Analytic Modeling, Simulation and Interpretation of Broadband Beam Coupling Impedance Bench Measurements

In the first part of the paper a generalized theoretical approach towards beam coupling impedances and stretched-wire measurements is introduced. Applied to a circular symmetric setup, this approach allows to estimate the systematic measurement error due to the presence of the wire. Further, the interaction of the beam or the TEM wave, respectively, with dispersive material such as ferrite is discussed. The dependence of the obtained impedances on the relativistic velocity $\beta$ is investigated and found as material property dependent. The conversion formulas for the TEM scattering parameters from measurements to impedances are compared with each other and the analytical impedance solution. In the second part of the paper the measurements are compared to numerical simulations of wakefields and scattering parameters. In practice, the measurements have been performed for the circularly symmetric example setup. The optimization of the measurement process is discussed. The paper concludes with a summary of systematic and statistic error sources for impedance bench measurements and their diminishment strategy

Laser Cooling of Intense Relativistic Ion Beams

Doppler laser cooling is a technique to reduce the longitudinal momentum spread of an ion beam in a circular accelerator. In the past, the principle was investigated and verified on non-relativistic ion beams. Within the FAIR project, laser cooling will be applied to high intensity and relativistic ion beams for the first time. Laser cooling results in a further increase of the longitudinal ion density and creates exotic longitudinal phase space distributions. In order to ensure stable operation and optimize the cooling process, this dissertation numerically investigates the particle dynamics and the interplay of the laser force and high intensity effects. This work describes the ion-photon interaction and derives the laser force on ions at relativistic energies. The force is calculated for continuous wave and pulsed laser excitations. The pulsed laser excitation results in a broadband force, which interacts with all ions simultaneously, whereas the width of the continuous wave laser force is typically three to four orders of magnitude smaller. In order to interact with all ions, the position of the continuous wave laser force is scanned during the cooling process. The particle dynamics during the cooling processes for both laser forces are analyzed and compared. The impact of heating effects during the laser cooling process is also investigated. Scattering events within the beams limit the maximum ion intensity for the cooling for both a continuous wave or a pulsed laser system. In addition, numerical simulations show two instabilities, that arise during the scan of the continuous wave laser force and are triggered by space charge. This work describes the development of the instabilities and the impact on the laser cooling process. Analytical expressions for the threshold of instabilities and maximum ion intensities are given. The scaling of the cooling process and intensity limitations with beam energy is discussed in order to evaluate the prospects of laser cooling experiments at relativistic energies. The work concludes with the comparison of the cooling process of non-relativistic carbon ions and relativistic titanium ions. The comparison emphasizes the main challenges for laser cooling experiments in the SIS100 synchrotron at FAIR

Cooling rates and intensity limitations for laser-cooled ions at relativistic energies

The ability of laser cooling for relativistic ion beams is investigated. For this purpose, the excitation of relativistic ions with a continuous wave and a pulsed laser is analyzed, utilizing the optical Bloch equations. The laser cooling force is derived in detail and its scaling with the relativistic factor $\gamma$ is discussed. The cooling processes with a continuous wave and a pulsed laser system are investigated. Optimized cooling scenarios and times are obtained in order to determine the required properties of the laser and the ion beam for the planed experiments. The impact of beam intensity effects, like intrabeam scattering and space charge are analyzed. Predictions from simplified models are compared to particle-in-cell simulations and are found to be in good agreement. Finally two realistic example cases of Carbon ions in the ESR and relativistic Titanium ions in SIS100 are compared in order to discuss prospects for future laser cooling experiments

重离子储存环CSRe上激光冷却相对论能量类锂 ~(12)C~(3+)离子束的实验研究进展

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">激光冷却储存环中相对论能量的重离子束是最有希望得到高相空间密度离子束、实现离子束相变并且获得有序束和晶化束的一种方法. 相对于已经比较成熟的随机冷却和电子冷却技术, 储存环上重离子束的激光冷却具有冷却速度快, 冷却作用力强的特点, 可以将离子束冷却到极低温度(mK), 在激光冷却的同时还可以开展高电荷态离子的精细激光谱学实验. 本文介绍了中国科学院近代物理研究所大科学装置重离子冷却储存环CSRe上开展激光冷却重离子束的实验原理和实验方法, 给出了在CSRe上首次激光冷却能量为122 MeV/u的类锂~(12)C~(3+)离子束测试性实验结果, 并且展望了在未来大型加速器HIAF上开展类锂类钠高电荷态离子的激光冷却和精细激光谱学实验.</span><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Laser cooling of relativistic heavy ion beams at storage rings is one of the most promising techniques to reach high phase-space densities and achieve phase transition, ordered beam even crystalline beam. Compared with the established cooling schemes at storage rings, such as stochastic cooling and electron cooling, laser cooling has many advantages such as fast-cooling, ultra-strong cooling force and providing an ultra-low temperature (mK) ion beams. In addition, the precision laser spectroscopy of the highly charged ions can be performed by using the laser-cooled ion beams during the laser cooling experiments. We introduce the experimental principal and methods of laser cooling of relativistic ion beams at the experimental cooler storage ring of the CSRe at the Institute of Modern Phyics, Chinese Academy of Sciences. The first experimental results from a beam time aiming for laser cooling of 122 MeV/u Li-like ~(12)C~(3+) at the CSRe with a pulsed laser are presented, and laser cooling and precision laser spectroscopy of relativistic Li-like and Na-like highly charged ions at the future large facility HIAF and FAIR are outlined.</span