As most of us sit back and enjoy the summer holidays, the JET shutdown continues in its rhythm of twoshifts- per-day, seven-days-per-week. The shutdown team is in the process of changing all of the machine’s plasmafacing components to the combination of beryllium and tungsten foreseen for ITER (see FN December 2009). By August, nine months into the shutdown, a key milestone had been reached with virtually all of the carbon components removed and the ‘naked’ vessel having been surveyed in detail to confirm the geometry of the machine prior to proceeding with the installation of the beryllium and tungsten components.

Before starting to install the new tiles, the machine will be thoroughly cleaned using a specially designed vacuum cleaner that is remotely operated. This will remove residual carbon dust resulting from the previous operation to ensure that it will not influence the results obtained with the new metal wall. The installation of the wall will then commence with the re-installation of the beam which holds the diagnostics for measuring the plasma-generated magnetic field.

Another important component of the present enhancement of JET is the upgrade of the suite of diagnostics, with particular emphasis on systems that will help to study the interaction of the plasma with the new wall. Many of these new diagnostics, especially those based on spectroscopy, require calibration. A new remote handling-compatible calibrated light source has been developed and will be used to calibrate these systems ‘end-to-end’, including the in-vessel optical components, like lenses, windows and mirrors. In a similar manner, a strong neutron source has been hired and will be deployed on the remote handling boom to enable the calibration of the JET neutron diagnostics. As with many of the procedures and techniques being used in this JET shutdown, progress is being closely monitored by colleagues at ITER, who are hoping to develop similar techniques.

The target shutdown duration remains at 65 weeks. In early 2011, JET will be restarted with a new all-metal first wall, an increase of neutral beam power from 23 to 34 megawatts and a significantly enhanced set of diagnostics. The preparations for scientific exploitation of these new capabilities are already well underway and the high level of participation of scientists from around Europe attests to the excitement that these new capabilities have generated within the community.

More information in JET’s shutdown weekly:

Lorne Horton, EFDA-JET