A hybrid beam design for slow positron transport

The authors report on the design of a hybrid transport system for slow positrons based upon the high-intensity magnetically transported positron beam, which existed at the Brookhaven (BNL) high-flux beam reactor (HFBR) in 1986. The resulting modified transport, incorporating an initial electrostatic stage followed by a magnetic stage and completed by brightness enhancement moderation leading to a final electrostatic section, represented the minimum alteration of the existing beam to enable it to be used for crossed-beams differential scattering studies involving a variety of atomic and molecular systems, including atomic hydrogen. A recent proposal for constructing a very high-intensity positron beam at the Paul Scherrer Institute (PSI), based upon magnetic confinement premoderation, has rekindled interest in the conclusions of the study

A polarized atomic hydrogen beam

We describe the design and operating characteristics of a simple polarized atomic hydrogen beam particularly suitable for applications to crossed beams experiments. In addition to experimental measurements, we present the results of detailed computer models, using Monte-Carlo ray tracing techniques, optical analogs, and phase-space methods, that not only provide us with a confirmation of our measurement, but also allow us to characterize the density, polarization, and atomic fraction of the beam at all points along its path. As a subsidiary result, we also present measurements of the relative and absolute efficiencies of the V/G Supavac mass analyzer for masses 1 and 2

Research and development activity in support of LCP

The research and development activity (RDAC) established in support of the Large Coil Program (LCP) at Oak Ridge National Laboratory (ORNL) is described. Some experimental results are presented and the importance of the RDAC to the magnet community is discussed

Empirical scaling formulas for critical current and critical field for commercial NbTi

This paper presents the results of an analysis of both published and unpublished critical current data given as a function of both field and temperature. Simple formulas have been obtained for (1) the critical temperature as a function of field that is needed to obtain an estimate of the current sharing temperature and hence temperature margin, (2) the critical current density for constant temperature as a function of field, and (3) the critical current density for constant field as a function of temperature

A hybrid beam design for slow positron transport

The authors report on the design of a hybrid transport system for slow positrons based upon the high-intensity magnetically transported positron beam, which existed at the Brookhaven (BNL) high-flux beam reactor (HFBR) in 1986. The resulting modified transport, incorporating an initial electrostatic stage followed by a magnetic stage and completed by brightness enhancement moderation leading to a final electrostatic section, represented the minimum alteration of the existing beam to enable it to be used for crossed-beams differential scattering studies involving a variety of atomic and molecular systems, including atomic hydrogen. A recent proposal for constructing a very high-intensity positron beam at the Paul Scherrer Institute (PSI), based upon magnetic confinement premoderation, has rekindled interest in the conclusions of the study

A hybrid beam design for slow positron transport

The authors report on the design of a hybrid transport system for slow positrons based upon the high-intensity magnetically transported positron beam, which existed at the Brookhaven (BNL) high-flux beam reactor (HFBR) in 1986. The resulting modified transport, incorporating an initial electrostatic stage followed by a magnetic stage and completed by brightness enhancement moderation leading to a final electrostatic section, represented the minimum alteration of the existing beam to enable it to be used for crossed-beams differential scattering studies involving a variety of atomic and molecular systems, including atomic hydrogen. A recent proposal for constructing a very high-intensity positron beam at the Paul Scherrer Institute (PSI), based upon magnetic confinement premoderation, has rekindled interest in the conclusions of the study

A hybrid beam design for slow positron transport

The authors report on the design of a hybrid transport system for slow positrons based upon the high-intensity magnetically transported positron beam, which existed at the Brookhaven (BNL) high-flux beam reactor (HFBR) in 1986. The resulting modified transport, incorporating an initial electrostatic stage followed by a magnetic stage and completed by brightness enhancement moderation leading to a final electrostatic section, represented the minimum alteration of the existing beam to enable it to be used for crossed-beams differential scattering studies involving a variety of atomic and molecular systems, including atomic hydrogen. A recent proposal for constructing a very high-intensity positron beam at the Paul Scherrer Institute (PSI), based upon magnetic confinement premoderation, has rekindled interest in the conclusions of the study

High-field, high-current-density, stable superconducting magnets for fusion machines

Designs for large fusion machines require high-performance superconducting magnets to reduce cost or increase machine performance. By employing force-flow cooling, cable-in-conduit conductor configuration, and NbTi superconductor, it is now possible to design superconducting magnets that operate a high fields (8-12 T) with high current densities (5-15 kA/cm/sup 2/ over the winding pack) in a stable manner. High current density leads to smaller, lighter, and thus less expensive coils. The force-flow cooling provides confined helium, full conductor insulation, and a rigid winding pack for better load distribution. The cable-in-conduit conductor configuration ensures a high stability margin for the magnet. The NbTi superconductor has reached a good engineering material standard. Its strain-insensitive critical parameters are particularly suitable for complex coil windings of a stellarator machine. The optimization procedure for such a conductor design, developed over the past decade, is summarized here. If desired a magnet built on the principles outlines in this paper can be extended to a field higher than the design value without degrading its stability by simply lowering the operating temperature below 4.2 K. 11 refs., 3 figs

Internally Cooled Cable Superconductor (ICCS) for TF and PF coils of FED

Internally Cooled Cable Superconductor (ICCS) concepts developed for TF and PF coils of FED are described. These concepts represent one of the options for FED, and other conductor concepts are still being explored, i.e., no decision has been made for the conductor concepts to be utilized for FED. The TF coil conductor design is based on an ICCS successfully used in a small test magnet at ORNL. The conductor consists of triplets of NbTi strands loosely packed in a stainless steel conduit similar to the Westinghouse LCP coil. The operating current for the conductor is 25.5 kA at l0T and 3.1/sup 0/K. The conductor is co-wound with a stainless steel C-shaped channel to provide a direct load path to the coil case for the accumulated magnetic loads in the winding. The strand diameter in the conductor is optimized to reduce the eddy current losses. The nuclear heating in the winding is the most dominant heat load. In order to remove these heat loads due to nuclear heating and ac losses in the winding, it is necessary to lower the inlet temperature of helium to 2.2/sup 0/K. The conductor has a thermal capacity of approx. 200 mJ/cc, which provides a comfortable stability margin under the operating conditions