Creator:B.E. Abey, R.M. Emrick, and C.T. Tomizuka
Date Created:
Place Created:Tucson, Arizona
Keywords:high resitance electrical leads
Context:report on work done for the Air Force Office of Scientific Research
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HIGH RESISTANCE ELECTRICAL LEADS FOE HXCSi PRESSURE APPLICATIONS15
B. E Abey, R. M. Einrick end C. T. Toraisuka
Department of Physics The University of Arizona Tucson., Arizona
«This work was sponsored in part; *oy the Air Force Office of -Scientific Research under Contract AF49{ 638} -790 and the U.S. Atomic Energy Consnission under Contract AT{ 13.-1 }-lC4l
2
Epoxy and similar substances have been used for some
time in the making of electrical lead-ins for high prosit p q
sure apparatus. 3 It has been found that an extremely simple type of epoxy electrical lead-in gives a very high resistance between the electrical lead and the high pressure apparatus. The resistance at room temperature is infinite as measured on a General Radio type 544B megohm bridge. At 50° C. the resistance is 1012 ohum; at 100° C., 2 x 1011 ohms; and at 150° C., 5 x 1010 ohms. Work with an internal furnace shows that the resistance of these lead-ins changes very little when the internal temperature of the furnace is increased to 250° C. These epoxy lead-ins are of particular use when the leakage current through the lead-in is of Importance. A diagram of these cones is shown in Fig. 1.
The cones are made from Eccobond 76 epoxy in hardened tool steel (Rockwell 40 C). The cones are constructed by placing a taut copper wire, which passes through the alumina insulator, up the middle of the cone in the apparatus plug. The apparatus plug is then heated by means of
a heat gun until the epoxy flows freely. The epoxy is then applied as shown making sure that no air pockets are
left in the cone. After being allowed to cool to room
temperature the plug is cured for three hours at 110° C.
and for three hours at 150° C.
3
These cones have been used in a liquid system at temperatures from 20° C. to 120° C. at pressures up to 10,000 atin. for short periods of tin® and at pressures up to 8,000 atm. for up to eighty-two hours with very good results. Preliminary tests Indicate that the longevity of these electrical lead-ins is good.
The repair of a damaged cone is quite simple as the old cone can be removed in about five minutes by using a coning tool and replaced in exactly the same mannjr as a new cone is made without touching any of the remaining undamaged cones.
REFERENCES
1.	Blosser, L. G. and H. S. Young, Rev. Sci. Ins. 33, 1007 (1962).
2.	Lazane, F., J. Phys. Radium 14, 213 (1953)*
3.	Gugan, D., J. Sci. Instr. 6° (1956).
Fig, 1. Diagram of epoxy resin electrical seal.
1-	COPPER WIRE
2-	EPOXY
3-	APPARATUS PLUG
4-	ALUMINA INSULATOR
5-	1/16" HOLE COUNTERSUNK 16° TO ABOUT .165 DIA.

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