Generation Of High-current Electron Beams Research Articles

High current electron beam generation in a vacuum transient hollow cathode discharge

Experimental observations are presented of prebreakdown electron beam generation in a transient hollow cathode discharge (THCD) in a vacuum. The discharge driver consists of a 400-kV maximum voltage, 25-nF Marx operated at 450-J stored energy coupled to a 120-ns, 1.5- Omega coaxial line. Electron beams with peak currents up to tens of kA are observed when a pulsed Nd:YAG laser is used to produce a plasma at the back of the cathode surface, inside the hollow cathode region (HCR). It is found that a plasma density of a few 10/sup 18/ cm/sup -3/ in a volume of a few mm/sup 3/ is required to generate intense electron beams. Optimal conditions are determined by varying the position of the laser focal spot inside the HCR and the time delay between the laser and the applied voltage. The main features of the electron beams are similar to those observed in conventional THCD at pressures in the 10-200 mtorr range. >

Electron Beam Visualization in Hypersonic Airflows

The electron beam fluorescence technique has been employed for visualizing hypersonic airflow fields. A high current electron beam generator was used to provide electron beams with currents up to 50 ma at voltages up to 20 kv. Applications of the technique at low densities illustrate that many details of the flowfield can be obtained in density regions where conventional optical systems fail to yield useful results. Techniques for obtaining quantitative density measurements with photographic techniques are discussed. The value and versatility of the method is demonstrated by results obtained with a sharp cone model and an advanced ramjet aircraft configuration in a Mach 10 airflow field.