Difference between revisions of "Pion-LT specific shift instructions"

Latest revision as of 13:44, 7 June 2022

!!! NEW !!! Mode 10 Running !!! NEW !!!

These instructions are new for the PionLT 2021 run, please read them carefully

During the PionLT run, we want to carefully study the gas Cherenkov detectors. As such, we want to take mode 10 information for all gas Cherenkov PMTs during every run.

• To ensure this is the case, please make sure that the cermode10 checkbox on the prescale GUI is enabled. This should appear as in the image below -

• In addition, we want to take full mode 10 information once per physics setting
• To enable this, select the fadcmode10 check box in the prescale GUI, as seen in the image below -
• These mode 10 runs should be approximately 2 minutes in length
  • The deadtime for these runs will be very high, this is fine, don't worry about this

• Full mode 10 runs should be kept to a maximum of 3 minutes during production running to keep file sizes down
• Once a full mode 10 run for a setting has been completed, please indicate it on the run sheet
  • A hclog entry indicating that a mode 10 run has been completed (including the physics setting info) should also be made

• If these modes are toggled, they will enable the corresponding mode 10 information regardless of any other settings
  • See this logentry for more information

Magnet cycling

[Aug 20, 2020] 
When ramping up the SHMS or HMS magnets, do it in steps to minimize the chance of a trip.  So, ramp to the same MOL current in the end, but get there in 3--4 steps.  There is no need to pause between steps, just watch the magnet screens and adjust the set current in 3--4 stages.  You can do multiple magnets at a time -- just watch them.
(This makes it easier for the lead-flow controllers to reach the needed flow and remain stable.)

• Make sure to follow the appropriate magnet cycling procedure for the HMS and SHMS magnets. The cycling procedure is particularly important when going to a HIGHER momentum setting on the spectrometer.
• The HMS dipole in particular takes a long time to settle. Be sure the NMR is locked and stable before starting to take data!
• When the SHMS is at 10 degrees or below, ask for beam off when cycling magnets.

Setting Spectrometer angles

• Make sure to record all angles to 0.005 degree using the marks on the floor (interpolate to nearest half-division).
• It should be possible to set the spectrometers to within 0.01 degree of the desired value without too much difficulty. At some places the floor is not completely flat and this may be a problem. If so, then set the angle to within 0.03 degree of what is requested, but make a clear record of the actual setting in the hclog.
• Make an elog entry with an image of the floor marker angles on the camera every time you do a rotation.

Small Angle Rotation instructions

General Spectrometer Rotation Instructions

• When the SHMS is at 10 degrees or below, ask for beam off when rotating.
• SHMS angle between 6.25 and 7.00 degrees. Rotation does not need an access, but can only be done by a qualified expert (e.g. Steve Lassiter, Amy Comer). The RC should make arrangements, letting them know in advance of the planned rotation and when it is likely to be needed. They will oversee the rotation remotely, giving instructions to the shift crew. Beam off during the SHMS movement. Pay close attention to the hall cameras while departing the beamline, and be prepared to hit the rotation kill switch, if necessary.
• SHMS<6.25 degrees. Rotation requires a hall access. The Run Co-ordinator will need to arrange in advance which expert personnel (e.g. Amy Comer, Steve Lassiter) and spotters need to be present.
• HMS angles between 11.75 and 12.50 degrees. Does not require a hall access. Follow the SHMS 6.25-7.0 degree instructions above.
• HMS<11.75 degrees. Requires a hall access and experts to be present.

Engineer on Call Cell Number: 757-593-7890

• This is not the tech on call cell phone number.
• It will send out a notification to the other experts to be aware of the small angle rotation changes and what to look out for. They may defer this aspect of their duties to Amy Comer or Steve Lassiter though.

Beam Position

• We would like to control both the position and angle of the beam on target. Unless specified otherwise, please ensure that MCC puts the beam at the nominal position (written on the white board) for both the 3H07A and 3H07C BPMs.

Rates

• Single particle and coincidence rates have been estimated for all runs. Watch the scintillator rates (S1 and 3/4 planes) for each spectrometer for an indication of the particle rate through the wire chambers, and if actual rate is substantially (> 50%) higher than what is listed in the run plan, the RC should be warned.
• We want to keep the particle rate in each spectrometer below 750 kHz, and for some forward SHMS angle runs this will require the beam current to be significantly reduced from the nominal 70 μA value.
• For some low rate runs, it may be possible to use up to 100 μA beam with particle rates still below 350 kHz. Consult with the RC before requesting a higher beam current.
• The prescale values in the run plan are a guide. Adjust them to keep the singles data rate in each spectrometer between ∼100-150 Hz.
• If you change the prescalers, you must update and apply them in the GUI by clicking save before you start a new run

• Please be aware that the GUI sometimes "freezes" and does not update. Please check that it is still alive and corresponds to reality in terms of rates.
  • This issue is very common when prescales are updated in quick succession.
  • To check if this is an issue, examine the run-start screen and ensure the prescale values listed in the run description match the GUI and what is needed for the run.
• Please also be aware that the GUI sometimes miscalculates the EDTM scaler rate when the GUI is being changed and does not update properly.
  • To check if this has occured, examine the coda-flags file in the run-start hclog. Ensure both the desired and scaler EDTM rate are correct.
• If the GUI needs to be corrected due to an update error, first try reentering the values and saving again. If this does not resolve the issue, close and reopen the prescale GUI.
• All run times assume 100% running efficiency. Adjust the time for actual delivered beam time, and let the RC know if the efficiency drops below 60% for an extended period.

Replay

• Detector check replay to be done on first 50,000 events of every run, and compare plots with the standard ones in the binder. In addition, we want physics replay to be done on every run in its entirety. pi+ plots such as missing mass, t, W, Q^2 and phi should be checked for anomalies. Full replay instructions available here.
• Do not start the full physics analysis until after the run ends!

• Keep standard.kinematics up to date with the spectrometer settings for every configuration, so that the physics replay generates meaningful quantities. Use the beam energy determined from the arc measurement in the file, and the spectrometer angles from the TV.
• For aluminium dummy target runs, do not set the target mass to be aluminium in standard.kinematics, it should be the mass of hydrogen still!
• Shift leaders are asked to keep a running total of the number of e-Pi coincidence events falling within the missing mass and fiducial volume cuts set in the physics replay script, so that we can better estimate when to move to the next setting.