[en] Letter-to-the-editor

[en] Published in summary form only

[en] A semianalytic program has been developed to map the pitch angles of magnetospheric particles onto a detector telescope acceptance cone. The telescope fractional efficiency is defined as the fraction of the pitch angle cone in common with the telescope cone multiplied by the fractional perpendicular component of the exposed detector area, and normalized by 2π. Calculations have been performed as a function of the satellite's location, orbital inclination and the zenith angle of the telescope axis, both in dipole and real geomagnetic field models. At the dipole equator, the peak efficiency occurs at 90⁰ pitch angle. In the real geomagnetic field model, the average value of the pitch angle for maximum efficiency is ≅ 88⁰. The efficiency function depends strongly upon latitude and is independent of longitude in a dipole field, but depends on longitude in the real field model. In either field model, altitude, angle of tilt and orbital inclination have little effect upon efficiency. The efficiency function calculated at the dipole equator can be used at the minimum magnetic field equator with little error, but not for points away from the B_min position. The results are applied to calculate the absolute flux of magnetospheric particles observed near the equator. (orig.)

[en] The gain stability and the temperature effects of three photomultiplier tube bases at high counting rates were tested experimentally. Comparisons of the gain variation with counting rate were made among different supply voltages and between anode and dynode output signals. The factors causing gain variation at high counting rates were discussed. The experiments show that, choosing a transistor emitter follower type, using a lower supply voltage and adopting a dynode output mode are effective measures for improving the gain stability. (orig.)

[en] A study of a veto system efficient on a large surface is reported for those experiments in which rather rare events must be discriminated against the cosmic background. The technique proposed in this paper recognizes the events induced by cosmic rays from the direction of flight (DOF) of the crossing particles. The performance of a setup based on the DOF technique has been experimentally tested; the results are presented and discussed. (orig.)

[en] In order to investigate radiation hardness of the bipolar SST transistors, transistor samples were exposed with fast neutrons from a nuclear reactor. The obtained degradation coefficient, Δ(h_FE^-1), was ≅ 0.001 for 10¹³ neutrons/cm². (orig.)

[en] The horizontal position of the plasma in the HBTX1C reversed field pinch has been controlled to ±1 mm by a feedback circuit. The plasma is moved to the desired position by momentarily closing either one of two semiconductor switches which alter the way in which current is shared by the parallel-connected field windings. Equilibrium control was added without the need for additional power supplies or additional field coils. (orig.)

[en] Employing the crossed-beams technique we have measured absolute cross sections both for electron capture and for ionization in collisions between two Bi⁺ ions at center-of-mass energies ranging from 10 to 55 keV. Based on these data an estimate is given of beam intensity losses due to ion-ion collisions in the storage rings of the HIBALL II scenario. (orig.)

[en] For non-naked highly-charged heavy ions, dielectronic recombination (DR) can be the dominant electron capture process. Depending on the kind of a DR resonance involved, cross sections may reach values up to 10^-18 cm² at the peak maximum. The widths of the DR resonances are typically < or approx.1 eV. Tuning a merged electron beam with an internal temperature typically ∝0.1 eV to the DR resonance, a well defined narrow part can be cut out of the original ''hot'' primary ion beam by this charge-exchange process. The charge-changed new beam is pretty ''cool'' (ΔE/E ≅ 10^-5). A case study for Ge³¹⁺+e=Ge^30+** (2p²¹D₂) is given. Technical applications of DR beam tailoring techniques at heavy-ion storage rings will be discussed. (orig.)

[en] As a continuation of previous work on the analysis and optimization of ICF beam and target configurations, the influence of the energy deposition profile by heavy ions in the different layers of ICF capsules has been analyzed. A general conclusion obtained from the calculations is the confirmation that the hydrodynamic performance of the treated targets strongly depends on the particular ion energy deposition profile obtained along the different material zones. Moreover, the possibility of continuously locating the energy deposition front at the appropriate penetration level can avoid the undesirable fuel preheating resulting from the excessive penetration of energy deposition profiles optimized with regard to the initial target structure (before range shortening). It is worth to point out in this respect that significant reductions on the high gain (≅ 100) threshold beam energies have been estimated under assumption of the appropriate voltage tailoring for the incident ions, and that such tailoring, if technologically feasible, could be a key point for the practical obtainment of these high gains. The series of studies completed in order to optimize the structure of heavy-ion-beam-driven targets has led to the practical treatment of the critical points for the attainment of an optimized compression dynamics and to the joint definition of corresponding multilayered-target designs and energy deposition schemes. As a whole, the results obtained show heavy-ion fusion targets to be certainly promising as valid alternatives for use in ICF systems within the scope imposed by the limitations of the 1D simulation models employed, mainly related to the impossibility of consideration of asymmetry-induced effects. (orig.)