Sameen Ahmed Khan
Present understanding of accelerator optics is based mainly on classical mechanics and electrodynamics. In recent years quantum theory of charged-particle beam optics has been under development. In this paper the newly developed formalism is outlined.
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The Integrable Optics Test Accelerator (IOTA) at the Fermilab Accelerator Science & Technology (FAST) Facility is beginning operations, with an experimental program aimed at developing technology to enable future high intensity particle beams. The results garnered from IOTA should allow for better control of beam losses, leading to higher safely achievable beam power. This will be particularly useful for future accelerator based neutrino experiments. Two of the R&D efforts at IOTA, Nonlinear Integrable Optics and Electron Column-based space charge compensation, are discussed here.
This lecture introduces major physics and technology aspects of accelerator vacuum systems. Following an introduction, in the second section generic vacuum quantities such as pressure, gas density, the gas equation, pumping speed, conductance are introduced. Since accelerators typically have lengthy vacuum tubes, one-dimensional calculation is in many cases sufficient to compute a pressure profile for an accelerator, and methods for doing so are developed in the next section. In the fourth section accelerator specific aspects of vacuum are considered. This includes lifetime limiting effects fo…
We present a methodology for designing and measuring pulse front tilt in an ultrafast laser for use in dielectric laser acceleration. Previous research into dielectric laser accelerating modules has focused on measuring high accelerating gradients in novel structures, but has done so only for short electron-laser coupling lengths. Here we demonstrate an optical design to extend the laser-electron interaction to 1mm.
Fermilab's Integrable Optics Test Accelerator is an electron storage ring designed for testing advanced accelerator physics concepts, including implementation of nonlinear integrable beam optics and experiments on optical stochastic cooling. The machine is currently under construction at the Advanced Superconducting Test Accelerator facility. In this report we present the goals and the current status of the project, and describe the details of machine design. In particular, we concentrate on numerical simulations setting the requirements on the design and supporting the choice of machine param…
The use of nonlinear lattices with large betatron tune spreads can increase instability and space charge thresholds due to improved Landau damping. Unfortunately, the majority of nonlinear accelerator lattices turn out to be nonintegrable, producing chaotic motion and a complex network of stable and unstable resonances. Recent advances in finding the integrable nonlinear accelerator lattices have led to a proposal to construct at Fermilab a test accelerator with strong nonlinear focusing which avoids resonances and chaotic particle motion. This presentation will outline the main challenges, th…
An interpretation of the ``halo puzzle'' in accelerators based on quantum-like diffraction is given. Comparison between this approach and the others based on classical mechanics equations is exhibited.
Photon-induced near-field electron microscopy (PINEM) is a currently developing spectral approach that characterizes quantum electron-light interactions in electron energy gain/loss spectrum, with symmetrically discretized gains or losses of light quanta ($\hbar ω$), coupled with a laser induced optical near-field. In this letter, we have demonstrated that Linear Particle Accelerator (LPA) and anomalous PINEM (APINEM) can analytically emerge from PINEM-kind interaction in a strong coupling regime, because of quantum interference of spectral photon sidebands overlap. Furthermore, we also found …
The Integrable Optics Test Accelerator (IOTA) is proposed for operation at Fermilab. The goal of IOTA is to create practical nonlinear accelerator focusing systems with a large frequency spread and stable particle motion. The IOTA is a 40 m circumference, 150 MeV (e-), 2.5 MeV (p+) diagnostic test ring. A heavy low frequency steel floor girder is proposed as the primary tier for IOTA device component support. Two design lengths; (8) 3.96 m and (2) 3.1 m long girders with identical cross section completely encompass the ring. This study focuses on the 3.96 m length girder and the development of…
An electron lens is planned for the Fermilab Integrable Optics Test Accelerator as a nonlinear element for integrable dynamics, as an electron cooler, and as an electron trap to study space-charge compensation in rings. We present the main design principles and constraints for nonlinear integrable optics. A magnetic configuration of the solenoids and of the toroidal section is laid out. Single-particle tracking is used to optimize the electron path. Electron beam dynamics at high intensity is calculated with a particle-in-cell code to estimate current limits, profile distortions, and the effec…
We present a design of a stripline kicker for Integrable Optics Test Accelerator (IOTA). For its experimental program IOTA needs two full-aperture kickers, capable to create an arbitrary controllable kick in 2D. For that reason their strengths are variable in a wide range of amplitudes up to 16 mrad, and the pulse length 100 ns is less than a revolution period for electrons. In addition, the kicker should have a physical aperture of 40 mm for a proposed operation with proton beam, and an outer size of 70 mm to fit inside existing quadrupole magnets to save space in the ring. Computer simulatio…
Altering the optics in one section of a linear accelerator beamline will in general cause an alteration of the optics in all downstream sections. In circular accelerators, changing the optical properties of any beamline element will have an impact on the optical functions throughout the whole machine. In many cases, however, it is desirable to change the optics in a certain beamline section without disturbing any other parts of the machine. Such a local optics manipulation can be achieved by adjusting a number of additional corrector magnets that restore the initial optics after the manipulate…
The traditional approach to accelerator optics, based mainly on classical mechanics, is working excellently from the practical point of view. However, from the point of view of curiosity, as well as with a view to explore quantitatively the consequences of possible small quantum corrections to the classical theory, a quantum mechanical formalism of accelerator optics for the Dirac particle is being developed recently. Here, the essential features of such a quantum beam optical formalism for any spin-$\half$ particle are reviewed. It seems that the quantum corrections, particularly those due to…
Vertical excursion fixed-field alternating gradient accelerators can be designed with tunes that are invariant with respect to momentum and trajectories that are scaled images of each other displaced only in the vertical direction. This is possible using guiding fields that have a vertical exponential increase, with a skew quadrupole component in the magnet body and a solenoid component at the magnet ends. Because of the coupling this introduces, orbit and optics calculations and optimisation of parameters need to be performed numerically. In this paper, idealised magnetic fields are calculate…
We outline the design of beam experiments for the electron linac at the Fermilab Accelerator Science and Technology (FAST) facility and for the Integrable Optics Test Accelerator (IOTA), based on synchrotron light emitted by the electrons in bend dipoles, detected with gated microchannel-plate photomultipliers (MCP-PMTs). The system can be used both for beam diagnostics (e.g., beam intensity with full dynamic range, turn-by-turn beam vibrations, etc.) and for scientific experiments, such as the direct observation of the time structure of the radiation emitted by single electrons in a storage r…
The McMillan system is a novel method to increase the tune spread of a beam without decreasing its dynamic aperture due to the systems integrability. While the ideal system is based on an infinitely thin kick, the physical design requires a thick electron lens, including a solenoid. Particle transport through the lens is difficult to simulate due to the nature of the force on the circulating beam. This paper demonstrates accurate simulation of a thick McMillan lens in a solenoid using symplectic integrators derived from Yoshidas method.
The Integrable Optics Test Accelerator (IOTA) is a storage ring for advanced beam physics research currently being built and commissioned at Fermilab. It will operate with protons and electrons using injectors with momenta of 70 and 150 MeV/c, respectively. The research program includes the study of nonlinear focusing integrable optical beam lattices based on special magnets and electron lenses, beam dynamics of space-charge effects and their compensation, optical stochastic cooling, and several other experiments. In this article, we present the design and main parameters of the facility, outl…
An alternative representation for the vector potential of the nonlinear magnetic insert for the Integrable Optics Test Accelerator (IOTA), first described in Sec. V.A. of the paper of Danilov and Nagaitsev, is determined from first principles using standard complex variable methods. In particular, it is shown that the coupled system consisting of the 2D Laplace equation and the Bertrand-Darboux equation is equivalent to a single ordinary differential equation in the complex plane, and a simple solution is constructed. The results are consistent with the paper of Danilov and Nagaitsev, and this…
Many advanced techniques have been developed, tested and implemented in the last decades in almost all circular accelerators across the world to measure the linear optics. However, the greater availability and accuracy of beam diagnostics and the ever better correction of linear magnetic lattice imperfections (beta beating at 1% level and coupling at 0.1%) are reaching what seems to be the intrinsic accuracy and precision of different measurement techniques. This paper aims to highlight and quantify, when possible, the limitations of one standard method, the harmonic analysis of turn-by-turn b…
Operational Accelerator Tuning via Model-Coupled Optics and Bayesian Steering
本文提出了一种基于模型耦合光学与贝叶斯引导的在线调谐策略，通过解耦光学与引导提升加速器调谐的效率与可靠性。
The next generation high energy physics accelerators will require magnetic fields at ~20 T. HTS coils will be an essential component of future accelerator magnets and several efforts are currently dedicated on designing 20 T HTS- LTS hybrid magnets. Among the existing challenges, there is the lack of a robust quench detection system for hybrid magnet technology. Another big challenge is represented by the high number of training quenches required by Nb3Sn magnets to reach performance level. In this framework it is important to find a tool that allow local real-time monitoring of magnet strain …
Non-linear effects in accelerator physics are important for both successful operation of accelerators and during the design stage. Since both of these aspects are closely related, they will be treated together in this overview. Some of the most important aspects are well described by methods established in other areas of physics and mathematics. The treatment will be focused on the problems in accelerators used for particle physics experiments. Although the main emphasis will be on accelerator physics issues, some of the aspects of more general interest will be discussed. In particular, we dem…
A Formalism for the Transport and Matching of Coupled Beams in Accelerators
针对加速器中横向耦合动力学研究，本文基于Mais-Ripken和Lebedev-Bogacz参数化提出耦合束流光学函数传输与匹配的完整形式化方法，支持耦合与非耦合光学，可提取本征模发射度并关联线性差共振与耦合强度。
Recently, the study of integrable Hamiltonian systems has led to nonlinear accelerator lattices with one or two transverse invariants and wide stable tune spreads. These lattices may drastically improve the performance of high-intensity machines, providing Landau damping to protect the beam from instabilities, while preserving dynamic aperture. The Integrable Optics Test Accelerator (IOTA) is being built at Fermilab to study these concepts with 150-MeV pencil electron beams (single-particle dynamics) and 2.5-MeV protons (dynamics with self fields). One way to obtain a nonlinear integrable latt…
These proceedings present the lectures given at the twenty-fourth specialized course organized by the CERN Accelerator School (CAS). The course was held in Ebeltoft, Denmark, from 8-17 June, 2010 in collaboration with Aarhus University, with the topic 'RF for Accelerators' While this topic has been covered by CAS previously, early in the 1990s and again in 2000, it was recognized that recent advances in the field warranted an updated course. Following introductory courses covering the background physics, the course attempted to cover all aspects of RF for accelerators; from RF power generation…
It is reported that [Z. Huang et al., Phys. Rev. Lett. 109, 204801 (2012)], high-gain free-electron laser (FEL) can be generated by transverse-dispersed electron beams from laser-plasma accelerators (LPAs) using transverse-gradient undulator (TGU) assuming an ideal constant dispersion function without focusing optics. The constant dispersion function keeps electrons beyond the resonant energy bandwidth still being on resonant with the FEL radiation. Instead, in this paper, the case with focusing optics in an LPA-driven FEL using TGU is numerically studied, in which the dispersion function shou…
As a joint effort in the JLC/NLC research program, we have developed a new type of damped detuned accelerator structure with optimized round-shaped cavities (RDDS). This paper discusses some important R&D aspects of the first structure in this series (RDDS1). The design aspects covered are the cell design with sub-MHz precision, HOM detuning, coupling and damping technique and wakefield simulation. The fabrication issues covered are ultra-precision cell machining with micron accuracy, assembly and diffusion bonding technologies to satisfactorily meet bookshelf, straightness and cell rotational…
The goal of this manuscript is to give an introduction into the design of the magnet lattice and as a consequence into the transverse dynamics of the particles in a synchrotron or storage ring. Starting from the basic principles of how to design the geometry of the ring we will briefly review the transverse motion of the particles and apply this knowledge to study the layout and optimization of the principal elements, namely the lattice cells. The detailed arrangement of the accelerator magnets within the cells is explained and will be used to calculate well defined and predictable beam parame…
Optics tuning simulations for FCC-ee using Python Accelerator Toolbox
针对超低发射度储存环FCC-ee的光学校正难题，研究利用PyAT开发校正步骤序列，对比两种校正方法后发现耦合RDTs+ηᵧ方法在实现目标发射度和提升动态孔径上表现更优。
Proton Dynamics Scenarios in the Integrable Optics Test Accelerator (IOTA) at Fermilab
本文研究IOTA中2.5 MeV质子束在两种裸露晶格配置下的参数和动态，探讨非线性可积光学和电子冷却的应用，分析束流强度对横向发散率增长的影响。
Achromatic optics using nonlinear plasma lenses for beam-quality preservation between plasma-accelerator stages
本文提出一种紧凑的非色差晶格，利用非线性等离子体透镜在等离子体加速器阶段之间保持束质量，通过分析和数值模拟比较了该方案与传统方案的性能和限制。
Superconducting Accelerator Magnets
本课程介绍超导磁体技术，涵盖材料、结构、制造方法及核心挑战，通过实例展示其在加速器中的应用与优势。
We present a brief summary of various aspects of the electron-cloud effect (ECE) in accelerators. For further details, the reader is encouraged to refer to the proceedings of many prior workshops, either dedicated to EC or with significant EC contents, including the entire "ECLOUD" series [122]. In addition, the proceedings of the various flavors of Particle Accelerator Conferences [23] contain a large number of EC-related publications. The ICFA Beam Dynamics Newsletter series [24] contains one dedicated issue, and several occasional articles, on EC. An extensive reference database is the LHC …
What prevents us from building super-high intensity accelerators? The answer is case-specific, but it often points to one of the following phenomena: machine resonances, various tune shifts (and spreads), and instabilities. These three phenomena are interdependent in all present machines. In this paper we propose a path toward alleviating these phenomena by making accelerators nonlinear. This idea is not new: Orlov (1963) and McMillan (1967) have proposed initial ideas on nonlinear focusing systems for accelerators. However, practical implementations of such ideas proved elusive, until recentl…
Integrable optics is an innovation in particle accelerator design that provides strong nonlinear focusing while avoiding parametric resonances. One promising application of integrable optics is to overcome the traditional limits on accelerator intensity imposed by betatron tune-spread and collective instabilities. The efficacy of high-intensity integrable accelerators will be undergo comprehensive testing over the next several years at the Fermilab Integrable Optics Test Accelerator (IOTA) and the University of Maryland Electron Ring (UMER). We propose an integrable Rapid-Cycling Synchrotron (…
Design of a large energy acceptance beamline using Fixed Field Accelerator optics
针对带电粒子治疗束流配送系统动量接受度小的瓶颈，提出固定场加速器光学的大动量接受度偏转弧设计方法，应用于TURBO项目质子演示系统，验证了可行性并规划后续研发方向。
The stability of non-linear Integrable Optics Test Accelerator (IOTA) model was tested. The area of the stable region in transverse coordinates and the maximum attainable tune spread were found as a function of non-linear lens strength. Particle loss as a function of turn number was analyzed to determine whether a dynamic aperture limitation present in the system. The system was also tested with sextupoles included in the machine for chromaticity compensation. A method of evaluation of the beam size in the linear part of the accelerator was proposed.
A Unified Approach for Coupled Beam Optics in Accelerators
本文提出了一种统一方法，通过规范不变的耦合参数$u_{k,\mathrm{inv}}$来描述加速器中耦合束光学的不变特性。
Nonlinear optics is a promising idea potentially opening the path towards achieving super high beam intensities in circular accelerators. Creation of a tune spread reaching 50% of the betatron tune would provide strong Landau damping and make the beam immune to instabilities. Recent theoretical work has identified a possible way to implement stable nonlinear optics by incorporating nonlinear focusing elements into a specially designed machine lattice. In this report we propose the design of a test accelerator for a proof-of-principle experiment. We discuss possible studies at the machine, requ…
Electro-optical detection has proven to be a valuable technique to study temporal profiles of THz pulses with pulse durations down to femtoseconds. As the Coulomb field around a relativistic electron bunch resembles the current profile, electro-optical detection can be exploited for non-invasive bunch length measurements at accelerators. We have developed a very compact and robust electro-optical detection system based on spectral decoding for bunch length monitoring at the European XFEL with single-shot resolution better than 200~fs. Apart from the GaP crystal and the corresponding laser opti…
We present the results of experimental studies on the transverse and longitudinal dynamics of a single electron in the IOTA storage ring. IOTA is a flexible machine dedicated to beam physics experiments with electrons and protons. A method was developed to reliably inject and circulate a controlled number of electrons in the ring. A key beam diagnostic system is the set of sensitive high-resolution digital cameras for the detection of synchrotron light emitted by the electrons. With 60-130 electrons in the machine, we measured beam lifetime and derived an absolute calibration of the optical sy…
Practical aspects of transverse resonance island buckets at the Cornell Electron Storage Ring: design, control and application
本文提出一种在康奈尔电子储存环6-GeV格架中优化动力学和动量孔径并保持横向共振岛桶（TRIBs）形成条件的新方法，通过降维与优化算法设计旋钮控制TRIBs，并经模拟与实验验证，还提出了单岛驱动方案及应用前景。
The measurement and correction of optics parameters has been a major concern since the advent of strong focusing synchrotron accelerators. A review of typical imperfections in accelerator optics together with measurement and correction algorithms is given with emphasis on numerical implementations. Python examples are shown using existing libraries when possible.
At Integrable Optics Test Accelerator it is possible to create a nonlinear focusing optics with one invariant of motion using just conventional magnets. 6D simulations show that this will allow to achieve a tune spread of 0.05 without significant reduction of dynamic aperture.
This lecture gives an introduction into the design of high-energy storage ring lattices. Applying the formalism that has been established in transverse beam optics, the basic principles of the development of a magnet lattice are explained and the characteristics of the resulting magnet structure are discussed. The periodic assembly of a storage ring cell with its boundary conditions concerning stability and scaling of the beam optics parameters is addressed as well as special lattice insertions such asdrifts, mini beta sections, dispersion suppressors, etc. In addition to the exact calculation…
Introduction to Engineering Materials
本讲座概述加速器应用中工程材料的基础概念，涵盖物质结构、物理性质、主要材料类别及其劣化，并提及在粒子加速器和探测器中的应用。
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