A new type of charging belt for Van de Graaff accelerators
In 1978 Lawrence Berkeley Laboratory acquired a surplus 2.5 million volt High Voltage Engineering (HVEC) Model AK-2000 Accelerator. Several problems with the charging belt were encountered during the course of reconditioning. The machine was received with a standard HVEC rubberized cotton belt. During initial electrical testing the belt was found to experience ''mole-hole'' failures at an alarmingly high rate. This failure mode is characterized by the carbonization of a linen fiber down the length of the belt. The resulting fiber expands leaving a tell-tale bump on the surface of the rubberization, thus the term ''mole-hole.'' This carbonized fiber, when long enough, can provide an electrical leakage path along the belt which can short the terminal to ground. Several belts were destroyed in this manner. Discussions with HVEC centered on the topic of residual moisture left in the carcass of the HVEC style belts. Thus an attempt to remove moisture from the tank was initiated. The effort entailed multiple serial dilutions of the residual moisture by evacuating the tank below 70 microns (with the belt installed) and then back-filling the tank with dry nitrogen to a pressure of 25 PSIG. This procedure was repeated until the dew point of the nitrogen (measured 2 hours after backfilling) was below -70/sup 0/C. The tank was then pressurized with SF/sub 6/ to 70 PSIG. This method reduced the belt failures substantially, but did not totally eliminate the problem.
- Research Organization:
- Lawrence Berkeley Lab, Charles Evans and Assoc., 1670 S. Amphlett Boulevard, Suite 120, San Mateo, CA 94402
- OSTI ID:
- 5550321
- Journal Information:
- IEEE Trans. Nucl. Sci.; (United States), Vol. 30:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
VAN DE GRAAFF ACCELERATORS
MAINTENANCE
OPTIMIZATION
ELECTROSTATICS
FAILURES
LAWRENCE BERKELEY LABORATORY
REACTOR FUELING
ACCELERATORS
ELECTROSTATIC ACCELERATORS
NATIONAL ORGANIZATIONS
US AEC
US DOE
US ERDA
US ORGANIZATIONS
430100* - Particle Accelerators- Design
Development
& Operation