Magnets

In the process of editing and updating this page. Please contact Juliette Mammei crowder@jlab.org with questions or suggestions.

PREX Main<< HOW TOs

Nominal Settings

PLEASE READ HOW-TO BEFORE SETTING THE MAGNETS!!!!!

• Below are set points. Readbacks will be a bit lower.

• LHRS

Dipole	Q1	Q2	Q3
p0 = 0.95285	118.50 A	407.70 A	450.76 A

• RHRS

Dipole	Q1	Q2	Q3
p0 = 0.95284	118.55 A	404.07 A	446.90 A

Setting the Magnets

If one can not reset the magnet remotely: Do NOT go into the hall to reset by yourself. Contact RC and then tech on-call/magnet expert.

For PREX, regulators for Q1, Q2, Q3 are always OFF and only used for the dipole. Q1, Q2, Q3 magnets will be set by current until further noticed.

Set HRS Magnets

1. Clear all faults (if there are still problems with flows or liquid levels there is no point ramping back up to crash again).
2. Check regulator OFF for Q1, Q2 and Q3. Leave the dipole regulator ON
3. Set the momentum of the spectrometer you want. The dipole should start moving towards that setting. The NMR will be set too. Q1, Q2 and Q3 will not change.
4. Turn on the Q1 power supply if not on already
5. If turning a quad magnet down, we do not need to cycle the magnet. Just set the set point.
6. If turning a quad magnet up, it must be cycled to always follow the same hysteresis curve
   1. Right:
      1. Q1: The RQ! should be taken to 900A. Let it stay at 900A for about 2 minutes before loading the desired set point. (NB in the past the RQ1 has had problems reaching 900A so if you cannot do that make a log entry and go to 700A)
      2. Q2: The RQ2 should be run to 1400A. Let it stay at 1400A for about 2 minutes before loading the desired set point.
      3. Q3: The RQ3 should be run to 1400A. Let it stay at 1400A for 1 minute before loading the desired set point. Do NOT leave RQ3 at 1400 A more than 5 min (but leave it there for 1 min)!!
   2. Left:
      1. Q1: The LQ1 should be run to 900A. Let it stay at 900A for about 2 minutes before loading the desired set point.
      2. Q2: The LQ2 should be run to 1600A. Let it stay at 1600A for about 2 minutes before loading the desired set point.
      3. Q3: The LQ3 should be run to 1600A. Let it stay at 1600A for about 2 minutes before loading the desired set point.

Set Septum Magnet

Figure 1 - Hall A Septum with beam off.

• The polarity of the septum is positive
• Instructions for setting the current Jack's elog entry.

To check the septum current:

• In JMenu:
  • Operations < Magnets < Special Hall Magnets < Septum Magnet (Hall A)
  • The Hall A Septum screen will come up (see Figure 1)
  • Cycle the magnet to 400 A.
  • Set it to 333 A -- nominal Tune.

Monitoring the Magnets

HRS

GUI can be found at:

OPS Menu -> EDM (HLA) -> Hall A -> Tools Display

How to check polarity

LHRS dipole, RHRS Q1 and dipole polarity changes require an access. The rest can be changed with the power supply gui.

One should check the polarity with Gaussmeter. The Hall probes should read positive for positive particles and negative for negative particles (WITH CURRENT IN THE MAGNETS)

Septum

GUI can be found at:

OPS Menu -> EDM (HLA) -> Hall A -> Magnets -> Super Big Bite