ELECTRON BEAM STABILITY IN COMPACT RECIRCULATING ACCELERATORS

STABLE BEAM TRANSPORT IS A CENTRAL ISSUE IN DEVELOPING COMPACT HIGH CURRENT ELECTRON BEAM RECIRCULATING INDUCTION ACCELERATORS. POTENTIALLY DANGEROUS INSTABILITIES INCLUDE THE NEGATIVE MASS, THE BEAM BREAKUP (FOR INDUCTIVE GAPS DESIGNS), AND THREE-WAVE (FOR STRONG FOCUSING DESIGNS). MISSION RESEARCH CORPORATION PROPOSES TO DETERMINE THEIR SERIOUSNESS FOR HIGH CURRENT RECIRCULATING ACCELERATORS AND TO ESTABLISH BEAM AND ACCELERATOR PARAMETERS WHICH MINIMIZE THEIR DISRUPTIVENESS. EMPHASIS WILL BE PLACED ON SPIRAL LINE DEVICES, ALTHOUGH THE RESULTS OBTAINED WILL BE APPLICABLE MORE GENERALLY. SPECIFIC PHASE I ACTIVITIES ARE (1) GENERALIZING AN EXISTING BEAM BREAKUP INSTABILITY COMPUTER CODE TO TREAT PROPERLY THE OVERLAPPING RESONANT MODES OF A VERY LOW Q CAVITIES AND THEN EMPLOYING THIS CODE TO OBTAIN BETTER PREDICTIONS OF BEAM BREAKUP GROWTH IN THE SPIRAL LINE ACCELERATOR, (2) DETERMINING THE GROWTH RATES OF THE NEGATIVE MASS INSTABILITY AT HIGH MODE NUMBERS, WHERE ELECTROMAGNETIC RESONANCES ARE IMPORTANT, AND (3) ASSESSING PROPOSED METHODS OF SUPPRESSINGTHREE-WAVE INSTABILITIES.