Beam Dynamics Studies Research Articles

Computational Studies of Beam Dynamics in the ETA Gun

A new general purpose computer code call EBQ, has been written to simulate the beam dynamics of the ETA, find its beam emittance and evaluate effects of changes in the electrode positions and external magnetic fields. The original calculations of the ETA were made with EGUN and yielded considerable insight into the operation of the device in the non-relativistic regime. The EBQ code was written specifically to attend to the special problems associated with high current relativistic beam propagation in axially symmetric machines possessing external 2-dimensional electric and magnetic fields. The coherent electric and magnetic self-fields of the beam must be calculated accurately. Special care has been used in the relativistic regime where a high degree of cancellation occurs between the self-magnetic and self electric forces of the beam. Additionally, EBQ can handle equally well non-relativistic problems involving multiple ion species where the space charge from each must be included in its mutual effect on the others. Such problems arise in the design of ion sources where different charge and mass states are present.

HEATING OF DENSE PLASMA BY INTENSE RELATIVISTIC BEAMS

Preliminary experiments are described that utilize some of the unique properties of intense electron beams to help achieve the necessary conditions of high energy and power density. The experiments are divided into two groups, dealing with the study of beam dynamics and with plasma heating. (MOW)

Dynamics of intense relativistic electron beams in toroidal fields

Intense relativistic electron beams were propagated around a 180° toroidal sector to study beam dynamics in toroidal fields. The major beam drift under conditions for neutralization of self-fields was along - R × B and scaled as γZ/Bt, where Z is the propagated distance, Bt the toroidal field, and γ the relativistic factor. This is indicative of curvature and ∇B drifts. Use of conducting walls caused an additional F × B drift around the chamber due to image current forces. Analysis of the distortion of a propagating rectangular beam shows that beam electrons follow field lines. Preliminary experiments on counterstreaming beams show inefficient reflection of beams from opposing diodes. Application of these results to beam injection and confinement in toroidal magnetic fields is discussed.

Recent Investigations of the Orsay Group on RF Properties and Applications of Superconducting Cavities

After a large development of our experimental studies on high stability oscillators, a theoretical work on different physical processes able to induce localized transitions to the normal state at high field level in superconducting cavities, is in progress. A theoretical study of beam dynamics in low energy electron linacs (in the 1-5 MeV range) shows that a standing wave structure have interesting focusing properties for short bunches injected in the "unstable" rhase domain, and that a single TM010 cavity could be used to obtain electrons of 2 MeV.

Beam Dynamical Calculaticns with Realistic Fields in a Drift Tube Linear Accelerator

A method for numerical beam dynamics studies of drift tube type linear accelerators using electromagnetic fields similar to those encountered in actual machines is presented. Results of calculations for a 90 mev accelerator are given and comparisons made with similar calculations in which the axial electric field is assumed spatially constant within the accelerating gap.