METHOD OF MAKING TUNGSTEN FILAMENTS
A method of making tungsten filaments is described in which the tungsten is completely free of isotope impurities in the range of masses 234 to 245 for use in mass spectrometers. The filament comprises a tantalum core generally less than 1 mil in diameter having a coating of potassium-free tantalum-diffused tungsten molecularly bonded thereto. In the preferred process of manufacture a short, thin tantalum filament is first mounted between terminal posts mounted in insulated relation through a backing plate. The tungsten is most conveniently vapor plated onto the tantalum by a tungsten carbonyl vapor decomposition method having a critical step because of the tendency of the tantalum to volatilize at the temperature of operntion of the filament. The preferred recipe comprises volatilizing tantalum by resistance henting until the current drops by about 40%, cutting the voltage back to build up the tungsten, and then gradually building the temperature back up to balance the rate of tungsten deposition with the rate of tantalum volatilization. (AEC)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-008570
- Assignee:
- U.S. Atomic Energy Commission
- Patent Number(s):
- US 3069584
- OSTI ID:
- 4736408
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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