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Title: Fabrication of tungsten wire needles

Fine point needles for field emissoin are conventionally produced by electrolytically or chemically etching tungsten wire. Points formed in this manner have a typical tip radius of about 0.5 microns and a cone angle of some 30 degrees. The construction of needle matrix detector chambers has created a need for tungsten needles whose specifications are: 20 mil tungsten wire, 1.5 inch total length, 3 mm-long taper (resulting in a cone angle of about 5 degrees), and 25 micron-radius point (similar to that found on sewing needles). In the process described here for producing such needles, tungsten wire, immersed in a NaOH solution and in the presence of an electrode, is connected first to an ac voltage and then to a dc supply, to form a taper and a point on the end of the wire immersed in the solution. The process parameters described here are for needles that will meet the above specifications. Possible variations will be discussed under each approprite heading.
Authors:
Publication Date:
OSTI Identifier:
6133580
Report Number(s):
SLAC-TN-83-7
ON: DE83012025
DOE Contract Number:
AC03-76SF00515
Resource Type:
Technical Report
Research Org:
Stanford Linear Accelerator Center, CA (USA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; ELECTRODES; FABRICATION; FIELD EMISSION; FILAMENTS; RADIATION DETECTORS; TUNGSTEN; WIRES; ELEMENTS; EMISSION; MEASURING INSTRUMENTS; METALS; TRANSITION ELEMENTS 360101* -- Metals & Alloys-- Preparation & Fabrication; 420800 -- Engineering-- Electronic Circuits & Devices-- (-1989)