论文标题

FCC-EE对撞机中电子云效应的缓解

Mitigation of Electron Cloud Effects in the FCC-ee Collider

论文作者

Yaman, Fatih, Iadarola, Giovanni, Kersevan, Roberto, Ogur, Salim, Ohmi, Kazuhito, Zimmermann, Frank, Zobov, Mikhail

论文摘要

由于光发射和次级发射,在光束真空室内形成的电子云可能会限制加速器性能。具体而言,如果中央电子密度超过一定的阈值,则电子云可以通过头尾型单束式不稳定性吹出正电子束的垂直发射率,可以通过分析进行估计。使用PyeCloud和VSIM代码,我们对Electron-Cloud为主弧和FCC-EE撞机的阻尼环进行了详细的模拟,以确定实现和维护设计发射率所需的有效光发射率和次要发射率。为此,我们在梁管的中心介绍了模拟的电子密度,以进行各种束间距,二次发射屈服和光发射参数,在阻尼环和对撞机正电子环的弧中。为了进一步了解潜在的动力学,将云电子的空间和能量分布作为时间的函数说明。此外,我们比较了两个不同的二级发射模型(“ Furman-Pivi”和“ Ecloud”)获得的结果,从而表明此类型的研究中固有的不确定性,而没有任何原型真空室尚未可用。我们还指出了两种二次发射模型产生相似密度值的情况。最后,基于我们针对两个不同设计变体的仿真结果,我们得出结论,FCC-EE的新参数基线将促进电子云的缓解。

Electron clouds forming inside the beam vacuum chamber due to photoemission and secondary emission may limit the accelerator performance. Specifically, the electron clouds can blow up the vertical emittance of a positron beam, through a head-tail-type single-bunch instability, if the central electron density exceeds a certain threshold value, that can be estimated analytically. Using the codes PyECLOUD and VSim, we carried out detailed simulations of the electron-cloud build up for the main arcs and the damping ring of the FCC-ee collider, in order to identify the effective photoemission rate and secondary emission yield required for achieving and maintaining the design emittance. To this end, we present the simulated electron density at the centre of the beam pipe for various bunch spacings, secondary emission yields, and photoemission parameters, in the damping ring and in the arcs of the collider positron ring. To gain further insight into the underlying dynamics, the obtained spatial and energy distributions of the cloud electrons are illustrated as a function of time. In addition, we compare results obtained for two different secondary emission models ("Furman-Pivi" and "ECLOUD"), thereby indicating the uncertainty inherent in this type of study, without any prototype vacuum chambers yet available. We also point out a few situations where the two secondary-emission models yield similar density values. Finally, based on our simulation results for two different design variants, we conclude that the new parameter baseline of the FCC-ee will facilitate electron-cloud mitigation.

扫码加入交流群

加入微信交流群

微信交流群二维码

扫码加入学术交流群,获取更多资源