Neutral particle energy analysis and charge exchange power loss in edge-dominated spheromaks

Abstract

Neutral particle density profiles have previously been calculated for spheromak plasmas [Phys. Fluids B 2 (1990) 115]. Here, the formalism is extended to calculate the one-dimensional (1-D) profile of the egressing neutral energy flux to correctly treat profile and attenuation effects. If is found that the energy flux profile is strongly dependent on Ti,Te,ne profiles and magnitudes, and regions of the plasma have been identified as localized ‘‘hot spots’’ for charge-exchange power loss in some cases. In addition, the total charge exchange power loss is found to be in order-of-magnitude agreement with predictions from a zero-dimensional (0-D) model and can account for the bulk of the edge-dominated spheromak power loss.

Time of flight measurement of ion temperatures in spheromaks

“…It has been established that neutral gas particles (of the majority ion component) appear in large con-centrations (several times the edge plasma density) in the periphery of some classes of spheromak discharges [3,4]. Because of this as well as the low edge electron temperatures (T eedge <, 30 eV) in these experiments and multiple generation CX processes, neutral particles are able to penetrate the plasma core to distances much greater than their ionization mean free path [3,17,18]. Central plasma neutral concentrations of 0.01-0.1 rig can be expected [3].…”

“…5 shows. This could be due to shorter mean free paths for CX neutrals caused by lower Tj during this period (300-500 ixs) [3,18] or to lower edge neutral density after plasma formation.…”

“…Central plasma neutral concentrations of 0.01-0.1 rig can be expected [3]. These particles are then available for CX interactions with hot ions in the plasma core and may escape the plasma with a certain probability, which is proportional to the ionization and CX rates [18]. The escaping neutrals carry with them the core plasma ion temperature from the 'soft' CX interaction [3,18,19].…”

“…These particles are then available for CX interactions with hot ions in the plasma core and may escape the plasma with a certain probability, which is proportional to the ionization and CX rates [18]. The escaping neutrals carry with them the core plasma ion temperature from the 'soft' CX interaction [3,18,19]. Hence, these particles provide an excellent means of ion diagnosis which does not rely on line broadening.…”

Ion heating and magnetohydrodynamic dynamo fluctuations in the reversed-field pinch

“…The neutral flux simulation code NEUCGA [12,13] was used to model the neutral flux from MST, and attempts were made to reproduce the observed changes in T, and total neutral flux by changing the T h T e , and n e profiles. The required profile changes were inconsistent with the line-integrated density measurements made with a CO2 interferometer [14].…”