reactions. This was apparently a great success, and in January 1958, they announced the fusion had been achieved in ZETA based on the release of neutrons and measurements of the plasma temperature. Vitaly Shafranov and Stanislav Braginskii examined the news reports and attempted to figure out how it worked. One possibility they considered was the use of weak "frozen in" fields, but rejected this, believing the fields would not last long enough. They then concluded ZETA was essentially identical to the devices they had been studying, with strong external fields. First tokamaks By this time, Soviet researchers had decided to build a larger toroidal machine along the lines suggested by Sakharov. In particular, their design considered one important point found in Kruskal's and Shafranov's works; if the helical path of the particles made them circulate around the plasma's circumference more rapidly than they circulated the long axis of the torus, the kink instability would be strongly suppressed. Today this basic concept is known as the safety factor. The ratio of the number of times the particle orbits the major axis compared to the minor axis is denoted q, and the Kruskal-Shafranov Limit stated that the kink will be suppressed as long as q > 1. This path is controlled by the relative strengths of the external magnets compared to the field created by the internal current. To have q > 1, the external magnets must be much more powerful, or alternatively, the internal current has to be reduced. Following this criterion, design began on a new reactor, T-1, which today is known as the first real tokamak. T-1 used both stronger external magnets and a reduced current compared to stabilized pinch machines like ZETA. The success of the T-1 resulted in its recognition as the first working tokamak. For his work on "powerful impulse discharges in a gas, to obtain unusually high temperatures needed for thermonuclear processes", Yavlinskii was awarded the Lenin Prize and the Stalin Prize in 1958. Yavlinskii was already preparing the design of an even larger model, later built as T-3. With the apparently successful ZETA announcement, Yavlinskii's concept was viewed very favourably. Details of ZETA became public in a series of articles in Nature later in January. To Shafranov's surprise, the system did use the "frozen in" field concept. He remained sceptical, but a team at the Ioffe Institute in St. Petersberg began plans to build