Log entry time 18:51:12 on May 15, 2004

Entry number 121857

Last revised 15-May-04 feuerbac@jlab.org

May 2004 2-pass Optics Runplan

Preliminaries

At 6:00 am Sunday, May 16:Beam to Hall A is terminated to begin the Hall C leakage tests. Immediately request a sweep to go to Controlled Access. Set both septum to 0 amps, and turn the HRSL magnets to 0.0 current or momentum, to ramp down in preparation of polarity change by the technical crew who will be arriving shortly.
By noon Sunday, May 16: The accelerator should begin the pass change for Hall A to 2-pass 1.5GeV beam. The Hall A technicians will hopefully be finished in the Hall with the polarity change of left HRS and septum. Advise MCC that the hall can be locked up.

To establish 2-pass beam in Hall A:

1. With no target inserted, raster OFF, have the approx. 5 microAmp beam centered and straight at the target (+/- .100mm for x and y at 1H04A and 1H04B, which are BPMA and BPMB on the tools screen). Insert the BeO target and verify the beam profile.
2. Measure the beam size and halo with a harp scan. Spot size should be less than 200 microns. HALOG the results.
3. Have MCC turn on the RF energy and position locks. Verify on tools screen ("RF on" and "FB on").
4. Look at 1C12 OTR for the beam spot size, which should be consistent with harp scan results.
5. Put in C target, and take a short run to verify beam position and raster size with spot++ (raster size should be ~0.5 x 0.5 mm²)(See further instructions for spot++ below)
6. Adjust both septa to and HRS to put the elastic peak at -4% in delta (see table below). Be certain to cycle Q2 and Q3.

General conditions

Beam position:

Straight and centered on target, meaning less than 0.100 mm for x and y for 1H04A and 1H04B (BPMA and BPMB on the tools screen).

Target, Current and Raster size:

Initially raster should be off and we should have the carbon target in the beam. Ask for 5microAmps. Verify the raster with spot++. Remember you need to have beam and a CODA run going to use spot++.  Bob Michaels has more instructions on the DAQ web page at http://hallaweb.jlab.org/equipment/daq/spot.html.

Septum and HRS Magnets

The septum magnets are controlled by current. For both septa, the current can be calculated as I=92.58 * P₀, where P₀ is the spectrometer momentum in GeV/c and the current is in Amps. For an HRS momentum of 1.550GeV/c, the septum current should be at 143.50Amps. Read back current (labeled “Magnet Current” on the septum controls page or showing as the only septum current on the Hall A tools page) should be within 0.5 Amps of this value.

Prescales

Should be adjusted to give about 500 Hz of single arm T1, T3 each, and 40 Hz of T2 and T4 triggers. There should not be any T5, T6, or T7 triggers so those prescales can be left alone.

Data Taking

Momentum scan

With Raster OFF and 5 microAmps scan the elastic peak across the focal plane by taking runs for 10 minutes at a given momentum (about 250,000 -- 400,000 events) for elastic peak locations of:

Drop in momentum so that you will not need to cycle the quads. Be sure magnets and beam are stable before starting runs. Restore momentum to center the elastic peak in the momentum distribution. (4 hours)

*Raster

At +2%, 0% and -2%, take separate 10 minute runs with the raster on and off, with a raster amplitude (as measured by spot++) of +/- 1 mm and +/- 3 mm. Be sure and HALOG which runs are which in the beginning of run comments. (2 hours)

Beam angle/Bullseye Scan:

Raster OFF: After restoring to the 0% momentum setting:

1. Ask MCC to steer the beam such that BPMA and BPMB read (+2mm/0 and -2mm/0) in x/y.
2. Be sure beam is stable and Feedbacks are on.
3. Perform a harp scan, and then take a ~10min run with CODA
4. Repeat 1-3 for BPMA and BPMB positions of
   1. ( +1mm/0 -1mm/0 )
   2. ( -2mm/0 +2mm/0 )
   3. ( 0mm/0 0mm/0 )
5. For the rest of the Bullseye Scan, we are mainly interested in the position on BPMB, the values of BPMA are only guide-lines. Repeat 1-3 for BPMA and BPMB positions of
   1. ( 0/+2mm 0/+2mm )
   2. ( 0/-2mm 0/-2mm )
   3. ( +2mm/0 +2mm/0 )
   4. ( -2mm/0 -2mm/0 )

When finished, ask the beam to be set to ( 0/0 0/0 ) again.

Energy shifts:

We want to be able to measure, in a controlled study, how well our beam energy readbacks work and how well we can correct for variations in the incident beam energy.

1. Ask MCC to turn off the energy locks, and take a 10 minuterun. HALOG the energy spread striptool. (.25 hours)
2. Ask MCC to turn on the energy locks and adjust the Hall A (arc) dipole Bdl to change the energy by +1 MeV. Take a 10 minute run. HALOG the energy and elastic peak location.
3. Repeat step 2 for +2, -1, and -2 MeV adjustments. Ask MCC to restore the Hall A dipole Bdl to the initial value.

Other studies

Extended target Acceptance/optics check

With raster off, take a 10 minute run on each the Optics 10cm and Optics 24cm targets.

HAPPEX dithering tests

The HAPPEX experiment wants to perform a test of their dithering controls.