On the Core Deuterium-Tritium Fuel Ratio and Temperature Measurements in DEMO

TL;DR

This paper proposes a novel gamma-ray based diagnostic technique for measuring core deuterium-tritium fuel ratio and temperature in DEMO, a future fusion reactor, which is robust, efficient, and suitable for high-radiation environments.

Contribution

A new gamma-ray diagnostic method for core fuel ratio and temperature measurement in DEMO, compatible with limited access and high neutron flux conditions.

Findings

The technique uses nuclear reaction rate comparisons for diagnostics.

It is robust and does not require direct plasma access.

Feasibility discussed for JET and ITER experiments.

Abstract

Comparing with ITER, the experimental fusion machine under constraction, the next step test fusion power plant, DEMO will be characterized by very long pulse/steady-state operation and much higher plasma volume and fusion power. The substantially increased level of neutron and gamma fluxes will require reducing the physical access to the plant. It means some conventional diagnostics for the fusion plasma control will be not suitable in DEMO. Development of diagnostics along with the machine design is a primary task for the test plant. The deuterium- tritium fuel ratio and temperature are among important parameters, which should be under control. In this letter a novel technique for the core fuel ratio and temperature diagnostics is proposed. It is based on measurements and comparison of the rates T(p,{\gamma})4He and D(T,{\gamma})5He nuclear reactions that take place in the hot deuterium-tritium plasma. Based on detection of high energy gamma-rays, this diagnostic is robust, efficient and does not require direct access to the plasma. It could be included in the loop of the burning plasma control system. A feasibility of the diagnostic in experiments on JET and ITER is also discussed.