Eddy Currents in the NSLS Vacuum Chamber

The present Fermilab proton Booster is an early example of a rapid-cycling synchrotron (RCS). Built in 1960s, it features a design in which the combined-function dipole magnets serve as vacuum chambers. Such a design is quite cost-effective, and it does not have the limitations associated with the eddy currents in a metallic vacuum chamber. However, an important drawback of that design is a high impedance, as seen by a beam, because of the magnet laminations. More recent RCS designs (e.g. J-PARC) employ large and complex ceramic vacuum chambers in order to mitigate the eddy-current effects and to shield the beam from the magnet laminations. Such a design, albeit very successful, is quite costly because it requires large-bore magnets and large-bore RF cavities. In this paper, we consider an RCS concept with a thin-wall metallic vacuum chamber as a compromise between the chamber-less Fermilab Booster design and the large-bore design with ceramic chambers.

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Thin Pyrolytic Graphite Films for Electron Microscope Substrates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065183 ◽

1971 ◽

Vol 29 ◽

pp. 226-227 ◽

Cited By ~ 1

Author(s):

George H. N. Riddle ◽

Benjamin M. Siegel

Keyword(s):

Vacuum Chamber ◽

Pyrolytic Graphite ◽

High Vacuum ◽

Dark Field ◽

Ultra High Vacuum ◽

Graphite Substrate ◽

Nickel Substrate ◽

Routine Procedure ◽

Field Electron Microscopy ◽

Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

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