Difference between revisions of "Commissioning Run Plan"

Revision as of 11:49, 14 October 2014

For the Fall of 2014 assume:

• Maximum beam current = 20 μA but for short times it can go higher for boiling studies and BCM calibration.
• 7.3 GeV @ 4 pass, 5.5GeV @ 3 Pass and 3.7 GeV @ 2 pass. No five pass beam in the Fall of 2014.
• Angle restrictions with DVCS calorimeter in place:
  1. HRS-BL: 26.5 to 45 degrees
  2. HRS-BR: 46.2 to 74.5 degrees

Pre-beam Checklist

Trigger Checkout (Experts)

* Checkout trigger timing
* Checkout of EDTM (Barak Schmookler)
* Think about adding 60, 100, 150, and 200 ns wide electronic deadtime scalers.
  This has been found to be a robust method for determining electronic deadtime in Hall C and we should think about adding something similar for GMP.

HRS Detector Checkout (Detector Experts)

* Take a long cosmics run with all detectors on.
* Look for dead and hot wires in the wire chambers against an earlier plot to look for any possible inconsistencies in wiring.  Check these against 
  those listed in the current analysis parameters. (Yang Wang)
* Look at ADC distributions for the hodoscopes Gas Cherenkovs and lead glass calorimeters.  Are they all firing? (Barak Schmookler, Longwu Ou)
* Look at TDC distributions for hodoscopes and Gas Cherenkovs.  Is the timing reasonable, any multiple peaks, within timing range, etc? 
  (Barak Schmookler, Longwu Ou)

Commissioning and Calibrations

The following items should be performed during the first 1-1.5 shifts with beam on target:

* Initial trigger checkout with beam.  Check timing and PID thresholds.
* Initial detector checkout with beam.
* Initial checks of beam position and raster.

The detector checkout is best done using a fairly uniform illumination, which is provided for by 20 μA on the central Carbon target at the following kinematics:

E' = 3.056 GeV, θ = 19 degrees (W² = 2.53 GeV, Q² = 2.43 GeV²). The HRS electron rates should be about 270 Hz.

Beamline

Superharp Scan with Raster off/on

1. Scan the two superharps near the target with raster off. Obtain two pictures including the three wires for each harp.
2. Make sure the three wires are clearly visible and have reasonable resolution: ~ 100-200 μm.
3. Repeat with raster on. In this case, you may not see the wires clearly.
4. Make sure to post the results in the Hall A elog.

BPM Calibrations (Bullseye Scan)

How to perform a bulls eye scan:

1. You need unrastered beam:

    - caution you should not do this with a target requiring rastered beam
    - use carbon, BeO, optics, or in the worst case empty instead

2. Ask MCC to steer the beam to the nominal center of the target.

3. Wait until beam is stable and have MCC perform a harp scan for the two superharps near the target (1H03A and 1H03B) and take a coda run during the

   same time. Start the coda run first before asking MCC.  Request MCC to make an ELOG entry with the results, you should see all three harp wires. 
   Record ELOG entry numbers. 

4. Ask MCC then to steer the beam to positions around the nominal center:

    - cover at least the area the raster will cover: (2,2), (2,-2), (-2,-2), (-2,2) and repeat (0,0)
    - repeat harp and coda runs for each position

5. Record Harp scan run numbers and corresponding CODA run number for each beam position.

6. Make a record of the harp scans and CODA runs in the HAlog.

How to analyze the bulls eye scan:

 - detailed instructions can be found at the Analyzing BPMs website.
 - the shift crew is not expected to analysis the bulls eye scan.

BCM Calibrations [2 hours]

1. Warn MCC a few hours beforehand.
2. The Hall A BCM and scalers need to be cross-calibrated to the Faraday cup and a BCM in the accelerator (OLO2) and the Hall A Unser.
3. Before beginning the procedure, make sure the Hall A BCM logger is started, which will record the signals from all relevant BCM used during the calibration.
4. Also start a HRS run to record the scalers during the calibration procedure.
5. It is useful to have someone over in MCC to help coordinate the calibration with them.
6. Take data on carbon target with I = 10, 20, 30, 40 50, 60, 70, 80, 90, 100 μA (or as high a current as available).

ARC Energy Measurement [? hours]

1. The procedure will be conducted by Doug Higinbotham in coordination with MCC.
2. Notify Doug and MCC a few hours beforehand to make sure they are ready and available.

Spectrometer Optics

• Time estimate: 1-2 hours

Procedure with Sieve-slit

* A Hall A Tech may be required to install the 2-inch lead sieve-slit collimator onto the front face of the HRS.
* Take a sieve slit run with the multi-foil carbon target for the inelastic kinematics in the table.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Repeat the above with the beam position shifted so that you see a vertical shift by one row.
* Rates assume 5 carbon foils, only 9 out of 25 sieve holes have events (~ 0.146 mSr acceptance), and 9% delta acceptance.

Alternative rates with 1-inch tungsten sieve slit: 
* Assumes that 49 out of the 63 holes are seen (~ 0.52 mSr acceptance); however, the acceptance is reduced by 85%, 
  since not all foils will see all holes.
* Rates assume 5 carbon foils and 9% delta acceptance.

Procedure without Sieve-slit

* Next take a run at the following kinematics without the sieve-slit collimator.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Rates assume 5 carbon foils, 6 mSr acceptance, and 9% delta acceptance.

Elastic from Hydrogen

Elastic electron-proton measurement. Assuming a 15 cm LH2 target, a spectrometer acceptance of 6 msr and elastic from Eric's rate program to compute the cross-section. Taking data at 7.3 GeV with the given momentum restrictions is time consuming.
(Table borrowed from DVCS3 wiki page)