Reported are measurements on the high‐frequency fields generated by a relativistic electron beam plasma interaction in the BP II experiment. Measurements are done at fixed positions as well as integrated over the length of the experiment. At fixed positions time‐resolved spectroscopy on hydrogen and helium lines is applied. The integrated measurements are performed with a magnetic energy analyzer, which measures the energy distribution of the relativistic electron beam at the end of the experiment. Spectroscopic measurements of the dynamic Stark effect and forbidden transitions lead to hf fields with amplitudes in the order of 1 MV/m. The interpretation of the beam energy spectra suggests localized fields with field strengths as great as 108 V/m.

Observation of high‐frequency fields due to the interaction of a relativistic electron beam with a plasma

Relativistic electron beams and beam-plasma interaction

The injection of a relativistic electron beam ( nu mod gamma =0.16) into vacuum, results in the formation of a virtual cathode. As a consequence a hollow current density profile is measured beyond the virtual cathode. But the measurement of the angular distribution of the electron velocities indicates that it remains dominated by scattering in the anode foil. Transmitted beam currents are greater than the stationary vacuum limiting current of Bogdankevich, and Rukhadze (1971). Electron beam trajectory calculations, taking into account the electromagnetic beam potential and foil scattering, are capable of describing the virtual cathode. Similar to the calculations of Thode et al. (1979), the hollow profile is steeper than the measured profile and in both cases the calculated limiting current is too small.

http://iopscience.iop.org/article/10.1088/0032-1028/24/6/010/pdf

Angular distribution and radial profile of a relativistic electron beam in vacuum

Describes the construction and operation of a retarding field energy analyser intended to measure the distribution of both beam and plasma electrons in a high-power beam-plasma system. The analyser has been tested in an axial magnetic field up to 0.2 T, applying retarding voltages up to 10 kV. The paper is devoted to a review of problems and their solutions met in the design of such an energy analyser.

http://iopscience.iop.org/article/10.1088/0022-3735/10/3/027/pdf

The construction of a retarding field energy analyser

Presents an analysis of the influence of heavy-gas end plugs on the axial electron heat conduction losses of a plasma column. It is shown that end plugs of highly ionized heavy-gas plasmas increase the energy confinement time.

The increase of energy confinement by the use of heavy-gas end plugs

The energy distribution of a relativistic electron beam which has interacted with a plasma was investigated. The beam parameters were 550 keV, 500 A, and 20 ns (full width at half-maximum). From the broadening of the energy spectrum by interaction with the plasma we calculated the axial-wave electric field of the electrostatic beam-plasma instability to be E approx. = 1.8 x 10/sup 6/ V/m. This is in reasonable agreement with values predicted from theory.

Energy distribution of a relativistic electron beam interacting with plasma

Injection of a 500 A electron beam into a precreated plasma results in heating of plasma electrons to temperatures of 400 eV. The heating occurs only in a finite region of the plasma column near the diode. The amount of energy transfer is of the same order as theoretical estimates for electron-electron two-stream interaction, whereas the calculated growth rate enables saturation during the short beam pulse of 20 ns.

Plasma heating by a low current relativistic electron beam

A note on the heating of the cold plasma blanket in a linear fusion reactor

On the injection of a cold relativistic electron beam into a cold plasma

Discusses the time resolution of p-i-n photodiodes applied as electron detectors. The rise time was found to be of the order of 1 ns, which is equal to that in the case of photon detection. However, it appears that in electron detection the initially fast decay turns over in an exponential decay with a time constant of about 30 ns. A simple algorithm is presented that corrects the recorded waveform for the effects of this tail.

B. Jurgens

Papers

Energy distribution of a relativistic electron beam interacting with plasma

Plasma heating by a low current relativistic electron beam

A note on the heating of the cold plasma blanket in a linear fusion reactor

On the injection of a cold relativistic electron beam into a cold plasma

Time resolution of a p-i-n photodiode applied as electron detector