Mass‐Sensitive Ion Probe for Plasma Boundary Characterization on the Tokamak ISTTOK

Abstract

The principle of the mass-sensitive ion probe (MSIP) operation consists in a time-of-flight (TOF) analysis of the ions in the burst excited by a short (μs-range) voltage pulse applied to a small grid immersed into the plasma. The ions in the burst propagate along the magnetic field lines of the tokamak with velocities determined by the value of the applied voltage and by the ions mass/charge (mi/Zi) ratio. The ions of different species and charges separated along some distance (TOF path) from the grid are detected by a retarding field energy analyzer (RFEA). This paper presents description of the MSIP design and first operation on the tokamak ISTTOK. The preliminary results of the obtained mass-spectra are presented and discussed.

Influence of impurities on ion temperature measurements in the tokamak scrape-off layer by retarding field analysers

“…The absolute flux of each impurity charge state is rarely known in general [10,11,[13][14][15]. Nonetheless, the impurity ions are considered as a small, unperturbing, minority by assuming fuel Z = Z , the charge of fuel ions (typically 1  Z for deuterium D + ).…”

“…RFAs do not directly measure T i , but T i /Z, meaning that a charge state of the incident ions Z has to be assigned. The absolute flux of each impurity charge state is rarely known in general [10,11,[13][14][15]. Nonetheless, the impurity ions are considered as a small, unperturbing, minority by assuming Z = Z fuel , the charge of fuel ions (typically Z = 1 for deuterium D + ).…”