NA62 Gigatracker Working Group Meeting 23 March 2010 Massimiliano Fiorini CERN

Measurement setup (1) M. Noy (19/11/2009) Discriminated pixel output

Measurement setup (2) single PC controlling everything via USB and Ethernet inject charge pulses with fixed rise time (2.5 ns) and variable amplitude Tektronics AFG3252 pulse generator driving charge injection circuit programmable 0 – 5 V, pulse min. 50 mV, steps of 1 mV 1/10 attenuation: 5 mV  0.5 V, steps of 100 µV charge injection ~20 fF (0.1 fC  10 fC) record injected signal and discriminated pixel output with oscilloscope LeCroy WavePro 7100A oscilloscope (20 GS/s for 2 channels, 1 GHz analogue bandwidth) CERN prototype chip: measurement of 1 of the 5 test pixels with discriminated output with CLOCK OFF with CLOCK ON (replaced USB card with ALTERA board) 250 MHz DLL operation (125 ps bin)

Measurement setup (3)

T in V (0.7 fC) threshold

Measurement setup (3) T1T1 T2T2 0 V threshold

Injected pulse signals nominal pulse amplitudes from 0.06 V to 0.5 V (correspond to 1.2 fC and 10.0 fC resp.) note: 1/10 attenuation threshold set to V (0.7 fC)

Discriminated output signals

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

Injection time measurement (2) least square method applied to: Method 1 3 samples above and below threshold Method 2 40 samples on the rising slopes at fixed position (~ ns) T in

Discr. times measurement least square method applied to: Method 1 3 samples above and below threshold (0 V) T1T1 T2T2

Correlation coefficient: T 1 and T 2

Correlation coefficient: T in

Ex. of low charge pulse shape (1)

Ex. of low charge pulse shape (2)

Method 1 Vs 2 for T in Measurement

T 1 jitter

Correction of Injection Baseline Variation

Injection baseline variation

T 1 jitter (w. baseline correction) variation of V (0.7 fC) threshold taking into account (trace by trace) baseline variation lower T 1 jitter

Results with CLOCK OFF

Leading edge time (T 1 )

Trailing edge time (T 2 )

Injection time (T in )

(T 1 – T in )

(T 2 – T in )

Time over Threshold (T 2 – T 1 )

T 1 jitter: (T 1 – T in ) rms

T 2 jitter: (T 2 – T in ) rms

Results with CLOCK ON

Leading edge time (T 1 )

Trailing edge time (T 2 )

Injection time (T in )

(T 1 – T in )

(T 2 – T in )

Time over Threshold (T 2 – T 1 )

T 1 jitter: (T 1 – T in ) rms

T 2 jitter: (T 2 – T in ) rms

Extraction of CLOCK contribution

T 1 jitter: CLOCK contribution mean jitter value of (36 ± 2) ps above 2 fC

Geant 4 Simulation

Energy 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 T 1 jitter value taking into account the energy distribution of particle hits in the Gigatracker, one can extract a weighted average value for the jitter on T 1 no charge sharing between pixels considered

Charge weighted average result: (65 ± 12) ps  CLOCK OFF Charge weighted average result: (76 ± 11) ps  CLOCK ON CAVEAT  measurements done with: 20 pF pixel input capacitance (no bump-bonded sensor) 2.5 ns pulse injection rise time 25 °C ambient temperature no charge sharing Comparison with simulation: simulations from J. Kaplon show ps rms (160 ps pk- pk) for a 3.0 fC signal Results of weighted jitter

Conclusions T 1 jitter was measured to be: lower than 100 ps for charge injection greater than 2.0 fC ~69 ps at 3.2 fC injection (mean charge released by mip) Charge weighted jitter is (76 ± 11) ps with CLOCK ON Measurement + analysis method limited by noise especially for low charge injections (less than ~2 fC) measured jitter values have to be considered upper limits

SPARES

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)

Time Over Threshold Correction

ToT Correction (1) build Look-Up Table to correct T 1 as a function of the signal Time Over Threshold, i.e. (T 2 – T 1 )

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 (T 1 – T in ) plot fit, compute the time correction to be applied to T 1 then build complete LUT to be used in reconstruction program

Results (1) T 1 – T in distribution becomes flat error bar = jitter small shift around ~6 fC due to change in measurement conditions

Results (2) T1 jitter consistent with value before correction problem with the same 2 points around 6 fC

Results (3) problem with 2 points around ~6 fC due to events “leak” from one bin to the next one around the “threshold” for anomalous T in behavior

Results (3) problem with 2 points around ~6 fC due to events “leak” from one bin to the next one around the “threshold” for anomalous T in behavior

problem with 2 points around 6 fC due to events “leak” from one bin to the next one around the “threshold” for anomalous T in behavior Results (3)

Correction of Injected Pulse Height Variation

Inject. pulse height variation (1)

Inject. pulse height variation (2)

Inject. pulse height variation (3)

T 1 jitter selection of injected pulse height within ±0.1 mV of local mean value (±0.002 fC) comparable T 1 jitter (lower jitter for first bin only) cuts a lot of statistics and has negligible effect: not used in the analysis