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Description of (as far as we understood) the VFAT calibration procedure

Description of (as far as we understood) the VFAT calibration procedure Software/firmware activities people. Set first approx threshold random triggers / no cal pulse -Set default DVt Reduce DVt until noise limit Set DVt to noise limit + n.sigma Use it to guess delay

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Description of (as far as we understood) the VFAT calibration procedure

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  1. Description of (as far as we understood) the VFAT calibration procedure • Software/firmware activities • people

  2. Set first approx threshold • random triggers / no cal pulse • -Set default DVt • Reduce DVt until noise limit • Set DVt to noise limit + n.sigma • Use it to guess delay • Scan for delay (approximate) by setting the threshold and using a large amplitude CalPulse • Further adjust delay • scan latency with cal pulse • look latency value +/- 1 --> adjust CalPhase to have all hits in the same time slot

  3. Do the real threshold scan • Do the precise (high statistics) S-curve • optionally scan dac respose via DCU to know number of e- corresponding to chosen DVt (via I2C). One VFAT at a time (they are in a chain). Or do a look-up table at the beginning and store it. • extract Qth and noise.

  4. Then trim the DACs to equalize the thresholds • do the high-statistics S-curve on every channel (analysis of the channels one by one) • Do with TrimDACs=00000 and =11111 (min and max) • Adjust DACrange • cycle until Qth distributions overlap • in a channel-by-channel base, set Qth to be in the middle of the value found for 00000 and 11111 (middle of the 2 histograms) (assume it is linear)

  5. Final timing • re-do the timing with the CalPulse with more accuracy. • time the external trigger • Then: ready to run. • How long will it take to do all this with the complete TOTEM? • Nobody knows now, will learn it the hard way. • Too early now (and too busy on other matters) to start worrying

  6. Paul • Reference knowledge, Q&A parties • Juha, Rauno • FEC software + extension (hard+soft) to send calibration / random triggers • Jan, Hubert • Sync monitoring to FEC config files, develop algorithms to extract threshold/noise • Giovanni, Gianfranco under Gueorgui’s supervision • VFAT emulator as bridge, fix Opto-rx firmware

  7. We are now dealing with the first step: first rough evaluation of threshold • Need • FEC software in a loop • Monitoring able to read FEC configuration + extract threshold + noise values • Triggering the system from the PC • Working VFAT hybrid + VFAT emulator bridge • Working Opto-rx • 3 activities in parallel • … it’s a long, long way …

  8. Set D_Vt • First step: do initial S-curve with random triggers • Choose number M of threshold (D_Vt) values to scan • Defines plot granularity • Choose number N of T1 triggers • Defines statistics • Hardware • I2C to program D_Vt • I/O register (or equivalent) send triggers • Opto-RX to receive data • Software • FEC in a loop + write config file • Monitoring must read config file Write config file Send T1 n.T1 = N? n.D_Vt = M?

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