Plasma Profile Plots

Profiles show how temperature, density, and other quantities vary across the plasma radius, the workhorse plot of confinement physics.

The radial profile

A profile plots a plasma quantity against a radial coordinate, usually a normalized flux-surface label from 0 at the axis to 1 at the boundary. Temperature, density, pressure, current, and the safety factor are the common profiles. Their shapes carry the physics: peaking, gradients, and pedestal features drive confinement and stability.

Choosing the abscissa

Kronos motion — density profile

Normalized flux label makes profiles comparable across shapes and sizes.
Major radius shows real spatial position but mixes in geometry.
Always state which coordinate is used; the two look similar and mean different things.

Reading gradients

Much of the interesting physics lives in slopes, not values. Steep edge gradients, a pedestal, or a flattened core all indicate transport behavior. Plotting the gradient alongside the profile, or using a scale that reveals it, prevents the eye from missing the feature that matters.

Overlaying model and data

Profiles are where simulation meets measurement. Plotting a modeled profile against diagnostic points, with error bars on the data and a band on the model, shows agreement honestly. Never draw a smooth model curve through scattered points without showing the scatter.

python

import numpy as np
rho = np.linspace(0,1,100)
T = T0*(1 - rho**2)**alpha   # a simple peaked profile
# plot T vs rho; annotate axis (rho) and units (keV)

Kronos use

Profiles for the breeder plasma are simulation output at the frozen design point; they are shown with clearly labeled units and never presented as measured data before first hardware.