First Measurements of Gas Balance and Chemical Composition in the MK I Pumped Divertor Phase of JET using the Gas Collection System

摘要

1. When the divertor cryopump is off, the results of the gas balance and short term wall retention are in good agreement with results found in previous JET campaigns (1989-92) for a Beryllium coated machine, both for C and Be divertor targets tiles.rn2. The cryopump reduces the wall retention. This implies a low D (and T) inventory, despite the large fuelling required to maintain a set plasma density when the cryopump is on.rn3. High performance long ELMy H-mode pulses, with low gas input and high input power deplete the wall from the Deuterium reservoir in the wall. Net wall depletion occurs also during long high density L-mode plasmas, near detachment.rn4. For pulses with Nitrogen seeding the measured composition of the output gas is different from the input gas, and in particular is enriched in Nitrogen.