A scanning Fabry-Perot interferometer for use in the far ir (100 microm < < 2 mm) has been developed capable of scanning a free spectral range in a few milliseconds. A commercial loudspeaker was used as a drive, and mirrors were fabricated from electroformed copper mesh. Primary limitations of the instrument were due to vibrations of the interferometer frame.
This is a study of the effects of electron-electron and electron-ion collisions on small oscillations in a fully ionized plasma imbedded in a constant external magnetic field. The first three moments are taken of the Boltzmann equation with the Bhatnagar-Gross-Krook collision terms. The low-temperature approximation is employed to close the set of equations. The moment equations and Maxwell's equations are solved simultaneously to obtain the dispersion relation for small amplitude electron waves propagating at an arbitrary angle to the external magnetic field. The dispersion relation, the collisional damping included, is studied in various limiting cases. The most striking collisional effect is the reduction and smoothing out of the resonance near the electron cyclotron frequency.
It has been observed that the presence of a dense magnetized background plasma can greatly influence the synchrotron emission associated with relativistic electrons. The plasmas studied are produced by electron cyclotron resonance heating in a magnetic mirror geometry. After microwave turnoff, when the background plasma is not present, the usual synchrotron radiation associated with a tenuous distribution of relativistic electrons is observed; during microwave heating when a dense magnetized background plasma is present, the synchrotron intensity may be considerably decreased from the vacuum intensity. The largest decreases are observed at frequencies below the nonrelativistic electron gyrofrequency ωc, in qualitative agreement with the predictions of a test particle model for the synchrotron emission process. The decreases near nωc are due to the absorption of the synchrotron extraordinary mode via cyclotron damping in the finite temperature background plasma. At frequencies above the upper hybrid frequency ωuh(ωuh2 = ωp2+ωc2 the decrease arises because the synchrotron emission occurs into a cutoff mode of the background plasma.
A velocity space instability with frequency near the electron cyclotron frequency f c has been observed in a hot electron plasma. Measurements of the frequency shift above f c, the stability boundary and the growth rate agree well with calculations for the two-component instability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.