Posted on: 28th October 2007

picture of CODAS administrator in the JET control room

JET is currently coming to the end of a “Shutdown” period – a time when substantial maintenance work and upgrades to the Facilities are performed while the JET machine is not in operation. Shutdowns are not a relaxing time for CODAS, the department responsible for JET’s Control and Data Acquisition System. New user-software has to be prepared, new hardware and associated software accommodated, new diagnostics installed, and then there are the computers!

At the end of all major JET Shutdowns checks are made, subsystems rehearsed and then full test countdowns are run. CODAS needs to demonstrate its readiness for Operations and the rehearsals are performed around a month in advance to give sufficient time to iron out any bugs.

Immediately prior to the rehearsals, CODAS’s Computer Administrators install all the latest software, any user-requested upgrades, and any computer upgrades onto every computer cluster. When completed, each individual subsystem is put through its paces to ensure that its performance has not been impaired and to confirm that it behaves as expected.

To avoid systematic errors, each subsystem rehearsal is performed by a Subsystem Responsible Officer who is not actually responsible for the subsystem he is rehearsing. This is concluded by running a dummy JET pulse on each subsystem to ensure it is individually ready for Operations.

When the subsystem rehearsals have been completed and any issues resolved, it is time for the full CODAS Rehearsal. Under safe conditions a full countdown is performed with all subsystems included. Finally, when the last few anomalies have been resolved, which might take several pulses, CODAS is declared “Ready for Operations”.

This step, achieved on 18th October 2007, is just one part of the long commissioning process which must be carried out at the end of any major JET Shutdown.