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The surface topography of YBa2Cu3O7 thin films prepared by pulsed laser deposition is studied by atomic force microscopy and scanning tunneling microscopy. The possible contributions from observed structural features to the critical current density Jc are discussed. It is shown that the contribution of the screw dislocations associated with some structures can be either repulsive or attractive, depending on the dominant pinning mechanism. At low magnetic fields (to about 0.25 kOe) these dislocations can account for the observed critical current density values (Jc≳1011 A/m2) while for larger fields the higher‐density steplike growth structures can account for significant values of Jc. It is shown that the pinning strength associated with pinning at steps varies inversely with thickness.

High-intensity fast white neutron pulses are needed for pulsed fast neutron transmission spectroscopy (PFNTS). A compact tritium–tritium fusion reaction neutron generator with an integrated ion beam chopping system has been designed, simulated, and tested for PFNTS. The design consists of a toroidal plasma chamber with 20 extraction slits, concentric cylindrical electrodes, chopper plates, and a central titanium-coated beam target. The total ion beam current is 1A. The beam chopping is done at 30keV energy with a parallel-plate deflector integrated with an Einzel lens. Beam pulses with 5ns width can be achieved with a 15ns rise/fall time ±1500V sweep on the chopper plates. The neutrons are produced at 120keV energy. A three-dimensional simulation code based on Vlasov iteration was developed for simulating the ion optics of this system. The results with this code were found to be consistent with other simulation codes. So far we have measured 50ns ion beam pulses from the system.

Fast deuterium (D+) and tritium (T+) ion beam pulses are needed in some neutron-based imaging systems. A compact, integrated fast ion beam extraction and chopping system has been developed and tested at the Lawrence Berkeley National Laboratory for these applications, and beam pulses with 15ns full width at half maximum have been achieved. Computer simulations together with experimental tests indicate that even faster pulses are achievable by shortening the chopper voltage rise time. This chopper arrangement will be implemented in a coaxial neutron generator, in which a small point-like neutron source is created by multiple 120keV D+ ion beams hitting a titanium target at the center of the source.

A single-photon counting system has been developed for measuring gas laser parameters. A linear accelerator provides nanosecond-wide pulses of heavy charged particles which are injected into a specially designed cell. The charged particles excite gas mixtures, and the temporal response of the emitted radiation is observed as a function of wavelength. The resulting data is analyzed to obtain pertinent parameters such as excited-state lifetimes, reaction rate constants, and quenching rate constants. At the present time nuclear pumper laser candidate gases are being examined.

Relative excitation efficiencies are reported for the fluorescence at 173 nm in liquid xenon excited by 0.5 MeV electrons (β particle), 6 MeV alpha particles (α particle), and 90 MeV fission fragments (ff). Efficiencies at 173 nm are also reported for alpha particle and fission fragment excitation of high pressure xenon. Results are presented in the form of ratios which compare the fluorescent output per unit energy for excitation by the different particles. The β/α and α/ff ratios for liquid xenon are 1.25±0.5 and 3.5±1.2, respectively. For xenon at 2000, 3000, and 4000 Torr, the α/ff ratios are 0.60±0.25, 0.61±0.23, and 0.63±0.24, respectively.