Fuel Retention Diagnostic Setup (FREDIS) for desorption of gases from beryllium and tritium containing samples

Abstract

In fusion devices, the retention of the fusion fuel deuterium (D) and tritium (T) in plasma-facing components (PFCs) is a major concern. Measurement of their hydrogen isotope content gives insight into the retention physics.In FREDIS, two methods of thermal desorption are used for retention measurements: In Thermal Desorption Spectrometry (TDS) the samples are heated by 6 infrared lamps up to 1433 K with linear temperature ramps of up to 1.67 K/s. The desorbed gases are detected up to 100 amu/e with a double-QMS (Quadrupole Mass Spectrometer) that can distinguish between helium and D2 and uses an innovative differential pumping system.In a connected vacuum chamber, a ∅3 mm spot can be heated on the sample surface by a high energy Nd:YAG laser pulse (E0 < 100 J) within milliseconds (0.1–20 ms) to several thousand degrees. This method of Laser-Induced Desorption (LID) can also be applied inside the fusion chamber and is planned as in situ retention diagnostic for ITER. In FREDIS, LID is thus tested and used as ex situ analysis method utilising the same double-QMS for absolute quantification. FREDIS is capable of handling beryllium (Be) by means of glove boxes and in the future also tritium using a tritium trap to analyse also samples from JET and ITER. In this contribution we present the specifications of FREDIS and compare TDS and LID.