ITER Plasma Density, the Greenwald Limit and the Aldred Density Ceiling

This paper computes the characteristic densities of the ITER tokamak plasma from published operating parameters and compares them, quantity by quantity, with the Aldred density ceiling of 9.72e+57 kilograms per cubic metre, the neutron-branch bound at prescription coefficient one eighth. The headline comparison gives a margin of 64.4 orders of magnitude between the operating point and the ceiling: the ITER core mass density lies 64.4 orders of magnitude below the ceiling, while the empirical Greenwald density sits only a factor of 1.19 above the operating point; the density limit that ITER must respect is an edge stability limit, and the ceiling is remote by an enormous factor. Every number is obtained from the deposited calculation, which uses only published device parameters, internationally tabulated constants, and algebra stated in full. The result is negative in the useful sense: it shows that the ceiling imposes no constraint on the system as designed or operated, identifies the empirical and engineering limits that act instead, and states precisely what change in operating parameters would be required before the ceiling could matter. The study is a computation from stated assumptions; nothing in it is a measurement.