MainPage:Nuclear:DVCS-3

⇐ Back to the Main_Page

DVCS-3 Updates

Deadtime analysis in progress: main goals include

Determine the livetime/deadtime correction factor (LTCF)
Take a trigger rate/live rate and normalize using the current, adjust to the prescale, and then apply the LTCF.
To make sure the deadtime is correctly computed, the deadtime, current and prescale factors should be in agreement more than 1%, especially for the range of rates in which the deadtime is linear.

Currently analyzing run taken in April 2016, 13418 which was a dedicated run for the deadtime analysis, at three different currents (10, 15, 20 uA) using a liquid hydrogen target.
There are other dedicated deadtime runs taken in February 2016 with a carbon target, 12471 to 12476 at a current of ~5 uA with different prescale factors ( ).

Deadtime Analysis

Brief Overview

DVCS-3 was an experiment that ran from 2015-2016 in Hall A (E12-06-114) is one of the first experiments of the 12 GeV era. The method of DVCS is the cleanest way to access Generalized Parton Distributions (GPDs). The deadtime is defined as the ratio of the number of "live" events going into the electronics or computers to the total number of events. The deadtime calculations are crucial for the calibration process after the experiment. The electronic and computer deadtime need to be quantified to eventually extract precision measurements of the cross section, and thus obtain the neutral pion form factor.

Detectors in the HRS

There are three detectors that work within the HRS (High Resolution Spectrometer): the S0, S2, and the Cherenkov Detector.

Definitions

Scalars - each detector has two types of scalars, internal and external.
- External Scalars (borrowed from here)
1. 512ns clock from DVCS trigger crate (1)
2. DVCS cosmic trigger
3. s0
4. s2
5. CER
6. EDTM
7. DVCS external clock or LED trigger
8. ARS_stop
9. ARS_valid
10. DVCS calorimeter ADC_gate
11. inverted S0
12. inverted S2
13. inverted CER
14. L1A
15. CaloBlock001
16. External S2M_CER
17. 64ns clock from DVCS trigger crate
18. 512ns clock from DVCS trigger crate (2)
25. Master_OR
26. Master_OR_Live
27. HRS_Single
28. S2M_CER
29. S2M_CER_Scaled
30. 103kHz clock from spectrometer
31. BCM signal

Beam Current Monitor (BCM) - Beam Position Monitor (BPM) -

Plots from run 13418: dedicated deadtime analysis run


xx	xx
Histogram displaying S0, S2 and the Cherenkov Detector's livetime. We can see that since the Cerenkov detector has the shortest livetime, its deadtime dominates compared to the other detectors.	xx
xx	xx
xx	xx