BNMR: EPICS

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Introduction

Experimenters will need to display the Epics Control Pages in order to run the bnmr or bnqr experiments. They must also ensure that BNMR has been granted write access to the required Epics parameters as described below, or they will not be able to change the relevant beamline controls.

Display ISAC Epics Control Pages

Switch onto a different desktop on linux box isdaq01 (or isdaq06) so the Epics Control page does not clutter the desktop used for running the experiment. Access the epics control pages on isacepics1 with ssh from an xterm window, as follows (if you don't know the password, ask a group member).

ssh bnmr@isacepics1
( Type in the password )

You should see the main ISAC EPICS control page come up after a few seconds.

Note

There is no bnqr user account on isacepics1. The bnmr account is used for both experiments and the same EPICS access permission (i.e. BNMR) applies to both.

Write access to Epics Parameters

Most Epics parameters can be read by anyone, but write access has to be granted by the Controls Group. On the mainEPICS Control Page there is a button labelled "Access". Click on this button. This will show the current "Access". For the bnmr and bnqr experiments, "Access" must be set to BNMR, or it will not be possible to run in any #Experimental Mode that requires write access to one of the required IOCs. Testing the DAQ can be done in Single Channel Mode using frequency scans, but running a NaCell scan or Dual Channel Mode will not be possible without "Access" set to BNMR. If access is granted to BNMR, this includes BNQR.

Therefore, at the beginning of the bnmr / bnqr beam period, ensure that the "Access" parameter on the main ISAC Epics controls page is set to BNMR '. If "Access" is NOT set to BNMR, telephone the Control Room and ask them to change the Access.

Even when "Access" is granted to BNMR, only those EPICS IOCs relevant to the experiment can be changed by the experimenters from the EPICS Control pages, e.g. Helicity, and all BNMR/BNQR parameters for single/dual channel mode control.

Some of these parameters are also writable by the bnmr and bnqr BNMR and BNQR VMICs (lxbnmr,lxbnqr). They have been granted write access by the Controls Group to allow the frontend programs to flip helicity and turn the beam on/off via PPG signals. The frontends also use Channel Access software to scan the NaCell voltage, for example.

WARNING

There is NO protection against users changing Epics parameters via the Epics Control pages or the frontend programs while an experimental run is in progress on either bnmr or bnqr DAQs. Users must ensure that they know what they are doing!