July 13, 2015 Cal F250

Video Conferencing Information

Meeting Time:

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Participant Direct Lines

• JLab Phone: in CC F326 is 757-269-6460 (usual room)
• JLab Phone in CC L207 is 757-269-7084
• Phone in the Regina Video-conference Suite is 306-585-4204

Action Items

List of issues:

• Handling of pedestal subtraction for late pulses (leading to negative values)

FA125's Useful Links

• FADC250 modes 2 from Ed and Hai, Feb 18 2014
• FIRMWARE for FADC250 Ver2 ADC FPGA, Sept 2014?
• Format doc version 5.06, 23 June 2015
• Timing algorithm wiki page - updated to include latest revisions
• Data format for 250 modes on fADC125 from Cody, Aug 15 2014
• FDC_pulse_data_format
• CDC readout needs Garfield calcs

References

• Media:FADC125 DataFormat v5 06.pdf
• GlueX-doc-2752 fADC250 Operational Characterization: Air Flow, Temperature and Pedestals

Tentative Agenda

1. Announcements
2. Action Items
3. Log Entry 3345390 and Log Entry 3345534 Floating and integer sums (Elton)
4. Log Entry 3345636 Correlation coefficient between samples (Elton)
5. Log Entry 3345807 Study of integration limits for BCAL Signals (Mark)
6. f250 data (David)
7. Any other business

Minutes

Attendees: Elton, David, Mark, Matt

1. Announcements
2. Action Items
3. f250 data (David)
   • Looked at R2931, mode 7 data, relatively high current, closest to expected running conditions
   • BCAL produces about 0.4 kB/event, FCAL about 0.5 kB/event, FDC about 0.6 kB/event. However most of the data is in form of headers, not content.
   • Presently the BCAL content represents less than 20% of the BCAL data volume and about 1.5% of the overall file size..... (Why is the overhead so high?)
   • Overall file size spring 2015 was about 25 kB/event. Resources has been computed assuming 18 kB/event.
   • -> Based on these overall considerations it may be possible to output 3 F250 words per hit channel and not affect file sizes significantly.
   • -> Consider options for 3 F250 words per hit channel, with one word with pedestal and/or other info that could be optionally dropped if required for data volume or transfer considerations.
   • Also provided graphical displays of various options considered for the F125 data as examples, as the graphs did not represent the latest documentation.
4. Log Entry 3345807 Study of integration limits for BCAL Signals (Mark)
   • Used LED data to study the fractional width as a function of the summing window. Pulses were all relatively large (~ 1000 counts)
   • Finds that the fractional width decreases with increasing pulse height.
   • There is a clear minimum fractional width obtained by sliding the position and width of the integration window.
   • The optimal window begins about 2 counts past the threshold and ends about 13 counts past the threshold (i.e. Nsb~-2, Nsa~13). The peak is at about 4 counts past the threshold.
   • The study was conducted with and without pedestal subtraction, with no significant difference.
5. Log Entry 3345390 and Log Entry 3345534 Floating and integer sums (Elton)
   • Monte Carlo study of the mean and width determined with floating and integer arithmetic. Three options were considered: a) data and averages all in floating point (reference, not physical) b) data truncated, but averages in floating point (e.g. indicative of keeping sums in firmware, but dividing with floating point precision later) and c) data truncated, and integer arithmetic used for averages (averages taken in firmware by bit shifting).
   • The integer arithmetic increases both the width of the distributions as well as impacts the extracted mean depending strongly on the number of samples used and the precise level of the pedestal.
6. Log Entry 3345636 Correlation coefficient between samples (Elton)
   • Correlation coefficients were computed for R3281 between all samples within the fadc sampling window. The average correlation is of order 5%, representing correlations during the 1 s sampling period of the data. Patters are quite interesting, but it is unclear how important these correlations are in pedestal determinations.
7. Any other business
   • Next meeting will be Tuesday July 28 at 1:30 pm, hoping for a regular schedule.