An increased understanding of recycling in tokamaks by mass spectrometry; principle and application in TFR

Time-resolved mass spectrometric measurements of the H/D ratio in the neutral gas during TFR discharges were made. An analysis procedure, based on a zero-dimensional model, has been applied to the data, giving in principle the time evolution of the ion densities, of the particle confinement time, and of the wall inventories. Evidence is presented for (i) rise of the nsub(H)/nsub(D) ratio during the discharge, upon H to D isotope-exchange experiments, and (ii) increased wall desorption and recycling during ICRF plasma heating. Uncertainties in the procedure are discussed