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FEE card validation

FEE card validation. M. Raggi , T. Spadaro. The problem. Validate FEE production threshold determination at < 1mV accuracy comparator time effects: Overdrive Signal slope After validation for prototype cards, final decision for: amplification hysteresis DAC internal pulser features.

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FEE card validation

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  1. FEE card validation M. Raggi, T. Spadaro

  2. The problem • Validate FEE production • threshold determination at < 1mV accuracy • comparator time effects: • Overdrive • Signal slope • After validation for prototype cards, final decision for: • amplification • hysteresis • DAC internal pulser features

  3. Threshold • Measure threshold by means of time correlation: • fit threshold imposing time response is independent of signal amplitude • For this to work, have to evaluate and subtract: • slewing effects • overdrive effects • slope effects

  4. Threshold measurement • Measure threshold by means of time correlation: • fit threshold imposing time response is independent of signal amplitude • For this to work, have to evaluate and subtract: • slewing effects • overdrive effects • slope effects

  5. Threshold measurement Need to assess threshold @sub-mV level, mandatory for Q vs T reliability Tried measuring efficiency as a function of minimum signal voltage: would need clean environment: in presence of a 2-3 mV radiofrequency noise, width of efficiency profile depends on noise Try to overcome this, by measuring crossing times: register both a signal copy and the LVDS output with a flash ADC evaluate LVDS transition time, TL (leading or trailing) assume a trial threshold Vth, evaluate signal transition time TS(Vth) For the correct Vthvalue, TL-TS(Vth) is independent of the signal amplitude Measurement for real signals, use PMT pulsed by 70-ps width LASER source

  6. Threshold measurement Trailing time correlations as a function of trial threshold values For the true value of the threshold, dT should be independent from Vmin Vmin dT (trailing) (ns)

  7. Threshold measurement Correlation factor for trailing times Vth(V)

  8. Threshold measurement Effect of overdrive-dependent delay at the comparator must be subtracted for dT to be independent on Vmax Reminder: for old (new) voltage at comparator is amplified x5 (x3) wrt original signal

  9. Threshold measurement Effect of slope-dependent delay at the comparator must be subtracted for dT to be independent on Vmax Reminder: for old (new) voltage at comparator is amplified x5 (x3) wrt original signal 1 V 2 V 3 V ~ 0.2 V V equivalent at comparator for 5 ns rise time

  10. First assessment of overdrive + slope effects Measure via CAMAC LED driver pulser FEE threhold was 20+-2 mV Can vary signal amplitude: range used, from 30 mV to 200 mV Presently, cannot vary rise time: fixed at ~ 2.7 ns (20%-80%) vs PMT value of ~ 5 ns. For 30 mV, this is equivalent to ~ 8 V/ms dT = P1 + P2/√Vmax Reminder: for old (new) voltage at comparator is amplified x5 (x3) wrt original signal 450 75 200 325 V overdrive at comparator

  11. Preliminary conclusions First assessment of overdrive + slope effects seem satisfactory for veto capabilities Have to confirm this picture with smaller slope, as for the PMT signal Will use again ultra-short LASER pulse + PMT to measure combined effect For the mass validation, 2 possible methods might be performed: Use of LASER + PMT, including step-by-step motor for LASER intensity automatic variation Use of a GPIB-programmable pulser, for which both amplitude and rise time can be changed

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