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The NBS-LASL racetrack microtron (RTM) is a joint research project of the National Bureau of Standards and the Los Alamos Scientific Laboratory. The project goals are to determine the feasibility of, and develop the necessary technology for building high-energy, high-current, continuous-beam (cw) electron accelerators using beam recirculation and room-temperature rf accelerating structures. To achieve these goals, a demonstration accelerator will be designed, constructed, and tested. Parameters of the demonstration RTM are: injection energy -5 MeV; energy gain per pass -12 MeV; number of passes -15; final beam energy -185 MeV; maximum current 550 pA. One 450 kW cw klystron operating at 2380 MHz will supply rf power to both the injector linac and the main accelerating section of the RTM. The disk and washer standing wave rf structure being developed at LASL will be used. SUPERFISH calculations indicate that an effective shunt impedance (ZT2) of about 100 MQ/m can be obtained. Thus, rf power dissipation of 25 kW/m results in an energy gain of more than 1.5 MeV/m. Accelerators of this type should be attractive for many applications. At beam energies above about 50 MeV, an RTM should be considerably cheaper to build and operate than a conventional pulsed rf linac of the same maximum energy and time-average beam power. In addition, the RTM provides superior beam quality and a continuous beam which is essential for nuclear physics experiments requiring time-coincidence measurements between emitted particles.

Evidence is presented from the reaction rotational band based on the 1.256-MeV 0 + 1.417 and 1.819 MeV.The low-lying states of nuclei around i V = 88 undergo a transition in character from harmonic vibrational (N88). This can be interpreted as indicating a shape change from spherical to deformed. However, these nuclei, especially those close to N = 88, are quite soft to shape variation and probably have zeropoint vibrations whose amplitude is comparable with their average deformation. 1 In the following we will refer to "spherical" and "deformed" states, realizing that this describes only in some average way the nuclear shape. 150 Sm ( AT = 88) and 152 Sm (tf = 90) are spherical and deformed, respectively, in their ground states, but have excited 0 + states which are believed to have shapes quite unlike the ground states. The 1.091-MeV 0 + state of 152 Sm is strongly populated by the (t, p) reaction from the spherical ground state of 150 Sm, 2 * 3 in contrast to the usual weak population of excited 0 + states by the (t,p) and (/>, t) reactions. Hinds et ah 2 interpret this as indicating a spherical character for the state. Further support for this picture comes from a recent (p, t) experiment 4 in which this state is not seen in pickup from deformed 154 Sm.Likewise, the unusual strength with which the (p,t) reaction connects the deformed ground state of 152 Sm with the 1.256-MeV 0* state of 150 Sm 5 indicates that the latter is a deformed state of a nucleus whose ground state is spherical. If the 1.256-MeV state is indeed deformed, it must serve as the basis for a rotational band. The resolution of the earlier (p,t) experiment left unanswered the question of whether such a rotational band exists.We are currently studying the (p> t) reaction at 19 MeV for a range of rare-earth nuclei. Targets of 152 Sm on C backing have been bombarded with 19-MeV protons from the John H. Williams Laboratory MP tandem. The resultant tritons were analyzed with a split-pole magnetic spectrometer and were recorded on nuclear emulsion. The overall energy resolution was approximately 10 keV. The spectrum of tritons recorded at 6 = 25° is displayed in Fig. 1. Table I gives the excitation energies, angular momenta, and 152 Sm(£,£) 150 Sm for the existence of an excited state of 150 Sm, with 2 + and 4 + members at relative cross sections for the states observed in 150 Sm.The 1.256-MeV 0* state is strongly excited, as in the earlier experiment, 5 and candidates for the 2 + and 4* members of its rotational band appear at 1.417 and 1.819 MeV, respectively. The 1.417-MeV state has been assigned J v =2 + by Lure, Peker, and Prokofev 6 and by Smither and Buss. 7 Lure, Peker, and Prokofev suggested that the state is a rotation of the 1.256-MeV 0 + state. The 1.819-MeV state has recently been assigned J* = 4* by Smither and Buss 7 from resonance capture in the reaction 149 Sm(«, y) 150 Sm. Thus, the angular momenta of these states are proper for a K = 0 rotational band. Angular distributions of 152 Sm(p,t) 150 Sm with L =...