Pennsylv t v Library ^ecknical v2ote 92©. 321 SPARK PLANING DAMAGE IN COPPER JOHN J. GNIEWEK, ALAN F. CLARK, AND JOHN C. MOULDER U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. 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Government Printing Office Washington, D.C. 20402 Price: 15 , 50ml HC H„C> and 110ml H PO, at 3 2 3 2 3 4 60-70°C. The dislocation etchant (lMFeCl -6HO, 12MHC1, 0. 25 MHBr) [5] 3 2 was that developed by Young for use on (111) surfaces. The resulting background dislocation density was determined to be about 5x10 /cm . The crystal was then spark-planed with the gap voltage set at 180 volts on a plane perpendicular to the (111) plane. Damage from this oper- ation is revealed by an increasing dislocation density approaching the newly planed surface which appears as the edge in Figs. 1 and 2. The de- fined depth of damage is arbitrary since the dislocation density increase is gradual from the crystal interior. It is defined here as the depth at which the density of dislocation etch pits has increased to the point of 7, 2 being unresolved. This corresponds to a density of about 5x10 /cm . For comparison purposes, an area is marked in Fig. 2 where the average 6/ 2 dislocation density was determined to be approximately 5x10 /cm . As is seen in Fig. 1, the depth of damage is not constant along the length of the crystal. The damage depths tabulated in Table 1 show a spread cor- responding to this variation. The values presented here are in good agree - [6] ment with unpublished work of Hazzledine who measured the damage in copper, as revealed by dislocation etch pits, produced by planing on two ranges (3 and 7) of the same model spark cutter. Table I Spark Cutter Damage Cutting Range Capacitor in Discharge Circuit Depth of Damage (mm) 4 . Z5\i£ 0. 7 - 1.1 5 . 05jxf 0. 4 - 0. 6 6 . Olfjrf 0.3 - 0.4 7 lOpf 0. 2 - 0.3 CD £1 H i— i . 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