Gigatracker read-out chip test results

Preliminary results on CERN GTK read-out chip prototype testsGigatracker Working Group Meeting8 December 2009Massimiliano FioriniCERN

Measurement setup (1)

M. Noy (19/11/2009)Discriminated pixeloutputMeasurement setup (2)measurements by M. Noy and E. Martinsingle PC controlling everything via USB and Ethernetinject charge through pulses with fixed rise time (2.5 ns) and variable amplitudeTektronics AFG3252 pulse generator driving charge injection circuitprogrammable 0 5 V, pulse min. 50 mV, steps of 1 mV1/10 attenuation: 5 mV 0.5 V, steps of 100 Vcharge injection ~20 fF (0.1 fC 10 fC)chip configuration done via USB cardrecord injected signal and discriminated pixel output with oscilloscopeLeCroy WavePro 7100A oscilloscope (20 GS/s for 2 channels, 1 GHz analogue bandwidth)

Measurement setup (3)

Measurement setup (3)Tin0.035 V(0.7 fC)threshold

Measurement setup (3)T1T20 VthresholdInjected pulse signalsnominal pulse amplitudes from 0.06 V to 0.5 V (correspond to 1.2 fC and 10.0 fC resp.)note: 1/10 attenuationthreshold set to 0.035 V (0.7 fC)

Discriminated output signals

Injection time measurement (1)least square method applied to:Method 1: 3 samples above and below thresholdMethod 2: 40 samples on the rising slopes at fixed position (11-13 ns)

Injection time measurement (2)least square method applied to:Method 1: 3 samples above and below thresholdMethod 2: 40 samples on the rising slopes at fixed position (11-13 ns)

TinDiscr. times measurementleast square method applied to:Method 1: 3 samples above and below threshold (0 V)

T1T2Method 2 for Tin MeasurementT1 distribution

T2 distribution

Tin distribution

(T1 Tin) mean value distribution

(T2 Tin) mean value distribution(T1 Tin) rms distribution

(T2 Tin) rms distribution

(T2 T1) mean value distribution

Method 2 Vs Method 1 for Tin MeasurementT1 jitter

T2 jitter

Correction of Injection Baseline VariationInjection baseline variation

T1 jitter

variation of 0.035 V (0.7 fC) threshold taking into account (trace by trace) baseline variationlower T1 jitterCorrection of Injection Pulse Height VariationInject. pulse height variation (1)

Inject. pulse height variation (2)

Inject. pulse height variation (3)

T1 jitter

selection of injected pulse height within 0.1 mV of local mean value (0.002 fC)comparable T1 jitter (lower jitter for first bin only)Time Over Threshold CorrectionToT Correction (1)

build Look-Up Table to correct T1 as a function of the signal Time Over Threshold, i.e. (T2 T1)ToT Correction (2)

from ToT plot fit, extract input charge values using 50 ps wide time intervals (from 10 ns to 20 ns)ToT Correction (3)

from (T1 Tin) plot fit, compute the time correction to be applied to T1then build complete LUT to be used in reconstruction programResults (1)

T1 Tin distribution becomes flaterror bar = jittersmall shift around ~6 fC due to change in measurement conditionsResults (2)

T1 jitter consistent with value before correctionproblem with the same 2 points around 6 fCResults (3)

problem with 2 points around ~6 fC due to events leak from one bin to the next one around the threshold for anomalous Tin behaviorResults (3)

problem with 2 points around ~6 fC due to events leak from one bin to the next one around the threshold for anomalous Tin behaviorproblem with 2 points around 6 fC due to events leak from one bin to the next one around the threshold for anomalous Tin behaviorResults (3)

Geant 4 SimulationEnergy release GTK per hit

mean energy: 72.4 keV (~20.1 k e-h ~3.2 fC)most probable energy: 53.7 keV (~14.9 k e-h ~2.4 fC)FWHM: ~25 keV (~6.9 k e-h ~1.1 fC)minimum energy: ~29 keV (~8.1 k e-h ~1.3 fC)

Charge-weighted T1 jitter valuetaking into account the energy distribution of particle hits in the Gigatracker, one can extract a weighted average value for the jitter on T1

Charge weighted average result: (70 5) psCAVEAT measurements done with:20 pF pixel input capacitance2.5 ns pulse injection rise time35 C ambient temperatureComparison with simulation:simulations from J. Kaplon show 30-40 ps rms (160 ps pk-pk) for a 3.0 fC signalmeasurements show ~70 ps rms for 3.0 fCTO DO list:identify other (possible) systematic effects in the measured quantities and correct for themanalyze data samples at different temperatures (-5, 5, 15, 25 C)

Final Results and TO DO ListConclusionsT1 jitter lower than ~140 ps for charge injection greater than 1.0 fC

Charge weighted jitter is ~70 ps

ToT correction technique works well: LUT has been produced for fast offline correction

Developed software tool for the analysis of measurement data which fits into the existing testing setupSPARES

Energy release GTK per hit (2)

mean energy: 72.4 keV (~20.1 k e-h ~3.2 fC)most probable energy: 53.7 keV (~14.9 k e-h ~2.4 fC)FWHM: ~25 keV (~6.9 k e-h ~1.1 fC)minimum energy: ~29 keV (~8.1 k e-h ~1.3 fC)