Robert L. Kustom

A Dielectric Loaded Slow Wave Structure for Separation of Relativistic Particles

Dielectric loaded waveguides of rectangular cross section are considered as synchronous traveling wave particle separators. These structures support two linearly independent modes: those which have no electric field perpendicular to the dielectric, and those which have no magnetic field perpendicular to the dielectric. Both modes have suitable transverse deflection forces with phase velocities which can be slower than the speed of light. Degeneracies and dispersion relations are discussed. The theoretical conclusions are supported by experimental studies which include slotted line and bead perturbation measurements.

Three-Phase Energy Transfer Circuit with Superconducting Energy Storage Coils

The operation and circuit analysis of a three-phase inductor converter bridge (ICB) is described. The ICB is used to transfer energy between two superconducting coils and may find application in future tokamak fusion power reactors and large particle accelerators. This circuit provides an efficient, controllable, and reversible means for energy transfer.

A Design Concept for a Planar Superconducting Undulator for the APS

A superconducting planar undulator is under development at the Advanced Photon Source. The R&D phase culminated in the successful testing of several short magnetic structure prototypes. Work is now focused on a complete design for the first undulator. The conceptual designs for its superconducting magnet, the cooling system, and the cryostat are described in this paper.

Intense Pulsed Neutron Sources

Accelerator requirements for pulsed spallation neutron sources are stated. Brief descriptions of the Argonne IPNS-I, the Japanese KENS, Los Alamos Scientific Laboratory WNR/PSR, the Rutherford Laboratory SNS, and the West German SNQ facilities are presented.

RaD of Short-Period NBTI and Nb 3 Sn Superconducting Undulators for the APS

Superconducting undulators (SCUs) with a period of 14.5 mm are under development for the Advanced Photon Source (APS). The undulators have been designed to achieve a peak field on the beam axis higher than 0.8 T with an 8 mm pole gap and current densities over 1 kA/mm2in the NbTi and Nb 3 Sn coils. Upper-half NbTi SCUs of short sections have been fabricated and were charged up to near the critical current density of 1.43 kA/mm2to achieve a peak field about 1 T. The stability margin of the SCU was measured by imposing steady-state heat fluxes on the pole/coil face of the SCU in a pool-boiling liquid He (LHe) dewar at 4.2 K. Near the critical current density, where the temperature stability margin is minimal, the heat flux density to quench the SCU was about 1.3 mW/mm2, of which 60% was attributed to LHe at the interface of the SCU and the vacuum chamber. The peak fields of the SCU were mapped along the beam axis using a Hall probe in a vertical dewar. The first test of a Nb 3 Sn short-section SCU was charged to an average current density of 1.45 kA/mm2, slightly higher than the critical current density for the NbTi SCU.

LIGA fabrication of mm-wave accelerating cavity structures at the Advanced Photon Source (APS)

Recent microfabrication technologies based on the LIGA (German acronym for Lithographe, Galvanoformung, und Abformung) process have been applied to build high-aspect-ratio, metallic or dielectric planar structures suitable for high-frequency rf cavity structures. The cavity structures would be used as parts of linear accelerators, microwave undulators, and mm-wave amplifiers. The microfabrication process includes manufacture of precision X-ray masks, exposure of positive resist by X-rays through the mask, resist development, and electroforming of the final microstructure. Prototypes of a 32-cell, 108-GHz constant-impedance cavity and a 66-cell, 94-GHz constant-gradient cavity were fabricated with the synchrotron radiation sources at APS and NSLS. This paper presents an overview of the new technology and details of the mm-wave cavity fabrication.

Measurements on prototype cavities (352 MHz) for the Advanced Photon Source (APS)

Measurements of the higher order modes of a prototype single-cell 352-MHz cavity for the APS 7-GeV storage ring are presented and discussed. A 352-MHz cylindrical pill-box cavity made of aluminum has been built to test and verify the measurement instruments using the analytically derived resonant frequencies of both the fundamental and higher-order modes. A cavity made from solid copper was built according to dimensions derived from URMEL program runs. The longitudinal and transverse impedances of the first several higher-order modes have been measured using various shaped metal beads.<<ETX>>

A New Diagnostic System for Studying the Injector and Injection at the Zero Gradient Synchrotron (ZGS)

The SFC system provides detailed information about the injector beam and the capture and early acceleration cycle of the ZGS more rapidly and accurately than was previously possible. The system was an important part of the retuning program after the titanium vacuum chamber installation. The SFCs a-re frequently employed in maintaining stable ZGS operation with intense beams.

Development of Short-Period

Superconducting undulators (SCUs) with a period of 14.5 mm are under development for the Advanced Photon Source (APS) using Nb3Sn superconductors. The initial goal is to install a SCU with a 19- to 29-keV tuning range for the first harmonic photon energy. The design of the SCU assembly includes the interface with the beam chamber as an integral part of the assembly. A four-period Nb3Sn half SCU was fabricated and tested. After a number of quenches, the SCU was charged to an engineering current density of 1.92 kA/mm 2 in the coil pack. This corresponds to a peak field of 1.08 T on the beam axis with a pole gap of 8.5 mm. The achieved current density was approximately 90% of the engineering critical current density for the design calculations. With an operating current density of 1.6 kA/mm 2 , the SCU will operate at a peak field of 0.95 T with some degree of stability.

{\rm Nb}_{3}{\rm Sn}

A planar superconducting undulator (SCU) with a period of 15 mm is under development at the Advanced Photon Source (APS). The intended users require a photon energy that can be tuned from 19 to 28 keV for inelastic X-ray scattering studies. The SCU design consists of two low-carbon-steel cores that are positioned above and below the beam chamber. There are 20 turns of NbTi/Cu superconducting (SC) wire within a coil cross section of 4.3 /spl times/ 4.0 (w /spl times/ h) mm/sup 2/. At a pole gap of 8 mm, the necessary average current density in the coil will be about 1 kA/mm/sup 2/ to achieve a peak field of 0.8 T on the beam axis. The design and fabrication progress of a 12-period prototype SCU are presented, and some challenging requirements are discussed.