Posted on: 13th May 2013
The upgrades, repairs and calibrations have been completed, the remote handling booms have been retracted, the ports sealed and pumping the air out of the JET torus has begun.
The main purpose of the shutdown has been to enable examination of the behaviour of the new ITER-Like Wall during the recent experimental campaign. Marker tiles that were placed in various locations around the vessel have been removed and can now be analysed to see whether the tungsten and beryllium surfaces were eroded, and if so where the eroded material was deposited.
Preliminary results on the ITER-Like Wall’s status will be presented next week at the 14th International Conference on Plasma-Facing Materials. “It’s early days yet, but at the moment the wall seems to be much cleaner than expected!” says Task Force Leader Guy Matthews.
During the shutdown the opportunity was taken to calibrate a number of the instruments, most notably the neutron detectors, and to tune up some of the systems, such as the neutral beam injection heating, ready for the high power experiments planned in the coming campaign.
Bringing an experiment as large and complex as JET back into a readiness for operations is a serious process. Initially there is leak testing and baking the vessel to remove gases adsorbed onto surfaces. Then there is two weeks of dry commissioning of power supplies and heating systems before finally fuel is added and plasma created in the vessel. But still experiments are not performed for another couple of weeks while the engineers ensure all the systems are perfect working order: only after these tests are successfully completed are the scientists able to take over the controls and begin experiments.
The plan has the experimental campaign beginning in early July; just as many people are starting to think about summer holidays, JET’s scientists will be getting into full swing.