BNMR: EPICS

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Introduction

Experimenters will need to display the Epics Control Pages in order to run the bnmr <word> bnqr experiment. They must also ensure that bnmr has been given #write access to Epics Parameters, or they will not be able to change the relevant beamline controls (see #note).

Display Epics Control Pages

Switch onto a different desktop on Template:Linux (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 bnmr 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 account on isacepics1. The bnmr account is used for both bnmr/bnqr experiments and the same EPICS access permission (i.e. bnmr) applies to both experiments.

Write access to Epics Parameters

Most Epics parameters can be read by anyone, but write access has to be granted by the Controls Group. Only those EPICS parameters to which users bnmr and bnqr have been granted write access can be changed by the experimenters, and only if "Access" is granted to the bnmr experiment. As far as EPICS write access is concerned, if access is granted to bnmr, then bnqr also has access.

At the beginning of the bnmr/bnqr beam period, it is therefore essential to 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.

Examples of EPICS parameters to which the controls group have granted bnmr write access are Helicity, NaCell voltage, and all BNMR/BNQR parameters for single/dual channel mode control.

Some of these parameters are also writable by the BNMR and BNQR frontends (PPCs), e.g. Helicity and Sodium Cell voltage. In some modes, an Epics parameter such as the Sodium Cell voltage is scanned. In all modes, the frontend PPC is responsible for flipping the helicity each cycle ( by hardware via a PPG signal to the Epics Helicity switch).

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