Cratering behavior in single- and poly-crystalline copper irradiated by an intense pulsed ion beam Page: 4 of 10
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Cratering Behavior in Single- and Poly-Crystalline Copper
Irradiated by an Intense Pulsed Ion Beam
B. P. Wood, L. J. Bitteker, W. J. Waganaar
Plasma Physics Group, MS-E526, Los Alamos National Laboratory, Los Alamos, NM 87545
A. J. Perry
A.I.M.S. Marketing, 10921 Corte Calandria, San Diego, CA 92127
Abstract
When treated with intense pulsed ion beams (IPIB), many materials exhibit increased wear
resistance, fatigue life, and hardness. However, this treatment often results in cratering and
roughening of the surface. In this work, high purity single crystal and polycrystalline copper
samples were irradiated with pulses from an IPIB to gain insight into the causes of this cratering
behavior. Samples were treated with 1, 2, 5, and 10 shots at 2 J/cm2 and 5 J/cm2 average energy
fluence per shot. Shots were about 400 ns in duration and consisted of a mixture of carbon,
hydrogen, and oxygen ions at 300 keV. It was found that the single crystal copper cratered far
less than the polycrystalline copper at the lower energy fluence. At the higher energy fluence,
cratering was replaced by other forms of surface damage, and the single crystal copper sustained
less damage at all but the largest number of shots. Molten debris from the Lucite anode (the ion
source) was removed and redeposited on the samples with each shot.
Introduction
Intense Pulsed Ion Beams (IPIB) have been under investigation for a number of years in Japan,
the Former Soviet Union, Germany, and the United States for materials processing applications
[1-7]. Such IPIB devices typically produce beams of 10's of kiloamps current at 100's to 1000's
of kilovolts, in pulses of 50 -1000 ns. Although these are called "ion beams", they are, in fact
beams of neutral plasma - although only the ions are initially accelerated, electrons are pulled off
surfaces to provide quasi-neutrality.
When treated with by IPIB, many materials exhibit increased wear resistance, fatigue life, and
hardness. However, this treatment often results in cratering and roughening of the surface [8-
10], which undergoes rapid melting and resolidification. Although IPIB treatment of pure
materials such as copper [8,9] and silicon [111 has been studied, it is not clear whether this
cratering damage results from alloy content, explosive behavior of impurities at grain
boundaries, grain structure itself, or impact of debris on the molten surface.
In the work reported here, high purity single crystal and polycrystalline copper samples were
irradiated with pulses from an IPLB to gain insight into the causes of this cratering behavior.
Samples were treated with 1, 2, 5, and 10 shots of 400 ns duration at 2 J/cm2 and 5 J/cm2 average
energy fluence per shot. Following treatment, the samples were examined for damage with a
scanning electron microscope.1
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Wood, B. P.; Bitteker, L. J.; Waganaar, W. J. & Perry, A. J. Cratering behavior in single- and poly-crystalline copper irradiated by an intense pulsed ion beam, report, December 31, 1998; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc677118/m1/4/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.