[en] Coherent transient phenomena in superconducting tunnel junctions are investigated by means of a Gorkov-Nambu, Green's-function formulation, but without making the usual factorization. In this way we are led to and justify a pseudospin-angular-momentum formulation of junction dynamics. We find that for problems involving pair-current flow between weakly coupled superconductors the system can be conveniently represented by its position on a Bloch sphere in our pseudospin space. The magnitude of the Bloch vector is set by the total number of interacting Cooper pairs whereas its orientation is specified by two angles, theta and phi. The angle phi is the usual Josephson-pair phase, but the new angle theta enters our calculations for transient situations. A comparison is made between the present angular-momentum formulation and the phenomenological number--phase-angle theory

[en] Differential cross sections for evaporation residue formation following complete fusion of ⁶⁴Ni and ⁷⁴Ge with 171 to 215 MeV ⁵⁸Ni and ⁶⁴Ni ions were measured with high precision using a velocity selector together with a counter telescope. The resulting excitation functions for complete fusion ranged in magnitude from 10 μb to 300 mb. The excitation functions exhibited a strong response, at subbarrier energies, to changes in the underlying nuclear structure. We interpreted these variations as evidence that the fusion proceeds through dynamic single-particle/softness-related processes. A phenomenological analysis was performed. In the analysis, we employed the WKB method, constructed a simple interaction potential and introduced a radially-dependent effective mass. The use of the variable effective mass led to a meaningful description of our above-barrier data and to improvements towards describing our subbarrier data

[en] Differential cross sections for evaporation residue formation following the complete fusion of ⁵⁸Ni with 187.6 to 220 MeV ⁵⁸Ni ions were measured with high precision using a velocity selector together with a counter telescope. The resulting cross sections for complete fusion ranged in magnitude from 50 μb at 93.3 MeV to 230 mb at 108.9 MeV (c.m.). The cross sections for complete fusion at sub-barrier energies were shown to be far greater than those predicted by standard barrier penetration models

[en] Near-barrier excitation functions for 2n, 3n, 4n, 5n, 2n1p, 3n1p, and 4n1p evaporation from ²⁰⁴Rn following the fusion of ³⁵Cl+ ¹⁶⁹Tm, ⁴⁸Ti+ ¹⁵⁶Gd, and ⁶⁵Cu+ ¹³⁹La are compared between reactions and with statistical decay codes. First and second gamma multiplicity moments were obtained for all three systems at 50 MeV excitation energy. General agreement with statistical decay code predictions is found in all cases

[en] Excitation functions for complete fusion of ⁵⁸Ni+⁵⁸Ni, ⁵⁸Ni+⁶⁴Ni, and ⁶⁴+⁶⁴Ni have been determined over a range of energies from just above to well below the fusion barrier. The response of these excitation functions to the addition of valence neutrons is found to be surprisingly complex. We suggest that at least part of the observed variations may be due to dynamic, single-particle effects

[en] The authors discuss two studies of cyclotron autoresonance maser (CARM) amplifiers underway at M.I.T. They differ both in frequency and in the technologies employed. The 35GHz amplifier uses a 1.5MeV,260A,30ns electron beam from a field emission (explosive) cathode energized by a Marx type, Physics International Pulserad accelerator. The entire system is immersed in a uniform, pulsed magnetic field 7kG. Measurements give a small signal gain of 90dB/m, a saturated power output of 10MW and an electronic efficiency of 3%. The 140GH_z amplifier under development will employ a 450-700kV, 30A, 1μs electron beam from a Pierce-type gun driven by a high-voltage, long-pulse modulator. The magnetic field (--25kG) in the CARM interaction region will be produced by a superconducting magnet. Theoretical investigations of CARM efficiency, efficiency enhancement by magnetic field tapering, and amplifier stability are also being carried out