Development of Superconducting Cavities for Future Synchrotron Light Sources and Electron-Positron Colliders

未来同步加速器光源和正负电子对撞机超导腔的开发

• 批准号: 12440074
• 负责人: FURUYA Takaaki
• 金额: $ 9.6万
• 依托单位: KEK, High Energy Accelerator Research Organization
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440074/
• 关键词: superconducting; cavities; KEKB; collider; HOM; ferrite; coupler; synchrotron; 蓄積電流; 電流値; 高周波高電力試験装置; Bファクトリー加速器; 超伝導破壊; ビーム不安定性

Superconducting (SC) RF cavities provide a high accelerating field gradientin constant wave operation, which is several times higher than that achieved by conventional normal conducting (NC) cavities. This superior performance has a clear advantage in the application to high intensity electron (positron) storage rings, where the less number of cavities is desired so as to reduce the total higher order mode (HOM) impedance and to avoid beam instabilities.KEKB is an electron and positron collider for B meson physics, in which extreme high intensity beams of 1.1 A and 2.6 A are accumulated and collided each other to achieve a luminosity of 10^<34> cm^<-2>S^<-1>. To keep such a high intensity beam, new SC cavities based on a HOM damping scheme using ferrite absorbers have been developed and commissioned in the electron ring (HER). The mission of this research projefct is to make clear the performance of the SC cavities and also to establish the operation technology of SC cavities in high c … More urrent use.The important results will be summarized as follows.1) During this research project, the beam intensity has gradually been improved and finally reached the full current of 1.1 A. This result demonstrates that the new SC cavity with ferrite absorbers is quite useful as an RF cavity for high intensity storage accelerators in various fields.2) The cavity has a strong interaction with the beam in such a high intensity operation. As a result, just a small movement of the beam disturbs the cavity voltage and causes a trip of the cavities. Tfte analysis study of all the trips showed clearly that 90 % of die trips were caused by the instabilities and the loss of the beam. On the other hand, the SC cavity itself was quite stable, and tripped once or twice per month that was caused by discharging.3) The study of an input coupler demonstrated that multipacting discharging happened on the wall of outer conductor, which was in agreement with a simulation result under a DC bias voltage between the conductors.4) RF power absorbed by ferrite dampers has been measured and analyzed under various beam intensity and bunch configurations. The results show that the power caused by wide-range HOMs is dominant, and that the ferrite dampers sufficiently damps the Q of all the HOMs in th cavity so as not to introduce the beam instabilities. Because of an operation mode of higher bunch current, absorbed power has already reached two times higher than the design level.Besides these results, the study of a cavity shape of 500MHz gave a solution of the SC cavity in synchrotron light source rings. As a result this research project has made clear the feasibility of SC cavities in high current use. Less

超导（SC）射频腔在恒定波工作时具有很高的加速场梯度，比常规的正常导体（NC）腔的加速场梯度高几倍。这种上级性能在高强度电子束的应用中具有明显的优势（正电子）存储环，其中期望较少数量的腔，以便减小总的高阶模（HOM）阻抗并避免束不稳定性。KEKB是用于B介子物理的电子和正电子对撞机，其中1.1A和2.6A的极高强度光束被累积并且彼此碰撞以实现10^<34>cm^<-2>S^的光度<-1>。为了保持这样的高强度束，已经开发了基于使用铁氧体吸收体的HOM阻尼方案的新的SC腔，并在电子环（HER）中进行了调试。本课题的使命是弄清超导腔的性能，建立超导腔在高功率下的运行技术 ...更多信息 主要研究结果如下：1）在本课题的研究过程中，束流强度逐步提高，最终达到了1.1A的满电流。这一结果表明，这种新型的超导铁氧体吸收腔作为高强度存储加速器的射频腔在各个领域都是非常有用的。2）在这样的高强度操作中，这种腔与束流有很强的相互作用。结果，仅仅是电子束的微小移动就会干扰腔电压并导致腔跳闸。对所有跳闸的Tfte分析研究清楚地表明，90%的芯片跳闸是由束流的不稳定和损失引起的。另一方面，SC腔本身相当稳定，每个月都有一到两次放电引起的跳闸。3）对输入耦合器的研究表明，外导体壁上发生了二次放电，这与在导体之间的DC偏置电压下的模拟结果一致。测量和分析了不同束流强度和束团结构下铁氧体阻尼器吸收的射频功率。结果表明，宽范围的HOM引起的功率占主导地位，铁氧体阻尼器充分阻尼了腔中所有HOM的Q，从而不会引入光束不稳定性。由于采用了高束流工作模式，吸收功率已达到设计水平的2倍以上，此外，对500MHz腔形的研究给出了同步辐射光源环SC腔的解决方案。因此，本研究项目明确了SC腔在大电流使用中的可行性。少

项目成果

K.Akai et al.: "Commissioning of KEKB"Nuclear instruments and Methods in Physics Research. A499. 191-227 (2003)

K.Akai 等人：“KEKB 的调试”物理研究中的核仪器和方法。

T.Furuya et al.: "Operation Status of the KEKB Superconducting Damped Cavity"Proc. of the 10^<th> Workshop on RF Superconductivity. 599-601 (2001)

T.Furuya 等：“KEKB 超导阻尼腔的运行状态”Proc。

Y.Kijima et al.: "Conditioning of Input Couoplers for KEKB Superconducting Cavities"Proc.of the 10^<th> Workshop on RF Supecccmductivity. 505-569 (2003)

Y.Kijima 等人：“KEKB 超导腔输入耦合器的调节”第 1​​0 届 RF 超导性研讨会论文集。

K.Akai et al.: "RF System for the KEK B-Factory"Nuclear Instruments and Methods in Physics Research. A499. 45-65 (2003)

K.Akai 等人：“KEK B 工厂的射频系统”物理研究中的核仪器和方法。

Y.Kijima et al.: "Conditioning of Input Couoplers for KEKB Superconducting Cavities"Proc. of the 10^<th> Workshop on RF Superconductivity. 505-569 (2001)

Y.Kijima 等人：“KEKB 超导腔输入耦合器的调节”Proc。