Impurity ions temperature analysis

If the flag NLTI2TX=T is set, TRANSP interprets the input ion temperature as temperature of impurity ions. For example, if measurements come from Carbon ionized states with Charge-Exchange sprectroscopy. This flag needs also NLTI2=T, otherwise has no effect.
In computing the feedback, the profile T_i-T_x is computed and smoothed in space. Additional namelist variables include parameters for smoothing and for time convolution.

XTI2TXSM

this parameter control the smoothing and represents a smoothing radius or half width in normalized flux coordinates. The default value is 0.1.

SLVTXSM

This parameter introduces a smoothing in time. The default value is ZERO, i.e. no convolution. Beware that this option causes a time lag and would break during sawtooth crashes and pellet events.

SLVTXS2

This parameter select the type of convolution and assumes values between 0 and 1. Zero means no convolution, i.e. full time lag, while unity is for a full forward time convolution. This would reduce the time lag, but also overshoots intermediate time stamps for intermediate results.

Using a time convolution is strongly discouraged.

Most of TRANSP treats the ions as all having one temperature, T_i. In reality auxiliary heating can split the species, e.g. causing the impurities to have a higher temperature than the hydrogenic species. Since the fusion reaction rate is tied to the hydrogenic species temperatures, but diagnostics usually see the impurity temperatures, it is of interest to calculate the difference.

Starting from the ion power balance (either interpretive or predictive runs), TRANSP estimates the temperature partition between main ions and impurity ions. There are three possibilities for the ion temperature profile, either from impurity (T_x) or from main ions (T_MJ) or an average of the two (T_AV). The average temperature is defined as (n_xT_x + n_mj*T_mj)/(n_x+n_mj)
The assumption is that the temperature that comes from TRANSP is an average temperature, and thus both T_x and T_MJ are evolved independently around the average value. However, if NLTIPRO=T or NLTI2=T, but NLTI2TX=F, then the corrections are controlled with the flag NSLVTXI, described below.

NSLVTXI=1

With this value the ion temperature data are interpreted as majority ions temperature ( H/D/T/He3/He4). The subroutine solves for T_x and computes the average T_AV.

NSLVTXI=2

With this value the ion temperature data are interpeted as an average temperature (TIAV)

NSLVTXI=3

With this value (default) the ion temperature data are interpreted as impurity ions temperature.

These controls affect only the output, i.e. the calculated corrections are not used, unless NLTI2TX=T. In this case, a smoothed T_AV-T_x correction is applied to the ion temperature profile input data, which is assumed to be impurity temperature.