[en] We calculated the cool down time for the outer coil of the 60 Tesla 100 ms research magnet under design at the US High Magnetic Field Laboratory. A drawing of the magnet system is shown in Fig. 1. This is a preliminary design and will undoubtedly differ from the final design. We chose convenient conductor cross sections for the solenoid and assumed a packing factor of 0.75. The 25% conductor void was assumed to be filled with insulation having the thermal properties of an epoxy glass resin mixture. Our approach was to use a 2D axisymmetric finite element calculation to accurately model a radial slice from the midplane of the solenoid. This model consisting of alternating layers of insulation and conductor is shown in Fig. 2. We compared the results from this model to those of a one material model with smeared thermal properties. The smeared properties were adjusted so that comparable thermal diffusion times were obtained by both methods. Using the smeared properties we were able to model a 2D cross section of the solenoid with all the boundaries specified while avoiding the necessity of the complex meshing of conductors and insulators. Long simulation run times were thus avoided, and we were able to quickly modify the geometry to test cooling methods

No abstract available

[en] Results have been obtained from initial experiments in which a small plasma focus was used to drive DT microballoons. The DT microballoons were 1 mm in diameter and contained 50 atmospheres of DT gas in a 50% mixture. The plasma focus driver achieves a maximum current of ∼ 1 MA from its 20-kV, 72-kJ capacitor bank. The plasma sheath was formed from deuterium, hydrogen, and helium for these tests. After several conditioning shots using the gas for the experiment, the microballoons were inserted into the focus region through an air lock in the device's anode, to avoid any electrical gradient between the positive electrode and the target. Neutron yields of 10⁹ to 10¹⁰ 14.1-MeV neutrons have been measured from the combination of a deuterium plasma sheath and a DT target. However, the authors have been unable to detect a significant DT-neutron yield with hydrogen and helium plasma sheaths. Therefore, one is led to conclude that the 14.1-MeV neutron yields that have been observed are due to a beam-target interaction between accelerated deuterons from the plasma sheath and the tritium gas in the microballoon. The results of these tests are presented

[en] Magnetic semiconductors offer a unique possibility for strongly tuning the intrinsic alloy disorder potential with applied magnetic field. We report the direct observation of a series of step-like reductions in the magnetic alloy disorder potential in single ZnSe/Zn(Cd,Mn)Se quantum wells between O and 60 Tesla. This disorder, measured through the linewidth of low temperature photoluminescence spectra drops abruptly at -19, 36, and 53 Tesla, in concert with observed magnetization steps. Conventional models of alloy disorder (developed for nonmagnetic semiconductors) reproduce the general shape of the data, but markedly underestimate the size of the linewidth reduction

[en] The magnetophotoluminescence (MPL) behavior of a GaAs/Al_0.3Ga_0.7As single heterojunction has been investigated to 60T. We observed negatively charged singlet and triplet exciton states that are formed at high magnetic fields beyond the ν=l quantum Hall state. The variation of the charged exciton binding energies are in good agreement with theoretical predictions. The MPL transition intensities for these states showed intensity variations (maxima and minima) at the ν=l/3 and 1/5 fractional quantum Hall (FQH) state as a consequence of a large reduction of electron-hole screening at these filling factors

[en] We present here the results of polarized magneto-photoluminescence measurements on a high mobility single-heterojunction. The presence of a doublet structure over a large magnetic field range (2>v>l/6) is interpreted as possible evidence for the existence of a magneto-roton minima of the charged density waves. This is understood as an indication of strong electronic correlation even in the case of the IQHE limit

[en] Results have been obtained from initial experiments in which a small plasma focus was used to drive DT microballoons. The DT microballoons were 1 mm in diameter and contained 75 atmospheres of DT gas in 50% mixture. The plasma focus driver achieves a maximum current of --1 MA from its 20-kV, 72-kJ capacitor bank. The plasma sheath was formed from deuterium, helium, and argon for these tests. After several conditioning shots using the gas for the experiment, the microballoons were inserted into the focus region through an air lock in the device's anode, to avoid any electrical gradient between the positive electrode and the target. The results of these tests are presented

[en] We discuss basic Relativistic Klystron Amplifier physics. We show that in the intense space-charge regime the maximum power extraction does not coincide with the maximum harmonic bunching. In addition, we show that as the beam is bunched, the additional power stored in the Coulomb fields does not add significantly to the overall power extraction. Because of these effects, the power extraction at 1.3 GHz for a 500 kV, 5 kA beam with reasonable beam-to-wall spacing is limited to around 35%. 3 refs., 17 figs

No abstract available

[en] Bistatic HF Doppler measurements of the ionospheric disturbance arising from a large ground-level chemical explosion have revealed a peculiar HF return which begins at large positive Doppler (greater than +5 Hz) and linearly evolves to large negative Doppler (less than -5 Hz). Various pieces of evidence in the data suggest that an HF wave which is diffracted from the intersection of the acoustic shock and an extensive plane of sporadic E ionization at 110 km was observed. From these measurements the horizontal trace velocity of the locus of intersection is estimated. 16 references