Innovative Development for High Intensity Proton Synchrotron with High Permeability Magnetic Alloy

我们测量了不同类型的高磁导率磁合金（MA）铁芯的各种特性，发现MA铁芯可以产生大于100kV/m的大加速场梯度。这是因为MA磁芯的最大允许磁通量大于2kG，是铁氧体磁芯的10倍。在此基础上，研制了总长度仅为40cm的单间隙高梯度空腔原型。这个空腔由8ma的磁芯组成。在谐振频率约为2的情况下，在最大功率为300kW的射频放大器的限制下，该腔获得了20kV的最大电压。-3MIHz。对应的有效加速场梯度为50kV/m，几乎是普通铁氧体负载加速腔的5倍。该空腔的Q值相对较低（Q-0.6），因此其能带很宽，有利于重离子的加速。该腔体安装在HIMAC上，成功地将He、C、Ne等重离子加速到100MeV/u。为了消除纵向空间电荷阻抗，我们设计了由高磁导率磁合金磁芯组成的“阻抗调谐器”。它被安装在KEK PS主环上。我们观察了相干四极振荡的频移，并推导了非相干同步加速器振荡的频移。总无功阻抗可以估计为位移和波束强度之间的系数。通过阻抗调谐器将测量阻抗从- j2475omega降低到j1182omega。我们证明了空间电荷阻抗是由阻抗调谐器补偿的。

We have measured various characteristics of the different types of high permeability magnetic alloy (MA) core and found that a large accelerating field gradient of more than 100kV/m is possible with the MA cores. This is because the maximum allowable if magnetic flux of the MA core is more than 2kG which is ten times larger than that of the ferrite core. Based on these measurements, the prototype of the single-gap high gradient cavity whose total length is only 40cm has been developed. This cavity consits of 8 MA cores. With this cavity, a maximum voltage of 20kV, which is limited by the rf amplifier whose maximum power is 300kW, has been obtained at the resonant frequency of about 2.-3MIHz so far. This corresponds that the effective accelerating field gradient is 50kV/m, which is almost 5 times larger than that of the ordinary ferrite loaded if accelerating cavity. The Q value of this cavity is relatively low (Q-0.6), thus, its band width is very broad, which would be beneficial for acceleration of heavy ion. This cavity was installed at HIMAC and successfully accelerated heavy ions such as He, C, Ne ions up to several 100MeV/u.We designed the "Impedance tuner" consisting of the inductive material, high permeability magnetic alloy (MA) cores, to cancel the space charge impedance in the longitudinal direction. It was installed in the KEK PS main ring. We observed the frequency shift of the coherent quadrupole oscillations and inferred the shift of the incoherent synchrotron oscillation. Total reactive impedance can be estimated as the coefficient between the shift and beam intensity. The measured impedance is reduced from-j2475OMEGA to-j1182OMEGA by the impedance tuner. We demonstrated the space charge impedance is compensated by the impedance tuner.