SEPTUM OPERATIONS from EPICS

Please send comments or questions to John LeRose: lerose@cebaf.gov

Important Phone numbers:

 

The EPICS screen for septum magnet control can be accessed as follows. From the Hall A Main Menu select Magnet Controls then from the activated pull down menu select Septum Right (or Left) Controls. A copy of the EPICS screen is shown below in Figure 1.

Please note that the cycle from command to action can be quite slow so expect to wait many seconds for an indication of command execution. The steps below must be used to prepare the septa for energization.

Energizing the septum:

n.b. Except for step 1, which requires a Hall access, NEVER proceed to the next step without successfully completing the verifying observation. If the verifying observation is not satisfied call an expert for consultation.

 

Action

Verifying observation

Step 1

Turn on Power supply in the Hall (techs do this)

 

Step 2

Clear interlocks

all green status in lower left of Septum Right (or Left) Controls page

Step 3

Verify operating conditions

(check white board and halog for updates on operating conditions)

  • Coil Temperature ≤ 8 K
  • Helium Level ≥ 75%
  • He Gas Flow L1 & L2 ~ 10.6 SLM

Step 4

Dump Switch CMD ON

Observe green light next to ON/OFF

Step 5

Power Supply CMD ON

Observe green light next to ON/OFF

Right septum note

Step 6

Enter desired current in the Set Current box (or type in the desired P0 on the Hall A Tools GUI) see: autoset

Magnet coil voltage and current increase.

Step 7

Continuously verify proper operation

  • He Gas Flow L1 & L2 should increase with current.
  • Coil temperature remains stable during ramping

 Right Septum Peculiarity: (5/27/05)

Sometimes, when the right septum has been off for a while, step 5 above triggers the quench protection circuitry and the power supply shuts down. Going back and repeating steps 2 through 5 takes care of the problem. We don’t know why!

Septa Settings are Now Automatic: (6/9/05)

Update 8/1/05: This feature has been disabled at the request of the HAPPEX Collaboration.

The septum controls have been changed so that henceforward, when you type in P0 on the Hall A Tools GUI the set current for the septum in that arm will be automatically updated. This is new, so shift workers should still verify that this has been done correctly and make sure both the "set current" AND "Magnet Current" are coming out properly (the "Magnet Current" is slightly offset from the "set current").

The prescription used was:

Right Septum “set current” = 92.58 * P0 (“Magnet Current” = “set current”-2.2)

Left Septum “set current” = 94.22 * P0 (“Magnet Current” = “set current”-3.2)

(These parameters will have to be updated for 9 degree running.)

As with all the other spectrometer magnets, typing in the same P0 as is already there will not update anything. Also, if you type a different set current in the septum magnet control GUI it will override the one installed by the software the last time P0 was updated. Be careful about typing in new P0's if someone is working on the magnets.

Note re “Magnet Current”: The readback is fairly noisy. The recommended way to determine the actual magnet current is to observe it on a strip chart (a clear baseline value should be obvious after a minute or so).

 

Blank (white spaces) control screens? This usually means the septum IOC has crashed or hung up somehow. The cure is to reboot the IOC (iocha49). You do this over the web. Go to http://hareboot7 (NB this is sometimes updated. Check the IOCs button on the “Hall A Main Menu” to make sure hareboot7 is the one you want). You'll be asked for a username and password (on the wall with the other passwords etc.) Next to iocha49 (verify this from the IOC’s button on the “Hall A Main Menu” too) select "immediate reboot" and then click on "apply". In a few minutes everything should be back (be patient). Observe via the strip charts that the current hasn't changed in the magnets. Then, just for the sanity of whoever comes after you, retype in the set current values on the septum controls (they will read zero after the reboot).
If this happens during data taking make sure you make a log entry.

ESR Crash: In the event of an ESR crash immediately begin ramping both magnets down to zero. (Type 0. In the set current fields of both septa.)

 Figure1

Sample Septum Epics control screen.

Monitoring system variables

There is a display of system temperatures, pressures, liquid levels, VCL coolant flow rate, coil voltage ,magnet current, vacuum , VCL voltage, valve positions, and interlock status. These parameters can be plotted by stripchart to view trends .

 

Magnet dump recovery

Without quench

A discharge by either fast or slow dump without a quench usually can be recovered fairly quickly. If the coil temperatures are OK one can proceed to reenergize the magnet as described above.

 

With quench

A Fast dump with a quench requires a longer wait to return the septum to normal temperatures. A one to two-hour recovery from a 350 amp quench is normal. The main reason is that all the magnet's stored energy is dumped internally in the coil due to the extremely fast spread of the quench. The current will dump in a few seconds and the power supply will automatically shut down. The present digitally controlled fast dump switch is not fast enough to remove any significant energy from the magnet. A planned upgrade to an all analogue fast dump will be able to remove some of the energy and lessen the recovery time. Recovery goes as follows:

    1. Observe normal system temperatures
    2. Follow startup procedure above

 

Name

Office

Pager

Home

John LeRose

7624

584-7624

565-5060

After Hours, 1st consult the Run Coordinator, then call Tech-on-Call[*]

See the white board

Mark Stevens

6383

584-6383

 

Heidi Fansler

6915

584-6915

 

Paul Brindza

7588

584-7588

 

 


 

 

 

 



[*] Calling Tech-on-Call after hours requires Run Coordinator, or higher, approval.