me demand for information arose before Ranger. The very great and sudden improvementsin the national stockpile capability resulting immediately after Sandstone and after Ranger are proofs, not only of the value of full-scale testing, but also of the fact that testing activity had beenat too low a level compared with the other activities. Other fields were sufficiently far ahead so that even a little information from tests improved the over-all situation enormously, One of the major activities should never again be allowed to fall so far behind progress in all other major lines for, if so, these activities will soon reach the point of diminishing returns. LASL does not yet feel that the rate of testing is as rapid as the generation of new ideas would warrant. A new factor has recently entered into the general problem of determining the amount of full-scale testing so as to match appropriately progress in other facets of development. In almost any fission weapon configuration, a combination of results from basic experimental physics, theoretical calculations, and component experiments—all of which can be performed at Los Alamos——can give reliable estimates of all pertinent physical conditions at the beginning of the explosion process, This is not true of devices dependent upon newer techniques for assembly and compression. Not only are calculations much moredifficult and uncertain for the assembly phases of these newer devices, but basic data are often less reliable (if known at all) and, still worse, simple experimental checks of predicted behavior weed during assembly cannot be made without a nuclear detonation. Thus, where full-scale nuclear detonations for fission weapon development have been made with the primary objec- tive of obtaining information about the explosive and disassembly pi.ases of the process, similar tests are now required for thermonuclear devices to obtain information upon both the assembly and the disassembly phases. The uncertainty of these two phases of func- tion of a proposed type of device can easily lead to more than twice as much testing as might be required if only one phase were relatively uncertain. Another factor influencing choice of the optimum amount of testing of thermonuclear, as compared with pure fission, devices involves the great difficulty of measuring the desired quantities affecting the newer techniques during their progress. This meansthat, in the new field, test experimentation has become much more complicated and costly in manpower and dollars, This factor tends to hold down the number of such tests because the diversion of effort required for a high rate of field testing would handicap other necessary activities to the point of impeding over-all progress. Nevertheless, it is clear that rela- tively more tests are needed for thermonuclear weapon development than for fission weapon development. The LASL Organization The objective of the LASL effort is to obtain knowledge in several areas as to utilization of nuclear energy for explosive purposes: The area of nuclear characteristics, especially with respect to neutrons, of all materials which are employed; the area of phys- ical, chemical, and metallurgical characteristics of these materials; the area of mechanics and dynamics of methods of initiating the nuclear energy release; and the area of the behavior of supercritical systems in which the energy generation per unit volume is very large. Ina general way each area corresponds to an organizational division. There have been no major changes in the internal structure of LASL during the three years. The or- ganization includes the following: . LG Theoretical (T) Division -- Is involved in all areas, especially the behavior of super- critical systems, which is understandably less amenabie to experimental investigation than the others. - eee yr 8