Proton Calorimetry/Meetings/2020/11/18

Minutes for UCL Proton Calorimetry Meetings, 18th November

Present

Ruben Saakyan, Raffaella Radogna, Saad Shaikh, Fern Pannell

Saad Shaikh

• Took and analysed photodiode data at home and at UCL with Raffy.
  • Results discussed with Ruben in this presentation.
• Main conclusions of analysis:
  • Found that the ADC is noisier than it should be by comparison of standard deviation of test mode histogram with that of where photodiodes are unplugged. Any noise introduced by photodiodes is masked.
  • Measurements taken in D27 are likely subject to significant electronic noise – giving strange histograms when the two channels of a photodiode are combined.
    • Ruben suggested to check for bugs in the code, but none have been found yet. Additionally, combined histograms of dark measurements taken at home away from electronic noise make sense. Raffy will continue to work on and debug the plotting macro.
    • Will repeat (dark) measurements with detector but in an office to see if noise persists.
  • Ruben was very dubious about the way charge is split into two channels on the DDC232 board – better ways to do this (transistors?).
    • Behaviour of underflow measurements (where exactly 0 is returned by the DDC232) suggests there is something going wrong: at home, 0 measurements in one channel are paired with 'real' values from the other channel, such that underflow disappears in the combined photodiode histogram.
    • Underflow persists in measurements taken in D27, perhaps due to electronic noise.
• While ADC is very noisy, might still be worthwhile to do some characterisation with intense LED injected directly into photodiodes.
• Will take UV torch home during next visit to UCL, to conduct some light measurements at home, away from electronic noise.
• Will contact Marko to investigate charge splitting and electronic noise problems.
• Should also contact Texas Instruments to discuss apparent worsening of performance with increasing integration time and decreasing full-scale range. Unclear whether this observed behaviour is something introduced in the board design.
• Will continue work on Nexys Video USB interface.