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Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ and Analysis Bob Michaels with Reminder about Nov 2006 Results Specification of new.

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Presentation on theme: "Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ and Analysis Bob Michaels with Reminder about Nov 2006 Results Specification of new."— Presentation transcript:

1 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ and Analysis Bob Michaels with Reminder about Nov 2006 Results Specification of new FADC Data Analysis with FADC Gregg Franklin Alexandre Camsonne Sirish Nanda

2 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ FADC fanout to counting DAQ detector PMT (Neg. HV) amplifier ~ 20 m ~ 120 m ~ 30 m 1 st floor cnt room 2 nd floor cnt room Compton photons Nov 2006 Compton Integration DAQ FADC Data integrated over helicity pulse (30 msec) FADC samples also available. BCM, Compton laser status, & EPICS data available. Inside Hall A

3 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Time (ea. bin 5 nsec) Voltage (full scale ~2 V) FADC Samples that look like signal

4 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Time (ea. bin 5 nsec) Voltage (full scale ~2 V) FADC Samples that look like background ~ 50 nsec

5 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Integral over the width of individual pulses Its what the counting DAQ does, too. Clear Compton events seen. LED calibrates energy scale. Brehmstrahlung background (1/E)

6 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ To obtain a digital integral with zero deadtime: use so-called Accumulator = sum of samples subject to cut conditions : Cut conditions are optional Sample above a certain threshold. Sample below another threshold. over 30 msec helicity window ( can be turned off ) ( eliminates noise ) ( eliminates background ) Full-sampling mode used to evaluate systematic errors.

7 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Setting up Accumulator (Nov 06 data) Problems: 1.The high cut didnt work so we made big pulses clip at zero. 2.We did not know the pedestal of accumulator (understood later). FADC sample (ADC units)

8 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Asymmtries from Accumulator Day 1 : IHWP outDay 2 : IHWP in and different thresholds ! FLIP laser pol. Laser off.

9 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Summary of Nov `06 Experience Saw Compton events, good signal-to-background Too much electronic noise Accumulators worked well, but... Need shorter cable runs. Want no amplifiers Get more gain with 12-stage PMT ? Asymmetries made no sense until we realized … Pedestal subtraction wrong and threshold dependent. Need more info. to subtract pedestals.

10 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Specification of new FADC with fancier accumulators by Bob Michaels and Gregg Franklin Spec has been sent to two vendors: SISGmbH and CAEN. Expect boards from each vendor in ~August. Old SISGmbH boards can be updated (new firmware) Boards have other uses in Hall A.

11 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Resolution 12 bits Sampling Rate 250 MHz ( or 200) Range Buffer Accumulator Custom FADC based on SIS3320 / CAEN1720. bipolar Samples See next slides ( 33 msec ) CAEN SIS

12 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Voltage Time Zero Volts Typical Big Pulse (background) Typical Small Pulse (Compton event) Low Threshold High Threshold How Thresholds Work

13 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Accumulator Feature Samples added between Tstart and Tstop Subject to cut conditions (optional). Number of samples available N Ex #1 Data above a threshold, or data between a low & high threshold. Ex #2 Data N pulses before & after a threshold (more linear response). sample See the spec for details. Necessary for pedestal subtraction

14 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Voltage ; Conversion ; Pedestal ; ADC value Example : How to Analyze Data FADC measurements Integrated Signal ( C cancels in Asy. ) Deadtime Correction ( high threshold ``robs signal ) Physical Signal to use in Asymmetry. B = background empirical correction missing in Nov 06 thanks, Gregg !

15 Bob MichaelsParity Collab. Mtg. May 17, `07 Integrating Compton DAQ Conclusions – Integrating Compton DAQ ``Data Analysis on a Chip looks promising, may have widespread applications FADC with new accumulators ready this summer. ~ August but yet to be proven.


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