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性合金(MA)磁芯的各种特性，发现MA磁芯有可能产生超过100KV/m的大加速磁场梯度。这是因为MA磁芯的最大允许中频磁通大于2 kg，是铁氧体磁芯的10倍。在此基础上，研制出总长度仅为40 cm的单间隙高梯度腔样机。该腔由8个MA芯组成。到目前为止，在2-3 MIHZ的谐振频率下，获得了20KV的最大电压，这是由最大功率300kW的射频放大器所限制的。相应地，有效加速场梯度为50kV/m，几乎是普通铁氧体加载中频加速腔的5倍。该腔的Q值相对较低(Q-0.6)，因此其带宽很宽，这将有利于重离子的加速。该腔被安装在HIMAC上，成功地将He、C、Ne等重离子加速到100 MeV/U。我们设计了由高磁导率磁性合金(MA)电感材料组成的“阻抗调谐器”，以消除纵向的空间电荷阻抗。它被安装在KEK PS主环中。我们观察到了相干四极振荡的频移，并推断出非相干同步辐射振荡的频移。总无功阻抗可以用位移和束流强度之间的系数来估计。通过阻抗调谐器将测量的阻抗从-j2475OMEGA降低到-j1182OMEGA。论证了阻抗调谐器对空间电荷阻抗的补偿作用。

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.