To fission more of a given amount of fissile material, a small amount of material that can undergo fusion, deuterium and tritium (D-T) gas, can be placed inside the core of a fission device. Here, just as the fission chain reaction gets underway, the D-T gas undergoes fusion, releasing an intense burst of high-energy neutrons (along with a small amount of fusion energy as well) that fissions the surrounding material more completely.
Substantial theoretical work on the booster was done in 1948, and on the basis of this work it was proposed in the Fall of 1948 to include the booster in the next weapons test. In the first part of 1949, a more thorough theoretical investigation of the booster was carried out.
Possibilities of this general type were recognized at least as early as November 1945, when they were included in a patent application filed at Los Alamos. The designation "Booster" only became general after its use by Teller in September 1947. In the summer of 1948 a detailed study was begun to determine the necessary characteristics of a device in which this interaction between fission and thermonuclear processes might be realized. A full-scale test of the model which would ultimately result from this program of study was put on the list of shots to be made in the next overseas test operation which was then planned to be held in 1951.
These studies, which were in general directed by Teller, were earned out in their first stages by Rosenbluth and Reitz. By the fall of 1948, a number of points had been checked and the more promising lines of approach had been identified. Study of the Booster was continued through 1949 and, starting early in the summer, was greatly intensified. Several unanticipated problems were turned up and overcome.
A large number of people necessarily became involved in obtaining the information required for the many different aspects of the study of the Booster: Landshoff, because of his experience with Baby Hippo; Evans, on the ignition and progress of thermonuclear burning; Reitz and others, on equation of state problems; the members of the hydrodynamics calculation group, under Hammer; the various persons who had experience with the neutronics calculations required for standard fission bombs; Bethe, Longmire, and others, to consider possible extraneous processes and to make estimates of their effects; and many others outside the Theoretical Division, to measure cross sections and other quantities required for the calculations, and to solve the mechamical problems involved.
Almost all of these aspects of the problem had been taken up before the time of the first Russian test in September 1949. By about the end of January 1850, this work was far enough advanced to allow the choice of a model for which each step was to be calculated. This chain of calculations was expected to be completed sometime during the summer of 1950; and at that time, provided no major surprises were encountered, it was hoped to freeze the fine details of the design.
In the event, things proceeded very much in this fashion except that it took a little longer than expected. The last details of the design for the experiment were frozen late in October 1950.
Five test explosions at Eniwetok in Greenhouse series first demonstrated boosting techniques. These included "Cylinder=George" test, which yielded 225 KT on 09 May 1951, and the 45.5 KT "Item" test. These confirm yield boosting via D+T reaction.
This approach, called boosting, is used in most modem nuclear weapons to maintain their yields while greatly decreasing their overall size and weight.
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