metal  tails of light spot guard ring metal no metal Reflection from metal Before irradiation Bias = 100 V

8 Irradiated detector Φ eq = 5·10 15 n/cm 2 Bias = 1000 V Annealed 5120 minutes at 60 C multiplication expected End of implants Large signals close to guard ring

9 Irradiated detector Φ eq = 5·10 15 n/cm 2 ; Bias = 1000 V; Annealed 5120 minutes at 60 C  high signals also near the guard-ring parallel to the strip stripsGuard ring

10 Δt = 0.2 ns Δt = 0.6 ns Δt = 0.7 ns Step: 50 µm (dot colors correspond to line colors) Irradiated detector Φ eq = 5·10 15 n/cm 2 Bias = 1000 V Annealed 5120 minutes at 60 C guard ring metal no metal The second peak probably from high field at the end of implant

11 guard ring metal no metal Scan over “no metal” Pulses from scan over “no metal” part Pulses from scan over “metal” Scan over “metal” Irradiated detector Φ eq = 5·10 15 n/cm 2,Bias = 1000 V, annealed 5120 minutes at 60 C Complicated behavior near guard rings!

12 Signals on edges increase with long term annealing  multiplication effects Irradiated detector Φ eq = 5·10 15 n/cm 2, Bias = 1000 V 80 min at 60°C320 min at 60°C 1280 min at 60°C5120 min at 60°C

13 Irradiated detector: effect of annealing Φ eq = 5·10 15 n/cm 2 ; Bias = 1000 V; Scan over metalized part of strips ~ 1 mm from guard ring Scan over non metalized implants ~ 0.5 mm from guard ring implant  more non-uniform with annealing  multiplication at the edge of implants  effect increases closer to guard-ring

14 Φ eq = 5·10 15 n/cm 2 ; Bias = 600 V; Scan over metalized part of strips ~ 1 mm from guard ring Scan over non metalized implants without ~ 500 µm from guard ring  uniformity doesn’t change much with annealing  charge drops with reverse annealing  no multiplication Irradiated detector: annealing 600 V

15 Annealing of CCE depends on location Increase of charge with long annealing at the implant edge Annealing Φ eq = 5·10 15 n/cm 2 Bias = 1000 V

16 Annealing Φ eq = 2·10 15 n/cm 2 Bias = 1000 V larger non-uniformity after long annealing annealing of CCE depends on location increase of charge with long annealing larger closer to implant edge

17 Annealing Φ eq = 2·10 15 n/cm 2 Bias = 1000 V slightly different behavior at larger distance from guard-ring metal

18 2e15, anneaeld 5120 min5e15, anneaeld 5120 min Voltage scan

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20 Spaghetti detectors  all strips connected  sum of signals from all strips measured  opposite polarity contribution from neighbor strips are added  oscillations of CCE with location may be dumped Hamamatsu detector irradiated to 1e15: ( plot from Bari : ) Sum of signals from near neighbor strips 1000 V

21 Summary