Beam Requirements for a Two Stream Instability Amplifier
Abstract
Theoretical and simulation work has raised the possibility of a GW-class two-stream instability based amplifier using two co-propagating relativistic beams of different currents and energies that achieves high efficiency (50 ). With some selected beam parameters, we have achieved simulated signal gains in excess of 35dB in the squared amplitude of beam modulation ~I2, which is proportional to the maximum RF power that could be extracted. We have investigated the effect of beam temperature and annular beam thickness on the performance of this device. Beam energy spread has to be kept very low (< 1 of the beam energy) to achieve high levels of bunching in the beams, failure to do so can result in > 75 loss in magnitude of ~Imax. Also, the thickness of the annular beams used has to be tightly constrained, or similar performance degradation results. Beam energy spread is shown to influence the maximum achievable bunching prior to saturation, while not modifying growth rate. These beam energy spread constraints combined with the requirement to produce very high current (multi-kA), very small radius (< 2cm), very small thickness (<= 1mm) beams makes practical realization of a 100MW amplifier based on relativistic two-stream instability challenging. Attempts to relax these constraints by moving from a 9GHz amplifier to a larger 3GHz amplifier have resulted in performance degradation while still posing a presently insurmountable problem for the electron beam gun designer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 23, 2017
- Accession Number
- AD1060082
Entities
People
- Michael Lambrecht
- Peter Mardahl
Organizations
- Air Force Research Laboratory