Wall heat loads¶

SIMPLE records where and when each lost marker leaves the plasma. This page sets up the two heat-load estimates: on the last closed flux surface (LCFS) from a standard run, and on a triangulated first wall from an STL file. Method: Heat-load estimators. Worked example: Tutorial 2: Wall heat loads.

Losses on the last closed flux surface¶

A standard run stops a marker when its guiding centre crosses the LCFS (exit code 1). Its final state zend and xend_cart in results.nc (output_results_netcdf = .true.) is the crossing point. Binning these points in \((\vartheta, \varphi)\), weighting each by \((v/v_0)^2\) and dividing by the bin area from a chartmap gives the LCFS heat flux; use docs/tutorials/scripts/lcfs_heat_flux.py. The estimate needs no wall geometry and ignores plasma–wall distance, gyroradius and shadowing.

Limitation: pysimple.engineering.WallHeatMap.from_netcdf reports no losses for a standard run (it selects class_lost, set only by classification runs) and reads zend with transposed axes; use the tutorial script.

Losses on an STL first wall¶

SIMPLE follows the guiding centres beyond the LCFS and intersects each accepted step with the wall surface.

Setting	Requirement
build	`-DSIMPLE_ENABLE_CGAL=ON` (Installation)
`coord_input`	chartmap reaching beyond the LCFS, with attribute `rho_lcfs` < 1 (Field sources and coordinates)
`field_input`	field valid between LCFS and wall, normally the coil field
`isw_field_type`	`3` or `4` (canonical on the chartmap), or `5` with `integmode = 0`
`wall_input`	STL file, closed surface around the LCFS, facet order as in the CAD export
`wall_units`	`'m'` (default) or `'mm'`, the STL length unit
`output_results_netcdf`	`.true.`, to write the hits

The wall is queried only after an accepted step has ended outside the LCFS (\(\rho > \rho_\text{lcfs}\)), because a chord between two points inside the LCFS can cut a non-convex wall. A hit ends the marker with exit code 2 and writes wall_hit = 1, wall_hit_cart, wall_hit_normal_cart, wall_hit_angle_rad (0 is normal incidence) and wall_hit_triangle (zero-based facet index in STL file order, -1 without hit). A marker that reaches the outer chartmap boundary without a hit ends according to chart_boundary_kind (Wall intersection). Positions are guiding-centre positions; full orbits (orbit_model = 7) do not support walls.

With collisions (swcoll = .true. and a &profiles namelist, Running SIMPLE), hits occur at reduced energy. Choose trace_time relative to the slowing-down time of the profiles: much shorter measures prompt losses, comparable resolves losses at reduced energy. The hit keeps the momentum of the kicks before the intersecting step, so hit energies have the time resolution of the microstep.

Heat load per triangle¶

pysimple.wall_heat_load.TriangleHeatLoad deposits each hit on its facet (formulas and metric definitions in Heat-load estimators). It needs the original STL with unchanged facet order; the loader checks file name and facet count.

from pysimple.wall_heat_load import TriangleHeatLoad

load = TriangleHeatLoad.from_netcdf("results.nc", "wall.stl",
                                    total_alpha_power_MW=600.0)
print(load.summary(threshold_W_m2=1e5))  # peak, p95, wetted area, ...
load.to_vtk("wall_heat.vtk")     # ParaView, cell data per facet
load.to_netcdf("wall_heat.nc")   # arrays plus vertices(triangle, vertex, xyz)
load.to_stl("wall_heat.stl")     # geometry plus wall_heat.stl.nc sidecar

Per facet it provides power_W, power_density_W_m2, power_density_per_MW (W/m² per MW of source alpha power) and hit_count; geometry is in metres. Equal marker weights are power-correct only for fusion-weighted births (startmode = 7, Fusion-weighted alpha births); for other start distributions pass marker_weights (one relative source weight per marker). No smoothing is applied: check hit_count and convergence with marker number.