Apr 05, 2016
68 Tantalum Langmuir probes imbedded in Phase I graphite divertor

A complex system of Langmuir probes was designed and manufactured for the WEST divertor for local measurement of plasma flux to target. The delivery of the probes at IRFM - an in-kind procurement of the IPP-Prague to the WEST project - is the result of a long lasting and a very productive collaboration between the two institutes.


It is an exciting time at the WEST project as a myriad of packages arrives on site containing shiny new diagnostic components that for the past few years only existed as ideas and drawings. One of the new diagnostic systems is an array of Langmuir probes that will monitor the plasma just in front of the divertor targets in which they are embedded. Probes suffer the same harsh conditions as the divertor itself, and are tricky to design because they must remain electrically insulated, while at the same time have good thermal contact with the target to avoid overheating. In collaboration with one our traditional partners, our friends at IPP-Prague, a probe design was conceived that meets the measurement requirements and survives the predicted heat loads in WEST. The probes are made of tantalum, tungsten's neighbour on the periodic table of the elements, with a very high melting temperature (3000°C), but unlike tungsten, with very high ductility. These properties lead to a robust, compact design. Following successful high heat flux testing of prototypes in the GLADIS device, a total of 58 divertor Langmuir probes were manufactured in-kind by IPP-Prague, as well as 10 probes for the inboard bumper limiter which will be used for plasma start-up studies. The probes were received on-schedule at Cadarache and will be eagerly awaiting their first taste of plasma when WEST begins operation later this year.


Last update : 05/02 2016 (526)