Relativistic klystrons

Experimental work is underway by a SLAC-LLNL-LBL collaboration to investigate the feasibility of using relativistic klystrons as a power source for future high gradient accelerators. Two different relativistic klystron configurations have been built and tested to date: a high grain multicavity klystron at 11.4 GHz and a low gain two cavity subharmonic buncher driven at 5.7 GHz. In both configurations power is extracted at 11.4 GHz. In order to understand the basic physics issues involved in extracting RF from a high power beam, we have used both a single resonant cavity and a multi-cell traveling wave structure for energy extraction. We have learned how to overcome our previously reported problem of high power RF pulse shortening, and have achieved peak RF power levels of 170 MW with the RF pulse of the same duration as the beam current pulse. 6 refs., 3 figs., 3 tabs

(A) A MULTI-AMPERE HEAVY ION INJECTOR FOR LINEAR INDUCTION ACCELERATORS USING PERIODIC ELECTROSTATIC FOCUSING*

One of the key problems for the accelerator system for a heavy ion fusion (HIF) power plant is to provide a source of ions at the parameters, principally energy and intensity, that are well matched for the primary accelerator component. A promising candidate for the primary accelerato

(A)- A CHARGE SEPARATING SPECTROMETER FOR ANNULAR ION BEAMS*

The need for very high currents of low-velocity heavy ions requires some new approaches to the transport and acceleration problem. One such approach, described in reference 1, would use a configuration of alternating accelerating and decelerating fields applied by rails or rings to the ion beam, which is configured in thin sheets in order to make this method of focusing effective. The annular ring configuration of the focusing structure is attractive because of the absence of end effects. In applying this system to a heavy ion injector for a linear induction accelerator (LIA>, it is noted that it may be desired to accelerate multiple- charged ions in order to reduce the length and cost of the accelerator. The same conclusion can be drawn for the drift tube linac, which could be very long if only 1 or 2 MeV are gained per section. Thus, in the example parameters shown in reference 1, it is suggested that a stripping and charge- state separation system be located at the 4 MeV point between tanks No. 2 and No. 3. This report will describe an annular spectrometer system for the charge separator

Computer simulation of the Lasertron

The concept of the Lasertron can be most easily described by referring to the figures. A short bunch of electrons (short in time compared to the period of an rf cycle), is emitted from the cathode and accelerated by a dc potential toward the anode. An rf cavity, located just past the anode aperture, is the output cavity. The rf frequency is determined by the pulse rate of the electron bunches. Although other types of solid-state cathodes are possible, if a photo-cathode is used, then the light source will likely be a fast pulsing laser, hence the name Lasertron. The device cannot be properly called a Laser klystron since that name implies the waves of rf current by which a dc beam is bunched. In the Lasertron, the electrons are emitted bunched and it is only necessary to accelerate them before space charge forces cause too much debunching

Heavy ion fusion: prospects and status

The main purpose of this talk is to review the status of HIF as it was presented at Princeton, and also to try to deduce something about the prospects for HIF in particular, and fusion in general, from the world and US political scene. The status of the field is largely, though not entirely, expressed through presentations from the two leading HIF efforts: (1) the US program, centered at LBNL and LLNL, is primarily concerned with applying induction linac technology for HIF drivers; (2) the European program, centered at GSI, Darmstadt, but including several other laboratories, is primarily directed towards the rf linac approach using storage rings for energy compression. Several developments in the field of HIF should be noted: (1) progress towards construction of the National Ignition Facility (NIF) gives strength to the whole rational for developing a driver for Inertial Fusion Energy; (2) the field of accelerator science has matured far beyond the status that it had in 1976; (3) Heavy Ion Fusion has passed some more reviews, including one by the Fusion Energy Advisory Committee (FEAC), and has received the usual good marks; (5) as the budgets for Magnetic Fusion have fallen, the pressures on the Office of Fusion energy (OFE) have intensified, and a move is underway to shift the HIF program out of the IFE program and back into the ICF program in the Defense Programs (DP) side of the DOE