A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs.

The Accelerator Test Facility (ATF) at Brookhaven National Laboratory is a linac-laser complex for research into laser acceleration and for the generation of coherent radiation from electron beams. In order to achieve the design 50 MeV output emittance (..gamma..sigma/sub x/sigma/sub x/') of less than 3 /times/ 10/sup /minus/5/ m rad a high brightness electron gun is required. This paper describes computations and measurements made on a full scale brass model of a 1-1/2 cell, ..pi..-mode, resonant, disc loaded, radiofrequency gun structure which has been designed for this purpose. 7 refs., 9 figs., 6 tabs.

We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging form 280 to 560 GHz. 7 refs., 1 tab.

In the critical current measurement of some high current NbTi cables, the samples have to be ''trained'' by repeated quenching in order to obtain a usable voltage-current curve for I/sub c/ determination. This training behavior is most pronounced when the applied field is perpendicular to the wide face of the conductor and is strongly dependent on the copper-to-superconductor ratio and the clamping pressure. Data are given for SSC prototype cables as well as for HERA production conductors. Although a quantitative understanding of the experimental data is still lacking, some speculations regarding stability are presented. 8 refs., 7 figs.

The time variation in the magnetic field of a model Tevatron dipole magnet at constant excitation current has been studied. Variations in symmetry allowed harmonic components over long time ranges show a log t behavior indicative of ''flux creep.'' Both short time range and long time range behavior depend in a detailed way on the excitation history. Similar effects are seen in the remnant fields present in full-scale Tevatron dipoles following current ramping. Both magnitudes and time dependences are observed to depend on details for the ramps, such as ramp rate, flattop duration, and number of ramps. In a few magnets, variations are also seen in symmetry unallowed harmonics. 9 refs., 10 figs.

In accoradnce with the ASME Code for Pressure Piping, B31 version of Chemical Plant and Petroleum Refinery Piping, ANSI/ASME B31.3-1984 Edition, the maximum allowable stress for 304 stainless steel piping is 25,500 psi. This 'Allowable Displacement Stress Range' value was calculated using equation (1a) found on page 16 of the above mentioned reference. Each of the lines that comprise the End Cap Calorimeter (BC) piping were modeled on ANSYS and the appropriate constraints were applied. This was done using the Piping Stress Analysis Module of ANSYS. The bending stresses and displacements due to the thermal contraction that occurs in cooling the piping from 300 K to 77 K were calculated by ANSYS. The seven lines involved and their maximum bending stresses are as follows: (1) Rupture Disc - Maximum bending stress is 8335 psi; (2) Argon Relief - Maximum bending stress is 12,619 psi; (3) Gaseous Argon Supply - Maximum bending stress is 5399 psi; (4) Liquid Nitrogen Cooldown Supply - Maximum bending stress is 7049 psi; (5) Liquid Nitrogen Operating Supply - Maximum bending stress is 5774 psi; (6) Nitrogen Exhaust - Maximum bending stress is 1826 psi; and (7) Argon/Nitrogen Vent - Maximum bending stress is 48,364 psi. …

We have measured the slow magnetization decay of a short sample (2.3 cm) of Tevatron cable in fields up to 0.3 T. The special susceptometer in development for these measurements is based on a commercial SQUID and is described in detail. The observed decay is logarithmic in time as expected from flux creep in the NbTi filaments. A strong correlation was found between the decay and the magnetization status of the sample. It is too early yet to present a quantitative correlation between what we observed and the decay observed in the sextupole component of Tevatron dipoles. The detailed understanding of this phenomenon may be instrumental in guiding the search for efficient superconducting synchrotron operational procedures. 3 refs., 5 figs.

Four full-scale SSC R and D dipole magnets, incorporating successive mechanical design improvements, have been quench tested. Three of these magnets are heavily instrumented with sensors to measure the mechanical behavior of the magnets and verify the performance of the mechanical improvements and with multiple voltage taps to locate the origin of quenches. The last two magnets of this series reach the SSC design operating field of 6.6 T in two or fewer quenches. Load cells and motion sensors show that in these two magnets the azimuthal clamping stress is higher at zero current and drops more slowly with excitation than in previous long magnets and that the axial motion of the coil upon excitation has been greatly reduced. Quenches are found to originate preferentially in several locations, suggesting other design improvements. 13 refs., 5 figs.