Event Handling Parameters

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The treatment of the input Ufile data is similar when either pellets or sawteeth are present in the shot being simulated. In both cases a window is specified around the event times during which no Ufile data is used. Instead the data outside this window is used to extrapolate forwards or backwards to the time the event occurred forming a discontinuity there. The windows to be used for pellet and sawtooth events are defined in their respective sections. It is possible to specify a minimum extrapolation window for a particular diagnostic ABC using the variable XDTABC. Setting XDTABC=a would mean that no data for diagnostic ABC was used within a seconds either side of an event. The data which are typically affected by event extrapolation are the temperature, density and effective charge data.

Pellets

NPEL: The number of pellet events during the shot, the maximum is 100.

TPEL: The list of NPEL pellet event times in ascending order of time.

APEL: The atomic weights of the NPEL injected pellets (e.g. 2.0 for deuterium).
APEL values must be drawn from the following sets:
{1.0, 2.0, 3.0} -- isotopes of Hydrogen
{6.0, 7.0} -- isotopes of Lithium

PELVEL: The list of NPEL pellet velocities.

PELRAD: The list of NPEL pellet radii.

Multi-Species Pellets

It is also possible to set multi-species pellets. To assign a 2nd species to the J'th pellet in a run, set the following for each pellet:

FPEL2: The fraction of the pellet which is the 2nd species.

APEL2: The atomic weight of 2nd species. The same constraints which apply to APEL apply to APEL2 also. APEL and APEL2 must be distinct for each pellet.

Extrapolation Controls

The extrapolation window around the pellet times is controlled by the following switches. Note that for each value of J that TPELDA(1,J) and TPELDA(2,J) must surround a pellet event time.

TPELDA(1,J): This is the last valid time to use Ufile data prior to the injection of the J'th pellet. The data will be extrapolated forwards to the event time from this point.

TPELDA(2,J): This is the first valid time to use Ufile data after the injection of the J'th pellet. The data will be extrapolated backwards to the event time from this point.

The method of extrapolation is controlled by the following switches. The first is a global switch which will apply to all diagnostics whereas the second applies to the specific diagnostic with trigraph xxx. For these switches a value of 0.0 corresponds to flat (constant) extrapolation into the event window while a value of 1.0 corresponds to linear extrapolation. A value between 0.0 and 1.0 gives a weighted average of the two methods.

XXTPEL: The global control for all diagnostics.

XTPxxx: The control for the diagnostic with trigraph xxx.

Pellet Gun Geometry Controls

PLRSTA=700.0 : Initial R value of pellet.

PLYSTA=0.0 : Initial Z value of pellet.

PLTHEA=0.0 : Poloidal tilt angle of pellet gun (Degrees).

PLPHIA=0.0 : Toroidal tilt angle of pellet gun (Degrees).

Sawteeth

Unlike for the pellets, the window around a sawtooth event where Ufile data is not used is defined by a single number: DTSAWD. Data within +/-DTSAWD of a sawtooth event will not be used and the data outside this window will be extrapolated inwards to the sawtooth time. The sawteeth times are passed to TRANSP via a 1D Ufile input using trigraph SAW. Such a Ufile is created by searching for discontinuities in a suitable 1D time trace, for instance one of the core KK3 (electron temperature) channels. This is described in the how to section.

The method of extrapolation for sawteeth is controlled by the following switches. The function of these switches is completely analagous to the corresponding switches XXTPEL and XTPxxx for pellets described above.

XXTSAW: The global control for all diagnostics.

XTSxxx: The control for the diagnostic with trigraph xxx.

Sawtooth Modelling

In order to exploit the sawtooth modelling functionality a Ufile containing sawtooth times must be provided as described in the above section. Utilising this allows comparisons of energy transfers calculated using measured data and predictions based on various sawtooth models. To activate the sawtooth model set:

NLSAW = TRUE

It is then possible to configure which species are affected by the sawteeth using the following switches. The default for each of these is TRUE indicating that they will be affected.

NLSAWE : Set to FALSE to turn off the sawtooth model for electrons.

NLSAWI : Set to FALSE to turn off the sawtooth model for ions.

NLSAWB : Set to FALSE to turn off the sawtooth model for beam ions.

NLSAWF : Set to FALSE to turn off the sawtooth model for fusion product ions.

NLSAWIC : Set to FALSE to turn off the sawtooth model for ICRF minority fast ions.

Which model is used to determine the effect of the sawteeth is governed by the switch NMIX_KDSAW. The options available for this switch are:

NMIX_KDSAW = 1 : The standard Kadomtsev Model

NMIX_KDSAW = 2 : The Kadomtsev Model but with full particle mixing instead of Helical flux matching. The predicted densities are fully flattened.

NMIX_KDSAW = 3 : The Porcelli Model with 2 mixing regions, one for the island around the q=1 surface and one for the core region inside the island. The island width is set by the parameter FPORCELLI.

NMIX_KDSAW = 4 : The Porcelli Model with a single mixing region including both the q=1 island and the core region inside the island.

The following variables further configure the behaviour of the sawtooth model:

FPORCELLI : The width of the magnetic island around the q=1 surface in the Porcelli model is set using this parameter. The island extends inwards from the q=1 surface to χ=(1-FPORCELLI) × χ(q=1) where χ= $\sqrt{Ψ_{Tor} (Normalised)}$ . Consequently for a choice FPORCELLI=1.0 the magnetic island will extent to the magnetic axis as for the Kadomtsev model. Note that the island extends the same distance in χ outside the q=1 surface.

XSWID1 : This switch controls the prediction of the ion temperature after the sawtooth crash. When set to 0.0 (Default) the model is used to calculate the post sawtooth ion energy density profile. The ion temperature is then calculated using measured ion density data. This conserves total ion energy. Conversely setting this switch to 1.0 uses the sawtooth model to calculate the new ion temperature profile directly and uses the measured data for the density. This will not strictly conserve energy. Intermediate values giving a weighted average between the two extremes are allowed.

XSWID2 : The switch controls the prediction of the plasma current. When set to 0.0 (Default) the current profile predicted by the sawtooth model is used after the sawtooth crash. For instance the Kadomtsev model yields q=1 on axis and q>1 off axis post-crash. When set to 1.0 no current mixing occurs, the current and q profile are unchanged by the sawtooth crash. Again intermediate values give weighted averages of the two extreme cases.

XSWIDQ : This sets a minimum χ width on current sheets produced by the mixing model. This is to prevent the equlibrium solver from failing when presented with a true current sheet as this causes discontinuities in the q profile. The range is restricted to 0.0<XSWIDQ<0.10 (Default=0.05).