The large plasma research device (LAPD), a large, linear plasma research device designed to study space plasma processes, has been constructed at UCLA over the past four years. The LAPD has a 0.5×0.5 m2 oxide-coated cathode as a source which produces a 10-m-long plasma column with densities up to the mid 1012/cm3 range. The linear machine is surrounded by a set of 68 magnet coils which can generate an axial magnetic field of up to 3000 G. The vacuum chamber has 128 radial ports to ensure excellent access for probes and antennas. An internal probe drive capable of moving a set of probes to any position within the plasma column is described in a companion paper. This machine is a scientific instrument in its own right and was designed to be versatile enough to study a large variety of phenomena. The techniques employed in the design and construction are sufficiently useful to be discussed here so that others can benefit from our experience.

This article shows how a simple Christmas ribbon can be used to demonstrate a relatively complex physical phenomenon: the conservation of helicity during magnetic reconnection. The physical term, helicity, and the process of magnetic reconnection will be introduced and explained in detail. The ‘‘helicity meter,’’ a very simple device that will help in the determination of the helicity of certain topological configurations, will also be introduced.

During the first semester of our calculus-based introductory physics course sequence, students work in small groups on mechanics projects. Many teams choose digital video analysis for projects involving mechanics. We discuss the management of collaborative projects and schemes for critiquing collaborative papers and assigning individual grades. We also describe some of the more interesting projects. Finally, we offer some advice on how to find the information needed to create good digital video movies.

A neutral magnetic sheet, in which the current is carried mainly by the electrons, is set up in a laboratory plasma. By forcing the current through a thin slot, the ratio of the length to height t of the sheet may be varied; the current is observed to tear when t≳30. The structure of the magnetic islands and their associated currents is fully three dimensional, although a linear two-dimensional theory gives a very good estimate of the tearing mode growth time. Tearing is accompanied by the generation of significant Hall currents, and magnetic disturbances are observed to propagate at the whistler wave speed.

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