Spectrometer Rotation

SPECTROMETER ROTATION INSTRUCTIONS

Before we begin... Rotating the Hall-C spectrometers is pretty easy ... maybe too easy! Remember that you're moving a very large, very heavy object that can do lots of damage if it hits something, runs over something, or pulls on a cable or rope that is tied to something else. If the Hall-C technicians or engineers have certified the spectrometers as 'ready for rotation' then it is safe to proceed -- unless there is the possibility that you or somebody else left a cable, ladder, hose, etc. in the wrong place since the technicians checked. Just THINK before you act.

The limits for remote rotation are discussed here: Guidance for SHMS/HMS rotation. When desired angles fall outside the remote rotation limits, rotation must be done by an expert (Steve Lassiter) while in the Hall.

Rotation GUI Screen -- Rotating a spectrometer

 The rotation control screen is part of the Spectrometer Magnets GUI. If you need to start it, the magnet screen is brought up on any hcdesk machine by the command go_magnets.

• Open the Rotation GUI by clicking on the ROTATION button on the top left of the magnet screen:

• The rotation screen will now appear. The same screen controls both the HMS and the SHMS. Do not try to move both spectrometers at the same time.

The large box on the right will have a green button indicating which spectrometer is Selected. If you want to rotate the other one, press the grey button that says Select (the other one). In the screen image below, the HMS is Selected for rotation.

• On this screen, the current HMS angle is shown to be 13.5 degrees. A new angle (30 degrees) has been entered in the Rotate To: box. By typing 30 and pressing RETURN (or ENTER) on the keyboard, this will set the new rotation angle.

• Next, press Push to Enable. Three buttons, START, RESET, and STOP will appear, as shown below.
  • To begin moving the selected spectrometer,
    1. press RESET,
    2. Wait 10 Seconds,
    3. then press START.
  • You should monitor the rotation progress on both the GUI and on the TV camera that views the correct angle scale.
  • If needed, you can halt spectrometer movement by pressing STOP.
  • If there is no movement within 15 seconds after pressing START, hit the STOP button or you may have to go into the hall to reset the shunt trip breaker!!
• If you want to back out of the procedure without moving the spectrometer, press the RESET button and then Select (other spectrometer).

Status Lights / Rotation Faults and Interlocks

Please record all interlocks or error messages that pop up on the interlock pages as this is a great aid in debugging what has failed.

The box on the lower-right of the rotation GUI shows the rotation system status. Generally, GREEN is good. RED indicates that something is wrong.

• Power On, Remote, and Auto should have green indicators.
• The square HMI Alive indicator to the left of the status box should be green, indicating that the control system is actually working and the process has not hung or crashed.
  • If the HMI Alive indicator is red...
    1. Try killing and restarting the 'go_magnets' screen.
    2. If that does not work, contact Hall-C Engineer On Call.

Any RED status lights indicate a fault that needs to be cleared before you will be allowed to rotate. Here they are and the procedure for clearing each one:

• HMS Drive Controller

1. This fault condition will prevent both HMS and SHMS from moving.
2. With HMS Selected, press RESET to attempt to clear the fault.
3. If it will not reset remotely, contact an expert who can enter the hall to reset the Shunt Trip Breaker.

• SHMS Drive Controller

1. This fault condition will prevent both HMS and SHMS from moving.
2. With SHMS Selected, press RESET to attempt to clear the fault.
3. If it will not reset remotely, contact an expert who can enter the hall to reset the Shunt Trip Breaker.

• Proximity Switch Indicators mean that a spectrometer position limit switch has been activated. Normally, this should not occur. Contact the Hall-C Engineer On Call.
  • SHMS Forward Prox.
  • SHMS Reverse Prox.
  • HMS Forward Prox.
  • HMS Reverse Prox.

• HMS input angle close to minimum angle.
  • Watch the live video extremely closely so as not to exceed minimum angle. If it going to exceed, hit the Stop button in the GUI. If this does not work, hit the Rotation Crash button for the HMS.
• Input angle for HMS will violate minimum spectrometer separation angle.
  • See the spectrometer separation criteria at Guidance for SHMS/HMS rotation
• SHMS input angle close to minimum angle.
  • Watch the live video extremely closely so as not to exceed minimum angle. If it going to exceed, hit the Stop button in the GUI. If this does not work, hit the Rotation Crash button for the SHMS.
• Input angle for SHMS will violate minimum spectrometer separation angle.
  • See the spectrometer separation criteria at Guidance for SHMS/HMS rotation

Adjusting the angle offsets

• The TV cameras are the primary references for the spectrometer positions (angles). The digital readouts shown in the GUI windows rely upon a passive wheel with optical encoder and a couple of calibration constants. It is possible for the wheels to slip over time.
• If the digital readout has drifted far from the TV readout, you can adjust it (for each spectrometer separately):
  1. Make sure that NEITHER spectrometer is moving.
  2. In the 'offset' box, enter the difference [TV_Angle - GUI_Angle] (rounded to nearest 0.01 degrees) and press ENTER or RETURN.
• Repeat the last step until the difference is less than 0.01 degrees.

A few logbook entries from December, 2017

• Rotation of HMS working now
• Summary of work to restore spectrometer rotation control
• Follow-up Re: Summary of work to restore spectrometer rotation control
• Rotation controls updated <-- A bug in the rotation code was fixed here.