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Appendix C Excerpts from the Draft Report of the Workshop on Plasma Physics Research on the Space Station PLASMA PROCESSES [ABO1lATORY In 1985 a workshop was held to explore the feasibility of the Plasma Processes Laboratory for the Space Station. Scien- t~ts from plasma and fusion research laboratories throughout the United States participated in this workshop. After three days of vigorous discussion, the workshop partic- ipants identified a number of interesting ideas for basic scientific and technological experiments on the Space Station. In each case there is ~ solid scientific reason for pursuing these concepts on the Space Station as opposed to In the laboratory. Also, plasma physics as a discipline has much to offer the Space Station com- plex in understanding the plasma environment that surrounds it, and the interaction of a large curren~carrying structure (like the Space Station) with this environment. The development of the basic technologies that would enhance the capabilities of future Space Station investigations ~ also unportant. NOTE: These excerpts are taken from Overview of Space Station Attached Payloads in the Areas of Solar Physics, Solar Terrestrial Physics, and Plasma Processes, by W. T. Roberts, J. Kropp, and W. W. C. Taylor, AIAA Paper 86-2298, September 1986. 109

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110 The advantages of the Space Station to plasma physics may be categorized into two areas environmental and operational. The environmental considerations include: . The possibility of creating ultrahigh vacuum over a large volume. This may be accomplished by shielding the desired volume from the ambient neutral and plasma flow, creating a high-vacuum wake region. ~ An ambient plasma environment uniform over large-sc~e lengths. This makes it possible to perform experimental studies of processes requiring homogeneous background conditions over interaction lengths attainable only in space. ~ The absence of walls and accompanying effects, such as impurity injection, wall currents, and field shorting. ~ The large-scale steady plasma flow past the Space Station due to its orbital velocity. This condition Is difficult to achieve in the laboratory. Combinations of plasma parameters in the Space Station environment that are ideal for qualitative scaling of space phe- . nomena. ~ The absence of gravity. This permits a category of ex- perunents that are difficult on Earth, involving colloidal or dusty plasmas as well as certain technology studies involving such effects as breakdown of insulation in mists. Additionally, levitation of components for achieving various boundary conditions or magnetic fields is sunplified, possibly leading to previously unattainable field topologies. Operational considerations include such factors as: . Long-duration data bases. In contrast to Shuttle-borne missions, it will be possible to explore wider variations of experi- mental and environmental parameters with correspondingly more comprehensive investigation. Experiments that would yield too few data during a Shuttle flight may be contemplated. ~ The ability to modify experiments during the course of an investigation. The scientific return from Space-Station-based experiments can be qualitatively greater because of an investiga- tor's ability to respond to unanticipated results or to modify (to some degree) the experimental configuration as new objectives are indicated by interun data. This mode of operation will lead to a hands-on, laboratory-like capability.

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111 . Maneuverable platforms, tethers, and other adjuncts, which will allow great flexibility in experimental configurations and diagnosis. The large-scale sizes available in space, already mentioned above in the context of enabling experunents involving long in- teraction lengths, will also peanut much greater diagnostic access than in ground-based experunents. The workshop participants, after developing basic evaluation criteria, described nine very broad exper~rnent categories that could effectively be addressed by the Plasma Processes Labora- tory. I. Investigations of the interaction of the large Space Station with the surrounding plasma environment. 2. Investigations of potential buildup on objects in the space plasma environment. 3. Studies of the plasma flow about objects. 4. Investigations of the basic mechanisms of nonlinear particle and wave interactions. 5. Studies of plasma shocks. 6. Investigations of beam-plasma interactions. 7. Investigations of plasma toroide. S. Studies of the fundamental physics of dusty plasmas. 9. Studies of the physics of plasmas in a m~crogravity envi- ronment.