Automated system for measuring vacuum outgassing rates
Particle accelerators and particle physics detectors require large electrical insulators with metal embedments having vacuum on one side and an insulating fluid or gas on the other. For high vacuum requirements they may be fabricated out of sintered alumina using vacuum brazing to attach the metal pieces. Although this produces quite acceptable devices, it is very time-consuming and expensive, involving the pressing, firing and grinding-to-size of the alumina parts, the manufacture of a brazing fixture and the fabrication of the individual braze foils. After firing in a vacuum oven, if there are any vacuum leaks in the braze joints, the part usually must be rejected. For moderate vacuum service one can use cast or machined plastics which are glued together. Although this is a much less expensive fabrication method, the vacuum outgassing rates of these assemblies can be three orders of magnitude higher than the brazed alumina ones, which may be unacceptable for many applications. It was with these ideas in mind that the authors undertook a program at LBL to develop castable insulators using plastics filled with inorganic materials. The systems were selected mostly on the basis of manufacturer's data on the electrical and mechanical performance of the materials in electrical utility service. Very little data was available on vacuum outgassing. In the course of making the necessary vacuum outgassing measurements, it became clear that if data-taking were automated it could be easily done with a few hours labor per week per sample rather than about the 8 hours/sample required with manual data acquisition and analysis. The system that was developed is based on a Hewlett Packard HP-85 computer which controls the experiment and then evaluates the data and plots it. The measuring system uses the conductance of a fixed orifice and the readings of two Bayard-Alpert gauges to determine outgassing rates.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5420525
- Report Number(s):
- LBL-19326; ON: DE85016509
- Resource Relation:
- Other Information: Paper copy only, copy does not permit microfiche production. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
Similar Records
Vacuum outgassing rates of plastics and composites for electrical insulators
NOVEL REFRACTORY MATERIALS FOR HIGH ALKALI, HIGH TEMPERATURE ENVIRONMENTS
Related Subjects
47 OTHER INSTRUMENTATION
DEGASSING
MEASURING METHODS
VACUUM SYSTEMS
PERFORMANCE
ACCELERATORS
AUTOMATION
BAYARD-ALPERT GAGES
COMPUTER CODES
ELECTRICAL INSULATION
ELECTRICAL INSULATORS
INORGANIC COMPOUNDS
INSULATING OILS
LAWRENCE BERKELEY LABORATORY
ELECTRICAL EQUIPMENT
EQUIPMENT
IONIZATION GAGES
MEASURING INSTRUMENTS
NATIONAL ORGANIZATIONS
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PRESSURE GAGES
US AEC
US DOE
US ERDA
US ORGANIZATIONS
VACUUM GAGES
420700* - Engineering- Vacuum Engineering- (-1987)
440300 - Miscellaneous Instruments- (-1989)