Instability of mismatched beam in the proton linear accelerator

1)晕的形成n束输运系统我的一个研究生，M池上研究晕的形成从不匹配的轴对称光束在一个周期性的通道与博士H冈本（Jpn。应用物理学，第36卷，7028，1997）。采用一维近似的质点网格法进行了计算机模拟。结果表明，与输运系统匹配的束流不会引起束晕，而与输运系统失配的束流由于空间电荷效应会引起束晕。但是在这种情况下，光晕是从起始位置处的相空间分布的外围区域产生的。而在光环一旦被光束准直器刮擦之后，它就不会在此后产生。这是一个有希望的结果，为高强度的束流加速，虽然它是不现实的三维模拟。2）回旋加速器中的空间电荷效应的回旋加速器中的空间电荷效应进行了估计，以比较与直线加速器的加速器驱动系统。采用三次谐波射频场，虽然非线性效应不明显，但在500 MeV下，可以达到10 mA的强度。3）多棒直线加速器和加速器驱动系统（ADS）设计了一种独特结构的束流回旋多棒直线加速器。该直线加速器各通道的束流透过率均小于50%，但总束流强度可超过普通单通道直线加速器，并为京都大学研究堆研究所的未来项目提出了一个ADS。

1) halo formation n beam transport systemOne of my graduate students, M.Ikegami studied halo formation from mismatched axisymmetric beams in a periodic channel with Dr. H.Okamoto (Jpn. Appl. Phys., Vol. 36, 7028, 1997). The computer simulation was made by particle-in-cell method with one dimensional approximation. The result shows that a matched beam to the transport system does not cause beam halo but a mismatched beam causes halo by space charge effect. But in this case the halo is created from the peripheral region of the phase space distribution at the starting position. And after the halo is once scraped by a beam collimator it is not created thereafter. This is a hopeful result for a high intensity beam acceleration though it is not realistic three dimensional simulation.2) Space charge effect in a cyclotronThe space charge effect in the cyclotron was estimated to be compared with a linac for an accelerator driven system. The intensity of l0mA at 500MeV may be attainable with third harmonic RF field though the non-linear effect is ambiguous.3) Multi-rod RFQ linac and accelerator driven system (ADS)A unique structure multi-rod RFQ linac in which beams slalomed was designed. The beam transmission of each channel of the linac is less than 50%, but total beam intensity of the linac can be very much than a usual single channel RFQ linac.An ADS was proposed for the future project of Kyoto University Research Reactor Institute.