Beam halo dynamics and control with hollow electron beams
G. Stancari, G. Annala, A. Didenko, T. R. Johnson, I. A. Morozov, V. Previtali, G. Saewert, V. Shiltsev, D. Still, A. Valishev, L. G. Vorobiev, D. Shatilov, R. W. Assmann, R. Bruce, S. Redaelli, A. Rossi, B. Salvachua Ferrando, G. Valentino
本文综述了准直器扫描束晕扩散动力学的实验测量。本文讨论了用空心电子束准直器控制晕的概念，在Tevatron上的演示，以及它在LHC上的可能应用。
Experimental measurements of beam halo diffusion dynamics with collimator scans are reviewed. The concept of halo control with a hollow electron beam collimator, its demonstration at the Tevatron, and its possible applications at the LHC are discussed.
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Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider
空心电子束准直是一种控制强流强子束晕的技术。它基于由强轴向磁场引导的电子束（可能是脉冲的或强度调制的），该磁场在环的短部分中与循环束重叠。这个概念在费米实验室的Tevatron对撞机上进行了实验测试，使用了一个安装在Tevatron电子透镜中的空心电子枪。在美国LHC加速器研究计划（LARP）和欧洲FP7 HiLumi LHC设计研究中，我们提出了将这种技术应用于CERN大型强子对撞机的概念设计。一个原型空心电子枪的大型强子对撞机建造和测试。空心电子束准直器的预期性能是基于Tevatron实验和数值跟踪模拟。晕去除率和增强晕扩散率估计作为一个函数的光束和晶格参数。检查质子束芯寿命和发射度增长率，以确保抑制不希望的影响。硬件规格基于Tevatron设备和LHC机器中的初步工程集成研究。还概述了所需的资源和可能的时间轴，并简要讨论了替代性的光晕去除方案和电子透镜的其他可能用途，以提高LHC的性能。
Hollow Electron Beam Collimator: R&D Status Report
磁约束空心电子束的控制晕消除在高能对撞机，如Tevatron或LHC可能会扩展传统的准直系统超出可容忍的材料损伤所施加的强度限制。它们还可以通过抑制由于光束抖动引起的损耗尖峰和通过增加捕获效率来改善准直性能。设计并制造了一种空心电子枪。它的性能和稳定性在费米实验室测试台上进行了测量。该枪将安装在现有的Tevatron电子透镜中，用于空心束准直器概念的初步测试，解决重叠质子和电子束的对准和不稳定性等关键问题。
Development of hollow electron beams for proton and ion collimation
磁约束空心电子束的控制晕消除在高能对撞机，如Tevatron或LHC可能会扩展传统的准直系统超出可容忍的材料损伤所施加的强度限制。它们还可以通过抑制由于光束抖动引起的损耗尖峰和通过增加捕获效率来改善准直性能。设计并制造了一种空心电子枪。它的性能和稳定性在费米实验室测试台上进行了测量。该枪将安装在现有的Tevatron电子透镜中，用于空心束准直器概念的初步测试，解决重叠质子和电子束的对准和不稳定性等关键问题。
Collimation with hollow electron beams
提出了一种新的控制强流高能束晕在储存环和对撞机中的消除概念。它是基于循环束的相互作用与5千电子伏，磁约束，脉冲空心电子束在一个2米长的部分环。电子包围循环束流，横向踢晕粒子并使束流核心不受干扰。通过充当可调谐扩散增强器而不是硬孔径限制，中空电子束准直器将常规准直系统扩展到超出由可容忍损耗施加的强度限制。这个概念在费米实验室的Tevatron质子-反质子对撞机上进行了实验测试。本文介绍了980-GeV反质子准直的初步结果。
The Side-Effects of the Space Charge Field Introduced by Hollow Electron Beam in the Electron Cooler of CSRm
电子冷却器用于提高同步加速器中的束流质量，但它也引入了非线性电磁场，这会引起调谐漂移、调谐扩展，并可能驱动共振，导致束流损失。本文研究了空心电子注的非线性电磁场引起的频移和频散，分析了非线性电磁场的共振驱动项。并与固体电子束进行了比较。使用表1中给出的参数，对储存在CSRm中的能量为1.272 MeV的$^{238}U^{32+}$离子进行了计算。结果表明，在这种情况下，空心电子束产生的非线性场不会导致严重的共振。
Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the HL-LHC. In order to further increase the diffusion rates for a fast halo removal as e.g. desired before the squeeze, the electron lens (e-lens) can be operated in pulsed mode. In case of profile imperfections in the electron beam the pulsing of the e-lens induces noise on the proton beam which can, depending on the frequency content and strength, lead to emittance growth. In order to study the sensitivity to the pulsing pattern and the amplitude, a beam study (machine developme…
We present the results of numerical simulations and experimental studies about the effects of resonant and random excitations on proton losses, emittances, and beam distributions in the Large Hadron Collider (LHC). In addition to shedding light on complex nonlinear effects, these studies are applied to the design of hollow electron lenses (HEL) for active beam halo control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable amount of energy will be stored in the beam tails. To control and clean the beam halo, the installation of two hollow electron lenses, one per beam, is b…
Ultra-relativistic hollow electron beams can drive plasma wakefields ($\sim$ GV/m) suitable for positron acceleration. Stable propagation of hollow electron beams for long distances in plasmas is required to accelerate positrons to high energies by these plasma wakefields. In this work, we show by quasi-static kinetic simulations using the code WAKE that an ultra-relativistic azimuthally-symmetric hollow electron beam propagates in a plasma by developing fish-bone like structure and shifting its bulk, differentially along its length (rear part fastest), towards its axis due to the decrease in …
Single-shot Transverse Wakefield Mapping with a Hollow Electron Beam
本文提出一种基于空心电子束的单发横向尾场测量技术，通过探针横向畸变直接测量驱动束团产生的尾场分布，为抑制束流破裂不稳定性提供诊断手段。
Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first…
We propose a novel positron beam loading regime in a hollow plasma channel that can efficiently accelerate $e^+$ beam with high gradient and narrow energy spread. In this regime, the $e^+$ beam coincides with the drive $e^-$ beam in time and space and their net current distribution determines the plasma wakefields. By precisely shaping the beam current profile and loading phase according to explicit expressions, three-dimensional Particle-in-Cell (PIC) simulations show that the acceleration for $e^+$ beam of $\sim$nC charge with $\sim$GV/m gradient, $\lesssim$0.5% induced energy spread and $\s…
Calculation of the transverse kicks generated by the bends of a hollow electron lens
电子透镜是脉冲的、磁约束的电子束，其电流密度分布被成形以获得对高能加速器中的循环束的期望效果。它们被用于费米实验室的Tevatron对撞机，用于异常间隙清除，束-束补偿和晕刮。目前，布鲁克海文国家实验室的相对论重离子对撞机正在实施一种基于电子透镜的束-束补偿方案。这项工作是在大型强子对撞机的空心电子束刮刀的概念设计的支持。它也适用于在费米实验室的可积光学测试加速器的电子透镜的非线性可积光学的实施。我们考虑的电子束的轴向不对称性所造成的弯曲，用于注入电子到相互作用区域，并提取它们。电子宏观粒子的分布被沉积在封闭在导电管中的离散网格上。静电势和电场的计算使用数值泊松求解器。通过在直线轨迹上积分电场来估计循环射束所经历的反冲。这些踢还提供了插值分析辛地图的形式，用于数值跟踪模拟，这是需要估计的电子透镜的缺陷对质子寿命，发射度的增长，和动态孔径的影响。我们概述了一个一般的程序来计算的横向质子踢的大小，然后可以概括，如果需要的话，包括进一步的改进，如电子束的空间电荷演化，由电子流产生的磁场，和纵向质子动力学。
Acceleration of a Positron Bunch in a Hollow Channel Plasma
该研究在空芯通道等离子体中实验验证了正电子束驱动的尾场加速，实现了70 MV/m的加速梯度，为对称加速正负电子束提供了概念验证。
Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the …
New methods of particle collimation in colliders
准直系统是任何高功率加速器设计的重要组成部分。其功能包括保护组件免受意外和故意的能量沉积，减少背景和光束诊断。基于散射体和吸收体的传统多级系统提供鲁棒的屏蔽和有效的损耗收集。两个互补的概念已被提出来解决一些传统系统的局限性：沟道和弯曲晶体中的体积反射和空心电子束准直。本文的主要重点是空心电子束准直器，一个新的概念的基础上的相互作用的循环束与5千电子伏，磁约束，脉冲空心电子束在一个2米长的部分环。电子包围循环束流，横向踢晕粒子并使束流核心不受干扰。通过充当可调谐扩散增强器而不是硬孔径限制，中空电子束准直器将常规准直系统扩展到超出由可容忍损耗施加的强度限制。这个概念在费米实验室的Tevatron质子-反质子对撞机上进行了实验测试。本文介绍了980 GeV反质子准直的结果，并对未来作了展望。
Plasma wakefield acceleration in the blowout regime is particularly promising for high-energy acceleration of electron beams because of its potential to simultaneously provide large acceleration gradients and high energy transfer efficiency while maintaining excellent beam quality. However, no equivalent regime for positron acceleration in plasma wakes has been discovered to-date. We show that after a short propagation distance, an asymmetric electron beam drives a stable wakefield in a hollow plasma channel that can be both accelerating and focusing for a positron beam. A high charge positron…
Formation and stability of a hollow electron beam in the presence of a plasma wake field driven by an ultra-short electron bunch
对等离子体尾流场作用下电子注在等离子体中的时空演化进行了数值研究。后者是由超短相对论轴对称飞秒电子束团驱动的。我们首先推导出一个新的泊松方程的尾流电位的驱动项是超短聚束密度，适当地考虑到之间的相互作用的锐度和高能量的聚束。然后，我们表明，形成一个通道纵向，通过外部注入的光束，同时经历的聚束驱动的等离子体尾场的影响，在热波模型的上下文中。通道的形成似乎是光束3D演化的最后阶段。这涉及在纵轴周围出现小细丝和气泡。气泡聚结形成相对稳定的轴对称中空梁结构。
A positron-beam interacting with the plasma electrons drives radial suck-in, in contrast to an electron-beam driven blow-out in the over-dense regime, $n_b>n_0$. In a homogeneous plasma, the electrons are radially sucked-in from all the different radii. The electrons collapsing from different radii do not simultaneously compress on-axis driving weak fields. A hollow-channel allows electrons from its channel-radius to collapse simultaneously exciting coherent fields. We analyze the optimal channel radius. Additionally, the low ion density in the hollow allows a larger region with focusing phase…
Hollow plasma channels are attractive for lepton acceleration because they provide intrinsic emittance preservation regimes. However, beam breakup instabilities dominate the dynamics. Here, we show that thin, warm hollow channels can sustain large-amplitude plasma waves ready for high-quality positron acceleration. We verify that the combination of warm electrons and thin hollow channel enables positron focusing structures. Such focusing wakefields unlock beam breakup damping mechanisms. We demonstrate that such channels emerge self-consistently during the long-term plasma dynamics in the blow…
Beam Halo Formation via Longitudinal-Transverse Coupling in Continuous-Wave Photoinjectors
本文针对连续波光注入器中束晕形成问题，提出并实验验证了一种由纵向-横向耦合驱动的三步机制，并通过聚束器压缩调节实现束晕抑制，为高重复频率FEL稳定运行提供支持。
Positron acceleration in a hollow plasma channel up to TeV regime
我们提出了一种基于等离子体的高能轻子加速器，其中在束轴附近形成弱聚焦等离子体结构。该结构保持了加速束的发射度，并产生低辐射损失。此外，该结构允许在驱动器耗尽阶段显著降低见证能量扩展。
Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned…
Plasma-based electron and positron wakefield acceleration has made great strides in the past decade. However one major challenge for its applications to coherent light sources and colliders is the relatively large energy spread of the accelerated beams, currently at a few percent level. This energy spread is usually correlated with particle position in the beam arising from the longitudinal chirp of the wakefield amplitude. Therefore a dechirper is highly desirable for reducing this spread down to $\sim0.1\%$ level, while at the same time for maintaining the emittance of the accelerated beam. …
Analysis of a hadron beam in five-dimensional phase space
本文在散裂中子源束流测试装置上对五维相空间强子束流进行高分辨率测量，开发非平面切片等分析可视化技术，揭示低维投影无法充分表征高维相空间分布。
Laser-Plasma Ion Beam Booster Based on Hollow-Channel Magnetic Vortex Acceleration
针对激光驱动离子加速的离子最大能量不足问题，提出保品质级联加速方案，经三维PIC模拟验证其鲁棒性且可俘获高电荷质子团，适配现有及近期激光装置。
Scheme for proton-driven plasma-wakefield acceleration of positively charged particles in a hollow plasma channel
提出了一种在等离子体尾场加速器中加速带正电粒子的新方案。如果质子驱动束在中空等离子体通道中传播，并且束半径是通道宽度的量级，则驱动器的空间电荷力导致通道壁处的电荷分离，这有助于聚焦沿束轴传播的带正电的见证聚束。在通道中，带正电荷的粒子的加速桶比均匀等离子体的井喷状态大得多，并且长距离的稳定加速是可能的。此外，可以通过改变通道的半径来调整见证物相对于波的相位，以确保加速度是最佳的。二维模拟表明，对于未来可能出现的质子驱动器，带正电的粒子可以稳定地加速超过1公里，平均加速梯度为1.3 GeV/m。
Generation and Acceleration of Isolated-Attosecond Electron Bunch in a Hollow-Channel Plasma Wakefield
提出利用电子束驱动空心通道等离子体靶同时产生并加速十GeV级孤立阿秒电子束的新方案，通过辐射尾场注入并加速等离子体电子，获得高电荷量、高能量、高稳定性的电子束，适用于超快与高能物理。
Applications of electron lenses: scraping of high-power beams, beam-beam compensation, and nonlinear optics
电子透镜是脉冲的、磁约束的电子束，其电流密度分布被成形以在循环束上获得期望的效果。费米实验室的Tevatron对撞机使用了电子透镜，用于逐束补偿远距离束-束调谐偏移，用于去除中止间隙中未捕获的粒子，用于正面束-束补偿的初步实验，以及用于演示空心电子束的晕刮。布鲁克海文国家实验室（BNL）的相对论重离子对撞机（RHIC）正在调试用于束-束补偿的电子透镜。对空心电子束准直和晕控制进行了研究，作为补充欧洲核子研究中心大型强子对撞机升级准直系统的一个备选方案;最近完成了一项概念设计。由于它们的电荷和质子束附近没有材料，电子透镜也可以提供一种替代导线的方法，用于LHC亮度升级方案中具有小交叉角的长距离束-束补偿。在费米实验室，我们计划在可积光学测试加速器（IOTA，一个40米的150 MeV电子环）中安装一个电子透镜，作为非线性可积光学的原理验证实现之一，以实现大的调谐扩展和更稳定的光束，而不会损失动态孔径。
Ion extraction from DECRIS-PM source is simulated by using initial distributions of ions at the extraction aperture obtained with NAM-ECRIS code. Three-dimensional calculations of plasma emissive surface are done and ions are traced in the extraction region. The ion beam profiles show strong aberrations due to shape of plasma meniscus; hollow beam features are reproduced, as well as changes in profiles for different focusing conditions.
In circular colliders, as well as in damping rings and synchrotron radiation light sources, beam halo is one of the critical issues limiting the performance as well as potentially causing component damage and activation. It is imperative to clearly understand the mechanisms that lead to halo formation and to test the available theoretical models. Elastic beam-gas scattering can drive particles to large oscillation amplitudes and be a potential source of beam halo. In this paper, numerical estimation and Monte Carlo simulations of this process at the ATF of KEK are presented. Experimental measu…
A Hollow Electron Lens (HEL) has been proposed in order to improve performance of halo control and collimation in the Large Hadron Collider in view of its High Luminosity upgrade (HL-LHC). The concept is based on a beam of electrons that travels around the protons for a few meters. The electron beam is produced by a cathode and then guided by a strong magnetic field generated by a set of superconducting solenoids. The first step of the design is the definition of the magnetic fields that drive the electron trajectories. The estimation of such trajectories by means of a dedicated MATLAB tool is…
Beam halo is one of the crucial issues limiting the machine performance and causing radioactivation in high-intensity accelerators. A clear picture of beam-halo formation is of great importance for successful suppression of the undesired beam loss. We present numerical and experimental studies of transverse and longitudinal halos in the KEK Accelerator Test Facility. The fair accordance between predictions and observations in various conditions indicates that the Touschek scattering is the dominant mechanism forming the horizontal and momentum halos.
The Beam Halo Experiment at the LEDA Facility
由于在强质子束中产生晕粒子的潜在不利影响，因此必须清楚地了解当前和拟议的高强度直线加速器可能导致晕形成的机制。为此，已经开发了一个理论模型，该模型表明，在强空间电荷力和线性传输通道中的周期性聚焦的联合影响下，质子可以被踢到晕轨道中。然而，还没有实验测量质子束中的束晕。在本文中，我们报告的进展，努力进行一项实验，以测量束晕使用现有的高强度质子束的LEDA设施。一个线性传输通道已组装与适当的诊断用于测量作为光束参数的函数的束晕中的预期的小光束分量。该实验是基于使用一个阵列的高动态范围线和光束刮刀，以确定沿运输通道的晕和核心配置文件。将介绍实验设计的详细信息和预期的晕圈测量特性。
Isolated attosecond free-electron laser based on a sub-cycle driver from hollow capillary fibers
提出利用中空毛细管光纤产生的中红外亚周期激光调制电子束，生成准孤立电流峰，从而产生高信噪比、高强度的孤立阿秒软X射线自由电子激光。
Halo distribution is a key topic for background study. This paper has developed an analytical method to give an estimation of ATF beam halo distribution. The equilibrium particle distribution of the beam tail in the ATF damping ring is calculated analytically with different emittance and different vacuum degree. The analytical results agree the measurements very well. This is a general method which can be applied to any electron rings.
An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensi…
Stability and Halo Formation in Axisymmetric Intense Beams
采用粒子模拟方法，分析了高强度轴对称二维光束在均匀聚焦通道中的光束稳定性和束晕形成。探讨了均匀（KV）分布的粒子横向相空间密度，以及更现实的（特别是，水袋分布），以确定稳定性限制和晕参数的调谐凹陷失配空间。数值结果表明，与晕形成的分析模型（R.L.）的预测一致。Gluckstern，Phys.Rev.Letters，73（1994）1247）。
Halo Coupling and Cleaning by a Space Charge Resonance in High Intensity Beams
结果表明，强流束的空间电荷赝八极子驱动的差共振不仅耦合束芯发射度，还导致束晕中的发射度交换，这与强流加速器中的束流损失有关.关于直线加速器，“主共振”kz/kxy =1（对应于圆形加速器中的蒙塔古共振2 Qx-2 Qy =0）可导致平面之间的晕圈的这种耦合和转移。即使芯发射度（rms）完全相等或几乎相等，也可能发生横向晕耦合到纵向平面（反之亦然）。这个晕轮论证证明了在直线加速器设计中的额外谨慎，包括考虑避免均分设计。然而，与此同时，该机制也可以通过将晕圈从纵向平面耦合到横向平面（其中局部刮擦是可访问的）中而有资格作为主动动态晕圈清洁方案。我们提出了半解析发射度耦合率，并表明，以前开发的直线加速器的核心稳定性图表可以扩展-使用的纵向横向晕发射度比-以表明其他地区的晕耦合可能是重要的。
In order to study the background status in the ATF2 beam line and the interaction point (IP), this paper developed an analytical method to give the estimation of ATF beam halo distribution based on K. Hirata and K. Yokoya's theory. The equilibrium particle distribution of beam tail in ATF damping ring, when each electron is being affected by, in addition to the synchrotron radiation damping effects, several stochastic processes, such as beam-gas scattring, beam-gas bremsstrahlung and intra-beam scattering, was presented. This method is common and can be applied on other electron rings.
Control of focusing forces and emittances in plasma-based accelerators using near-hollow plasma channels
提出了一种近中空等离子体通道，其中通道中的等离子体密度远小于壁中的等离子体密度，以提供对等离子体加速器中的聚焦力和加速力的独立控制。在这种几何形状中，通道中的低密度有助于聚焦力，而加速场由通道壁中的高密度决定。该通道还为用于尾流场激发的强激光脉冲提供引导。在某些情况下，电子束和正电子束都可以以近似对称的方式加速和聚焦。近空心等离子体通道可以有效地抑制由于库仑散射引起的发射度增长，适用于高能物理应用。
Beam Halo Imaging with a Digital Optical Mask
束晕是影响强流加速器性能的重要因素。它会导致束流控制困难、发射度增长、粒子损失，甚至损坏加速器。因此，必须了解晕形成的机制及其动力学，以控制和尽量减少其影响。晕分布的实验测量是这类研究的重要工具。在本文中，我们提出了一种新的自适应掩模的方法，我们已经开发的图像束晕，它使用数字微镜阵列器件（DMD）。这种方法已经在实验室中使用激光和白光光源，并与马里兰大学电子环（UMER）产生的实际光束进行了彻底的研究。用这种新方法已经证明了~10（5）的高动态范围，最近的研究表明，对于更强的光束，可以超过这个数字至少一个数量级。该方法灵活，易于设置，可用于任何加速器或光源。我们提出了我们的测量结果的性能的方法和图像的光束晕在各种实验条件下产生的。
The substantial angular divergence of electron beams produced by direct laser acceleration is often considered as an inherent negative feature of the mechanism. The divergence however arises primarily because the standard approach relies on transverse electron oscillations and their interplay with the transverse electric fields of the laser pulse. We propose a conceptually different approach to direct laser acceleration that leverages longitudinal laser electric fields that are present in a tightly focused laser beam. A structured hollow-core target is used to enhance the longitudinal fields a…
Fluctuations Do Matter: Large Noise-Enhanced Halos in Charged-Particle Beams
束晕的形成通常用粒子核模型来描述，其中振荡核的空间电荷场将粒子驱动到大振幅。该模型涉及参数共振，并预测了一个硬上限的晕粒子的轨道振幅。我们表明，由于空间电荷波动和/或机器缺陷的有色噪声的存在下，可以喷射粒子到更大的幅度比将单独从参数共振推断。
In particle accelerators, particle losses to surrounding components must be minimized. These particles usually have been driven into an undesired "halo" outside the desired distribution before being lost. The processes involved and physical identification of such halo is an intense research topic especially when the nonlinear space charge effect is taken into account. In order to present a method, firmly based on the physics of the transient beam state, for determining when a particle may be defined as being in a halo, the particular example of an initially rms matched beam injected into a res…
Measurements of the effect of collisions on transverse beam halo diffusion in the Tevatron and in the LHC
在粒子对撞机中，束-束力和碰撞光学对束流寿命、动态孔径和束晕的形成有重要影响。在机器的设计和操作阶段进行了大量的分析和数值模拟，以量化这些影响，但实验数据很少。小步长准直器扫描技术应用于费米实验室Tevatron对撞机和欧洲核子研究中心（CERN）大型强子对撞机，研究了碰撞对横向束晕动力学的影响。我们描述的技术，并提出了一个总结的第一个结果的依赖性的晕扩散系数在Tevatron和LHC的电子感应加速器振幅。
Circular particle accelerators at the energy frontier are based on superconducting magnets that are extremely sensitive to beam losses as these might induce quenches, i.e.\ transitions to the normal-conducting state. Furthermore, the energy stored in the circulating beam is so large that hardware integrity is put in serious danger, and machine protection becomes essential for reaching the nominal accelerator performance. In this challenging context, the beam halo becomes a potential source of performance limitations and its dynamics needs to be understood in detail to assess whether it could b…
Tevatron Beam Halo Collimation System: Design, Operational Experience and New Methods
质子束和反质子束在Tevatron对撞机中的准直是为了保护CDF和D0探测器并使其本底率最小化，保持超导磁体的辐照处于控制之下，保持长期运行的可靠性，并减少束流感应辐射对环境的影响。本文简要介绍了对撞机准直系统的设计、实际实现和性能，控制横向和纵向束晕的方法，以及在Tevatron上测试的两种新的准直技术。
Measurements of beam halo diffusion and population density in the Tevatron and in the Large Hadron Collider
晕动力学影响全球加速器的性能：束流寿命，发射度增长，动态孔径和准直效率。光晕监测和控制对于高功率机器的运行也至关重要。例如，在LHC的高亮度升级中，储存在束尾中的能量可能达到几兆焦耳。快速损耗会导致超导磁体失超、磁体损坏甚至准直器变形。需要测量束晕并以可控的速率去除它。在Tevatron和LHC中，通过观察在不同的实验条件下小的向内或向外的准直器步骤之后的损失的时间演变，用准直器扫描测量晕粒子数密度和扩散率：用单束和碰撞，并且在Tevatron的情况下，用空心电子透镜作用于聚束的子集。大型强子对撞机恢复运行后，计划将测量的扩散率与已知的横向阻尼器激励强度进行比较。本文还简要讨论了非破坏性晕粒子数密度测量的新建议。
An experimentally robust technique for halo measurement using the IPM at the Fermilab Booster
我们提出了一个模型无关的量，$L/G$，来表征非高斯尾巴在费米实验室助推器离子轮廓监测器观察到的光束轮廓。这个量可以被认为是助推器中束晕的量度。我们使用束流动力学和探测器模拟证明，$L/G$是优于峰度作为一个实验测量束晕时，考虑到现实的光束形状，探测器的影响和不确定性。除了在助推器中的实验研究结果外，我们还包括$L/G$的基本原理和计算方法，在助推器中我们表明$L/G$是一种有用的晕轮。
Halo Formation in Spheroidal Bunches with Self-Consistent Stationary Distributions
本文构造了一类新的自洽6-D相空间平稳分布。然后，光束纵向和/或横向不匹配，我们探讨了光束的稳定性和晕形成的情况下，3-D轴对称束团使用粒子在细胞模拟。我们专注于束团的长宽比从1到5，这涵盖了APT直线加速器参数的典型范围内的光束。我们发现，纵向晕的形式第一可比的纵向和横向失配。一个有趣的耦合现象-纵向或横向晕观察，即使对于非常小的失配，如果在其他平面的失配是大的-被发现。
Production of Enhanced Beam Halos via Collective Modes and Colored Noise
我们研究如何集体模式和色噪声合谋产生一个光束晕与更大的幅度比可以单独产生的现象。集体模式是最低阶径向本征模计算自洽的配置对应于直流，圆柱对称，温暖的流体Kapchinskij-Vladimirskij平衡。色噪声来自于不可避免的机器误差，并影响内部空间电荷力。它的存在通过不断地将统计上罕见的粒子踢回与集体模式振荡同相，迅速将它们发射到不断增长的振幅。对于纯径向轨道和最初纯方位角轨道，晕幅基本上是相同的;轨道角动量在统计上没有显著的影响。确实有影响的因素包括集体模式的振幅以及色噪声的强度和自相关时间。由于噪声破坏了Kolmogorov-Arnol 'd-Moser环面，否则将限制光束，因此潜在的动力学增强。这些环面是脆弱的;即使是非常微弱的噪音最终也会打破它们，尽管它们解体的时间尺度取决于噪音的强度。因此，集体模式和噪声是非常重要的，在真实光束中的晕形成的动力学。
By means of hollow plasma, multiple proton bunches work well in driving nonlinear plasma wakefields and accelerate electrons to energy frontier with preserved beam quality. However, the acceleration of positrons is different because the accelerating structure is strongly charge dependent. There is a discrepancy between keeping a small normalized emittance and a small energy spread. This results from the conflict that the plasma electrons used to provide focusing to the multiple proton bunches dilute the positron bunch. By loading an extra electron bunch to repel the plasma electrons and meanwh…
Pbar Beam Stacking in the Recycler by Longitudinal Phase-space Coating
屏障射频桶给同步加速器中带电粒子束的纵向束动力学带来了新的挑战，同时也为束流处理带来了许多新的显着前景。在本文中，我描述了一种新的同步加速器束流堆积计划使用障碍桶没有任何发射度稀释的束。首先，我讨论的方法，称为纵向相空间涂层的一般原则。将该方案应用于回收器的多粒子束动力学模拟，有力地验证了该方法的概念和可行性。然后，我在回收机中实验性地演示了该技术，并在操作中使用它。该方案的一个副产品是它的实用性在映射的非相干同步调谐光谱的光束粒子在障碍桶和产生一个干净的空心光束在纵向相空间。这两个都在这里详细描述与插图。这里提出的波束叠加方案是同类方案中的第一个。
Laser Wire Scanner Compton Scattering Techniques for the Measurement of the Transverse Beam Size of Particle Beams at Future Linear Colliders
这个档案总结了2001年至2006年与未来直线对撞机（FLC）的激光线扫描器开发相关的工作论文和会议记录。特别是在PETRA II和CT 2的激光线实验的设计，设置和数据采集进行了说明。该材料侧重于伦敦皇家霍洛威大学（RHUL）开展的活动。
Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment
高功率质子束晕形成的测量是低能示范加速器（LEDA）设施正在进行的科学实验。为了实现这一测量目标，一个52磁铁束线包含几种类型的束诊断仪器正在安装。实验物理和工业控制系统（EPICS）和商业软件应用程序目前正在整合，以提供一个实时，同步数据采集和控制系统。该系统由磁控制、真空控制、电机控制、数据采集和数据分析组成。独特的需求导致了定制软件和硬件的开发和集成。EPICS实时数据库、交互式数据语言（IDL）程序、LabVIEW虚拟仪器（VI）和状态表示语言（SNL）序列托管在基于VXI、PC和UNIX的平台上，这些平台使用EPICS通道访问（CA）通信协议进行交互。采集和控制硬件技术范围从基于DSP的诊断仪器到PLC控制的真空系统。本文主要介绍了控制系统的硬件和软件的设计、实现。
Channeling and Volume Reflection Based Crystal Collimation of Tevatron Circulating Beam Halo (T-980)
T980晶体准直实验正在Tevatron进行，以确定这种技术是否可以提高980 GeV束晕准直效率，如Tevatron和LHC等高能强子对撞机。T980还研究各种晶体类型和参数。在2009年夏天的停机期间，通过在水平测角仪中安装新的O形晶体，以及添加具有两个交替晶体（O形和多条）的垂直测角仪和额外的光束诊断，该设置得到了大幅增强。第一次测量与新系统是相当令人鼓舞的，与预测的二级准直器上观察到的通道和体积反射光束。研究了晶体在体反射和沟道模式下的准直效率，并与非晶主准直器进行了比较。系统性能的结果是为最终的商店的研究和整个对撞机商店。第一次调查碰撞光束准直同时使用晶体在垂直和水平面已在政权与水平通道和垂直体积反射光束。正在计划在FY10夏季关闭期间进行重大的硬件改进，并在Tevatron运行的最后一年进行专门的研究，以及“后对撞机束流物理运行”期间。
Beam Halo and Bunch Purity Monitoring
本文介绍了用于束团晕测量的高动态范围仪器，并讨论了束流仪器角度下的晕定义和量化方法。
The investigation of beam halo transverse distributions is important for the understanding of beam losses and the control of backgrounds in Future Linear Colliders (FLC). A novel in vacuum diamond sensor (DSv) scanner with four strips has been designed and developed for the investigation of the beam halo transverse distributions and also for the diagnostics of Compton recoil electrons after the interaction point (IP) of ATF2, a low energy (1.3 GeV) prototype of the final focus system for the ILC and CLIC linear collider projects. Using the DSv, a dynamic range of $\sim10^6$ has been successful…
Measurement of the nonlinear diffusion of the proton beam halo at the CERN LHC
本文基于Nekhoroshev定理分析框架，通过监测CERN LHC准直器颚板受控移动期间的束流损失信号，测量了质子束晕的非线性扩散系数，验证了其与理论假设的高度一致性，并评估了束束补偿对束尾扩散的有效性。
Cleaning the beam halo using nonlinear AC magnets
针对四维相空间中含束晕的束流分布，本文提出利用高阶非线性交流磁铁捕获并绝热输运束晕，通过理论建模与数值模拟验证清洁效果。
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