TOF HV Operations Manual

Last modified: January 15th 2010, by Bertrand H.J. Biritz

The TOF HV system is comprised of a CAEN SY1527LC main frame and four CAEN A1534 Positive/Negative boards which can supply +/- 8000V respectively.

The main control interface EPICS consists of two components the underlying Input/Output Controller (IOC) and then the MEDM GUI interface. The later provides a graphical overview of the Process Variables (PV's) which the former supplies. This means there need to be two processes running for the normal operation of the HV controller. This interface was written by me (Bertrand H.J. Biritz) - so you know whom to complain to :)

There also is telnet interface provided by CAEN in order to control the main frame (and subsequently the boards). This should be considered a backup to the EPICS interface. If certain problems arise then the expert might advise you to log in or he/she will do so remotely.

EPICS Interface

Starting the MEDM GUI

From the alarm handler main window click on the button labeled P to the right of the TOF_ALARMS group button - read the overview section if you don't understand the instructions. This should launch the following display

Main Window

Depending upon the status of the HV, the display colors might be a little different (i.e. red, yellow, blue or white instead of green).

Seeing the channel details

Normally one does not need to look at the channel details, however if one of the sectors is not green then the Operator panel shows you detailed information about the particular channel. Click on the HV button next to a particular sector to bring up this panel

MEDM Operator

here you can set the operating voltage, turn the channel on/off or also enable/disable it.

Expert Settings

A final panel allows you to set such values as the ramp up and ramp down rate. From the Operator panel you have to click on the Expert Settings button to get the following

MEDM Expert

These settings are to be only changed under the advice of the expert.

Telnet Interface

Telnet'ing in

In a terminal type telnet_caen which should cause the following screen to appear


if not, please see the trouble shooting section.

After pressing any key, type in admin for the username and contact a TOF expert for the password (press tab to move between the fields)


This will bring up the main menu


Controlling the channels

Press tab in order to access the menu bar options and select Main->Channels

channel control

this will change the display to

main channels

Setting a channel voltage

In order to adjust the voltage use the arrow keys go to the V0Set column and the appropriate channel row. Then enter 7000 as the desired value and press return to enter the value.

Turning on/off a channel

To turn on/off a channel use the arrows keys to move to the Pw column and the desired channel row, then press the space bar to toggle the channel on or off. The Status column should reflect this change (i.e. Ramping up or Ramping down respectively).

Checking channel status

To check the channel status use the arrow keys to have the Status column displayed. Under normal operations there should be nothing displayed, possible statuses are
Ramping UpNormal
Ramping DownNormal
Over CurrentCall Expert
Over VoltageCall Expert
Under VoltageCall Expert
External TripCall Expert
Max VoltageCall Expert
External DisabledCall Expert
Calibration ErrorCall Expert
UnpluggedCall Expert

Checking board status

To check the board status use the arrow keys to have the BdStatus column displayed

board status

Under normal operations there should be nothing displayed. Possible failure statuses are

Power Failure Status
Firmware Checksum Error
HV Calibration Error
Temp Calibration Error
If any of these are displayed the expert should be called.


The first and foremost rule is

Don't get creative, call for backup

If you run into any of the problems listed below the expert should be contacted - doubly so for ones which aren't listed! I have compiled these trouble shooting items for a couple of reasons:

HV reads 0 or HV On/Off button missing

If the main TOF window looks like this

HVIOC reconnected

It is due to the IOC having lost and then regained connection with the HV mainframe. To correct this situation you will first need to launch a terminal and type screenHVIOC

screen HVIOC

after you have pressed return you will be inside of a screen session containing the HV IOC. You should see at least one "lost connection & regained connection" message

HVIOC reconnected

To shut down the IOC type exit and press return

Exiting HVIOC

This is how the terminal should look after exiting

HVIOC reconnected

Next check to see if there are any orphaned semaphores by typing ipcs at the prompt


If there are, you will need to clear them one at a time by typing ipcrm -s and the particular number as shown above.

Once any semaphores are cleared you can relaunch the HV IOC using the usual TOFHV_IOC command. Use screenHVIOC to once more check on the status of the IOC and make sure it hasn't lost connection again - if so repeat the above steps.

To disconnect from the HV IOC you will need to press ctrl+A, ctrl+D, which will give you a "detached" message - else you just shut down the IOC once again!

Detaching from screen

telnet_caen command not found

When trying to telnet into the CAEN main frame you get the error message command not found, then there is something wrong with the Bash shell alias.
In order to telnet in type the following in a terminal:

telnet 1527
unless there are other problems this will bring up the usual terminal interface.

I set up a shell alias in ~/.bashrc so you don't have to type the above - which apparently has been changed. To have this problem fixed please contact the expert.

telnet_caen: No route to host

If you receive a no route to host error message while trying to launch telnet_caen, then there is most likely a networking problem. There isn't much that can be done at that point without an access to test the network cable.