sites have been used routinely by LASL since 1943 for tests involving high explosives and for tests involving radioactive materials. As discussed in the previous section, much of the requisite knowledge up to the point of disassembly of implosion-type weapons could be tested at Los Alamos! outlying sites. With the advent of two-stage thermonuclear experimentation, however, Los Alamos! outlying sites could no longerbe used to acquire assembly knowledge; exploration of both the assembly and disassembly phases now require fullscale field tests. A majority of full-scale field tests is for exploration of what takes place during assembly and disassembly and for nuclear components research and development. Some are held, however, to check the functioning of various components or of the full weapon. Tests for these purposes are utilized additionally by other national programs, such as military and civil defense effects programs. On occasion, tests are scheduled almost entirely to meet military requirements, but are then used additionally for developmental research. From the viewpoint of AEC programs, full-scale nuclear field tests are held for the following reasons: To 1. Assure the adequacy of a device or weapon beforeit enters the national stockpile, to provide a firm basis for undertaking the extensive engineering and fabrication effort which must be expended in order to carry a preliminary model to the version satisfactory for stockpile production. 2. Demonstrate the adequacy, ‘or inadequacy and limitations, of current theoretical approaches in order that promising avenues of development may be exploited more fully or given lower priority of attention. 3. Explore phenomena which can vitally affect the efficiency and per- formance of an atomic weapon, but which are not susceptible to prior theoreti- cal analysis of sufficient certainty. 4. Provide a basis for choice among existing theoretical methods of weapon improvement in order to concentrate attention along lines of the great- est practical significance. 5. Determine the validity of entirely new and untried principles proposed for application to the production of explosive atomic energy at improved efficiency. 6. Provide entirely new information pertinent to weapons development arising as a by-product of scientific observation of full-scale detonations. Experience has shown the significant value of such incidental information obtained in addition to specifically planned objectives. 7. Gain time in urgent development programs by the substitution of fullscale tests for a portion of a possible but lengthy calculational and experimental program in the laboratory. ALGa 8. Provide, as a by-product, basic scientific information which becomes a part of the backlog of knowledge more normally obtained in the laboratory. Tests thus contribute to other major phases of weapons development. Another application of this type of information lies in its use in the interpretation from wa