The Steady State Superconducting Tokamak (SST-1) is currently under design/fabrication at the Institute For Plasma Research (IPR), Bhat, Gandhinagar-382 428, India. This page gives a brief idea about the device, its conceptualization, status and goals. More details will be added in future by hyperlinks.
Plasma is a new state of matter in which most of the atoms are ionized due to some sort of `violence' and breaking away of the originally bound electrons. This state of matter is interesting because of its use in creating fusion reactions in a controlled manner in future. For fusion reactions to take place in an economically viable way for power production, one must confine a hot and dense plasma of the `fuel' gas (say deuterium and tritium which are isotopes of hydrogen) for a sufficiently long time. All these parameters (hotness, density and the time-duration) are usually written as a product (Lawson number) which must exceed a certain threhold value for getting as much fusion energy as one is spending (say in maintaining the heat within the plasma).
A tokamak is a device for confining a hot and dense plasma using magnetic forces. Shaped like a donut or a torus, it can be characterized by a major radius R and a minor radius a. It has evolved over a period of about 40 years and has perfected its performance steadily to rise to a level envied by other alternate confinment schemes. Its evolution profile is dotted with several crucial discoveries, e.g., the fact that the confinement time goes as the square of major radius, and Ip (the current carried by the plasma), the discovery and explanation of density, current and pressure limits, and finally, the fact that when one has steered clear of almost all major instabilities the remaining `noise' which causes a significant heat loss can also be somewhat controlled. (The various improved confinement modes of operation).The SST-1 tokamak belongs to a new generation of tokamaks which take the above objectives further -- in the direction of steady state operation. Traditionally the tokamaks have operated with a `transformer' action -- with plasma acting as a secondary, thus having the vital `self-generated' magnetic field on top of the `externally-generated' (toroidal and equilibrium) fields. This is a pretty good scheme in which creation, current-drive and heating are neatly integrated and remained a choice of the fusion community for many years untill the stage came to heat the plasma to multi-keV temperatures. Heating was then accomplished separately by Radio Frequency (RF) waves and/or energetic Neutral Beam Injection (NBI). Subsequently, excellent control got established on tokamak plasma performance by controlling the plasma-wall interaction processes at the plasma boundary so the plasma duration was limited primarily by the `transformer pulse length'. However, for relevance to future power reactors it is essential to operate these devices in a steady state mode. The very idea of steady state operation presents a series of physics and technology challenges! For example, the excellent plasma performance which was accomplished earlier, was with the surrounding material wall acting as a good `pump' of particles, a fact which may not be true in steady state. So one has to try and accomplish an equally good performance in presence of a possibly `saturated' wall. Secondly, a host of engineering and technical considerations spring up. The magnets must be superconducting type, otherwise the power dissipation in conventional (resistive) types can reach uneconomical levels. They have to be specially designed to remain superconducting inspite of their proximity to the other `warm' objects (like vacuum vessel etc.). The heat and particle exhaust must be handled in steady state with specialized tiles and active cooling.
The SST-1 tokamak is a step in the above direction. Its parameters are: