Commissioning Plan for Left HRS
Before we use the Left HRS to commission HCAL, we need to spend some time checking the HRS itself. Most checks of detector and the DAQ can be done with cosmics or with pulsers, but the two topics where we need beam are: 1) Check the HV on the Cherenkov detectors -- need electrons going in the right direction, and 2) Check the magnetic optics. We can start with an optics database from the Tritium era.
Initially we'll have the HRS at about 80 degrees. We can run with beam and check detectors and look at reconstructed angles at the target. We can do this parasitically or late at night when nobody is in the hall. (We need the beam on target.) For the reconstructed angles, all is well if the acceptance looks about right (a familiar rectangle) and if the comparison of TRANSPORT angles to Monte Carlo looks good. Later, when we remove Bigbite, we can move the HRS to smaller angles (~30 degrees) and put in the sieve slits and check more carefully the optics if time permits. If the optics are really bad (blurry hole pattern) we can do an optics calibration run plan. However, I doubt that we even need an Optics calibration.
Rate calculations for e-P elastic scattering into Left HRS. Assuming 15 cm LH2 target. 1 uA of beam. Here I used some of the kinematics given in the HCAL run plan. 4.4 GeV is not very practical. Note, the sieve slit will cut the rate by a factor of 200. E' is the momentum setting of the L-HRS for elastic. E theta_HRS E' Rate (GeV) (degrees) (GeV) (Hz for 1 uA beam) 4.4 30.9 2.64 2.9 Hz/uA 4.4 34.1 2.44 1.3 Hz/uA 4.4 61.1 1.29 0.018 Hz/uA 4.4 64.3 1.20 0.014 Hz/uA 4.4 67.5 1.13 0.010 Hz/uA 4.4 70.7 1.06 0.008 Hz/uA 2.2 30.9 1.65 216 Hz/uA ..... angle available when Bigbite removed (can run with sieve) 2.2 34.1 1.57 100 Hz/uA 2.2 40 1.42 29 Hz/uA 2.2 45 1.30 11.7 Hz/uA 2.2 80 0.75 0.27 Hz/uA .... run here at 40 uA (without sieve) 2.2 90 0.66 0.15 Hz/uA
back to main page: https://hallaweb.jlab.org/wiki/index.php/L-HRS_for_SBS