Accelerated Particle Beams Research Articles

Prototype of a test bench for applied research on Extracted beams of the nuclotron accelerator complex

The results of the development and testing of elements of a test bench for investigating the impact of accelerated particle beams on biological objects, electronics, and other targets are presented. The systems for beam monitoring and target positioning were tested on extracted argon beams in the framework of experiments on studying the radiation hardness of electronic components.

Nondestructive diagnostics of charged particle beams in accelerators

The basic techniques for nondestructive diagnostics and detection of losses of charged particle beams used in accelerator engineering are reviewed. The data provided may help choose the systems for diagnostics and detection of losses of beams and give a qualitative picture of the operation principles of such devices. Quantitative characteristics that define the limits of applicability of each diagnostic technique are outlined.

A detector based on silica fibers for ion beam monitoring in a wide current range

A detector based on doped silica and optical fibers was developed to monitor the profile of particle accelerator beams of intensity ranging from 1 pA to tens of μA. Scintillation light produced in a fiber moving across the beam is measured, giving information on its position, shape and intensity. The detector was tested with a continuous proton beam at the 18 MeV Bern medical cyclotron used for radioisotope production and multi-disciplinary research. For currents from 1 pA to 20 μA, Ce3+ and Sb3+ doped silica fibers were used as sensors. Read-out systems based on photodiodes, photomultipliers and solid state photomultipliers were employed. Profiles down to the pA range were measured with this method for the first time. For currents ranging from 1 pA to 3 μA, the integral of the profile was found to be linear with respect to the beam current, which can be measured by this detector with an accuracy of ∼1%. The profile was determined with a spatial resolution of 0.25 mm. For currents ranging from 5 μA to 20 μA, thermal effects affect light yield and transmission, causing distortions of the profile and limitations in monitoring capabilities. For currents higher than ∼1 μA, non-doped optical fibers for both producing and transporting scintillation light were also successfully employed.

Software package for modeling spin–orbit motion in storage rings

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Julich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 106–109 particles in a beam during 109 turns in an accelerator (about 1012–1015 integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin–orbit dynamics.

Modeling of the interaction of a volumetric metallic metamaterial structure with a relativistic electron beam

We present the design of avolumetric metamaterial (MTM) structure and its interaction with a relativistic electron beam. This novel structure has promising applications in particle beam diagnostics, acceleration, and microwave generation. The volumetric MTM has a cubic unit cell allowing structures of arbitrary size to be configured as an array of identical cells. This structure allows the exploration of the properties of a metamaterial structure without having to consider substrates or other supporting elements. The dispersion characteristics of the unit cell are obtained using eigenmode simulations in the HFSS code and also using an effective medium theory with spatial dispersion. Good agreement is obtained between these two approaches. The lowest-order mode of the MTM structure is found to have a negative group velocity in all directions of propagation. The frequency spectrum of the radiation from a relativistic electron beam passing through the MTM structure is calculated analytically and also calculated with the CST code, with very good agreement. The radiation pattern from the relativistic electron beam is found to be backward Cherenkov radiation, which is a promising tool for particle diagnostics. Calculations are also presented for the application of a MTM-based wakefield accelerator as a possible all-metal replacement for the conventional dielectric wakefield structure. The proposed structure may also be useful for MTM-based vacuum electron devices for microwave generation and amplification.

A beam of hope for heavy ion radiotherapy: Promising clinical results and better designs are adding new momentum to the push for more proton and carbon ion radiotherapy centers.

A beam of hope for heavy ion radiotherapy: Promising clinical results and better designs are adding new momentum to the push for more proton and carbon ion radiotherapy centers.

Radiation oncology: physics advances that minimize morbidity.

Radiation therapy has become an ever more successful treatment for many cancer patients. This is due in large part from advances in physics including the expanded use of imaging protocols combined with ever more precise therapy devices such as linear and particle beam accelerators, all contributing to treatments with far fewer side effects. This paper will review current state-of-the-art physics maneuvers that minimize morbidity, such as intensity-modulated radiation therapy, volummetric arc therapy, image-guided radiation, radiosurgery and particle beam treatment. We will also highlight future physics enhancements on the horizon such as MRI during treatment and intensity-modulated hadron therapy, all with the continued goal of improved clinical outcomes.

Dynamics of intense particle beam in axial-symmetric magnetic field

Axial-symmetric magnetic field is often used in focusing of particle beams. Most existing ion Low Energy Beam Transport lines are based on solenoid focusing. Modern accelerator projects utilize superconducting solenoids in combination with superconducting accelerating cavities for acceleration of high-intensity particle beams. Present article discusses conditions for matched beam in axial-symmetric magnetic field. Analysis allows us to minimize power consumption of solenoids and beam emittance growth due to nonlinear space charge, lens aberrations, and maximize acceptance of the channel. Expressions for maximum beam current in focusing structure, beam emittance growth due to spherical aberrations and non-linear space charge forces are derived.

High-efficiency acceleration of an electron beam in a plasma wakefield accelerator.

High-efficiency acceleration of charged particle beams at high gradients of energy gain per unit length is necessary to achieve an affordable and compact high-energy collider. The plasma wakefield accelerator is one concept being developed for this purpose. In plasma wakefield acceleration, a charge-density wake with high accelerating fields is driven by the passage of an ultra-relativistic bunch of charged particles (the drive bunch) through a plasma. If a second bunch of relativistic electrons (the trailing bunch) with sufficient charge follows in the wake of the drive bunch at an appropriate distance, it can be efficiently accelerated to high energy. Previous experiments using just a single 42-gigaelectronvolt drive bunch have accelerated electrons with a continuous energy spectrum and a maximum energy of up to 85gigaelectronvolts from the tail of the same bunch in less than a metre of plasma. However, the total charge of these accelerated electrons was insufficient to extract a substantial amount of energy from the wake. Here we report high-efficiency acceleration of a discrete trailing bunch of electrons that contains sufficient charge to extract a substantial amount of energy from the high-gradient, nonlinear plasma wakefield accelerator. Specifically, we show the acceleration of about 74picocoulombs of charge contained in the core of the trailing bunch in an accelerating gradient of about 4.4gigavolts per metre. These core particles gain about 1.6gigaelectronvolts of energy per particle, with a final energy spread as low as 0.7 per cent (2.0 per cent on average), and an energy-transfer efficiency from the wake to the bunch that can exceed 30 per cent (17.7 per cent on average). This acceleration of a distinct bunch of electrons containing a substantial charge and having a small energy spread with both a high accelerating gradient and a high energy-transfer efficiency represents a milestone in the development of plasma wakefield acceleration into a compact and affordable accelerator technology.

The mechanism of coherent radio emission in some classes of pulsar

Radio luminosities have been estimated from published data for a well-defined homogeneous set of 29 normal pulsars. The radio-frequency energies per unit charge in the primary accelerated particle beam are given for each pulsar and form a distribution more than two orders of magnitude in width. The values found show that pulsars are extremely efficient generators of radiation below 1 - 10 GHz given the kinematic constraints which are obtained here in the cases of electron-positron and ion-proton plasmas. Our conclusion is that only the ion-proton plasma source is consistent with the spectra of normal and millisecond pulsars and we list and describe the factors which together support this conclusion.

Open cell conducting foams for high synchrotron radiation accelerators

The possible use of open-cell conductive foams in high synchrotron radiation particle accelerator beam liners is considered. Available materials and modeling tools are reviewed, potential pros and cons are discussed, and preliminary conclusions are drawn.

Magnetic Measurements for Magnets Manufacturing Tolerances Assessment

Superconducting high field magnets are tightly constrained in terms of field quality, since such magnets are usually designed to perform quite demanding tasks, such as focusing particle beams in accelerators, plasma confinement and shaping in fusion devices, and polarizing actions in magnetic resonance. In all these cases, small discrepancies of field map from the design values may strongly impact on device performance. As a consequence, quality insurance procedures are needed to verify if each single coil meets such criteria, e.g., using laser tracking, and possibly warm magnetic measurements. As a matter of fact, external magnetic measurements can be used to estimate the possible deformations of conductors inside the magnet, but this implies inverse problem approaches. The field probes accuracy is therefore critical, and the measurement system must be carefully designed, taking into account the probe characteristics, but also the characteristics of the windings and of the surrounding environment. In this paper, different measurement techniques are compared in terms of sensitivity and accuracy, with reference to various types of sensors and of measurement schemes.

Detecting chaos in particle accelerators through the frequency map analysis method.

The motion of beams in particle accelerators is dominated by a plethora of non-linear effects, which can enhance chaotic motion and limit their performance. The application of advanced non-linear dynamics methods for detecting and correcting these effects and thereby increasing the region of beam stability plays an essential role during the accelerator design phase but also their operation. After describing the nature of non-linear effects and their impact on performance parameters of different particle accelerator categories, the theory of non-linear particle motion is outlined. The recent developments on the methods employed for the analysis of chaotic beam motion are detailed. In particular, the ability of the frequency map analysis method to detect chaotic motion and guide the correction of non-linear effects is demonstrated in particle tracking simulations but also experimental data.

Formation of Accelerated Particle Beam in Isochronous Cyclotron

In the literature there is usually considered a dependence of the one of main beam parameters the value of energy spread, ∆E/E, on cyclotron characteristics for magnetic eld by form closed to isochronous one [1]. Since the output of ion beams from considered installation is realized in decreasing eld, there was carried out an estimation of energetic spread of the beam with nite phase width ∆φ in case of one-revolution output for real magnetic eld that has a decreasing area.

Issues with Phase Space Characterization of Laser-plasma Generated Electron Beams

Abstract Plasma acceleration is the new frontier in particle beam accelerators. Using the strong electric fields inside a plasma it is possible to achieve accelerating gradients orders of magnitude larger with respect to current technologies. Different schemes, using completely different approaches, have been proposed and several already tested, producing beams of energy up to several GeV. Regardless of the technique used for acceleration a precise determination of the output beam parameters is mandatory for the fine tuning of the process. The measurement of these parameters, in particular the beam distribution in transverse and longitudinal phase space, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We illustrate the main problems related to the diagnostic of this kind of beams and some of the proposed or already realized solutions

The Self-Consistent Nonlinear Theory of Charged Particle Beam Acceleration by Slowed Circularly Polarized Electromagnetic Waves

The relativistic interaction of charged particle beams with a circularly polarized electromagnetic wave propagating along a uniform guiding magnetic field in the tunneling of a dielectric medium is analyzed. The acceleration mechanism and a self-consistent nonlinear theory are presented for the interaction of relativistic charged particle beams with electromagnetic waves. Numerical results show that the beam particle can be efficiently accelerated in the interaction process.

Two-dimensional visualization of cluster beams by microchannel plates

An advanced technique for a two-dimensional real time visualization of cluster beams in a vacuum as well as of the overlap volume of cluster beams with particle accelerator beams is presented. The detection system consists of an array of microchannel plates (MCPs) in combination with a phosphor screen which is read out by a CCD camera. This setup together with the ionization of a cluster beam by an electron or ion beam allows for spatial resolved investigations of the cluster beam position, size, and intensity. Moreover, since electrically uncharged clusters remain undetected, the operation in an internal beam experiment opens the way to monitor the overlap region and thus the position and size of an accelerator beam crossing an originally electrically neutral cluster jet. The observed intensity distribution of the recorded image is directly proportional to the convolution of the spatial ion beam and cluster beam intensities and is by this a direct measure of the two-dimensional luminosity distribution. This information can directly be used for the reconstruction of vertex positions as well as for an input for numerical simulations of the reaction zone. The spatial resolution of the images is dominated by the granularity of the complete MCP device and was found to be in the order of σ≈100μm.

Digital Control for a Multiple-Stage Pulsed Current Source

Multiple-stage converters are composed of a set of structures with different voltage, current and switching frequency capabilities. In particular, in applications like particle accelerator beam deflection and focusing, the requirement is high-current high-precision current pulses generation. In order to satisfy the specifications of this application, a novel multiple-stage converter topology was proposed and presented in a previous work. However, said proposal should be complemented with a control system to perform the control of each structure, manage its global interconnection and execute the regulation loops. This work describes the implementation of the digital control developed for the proposed converter. Experimental results are presented by applying the proposed control to a prototype.

Closed form solutions of the heat diffusion equation with a Gaussian source

In the context of the Large Hadron Collider, high energy particles are dumped onto blocks of material that are commonly called beam-dumps. The high energy deposition is almost instantaneous and can be represented by a very high power source for a short period of time. Temperatures can rise above failure limits at the locations of highest energy deposition. Particle beam accelerators are also widely used for medical applications where electron, proton or ion particle beams at energies of the order of megaelectronvolts are used to destroy cancer cells [1]. The motivation of this article is to be able to calculate the temperature fields without turning to numerical simulations that can be very time consuming. We present closed form solutions of the transient heat diffusion problem during the energy deposition. The transient heat diffusion equation assumes infinitely fast propagation of the information throughout the medium, but the diffusion process remains at finite speeds. Energy is deposited in such a small time interval so that the heat flux across the boundaries is assumed to be zero. It follows that the heat diffusion equation can be solved in an infinite medium, by the use of Green’s functions, to provide closed form solutions for the transient temperature field within the pulse time. The range of applicability of these solutions is supported by a parametric relative error analysis. They demand very little computational power and time compared to commercial numerical software.

Ongoing electronic development in the CERN Beam Instrumentation Group: challenges and solutions for the measurement of particle accelerator beam parameters.

The Beam Instrumentation Group (BI) is responsible for designing,building and maintaining the instrumen ts that allow observation ofthe particle beams and the measurement of related parameters for allCERN accelerators and transfer lines. This contribution is aimed togive an overview of the ongoing electronic developments within thebeam instrumentation group both to improve the performances and easethe maintenance of instrumentation in the existing machines and tomeet the requirements of future accelerators. Details on some of thechallenges and proposed technical solutions will be presented.