Laser Control

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Laser Control Menu

  1. Log onto hacsbs2 using account hacuser, password is on the wall.
  2. enter the directory Hall_A_Tools and execute NewTools
  3. EOS menu -> EDM(HLA Main) ->Polarized He3 -> Main Laser Control

COMET Laser Control

Each of the COMET Laser Control is divided into to parts representing two controllers we're using at the same time as you see in the snapshot.

  • The top one is for the Diode Driver, which is the power supply of the laser diode and controls the current.
  • The buttom one is for the Temperature Controller, which is controlling the diode temperature so that the wavelength of the output laser is stablized.

Laser control.png

Diode Driver

The control of the diode driver has three sections:


Always turn ON the temperature before turn ON the laser diode

There are four clickable options and three indicators

  1. Indicator Comm: Shows the communication status, it should stay green when the communication to the device is good
  2. Options Disable and Enable: Used to enable or disable the laser. The check marks will not be updated automatically, so some time it's may not be in the right place.
  3. Second Indicator: Broken... and always in red....
  4. Options Remote and Local: Used to switch between remote and local mode. The GUI can only read back status and send commends in Remote mode.
  5. Third Indicator: Green means Remote mode and Yellow means Local mode.


The unit in this section is wrong, and should be A instead of mW
  1. Photo Diode Current: Current read back of the laser diode.
  2. Set Current: Only editable place in this section. One can change the laser current by putting new values into the window then hitting enter key.
  3. Current SetPoint: Read back the current setpoint. If one changed the current, this read back value is expected to be changed if the change is succeeded.


The section shows all the status bit, only three of them need to be paid attention

Only Output ON/OFF State is expected to be ON during normal condition.

Any other status bit should be off during production. Here I list some common problems

  1. Output Outside Tolerance: This is on when the laser current is ramping up or far away from the setpoint.
  2. Interlock Disabled: When the interlock is broken for some reason.

Temperature Controller

The control of the temperature controller is very similar to the diode driver with some minor changes:


For the diode safety, always keep temperature controller ON

This section is exactly the same as the Diode Driver.


This section is the same as the Current section of Diode Driver.


This section is the same as the Diode Driver and only the Output ON should be on during normal condition.

Current/Voltage Limit are sometimes ON when the controller is adjusting the temperature and should NOT be treated as a problem.

FAP Laser Control


Currently Used Lasers

  • COMET 1 (W&M): 35A, 26C
  • COMET 2 (Rutgers): 34A, 20C
  • COMET 3 (JLab): 36A, 25C