The characteristics of low frequency waves in the presence of E x B rotation of a tandem mirror plasma are investigated using the Fraunhofer diffraction method. The observed dispersion relations are in good agreement with those of drift waves including a Doppler shift due to the E x B rotation velocity. The effect of the radial electric field on the drift waves is studied quantitatively by applying a bias voltage to the end plates of the tandem mirror. The fluctuation level is observed to depend on the radial electric field E r . The fluctuation has a maximum value when E r = 0 and decreases with increasing E r , regardless of its sign. The radial confinement time estimated from the particle balance equation decreases as the fluctuation level increases. The dependence of the fluctuation level agrees with that evaluated from the quasi-linear theory of drift wave turbulence.

The Fraunhofer diffraction measurements from a tandem mirror plasma are reported. The successful use of a new multichannel detector array permits a detailed study of k−ω spectra of long-wavelength waves with a few plasma shots. The observed dispersion relations are in good agreement with those of drift wave including a Doppler shift due to E×B rotation velocity.

Neutral hydrogen beams of 13 and 14 keV at equivalent proton currents of 5 and 3 A, respectively, were injected into a target plasma in a tandem mirror. The space potential at plugs increased more than 10 V relative to the space potential at the central cell and was sustained for more than 0.3 ms. The potential increase is due to the heating of electrons with trapped hot ions and is explained by the relation cp^T^lninp/n^).

We report and discuss high-flux generation of circularly polarized γ-rays by means of Compton scattering. The γ-ray beam results from the collision of an external-cavity-enhanced infrared laser beam and a low emittance relativistic electron beam. By operating a non-planar bow-tie high-finesse optical Fabry-Perot cavity coupled to a storage ring, we have recorded a flux of up to (3.5 ± 0.3) × 108 photons per second with a mean measured energy of 24 MeV. The γ-ray flux has been sustained for several hours. In particular, we were able to measure a record value of up to 400 γ-rays per collision in a full bandwidth. Moreover, the impact of Compton scattering on the electron beam dynamics could be observed resulting in a reduction of the electron beam lifetime correlated to the laser power stored in the Fabry-Perot cavity. We demonstrate that the electron beam lifetime provides an independent and consistent determination of the γ-ray flux. Furthermore, a reduction of the γ-ray flux due to intrabeam scattering has clearly been identified. These results, obtained on an accelerator test facility, warrant potential scaling and revealed both expected and yet unobserved effects. They set the baseline for further scaling of the future Compton sources under development around the world.

A millimeter-wave phase-imaging interferometer has been developed for the study of density profiles of the GAMMA 10 tandem mirror. The interferometer uses a 70-GHz klystron oscillator and a quasi-optical transmission system. The probe beam is expanded so as to fill an orthogonal view of a plasma cross section. The view is imaged onto a detector array. The detector array consists of beam-lead GaAs Schottky barrier diodes bonded to antennas fabricated using photolithographic techniques on a fused-quartz substrate. Two types of antennas, bow-tie and Yagi-Uda antennas have been used in order to provide an effective matching to millimeter-wave beams, and compared for the performance of an imaging system. The interferometers have been applied to the central-cell and plug-cell plasmas of GAMMA 10.