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1

Toward automatic control of particle accelerator beams  

SciTech Connect

We describe a program aiming toward automatic control of particle accelerator beams. A hybrid approach is used, combining knowledge- based system programming techniques and traditional numerical simulations. We use an expert system shell for the symbolic processing and have incorporated the FORTRAN beam optics code TRANSPORT for numerical simulation. The paper discusses the symbolic model we built, the reasoning components, how the knowledge base accesses information from an operating beamline, and the experience gained in merging the two worlds of numeric and symbolic processing. We also discuss plans for a future real-time system. 6 refs., 6 figs.

Schultz, D.E.; Silbar, R.R.

1988-01-01

2

Characterisation of electron beams from laser-driven particle accelerators  

SciTech Connect

The development, understanding and application of laser-driven particle accelerators require accurate measurements of the beam properties, in particular emittance, energy spread and bunch length. Here we report measurements and simulations showing that laser wakefield accelerators can produce beams of quality comparable to conventional linear accelerators.

Brunetti, E.; Manahan, G. G.; Shanks, R. P.; Islam, M. R.; Ersfeld, B.; Anania, M. P.; Cipiccia, S.; Issac, R. C.; Vieux, G.; Welsh, G. H.; Wiggins, S. M.; Jaroszynski, D. A. [Physics Department, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

2012-12-21

3

Particle beam tracker for an accelerating target  

Microsoft Academic Search

The purpose is to use a PI(Proportional plus INTEGRAL) controller to point the centroid of a particle beam at an intended target. Multiple Model Adaptive Estimator is used to estimate the centroid of a one-dimensional Gaussian shaped source of photo-electron events. Merge Method of filter pruning is used to limit the size of this filter. A standard Kalman filter is

L. C. Jamerson

1985-01-01

4

Data handling facility for the Sandia Particle Beam Fusion Accelerator  

SciTech Connect

This paper describes an on-line data handling facility for Sandia's Particle Beam Fusion Accelerator, PBFA-I, and the upgrade prototype machine Supermite. These accelerators are used for research on inertial confinement fusion (ICF) using particle beams. The main objectives in designing the data acquisition system were: (1) process both experiment and machine performance diagnostic signals, (2) record high signal-to-noise ratio, wideband waveforms in a severe EMP environment, (3) support multiple users recording and analyzing data simultaneously, and (4) provide fast turnaround for experimental results. Commercially available equipment is used wherever possible. However, several special purpose devices were developed. This data handling facility is a significant upgrade of an existing system that supports other Sandia particle beam fusion research accelerators.

Boyer, W. B.; Neau, E. L.

1980-01-01

5

Automatic Beam Path Analysis of Laser Wakefield Particle Acceleration Data  

SciTech Connect

Numerical simulations of laser wakefield particle accelerators play a key role in the understanding of the complex acceleration process and in the design of expensive experimental facilities. As the size and complexity of simulation output grows, an increasingly acute challenge is the practical need for computational techniques that aid in scientific knowledge discovery. To that end, we present a set of data-understanding algorithms that work in concert in a pipeline fashion to automatically locate and analyze high energy particle bunches undergoing acceleration in very large simulation datasets. These techniques work cooperatively by first identifying features of interest in individual timesteps, then integrating features across timesteps, and based on the information derived perform analysis of temporally dynamic features. This combination of techniques supports accurate detection of particle beams enabling a deeper level of scientific understanding of physical phenomena than hasbeen possible before. By combining efficient data analysis algorithms and state-of-the-art data management we enable high-performance analysis of extremely large particle datasets in 3D. We demonstrate the usefulness of our methods for a variety of 2D and 3D datasets and discuss the performance of our analysis pipeline.

Rubel, Oliver; Geddes, Cameron G.R.; Cormier-Michel, Estelle; Wu, Kesheng; Prabhat,; Weber, Gunther H.; Ushizima, Daniela M.; Messmer, Peter; Hagen, Hans; Hamann, Bernd; Bethel, E. Wes

2009-10-19

6

Numerical simulations of intense charged particle beam propagation in a dielectric wakefield accelerator  

Microsoft Academic Search

The propagation of an intense electron beam through a long dielectric tube is a critical issue for the success of the dielectric wakefield acceleration scheme. Due to the head-tail instability, a high current charged particle beam cannot propagate long distance without external focusing. In this paper we examine the beam handling and control problem in the dielectric wakefield accelerator. We

W. Gai; A. D. Kanareykin; A. L. Kustov; J. Simpson

1995-01-01

7

Means and method for the focusing and acceleration of parallel beams of charged particles  

DOEpatents

A novel apparatus and method for focussing beams of charged particles comprising planar arrays of electrostatic quadrupoles. The quadrupole arrays may comprise electrodes which are shared by two or more quadrupoles. Such quadrupole arrays are particularly adapted to providing strong focussing forces for high current, high brightness, beams of charged particles, said beams further comprising a plurality of parallel beams, or beamlets, each such beamlet being focussed by one quadrupole of the array. Such arrays may be incorporated in various devices wherein beams of charged particles are accelerated or transported, such as linear accelerators, klystron tubes, beam transport lines, etc.

Maschke, Alfred W. (East Moriches, NY)

1983-07-05

8

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

SciTech Connect

Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator design and the different physical mechanisms of laser-driven and beam-driven plasma acceleration are discussed. Driver propagation is examined, as well as the effects of the excited plasma wave phase velocity. The driver coupling to subsequent plasma accelerator stages for high-energy physics applications is addressed.

Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R.; Leemans, W.P.

2010-06-01

9

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

SciTech Connect

Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator design and the different physical mechanisms of laser-driven and beam-driven plasma acceleration are discussed. Driver propagation is examined, as well as the effects of the excited plasma wave phase velocity. The driver coupling to subsequent plasma accelerator stages for high-energy physics applications is addressed.

Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-11-04

10

Particle-beam tracker for an accelerating target. Master's thesis  

Microsoft Academic Search

The purpose is to use a PI(Proportional plus INTEGRAL) controller to point the centroid of a particle beam at an intended target. Multiple Model Adaptive Estimator is used to estimate the centroid of a one-dimensionald Gaussian shaped source of photoelectron events. Merge Method of filter pruning is used to limit the size of this filter. A standard Kalman filter is

Jamerson

1985-01-01

11

Low energy beam transport for facility for rare isotope beams driver linear particle accelerator  

SciTech Connect

The driver linac for the facility for rare isotope beams (FRIB) will provide a wide range of primary ion beams for nuclear physics research. The linac will be capable of accelerating a uranium beam to an energy of up to 200 Mev/u and delivering it to a fragmentation target with a maximum power of 400 kW. Stable ion beams will be produced by a high performance electron cyclotron resonance ion source operating at 28 GHz. The ion source will be located on a high voltage platform to reach an initial beam energy of 12 keV/u. After extraction, the ion beam will be transported vertically down to the linac tunnel in a low energy beam transport (LEBT) system and injected into a radio frequency quadrupole (RFQ) operating at a frequency of 80.5 MHz. To meet the beam power requirements, simultaneous acceleration of two-charge states will be used for heavier ions ({>=}Xe). This paper presents the layout of the FRIB LEBT and the beam dynamics in the LEBT. In particular, simulation and design of the beam line section before charge state selection will be detailed. The need to use an achromatic design for the charge state selection system and the advantage of an ion beam collimation system to limit the emittance of the beam injected into the RFQ will be discussed in this paper.

Sun, L. T.; Leitner, D.; Machicoane, G.; Pozdeyev, E.; Winklehner, D.; Zhao, Q. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States); Smirnov, V.; Vorozhtsov, S. B. [Joint Institute for Nuclear Research, Dubna, Moscow 141980 (Russian Federation)

2012-02-15

12

Low energy beam transport for facility for rare isotope beams driver linear particle accelerator.  

PubMed

The driver linac for the facility for rare isotope beams (FRIB) will provide a wide range of primary ion beams for nuclear physics research. The linac will be capable of accelerating a uranium beam to an energy of up to 200 Mev?u and delivering it to a fragmentation target with a maximum power of 400 kW. Stable ion beams will be produced by a high performance electron cyclotron resonance ion source operating at 28 GHz. The ion source will be located on a high voltage platform to reach an initial beam energy of 12 keV?u. After extraction, the ion beam will be transported vertically down to the linac tunnel in a low energy beam transport (LEBT) system and injected into a radio frequency quadrupole (RFQ) operating at a frequency of 80.5 MHz. To meet the beam power requirements, simultaneous acceleration of two-charge states will be used for heavier ions (?Xe). This paper presents the layout of the FRIB LEBT and the beam dynamics in the LEBT. In particular, simulation and design of the beam line section before charge state selection will be detailed. The need to use an achromatic design for the charge state selection system and the advantage of an ion beam collimation system to limit the emittance of the beam injected into the RFQ will be discussed in this paper. PMID:22380310

Sun, L T; Leitner, D; Machicoane, G; Pozdeyev, E; Smirnov, V; Vorozhtsov, S B; Winklehner, D; Zhao, Q

2012-02-01

13

Charged particle accelerator grating  

DOEpatents

A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

Palmer, Robert B. (Shoreham, NY)

1986-01-01

14

Course Notes: United States Particle Accelerator School Beam Physics with Intense Space-Charge  

SciTech Connect

The purpose of this course is to provide a comprehensive introduction to the physics of beams with intense space charge. This course is suitable for graduate students and researchers interested in accelerator systems that require sufficient high intensity where mutual particle interactions in the beam can no longer be neglected. This course is intended to give the student a broad overview of the dynamics of beams with strong space charge. The emphasis is on theoretical and analytical methods of describing the acceleration and transport of beams. Some aspects of numerical and experimental methods will also be covered. Students will become familiar with standard methods employed to understand the transverse and longitudinal evolution of beams with strong space charge. The material covered will provide a foundation to design practical architectures. In this course, we will introduce you to the physics of intense charged particle beams, focusing on the role of space charge. The topics include: particle equations of motion, the paraxial ray equation, and the Vlasov equation; 4-D and 2-D equilibrium distribution functions (such as the Kapchinskij-Vladimirskij, thermal equilibrium, and Neuffer distributions), reduced moment and envelope equation formulations of beam evolution; transport limits and focusing methods; the concept of emittance and the calculation of its growth from mismatches in beam envelope and from space-charge non-uniformities using system conservation constraints; the role of space-charge in producing beam halos; longitudinal space-charge effects including small amplitude and rarefaction waves; stable and unstable oscillation modes of beams (including envelope and kinetic modes); the role of space charge in the injector; and algorithms to calculate space-charge effects in particle codes. Examples of intense beams will be given primarily from the ion and proton accelerator communities with applications from, for example, heavy-ion fusion, spallation neutron sources, nuclear waste transmutation, etc.

Barnard, J.J.; Lund, S.M.

2008-05-30

15

Particle in cell simulation of laser-accelerated proton beams for radiation therapy.  

PubMed

In this article we present the results of particle in cell (PIC) simulations of laser plasma interaction for proton acceleration for radiation therapy treatments. We show that under optimal interaction conditions protons can be accelerated up to relativistic energies of 300 MeV by a petawatt laser field. The proton acceleration is due to the dragging Coulomb force arising from charge separation induced by the ponderomotive pressure (light pressure) of high-intensity laser. The proton energy and phase space distribution functions obtained from the PIC simulations are used in the calculations of dose distributions using the GEANT Monte Carlo simulation code. Because of the broad energy and angular spectra of the protons, a compact particle selection and beam collimation system will be needed to generate small beams of polyenergetic protons for intensity modulated proton therapy. PMID:12512712

Fourkal, E; Shahine, B; Ding, M; Li, J S; Tajima, T; Ma, C M

2002-12-01

16

Particle acceleration  

NASA Technical Reports Server (NTRS)

Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

1986-01-01

17

Artificial intelligence research in particle accelerator control systems for beam line tuning  

SciTech Connect

Tuning particle accelerators is time consuming and expensive, with a number of inherently non-linear interactions between system components. Conventional control methods have not been successful in this domain and the result is constant and expensive monitoring of the systems by human operators. This is particularly true for the start-up and conditioning phase after a maintenance period or an unexpected fault. In turn, this often requires a step-by-step restart of the accelerator. Surprisingly few attempts have been made to apply intelligent accelerator control techniques to help with beam tuning, fault detection, and fault recovery problems. The reason for that might be that accelerator facilities are rare and difficult to understand systems that require detailed expert knowledge about the underlying physics as well as months if not years of experience to understand the relationship between individual components, particularly if they are geographically disjoint. This paper will give an overview about the research effort in the accelerator community that has been dedicated to the use of artificial intelligence methods for accelerator beam line tuning.

Pieck, Martin [Los Alamos National Laboratory

2008-01-01

18

Charged particle accelerator grating  

DOEpatents

A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

Palmer, R.B.

1985-09-09

19

Automated detection and analysis of particle beams in laser-plasma accelerator simulations  

Microsoft Academic Search

Numerical simulations of laser-plasma wakefield (particle) accelerators model the acceleration of electrons trapped in plasma oscillations (wakes) left behind when an intense laser pulse propagates through the plasma. The goal of these simulations is to better understand the process involved in plasma wake generation and how electrons are trapped and accelerated by the wake. Understanding of such accelerators, and their

Daniela Mayumi Ushizima; Cameron G. Geddes; Estelle Cormier-Michel; E. Wes Bethel; Janet Jacobsen; Prabhat; O. R. ubel; G Weber; Bernd Hamann

2010-01-01

20

Principles of Charged Particle Acceleration  

NSDL National Science Digital Library

This learning resources comprise a healthy introduction to charged particle acceleration. The site, by Stanley Humphries, a professor of electrical and computer engineering at University of New Mexico, amounts to an online textbook (.pdf) introducing the theory of charged particle acceleration. The book's fifteen chapters (with bibliography) summarize "the principles underlying all particle accelerators" and provide "a reference collection of equations and material essential to accelerator development and beam applications."

21

Laser acceleration of ion beams  

E-print Network

We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.

I. A. Egorova; A. V. Filatov; A. V. Prozorkevich; S. A. Smolyansky; D. B. Blaschke; M. Chubaryan

2006-12-18

22

Loss-proof self-accelerating beams and their use in non-paraxial manipulation of particles' trajectories.  

PubMed

Self-accelerating beams-shape-preserving bending beams-are attracting great interest, offering applications in many areas such as particle micromanipulation, microscopy, induction of plasma channels, surface plasmons, laser machining, nonlinear frequency conversion and electron beams. Most of these applications involve light-matter interactions, hence their propagation range is limited by absorption. We propose loss-proof accelerating beams that overcome linear and nonlinear losses. These beams, as analytic solutions of Maxwell's equations with losses, propagate in absorbing media while maintaining their peak intensity. While the power such beams carry decays during propagation, the peak intensity and the structure of their main lobe region are maintained over large distances. We use these beams for manipulation of particles in fluids, steering the particles to steeper angles than ever demonstrated. Such beams offer many additional applications, such as loss-proof self-bending plasmons. In transparent media these beams show exponential intensity growth, which facilitates other novel applications in micromanipulation and ignition of nonlinear processes. PMID:25355605

Schley, Ran; Kaminer, Ido; Greenfield, Elad; Bekenstein, Rivka; Lumer, Yaakov; Segev, Mordechai

2014-01-01

23

Loss-proof self-accelerating beams and their use in non-paraxial manipulation of particles’ trajectories  

NASA Astrophysics Data System (ADS)

Self-accelerating beams—shape-preserving bending beams—are attracting great interest, offering applications in many areas such as particle micromanipulation, microscopy, induction of plasma channels, surface plasmons, laser machining, nonlinear frequency conversion and electron beams. Most of these applications involve light-matter interactions, hence their propagation range is limited by absorption. We propose loss-proof accelerating beams that overcome linear and nonlinear losses. These beams, as analytic solutions of Maxwell’s equations with losses, propagate in absorbing media while maintaining their peak intensity. While the power such beams carry decays during propagation, the peak intensity and the structure of their main lobe region are maintained over large distances. We use these beams for manipulation of particles in fluids, steering the particles to steeper angles than ever demonstrated. Such beams offer many additional applications, such as loss-proof self-bending plasmons. In transparent media these beams show exponential intensity growth, which facilitates other novel applications in micromanipulation and ignition of nonlinear processes.

Schley, Ran; Kaminer, Ido; Greenfield, Elad; Bekenstein, Rivka; Lumer, Yaakov; Segev, Mordechai

2014-10-01

24

Investigation of Multiple Particle Final States at CEBAF (Continuous Electron Beam Accelerator Facility).  

National Technical Information Service (NTIS)

The physics motivation for the investigation of multiple particle reactions at the CEBAF 4 GeV electron accelerator is examined. The corresponding requirements for the accelerator and the detector are outlined. 10 refs., 4 figs. (ERA citation 13:005059)

B. A. Mecking

1987-01-01

25

Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators.  

PubMed

Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed. PMID:23020369

Silva, T F; Bonini, A L; Lima, R R; Maidana, N L; Malafronte, A A; Pascholati, P R; Vanin, V R; Martins, M N

2012-09-01

26

A stochastic model for the semiclassical collective dynamics of charged beams in particle accelerators  

Microsoft Academic Search

A recent proposal (see quant-ph\\/9803068) to simulate semiclassical\\u000acorrections to classical dynamics by suitable classical stochastic fluctuations\\u000ais applied to the specific instance of charged beam dynamics in particle\\u000aaccelerators. The resulting picture is that the collective beam dynamics, at\\u000athe leading semiclassical order in Planck constant can be described by a\\u000aparticular diffusion process, the Nelson process, which is

Salvatore De Martino; Silvio De Siena; Fabrizio Illuminati

1998-01-01

27

Photonic device particle accelerators and light sources  

Microsoft Academic Search

Laser-driven particle acceleration is revealing itself as a very promising future alternative to RF particle acceleration. The concept of this acceleration technology is to employ a photonic structure that controls an electromagnetic wave in such a way as to produce a continuous acceleration force along the electron beam trajectory. The electrons travel in a vacuum space, which eliminates scattering from

T. Plettner; R. L. Byer; P. P. Lu; K. Sun

2007-01-01

28

Beam dynamics for induction accelerators  

NASA Astrophysics Data System (ADS)

An induction linac uses pulsed power that is applied directly, without any intervening resonant cavities, to accelerate a charged particle pulse. This approach can accommodate a large multiple-beam focusing lattice capable of transporting a large total beam current with a long pulse duration, which may be compressed while accelerating as well as afterward. The mean accelerating gradient is relatively low (less than about 1.5 MV/m), but the potential efficiency of energy transfer can be large up to about 50%. A multiple-beam induction linac is therefore a natural candidate accelerator for a heavy ion fusion (HIF) driver. However, the accelerated beams must meet stringent requirements on occupied phase space volume in order to be focused accurately and with small radius onto the fusion target. Dynamical considerations in the beam injector and linac, as well as in the final compression, final focus, and the fusion chamber, determine the quality of the driver beams as they approach the target. Requirements and tolerances derived from beam dynamics strongly influence the linac configuration and component design.

Lee, Edward P.

2014-01-01

29

Performance of plasma opening switches for the Particle Beam Fusion Accelerator II (PBFA II)  

SciTech Connect

During 1987 and 1988, Plasma Opening Switch (POS) experiments have been continued with the goal of providing voltage and power gain on the PBFA II ion beam accelerator at Sandia National Laboratories. The experiments have developed a POS that has a rugged plasma source, will open rapidly, and will couple to a high-impedance load. The initial erosion switch design with improved plasma uniformity does not couple to these loads. Therefore, we have abandoned further development of this switch for voltage and power gain. Three alternate designs have been developed, tested, and are found to have better performance with the high-impedance loads. These new switches employ magnetic fields to control and confine the injected plasma. A summary of the switch configurations, their theory of operation, and the experimental results is presented and discussed. 4 refs., 10 figs.

Rochau, G.E.; McDaniel, D.H.; Mendel, C.W.; Sweeney, M.A.; Moore, W.B.S.; Mowrer, G.R.; Simpson, W.W.; Zagar, D.M.; Grasser, T.; McDougal, C.D.

1989-01-01

30

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

E-print Network

laser-plasma accelerators were proposed, the technology toplasma physics, and not addressed the driver technology. Itplasma accelerators have benefitted greatly by recent improvements in linac technology

Schroeder, C. B.

2011-01-01

31

Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams  

SciTech Connect

Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

Siemann, R.H.; /SLAC

2011-10-24

32

Particle Beam Radiography  

NASA Astrophysics Data System (ADS)

Particle beam radiography, which uses a variety of particle probes (neutrons, protons, electrons, gammas and potentially other particles) to study the structure of materials and objects noninvasively, is reviewed, largely from an accelerator perspective, although the use of cosmic rays (mainly muons but potentially also high-energy neutrinos) is briefly reviewed. Tomography is a form of radiography which uses multiple views to reconstruct a three-dimensional density map of an object. There is a very wide range of applications of radiography and tomography, from medicine to engineering and security, and advances in instrumentation, specifically the development of electronic detectors, allow rapid analysis of the resultant radiographs. Flash radiography is a diagnostic technique for large high-explosive-driven hydrodynamic experiments that is used at many laboratories. The bremsstrahlung radiation pulse from an intense relativistic electron beam incident onto a high-Z target is the source of these radiographs. The challenge is to provide radiation sources intense enough to penetrate hundreds of g/cm2 of material, in pulses short enough to stop the motion of high-speed hydrodynamic shocks, and with source spots small enough to resolve fine details. The challenge has been met with a wide variety of accelerator technologies, including pulsed-power-driven diodes, air-core pulsed betatrons and high-current linear induction accelerators. Accelerator technology has also evolved to accommodate the experimenters' continuing quest for multiple images in time and space. Linear induction accelerators have had a major role in these advances, especially in providing multiple-time radiographs of the largest hydrodynamic experiments.

Peach, Ken; Ekdahl, Carl

2014-02-01

33

Particle accelerator employing transient space charge potentials  

DOEpatents

The invention provides an accelerator for ions and charged particles. The plasma is generated and confined in a magnetic mirror field. The electrons of the plasma are heated to high temperatures. A series of local coils are placed along the axis of the magnetic mirror field. As an ion or particle beam is directed along the axis in sequence the coils are rapidly pulsed creating a space charge to accelerate and focus the beam of ions or charged particles.

Post, Richard F. (Walnut Creek, CA)

1990-01-01

34

Accelerator system and method of accelerating particles  

NASA Technical Reports Server (NTRS)

An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

Wirz, Richard E. (Inventor)

2010-01-01

35

Electron cloud effects on beam evolution in a circular accelerator  

Microsoft Academic Search

The interaction between a low-density electron cloud in a circular particle accelerator with a circulating charged particle beam is considered. The particle beam's space charge attracts the cloud, enhancing the cloud density near the beam axis. It is shown that this enhanced charge and the image charges associated with the cloud charge and the conducting wall of the accelerator may

G. Rumolo; A. Z. Ghalam; T. Katsouleas; C. K. Huang; V. K. Decyk; C. Ren; W. B. Mori; F. Zimmermann; F. Ruggiero

2003-01-01

36

Neutral particle beam intensity controller  

DOEpatents

A neutral beam intensity controller is provided for a neutral beam generator in which a neutral beam is established by accelerating ions from an ion source into a gas neutralizer. An amplitude modulated, rotating magnetic field is applied to the accelerated ion beam in the gas neutralizer to defocus the resultant neutral beam in a controlled manner to achieve intensity control of the neutral beam along the beam axis at constant beam energy. The rotating magnetic field alters the orbits of ions in the gas neutralizer before they are neutralized, thereby controlling the fraction of neutral particles transmitted out of the neutralizer along the central beam axis to a fusion device or the like. The altered path or defocused neutral particles are sprayed onto an actively cooled beam dump disposed perpendicular to the neutral beam axis and having a central open for passage of the focused beam at the central axis of the beamline. Virtually zero therough 100% intensity control is achieved by varying the magnetic field strength without altering the ion source beam intensity or its species yield.

Dagenhart, William K. (Oak Ridge, TN)

1986-01-01

37

Solar Flares and particle acceleration  

E-print Network

Solar Flares and particle acceleration Eduard Kontar School of Physics and Astronomy University of Glasgow, UK STFC Summer School, Armagh, 2012 #12;Solar flares: basics X-raysradiowavesParticles1AU Figure and accelerated particles #12;Solar flares and accelerated particles From Emslie et al., 2004, 2005 Free magnetic

38

Method and apparatus for varying accelerator beam output energy  

DOEpatents

A coupled cavity accelerator (CCA) accelerates a charged particle beam with rf energy from a rf source. An input accelerating cavity receives the charged particle beam and an output accelerating cavity outputs the charged particle beam at an increased energy. Intermediate accelerating cavities connect the input and the output accelerating cavities to accelerate the charged particle beam. A plurality of tunable coupling cavities are arranged so that each one of the tunable coupling cavities respectively connect an adjacent pair of the input, output, and intermediate accelerating cavities to transfer the rf energy along the accelerating cavities. An output tunable coupling cavity can be detuned to variably change the phase of the rf energy reflected from the output coupling cavity so that regions of the accelerator can be selectively turned off when one of the intermediate tunable coupling cavities is also detuned.

Young, Lloyd M. (Los Alamos, NM)

1998-01-01

39

Electrostatic wire for stabilizing a charged particle beam  

DOEpatents

In combination with a charged particle beam generator and accelerator, apparatus and method are provided for stabilizing a beam of electrically charged particles. A guiding means, disposed within the particle beam, has an electric charge induced upon it by the charged particle beam. Because the sign of the electric charge on the guiding means and the sign of the particle beam are opposite, the particles are attracted toward and cluster around the guiding means to thereby stabilize the particle beam as it travels.

Prono, Daniel S. (Livermore, CA); Caporaso, George J. (Livermore, CA); Briggs, Richard J. (Livermore, CA)

1985-01-01

40

Particle acceleration in solar flares  

NASA Technical Reports Server (NTRS)

The most direct signatures of particle acceleration in flares are energetic particles detected in interplanetary space and in the Earth atmosphere, and gamma rays, neutrons, hard X-rays, and radio emissions produced by the energetic particles in the solar atmosphere. The stochastic and shock acceleration theories in flares are reviewed and the implications of observations on particle energy spectra, particle confinement and escape, multiple acceleration phases, particle anistropies, and solar atmospheric abundances are discussed.

Ramaty, R.; Forman, M. A.

1987-01-01

41

Beam Breakup Effects in Dielectric Based Accelerators  

SciTech Connect

The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.

Schoessow, P.; Kanareykin, A. [Euclid Techlabs LLC, Solon, OH 44139 (United States); Jing, C. [Euclid Techlabs LLC, Solon, OH 44139 (United States); Argonne National Laboratory, IL (United States); Kustov, A. [Dynamics Software, Helsinki (Finland); Altmark, A. [Electrotechnical University Eltech 'LETI', St. Petersburg (Russian Federation); Power, J. G.; Gai, W. [Argonne National Laboratory, IL (United States)

2009-01-22

42

Beam Breakup Effects in Dielectric Based Accelerators  

NASA Astrophysics Data System (ADS)

The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.

Schoessow, P.; Kanareykin, A.; Jing, C.; Kustov, A.; Altmark, A.; Power, J. G.; Gai, W.

2009-01-01

43

On the possibility of laboratory shock wave studies of the equation of state of a material at gigabar pressures with beams of laser-accelerated particles  

NASA Astrophysics Data System (ADS)

The possibility of laboratory shock wave studies of the equation of state of a material with beams of laser-accelerated charged particles at pressures an order of magnitude higher than those reached in current experiments has been discussed. The possibility of the generation of a plane quasistationary shock wave with a pressure of several gigabars behind its front at the irradiation of a target by a laser beam with an energy of several kilojoules and an intensity of about 1017 W/cm2, which is accompanied by the generation of fast electrons with an average energy of 20-50 keV, has been justified.

Gus'kov, S. Yu.

2014-09-01

44

Particle beams with uniform transverse distribution  

SciTech Connect

A successfully tested method is described which achieves a more uniform illumination of an extended flat target by the charged particle beam from an accelerator, by proper use of a combination of quadrupole and octupole magneto-optical elements.

Tsoupas, N.; Zucker, M.S.; Snead, C.L.; Ward, T.E.

1996-10-01

45

Particle beam injector system and method  

DOEpatents

Methods and devices enable coupling of a charged particle beam to a radio frequency quadrupole accelerator. Coupling of the charged particle beam is accomplished, at least in-part, by relying on of sensitivity of the input phase space acceptance of the radio frequency quadrupole to the angle of the input charged particle beam. A first electric field across a beam deflector deflects the particle beam at an angle that is beyond the acceptance angle of the radio frequency quadrupole. By momentarily reversing or reducing the established electric field, a narrow portion of the charged particle beam is deflected at an angle within the acceptance angle of the radio frequency quadrupole. In another configuration, beam is directed at an angle within the acceptance angle of the radio frequency quadrupole by the first electric field and is deflected beyond the acceptance angle of the radio frequency quadrupole due to the second electric field.

Guethlein, Gary

2013-06-18

46

Non-accelerator Particle Physics  

E-print Network

Non-accelerator Particle Physics and Neutrino Physics Research programs of: Prof. Martin that often connect particle physics with astrophysics and cosmology Some questions: - What particles of the neutrino? #12;The techniques: Laboratory experiments, in the style of particle physics · High energy

Wechsler, Risa H.

47

Safety training and safe operating procedures written for PBFA (Particle Beam Fusion Accelerator) II and applicable to other pulsed power facilities  

SciTech Connect

To ensure that work in advancing pulsed power technology is performed with an acceptably low risk, pulsed power research facilities at Sandia National Laboratories must satisfy general safety guidelines established by the Department of Energy, policies and formats of the Environment, Safety, and Health (ES and H) Department, and detailed procedures formulated by the Pulsed Power Sciences Directorate. The approach to safety training and to writing safe operating procedures, and the procedures presented here are specific to the Particle Beam Fusion Accelerator II (PBFA II) Facility but are applicable as guidelines to other research and development facilities which have similar hazards.

Donovan, G.L.; Goldstein, S.A.

1986-12-01

48

Particle acceleration at planetary bow shock waves  

Microsoft Academic Search

One property of the collisionless shocks that may be studied through a comparison of their behavior in a variety of plasma conditions at several different planets is the occurrence of MHD waves, associated with particle beams accelerated at these shocks and flowing backward to the sun. Mercury, Venus, earth and Jupiter observations of one of these wave classes show that

M. M. Hoppe

1982-01-01

49

Space Experiments with Particle Accelerators: SEPAC  

NASA Technical Reports Server (NTRS)

The Space Experiments with Particle Accelerators (SEPAC), which flew on the Atmospheric Laboratory for Applications and Science (ATLAS) 1 mission, used new techniques to study natural phenomena in the Earth's upper atmosphere, ionosphere and magnetosphere by introducing energetic perturbations into the system from a high power electron beam with known characteristics. Properties of auroras were studied by directing the electron beam into the upper atmosphere while making measurements of optical emissions. Studies were also performed of the critical ionization velocity phenomenon.

Burch, J. L.; Roberts, W. T.; Taylor, W. W. L.; Kawashima, N.; Marshall, J. A.; Moses, S. L.; Neubert, T.; Mende, S. B.; Choueiri, E. Y.

1994-01-01

50

Recent progress in techniques utilized for particle accelerator  

NASA Astrophysics Data System (ADS)

Particle accelerators are widely used in scientific research and industry. Recently, techniques utilized for accelerator are developed rapidly in China. We briefly review the recent progress in this field and primarily focus on superconducting RF, innovative structures for particle production and acceleration and beam diagnosis. Several advanced compact user facilities are also introduced.

Liu, KeXin

2012-12-01

51

Space Experiments with Particle Accelerators (SEPAC)  

NASA Technical Reports Server (NTRS)

The purpose of Space Experiments with Particle Accelerators (SEPAC) on the Atmospheric Laboratory for Applications and Science (ATLAS 1) mission, is to carry out active and interactive experiments on and in the earth's ionosphere, atmosphere, and magnetosphere. The instruments to be used are an electron beam accelerator (EBA), plasma contactor, and associated instruments the purpose of which is to perform diagnostic, monitoring, and general data taking functions. Four major classes of investigations are to be performed by SEPAC. They are: beam plasma physics, beam-atmosphere interactions, the use of modulated electron beams as transmitting antennas, and the use of electron beams for remote sensing of electric and magnetic fields. The first class consists mainly of onboard plasma physics experiments to measure the effects of phenomena in the vicinity of the shuttle. The last three are concerned with remote effects and are supported by other ATLAS 1 investigations as well as by ground-based observations.

Obayashi, Tatsuzo

1988-01-01

52

Design, modeling and simulations of a Cabinet Safe System for a linear particle accelerator of intermediate-low energy by optimization of the beam optics  

NASA Astrophysics Data System (ADS)

As part of an accelerator based Cargo Inspection System, studies were made to develop a Cabinet Safe System by Optimization of the Beam Optics of Microwave Linear Accelerators of the IAC-Varian series working on the S-band and standing wave pi/2 mode. Measurements, modeling and simulations of the main subsystems were done and a Multiple Solenoidal System was designed. This Cabinet Safe System based on a Multiple Solenoidal System minimizes the radiation field generated by the low efficiency of the microwave accelerators by optimizing the RF waveguide system and by also trapping secondaries generated in the accelerator head. These secondaries are generated mainly due to instabilities in the exit window region and particles backscattered from the target. The electron gun was also studied and software for its right mechanical design and for its optimization was developed as well. Besides the standard design method, an optimization of the injection process is accomplished by slightly modifying the gun configuration and by placing a solenoid on the waist position while avoiding threading the cathode with the magnetic flux generated. The Multiple Solenoidal System and the electron gun optimization are the backbone of a Cabinet Safe System that could be applied not only to the 25 MeV IAC-Varian microwave accelerators but, by extension, to machines of different manufacturers as well. Thus, they constitute the main topic of this dissertation.

Maidana, Carlos Omar

53

Particle acceleration in pulsar magnetospheres  

NASA Technical Reports Server (NTRS)

The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.

Baker, K. B.

1978-01-01

54

Beam losses and beam halos in accelerators for new energy sources  

SciTech Connect

Large particle accelerators are proposed as drivers for new ways to produce electricity from nuclear fusion and fission reactions. The accelerators must be designed to deliver large particle beam currents to a target facility with very little beam spill along the accelerator itself, in order that accelerator maintenance can be accomplished without remote manipulators. Typically, particle loss is preceded by the formation of a tenuous halo of particles around the central beam core, caused by beam dynamics effects, often coupled with the slight imperfections inevitable in a practical design. If the halo becomes large enough, particles may be scraped off along the accelerator. The tolerance for beam spill in different applications is discussed, halo mechanisms and recent work to explore and understand their dynamics are reviewed, and possible directions for future investigation are outlined. 17 refs., 10 figs.

Jameson, R.A.

1995-12-31

55

Particle acceleration by electromagnetic waves.  

PubMed

We consider the symmetry in the interaction of photons and electrons, which has led to a common description of electron and photon accelerations; effects such as photon Landau damping arise naturally from such a treatment. Intense electromagnetic waves can act as a photon mirror to charged particles. The subsequent acceleration is equivalent to the photon pulse accelerating electrons. During the interaction or reflection process, the charged particle can emit bursts of radiation similar to the radiation emitted from the particles during wave breaking of plasma waves. PMID:18218605

Bingham, R

2008-05-28

56

Space Experiments with Particle Accelerators (SEPAC)  

NASA Technical Reports Server (NTRS)

The scientific emphasis of this contract has been on the physics of beam ionosphere interactions, in particular, what are the plasma wave levels stimulated by the Space Experiments with Particle Accelerators (SEPAC) electron beam as it is ejected from the Electron Beam Accelerator (EBA) and passes into and through the ionosphere. There were two different phenomena expected. The first was generation of plasma waves by the interaction of the DC component of the beam with the plasma of the ionosphere, by wave particle interactions. The second was the generation of waves at the pulsing frequency of the beam (AC component). This is referred to as using the beam as a virtual antenna, because the beam of electrons is a coherent electrical current confined to move along the earth's magnetic field. As in a physical antenna, a conductor at a radio or TV station, the beam virtual antenna radiates electromagnetic waves at the frequency of the current variations. These two phenomena were investigated during the period of this contract.

Taylor, William W. L.

1994-01-01

57

The beam business: Accelerators in industry  

SciTech Connect

Most physicists know that particle accelerators are widely used for treating cancer. But few are acquainted with the depth and breadth of their use in a myriad of applications outside of pure science and medicine. Society benefits from the use of particle beams in the areas of communications, transportation, the environment, security, health, and safety - in terms both of the global economy and quality of life. On the manufacturing level, the use of industrial accelerators has resulted in the faster and cheaper production of better parts for medical devices, automobiles, aircraft, and virtually all modern electronics. Consumers also benefit from the use of accelerators to explore for oil, gas, and minerals; sterilize food, wastewater, and medical supplies; and aid in the development of drugs and biomaterials.

Hamm, Robert W.; Hamm, Marianne E. [Pleasanton, California (United States)

2011-06-15

58

Particle acceleration in dipolarization events  

NASA Astrophysics Data System (ADS)

Using the electromagnetic fields of a recent MHD simulation of magnetotail reconnection, flow bursts and dipolarization, we investigate the acceleration of test particles (protons and electrons) to suprathermal energies, confirming and extending earlier results on acceleration mechanisms and sources. (Part of the new results have been reviewed recently in Birn et al., Space Science Reviews, 167, doi:10.1007/ s11214-012-9874-4.) The test particle simulations reproduce major features of energetic particle events (injections) associated with substorms or other dipolarization events, particularly a rapid rise of energetic particle fluxes over limited ranges of energy. The major acceleration mechanisms for electrons are betatron acceleration and Fermi acceleration in the collapsing magnetic field. Ions, although non-adiabatic, undergo similar acceleration. Two major entry mechanisms into the acceleration site are identified: cross-tail drift from the inner tail plasma sheet and reconnection entry from field lines extending to the more distant plasma sheet. The former dominates early in an event and at higher energies (hundreds of keV) while the latter constitutes the main source later and at lower energies (tens of keV). Despite the fact that the injection front moves earthward in the tail, the peak of energetic particle fluxes moves to higher latitude when mapped from the near-Earth boundary to Earth in a static magnetic field model.

Birn, J.; Hesse, M.; Nakamura, R.; Zaharia, S.

2013-05-01

59

A particle accelerator employing transient space charge potentials  

DOEpatents

The invention provides an accelerator for ions and charged particles. The plasma is generated and confined in a magnetic mirror field. The electrons of the plasma are heated to high temperatures. A series of local coils are placed along the axis of the magnetic mirror field. As an ion or particle beam is directed along the axis in sequence the coils are rapidly pulsed creating a space charge to accelerate and focus the beam of ions or charged particles. 3 figs.

Post, R.F.

1988-02-25

60

Fresnel diffraction patterns as accelerating beams  

NASA Astrophysics Data System (ADS)

We demonstrate that beams originating from Fresnel diffraction patterns are self-accelerating in free space. In addition to accelerating and self-healing, they also exhibit parabolic deceleration property, which is in stark contrast to other accelerating beams. We find that the trajectory of Fresnel paraxial accelerating beams is similar to that of nonparaxial Weber beams. Decelerating and accelerating regions are separated by a critical propagation distance, at which no acceleration is present. During deceleration, the Fresnel diffraction beams undergo self-smoothing, in which oscillations of the diffracted waves gradually focus and smooth out at the critical distance.

Zhang, Yiqi; Beli?, Milivoj R.; Zheng, Huaibin; Wu, Zhenkun; Li, Yuanyuan; Lu, Keqing; Zhang, Yanpeng

2013-11-01

61

Laser and Particle Guiding Micro-Elements for Particle Accelerators  

SciTech Connect

Laser driven particle accelerators require sub-micron control of the laser field as well as precise electron-beam guiding so fabrication techniques that allow integrating both elements into an accelerator-on-chip format become critical for the success of such next generation machines. Micromachining technology for silicon has been shown to be one such feasible technology in PAC2003[1] but with a variety of complications on the laser side. However, fabrication of transparent ceramics has become an interesting technology that could be applied for laser-particle accelerators in several ways. We discuss the advantages such as the range of materials available and ways to implement them followed by some different test examples we been considered. One important goal is an integrated system that avoids having to inject either laser or particle pulses into these structures.

Plettner, T.; Gaume, R.; Wisdom, J.; /Stanford U., Phys. Dept.; Spencer, J.; /SLAC

2005-06-07

62

Space experiments with particle accelerators. [Spacelab  

NASA Technical Reports Server (NTRS)

The purpose of space experiments with particle accelerators (SEPAC) is to carry out active and interactive experiments on and in the Earth's ionosphere and magnetosphere. It is also intended to make an initial performance test for an overall program of Spacelab/SEPAC experiments. The instruments to be used are an electron beam accelerator, magnetoplasma dynamic arcjet, and associated diagnostic equipment. The accelerators are installed on the pallet, with monitoring and diagnostic observations being made by the gas plume release, beam-monitor TV, and particle-wave measuring instruments also mounted on the pallet. Command and display systems are installed in the module. Three major classes of investigations to be performed are vehicle charge neutralization, beam plasma physics, and beam atmosphere interactions. The first two are mainly onboard plasma physics experiments to measure the effect of phenomena in the vicinity of Spacelab. The last one is concerned with atmospheric modification and is supported by other Spacelab 1 investigations as well as by ground-based, remote sensing observations.

Obayashi, T.

1981-01-01

63

Cosmic Particle Acceleration: Basic Issues  

E-print Network

Cosmic-rays are ubiquitous, but their origins are surprisingly difficult to understand. A review is presented of some of the basic issues common to cosmic particle accelerators and arguments leading to the likely importance of diffusive shock acceleration as a general explanation. The basic theory of diffusive shock acceleration is outlined, followed by a discussion of some of the key issues that still prevent us from a full understanding of its outcomes. Some recent insights are mentioned at the end that may help direct ultimate resolution of our uncertainties.

T. W. Jones

2000-12-22

64

Nonparaxial Mathieu and Weber Accelerating Beams  

NASA Astrophysics Data System (ADS)

We demonstrate both theoretically and experimentally nonparaxial Mathieu and Weber accelerating beams, generalizing the concept of previously found accelerating beams. We show that such beams bend into large angles along circular, elliptical, or parabolic trajectories but still retain nondiffracting and self-healing capabilities. The circular nonparaxial accelerating beams can be considered as a special case of the Mathieu accelerating beams, while an Airy beam is only a special case of the Weber beams at the paraxial limit. Not only do generalized nonparaxial accelerating beams open up many possibilities of beam engineering for applications, but the fundamental concept developed here can be applied to other linear wave systems in nature, ranging from electromagnetic and elastic waves to matter waves.

Zhang, Peng; Hu, Yi; Li, Tongcang; Cannan, Drake; Yin, Xiaobo; Morandotti, Roberto; Chen, Zhigang; Zhang, Xiang

2012-11-01

65

A Fundamental Theorem on Particle Acceleration  

SciTech Connect

A fundamental theorem on particle acceleration is derived from the reciprocity principle of electromagnetism and a rigorous proof of the theorem is presented. The theorem establishes a relation between acceleration and radiation, which is particularly useful for insightful understanding of and practical calculation about the first order acceleration in which energy gain of the accelerated particle is linearly proportional to the accelerating field.

Xie, Ming

2003-05-01

66

Beam Breakup Effects in Dielectric Based Accelerators  

Microsoft Academic Search

The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off

P. Schoessow; A. Kanareykin; C. Jing; A. Kustov; A. Altmark; J. G. Power; W. Gai

2009-01-01

67

Naked singularities as particle accelerators  

SciTech Connect

We investigate here the particle acceleration by naked singularities to arbitrarily high center of mass energies. Recently it has been suggested that black holes could be used as particle accelerators to probe the Planck scale physics. We show that the naked singularities serve the same purpose and probably would do better than their black hole counterparts. We focus on the scenario of a self-similar gravitational collapse starting from a regular initial data, leading to the formation of a globally naked singularity. It is seen that when particles moving along timelike geodesics interact and collide near the Cauchy horizon, the energy of collision in the center of mass frame will be arbitrarily high, thus offering a window to Planck scale physics.

Patil, Mandar; Joshi, Pankaj S. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2010-11-15

68

Fast ion mass spectrometry and charged particle spectrography investigations of transverse ion acceleration and beam-plasma interactions  

NASA Technical Reports Server (NTRS)

Ion acceleration transverse to the magnetic field in the topside ionosphere was investigated. Transverse acceleration is believed to be responsible for the upward-moving conical ion distributions commonly observed along auroral field lines at altitudes from several hundred to several thousand kilometers. Of primary concern in this investigation is the extent of these conic events in space and time. Theoretical predictions indicate very rapid initial heating rates, depending on the ion species. These same theories predict that the events will occur within a narrow vertical region of only a few hundred kilometers. Thus an instrument with very high spatial and temporal resolution was required; further, since different heating rates were predicted for different ions, it was necessary to obtain composition as well as velocity space distributions. The fast ion mass spectrometer (FIMS) was designed to meet these criteria. This instrument and its operation is discussed.

Gibson, W. C.; Tomlinson, W. M.; Marshall, J. A.

1987-01-01

69

Application of charged particle beams of TWAC-ITEP accelerator for diagnostics of high dynamic pressure processes  

Microsoft Academic Search

The 800 MeV proton radiography facility for high dynamic pressure research in condensed matter has been commissioned at the Terrawatt Accelerator of Institute of Theoretical and Experimental Physics (TWAC-ITEP) in Moscow. Spatial resolution of the facility measured in static experiments with a variety of test objects was found to be 0.30±0.01 mm in current experimental arrangement. First dynamic experiments on the observation

S. A. Kolesnikov; A. A. Golubev; V. S. Demidov; S. V. Dudin; A. V. Kantsyrev; V. B. Mintsev; G. N. Smirnov; V. I. Turtikov; A. V. Utkin; B. Y. Sharkov; V. E. Fortov

2010-01-01

70

Particle Acceleration at Interplanetary Discontinuities  

NASA Astrophysics Data System (ADS)

Interplanetary discontinuities, long-duration Alfvenic fluctuations and transient structures such as shocks, stream interfaces (SIs), and coronal mass ejections (CME's) are considered to be prime candidates for accelerating particles in space and are therefore also responsible for producing the suprathermal particle population. The spectral slope of the phase space density of of the suprathermal particle population has been reported to cluster around v-5 but may vary significantly over longer time periods [1]. It is unclear, however, how such as slope is generated and how these interplanetary structures contribute. In a statistical study for the years 2007-2009 we investigate shocks, SIs (alone or combined) as well as CME's with respect to ion acceleration efficiency and the formation of suprathermal tails in the particle distribution. This depends on solar wind plasma conditions (for example, the presence of Alfvenic fluctuations) and on the acceleration process, the shock geometry, and on the intensity of the source population. Pickup helium (He+) is an excellent tracer for interplanetary discontinuities. It is abundant at these plasma discontinuities because it is preferentially accelerated compared to solar wind ions (including He+2). This study shows that all of these discontinuities produce a suprathermal population with varying number density and spectral slope. Depending on the discontinuity/structure type, the solar wind plasma conditions, the data accumulation time, and the location within the discontinuity, the slopes of the suprathermal tails are shown to vary between v-3 and v-7. This large range is most likely due to the fact that the plasma at these discontinuities has not yet reached stationary state conditions. This conjecture can be confirmed by measurements and simulated particle distributions. [1] Gloeckler et al., : AIP Conf. Proc. 1436, 136 (2012); doi: 10.1063/1.4723601

Kucharek, Harald; Farrugia, Charles; Popecki, Mark; Klecker, Berndt; Simunac, Kristin; Galvin, Antoinette

2014-05-01

71

Radial particle distributions in PARMILA simulation beams  

SciTech Connect

The estimation of beam spill in particle accelerators is becoming of greater importance as higher current designs are being funded. To the present, no numerical method for predicting beam-spill has been available. In this paper, we present an approach to the loss-estimation problem that uses probability distributions fitted to particle-simulation beams. The properties of the PARMILA code's radial particle distribution are discussed, and a broad class of probability distributions are examined to check their ability to fit it. The possibility that the PARMILA distribution is a mixture is discussed, and a fitting distribution consisting of a mixture of two generalized gamma distributions is found. An efficient algorithm to accomplish the fit is presented. Examples of the relative prediction of beam spill are given. 26 references, 18 figures, 1 table.

Boicourt, G.P.

1984-03-01

72

Space Experiments with Particle Accelerators (SEPAC)  

NASA Technical Reports Server (NTRS)

Plans for SEPAC, an instrument array to be used on Spacelab 1 to study vehicle charging and neutralization, beam-plasma interaction in space, beam-atmospheric interaction exciting artificial aurora and airglow, and the electromagnetic-field configuration of the magnetosphere, are presented. The hardware, consisting of electron beam accelerator, magnetoplasma arcjet, neutral-gas plume generator, power supply, diagnostic package (photometer, plasma probes, particle analyzers, and plasma-wave package), TV monitor, and control and data-management unit, is described. The individual SEPAC experiments, the typical operational sequence, and the general outline of the SEPAC follow-on mission are discussed. Some of the experiments are to be joint ventures with AEPI (INS 003) and will be monitored by low-light-level TV.

Obayashi, T.; Kawashima, N.; Kuriki, K.; Nagatomo, M.; Ninomiya, K.; Sasaki, S.; Ushirokawa, A.; Kudo, I.; Ejiri, M.; Roberts, W. T.

1982-01-01

73

PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS  

SciTech Connect

Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. Plasma-based accelerators have attracted considerable attention owing to the ultrahigh field gradients sustainable in a plasma wave, enabling compact accelerators. These relativistic plasma waves are excited by displacing electrons in a neutral plasma. Two basic mechanisms for excitation of plasma waves are actively being researched: (i) excitation by the nonlinear ponderomotive force (radiation pressure) of an intense laser or (ii) excitation by the space-charge force of a dense charged particle beam. There has been significant recent experimental success using lasers and particle beam drivers for plasma acceleration. In particular, for laser-plasma accelerators (LPAs), the demonstration at LBNL in 2006 of high-quality, 1 GeV electron beams produced in approximately 3 cm plasma using a 40 TW laser. In 2007, for beam-driven plasma accelerators, or plasma-wakefield accelerators (PWFAs), the energy doubling over a meter to 42 GeV of a fraction of beam electrons on the tail of an electron beam by the plasma wave excited by the head was demonstrated at SLAC. These experimental successes have resulted in further interest in the development of plasma-based acceleration as a basis for a linear collider, and preliminary collider designs using laser drivers and beam drivers are being developed. The different physical mechanisms of plasma wave excitation, as well as the typical characteristics of the drivers, have implications for accelerator design. In the following, we identify the similarities and differences between wave excitation by lasers and particle beams. The field structure of the plasma wave driven by lasers or particle beams is discussed, as well as the regimes of operation (linear and nonlinear wave). Limitations owing to driver emittance are also discussed.

Schroeder, Carl B.; Esarey, Eric; Benedetti, Carlo; Toth, Csaba; Geddes, Cameron; Leemans, Wim

2011-04-01

74

[Proton therapy and particle accelerators].  

PubMed

Since the high energy accelerator plan was changed from a 40 GeV direct machine to a 12GeV cascade one, a 500 MeV rapid cycling booster synchrotron was installed between the injector linac and the 12 GeV main ring at KEK, National Lab. for High Energy Physics. The booster beams were used not only for injection to the main ring but also for medical use. Their energy was reduced to 250 MeV by a graphite block for clinical trial of cancer therapy. In 1970's, pi(-) or heavy ions were supposed to be promising. Although advantage of protons with Bragg Peak was pointed out earlier, they seemed effective only for eye melanoma at that time. In early 1980's, it was shown that they were effective for deep-seated tumor by Tsukuba University with KEK beams. The first dedicated facility was built at Loma Linda University Medical Center. Its synchrotron was made by Fermi National Accelerator Lab. Since a non-resonant accelerating rf cavity was installed, operation of the synchrotron became much easier. Later, innovation of the cyclotron was achieved. Its weight was reduced from 1,000 ton to 200 ton. Some of the cyclotrons are equipped with superconducting coils. PMID:24592677

Fukumoto, Sadayoshi

2012-01-01

75

Use of particle beams for lunar prospecting  

NASA Technical Reports Server (NTRS)

A key issue in choosing the appropriate site for a manned lunar base is the availability of resources, particularly oxygen and hydrogen for the production of water, and ores for the production of fuels and building materials. NASA has proposed two Lunar Scout missions that would orbit the Moon and use, among other instruments, a hard X-ray spectrometer, a neutron spectrometer, and a Ge gamma ray spectrometer to map the lunar surface. This passive instrumentation will have low resolution (tens of kilometers) due to the low signal levels produced by natural radioactivity and the interaction of cosmic rays and the solar wind with the lunar surface. This paper presents the results of a concept definition effort for a neutral particle beam lunar mapper probe. The idea of using particle beam probes to survey asteroids was first proposed by Sagdeev et al., and an ion beam device was fielded on the 1988 Soviet probe to the Mars moon Phobos. During the past five years, significant advances in the technology of neutral particle beams (NPB) have led to a suborbital flight of a neutral hydrogen beam device in the SDIO-sponsored BEAR experiment. An orbital experiment, the Neutral Particle Beam Far Field Optics Experiment (NPB-FOX) is presently in the preliminary design phase. The development of NPB accelerators that are space-operable leads one to consider the utility of these devices for probing the surface of the Moon using gamma ray, X-ray, and optical/UV spectroscopy to locate various elements and compounds. We consider the utility of the NPB-FOX satellite containing a 5-MeV particle beam accelerator as a probe in lunar orbit. Irradiation of the lunar surface by the particle beam will induce secondary and back scattered radiation from the lunar surface to be detected by a sensor that may be co-orbital with or on the particle beam satellite platform, or may be in a separate orbit. The secondary radiation is characteristic of the make-up of the lunar surface. The size of the spot irradiated by the beam is less than 1 km wide along the ground track of the satellite, resulting in the potential for high resolution. The fact that the probe could be placed in polar orbit would result in global coverage of the lunar surface. The orbital particle beam probe could provide the basis for selection of sites for more detailed prospecting by surface rovers.

Toepfer, A. J.; Eppler, D.; Friedlander, A.; Weitz, R.

1993-01-01

76

Microwaves and particle accelerators: a fundamental link  

SciTech Connect

John Cockcroft's splitting of the atom and Ernest Lawrence's invention of the cyclotron in the first half of the twentieth century ushered in the grand era of ever higher energy particle accelerators to probe deeper into matter. It also forged a link, bonding scientific discovery with technological innovation that continues today in the twenty first century. The development of radar and high power vacuum electronics, especially microwave power tubes like the magnetrons and the klystrons in the pre-second world war era, was instrumental in the rapid development of circular and linear charged particle accelerators in the second half of the twentieth century. We had harnessed the powerful microwave radio-frequency sources from few tens of MHz to up to 90 GHz spanning L-band to W-band frequencies. Simultaneously in the second half of the twentieth century, lasers began to offer very first opportunities of controlling charged particles at smaller resolutions on the scale of wavelengths of visible light. We also witnessed in this period the emergence of the photon and neutron sciences driven by accelerators built-by-design producing tailored and ultra-bright pulses of bright photons and neutrons to probe structure and function of matter from aggregate to individual molecular and atomic scales in unexplored territories in material and life sciences. As we enter the twenty first century, the race for ever higher energies, brightness and luminosity to probe atto-metric and atto-second domains of the ultra-small structures and ultra-fast processes continues. These developments depend crucially on yet further advancements in the production and control of high power and high frequency microwaves and light sources, often intricately coupled in their operation to the high energy beams themselves. We give a glimpse of the recent developments and innovations in the electromagnetic production and control of charged particle beams in the service of science and society. (author)

Chattopadhyay, Swapan [Universities of Lancaster, Liverpool and Manchester and Cockcroft Institute, Cheshire (United Kingdom)

2011-07-01

77

Multiple Charge State Beam Acceleration at ATLAS  

E-print Network

A test of the acceleration of multiple charge-state uranium beams was performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the tandem injector was used to tune the Booster for 238U+38. All charge states from the stripping were injected into the booster and accelerated. Up to 94% of the beam was accelerated through the Booster linac, with losses mostly in the lower charge states. The measured beam properties of each charge state and a comparison to numerical simulations are reported in this paper.

Ostroumov, P N; Zinkann, G P; Shepard, K W; Nolen, J A

2000-01-01

78

Detecting the ambient neutralino dark matter particles at accelerator  

E-print Network

In this work, we present a new strategy to investigate the possibility of direct detection of the ambient neutralino matter at accelerator. We calculate the cross sections for both elastic and inelastic scattering processes of the dark matter particles with the beam particles at $e^+e^-$ and hadron colliders.

Tai-Fu Feng; Xue-Qian Li; Wen-Gan Ma; Jian-Xiong Wang; Gong-Bo Zhao

2006-10-30

79

RFQ device for accelerating particles  

DOEpatents

A superconducting radio frequency quadrupole (RFQ) device includes four spaced elongated, linear, tubular rods disposed parallel to a charged particle beam axis, with each rod supported by two spaced tubular posts oriented radially with respect to the beam axis. The rod and post geometry of the device has four-fold rotation symmetry, lowers the frequency of the quadrupole mode below that of the dipole mode, and provides large dipole-quadrupole mode isolation to accommodate a range of mechanical tolerances. The simplicity of the geometry of the structure, which can be formed by joining eight simple T-sections, provides a high degree of mechanical stability, is insensitive to mechanical displacement, and is particularly adapted for fabrication with superconducting materials such as niobium.

Shepard, Kenneth W. (Park Ridge, IL); Delayen, Jean R. (Naperville, IL)

1995-01-01

80

The LICPA accelerator of dense plasma and ion beams  

NASA Astrophysics Data System (ADS)

Laser-induced cavity pressure acceleration (LICPA) is a novel scheme of acceleration of dense matter having a potential to accelerate plasma projectiles with the energetic efficiency much higher than the achieved so far with other methods. In this scheme, a projectile placed in a cavity is irradiated by a laser beam introduced into the cavity through a hole and accelerated along a guiding channel by the thermal pressure created in the cavity by the laser-produced plasma or by the photon pressure of the ultraintense laser radiation trapped in the cavity. This paper summarizes briefly the main results of our recent LICPA studies, in particular, experimental investigations of ion beam generation and heavy macroparticle acceleration in the hydrodynamic LICPA regime (at moderate laser intensities ~ 1015W/cm2) and numerical, particle-in-cell (PIC) studies of production of ultraintense ion beams and fast macroparticles using the photon pressure LICPA regime (at high laser intensities > 1020 W/cm2). It is shown that in both LICPA regimes the macroparticles and ion beams can be accelerated much more efficiently than in other laser-based acceleration scheme commonly used and the accelerated plasma/ion bunches can have a wide variety of parameters. It creates a prospect for a broad range of applications of the LICPA accelerator, in particular in such domains as high energy density physics, ICF research (ion fast ignition, impact ignition) or nuclear physics.

Badziak, J.; Jablo?ski, S.; Pisarczyk, T.; Chodukowski, T.; Parys, P.; Raczka, P.; Rosi?ski, M.; Krousky, E.; Ullschmied, J.; Liska, R.; Kucharik, M.; Torrisi, L.

2014-04-01

81

Frontiers of particle beam physics  

SciTech Connect

First, a review is given of various highly-developed techniques for particle handling which are, nevertheless, being vigorously advanced at the present time. These include soft superconductor radio frequency cavities, hard superconductor magnets, cooling rings for ions and anti-protons, and damping rings for electrons. Second, attention is focused upon novel devices for particle generation, acceleration, and focusing. These include relativistic klystrons and free electron laser power sources, binary power multipliers, photocathodes, switched-power linacs, plasma beat-wave accelerators, plasma wake-field accelerators, plasma lenses, plasma adiabatic focusers and plasma compensators. 12 refs.

Sessler, A.M.

1989-11-01

82

Conditional Fluid-Particle Accelerations in Turbulence  

Microsoft Academic Search

.   Simple closures for average fluid-particle accelerations, conditional on fixed local fluid velocity, are considered in isotropic,\\u000a homogeneous and stationary turbulence using exact probability density transport equations and are compared with direct numerical\\u000a simulations (DNS). Such accelerations are common ingredients in Lagrangian stochastic models for fluid-particle trajectories\\u000a in turbulence. One-particle accelerations are essentially trivial, so the focus is on two-particle

M. S. Borgas; P. K. Yeung

1998-01-01

83

Neutral particle beam distributed data acquisition system  

SciTech Connect

A distributed data acquisition system has been designed to support experiments at the Argonne Neutral Particle Beam Accelerator. The system uses a host VAXstation II/GPX computer acting as an experimenter's station linked via Ethernet with multiple MicroVAX IIs and rtVAXs dedicated to acquiring data and controlling hardware at remote sites. This paper describes the hardware design of the system, the applications support software on the host and target computers, and the real-time performance.

Daly, R.T.; Kraimer, M.R.; Novick, A.H.

1987-01-01

84

Plasma based charged-particle accelerators  

Microsoft Academic Search

Studies of charged-particle acceleration processes remain one of the most important areas of research in laboratory, space and astrophysical plasmas. In this paper, we present the underlying physics and the present status of high gradient and high energy plasma accelerators. We will focus on the acceleration of charged particles to relativistic energies by plasma waves that are created by intense

R Bingham; J T Mendonça; P K Shukla

2004-01-01

85

Challenges in plasma and laser wakefield accelerated beams diagnostic  

NASA Astrophysics Data System (ADS)

The new frontier in the particle beam accelerator is the so called plasma acceleration. Using the strong electric field inside a plasma it is possible to achieve accelerating gradients in the order of magnitude larger with respect to the actual technologies. Different schemes have been proposed and several already tested, producing beams of energy of several GeV. Mainly two approaches are followed: either the beam is directly produced by the interaction of a TW/PW class laser with a gas jet or a preexisting particle beam is accelerated in a plasma channel. In both cases a precise determination of the emerging beam parameters is mandatory for the fine tuning of the devices. The measurement of these parameters, in particular the emittance, 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 show the problems related to the diagnostic of this kind of beams and the proposed or already realized solutions.

Cianchi, A.; Anania, M. P.; Bellaveglia, M.; Castellano, M.; Chiadroni, E.; Ferrario, M.; Gatti, G.; Marchetti, B.; Mostacci, A.; Pompili, R.; Ronsivalle, C.; Rossi, A. R.; Serafini, L.

2013-08-01

86

"Accelerators and beams," a multimedia tutorial  

NASA Astrophysics Data System (ADS)

We are developing a computer-based tutorial for charged-particle beam optics under a grant from the DOE. This subject is important to the DOE not only for its use in providing basic research tools but because the physics is the underpinning for accelerators used in industry and medicine. The tutorial, which will be delivered on Macintosh and Windows platforms, uses multimedia techniques to enhance the student's rate of learning and length of retention of the material. As such, it integrates our interactive On-Screen Laboratories™ with hypertext, line drawings, photographs, animation, video, and sound. We are targeting an audience from technicians to graduate students in science and engineering. At this time we have about a fourth of the material (about equivalent to a one-semester three-credit-hour upper under-graduate physics course) available in prototype form.

Silbar, Richard R.

1997-02-01

87

Interstellar Flight by Particle Beam  

NASA Technical Reports Server (NTRS)

Two difficulties with the use of laser-propelled lightsails for interstellar propulsion are the extremely low energy efficiency, and the extremely large lenses required. Both the energy efficiency and the required lens size may be greatly improved by use of a particle beam, rather than a light beam. The particle beam is reflected by a magnetic field on the spacecraft, for example, by a magnetic sail or a mini-magnetosphere inflated by a plasma current. This results in a net force on the sail with no expenditure of propellant, allowing extremely high delta-V missions, such as an interstellar probe, to be accomplished.

Landis, Geoffrey A.

2001-01-01

88

How to obtain particles to accelerate  

NSDL National Science Digital Library

Where do the particles come from that are accelerated in a particle accelerator? In this portion of a particle physics tutorial, three sources of particles are described for students. The first source is electrons, which come from heated metals. The second is protons, which are available from ionized hydrogen. Antiparticles are the third source. They are collected by magnetic fields after particles smash targets. Copyright 2005 Eisenhower National Clearinghouse

Group, Lawrence B.

2002-01-01

89

Fundamentals of relativistic particle beam optics  

SciTech Connect

This lecture introduces the nonaccelerator-specialist to the motion of charged particles in a Storage Ring. The topics of discussion are restricted to the linear and nonlinear dynamics of a single particle in the transverse plane, i.e., the plane perpendicular to the direction of motion. The major omissions for a complete review of accelerator theory, for which a considerable literature exists, are the energy and phase oscillations (1). Other important accelerator physics aspects not treated here are the collective instabilities (2), the role of synchrotron radiation in electron storage rings (3), scattering processes (4), and beam-beam effects in colliding beam facilities (5). Much of the discussion that follows applies equally well to relativistic electron, proton, or ion synchrotrons. In this narrative, we refer to the particle as electron. After a broad overview, the magnetic forces acting on the electrons and the associated differential equations of motion are discussed. Solutions of the equations are given without derivation; the method of solution is outlined. and references for deeper studies are given. In this paper, the word electron is used to signify electron or positron. The dynamics of a single particle are not affected by the sign of its charge when the magnetic field direction is changed accordingly.

Cornacchia, M.

1995-12-01

90

RESOLVING BEAM TRANSPORT PROBLEMS IN ELECTROSTATIC ACCELERATORS  

E-print Network

. OPTICS, POLARIZED SOURCES, PULSING, MISCELLANEOUS. 1. Introduction. - What constitutes a problem in beam and to demonstrate again how potent is the lens effect at the entrance to an open acceleration tube. During studies

Boyer, Edmond

91

Pointing of laser-accelerated proton beams  

SciTech Connect

Small fluctuations in the acceleration sheath change the pointing of a proton beam accelerated from the rear side of a laser irradiated thin aluminum foil. The proton acceleration was produced with 40 fs pulses of a Ti:sapphire laser at an intensity of approximately 10{sup 19} W/cm{sup 2}. This observation has been made with a high spatial resolution Thomson spectrometer. The proton beam pointing has appeared stable in the energy range between the high energy cutoff (3 MeV) and 50% of this value. Deviations of the beam position at lower energies changes in a range of 0-3 mrad. The recorded pictures show wiggled and continuous proton traces which imply a release of the proton beam from the acceleration zone with a velocity chirp.

Schreiber, J.; Ter-Avetisyan, S.; Risse, E.; Kalachnikov, M.P.; Nickles, P.V.; Sandner, W.; Schramm, U.; Habs, D.; Witte, J.; Schnuerer, M. [MPI fuer Quantenoptik, Hans-Kopfermann-Str. 1, D 85748 Garching (Germany) and LMU Muenchen, Am Coulombwall 1, D 85748, Garching (Germany); Max Born Institut, Max Born Strasse 2a, D 12489 Berlin (Germany); Max Born Institut, Max Born Strasse 2a, D 12489 Berlin (Germany) and TU Berlin, Strasse des 17. Juni 135, D 10623 Berlin (Germany); LMU Muenchen, Am Coulombwall 1, D 85748, Garching (Germany); MPI fuer Quantenoptik, Hans-Kopfermann-Str. 1, D 85748 Garching (Germany); Max Born Institut, Max Born Strasse 2a, D 12489 Berlin (Germany)

2006-03-15

92

Beam Coupling to Optical Scale Accelerating Structures  

SciTech Connect

Current research efforts into structure based laser acceleration of electrons utilize beams from standard RF linacs. These beams must be coupled into very small structures with transverse dimensions comparable to the laser wavelength. To obtain decent transmission, a permanent magnet quadrupole (PMQ) triplet with a focusing gradient of 560 T/m is used to focus into the structure. Also of interest is the induced wakefield from the structure, useful for diagnosing potential accelerator structures or as novel radiation sources.

Sears, C.M.; Byer, R.L.; Colby, E.R.; Cowan, B.M.; Ischebeck, R.; Lincoln, M.R.; Siemann, R.H.; Spencer, J.E.; /SLAC; Plettner, T.; /Stanford U., Phys. Dept.

2007-03-27

93

Relativistic particle acceleration in plerions  

NASA Technical Reports Server (NTRS)

We discuss recent research on the structure and particle acceleration properties of relativistic shock waves in which the magnetic field is transverse to the flow direction in the upstream medium, and whose composition is either pure electrons and positrons or primarily electrons and positrons with an admixture of heavy ions. Particle-in-cell simulation techniques as well as analytic theory have been used to show that such shocks in pure pair plasmas are fully thermalized -- the downstream particle spectra are relativistic Maxwellians at the temperature expected from the jump conditions. On the other hand, shocks containing heavy ions which are a minority constituent by number but which carry most of the energy density in the upstream medium do put approximately 20% of the flow energy into a nonthermal population of pairs downstream, whose distribution in energy space is N(E) varies as E(exp -2), where N(E)dE is the number of particles with energy between E and E+dE. The mechanism of thermalization and particle acceleration is found to be synchrotron maser activity in the shock front, stimulated by the quasi-coherent gyration of the whole particle population as the plasma flowing into the shock reflects from the magnetic field in the shock front. The synchrotron maser modes radiated by the heavy ions are absorbed by the pairs at their (relativistic) cyclotron frequencies, allowing the maximum energy achievable by the pairs to be gamma(sub +/-)m(sub +/-)c squared = m(sub i)c squared gamma(sub 1)/Z(sub i), where gamma(sub 1) is the Lorentz factor of the upstream flow and Z(sub i) is the atomic number of the ions. The shock's spatial structure is shown to contain a series of 'overshoots' in the magnetic field, regions where the gyrating heavy ions compress the magnetic field to levels in excess of the eventual downstream value. This shock model is applied to an interpretation of the structure of the inner regions of the Crab Nebula, in particular to the 'wisps,' surface brightness enhancements near the pulsar. We argue that these surface brightness enhancements are the regions of magnetic overshoot, which appear brighter because the small Larmor radius pairs are compressed and radiate more efficiently in the regions of more intense magnetic field. This interpretation suggests that the structure of the shock terminating the pulsar's wind in the Crab Nebula is spatially resolved, and allows one to measure gamma(sub 1) and a number of other properties of the pulsar's wind. We also discuss applications of the shock theory to the termination shocks of the winds from rotation-powered pulsars embedded in compact binaries. We show that this model adequately accounts for (and indeed predicted) the recently discovered X-ray flux from PSR 1957+20, and we discuss several other applications to other examples of these systems.

Arons, Jonathan; Tavani, Marco

1994-01-01

94

ELECTROMAGNETIC SIMULATIONS OF DIELECTRIC WALL ACCELERATOR STRUCTURES FOR ELECTRON BEAM ACCELERATION  

SciTech Connect

Dielectric Wall Accelerator (DWA) technology incorporates the energy storage mechanism, the switching mechanism, and the acceleration mechanism for electron beams. Electromagnetic simulations of DWA structures includes these effects and also details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. DWA structures include both bi-linear and bi-spiral configurations with field gradients on the order of 20MV/m and the simulations include the effects of the beampipe, the beampipe walls, the DWA High Gradient Insulator (HGI) insulating stack, wakefield impedance calculations, and test particle trajectories with low emittance gain. Design trade-offs include the transmission line impedance (typically a few ohms), equilibration ring optimization, driving switch inductances, and layer-to-layer coupling effects and the associated affect on the acceleration pulse's peak value.

Nelson, S D; Poole, B R

2005-05-05

95

Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude  

DOEpatents

A beam current limiter is disclosed for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity. 6 figs.

Bogaty, J.M.; Clifft, B.E.; Bollinger, L.M.

1995-08-08

96

Generalized Radially Self-Accelerating Helicon Beams  

NASA Astrophysics Data System (ADS)

We report, in theory and experiment, on a new class of optical beams that are radially self-accelerating and nondiffracting. These beams continuously evolve on spiraling trajectories while maintaining their amplitude and phase distribution in their rotating rest frame. We provide a detailed insight into the theoretical origin and characteristics of radial self-acceleration and prove our findings experimentally. As radially self-accelerating beams are nonparaxial and a solution to the full scalar Helmholtz equation, they can be implemented in many linear wave systems beyond optics, from acoustic and elastic waves to surface waves in fluids and soft matter. Our work generalized the study of classical helicon beams to a complete set of solutions for rotating complex fields.

Vetter, Christian; Eichelkraut, Toni; Ornigotti, Marco; Szameit, Alexander

2014-10-01

97

Solitary waves in particle beams  

SciTech Connect

Since space charge waves on a particle beam exhibit both dispersive and nonlinear character, solitary waves or solitons are possible. Dispersive, nonlinear wave propagation in high current beams is found to be similar to ion-acoustic waves in plasmas with an analogy between Debye screening and beam pipe shielding. Exact longitudinal solitary wave propagation is found for potentials associated with certain transverse distributions which fill the beam pipe. For weak dispersion, the waves satisfy the Korteweg-deVries (KdV) equation, but for strong dispersion they exhibit breaking. More physically realizable distributions which do not fill the beam pipe are investigated and shown to also satisfy a KdV equation for weak dispersion if averaging over rapid transverse motion is physically justified. Scaling laws are presented to explore likely parameter regimes where these phenomena may be observed experimentally.

Bisognano, J.J. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

1996-07-01

98

Particle acceleration at a reconnecting magnetic separator  

E-print Network

While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. The effect upon particle behaviour of initial position, pitch angle and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains ...

Threlfall, J; Parnell, C E; Oskoui, S Eradat

2014-01-01

99

The appreciation of stochastic motion in particle accelerators  

SciTech Connect

A description is given of the analytic and numerical work, performed from July 1955 through August 1956, so as to develop, and then study, the process of making intense proton beams, suitable for colliding beams. It is shown how this investigation led, in a most natural way, to the realization that stochasticity can arise in a simple Hamiltonian system. Furthermore, the criterion for the onset of stochasticity was understood, and carefully studied, in two different situations. The first situation was the proposed (and subsequently used) ''stacking process'' for developing an intense beam, where stochasticity occurs as additional particles are added to the intense circulating beam. The second situation occurs when one seeks to develop ''stochastic accelerators'' in which particles are accelerated (continuously) by a collection of radio frequency systems. It was in the last connection that the well-known criterion for stochasticity, resonance overlap, was obtained.

Symon, Keith; Sessler, Andrew

2003-08-03

100

Type II radio bursts and particle acceleration  

Microsoft Academic Search

328 particle events recorded during 30 months from January 1, 1966 to June 30, 1968 (taken from the new Catalog of Solar Particle Events, 1955–1969) are compared with the occurrence of 166 type II radio bursts during the same period. The results of this comparison give a convincing evidence that proton acceleration to higher energies in flares (the ‘second acceleration

Z. Švestka; L. Fritzová-Svestková

1974-01-01

101

Particle acceleration in colliding wind binary systems  

Microsoft Academic Search

We present a new model for the particle acceleration believed to power the synchrotron emission observed in some Wolf-Rayet binaries. Particles are accelerated in a current sheet formed when the magnetic fields carried in the winds of the two stars are forced together as the winds collide. By modelling this current sheet we are able to determine, for a given

M. Jardine; H. R. Allen; A. M. T. Pollock

1996-01-01

102

Random Dielectric Photonic Structures for Accelerating Particles  

Microsoft Academic Search

We investigate the applicability of random dielectric photonic structures to particle acceleration. Electromagnetic waves trapped within photonic crystal cavities can be used to accelerate charged particles. Whereas metallic cavities support higher harmonics, cavities in dielectric photonic crystals limit trapped oscillations to a frequency range within the bandgap of the surrounding crystal. This allows the cavity to contain only one frequency

C. A. Bauer; J. R. Cary; G. R. Werner

2006-01-01

103

Introduction to Particle Acceleration in the Cosmos  

NASA Technical Reports Server (NTRS)

Accelerated charged particles have been used on Earth since 1930 to explore the very essence of matter, for industrial applications, and for medical treatments. Throughout the universe nature employs a dizzying array of acceleration processes to produce particles spanning twenty orders of magnitude in energy range, while shaping our cosmic environment. Here, we introduce and review the basic physical processes causing particle acceleration, in astrophysical plasmas from geospace to the outer reaches of the cosmos. These processes are chiefly divided into four categories: adiabatic and other forms of non-stochastic acceleration, magnetic energy storage and stochastic acceleration, shock acceleration, and plasma wave and turbulent acceleration. The purpose of this introduction is to set the stage and context for the individual papers comprising this monograph.

Gallagher, D. L.; Horwitz, J. L.; Perez, J.; Quenby, J.

2005-01-01

104

Particle acceleration in relativistic laser channels  

Microsoft Academic Search

Energy spectra of ions and fast electrons accelerated by a channeling laser pulse in near-critical plasma are studied using three-dimensional (3D) Particle-In-Cell simulations. The realistic 3D geometry of the simulations allows us to obtain not only the shape of the spectra, but also the absolute numbers of accelerated particles. It is shown that ions are accelerated by a collisionless radial

A. Pukhov; Z.-M. Sheng; J. Meyer-Ter-Vehn

1999-01-01

105

Particle Accelerators Test Cosmological Theory.  

ERIC Educational Resources Information Center

Discusses the symbiotic relationship of cosmology and elementary-particle physics. Presents a brief overview of particle physics. Explains how cosmological considerations set limits on the number of types of elementary particles. (RT)

Schramm, David N.; Steigman, Gary

1988-01-01

106

Hydrodynamic Penetration of High Power Particle Beams  

NASA Astrophysics Data System (ADS)

A high power particle beam that dwells on a target can produce hydrodynamic effects if the energy deposition exceeds a threshold needed to vaporize the target (typically a few kJ/g). If lateral hydrodynamic expansion causes decompression during the pulse, the beam can penetrate much farther than expected. By combining the MARS energy deposition code with 2- and 3-D hydrodynamic codes (MESA and SPHINX) we have calculated the effects of high power beams in abnormal situations. A 20 TeV proton beam with ?_x=?_y=2 mm, 4×10^14 ppp, 290?s,which strikes the face of a 4×7×800 cm graphite block, simulating a beam dump, creates a hole that expands laterally at 0.02cm/?s and longitudinally at 10cm/?s . If the beam is scanned across the face of the block at >=1mm/?s the beam moves into fresh material fast enough that there is no additional penetration beyond the static range. Proton interactions with a scraper were simulated with a ?_x=?_y=0.2 mm beam propagating 1 or 2? from a steel slab. A low density groove propagates parallel to the beam in the steel at about 60cm/?s, creating temperatures of 7000^circC and pressures of 25 kbar. Simulation of a superconducting magnet section produces similar temperatures and densities in the blowoff. Energy deposition in the superconducting coils reaches 25 J/g by 6?s and the beam tube reaches 1500^circC. These calculations illucidate abnormal scenarios to be avoided in accelerator design.

Wilson, D. C.; Goldstein, J. C.; Wingate, C. A.; Godwin, R. P.; Mokhov, N. V.

1998-04-01

107

Advanced visualization technology for terascale particle accelerator simulations  

Microsoft Academic Search

This paper presents two new hardware-assisted rendering techniques developed for interactive visualization of the terascale data generated from numerical modeling of next-generation accelerator designs. The first technique, based on a hybrid rendering approach, makes possible interactive exploration of large-scale particle data from particle beam dynamics modeling. The second technique, based on a compact texture-enhanced representation, exploits the advanced features of

Kwan-Liu Ma; Gregory L. Schussman; Brett Wilson; Kwok Ko; Ji Qiang; Robert Ryne

2002-01-01

108

Beam Head Erosion in Self-Ionized Plasma Wakefield Accelerators  

SciTech Connect

In the recent plasma wakefield accelerator experiments at SLAC, the energy of the particles in the tail of the 42 GeV electron beam were doubled in less than one meter [1]. Simulations suggest that the acceleration length was limited by a new phenomenon--beam head erosion in self-ionized plasmas. In vacuum, a particle beam expands transversely in a distance given by {beta}*. In the blowout regime of a plasma wakefield [2], the majority of the beam is focused by the ion channel, while the beam head slowly spreads since it takes a finite time for the ion channel to form. It is observed that in self-ionized plasmas, the head spreading is exacerbated compared to that in pre-ionized plasmas, causing the ionization front to move backward (erode). A simple theoretical model is used to estimate the upper limit of the erosion rate for a bi-gaussian beam by assuming free expansion of the beam head before the ionization front. Comparison with simulations suggests that half this maximum value can serve as an estimate for the erosion rate. Critical parameters to the erosion rate are discussed.

Berry, M.K.; Blumenfeld, I.; Decker, F.J.; Hogan, M.J.; Ischebeck, R.; Iverson, R.H.; Kirby, N.A.; Siemann, Robert H.; Walz, D.R.; /SLAC; Clayton, C.E.; Huang, C.; Joshi, C.; Lu, W.; Marsh, K.A.; Mori, W.B.; Zhou, M.; /UCLA; Katsouleas, T.C.; Muggli, P.; Oz, E.; /Southern California U.

2008-01-28

109

Acceleration of particles in imbalanced magnetohydrodynamic turbulence.  

PubMed

The present work investigates the acceleration of test particles, relevant to the solar-wind problem, in balanced and imbalanced magnetohydrodynamic turbulence (terms referring here to turbulent states possessing zero and nonzero cross helicity, respectively). These turbulent states, obtained numerically by prescribing the injection rates for the ideal invariants, are evolved dynamically with the particles. While the energy spectrum for balanced and imbalanced states is known, the impact made on particle heating is a matter of debate, with different considerations giving different results. By performing direct numerical simulations, resonant and nonresonant particle accelerations are automatically considered and the correct turbulent phases are taken into account. For imbalanced turbulence, it is found that the acceleration rate of charged particles is reduced and the heating rate diminished. This behavior is independent of the particle gyroradius, although particles that have a stronger adiabatic motion (smaller gyroradius) tend to experience a larger heating. PMID:25215682

Teaca, Bogdan; Weidl, Martin S; Jenko, Frank; Schlickeiser, Reinhard

2014-08-01

110

Feature-based analysis of plasma-based particle acceleration data.  

PubMed

Plasma-based particle accelerators can produce and sustain thousands of times stronger acceleration fields than conventional particle accelerators, providing a potential solution to the problem of the growing size and cost of conventional particle accelerators. To facilitate scientific knowledge discovery from the ever growing collections of accelerator simulation data generated by accelerator physicists to investigate next-generation plasma-based particle accelerator designs, we describe a novel approach for automatic detection and classification of particle beams and beam substructures due to temporal differences in the acceleration process, here called acceleration features. The automatic feature detection in combination with a novel visualization tool for fast, intuitive, query-based exploration of acceleration features enables an effective top-down data exploration process, starting from a high-level, feature-based view down to the level of individual particles. We describe the application of our analysis in practice to analyze simulations of single pulse and dual and triple colliding pulse accelerator designs, and to study the formation and evolution of particle beams, to compare substructures of a beam, and to investigate transverse particle loss. PMID:24356363

Rübel, Oliver; Geddes, Cameron G R; Chen, Min; Cormier-Michel, Estelle; Bethel, E Wes

2014-02-01

111

Frequency multiplying oscillator with an electron beam accelerated in a drift space  

SciTech Connect

In a uniform acceleration region, the behavior of a velocity-modulated electron beam has been analyzed using a particle-in-cell code. By making use of one of the accelerated harmonic components of the velocity-modulated electron beam, we demonstrate a frequency multiplying oscillator for a compact THz emitter, which employs multiple electron beams and a higher order mode resonator to modulate the electron beam without an additional driving source.

Jang, Kyu-Ha; Lee, Kitae; Hee Park, Seong; Uk Jeong, Young [WCI Center for Quantum Beam-based Radiation Research, Korea Atomic Energy Research Institute, 1045 Deadeok, Yuseong, Daejeon 305-353 (Korea, Republic of); Miginsky, S. [WCI Center for Quantum Beam-based Radiation Research, Korea Atomic Energy Research Institute, 1045 Deadeok, Yuseong, Daejeon 305-353 (Korea, Republic of); Budker Institute of Nuclear Physics, SB RAS, Academician Lavrentyev St. 11, Novosibrisk (Russian Federation)

2012-07-02

112

Accelerating diffraction-free beams in photonic lattices.  

PubMed

We study nondiffracting accelerating paraxial optical beams in periodic potentials, in both the linear and the nonlinear domains. In particular, we show that only a unique class of z-dependent lattices can support a true accelerating diffractionless beam. Accelerating lattice solitons, autofocusing beams and accelerating bullets in optical lattices are systematically examined. PMID:24686692

Makris, K G; Kaminer, I; El-Ganainy, R; Efremidis, N K; Chen, Zhigang; Segev, M; Christodoulides, D N

2014-04-01

113

Capture and Control of Laser-Accelerated Proton Beams: Experiment and Simulation  

SciTech Connect

This paper summarizes the ongoing studies on the possibilities for transport and RF capture of laser-accelerated proton beams in conventional accelerator structures. First results on the capture of laser-accelerated proton beams are presented, supported by Trace3D, CST particle studio and Warp simulations. Based on these results, the development of the pulsed high-field solenoid is guided by our desire to optimize the output particle number for this highly divergent beam with an exponential energy spectrum. A future experimental test stand is proposed to do studies concerning the application as a new particle source.

Nurnberg, F; Alber, I; Harres, K; Schollmeier, M; Roth, M; Barth, W; Eickhoff, H; Hofmann, I; Friedman, A; Grote, D; Logan, B G

2009-05-13

114

Study of space charge compensation phenomena in charged particle beams.  

PubMed

The propagation of a charged particle beam is accompanied by the production of secondary particles created in the interaction of the beam itself with the background gas flowing in the accelerator tube. In the drift region, where the electric field of the electrodes is negligible, secondary particles may accumulate giving a plasma which shields the self-induced potential of the charged beam. This phenomenon, known as space charge compensation is a typical issue in accelerator physics, where it is usually addressed by means of 1D radial transport codes or Monte Carlo codes. The present paper describes some theoretical studies on this phenomenon, presenting a Particle in Cell-Monte Carlo (PIC-MC) Code developed ad hoc where both radial and axial confinements of secondary particles are calculated. The features of the model, offering a new insight on the problem, are described and some results discussed. PMID:22380314

Veltri, P; Cavenago, M; Serianni, G

2012-02-01

115

Annular Cherenkov High Gradient Wakefield Accelerator: Beam-Breakup Analysis and Energy Transfer Efficiency  

NASA Astrophysics Data System (ADS)

In this paper, we give a complete analytical solution for Cherenkov wakefields generated by an azimuthally asymmetric annular beam propagating in a coaxial two-channel dielectric structure. The transformer ratio of this type of structure is dramatically increased in comparison to a cylindrical wakefield accelerating structure. A particle-Green's function beam dynamics code (BBU-3000) to study beam breakup effects has been upgraded to incorporate annular drive beams and coaxial dielectric wakefield accelerating structures. Beam dynamics simulations of the annular drive beam with asymmetric charge distributions have been carried out to determine the sensitivity of this method to beam imperfections.

Altmark, A. M.; Kanareykin, A. D.

2012-05-01

116

Accelerators for heavy-charged-particle radiation therapy.  

PubMed

This paper focuses on current and future designs of medical hadron accelerators for treating cancers and other diseases. Presently, five vendors and several national laboratories have produced heavy-particle medical accelerators for accelerating nuclei from hydrogen (protons) up through carbon and oxygen. Particle energies are varied to control the beam penetration depth in the patient. As of the end of 2006, four hospitals and one clinic in the United States offer proton treatments; there are five more such facilities in Japan. In most cases, these facilities use accelerators designed explicitly for cancer treatments. The accelerator types are a combination of synchrotrons, cyclotrons, and linear accelerators; some carry advanced features such as respiration gating, intensity modulation, and rapid energy changes, which contribute to better dose conformity on the tumor when using heavy charged particles. Recent interest in carbon nuclei for cancer treatment has led some vendors to offer carbon-ion and proton capability in their accelerator systems, so that either ion can be used. These features are now being incorporated for medical accelerators in new facilities. PMID:17668952

Coutrakon, George B

2007-08-01

117

Solar particle acceleration and propagation  

Microsoft Academic Search

Experimental and theoretical results concerning the acceleration of solar radiation are reviewed. Different types of radiations are considered separately including neutrons, electrons, gamma rays, and He-rich events. (AIP)

R. P. Lin

1987-01-01

118

Twisted waveguides for particle accelerator applications  

E-print Network

A novel microwave device for accelerating charged particles based on twisted waveguide is presented. Twisted guides support slow-wave TM modes whose phase velocity could reach the speed of light c. The axial electric field ...

Wilson, Joshua L.

119

Harmonic Ratcheting for Ferrite Tuned RF Acceleration of Charged Particles  

NASA Astrophysics Data System (ADS)

One of the most persistent difficulties in the design of RF cavities for acceleration of charged particles is the rapid and efficient acceleration of particles over a large range of frequencies. From medical synchrotrons to accelerator driven systems, there is a strong need for fast acceleration of protons and light ions over hundreds of MeV. Conventionally, this is a costly undertaking, requiring specially designed ferrite loaded cavities to be tuned over a large range of frequencies. Ferromagnetic materials allow for the precise adjustment of cavity resonant frequency, but rapid changes in the frequency as well as operation outside material specific frequency ranges result in significant Q-loss to the cavity. This leads to a considerable increase in power required and is thus undesirable for regular operation. We introduce an acceleration scheme known as harmonic ratcheting which can be used to reduce the cavity frequency range needed for accelerating an ion beam in a synchrotron. In particular, this scheme addresses the need for high rep. rate machines for applications such as radiation therapy in which low beam intensity is needed. We demonstrate with simulations the type of ramps achievable using this technique and consider its advantages over h=1 acceleration schemes.

Cook, Nathan; Brennan, Mike

2013-04-01

120

Optical Diagnostics for Plasma-based Particle Accelerators  

NASA Astrophysics Data System (ADS)

One of the challenges for plasma-based particle accelerators is to measure the spatio-temporal characteristics of the accelerated particle bunch. ``Optical'' diagnostics are particularly interesting and useful because of the large number of techniques that exits to determine the properties of photon pulses. The accelerated bunch can produce photons pulses that carry information about its characteristics for example through synchrotron radiation in a magnet, Cherenkov radiation in a gas, and transition radiation (TR) at the boundary between two media with different dielectric constants. Depending on the wavelength of the emission when compared to the particle bunch length, the radiation can be incoherent or coherent. Incoherent TR in the optical range (or OTR) is useful to measure the transverse spatial characteristics of the beam, such as charge distribution and size. Coherent TR (or CTR) carries information about the bunch length that can in principle be retrieved by standard auto-correlation or interferometric techniques, as well as by spectral measurements. A measurement of the total CTR energy emitted by bunches with constant charge can also be used as a shot-to-shot measurement for the relative bunch length as the CTR energy is proportional to the square of the bunch population and inversely proportional to its length (for a fixed distribution). Spectral interferometry can also yield the spacing between bunches in the case where multiple bunches are trapped in subsequent buckets of the plasma wave. Cherenkov radiation can be used as an energy threshold diagnostic for low energy particles. Cherenkov, synchrotron and transition radiation can be used in a dispersive section of the beam line to measure the bunch energy spectrum. The application of these diagnostics to plasma-based particle accelerators, with emphasis on the beam-driven, plasma wakefield accelerator (PWFA) at the SLAC National Accelerator Laboratory will be discussed.

Muggli, Patric

2009-05-01

121

On-line system identification for control system applications in particle accelerators  

Microsoft Academic Search

Particle accelerators require a number of feedback systems in order to stabilize a variety of parameters. The Continuous Electron Beam Accelerator at Thomas Jefferson National Accelerator Facility presents a unique set of control and identification problems. This accelerator produces a continuous electron beam with energies between 0.5 and 4.0 GeV to be delivered to the experimental halls. In order to

Mahesh Chowdhary

1997-01-01

122

Experimental Measurements of the Secondary Electron Yield in the Experimental Measurement of the Secondary Electron Yield in the PEP-II Particle Accelerator Beam Line  

SciTech Connect

Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders (LC) such as ILC and CLIC. To test a series of promising possible electron cloud mitigation techniques as surface coatings and grooves, in the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed several test vacuum chambers including (i) a special chamber to monitor the variation of the secondary electron yield of technical surface materials and coatings under the effect of ion, electron and photon conditioning in situ in the beam line; (ii) chambers with grooves in a straight magnetic-free section; and (iii) coated chambers in a dedicated newly installed 4-magnet chicane to study mitigations in a magnetic field region. In this paper, we describe the ongoing R&D effort to mitigate the electron cloud effect for the LC damping ring, focusing on the first experimental area and on results of the reduction of the secondary electron yield due to in situ conditioning.

Pivi, M.T.F.; Collet, G.; King, F.; Kirby, R.E.; Markiewicz, T.; Raubenheimer, T.O.; Seeman, J.; /SLAC; Le Pimpec, F.; /PSI, Villigen

2010-08-25

123

Single particle dynamics in circular accelerators  

SciTech Connect

The purpose of this paper is to introduce the reader to the theory associated with the transverse dynamics of single particle, in circular accelerators. The discussion begins with a review of Hamiltonian dynamics and canonical transformations. The case of a single particle in a circular accelerator is considered with a discussion of non-linear terms and chromaticity. The canonical perturbation theory is presented and nonlinear resonances are considered. Finally, the concept of renormalization and residue criterion are examined. (FI)

Ruth, R.D.

1986-10-01

124

Accelerating and storing polarized hadron beams  

SciTech Connect

Polarization hadron experiments at high energies continue to generate surprises. Many questions remain unanswered or unanswerable within the frame work of QCD. These include such basic questions as to why at high energies the polarization analyzing power in pp elastic scattering remains high, why hyperons are produced with high polarizations etc. It is, therefore, interesting to investigate the possibilities of accelerating and storing polarized beams in high energy colliders. On the technical side the recent understanding and confirmation of the actions of partial and multiple Siberian snakes made it possible to contemplate accelerating and storing polarized hadron beams to multi-TeV energies. In this paper, we will examine the equipment, the operation and the procedure required to obtain colliding beams of polarized protons at TeV energies.

Teng, L.C.

1990-10-01

125

GeV electron beams from a centimetre-scale accelerator  

E-print Network

GeV electron beams from a centimetre-scale accelerator W. P. LEEMANS1 * , B. NAGLER1 , A. JV) electron accelerators are essential to synchrotron radiation facilities and free-electron lasers, and as modules for high-energy particle physics. Radiofrequency-based accelerators are limited to relatively low

Geddes, Cameron Guy Robinson

126

A monolithic relativistic electron beam source based on a dielectric laser accelerator structure  

SciTech Connect

Work towards a monolithic device capable of producing relativistic particle beams within a cubic-centimeter is detailed. We will discuss the Micro-Accelerator Platform (MAP), an optical laser powered dielectric accelerator as the main building block of this chip-scale source along with a field enhanced emitter and a region for sub-relativistic acceleration.

McNeur, Josh; Carranza, Nestor; Travish, Gil; Yin Hairong; Yoder, Rodney [UCLA Dept. of Physics and Astronomy, Los Angeles, CA 90095 (United States); College of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054 (China); Manhattanville College, Physics Dept., 2900 Purchase St., Purchase, NY 10577 (United States)

2012-12-21

127

The United States Particle Accelerator School: Educating the next generation of accelerator scientists and engineers  

SciTech Connect

Only a handful of universities in the US offer any formal training in accelerator science. The United States Particle Accelerator School (USPAS) is National Graduate Educational Program that has developed a highly successful educational paradigm that, over the past twenty-years, has granted more university credit in accelerator / beam science and technology than any university in the world. Sessions are held twice annually, hosted by major US research universities that approve course credit, certify the USPAS faculty, and grant course credit. The USPAS paradigm is readily extensible to other rapidly developing, crossdisciplinary research areas such as high energy density physics.

Barletta, William A.; /MIT

2008-09-01

128

Early experiments in charged particle beams from the Space Shuttle  

NASA Technical Reports Server (NTRS)

Characteristics of studies on board the Shuttle involving the interaction of particle beams with the atmosphere and the ionosphere, and the effects of the beams on the electrical potential of the platform, are discussed. Noting that the Shuttle allows greater weight and power demands by scientific payloads than previous satellite launches, the OSS-1 Vehicle Charging and Potential experiment and the Spacelab 1 Particle Accelerator and Phenomena Induced by Charged Particle Beams are described. Instrumentation details are provided, including charge and current probes, the Spherical Retarding Potential Analyzer, the Fast Pulse Electron Generator, and digital control and interface units. The SEPAC equipment, which comprises an electron beam accelerator, and MPD plasma jet, and diagnostic units are detailed, and operating procedures and experiment objectives are outlined.

Raitt, W. J.; Banks, P. M.; Williamson, P. R.; Baker, K. D.; Obayashi, T.; Burch, J. L.

1982-01-01

129

Accelerator column models for low-current beams  

SciTech Connect

This paper describes three analytic approaches used to model electrostatic accelerator columns in beam-transport codes for low-current beams and compares the results of each approach with the results obtained by numerically calculating the electric field based on charge distribution on equipotential surfaces. The three analytic approaches described are (1) a cubic energy-gain approximation, (2) a cubic longitudinal electric-field approximation, and (3) the aperture equation. The first two approaches calculate impulse approximations at the apertures, whereas the third is an integration of particle trajectories through the column filed. The conditions under which the solutions tend to break down are discussed. 4 refs., 8 figs.

Rusthoi, D.P.; Allison, P.; Crandall, K.R.

1985-01-01

130

Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers  

DOEpatents

A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations (dB/dt) in the particle beam.

Danby, G.T.; Jackson, J.W.

1990-03-19

131

Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers  

DOEpatents

A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations in the particle beam.

Danby, Gordon T. (Wading River, NY); Jackson, John W. (Shoreham, NY)

1991-01-01

132

Applications of particle accelerators in medicine.  

PubMed

There are nearly 20,000 particle accelerators in operation worldwide, about half of them employed for biomedical uses. This paper focuses on some recent advances in the two main medical domains where accelerators find their use, radionuclide production and radiation therapy. The paper first discusses the use of high-energy electron and proton accelerators for the potential, future production of (99)Mo, which is presently provided by fission reactors. Next, it reviews the rationale for the use of protons and carbon ions in cancer therapy, discussing the requirements imposed on accelerator technology and looking at some recent developments. PMID:21676897

Silari, Marco

2011-07-01

133

Lie Algebraic Methods for Particle Accelerator Theory  

Microsoft Academic Search

The problem of determining charged particle behavior in electromagnetic fields falls within the realm of Hamiltonian dynamics. Consequently, the motion of a charged particle in an accelerator is amenable to description using a variety of the mathematical structures inherent to a Hamiltonian system. Amongst the most useful of these are a hierarchy of Lie algebras and Lie groups defined via

David Ross Douglas

1982-01-01

134

Particle Acceleration by Shocks in Supernova Remnants  

NASA Astrophysics Data System (ADS)

Particle acceleration occurs on a range of scales from AU in the heliosphere to Mpc in clusters of galaxies and to energies ranging from MeV to exaelectronvolt (EeV). A number of acceleration processes have been proposed, but diffusive shock acceleration (DSA) is widely invoked as the predominant mechanism. DSA operates on all these scales and probably to the highest energies. DSA is simple, robust and predicts a universal spectrum. However, there are still many unknowns regarding particle acceleration. This paper focuses on the particular question of whether supernova remnants (SNR) can produce the Galactic cosmic ray (CR) spectrum up to the knee at a few petaelectronvolt (PeV). The answer depends in large part on the detailed physics of diffusive shock acceleration.

Bell, Anthony Raymond

2014-10-01

135

Characterization Of A Wakefield Accelerated Electron Beam  

NASA Astrophysics Data System (ADS)

With the advancement of femtosecond Terawatt lasers, there has been great interest in their ability of accelerating electrons to high energy within short distances; this effect originating from the GeV/cm gradient created in the plasma (compared to conventional RF systems). We report on new experimental results obtained from a 400 fs/4 J-laser plasma driven electron beam. The data were collected by means of a ~ 3 m QQ¯QD spectrometer especially designed for that experiment. A 32× 16 fiber array detector, along with a scintillating LANEX screen and a Faraday cup were used to detect the electrons, and for charge monitoring. The momentum and spatial distributions of the beam were reconstructed. The results are consistent with a previous experiment, and compatible with a GEANT simulation used for background estimation due primarily to secondaries induced by electron-beam pipe collisions. We also report on the extracted emittance of the beam for the corresponding momentum range.

Guèye, Paul; Keppel, Cynthia; Lane, Bianca; Owens, Judy; Torrence, Rickey; Saleh, Ned; Umstadter, Don; Zhang, Ping; Ent, Rolf; Assamagan, Kétévi

2001-10-01

136

Laser steering of particle beams: Refraction and reflection ofparticle beams  

SciTech Connect

The co-propagation of an intense particle beam with an ionizing laser beam in a working gas/plasma is considered. When the axes of the laser and particle beam are not aligned, then asymmetric plasma lensing results in a net dipole field acting on the particle beam. The particle beam can be steered or bent (as well as focused) by steering the laser. An analogy is made between the bending of the particle beam by collective effects at a plasma boundary and the refraction or reflection of light at an interface. This mechanism of particle steering may be of interest in applications for which permanent magnets are inconvenient of a fast turn on is required. 3-D particle-in-cell simulations and relevance to a recent experiment are discussed.

Esarey, Eric; Katsouleas, T.; Mori, W.B.; Dodd, E.; Lee, S.; Hemker, R.; Clayton, C.; Joshi, C.

1999-11-01

137

Test particle acceleration in torsional fan reconnection  

NASA Astrophysics Data System (ADS)

Magnetic reconnection is understood to be a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. Torsional fan reconnection is one of the proposed mechanisms for steady-state three-dimensional (3D) magnetic reconnection. By using the magnetic and electric fields for `torsional fan reconnection', the features of test particle acceleration with input parameters for the solar corona are investigated numerically. We show that torsional fan reconnection is potentially an efficient particle accelerator and a proton can gain up to tens of MeV of kinetic energy within only a few milliseconds. Although the final kinetic energy of the accelerated particle depends on the injection position but there exists only one scenario for the particle's trajectory with different initial positions in which the particle is accelerated on the fan plane. Moreover, adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory. These results are compared with those of torsional spine reconnection.

Hosseinpour, M.

2014-12-01

138

Statistical phenomena in particle beams  

SciTech Connect

Particle beams are subject to a variety of apparently distinct statistical phenomena such as intrabeam scattering, stochastic cooling, electron cooling, coherent instabilities, and radiofrequency noise diffusion. In fact, both the physics and mathematical description of these mechanisms are quite similar, with the notion of correlation as a powerful unifying principle. In this presentation we will attempt to provide both a physical and a mathematical basis for understanding the wide range of statistical phenomena that have been discussed. In the course of this study the tools of the trade will be introduced, e.g., the Vlasov and Fokker-Planck equations, noise theory, correlation functions, and beam transfer functions. Although a major concern will be to provide equations for analyzing machine design, the primary goal is to introduce a basic set of physical concepts having a very broad range of applicability.

Bisognano, J.J.

1984-09-01

139

Transient particle acceleration associated with solar flares  

NASA Technical Reports Server (NTRS)

Mechanisms that apply to solar flares are discussed, and their applicability to other astrophysical sites, where transient X-ray and gamma-ray bursts occur, is tested. Two different approaches are used to determine the characteristics of the charged particles, accelerated in association with solar flares: (1) measurement of the energy spectra and composition of charged particles observed in space and believed to be associated with a specific solar flare; and (2) recording of electromagnetic emissions in the visible, ultraviolet, soft X-ray, hard X-ray, and gamma-ray spectral regions, and also high-energy neutrons produced in the solar atmosphere by the particles accelerated in association with the solar flare. It is suggested that, at the present level of knowledge, regions where particle acceleration and interactions occur are unlikely to be specified.

Chupp, E. L.

1990-01-01

140

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

PubMed

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 85 gigaelectronvolts 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 74 picocoulombs of charge contained in the core of the trailing bunch in an accelerating gradient of about 4.4 gigavolts per metre. These core particles gain about 1.6 gigaelectronvolts 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. PMID:25373678

Litos, M; Adli, E; An, W; Clarke, C I; Clayton, C E; Corde, S; Delahaye, J P; England, R J; Fisher, A S; Frederico, J; Gessner, S; Green, S Z; Hogan, M J; Joshi, C; Lu, W; Marsh, K A; Mori, W B; Muggli, P; Vafaei-Najafabadi, N; Walz, D; White, G; Wu, Z; Yakimenko, V; Yocky, G

2014-11-01

141

Particle acceleration in astrophysical shear flows  

E-print Network

We consider the acceleration of particles due to a velocity shear in relativistic astrophysical flows. The basic physical picture and the formation of power law momentum spectra is discussed for a non-relativistic velocity field using a microscopic approach. We identify possible sites for shear acceleration in relativistic astrophysical jets and analyze their associated acceleration timescales. It is shown in particular that for a mean scattering time $\\tau$ scaling with the gyro-radius, the acceleration timescale for gradual shear scales in the same manner as the synchrotron cooling timescale, so that losses may no longer be able to stop the acceleration once it has started to work efficiently. Finally, the possible role of shear acceleration is discussed with reference to the relativistic jet in the quasar 3C~273.

Frank M. Rieger; Peter Duffy

2005-01-10

142

High-powered pulsed-ion-beam acceleration and transport  

SciTech Connect

The state of research on intense ion beam acceleration and transport is reviewed. The limitations imposed on ion beam transport by space charge effects and methods available for neutralization are summarized. The general problem of ion beam neutralization in regions free of applied electric fields is treated. The physics of acceleration gaps is described. Finally, experiments on multi-stage ion acceleration are summarized.

Humphries, S. Jr.; Lockner, T.R.

1981-11-01

143

An interleaved, model-supported system identification scheme for the particle accelerator CLIC  

Microsoft Academic Search

The particle accelerator CLIC is a future linear collider, which is developed at CERN. The quality of the particle-beams produced by CLIC is very sensitive to ground motion. The efficiency of the feedback used to counteract ground motion, relies crucially on the quality of the system knowledge. Therefore, we present a system identification scheme to follow changes of accelerator parameters.

Jurgen Pfingstner; Daniel Schulte; Hermann Schmickler; Michael W. Hofbaur

2010-01-01

144

Phenomenology of crystalline beams in smooth accelerators  

SciTech Connect

We present a phenomenology of crystalline beams in storage rings. We use the smooth approximation to solve the equations of a test particle moving in the focussing potential of the storage ring, and in that of the other ions We find simple confinement, and stability conditions.

Haffmans, A.F.; Maletic, D.; Ruggiero, A.G.

1995-06-01

145

Radioactive ion beam acceleration at MAFF  

NASA Astrophysics Data System (ADS)

In April 2003, the German safety commission has given the final approval for the oper- ation of the high flux reactor FRM-II. This is an important step towards the development and installation of the Munich accelerator for fission fragments (MAFF), which will deliver highest intensities of neutron rich fission fragments. The acceleration chain of MAFF [1] consists of a charge breeder, which will deliver the ions with a mass to charge ratio of A/q ? 6.3 irrespective of the mass range, and with a repetition rate of maximum 50 Hz. The LINAC operating at 10% duty cycle is composed of a 101.28 IH-RFQ, which will boost up the energy from 2.5 up to 300 keV/u, three IH-tanks that will deliver an energy of 5.4 MeV/u and 2 seven gap IH-resonators that are used to vary the final energy up to a maximum of 5.9 MeV/u. Currently beam dynamics revisions are in progress especially in the low energy section, since the experimental program has requested specific time structures of the beam for TOF experiments. The status of the beam dynamics studies as well as the status of the single components of the accelerator will be presented in this paper.

Pasini, M.; Kester, O.; Habs, D.; Groß, M.; Sieber, T.; Maier, H. J.; Assmann, W.; Krüken, R.; Faestermann, T.; Schempp, A.; Ratzinger, U.; Safvan, C. P.

2004-12-01

146

Particle acceleration timescales in relativistic shear flows  

E-print Network

We review the acceleration of energetic particles in relativistic astrophysical jets characterized by a significant velocity shear. The possible formation of power-law momentum spectra is discussed and typical acceleration timescales are determined for a variety of different conditions such as parallel and azimuthal shear flows. Special attendance is given to the analysis of parallel shear flows with either a linear decreasing or a Gaussian-type velocity profile. It is shown that in the presence of a gradual shear flow and a particle mean free path scaling with the gyroradius, synchrotron radiation losses may no longer be able to stop the acceleration once it has started to work efficiently. Finally, the relevance of shear acceleration in small- and large-scale relativistic jets is addressed.

Frank M. Rieger; Peter Duffy

2005-06-29

147

Applications of Particle Accelerators in Medical Physics  

E-print Network

Particle accelerators are often associated to high energy or nuclear physics. As well pointed out in literature [1] if we kindly analyse the number of installation worldwide we can easily note that about 50% is mainly devoted to medical applications (radiotherapy, medical radioisotopes production, biomedical research). Particle accelerators are also playing an important indirect role considering the improvement of the technical features of medical diagnostic. In fact the use of radionuclide for advanced medical imaging is strongly increasing either in conventional radiography (CT and MRI) and also in nuclear medicine for Spect an PET imaging. In this paper role of particle accelerators for medical applications will be presented together with the main solutions applied.

Cuttone, G

2008-01-01

148

Space experiments with particle accelerators (SEPAC): Description of instrumentation  

NASA Technical Reports Server (NTRS)

SEPAC (Space Experiments with Particle Accelerators) flew on Spacelab 1 (SL 1) in November and December 1983. SEPAC is a joint U.S.-Japan investigation of the interaction of electron, plasma, and neutral beams with the ionosphere, atmosphere and magnetosphere. It is scheduled to fly again on Atlas 1 in August 1990. On SL 1, SEPAC used an electron accelerator, a plasma accelerator, and neutral gas source as active elements and an array of diagnostics to investigate the interactions. For Atlas 1, the plasma accelerator will be replaced by a plasma contactor and charge collection devices to improve vehicle charging meutralization. This paper describes the SEPAC instrumentation in detail for the SL 1 and Atlas 1 flights and includes a bibliography of SEPAC papers.

Taylor, W. W. L.; Roberts, W. T.; Reasoner, D. L.; Chappell, C. R.; Baker, B. B.; Burch, J. L.; Gibson, W. C.; Black, R. K.; Tomlinson, W. M.; Bounds, J. R.

1987-01-01

149

Hybrid Simulations of Particle Acceleration at Shocks  

E-print Network

We present the results of large hybrid (kinetic ions - fluid electrons) simulations of particle acceleration at non-relativistic collisionless shocks. Ion acceleration efficiency and magnetic field amplification are investigated in detail as a function of shock inclination and strength, and compared with predictions of diffusive shock acceleration theory, for shocks with Mach number up to 100. Moreover, we discuss the relative importance of resonant and Bell's instability in the shock precursor, and show that diffusion in the self-generated turbulence can be effectively parametrized as Bohm diffusion in the amplified magnetic field.

Caprioli, Damiano

2014-01-01

150

Transport of elliptic intense charged -particle beams  

E-print Network

The transport theory of high-intensity elliptic charged-particle beams is presented. In particular, the halo formation and beam loss problem associated with the high space charge and small-aperture structure is addressed, ...

Zhou, J. (Jing), 1978-

2006-01-01

151

The development of laser- and beam-driven plasma accelerators as an experimental fielda)  

NASA Astrophysics Data System (ADS)

Since its inception in the early 1980s, the field of plasma-based particle accelerators has made remarkable advances. Robust plasma accelerating structures can now be excited over centimeter scales using short laser pulses and over meter scales using ultrarelativistic particle beams. Accelerating fields in excess of tens of GV/m can be sustained over these lengths. Laser-driven plasma accelerators now routinely produce monoenergetic, low divergence electron beams in the 100MeV-1GeV range, whereas electron-beam driven plasma accelerators have demonstrated the ability to double the energy of 42GeV electrons using a high-energy collider beam in less than one meter. The development of this field is traced through a series of path breaking experiments.

Joshi, C.

2007-05-01

152

Isochoric heating with laser-accelerated proton beams  

NASA Astrophysics Data System (ADS)

Numerical simulations are used to study acceleration of protons by intense laser pulses and the induced heating of a secondary target using this proton beam. Laser-plasma interaction and ion acceleration are modeled with a multidimensional, relativistic particle-in-cell code. Proton slowing-down and secondary target heating are computed with a two-dimensional Monte Carlo and a one-dimensional Lagrangian hydrodynamics codes. Strategies for optimization of heating uniformity include tailoring the accelerated proton spectrum with specific target geometries or laser pulse parameters. A trade-off must then be found between heating uniformity and efficiency. The parameters (temperature, depth and radius of heated zone, characteristic heating and hydrodynamics times) that could be obtained on current short pulse laser facilities, using a typical 50 fs Gaussian pulse with an intensity of several 1019 W/cm2, are explored.

Carrié, M.; Combis, P.; Lefebvre, E.

2010-12-01

153

Accelerators for charged particle therapy: PAMELA and related issues  

NASA Astrophysics Data System (ADS)

Cancer is a dreadful disease that will affect one in three people at some point in their life; radiotherapy is used in more than half of all cancer treatment, and contributes about 40% to the successful treatment of cancer. Charged Particle Therapy uses protons and other light ions to deliver the lethal dose to the tumor while being relatively sparing of healthy tissue and, because of the finite range of the particles, is able to avoid giving any dose to vital organs. While there are adequate technologies currently available to deliver the required energies and fluxes, the two main technologies (cyclotrons and synchrotrons) have limitations. PAMELA (the Particle Accelerator for MEdicaL Applications) uses the newly-developed non-scaling Fixed Field Alternating Gradient accelerator concepts to deliver therapeutically relevant beams. The status of the development of the PAMELA conceptual design is discussed.

Peach, Ken

2014-05-01

154

Quiet time particle acceleration in interplanetary space  

E-print Network

We propose a model for the acceleration of charged particles in interplanetary space that appear during quiet time periods, that is, not associated with solar activity events like intense flares or coronal mass ejections. The interaction of charged particles with modeled turbulent electromagnetic fields, which mimic the fields observed in the interplanetary medium, is studied. The turbulence is modeled by means of a dynamical system,the Gledzer-Ohkitani-Yamada (GOY) shell model, which describes the gross features of the Navier-Stokes equations. The GOY model is used to build a 3-D velocity field, which in turn is used to numerically solve the ideal magneto-hydrodynamic (MHD) induction equation, while the electric field is calculated from the ideal Ohm's law. Particle acceleration in such an environment is investigated by test particle simulations, and the resulting energy distributions are discussed and compared to observations of suprathermal electrons and ions during quiet periods in interplanetary space.

F. Lepreti; H. Isliker; K. Petraki; L. Vlahos

2004-12-09

155

Non-accelerator particle physics  

SciTech Connect

The goals of this research are the experimental testing of fundamental theories of physics such as grand unification and the exploration of cosmic phenomena through the techniques of particle physics. We are working on the MACRO experiment, which employs a large area underground detector to search for grand unification magnetic monopoles and dark matter candidates and to study cosmic ray muons as well as low and high energy neutrinos: the {nu}IMB project, which seeks to refurbish and upgrade the IMB water Cerenkov detector to perform an improved proton decay search together with a long baseline reactor neutrino oscillation experiment using a kiloton liquid scintillator (the Perry experiment); and development of technology for improved liquid scintillators and for very low background materials in support of the MACRO and Perry experiments and for new solar neutrino experiments. 21 refs., 19 figs., 6 tabs.

Steinberg, R.I.; Lane, C.E.

1991-09-01

156

EIDOSCOPE : particle acceleration at plasma boundaries  

Microsoft Academic Search

We describe the mission concept of how ESA can make a major contribution to the Japanese Canadian multi-spacecraft mission\\u000a SCOPE by adding one cost-effective spacecraft EIDO (Electron and Ion Dynamics Observatory), which has a comprehensive and optimized plasma payload to address the physics of\\u000a particle acceleration. The combined mission EIDOSCOPE will distinguish amongst and quantify the governing processes of particle

A. Vaivads; G. Andersson; S. D. Bale; C. M. Cully; J. De Keyser; M. Fujimoto; S. Grahn; S. Haaland; H. Ji; Yu. V. Khotyaintsev; A. Lazarian; B. Lavraud; I. R. Mann; R. Nakamura; T. K. M. Nakamura; Y. Narita; A. Retinò; F. Sahraoui; A. Schekochihin; S. J. Schwartz; I. Shinohara; L. Sorriso-Valvo

2011-01-01

157

Stochastic Particle Acceleration near Accreting Black Holes  

E-print Network

We consider the stochastic acceleration of particles which results from resonant interactions with plasma waves in black hole magnetospheres. We calculate acceleration rates and escape time scales for protons and electrons resonating with Alfv\\'en waves, and for electrons resonating with whistlers. Assuming either a Kolmogorov or Kraichnan wave spectrum, accretion at the Eddington limit, magnetic field strengths near equipartition, and turbulence energy densities $\\sim 10\\%$ of the total magnetic field energy density, we find that Alfv\\'en waves accelerate protons to Lorentz factors $\\lte 10^4$--$10^6$ before they escape from the system. Acceleration of electrons by fast mode and whistler waves can produce a nonthermal population of relativistic electons whose maximum energy is determined by a competition with radiation losses. Particle energization and outflow is not possible at lower accretion rates, magnetic field strengths, or turbulence levels due to dominant Coulomb losses. Increases in the accretion luminosity relative to the Eddington luminosity can trigger particle acceleration out of the thermal background, and this mechanism could account for the differences between radio-quiet and radio-loud active galactic nuclei. Observations of outflowing radio-emitting components following transient X-ray events in galactic X-ray novae and gamma-ray flares in blazars are in accord with this scenario.

Charles D. Dermer; James A. Miller; Hui Li

1995-08-16

158

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators  

SciTech Connect

The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring. Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect. With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations. The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.

Mastoridis, Themistoklis; /Stanford U., Elect. Eng. Dept. /SLAC

2011-03-01

159

Seventy Five Years of Particle Accelerators  

ScienceCinema

Andy Sessler, Berkeley Lab director from 1973 to 1980, sheds light on the Lab's nearly eight-decade history of inventing and refining particle accelerators, which continue to illuminate the nature of the universe. His talk was presented July 26, 2006.

Andy Sessler

2013-06-11

160

Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 6: Accelerator Capabilities  

E-print Network

These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 6, on Accelerator Capabilities, discusses the future progress of accelerator technology, including issues for high-energy hadron and lepton colliders, high-intensity beams, electron-ion colliders, and necessary R&D for future accelerator technologies.

Barletta, W A; Battaglia, M; Bruning, O; Byrd, J; Ent, R; Flanagan, J; Gai, W; Galambos, J; Hoffstaetter, G; Hogan, M; Klute, M; Nagaitsev, S; Palmer, M; Prestemon, S; Roser, T; Rossi, L; Shiltsev, V; Varner, G; Yokoya, K

2014-01-01

161

US Particle Accelerator School Cyclotrons: Old but Still New  

E-print Network

US Particle Accelerator School Cyclotrons: Old but Still New The history of accelerators is a history of inventions William A. Barletta Director, US Particle Accelerator School Dept. of Physics, MIT Economics Faculty, University of Ljubljana #12;US Particle Accelerator School ~ 650 cyclotrons operating

Dai, Pengcheng

162

Particle Simulation Schemes for High Intensity Charged Particle Beams  

NASA Astrophysics Data System (ADS)

Numerical schemes for the electromagnetic particle simulations of high intensity charged particle beams have been developed. The purpose of devising these schemes is to avoid the numerical difficulties associated with the direct calculation of the time derivatives of the vector potential, partial A / partial t, in the Darwin model, for which the transverse induction current in Ampere's law is neglected. The first scheme requires the calculations of higher order velocity moments of the distribution function to obtain the time derivatives for both the scalar potential ? and A, similar to the method used for shear-Alfven waves.[1] The second uses the canonical momentum P = p + q A/c in the equations of motion as a means to eliminate the troublesome time derivatives.[2] The use of these schemes for physics problems in heavy ion fusion systems will be reported. [1] W. W. Lee, J. L. V. Lewandowski, T. S. Hahm, and Z. Lin, Phys. Plasmas 8, 4435 (2001). [2] W. W. Lee, E. Startsev, H. Qin and R. C. Davidson, Proceedings of 2001 Particle Accelerator Conference 1906 (2001).

Lee, Wei-Li; Startsev, Edward; Qin, Hong; Davidson, Ronald C.

2003-10-01

163

Design and optimization of a multi-particle accelerator beam transport and delivery system for material irradiation in nuclear and fusion science  

E-print Network

A beam delivery and transport system were designed for the use in MIT Materials Test Facility (M2TF). The purpose of this beam delivery system was to design a 36 MeV Proton Cyclotron for DPA accumulation and a 100 MeV ...

Sordelet, Tyler Christopher

2012-01-01

164

Requirements for Simulating Space Radiation With Particle Accelerators  

NASA Technical Reports Server (NTRS)

Interplanetary space radiation consists of fully ionized nuclei of atomic elements with high energy for which only the few lowest energy ions can be stopped in shielding materials. The health risk from exposure to these ions and their secondary radiations generated in the materials of spacecraft and planetary surface enclosures is a major limiting factor in the management of space radiation risk. Accurate risk prediction depends on a knowledge of basic radiobiological mechanisms and how they are modified in the living tissues of a whole organism. To a large extent, this knowledge is not currently available. It is best developed at ground-based laboratories, using particle accelerator beams to simulate the components of space radiation. Different particles, in different energy regions, are required to study different biological effects, including beams of argon and iron nuclei in the energy range 600 to several thousand MeV/nucleon and carbon beams in the energy range of approximately 100 MeV/nucleon to approximately 1000 MeV/nucleon. Three facilities, one each in the United States, in Germany and in Japan, currently have the partial capability to satisfy these constraints. A facility has been proposed using the Brookhaven National Laboratory Booster Synchrotron in the United States; in conjunction with other on-site accelerators, it will be able to provide the full range of heavy ion beams and energies required. International cooperation in the use of these facilities is essential to the development of a safe international space program.

Schimmerling, W.; Wilson, J. W.; Cucinotta, F.; Kim, M-H Y.

2004-01-01

165

Aerodynamic beam generator for large particles  

DOEpatents

A new type of aerodynamic particle beam generator is disclosed. This generator produces a tightly focused beam of large material particles at velocities ranging from a few feet per second to supersonic speeds, depending on the exact configuration and operating conditions. Such generators are of particular interest for use in additive fabrication techniques.

Brockmann, John E. (Albuquerque, NM); Torczynski, John R. (Albuquerque, NM); Dykhuizen, Ronald C. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Smith, Mark F. (Albuquerque, NM)

2002-01-01

166

A plasma wakefield acceleration experiment using CLARA beam  

NASA Astrophysics Data System (ADS)

We propose a Plasma Accelerator Research Station (PARS) based at proposed FEL test facility CLARA (Compact Linear Accelerator for Research and Applications) at Daresbury Laboratory. The idea is to use the relativistic electron beam from CLARA, to investigate some key issues in electron beam transport and in electron beam driven plasma wakefield acceleration, e.g. high gradient plasma wakefield excitation driven by a relativistic electron bunch, two bunch experiment for CLARA beam energy doubling, high transformer ratio, long bunch self-modulation and some other advanced beam dynamics issues. This paper presents the feasibility studies of electron beam transport to meet the requirements for beam driven wakefield acceleration and presents the plasma wakefield simulation results based on CLARA beam parameters. Other possible experiments which can be conducted at the PARS beam line are also discussed.

Xia, G.; Angal-Kalinin, D.; Clarke, J.; Smith, J.; Cormier-Michel, E.; Jones, J.; Williams, P. H.; Mckenzie, J. W.; Militsyn, B. L.; Hanahoe, K.; Mete, O.; Aimidula, A.; Welsch, C. P.

2014-03-01

167

``Accelerators and Beams,'' multimedia computer-based training in accelerator physics  

NASA Astrophysics Data System (ADS)

We are developing a set of computer-based tutorials on accelerators and charged-particle beams under an SBIR grant from the DOE. These self-paced, interactive tutorials, available for Macintosh and Windows platforms, use multimedia techniques to enhance the user's rate of learning and length of retention of the material. They integrate interactive "On-Screen Laboratories," hypertext, line drawings, photographs, two- and three-dimensional animations, video, and sound. They target a broad audience, from undergraduates or technicians to professionals. Presently, three modules have been published (Vectors, Forces, and Motion), a fourth (Dipole Magnets) has been submitted for review, and three more exist in prototype form (Quadrupoles, Matrix Transport, and Properties of Charged-Particle Beams). Participants in the poster session will have the opportunity to try out these modules on a laptop computer.

Silbar, R. R.; Browman, A. A.; Mead, W. C.; Williams, R. A.

1999-06-01

168

Particle Accelerators for Radiotherapy:. Present Status and Future  

NASA Astrophysics Data System (ADS)

The paper describes the development of the application of particle accelerators in the treatment of cancer diseases over the past fifty years. Special emphasis is put on the routine application of conventional electron accelerators delivering electron and photon beams. This is the largest group of devices for radiotherapy (over 7500 machines operating worldwide). The number of patients reaches 5 million per year. The medical electron linacs have recently undergone considerable modifications of construction, in particular the systems of radiation field shaping. Contemporary accelerators for radiotherapy are equipped with multi-leaf collimators (MLC) which, in conjunction with IMRT (Intensity Modulation Radiation Therapy) technique and special system of therapy planning, assure considerably higher precision, effectiveness and quality of treatment.

Maciszewski, Wieslaw; Scharf, Waldemar

2004-07-01

169

Transient particle acceleration associated with solar flares.  

PubMed

Understanding how individual charged particles can be accelerated to extreme energies (10(20) electron volts), remains a foremost problem in astrophysics. Within our solar system, the active sun is capable of producing, on a short time scale, ions with energies higher than 25 gigaelectron volts. Satellite and ground-based observation over the past 30 years have greatly increased our knowledge of the properties of transient bursts of energetic particles emitted from the sun in association with solar flares, but a real understanding of the solar flare particle acceleration process requires greatly refined experimental data. On the practical side, it is also imperative that this problem be solved if man is to venture, for long periods of time, beyond the protective umbrella of Earth's magnetic field, which excludes much of the biologically damaging solar energetic particles. It is only through an understanding of the basic acceleration problem that we can expect to be able to predict the occurrence of a solar flare with lethal solar radiations. For our knowledge of these effects to advance, a new space mission dedicated to studying the high-energy aspects of solar flares at high spatial and energy resolution will be required. PMID:17797307

Chupp, E L

1990-10-12

170

Linear particle accelerator with seal structure between electrodes and insulators  

DOEpatents

An electrostatic linear accelerator includes an electrode stack comprised of primary electrodes formed or Kovar and supported by annular glass insulators having the same thermal expansion rate as the electrodes. Each glass insulator is provided with a pair of fused-in Kovar ring inserts which are bonded to the electrodes. Each electrode is designed to define a concavo-convex particle trap so that secondary charged particles generated within the accelerated beam area cannot reach the inner surface of an insulator. Each insulator has a generated inner surface profile which is so configured that the electrical field at this surface contains no significant tangential component. A spark gap trigger assembly is provided, which energizes spark gaps protecting the electrodes affected by over voltage to prevent excessive energy dissipation in the electrode stack.

Broadhurst, John H. (Golden Valley, MN)

1989-01-01

171

TOPICS IN THE PHYSICS OF PARTICLE ACCELERATORS  

SciTech Connect

High energy physics, perhaps more than any other branch of science, is driven by technology. It is not the development of theory, or consideration of what measurements to make, which are the driving elements in our science. Rather it is the development of new technology which is the pacing item. Thus it is the development of new techniques, new computers, and new materials which allows one to develop new detectors and new particle-handling devices. It is the latter, the accelerators, which are at the heart of the science. Without particle accelerators there would be, essentially, no high energy physics. In fact. the advances in high energy physics can be directly tied to the advances in particle accelerators. Looking terribly briefly, and restricting one's self to recent history, the Bevatron made possible the discovery of the anti-proton and many of the resonances, on the AGS was found the {mu}-neutrino, the J-particle and time reversal non-invariance, on Spear was found the {psi}-particle, and, within the last year the Z{sub 0} and W{sup {+-}} were seen on the CERN SPS p-{bar p} collider. Of course one could, and should, go on in much more detail with this survey, but I think there is no need. It is clear that as better acceleration techniques were developed more and more powerful machines were built which, as a result, allowed high energy physics to advance. What are these techniques? They are very sophisticated and ever-developing. The science is very extensive and many individuals devote their whole lives to accelerator physics. As high energy experimental physicists your professional lives will be dominated by the performance of 'the machine'; i.e. the accelerator. Primarily you will be frustrated by the fact that it doesn't perform better. Why not? In these lectures, six in all, you should receive some appreciation of accelerator physics. We cannot, nor do we attempt, to make you into accelerator physicists, but we do hope to give you some insight into the machines with which you will be involved in the years to come. Perhaps, we can even turn your frustration with the inadequacy of these machines into marvel at the performance of the accelerators. At the least, we hope to convince you that the accelerators are central, not peripheral, to our science and that the physics of such machines is both fascinating and sophisticated. The plan is the following: First I will give two lectures on basic accelerator physics; then you will hear two lectures on the state of the art, present limitations, the specific parameters of LEP, HERA, TEV2 and SLC, and some extrapolation to the next generation of machines such as the Large Hadron Collider (LHC), Superconducting Super Collider (SSC), and Large Linear Colliders; finally, I will give two lectures on new acceleration methods.

Sessler, A.M.

1984-07-01

172

Electron Cloud Effects on Long-Term Beam Dynamics in a Circular Accelerator  

Microsoft Academic Search

In this paper we study long term dynamics of an intense positively charged beam in the presence of electron clouds in a circular accelerator. Particularly, we study strong head-tail beam instabilities, emmitance growth and tune shift caused by electron cloud. We adopt a Particle-in-cell (PIC) code, QuickPIC, which we have been developing for plasma based accelerators studies to the problem

Ali Ghalam; Tom Katsouleas; Giovanni Rumolo; Frank Zimmermann; Viktor Decyk; Chengkun Huang; Warren Mori; Francesco Ruggiero

2003-01-01

173

Levy-Student distributions for halos in accelerator beams  

SciTech Connect

We describe the transverse beam distribution in particle accelerators within the controlled, stochastic dynamical scheme of stochastic mechanics (SM) which produces time reversal invariant diffusion processes. This leads to a linearized theory summarized in a Schroedinger-like (SL) equation. The space charge effects have been introduced in recent papers by coupling this S-L equation with the Maxwell equations. We analyze the space-charge effects to understand how the dynamics produces the actual beam distributions, and in particular we show how the stationary, self-consistent solutions are related to the (external and space-charge) potentials both when we suppose that the external field is harmonic (constant focusing), and when we a priori prescribe the shape of the stationary solution. We then proceed to discuss a few other ideas by introducing generalized Student distributions, namely, non-Gaussian, Levy infinitely divisible (but not stable) distributions. We will discuss this idea from two different standpoints: (a) first by supposing that the stationary distribution of our (Wiener powered) SM model is a Student distribution; (b) by supposing that our model is based on a (non-Gaussian) Levy process whose increments are Student distributed. We show that in the case (a) the longer tails of the power decay of the Student laws and in the case (b) the discontinuities of the Levy-Student process can well account for the rare escape of particles from the beam core, and hence for the formation of a halo in intense beams.

Cufaro Petroni, Nicola; De Martino, Salvatore; De Siena, Silvio; Illuminati, Fabrizio [Dipartimento di Matematica dell'Universita di Bari and INFN Sezione di Bari, via E. Orabona 4, 70125 Bari (Italy); Dipartimento di Fisica dell'Universita di Salerno, INFM Unita di Salerno, and INFN Sezione di Napoli Gruppo collegato di Salerno, Via S. Allende, I-84081 Baronissi (Saudi Arabia) (Italy)

2005-12-15

174

Naked singularities as particle accelerators. II  

SciTech Connect

We generalize here our earlier results on particle acceleration by naked singularities. We showed recently [M. Patil and P. S. Joshi, Phys. Rev. D 82, 104049 (2010).] that the naked singularities that form due to the gravitational collapse of massive stars provide a suitable environment where particles could get accelerated and collide at arbitrarily high center-of-mass energies. However, we focused there only on the spherically symmetric gravitational collapse models, which were also assumed to be self-similar. In this paper, we broaden and generalize the result to all gravitational collapse models leading to the formation of a naked singularity as the final state of collapse, evolving from a regular initial data, without making any prior restrictive assumptions about the spacetime symmetries such as above. We show that, when the particles interact and collide near the Cauchy horizon, the energy of collision in the center-of-mass frame will be arbitrarily high, thus offering a window to the Planck scale physics. We also consider the issue of various possible physical mechanisms of generation of such very high-energy particles from the vicinity of naked singularity. We then construct a model of gravitational collapse to a timelike naked singularity to demonstrate the working of these ideas, where the pressure is allowed to be negative, but the energy conditions are respected. We show that a finite amount of mass-energy density has to be necessarily radiated away from the vicinity of the naked singularity as the collapse evolves. Therefore, the nature of naked singularities, both at the classical and quantum level, could play an important role in the process of particle acceleration, explaining the occurrence of highly energetic outgoing particles in the vicinity of the Cauchy horizon that participate in extreme high-energy collisions.

Patil, Mandar; Joshi, Pankaj S.; Malafarina, Daniele [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2011-03-15

175

A double-foil target for improving beam quality in laser ion acceleration with thin foils  

SciTech Connect

A double-foil target is proposed for laser ion acceleration with thin targets to take advantage of high efficiency of such targets while avoiding beam degradation in late stage of acceleration. Laser heating of electrons co-moving with the ion beam is stopped by the second foil. It is found that the second foil can also modify and substantially improve the spectral and spatial properties of the ion beam and reduce the temperature of the co-moving electrons, leading to better preservation of the beam quality. Details of the dynamics are studied with particle-in-cell simulations.

Huang, C.-K.; Albright, B. J.; Yin, L.; Wu, H.-C.; Bowers, K. J.; Hegelich, B. M.; Fernandez, J. C. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2011-05-15

176

Particle acceleration during substorm growth and onset  

Microsoft Academic Search

The authors present ISEE-1 observations of ion and electron energization made at â¼11 R{sub E} during a substorm event occurring on 2 April 1978. An analysis of the dominant cross-tail current systems in this event has allowed them to uniquely associate particle energization processes with the development and\\/or disruption of the cross-tail currents. They find that significant ion acceleration occurs

D. J. Williams; D. G. Mitchell; C. Y. Huang; L. A. Frank; C.T. Russell

1990-01-01

177

Stochastic Particle Acceleration in Impulsive Solar Flares  

NASA Technical Reports Server (NTRS)

The acceleration of a huge number of electrons and ions to relativistic energies over timescales ranging from several seconds to several tens of seconds is the fundamental problem in high-energy solar physics. The cascading turbulence model we have developed has been shown previously (e.g., Miller 2000; Miller & Roberts 1995; Miner, LaRosa, & Moore 1996) to account for all the bulk features (such as acceleration timescales, fluxes, total number of energetic particles, and maximum energies) of electron and proton acceleration in impulsive solar flares. While the simulation of this acceleration process is involved, the essential idea of the model is quite simple, and consists of just a few parts: 1. During the primary flare energy release phase, we assume that low-amplitude MHD Alfven and fast mode waves are excited at long wavelengths, say comparable to the size of the event (although the results are actually insensitive to this initial wavelength). While an assumption, this appears reasonable in light of the likely highly turbulent nature of the flare. 2. These waves then cascade in a Kolmogorov-like fashion to smaller wavelengths (e.g., Verma et al. 1996), forming a power-law spectral density in wavenumber space through the inertial range. 3. When the mean wavenumber of the fast mode waves has increased sufficiently, the transit-time acceleration rate (Miller 1997) for superAlfvenic electrons can overcome Coulomb energy losses, and these electrons are accelerated out of the thermal distribution and to relativistic energies (Miller et al. 1996). As the Alfven waves cascade to higher wavenumbers, they can cyclotron resonate with progressively lower energy protons. Eventually, they will resonate with protons in the tail of the thermal distribution, which will then be accelerated to relativistic energies as well (Miller & Roberts 1995). Hence, both ions and electrons are stochastically accelerated, albeit by different mechanisms and different waves. 4. When the protons become superAlfvenic (above about 1 MeV/nucleon), they too can suffer transit-time acceleration by the fast mode waves and will receive an extra acceleration "kick." The basic overall objective of this 1 year effort was to construct a spatially-dependent version of this acceleration model and this has been realized.

Miller, James A.

2001-01-01

178

Radiation Safety System for SPIDER Neutral Beam Accelerator  

SciTech Connect

SPIDER (Source for Production of Ion of Deuterium Extracted from RF Plasma only) and MITICA (Megavolt ITER Injector Concept Advanced) are the ITER neutral beam injector (NBI) testing facilities of the PRIMA (Padova Research Injector Megavolt Accelerated) Center. Both injectors accelerate negative deuterium ions with a maximum energy of 1 MeV for MITICA and 100 keV for SPIDER with a maximum beam current of 40 A for both experiments. The SPIDER facility is classified in Italy as a particle accelerator. At present, the design of the radiation safety system for the facility has been completed and the relevant reports have been presented to the Italian regulatory authorities. Before SPIDER can operate, approval must be obtained from the Italian Regulatory Authority Board (IRAB) following a detailed licensing process. In the present work, the main project information and criteria for the SPIDER injector source are reported together with the analysis of hypothetical accidental situations and safety issues considerations. Neutron and photon nuclear analysis is presented, along with special shielding solutions designed to meet Italian regulatory dose limits. The contribution of activated corrosion products (ACP) to external exposure of workers has also been assessed. Nuclear analysis indicates that the photon contribution to worker external exposure is negligible, and the neutron dose can be considered by far the main radiation protection issue. Our results confirm that the injector has no important radiological impact on the population living around the facility.

Sandri, S.; Poggi, C. [ENEA, Radiation Protection Institute, IRP-FUAC, Frascati (Italy); Coniglio, A. [Medical Physics Department, S. Giovanni Calibita Hospital, Fatebenefratelli, Isola Tiberina, Roma (Italy); D'Arienzo, M. [ENEA, Ionizing Radiation Metrology National Institute, METR, Casaccia, Rome (Italy)

2011-12-13

179

Mechanisms for Particle Acceleration in Impulsive Flares  

NASA Astrophysics Data System (ADS)

Magnetic reconnection is a plasma process in which magnetic energy is rapidly converted to kinetic energy via a change in the magnetic topology. Observations of reconnection in solar flares show it to be an very efficient accelerator of particles, e.g. nonthermal electrons. The traditional picture of acceleration via parallel electric fields near the magnetic X-line does not scale well to large systems such as the solar corona. Recent work has shown that particles may be accelerated by a Fermi mechanism inside contracting magnetic islands. This mechanism was previously explored in terms of particles trapped in contracting islands, gaining energy due to the conservation of the parallel adiabatic invariant. However, this treatment is not strictly applicable in complicated island geometries where particles are poorly trapped. To generalize this theory, we examine this mechanism by means of its local expression: the scalar product of the electric force with the curvature drift. This proves equivalent to conservation of the parallel adiabatic invariant for the case of a trapped particle. We present two-dimensional kinetic simulations which explore the relative importance of this term compared to parallel electric fields. The curvature-drift term dominates in antiparallel reconnection, with a negligible contribution from parallel electric fields. In the guide field simulations, relevant for solar flares, the contribution from parallel electric fields is significant. We explore several simulations with varying system sizes and mass ratios in order to examine how the parallel electric fields and the curvature-drift term would scale to large systems relevant for physical applications. We then compare the 2D results with 3D simulations.

Dahlin, J.; Drake, J. F.; Swisdak, M. M.

2013-12-01

180

Beam loading in a laser-plasma accelerator using a near-hollow plasma channel  

SciTech Connect

Beam loading in laser-plasma accelerators using a near-hollow plasma channel is examined in the linear wake regime. It is shown that, by properly shaping and phasing the witness particle beam, high-gradient acceleration can be achieved with high-efficiency, and without induced energy spread or emittance growth. Both electron and positron beams can be accelerated in this plasma channel geometry. Matched propagation of electron beams can be achieved by the focusing force provided by the channel density. For positron beams, matched propagation can be achieved in a hollow plasma channel with external focusing. The efficiency of energy transfer from the wake to a witness beam is calculated for single ultra-short bunches and bunch trains.

Schroeder, C. B.; Benedetti, C.; Esarey, E.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2013-12-15

181

Longitudinal control of intense charged particle beams  

NASA Astrophysics Data System (ADS)

As the accelerator frontier shifts from high energy to high intensity, accelerator facilities are demanding beams with higher quality. Applications such as Free Electron Lasers and Inertial Fusion Energy production require the minimization of both transverse emittance and longitudinal energy spread throughout the accelerator. Fluctuations in beam energy or density at the low-energy side of the accelerator, where space-charge forces dominate, may lead to larger modulations downstream and the eventual degradation of the overall beam quality. Thus it is important to understand the phenomenon that causes these modulations in space-charge dominated beams and be able to control them. This dissertation presents an experimental study on the longitudinal control of a space-charge dominated beam in the University of Maryland Electron Ring (UMER). UMER is a scaled model of a high-intensity beam system, which uses low-energy high-current electron beams to study the physics of space-charge. Using this facility, I have successfully applied longitudinal focusing to the beam edges, significantly lengthening the propagation distance of the beam to 1000 turns (>11.52 km). This is a factor of 10 greater than the original design conceived for the accelerator. At this injected current, the space-charge intensity is several times larger than the standard limit for storage rings, an encouraging result that raises the possibility of operating these machines with far more space-charge than previously assumed possible. I have also explored the transverse/longitudinal correlations that result when a beam is left to expand longitudinally under its own space-charge forces. In this situation, the beam ends develop a large correlated energy spread. Through indirect measurements, I have inferred the correlated energy profile along the bunch length. When the bunch is contained using longitudinal focusing, I have shown that errors in the applied focusing fields induce space-charge waves at the bunch edges that propagate into the middle region of the beam. In some cases, these waves sustain multiple reflections before damping away. I conclude that space-charge in an intense beam without longitudinal focusing can cause the bunch to develop a large correlated energy spread, increasing the risk that the beam is lost to the pipe walls as it requires a larger aperture. When longitudinal focusing is applied however, we are able to transport the beam over a much longer path length and reduce the correlated energy spread.

Beaudoin, Brian Louis

182

Equations of motion for a mass particle elastically mounted on a disk subjected to transverse and rotational accelerations. [Simulation of projectile accelerated down a rifled gun tube  

Microsoft Academic Search

Equations of motion for a mass particle elastically mounted on a disk which is subjected to transverse and rotational accelerations are derived. The idealized problem considered herein is an approximation to a more complicated problem concerned with the lateral response of a cantilever beam due to the balloting accelerations of a projectile as it accelerates down a rifled gun tube.

Benedetti

1977-01-01

183

Laser ion acceleration toward future ion beam cancer therapy - Numerical simulation study -  

PubMed Central

Background: Ion beam has been used in cancer treatment, and has a unique preferable feature to deposit its main energy inside a human body so that cancer cell could be killed by the ion beam. However, conventional ion accelerator tends to be huge in its size and its cost. In this paper a future intense-laser ion accelerator is proposed to make the ion accelerator compact. Subjects and methods: An intense femtosecond pulsed laser was employed to accelerate ions. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching and the ion particle energy control. In the study particle computer simulations were performed to solve the issues, and each component was designed to control the ion beam quality. Results: When an intense laser illuminates a target, electrons in the target are accelerated and leave from the target; temporarily a strong electric field is formed between the high-energy electrons and the target ions, and the target ions are accelerated. The energy efficiency from the laser to ions was improved by using a solid target with a fine sub-wavelength structure or by a near-critical density gas plasma. The ion beam collimation was realized by holes behind the solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching were successfully realized by a multi-stage laser-target interaction. Conclusions: The present study proposed a novel concept for a future compact laser ion accelerator, based on each component study required to control the ion beam quality and parameters. PMID:24155555

Kawata, Shigeo; Izumiyama, Takeshi; Nagashima, Toshihiro; Takano, Masahiro; Barada, Daisuke; Kong, Qing; Gu, Yan Jun; Wang, Ping Xiao; Ma, Yan Yun; Wang, Wei Min

2013-01-01

184

Calculation of Beam Loss Induced Particle Flux for CTF3 Matthew Wood  

E-print Network

Calculation of Beam Loss Induced Particle Flux for CTF3 Matthew Wood Northwestern University January 8, 2004 CTF3 Note 061 This research was partially supported by the Illinois Consortium to compute the beam loss induced particle ux outside the CTF3 accelerator vacuum chamber. GEANT 3

185

Application of MO-Type Flange for Accelerator Beam Ducts 3  

Microsoft Academic Search

Based on experiences in the precedent stain-less steel case, a possibility of employing copper-alloy and aluminum-alloy Matsumoto-Ohtsuka (MO)-type flanges in a vacuum beam pipes for a particle accelerator is experimentally studied. They can mitigate the heating problems found in the case of stainless-steel flanges under high-intensity beams, and also simplify the manufacturing procedure of beam pipes. Copper-alloy flanges show a

Yusuke Suetsugu; Mitsuru Shirai; Michio Ohtsuka; Toshiro Nishidono; Kazuhiko Watanabe; Yasuaki Suzuki; Akira Morishige; Masao Tsuchiya; Tomohiro Yonemoto

2010-01-01

186

Annular Cherenkov High Gradient Wakefield Accelerator: Beam-Breakup Analysis and Energy Transfer Efficiency  

Microsoft Academic Search

In this paper, we give a complete analytical solution for Cherenkov wakefields generated by an azimuthally asymmetric annular beam propagating in a coaxial two-channel dielectric structure. The transformer ratio of this type of structure is dramatically increased in comparison to a cylindrical wakefield accelerating structure. A particle-Green's function beam dynamics code (BBU-3000) to study beam breakup effects has been upgraded

A M Altmark; A D Kanareykin

2012-01-01

187

Emittance in particle and radiation beam techniques  

SciTech Connect

The author discusses the important and diverse role of the phase space area - the emittance - in the advanced techniques involving interaction of particle and radiation beams. For undulator radiation from unbunched beams, the radiation phase space is diluted from the coherent phase space of the single electron radiation. When the undulator radiation is used as a light source, it is important to minimize the dilution by decreasing the beam emittance and matching the phase space distributions of the particle and the radiation beams. For optical stochastic cooling, on the other hand, the phase space should be maximally mismatched for efficient cooling. In the case particles are bunched to a length much shorter than the radiation wavelength, the emittance appears as an intensity enhancement factor. In the operation of free electron lasers, the phase space matching becomes doubly important, once as the dilution factor in the initial stage of energy modulation and then as the radiation efficiency factor at the end where the beam is density modulated. The author then discusses some of the beam cooling techniques producing smaller emittances, especially the recent suggestions for relativistic heavy ions in storage rings or electron beams in linacs. These are based on the radiative cooling that occurs when particle beams backscatter powerful laser beams.

Kim, Kwang-Je

1997-03-01

188

Generating Particle Beams of Controlled Dimensions and Divergence: II. Experimental Evaluation of Particle Motion in Aerodynamic Lenses and Nozzle Expansions  

Microsoft Academic Search

A particle-beam-forming apparatus for producing narrow particle beams was developed based on the theory discussed in paper I of this series. It consists of a variable number of aerodynamic lenses (short capillaries and\\/or thin-plate orifices with diameters ranging from 3.5 to 7.0 mm) followed by an accelerating nozzle (3 mm). It was evaluated using monodisperse DOS and NaCl particles (0.02–0.24

Peng Liu; Paul J. Ziemann; David B. Kittelson; Peter H. McMurry

1995-01-01

189

ASSESSMENT OF A PARTICLE BED BASED BEAM STOP.  

SciTech Connect

Accelerator target/beam stop concepts able to withstand the thermal shock induced by intense, undiluted beams are being assessed in this study. Such conditions normally push target materials beyond their limits leading to limited useful life. A number of ingenious options have been attempted to help reduce the level of stress generated. Attention is paid to a very promising option that calls for a target consisting of a cooled particle bed. In such configuration the ability of the particle bed structure to diffuse and attenuate the generated thermal shock waves is being explored by performing comprehensive dynamic analyses that incorporate anticipated energy depositions, thermal diffusion, and wave propagation and attenuation. Further, options of coolant liquid filling the porous structure of the particle bed, including concerns of pressure drop and heat transfer, are evaluated for maximizing particle yield.

SIMOS,N.; LUDEWIG,H.; MONTANEZ,P.; TODOSOW,M.

2002-06-03

190

Neutral particle beam sensing and steering  

DOEpatents

The direction of a neutral particle beam (NPB) is determined by detecting Ly.alpha. radiation emitted during motional quenching of excited H(2S) atoms in the beam during movement of the atoms through a magnetic field. At least one detector is placed adjacent the beam exit to define an optical axis that intercepts the beam at a viewing angle to include a volume generating a selected number of photons for detection. The detection system includes a lens having an area that is small relative to the NPB area and a pixel array located in the focal plane of the lens. The lens viewing angle and area pixel array are selected to optimize the beam tilt sensitivity. In one embodiment, two detectors are placed coplanar with the beam axis to generate a difference signal that is insensitive to beam variations other than beam tilt.

Maier, II, William B. (Los Alamos, NM); Cobb, Donald D. (Los Alamos, NM); Robiscoe, Richard T. (Los Alamos, NM)

1991-01-01

191

9/16/2009 Andy Haas Stanford Student Orientation: Accelerator based Particle Physics 1 Accelerator-based Particle Physics  

E-print Network

9/16/2009 Andy Haas Stanford Student Orientation: Accelerator based Particle Physics 1 Accelerator-based Particle Physics Opportunities at SLAC/Stanford Andy Haas / SLAC Stanford Student Orientation Sept. 16, 2009 #12;9/16/2009 Andy Haas Stanford Student Orientation: Accelerator based Particle Physics 2

Wechsler, Risa H.

192

Particle beam and crabbing and deflecting structure  

DOEpatents

A new type of structure for the deflection and crabbing of particle bunches in particle accelerators comprising a number of parallel transverse electromagnetic (TEM)-resonant) lines operating in opposite phase from each other. Such a structure is significantly more compact than conventional crabbing cavities operating the transverse magnetic TM mode, thus allowing low frequency designs.

Delayen, Jean (Yorktown, VA)

2011-02-08

193

Polymer surface treatment with particle beams  

DOEpatents

A polymer surface and near surface treatment process produced by irradiation with high energy particle beams is disclosed. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications. 16 figs.

Stinnett, R.W.; VanDevender, J.P.

1999-05-04

194

Polymer surface treatment with particle beams  

DOEpatents

A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

Stinnett, Regan W. (1033 Tramway La. NE., Albuquerque, NM 87122); VanDevender, J. Pace (7604 Lamplighter NE., Albuquerque, NM 87109)

1999-01-01

195

Computer modeling of test particle acceleration at oblique shocks  

Microsoft Academic Search

We review the basic techniques and results of numerical codes used to model the acceleration of charged particles at oblique, fast-mode, collisionless shocks. The emphasis is upon models in which accelerated particles (ions) are treated as test particles, and particle dynamics is calculated by numerically integrating along exact phase-space orbits. We first review the case where ions are sufficiently energetic

Robert B. Decker

1988-01-01

196

Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron  

E-print Network

Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron A Research Centre astroparticle physics(f/m) DESY DESY is one of the world's leading research centres for photon science, particle modeling of nonthermal sources · Kinetic studies of wave-particle interactions · Particle acceleration

197

Advanced Accelerating Structures and Their Interaction with Electron Beams  

SciTech Connect

In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

Gai Wei [High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

2009-01-22

198

Advanced accelerating structures and their interaction with electron beams.  

SciTech Connect

In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

Gai, W.; High Energy Physics

2008-01-01

199

Advanced Accelerating Structures and Their Interaction with Electron Beams  

NASA Astrophysics Data System (ADS)

In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a ˜80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

Gai, Wei

2009-01-01

200

PARTICLE BEAM RADIOTHERAPY: CLINICAL PERSPECTIVE  

E-print Network

path is referred to as linear energy transfer. Conventional photon and electron beams used in therapy, dependent on the tissue type, chosen endpoint, dose fractionation schema, and so on. However, for practical

Yetisgen-Yildiz, Meliha

201

Enhanced quasi-static particle-in-cell simulation of electron cloud instabilities in circular accelerators  

Microsoft Academic Search

Electron cloud instabilities have been observed in many circular accelerators around the world and raised concerns of future accelerators and possible upgrades. In this thesis, the electron cloud instabilities are studied with the quasi-static particle-in-cell (PIC) code QuickPIC. Modeling in three-dimensions the long timescale propagation of beam in electron clouds in circular accelerators requires faster and more efficient simulation codes.

Bing Feng

2009-01-01

202

Proceedings of the 22nd Particle Accelerator Conference (PAC'07)  

SciTech Connect

The twenty-second Particle Accelerator Conference, PAC'07, took place at the Albuquerque Convention Centre in Albuquerque, the largest city in New Mexico, from Monday to Friday, 2007 June 25 to 29. It was attended by over 1350 delegates from 25 different countries (63% North America, 24% Europe, 11% Asia and 2% Other), and was held under the auspices of the two professional societies that oversee and make holding this series of conferences possible, the Division of Physics of Beams within APS, and the Nuclear and Plasma Sciences Society within IEEE. As host of the conference, Los Alamos National Laboratory (LANL) is especially thanked for their many contributions and assistance both prior to and during the conference. The Convention Center was an ideal location for information sharing and discussions between the interdisciplinary aspects of the accelerator community, as well as for related meetings and ad-hoc 'rump' sessions.

N /A

2007-08-01

203

Laser Plasma Particle Accelerators: Large Fields for Smaller Facility Sources  

SciTech Connect

Compared to conventional particle accelerators, plasmas can sustain accelerating fields that are thousands of times higher. To exploit this ability, massively parallel SciDAC particle simulations provide physical insight into the development of next-generation accelerators that use laser-driven plasma waves. These plasma-based accelerators offer a path to more compact, ultra-fast particle and radiation sources for probing the subatomic world, for studying new materials and new technologies, and for medical applications.

Geddes, Cameron G.R.; Cormier-Michel, Estelle; Esarey, Eric H.; Schroeder, Carl B.; Vay, Jean-Luc; Leemans, Wim P.; Bruhwiler, David L.; Cary, John R.; Cowan, Ben; Durant, Marc; Hamill, Paul; Messmer, Peter; Mullowney, Paul; Nieter, Chet; Paul, Kevin; Shasharina, Svetlana; Veitzer, Seth; Weber, Gunther; Rubel, Oliver; Ushizima, Daniela; Bethel, Wes; Wu, John

2009-03-20

204

Laser Guiding at Relativistic Intensities and Wakefield Particle Acceleration  

E-print Network

gas jet length as well as simulations indicate that the high quality beams were formed when beam formed by hydrodynamic shock were used to guide acceleration relevant laser intensities of at least 1E18

Geddes, Cameron Guy Robinson

205

Demonstration of two-beam acceleration in CTF II  

Microsoft Academic Search

The second phase of the Compact LInear Collider (CLIC) Test Facility (CTF II) at CERN has demon-strated the feasibility of two-beam acceleration at 30 GHz using a high-charge drive beam, running paral lel to the main beam, as the RF power source. To date accelerating gradients of 59 MV\\/m at 30 GHz have been achieved. In CTF II, the two

Rudolf Bossart; Hans Heinrich Braun; G. Carron; M. Chanudet; F. Chautard; J. P. Delahaye; J. C. Godot; S. Hutchins; I. Kamber; C. Martinez; Guy Suberlucq; P G Tenenbaum; L. Thorndahl; M. Valentini; Ian H Wilson; Walter Wuensch

1998-01-01

206

Strategies for mitigating the ionization-induced beam head erosion problem in an electron-beam-driven plasma wakefield accelerator  

NASA Astrophysics Data System (ADS)

Strategies for mitigating ionization-induced beam head erosion in an electron-beam-driven plasma wakefield accelerator (PWFA) are explored when the plasma and the wake are both formed by the transverse electric field of the beam itself. Beam head erosion can occur in a preformed plasma because of a lack of focusing force from the wake at the rising edge (head) of the beam due to the finite inertia of the electrons. When the plasma is produced by field ionization from the space charge field of the beam, the head erosion is significantly exacerbated due to the gradual recession (in the beam frame) of the 100% ionization contour. Beam particles in front of the ionization front cannot be focused (guided) causing them to expand as in vacuum. When they expand, the location of the ionization front recedes such that even more beam particles are completely unguided. Eventually this process terminates the wake formation prematurely, i.e., well before the beam is depleted of its energy. Ionization-induced head erosion can be mitigated by controlling the beam parameters (emittance, charge, and energy) and/or the plasma conditions. In this paper we explore how the latter can be optimized so as to extend the beam propagation distance and thereby increase the energy gain. In particular we show that, by using a combination of the alkali atoms of the lowest practical ionization potential (Cs) for plasma formation and a precursor laser pulse to generate a narrow plasma filament in front of the beam, the head erosion rate can be dramatically reduced. Simulation results show that in the upcoming “two-bunch PWFA experiments” on the FACET facility at SLAC national accelerator laboratory the energy gain of the trailing beam can be up to 10 times larger for the given parameters when employing these techniques. Comparison of the effect of beam head erosion in preformed and ionization produced plasmas is also presented.

An, W.; Zhou, M.; Vafaei-Najafabadi, N.; Marsh, K. A.; Clayton, C. E.; Joshi, C.; Mori, W. B.; Lu, W.; Adli, E.; Corde, S.; Litos, M.; Li, S.; Gessner, S.; Frederico, J.; Hogan, M. J.; Walz, D.; England, J.; Delahaye, J. P.; Muggli, P.

2013-10-01

207

Beam Line: 100 years of elementary particles  

Microsoft Academic Search

This issue of Beam Line commemorates the 100th anniversary of the April 30, 1897 report of the discovery of the electron by J.J. Thomson and the ensuing discovery of other subatomic particles. In the first three articles, theorists Abraham Pais, Steven Weinberg, and Chris Quigg provide their perspectives on the discoveries of elementary particles as well as the implications and

A. Pais; S. Weinberg; C. Quigg; M. Riordan; W. K. H. Panofsky

1997-01-01

208

Induced radioactivity in and around high-energy particle accelerators.  

PubMed

Particle accelerators and their surroundings are locations of residual radioactivity production that is induced by the interaction of high-energy particles with matter. This paper gives an overview of the principles of activation caused at proton accelerators, which are the main machines operated at Conseil Européen pour la Recherche Nucléaire. It describes the parameters defining radio-nuclide production caused by beam losses. The second part of the paper concentrates on the analytic calculation of activation and the Monte Carlo approach as it is implemented in the FLUKA code. Techniques used to obtain, on the one hand, estimates of radioactivity in Becquerel and, on the other hand, residual dose rates caused by the activated material are discussed. The last part of the paper focuses on experiments that allow for benchmarking FLUKA activation calculations and on simulations used to predict activation in and around high-energy proton machines. In that respect, the paper addresses the residual dose rate that will be induced by proton-proton collisions at an energy of two times 7 TeV in and around the Compact Muon Solenoid (CMS) detector. Besides activation of solid materials, the air activation expected in the CMS cavern caused by this beam operation is also discussed. PMID:21697180

Vincke, Helmut; Theis, Chris; Roesler, Stefan

2011-07-01

209

Design of a plasma discharge circuit for particle wakefield acceleration  

E-print Network

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV m^-1), enabling acceleration of electrons to GeV energy in few centimetres. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators; radiofrequency-based accelerators, in fact, are limited in the accelerating field (10-100 MV m^-1) requiring therefore kilometric distances to reach the GeV energies, but can provide very bright electron bunches. Combining high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of shor...

Anania, M P; Cianchi, A; Di Giovenale, D; Ferrario, M; Flora, F; Gallerano, G P; Ghigo, A; Marocchino, A; Massimo, F; Mostacci, A; Mezi, L; Musumeci, P; Serio, M; 10.1016/j.nima.2013.10.053

2014-01-01

210

A Simplified Model for the Acceleration of Cosmic Ray Particles  

ERIC Educational Resources Information Center

Two important questions concerning cosmic rays are: Why are electrons in the cosmic rays less efficiently accelerated than nuclei? How are particles accelerated to great energies in ultra-high energy cosmic rays? In order to answer these questions we construct a simple model of the acceleration of a charged particle in the cosmic ray. It is not…

Gron, Oyvind

2010-01-01

211

The ORNL radioactive ion beam project with the ORIC accelerator  

SciTech Connect

The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) for astrophysics, nuclear physics, and applied research with the Holifield Heavy Ion Research Facility (HHIRF) accelerators has been approved. Radioactive atoms will be produced by fusion reactions in an Isotope Separator On-Line (ISOL)type target-ion source assembly using light ion beams from the Oak Ridge Isochronous Cyclotron (ORIC). The radioactive atoms will be converted to negative ions using either (1) direct-surface ionization or (2) charge exchange following positive ionization. After acceleration to approximately 300 keV from a high-voltage platform, these negative ions will be injected into the 25-MV tandem accelerator for acceleration to higher energies. Beams of up to mass 80 will be accelerated to energies greater than 5 MeV/nucleon. For some radioactive beams. intensities greater than I pnA are possible.

Olsen, D.K.; Alton, G.D.; Baktash, C.; Dowling, D.T.; Garrett, J.D.; Haynes, D.L.; Jones, C.M.; Juras, R.C.; Lane, S.N.; Lee, I.Y.; Meigs, M.J.; Mills, G.D.; Mosko, S.W.; Tatum, B.A.; Toth, K.S. (Oak Ridge National Lab., TN (United States)); Carter, H.K.; Kormicki, J. (Oak Ridge Associated Universities, Inc., TN (United States))

1992-01-01

212

The ORNL radioactive ion beam project with the ORIC accelerator  

SciTech Connect

The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) for astrophysics, nuclear physics, and applied research with the Holifield Heavy Ion Research Facility (HHIRF) accelerators has been approved. Radioactive atoms will be produced by fusion reactions in an Isotope Separator On-Line (ISOL)type target-ion source assembly using light ion beams from the Oak Ridge Isochronous Cyclotron (ORIC). The radioactive atoms will be converted to negative ions using either (1) direct-surface ionization or (2) charge exchange following positive ionization. After acceleration to approximately 300 keV from a high-voltage platform, these negative ions will be injected into the 25-MV tandem accelerator for acceleration to higher energies. Beams of up to mass 80 will be accelerated to energies greater than 5 MeV/nucleon. For some radioactive beams. intensities greater than I pnA are possible.

Olsen, D.K.; Alton, G.D.; Baktash, C.; Dowling, D.T.; Garrett, J.D.; Haynes, D.L.; Jones, C.M.; Juras, R.C.; Lane, S.N.; Lee, I.Y.; Meigs, M.J.; Mills, G.D.; Mosko, S.W.; Tatum, B.A.; Toth, K.S. [Oak Ridge National Lab., TN (United States); Carter, H.K.; Kormicki, J. [Oak Ridge Associated Universities, Inc., TN (United States)

1992-09-01

213

Pulsed particle beam vacuum-to-air interface  

DOEpatents

A vacuum-to-air interface is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve, from which extends a vacuum-tight duct, that terminates in an aperture. Means are provided for periodically advancing a foil strip across the aperture at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band urges foil strip, when stationary, against and into the aperture. Gas pressure means periodically lift off and separate foil strip from aperture, so that it may be readily advanced. 5 figs.

Cruz, G.E.; Edwards, W.F.

1987-06-18

214

Merging for Particle-Mesh Complex Particle Kinetic Modeling of the Multiple Plasma Beams  

NASA Technical Reports Server (NTRS)

We suggest a merging procedure for the Particle-Mesh Complex Particle Kinetic (PMCPK) method in case of inter-penetrating flow (multiple plasma beams). We examine the standard particle-in-cell (PIC) and the PMCPK methods in the case of particle acceleration by shock surfing for a wide range of the control numerical parameters. The plasma dynamics is described by a hybrid (particle-ion-fluid-electron) model. Note that one may need a mesh if modeling with the computation of an electromagnetic field. Our calculations use specified, time-independent electromagnetic fields for the shock, rather than self-consistently generated fields. While a particle-mesh method is a well-verified approach, the CPK method seems to be a good approach for multiscale modeling that includes multiple regions with various particle/fluid plasma behavior. However, the CPK method is still in need of a verification for studying the basic plasma phenomena: particle heating and acceleration by collisionless shocks, magnetic field reconnection, beam dynamics, etc.

Lipatov, Alexander S.

2011-01-01

215

Radioactive beams with the HHIRF accelerators  

SciTech Connect

There is an increasing interest in radioactive ion beams for astrophysics and nuclear physics research and applied programs. This interest has led to an International Conference on Radioactive Nuclear Beams and a Workshop on the Science of Intense Radioactive Ion Beams. In addition, a steering committee has been formed to consider the development of a very large and intense RIB facility in North America to produce both proton- and neutron-rich beams. This report discusses development of these beams.

Olsen, D.K.; Alton, G.D.; Baktash, C.; Dowling, D.T.; Garrett, J.D.; Haynes, D.L.; Jones, C.M.; Juras, R.C., Lane, S.N.; Lee, I.Y.; Meigs, M.J.; Mills, G.D.; Mosko, S.W.; Tatum, B.A. Toth, K.S. (Oak Ridge National Lab., TN (USA)); Carter, H.K. (UNISOR, Oak Ridge, TN (USA))

1991-01-01

216

Diagnostic resonant cavity for a charged particle accelerator  

DOEpatents

Disclosed is a diagnostic resonant cavity for determining characteristics of a charged particle beam, such as an electron beam, produced in a charged particle accelerator. The cavity is based on resonant quadrupole-mode and higher order cavities. Enhanced shunt impedance in such cavities is obtained by the incorporation of a set of four or more electrically conductive rods extending inwardly from either one or both of the end walls of the cavity, so as to form capacitive gaps near the outer radius of the beam tube. For typical diagnostic cavity applications, a five-fold increase in shunt impedance can be obtained. In alternative embodiments the cavity may include either four or more opposing pairs of rods which extend coaxially toward one another from the opposite end walls of the cavity and are spaced from one another to form capacitative gaps; or the cavity may include a single set of individual rods that extend from one end wall to a point adjacent the opposing end wall.

Barov, Nikolai (San Diego, CA)

2007-10-02

217

High quality electron beams from a plasma channel guided laser wakefield accelerator  

SciTech Connect

Laser driven accelerators, in which particles are accelerated by the electric field of a plasma wave driven by an intense laser, have demonstrated accelerating electric fields of hundreds of GV/m. These fields are thousands of times those achievable in conventional radiofrequency (RF) accelerators, spurring interest in laser accelerators as compact next generation sources of energetic electrons and radiation. To date however, acceleration distances have been severely limited by lack of a controllable method for extending the propagation distance of the focused laser pulse. The ensuing short acceleration distance results in low energy beams with 100% electron energy spread, limiting applications. Here we demonstrate that a relativistically intense laser can be guided by a preformed plasma density channel and that the longer propagation distance can result in electron beams of percent energy spread with low emittance and increased energy, containing >10{sup 9} electrons above 80 MeV. The preformed plasma channel technique forms the basis of a new class of accelerators, combining beam quality comparable to RF accelerators with the high gradients of laser accelerators to produce compact tunable high brightness electron and radiation sources.

Geddes, C.G.R.; Toth, Cs.; van Tilborg, J.; Esarey, E.; Schroeder, C.B.; Bruhwiler, D.; Nieter, C.; Cary, J.; Leemans, W.P.

2004-07-08

218

Particle Accelerator Applications: Ion and Electron Irradiation in Materials Science, Biology and Medicine  

SciTech Connect

Although the developments of particle accelerators are devoted to basic study of matter constituents, since the beginning these machines have been applied with different purposes in many areas also. Today particle accelerators are essential instruments for science and technology. This work presents an overview of the main application for direct particle irradiation with accelerator in material science, biology and medicine. They are used for material synthesis by ion implantation and charged particle irradiation; to make coatings and micromachining; to characterize broad kind of samples by ion beam analysis techniques; as mass spectrometers for atomic isotopes determination. In biomedicine the accelerators are applied for the study of effects by charged particles on cells. In medicine the radiotherapy by electron irradiation is widely used, while hadrontherapy is still under development. Also, they are necessary for short life radioisotopes production required in radiodiagnostic.

Rodriguez-Fernandez, Luis [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, Mexico D.F., 01000 (Mexico)

2010-09-10

219

A beam energy analysis and monitoring system for linear accelerators  

SciTech Connect

A model-based beam orbit simulation program has been used successfully to analyze the beam energy errors at the two-mile linear accelerator during commissioning of the SLC system. This simulation program has also been used to develop a nondestructive beam energy error monitoring system. The method of analysis, the simulation program, and a beam energy analysis and monitoring system using expert systems techniques will be described.

Lee, M.J.; Kleban, S.D.; Zambre, Y.B.; Seeman, J.T.; Adolphsen, C.E.; Abrams, G.S.; Iverson, R.; Stanek, M.; Turner, J.L.; Blanchette, C.J.

1988-02-01

220

Particle beam generator using a radioactive source  

DOEpatents

The apparatus of the present invention selects from particles emitted by a radioactive source those particles having momentum within a desired range and focuses the selected particles in a beam having at least one narrow cross-dimension, and at the same time attenuates potentially disruptive gamma rays and low energy particles. Two major components of the present invention are an achromatic bending and focusing system, which includes sector magnets and quadrupole, and a quadrupole doublet final focus system. Permanent magnets utilized in the apparatus are constructed of a ceramic (ferrite) material which is inexpensive and easily machined.

Underwood, D.G.

1993-03-30

221

Particle beam generator using a radioactive source  

SciTech Connect

The apparatus of the present invention selects from particles emitted by a radioactive source those particles having momentum within a desired range and focuses the selected particles in a beam having at least one narrow cross-dimension, and at the same time attenuates potentially disruptive gamma rays and low energy particles. Two major components of the present invention are an achromatic bending and focusing system, which includes sector magnets and quadrupole, and a quadrupole doublet final focus system. Permanent magnets utilized in the apparatus are constructed of a ceramic (ferrite) material which is inexpensive and easily machined.

Underwood, D.G.

1991-12-31

222

Surfatron acceleration of a relativistic particle by electromagnetic plane wave  

E-print Network

We study motion of a relativistic charged particle in a plane slow electromagnetic wave and background uniform magnetic field. The wave propagates normally to the background field. Under certain conditions, the resonance between the wave and the Larmor motion of the particle is possible. Capture into this resonance results in acceleration of the particle along the wave front (surfatron acceleration). We analyse the phenomenon of capture and show that a captured particle never leaves the resonance and its energy infinitely grows. Scattering on the resonance is also studied. We find that this scattering results in diffusive growth of the particle energy. Finally, we estimate energy losses due to radiation by an accelerated particle.

A. I. Neishtadt; A. A. Vasiliev; A. V. Artemyev

2010-11-09

223

Accelerating Airy beams with non-parabolic trajectories  

NASA Astrophysics Data System (ADS)

A class of Airy accelerating beams with non-parabolic trajectories are derived by means of a novel application of a conformal transformation originally due to Bateman. It is also shown that the salient features of these beams are very simply incorporated in a solution which is derived by applying a conventional conformal transformation together with a Galilean translation to the basic accelerating Airy beam solution of the two-dimensional paraxial equation. Motivation for the non-parabolic beam trajectories is provided and the effects of finite-energy requirements are discussed.

Besieris, Ioannis M.; Shaarawi, Amr M.

2014-11-01

224

Particle acceleration by intense auroral VLF turbulence  

NASA Technical Reports Server (NTRS)

Broadband turbulence in the lower-hybrid to plasma frequency range is found in a variety of forms in the suprauroral region, most notably as auroral hiss and VLF saucers. When the turbulence is intense, it is observed to be associated with ion conics (ions heated transverse to the geomagnetic field) and 'counter-streaming' electron fluxes (heated in both directions parallel to the field). A review is presented of the dispersion and propagation characteristics of whistler resonance-cone waves, which comprise the turbulence. Plasma simulation and mesoscale (Monte Carlo) simulation techniques are used to illustrate the interaction of the ambient plasma with the turbulence. These calculations demonstrate how this interaction results in transverse heating of the ions and parallel heating of the electrons of the plasma, leading to the formation of the observed heated and accelerated particle fluxes.

Retterer, John M.; Jasperse, J. R.; Chang, Tom

1990-01-01

225

Plasma modeling of beam-electron cloud instabilities in circular accelerators  

Microsoft Academic Search

A 3D Particle-In-Cell model for continuous modeling of beam and electron cloud interaction in a circular accelerator is presented. A simple model for lattice structure, mainly the Quadruple and dipole magnets and chromaticity have been added to a plasma PIC code, QuickPIC, used extensively to model plasma wakefield acceleration concept. The code utilizes parallel processing techniques with domain decomposition in

Ali Ghalam

2005-01-01

226

G4beamline Particle Tracking in Matter Dominated Beam Lines  

SciTech Connect

The G4beamline program is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available at http://g4beamline.muonsinc.com

T.J. Roberts, K.B. Beard, S. Ahmed, D. Huang, D.M. Kaplan

2011-03-01

227

Linear Accelerators  

NASA Astrophysics Data System (ADS)

In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

Sidorin, Anatoly

2010-01-01

228

US Particle Accelerators at Age 50.  

ERIC Educational Resources Information Center

Reviews the development of accelerators over the past 50 years. Topics include: types of accelerators, including cyclotrons; sociology of accelerators (motivation, financing, construction, and use); impact of war; national laboratories; funding; applications; future projects; foreign projects; and international collaborations. (JN)

Wilson, R. R.

1981-01-01

229

Particle Acceleration in Relativistic Jets Due to Weibel Instability  

Microsoft Academic Search

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a three-dimensional relativistic electromagnetic particle code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient

K.-I. Nishikawa; P. Hardee; G. Richardson; R. Preece; H. Sol; G. J. Fishman

2003-01-01

230

Demonstration of two-beam acceleration in CTF II  

E-print Network

The second phase of the Compact LInear Collider (CLIC) Test Facility (CTF II) at CERN has demon-strated the feasibility of two-beam acceleration at 30 GHz using a high-charge drive beam, running paral lel to the main beam, as the RF power source. To date accelerating gradients of 59 MV/m at 30 GHz have been achieved. In CTF II, the two beams are generated by 3 GHz RF photo-injectors and are acceler ated in 3 GHz linacs, before injection into the 30 GHz modules. The drive beam linac has to accelerate a 16 ns long train of 48 bunches, each with a nominal charge of 13.4 nC. To cope with the very su bstantial beam-loading special accelerating structures are used (running slightly off the bunch repetition frequency). A magnetic chicane compresses the bunches to less than 5 ps fwhm, this is needed for efficient 30 GHz power generation. The 30 GHz modules are fully-engineered representative sections of CLIC, they include a 30 GHz decelerator for the drive beam, a 30 GHz accelerator for the main beam, high resolution...

Bossart, Rudolf; Carron, G; Chanudet, M; Chautard, F; Delahaye, J P; Godot, J C; Hutchins, S; Kamber, I; Martínez, C; Suberlucq, Guy; Tenenbaum, P G; Thorndahl, L; Valentini, M; Wilson, Ian H; Wuensch, Walter

1999-01-01

231

Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators  

NASA Astrophysics Data System (ADS)

The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Sc?rer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin, S Mangles, L O Silva, R Fonseca and P A Norreys Electro-optic shocks from blowout laser wakefields D F Gordon, A Ting, M H Helle, D Kaganovich and B Hafizi Onset of self-steepening of intense laser pulses in plasmas J Vieira, F Fiúza, L O Silva, M Tzoufras and W B Mori Analysis of laser wakefield dynamics in capillary tubes N E Andreev, K Cassou, F Wojda, G Genoud, M Burza, O Lundh, A Persson, B Cros, V E Fortov and C-G Wahlstrom Characterization of the beam loading effects in a laser plasma accelerator C Rechatin, J Faure, X Davoine, O Lundh, J Lim, A Ben-Ismaïl, F Burgy, A Tafzi, A Lifschitz, E Lefebvre and V Malka Energy gain scaling with plasma length and density in the plasma wakefield accelerator P Muggli, I Blumenfeld, C E Clayton, F J Decker, M J Hogan, C Huang, R Ischebeck, R H Iverson, C Joshi, T Katsouleas, N Kirby, W Lu, K A Marsh, W B Mori, E Oz, R H Siemann, D R Walz and M Zhou Generation of tens of GeV quasi-monoenergetic proton beams from a moving double layer formed by ultraintense lasers at intensity 1021-1023Wcm-2 Lu-Le Yu, Han Xu, Wei-Min Wang, Zheng-Ming Sheng, Bai-Fei Shen, Wei Yu and Jie Zhang Carbon ion acceleration from thin foil targets irradiated by ultrahigh-contrast, ultraintense laser pulses D C Carroll, O Tresca, R Prasad, L Romagnani, P S Foster, P Gallegos, S Ter-Avetisyan, J S Green, M J V Streeter, N Dover, C A J Palmer, C M Brenner, F H Cameron, K E Quinn, J Schreiber, A P L Robinson, T Baeva, M N Quinn, X H Yuan, Z Najmudin, M Zepf, D Neely, M Borghesi and P McKenna Numerical modelling of a 10-cm-long multi-GeV laser wakefield accelerator driven by a self-guided petawatt pulse S Y Kalmykov, S A Yi, A Beck, A F Lifschitz, X Davoine, E Lefebvre, A Pukhov, V Khudik, G Shvets, S A Reed, P Dong, X Wang, D Du, S Bedacht, R Zgadzaj, W Henderson, A Bernstein, G Dyer, M Martinez, E Gaul, T Ditmire and M C Downer Effects of laser prepulses on laser-induced proton generation D Batani, R Jafer, M Veltcheva, R Dezulian, O Lundh, F Lindau, A Persson, K Osvay, C-G Wahlström, D C Carroll, P McKenna, A Flacco and V Malka Proton accelerati

Joshi, Chan; Malka, Victor

2010-04-01

232

Advanced treatment planning methods for efficient radiation therapy with laser accelerated proton and ion beams  

SciTech Connect

Purpose: Laser plasma acceleration can potentially replace large and expensive cyclotrons or synchrotrons for radiotherapy with protons and ions. On the way toward a clinical implementation, various challenges such as the maximum obtainable energy still remain to be solved. In any case, laser accelerated particles exhibit differences compared to particles from conventional accelerators. They typically have a wide energy spread and the beam is extremely pulsed (i.e., quantized) due to the pulsed nature of the employed lasers. The energy spread leads to depth dose curves that do not show a pristine Bragg peak but a wide high dose area, making precise radiotherapy impossible without an additional energy selection system. Problems with the beam quantization include the limited repetition rate and the number of accelerated particles per laser shot. This number might be too low, which requires a high repetition rate, or it might be too high, which requires an additional fluence selection system to reduce the number of particles. Trying to use laser accelerated particles in a conventional way such as spot scanning leads to long treatment times and a high amount of secondary radiation produced when blocking unwanted particles. Methods: The authors present methods of beam delivery and treatment planning that are specifically adapted to laser accelerated particles. In general, it is not necessary to fully utilize the energy selection system to create monoenergetic beams for the whole treatment plan. Instead, within wide parts of the target volume, beams with broader energy spectra can be used to simultaneously cover multiple axially adjacent spots of a conventional dose delivery grid as applied in intensity modulated particle therapy. If one laser shot produces too many particles, they can be distributed over a wider area with the help of a scattering foil and a multileaf collimator to cover multiple lateral spot positions at the same time. These methods are called axial and lateral clustering and reduce the number of particles that have to be blocked in the beam delivery system. Furthermore, the optimization routine can be adjusted to reduce the number of dose spots and laser shots. The authors implemented these methods into a research treatment planning system for laser accelerated particles. Results: The authors' proposed methods can decrease the amount of secondary radiation produced when blocking particles with wrong energies or when reducing the total number of particles from one laser shot. Additionally, caused by the efficient use of the beam, the treatment time is reduced considerably. Both improvements can be achieved without extensively changing the quality of the treatment plan since conventional intensity modulated particle therapy usually includes a certain amount of unused degrees of freedom which can be used to adapt to laser specific properties. Conclusions: The advanced beam delivery and treatment planning methods reduce the need to have a perfect laser-based accelerator reproducing the properties of conventional accelerators that might not be possible without increasing treatment time and secondary radiation to the patient. The authors show how some of the differences to conventional beams can be overcome and efficiently used for radiation treatment.

Schell, Stefan; Wilkens, Jan J. [Department of Radiation Oncology, Technische Universitaet Muenchen, Klinikum Rechts der Isar, Ismaninger Str. 22, 81675 Muenchen (Germany)

2010-10-15

233

Wake-fields Induced by the Electron Beam Passing through theTESLA Accelerating System  

E-print Network

in 1990 [1]. The solution of an accelerating system is based up on superconducting RF structures operating. All interconnecting flexible beam tubes (bellows) are designed to be as smooth as possible. The shape of their longitudinal momentum. If exciting particle pass off the axis, also the transverse deflections are excited

234

Sterilization of Mail by Means of an Electron Beam Accelerator  

Microsoft Academic Search

In view of the recent cases of postal bioterrorism with the use of anthrax spores in sealed envelopes (see [11] and http:\\/\\/www. bt.cdc.gov), we experimentally checked and demonstrated the possibility of using an industrial electron beam accelerator for sterilization of mail. Industrial electron beam accelerators are widely used for sterilization of medical equipment, drugs, food, and packing materials. In some

V. L. Auslender; V. A. Vedernikov; M. A. Grachev; V. V. Drukker; A. I. Korchagin; E. P. Kruglyakov; A. M. Kudryavtsev; N. S. Kulikova; O. G. Netsvetaeva; O. N. Pavlova; V. V. Parfenova; E. A. Semenova; V. I. Serbin; I. A. Terkina; A. V. Tkov; E. P. Chebykin

2002-01-01

235

ISABELLE accelerator software, control system, and beam diagnostic philosophy  

SciTech Connect

The ISABELLE Project combines two large proton accelerators with two storage rings in the same facility using superconducting magnet technology. This combination leads to severe constraints on beam loss in magnets and involves complex treatment of magnetic field imperfections and correction elements. The consequent demands placed upon beam diagnostics, accelerator model programs, and the computer oriented control system are discussed in terms of an illustrative operation scenario.

Cornacchia, M.; Humphrey, J.W.; Niederer, J.; Poole, J.H.

1981-01-01

236

Transverse envelope analysis for accelerating relativistic electron beams in a linear accelerator as a photon source  

NASA Astrophysics Data System (ADS)

Since recent progress of electron guns extends the application of linear accelerators to photon radiation sources, the design and optimization of transverse beam optics over a linear accelerator become important. In this paper, we propose a transverse beam envelope analysis for accelerating beams in a linear accelerator using symplectic matrices based on a normalized emittance. This approach allows a description of the transverse envelope function, which reflects the characteristics of beam optics. Since the envelope function is described in the same phase space as photon radiation, it provides an effective and powerful tool for the design and optimization of the beam optics as a photon source. The emittance based formalism of the beam envelope, which was previously described by Douglas, Kewisch, and York, is first introduced for impulse acceleration, and then extended to a thick accelerator structure. The transverse beam envelope analyses, such as error sensitivity, chromatic aberration, and emittance growth, are presented by applying second-order perturbation treatment to a formulated matrix describing a quasi-periodic lattice in the linear accelerator system.

Hara, Toru; Togawa, Kazuaki; Tanaka, Hitoshi

2010-12-01

237

Secondary particle production from laser accelerated beams  

SciTech Connect

3-MeV protons and fusion neutrons are generated by focused radiation of the 3-TW Prague Asterix Laser System (PALS). 30-mA current of 3-MeV protons is detected behind the target in the forward direction when a hydrogenated silicon foil is used. The co-occurrence of bursts in the emission of ions and fusion neutrons from CD{sub 2} plasma is observed. The energy of produced deuteron bursts is high enough to drive deuterium fusion in CD{sub 2} catcher targets.

Krasa, Josef; Margarone, Daniele [Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic)

2012-07-09

238

High-power radio frequency pulse generation and extration based on wakefield excited by an intense charged particle beam in dielectric-loaded waveguides  

Microsoft Academic Search

Power extraction using a dielectric-loaded (DL) waveguide is a way to generate high-power radio frequency (RF) waves for future particle accelerators, especially for two-beam-acceleration. In a two-beam-acceleration scheme, a low-energy, high-current particle beam is passed through a deceleration section of waveguide (decelerator), where the power from the beam is partially transferred to trailing electromagnetic waves (wakefields); then with a properly

F. Gao

2009-01-01

239

Beam collimation and transport of quasineutral laser-accelerated protons by a solenoid field  

SciTech Connect

This article reports about controlling laser-accelerated proton beams with respect to beam divergence and energy. The particles are captured by a pulsed high field solenoid with a magnetic field strength of 8.6 T directly behind a flat target foil that is irradiated by a high intensity laser pulse. Proton beams with energies around 2.3 MeV and particle numbers of 10{sup 12} could be collimated and transported over a distance of more than 300 mm. In contrast to the protons the comoving electrons are strongly deflected by the solenoid field. They propagate at a submillimeter gyroradius around the solenoid's axis which could be experimentally verified. The originated high flux electron beam produces a high space charge resulting in a stronger focusing of the proton beam than expected by tracking results. Leadoff particle-in-cell simulations show qualitatively that this effect is caused by space charge attraction due to the comoving electrons. The collimation and transport of laser-accelerated protons is the first step to provide these unique beams for further applications such as postacceleration by conventional accelerator structures.

Harres, K.; Alber, I.; Guenther, M.; Nuernberg, F.; Otten, A.; Schuetrumpf, J.; Roth, M. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany); Tauschwitz, A.; Bagnoud, V. [Plasmaphysik and PHELIX, GSI-Helmholtzzentrum fuer Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt (Germany); Daido, H.; Tampo, M. [Photo Medical Research Center, JAEA, 8-1 Umemidai, Kizugawa City, Kyoto 619-0215 (Japan); Schollmeier, M. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2010-02-15

240

Acceleration of ampere class H(-) ion beam by MeV accelerator.  

PubMed

The H(-) ion accelerator R&D to realize the international thermonuclear experimental reactor neutral beam is ongoing at Japan Atomic Energy Agency (JAEA). The required performance for the prototype MeV accelerator developed at JAEA is 1 MeV, 500 mA (current density of 200 A/m(2)) H(-) ion beam at the beamlet divergence angle of less than 7 mrad. Up to 2005, 836 keV, 146 A/m(2) H(-) ion beam was successfully accelerated as the highest record of the current density at MeV class energy beams. In the present work, high current negative ion beam acceleration test was performed by increasing the beam extraction apertures from 3 x 3 (9 apertures) to 3 x 5 (15 apertures). By fixing the air leak at the source chamber due to backstream ions as well as the improvement of voltage holding capability by a new fiber reinforced plastic insulator ring, the performance of the MeV accelerator was improved. So far, H(-) ion beam of 320 mA was successfully accelerated up to 796 keV with the beam divergence angle of 5.5 mrad. The accelerated drain current including the electron reaches close to the power supply limit for the MeV test facility. The heat flux by the backstream ion during the above beam acceleration was estimated to be 360 W/cm(2). The Cs leakage to the accelerator during the test campaign (Cs total input of 5.0 g) was 0.26 mg (7.0 microg/cm(2)). This is considered to be the allowable level from the viewpoint of voltage holding. PMID:18315236

Taniguchi, M; Inoue, T; Umeda, N; Kashiwagi, M; Watanabe, K; Tobari, H; Dairaku, M; Sakamoto, K

2008-02-01

241

Solar Particle Source Energy spectrum: Stochastic acceleration vs Neutral Current Sheet acceleration vs Shock Wave acceleration  

NASA Astrophysics Data System (ADS)

It has been shown in a series of works that some solar particle events (SPE) are composed of two different relativistic populations, a Prompt Component (PC) and a Delayed Component (DC), each one with different energy spectrum behavior. The source spectra of the DC tend to be an inverse power law at the steady state situation, whereas the spectra of the PC are considerable deviated from such a power law. Here we attempt to reproduce the observational spectra of the PC and the DC on terms of different scenarios: (i) DC acceleration from magnetic merging in a Magnetic Neutral Current Sheet (MNCS). (ii) Stochastic acceleration of an injected population pre-accelerated in a MNCS. (iii) Stochastic acceleration with monoenergetic injection. (iv) Stochastic acceleration with monoenergetic injection, while undergoing adiabatic deceleration. We contrast our results with those assuming Shock Wave Acceleration. Results are illustrated for the case of the September 29, 1989, July 14, 2000, October 28, 2003 and January 20, 2005 Ground Level Events (GLE`s).

Perez-Peraza, J. A.; Gallegos-Cruz, A.; Vashenyuk, E. V.; Miroshnichenko, L. I.

2007-05-01

242

Alternative options for beam cooling for a muon accelerator  

E-print Network

1 Alternative options for beam cooling for a muon accelerator front-end Diktys Stratakis Physics for a Muon Accelerator · Recent engineering studies suggest to: · Increase the gap between coils in buncher cavities · Results do not seem sensitive to rf gradient, phase and absorber length variations. Optimum

McDonald, Kirk

243

High Power Particle Beams and Pulsed Power for Industrial Applications  

NASA Astrophysics Data System (ADS)

Several industrial scale projects with economic and ecologic potential are presently emanating from research and development in the fields of high power particle beams and pulsed power in Europe. Material surface modifications with large area pulsed electron beams are used to protect high temperature gas turbine blades and steel structures in Pb/Bi cooled accelerator driven nuclear reactor systems against oxidation and corrosion respectively. Channel spark electron beams are applied to deposit bio-compatible or bio-active layers on medical implants. Cell membranes are perforated with strong pulsed electric fields to extract nutritive substances or raw materials from the cells and to kill bacteria for sterilization of liquids. Eletrodynamic fragmentation devices are developed to reutilize concrete aggregates for the production of high quality secondary concrete. All activities have a large potential to contribute to a more sustainable economy.

Bluhm, Hansjoachim; An, Wladimir; Engelko, Wladimir; Giese, Harald; Frey, Wolfgang; Heinzel, Annette; Hoppé, Peter; Mueller, Georg; Schultheiss, Christoph; Singer, Josef; Strässner, Ralf; Strauß, Dirk; Weisenburger, Alfons; Zimmermann, Fritz

2002-12-01

244

Fluence and dose measurements for an accelerator neutron beam  

NASA Astrophysics Data System (ADS)

The 3 MV Van de Graaff accelerator at McMaster University accelerator laboratory is extended to a neutron irradiation facility for low-dose bystander effects research. A long counter and an Anderson-Braun type neutron monitor have been used as monitors for the determination of the total fluence. Activation foils were used to determine the thermal neutron fluence rate (around 10 6 neutrons s -1). Meanwhile, the interactions of neutrons with the monitors have been simulated using a Monte Carlo N Particle (MCNP) code. Bystander effects, i.e. damage occurring in cells that were not traversed by radiation but were in the same radiation environment, have been well observed following both alpha and gamma irradiation of many cell lines. Since neutron radiation involves mixed field (including gamma and neutron radiations), we need to differentiate the doses for the bystander effects from the two radiations. A tissue equivalent proportional counter (TEPC) filled with propane based tissue equivalent gas simulating a 2 ?m diameter tissue sphere has been investigated to estimate the neutron and gamma absorbed doses. A photon dose contamination of the neutron beam is less than 3%. The axial dose distribution follows the inverse square law and lateral and vertical dose distributions are relatively uniform over the irradiation area required by the biological study.

Liu, Z.; Byun, S. H.; McNeill, F. E.; Mothersill, C. E.; Seymour, C. B.; Prestwich, W. V.

2007-10-01

245

Education in a rapidly advancing technology: Accelerators and beams  

NASA Astrophysics Data System (ADS)

The field of accelerators and beams (A&B) is one of today's fast changing technologies. Because university faculties have not been able to keep pace with the associated advancing knowledge, universities have not been able to play their traditional role of educating the scientists and engineers needed to sustain this technology for use in science, industry, commerce, and defense. This problem for A&B is described and addressed. The solution proposed, a type of "distance" education, is the U.S. Particle Accelerator School (USPAS) created in the early 1980s. USPAS provides the universities with a means of serving the education needs of the institutions using A&B, primarily but not exclusively the national laboratories. The field of A&B is briefly summarized. The need for education outside the university framework, the raison d'être for USPAS, the USPAS method, program structure, and curriculum, and particular USPAS-university connections are explained. The management of USPAS is analyzed, including its unique administrative structure, its institutional ties, and its operations, finance, marketing, and governmental relations. USPAS performance over the years is documented and a business assessment is made. Finally, there is a brief discussion of the future potential for this type of educational program, including possible extrapolation to new areas and/or different environments, in particular, its extra-government potential and its international possibilities.

Month, Mel

2000-06-01

246

Cresting Algorithm Using Fourier Analysis of Beam Position for CEBAF Accelerator  

NASA Astrophysics Data System (ADS)

The Continuous Electron Beam Accelerator Facility (CEBAF) accelerator contains two linear accelerators with Radio frequency (RF) cavities to accelerate electrons. For this to happen, the maxima of the sinusoidal electric fields in each cavity must be precisely matched to the timing of the particle's trajectories. Optimization of the beam energy is achieved by modulating the phase of cavities one at a time until the electrons are observed have the maximum energy. The focus of this project is to improve the process of finding the crest (maxima) phase of multiple cavities by modulating several cavities simultaneously. This was done by modulating the phase of each cavity at a different frequency and observing the position of the beam. The position of the beam over the period of modulation was then Fourier Transformed, producing peaks at the frequencies that corresponded to the different cavities. This was repeated with different amplitudes of modulation to fit a relationship between the amplitude of modulation and the Fourier Transform spike amplitude, which contained phase information. It has been shown that multiple cavities can be crested at the same time through the phase modulation of cavities at different frequencies and Fourier transforming the positions of the resulting beam. This has ramifications for accelerator operation because it dramatically decreases tuning time needed for beam optimization.

Roussel, Ryan; Roblin, Yves

2012-10-01

247

A Low Energy Beam Transport Design with high SCC for TAC Proton Accelerator  

E-print Network

In this study, a low energy beam transport (LEBT) channel for the proton linac section of the Turkic Accelerator Complex (TAC) has been designed by using TRACE 2D and TRAVEL codes. The LEBT channel is located between an ion source and a radio frequency quadrupole (RFQ) structure. The aims of the design studies are perfect matching between input and output beams with two solenoid magnets, small emittance growth and sufficient space for beam diagnostics. Total length of such LEBT channel is about 1.3 m. The current of H- ion beam from ion source is 80 mA. In the beam dynamical simulations, we have taken into account some space charge compensation (SCC) factors between %93.75 and %100. The results of both codes have been compared for the selected SCC factors. Additionally, beam aperture study for % 95 SCC factor has been done to discard unwanted particles and increase the beam brightness.

Caliskan, A; Sultansoy, S; Yilmaz, M

2012-01-01

248

Polarization of fast particle beams by collisional pumping  

DOEpatents

Method and apparatus for highly polarizing a fast beam of particles by collisional pumping, including generating a fast beam of particles, and also generating a thick electron-spin-polarized medium positioned as a target for the beam. The target is made sufficiently thick to allow the beam to interact with the medium to produce collisional pumping whereby the beam becomes highly polarized.

Stearns, J. Warren (Castro Valley, CA); Kaplan, Selig N. (El Cerrito, CA); Pyle, Robert V. (Berkeley, CA); Anderson, L. Wilmer (Madison, WI); Ruby, Lawrence (Berkeley, CA); Schlachter, Alfred S. (Oakland, CA)

1988-01-01

249

Beam Line: 100 years of elementary particles  

NASA Astrophysics Data System (ADS)

This issue of Beam Line commemorates the 100th anniversary of the April 30, 1897 report of the discovery of the electron by J.J. Thomson and the ensuing discovery of other subatomic particles. In the first three articles, theorists Abraham Pais, Steven Weinberg, and Chris Quigg provide their perspectives on the discoveries of elementary particles as well as the implications and future directions resulting from these discoveries. In the following three articles, Michael Riordan, Wolfgang Panofsky, and Virginia Trimble apply our knowledge about elementary particles to high-energy research, electronics technology, and understanding the origin and evolution of our Universe.

Pais, A.; Weinberg, S.; Quigg, C.; Riordan, M.; Panofsky, W. K. H.

1997-04-01

250

Levy-Student Distributions for Halos in Accelerator Beams  

E-print Network

We describe the transverse beam distribution in particle accelerators within the controlled, stochastic dynamical scheme of the Stochastic Mechanics (SM) which produces time reversal invariant diffusion processes. This leads to a linearized theory summarized in a Shchr\\"odinger--like (\\Sl) equation. The space charge effects have been introduced in a recent paper \\cite{prstab} by coupling this \\Sl equation with the Maxwell equations. We analyze the space charge effects to understand how the dynamics produces the actual beam distributions, and in particular we show how the stationary, self--consistent solutions are related to the (external, and space--charge) potentials both when we suppose that the external field is harmonic (\\emph{constant focusing}), and when we \\emph{a priori} prescribe the shape of the stationary solution. We then proceed to discuss a few new ideas \\cite{epac04} by introducing the generalized Student distributions, namely non--Gaussian, L\\'evy \\emph{infinitely divisible} (but not \\emph{sta...

Petroni, N C; De Siena, S; Illuminati, F

2005-01-01

251

Generation of multi-giga-electron-volt monoenergetic electron beams via laser wakefield acceleration  

NASA Astrophysics Data System (ADS)

In plasma-based acceleration a particle bunch surfs a plasma wave, driven by a laser or a particle beam, in order to achieve high energy in a very short distance. Powerful modern drivers create strongly nonlinear wavefields in which the plasma electrons are radially expelled. These wakefields can generate well-defined particle beams in what is referred to as the "blowout" regime. In this dissertation we study with theory and simulations some key physics of the blowout regime and offer methods for designing plasma-based accelerators which are stable, efficient and generate particle beams with good quality. Starting from a phenomenological theory, originally presented in Ref. [51], which includes the concepts of nonlinear multi-dimensional wake excitation, local pump depletion, dephasing and laser guiding, we design laser wakefield accelerators which accelerate electron beams efficiently in a single stage. Simulations carried out using the Particle-In-Cell (PIC) code QuickPIC confirm much of the theoretical predictions. They show that in this nonlinear blowout regime, the laser excites a stable wake over distances hundreds of Rayleigh lengths long, as long as its spot size and duration are properly matched, kpw0 = optauL = 2a0. In the simulations a0 is held fixed at 2 and the plasma density is decreased while the spot size is kept matched. Stages that provide an average gradient 3.6GV/m (7.2 GV/m) with a final energy of 100GeV (25 GeV) were demonstrated. We discuss the optimal laser profile of an ultraintense pulse used for plasma-based acceleration and develop a method for describing how such a laser evolves. The first beam loading theory for electrons in nonlinear wakes is developed starting from the work in Ref. [48, 49]. By assuming that the blowout radius is large, analytical solutions for the shape of the bubble and the loaded wakefield are derived. It is found analytically and confirmed in PIC simulations with OSIRIS, that beam-loading efficiencies exceeding 90% can be achieved while the energy spread of the accelerating electron bunch is essentially conserved for trapezoidally-shaped trailing beams. Analytical solutions for flat-top current profiles are also calculated and it is found through simulations that the results are similar to those for Gaussian-shaped beams. Based on these solutions the amount of loaded charge is calculated for a given acceleration gradient.

Tzoufras, Michail

252

Beam dynamics in the Advanced Test Accelerator (ATA)  

SciTech Connect

We will review the performance of the Advanced Test Accelerator, a 50 MeV, 10 KA induction linac. The discussion will cover the operation of the plasma cathode electron source, beam transport throughout the accelerator, and transverse instabilities. Particular emphasis will be placed on the beam breakup instability and on the methods used to minimize it. These include a program of design changes that lead to an order of magnitude reduction in the Q's of the accelerator cavity modes and optimization of the transport tune.

Caporaso, G.J.; Barletta, W.A.; Birx, D.L.; Briggs, R.J.; Chong, Y.P.; Cole, A.G.; Fessenden, T.J.; Hester, R.E.; Lauer, E.J.; Neil, V.K.

1983-09-28

253

High transformer ratio drive beams for wakefield accelerator studies  

SciTech Connect

For wakefield based acceleration schemes, use of an asymmetric (or linearly ramped) drive bunch current profile has been predicted to enhance the transformer ratio and generate large accelerating wakes. We discuss plans and initial results for producing such bunches using the 20 to 23 GeV electron beam at the FACET facility at SLAC National Accelerator Laboratory and sending them through plasmas and dielectric tubes to generate transformer ratios greater than 2 (the limit for symmetric bunches). The scheme proposed utilizes the final FACET chicane compressor and transverse collimation to shape the longitudinal phase space of the beam.

England, R. J.; Ng, C.-K.; Frederico, J.; Hogan, M. J.; Litos, M.; Muggli, P.; Joshi, C.; An, W.; Andonian, G.; Mori, W.; Lu, W. [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Max Planck Institute for Physics, 80805 Munich (Germany); University of California Los Angeles, Los Angeles, CA 90095 (United States); Tsinghua University, Beijing (China)

2012-12-21

254

High transformer ratio drive beams for wakefield accelerator studies  

NASA Astrophysics Data System (ADS)

For wakefield based acceleration schemes, use of an asymmetric (or linearly ramped) drive bunch current profile has been predicted to enhance the transformer ratio and generate large accelerating wakes. We discuss plans and initial results for producing such bunches using the 20 to 23 GeV electron beam at the FACET facility at SLAC National Accelerator Laboratory and sending them through plasmas and dielectric tubes to generate transformer ratios greater than 2 (the limit for symmetric bunches). The scheme proposed utilizes the final FACET chicane compressor and transverse collimation to shape the longitudinal phase space of the beam.

England, R. J.; Ng, C.-K.; Frederico, J.; Hogan, M. J.; Litos, M.; Muggli, P.; Joshi, C.; An, W.; Andonian, G.; Mori, W.; Lu, W.

2012-12-01

255

SLAC National Accelerator Laboratory Experimental Particle Physics Faculty Search  

E-print Network

SLAC National Accelerator Laboratory Experimental Particle Physics Faculty Search The SLAC National Particle Physics in its Particle Physics and Astrophysics (PPA) Directorate. The search is at the tenured of PPA's ongoing programs in experimental particle physics, or to initiate a new program in line with PPA

Wechsler, Risa H.

256

Cavitation Inception on Microparticles: A Self-Propelled Particle Accelerator  

Microsoft Academic Search

Corrugated, hydrophilic particles with diameters between 30 and 150 mum are found to cause cavitation inception at their surfaces when they are exposed to a short, intensive tensile stress wave. The growing cavity accelerates the particle into translatory motion until the tensile stress decreases, and subsequently the particle separates from the cavity. The cavity growth and particle detachment are modeled

Manish Arora; Claus-Dieter Ohl; Knud Aage Mørch

2004-01-01

257

Nonlinear dynamics aspects of particle accelerators  

SciTech Connect

This book contains 18 selections. Some of the titles are: Integrable and Nonintegrable Hamiltonian Systems; Nonlinear Dynamics Aspects of Modern Storage Rings; Nonlinear Beam-Beam Resonances; Synchro-Betatron Resonances; Review of Beam-Beam Simulations; and Perturbation Method in Nonlinear Dynamics.

Araki, H.; Ehlers, J.; Hepp, K.; Kippenhahn, R.; Weidenmuller, A.; Zittartz, J.

1986-01-01

258

Particle trajectories and acceleration during 3D fan reconnection  

E-print Network

Context. The primary energy release in solar flares is almost certainly due to magnetic reconnection, making this a strong candidate as a mechanism for particle acceleration. While particle acceleration in 2D geometries has been widely studied, investigations in 3D are a recent development. Two main classes of reconnection regimes at a 3D magnetic null point have been identified: fan and spine reconnection Aims. Here we investigate particle trajectories and acceleration during reconnection at a 3D null point, using a test particle numerical code, and compare the efficiency of the fan and spine regimes in generating an energetic particle population. Methods. We calculated the time evolution of the energy spectra. We discuss the geometry of particle escape from the two configurations and characterise the trapped and escaped populations. Results. We find that fan reconnection is less efficent than spine reconnection in providing seed particles to the region of strong electric field where acceleration is possible...

Dalla, S; 10.1051/0004-6361:200809771

2008-01-01

259

Rapidly Accelerating Mathieu and Weber Surface Plasmon Beams  

NASA Astrophysics Data System (ADS)

We report the generation of two types of self-accelerating surface plasmon beams which are solutions of the nonparaxial Helmholtz equation in two dimensions. These beams preserve their shape while propagating along either elliptic (Mathieu beam) or parabolic (Weber beam) trajectories. We show that owing to the nonparaxial nature of the Weber beam, it maintains its shape over a much larger distance along the parabolic trajectory, with respect to the corresponding solution of the paraxial equation—the Airy beam. Dynamic control of the trajectory is realized by translating the position of the illuminating free-space beam. Finally, the ability of these beams to self-heal after blocking obstacles is demonstrated as well.

Libster-Hershko, Ana; Epstein, Itai; Arie, Ady

2014-09-01

260

Rapidly accelerating mathieu and weber surface plasmon beams.  

PubMed

We report the generation of two types of self-accelerating surface plasmon beams which are solutions of the nonparaxial Helmholtz equation in two dimensions. These beams preserve their shape while propagating along either elliptic (Mathieu beam) or parabolic (Weber beam) trajectories. We show that owing to the nonparaxial nature of the Weber beam, it maintains its shape over a much larger distance along the parabolic trajectory, with respect to the corresponding solution of the paraxial equation-the Airy beam. Dynamic control of the trajectory is realized by translating the position of the illuminating free-space beam. Finally, the ability of these beams to self-heal after blocking obstacles is demonstrated as well. PMID:25279631

Libster-Hershko, Ana; Epstein, Itai; Arie, Ady

2014-09-19

261

Advanced Visualization Technology for Terascale Particle Accelerator Simulations  

E-print Network

Advanced Visualization Technology for Terascale Particle Accelerator Simulations Kwan-Liu Ma £ Greg Accelerator Center Lawrence Berkeley National Laboratory Abstract This paper presents two new hardware modeling of next- generation accelerator designs. The first technique, based on a hybrid rendering approach

Ma, Kwan-Liu

262

Experimental demonstration of dielectric structure based two beam acceleration.  

SciTech Connect

We report on the experimental results of the dielectric based two beam accelerator (step-up transformer). By using a single high charge beam, we have generated and extracted a high power RF pulse from a 7.8 GHz primary dielectric structure and then subsequently transferred to a second accelerating structure with higher dielectric constant and smaller transverse dimensions. We have measured the energy change of a second (witness) beam passing through the acceleration stage. The measured gradient is >4 times the deceleration gradient. The detailed experiment of set-up and results of the measurements are dimmed. Future plans for the development of a 100 MeV demonstration accelerator based on this technique is presented.

Gai, W.; Conde, M. E.; Konecny, R.; Power, J. G.; Schoessow, P.; Sun, X.; Zou, P.

2000-11-28

263

Particle trajectories and acceleration during 3D fan reconnection  

Microsoft Academic Search

Context: The primary energy release in solar flares is almost certainly due to magnetic reconnection, making this a strong candidate as a mechanism for particle acceleration. While particle acceleration in 2D geometries has been widely studied, investigations in 3D are a recent development. Two main classes of reconnection regimes at a 3D magnetic null point have been identified: fan and

S. Dalla; P. K. Browning

2008-01-01

264

ENERGETIC PARTICLE ACCELERATION AND RADIATION IN EVOLVING COMPLEX ACTIVE REGIONS  

E-print Network

with respect to number of electric fields present and the thermal temperature of the initially injected71 ENERGETIC PARTICLE ACCELERATION AND RADIATION IN EVOLVING COMPLEX ACTIVE REGIONS A.Anastasiadis1 for the acceleration and radiation of solar energetic particles (electrons) in an evolving active region. The spatio

Anastasiadis, Anastasios

265

Particle acceleration in collisionless shocks - Regulated injection and high efficiency  

Microsoft Academic Search

Particle acceleration in supernova remnants and radio galaxies proceeds with high efficiency, and at the same time puts out most of the cosmic ray power at moderately relativistic energies. This suggests that there is a regulated injection mechanism that selects only a very small fraction of particles out of the thermal pool, but enough that, when accelerated to moderately relativistic

D. Eichler

1979-01-01

266

Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron  

E-print Network

Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron A Research Centre develops, builds and operates large accelerator facilities for photon science and particle physics of the Helmholtz Association ASTROPARTICLE PHYSICS· DESY, Zeuthen location, is seeking: Scientist (f/m) DESY DESY

267

Heavy-ion beam dynamics in the RIA accelerators  

NASA Astrophysics Data System (ADS)

The Nuclear Science Community in the United States has unanimously concluded that developments in both nuclear science and its supporting technologies make building a Rare-Isotope Accelerator (RIA) facility for production of radioactive beams. The RIA development effort involves several US Laboratories (ANL, JLAB, LANL, LBNL, MSU, ORNL). The RIA project includes a continuous wave 1.4 GV driver linac and a 123 MV post-accelerator, both based on superconducting (SC) cavities operating at frequencies from 48 to 805 MHz. Several new conceptual solutions in physics design of heavy-ion SC linacs have been developed recently. In particular, the concept of multiple charge state beam acceleration in SC linacs was tested and will be used in the driver linac to increase available accelerated beam power. A detailed design has been developed for the focusing-accelerating lattice of the RIA linacs which are configured as an array of short SC cavities, each with independently controllable RF phase. Independent phasing allows the velocity profile to be varied: the linac can be tuned to provide higher energies for the lighter ions. For example, the reference design linac can be tuned to provide a uranium beam at an energy of 403 MeV/ u and can be re-tuned to provide a proton beam at 900 MeV. The linac must provide 100 kW beam power with the possibility to upgrade up to 400 kW.

Ostroumov, P. N.

2004-02-01

268

Transformer ratio improvement for beam based plasma accelerators  

SciTech Connect

Increasing the transformer ratio of wakefield accelerating systems improves the viability of present novel accelerating schemes. The use of asymmetric bunches to improve the transformer ratio of beam based plasma systems has been proposed for some time[1, 2] but suffered from lack appropriate beam creation systems. Recently these impediments have been overcome [3, 4] and the ability now exists to create bunches with current profiles shaped to overcome the symmetric beam limit of R {<=} 2. We present here work towards experiments designed to measure the transformer ratio of such beams, including theoretical models and simulations using VORPAL (a 3D capable PIC code) [5]. Specifically we discuss projects to be carried out in the quasi-nonlinear regime [6] at the UCLA Neptune Laboratory and the Accelerator Test Facility at Brookhaven National Lab.

O'Shea, Brendan; Rosenzweig, James; Barber, Samuel; Fukasawa, Atsushi; Williams, Oliver; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl [University of California, Los Angeles, Department of Physics and Astronomy, Los Angeles, CA 90095 (United States); University of Southern California, Department of Electrical Engineering, Los Angeles, CA 90089 U.S.A. and Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen (Germany); Accelerator Test Facility, Brookhaven National Lab, Upton, NY, 11973 (United States)

2012-12-21

269

Accelerators  

NSDL National Science Digital Library

What is the purpose of particle accelerators? On this web page, part of a particle physics tutorial, students read that accelerators solve two problems. The accelerators provide an increase in momentum to produce particles of small wavelength, and the fast-moving particles can create new particles when smashed together. A photograph of the inside of a particle accelerator is provided. Copyright 2005 Eisenhower National Clearinghouse

Group, Lawrence B.

2002-01-01

270

PARTICLE ACCELERATION DURING MAGNETOROTATIONAL INSTABILITY IN A COLLISIONLESS ACCRETION DISK  

SciTech Connect

Particle acceleration during the magnetorotational instability (MRI) in a collisionless accretion disk was investigated by using a particle-in-cell simulation. We discuss the important role that magnetic reconnection plays not only on the saturation of MRI but also on the relativistic particle generation. The plasma pressure anisotropy of p > p{sub ||} induced by the action of MRI dynamo leads to rapid growth in magnetic reconnection, resulting in the fast generation of nonthermal particles with a hard power-law spectrum. This efficient particle acceleration mechanism involved in a collisionless accretion disk may be a possible model to explain the origin of high-energy particles observed around massive black holes.

Hoshino, Masahiro, E-mail: hoshino@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033 (Japan)

2013-08-20

271

Beam brilliance investigation of high current ion beams at GSI heavy ion accelerator facility.  

PubMed

In this work the emittance measurements of high current Ta-beam provided by VARIS (Vacuum Arc Ion Source) ion source are presented. Beam brilliance as a function of beam aperture at various extraction conditions is investigated. Influence of electrostatic ion beam compression in post acceleration gap on the beam quality is discussed. Use of different extraction systems (single aperture, 7 holes, and 13 holes) in order to achieve more peaked beam core is considered. The possible ways to increase the beam brilliance are discussed. PMID:24593461

Adonin, A A; Hollinger, R

2014-02-01

272

Testing General Relativity With Laser Accelerated Electron Beams  

E-print Network

Electron accelerations of the order of $10^{21} g$ obtained by laser fields open up the possibility of experimentally testing one of the cornerstones of general relativity, the weak equivalence principle, which states that the local effects of a gravitational field are indistinguishable from those sensed by a properly accelerated observer in flat space-time. We illustrate how this can be done by solving the Einstein equations in vacuum and integrating the geodesic equations of motion for a uniformly accelerated particle.

L. Á. Gergely; T. Harko

2012-07-16

273

High efficiency beam splitting for H/sup -/ accelerators  

SciTech Connect

Beam splitting for high energy accelerators has typically involved a significant loss of beam and radiation. This paper reports on a new method of splitting beams for H/sup -/ accelerators. This technique uses a high intensity flash of light to strip a fraction of the H/sup -/ beam to H/sup 0/ which are then easily separated by a small bending magnet. A system using a 900-watt (average electrical power) flashlamp and a highly efficient collector will provide 10/sup -3/ to 10/sup -2/ splitting of a 50 MeV H/sup -/ beam. Results on the operation and comparisons with stripping cross sections are presented. Also discussed is the possibility for developing this system to yield a higher stripping fraction.

Kramer, S.L.; Stipp, V.; Krieger, C.; Madsen, J.

1985-01-01

274

Acceleration Statistics of Neutrally Buoyant Spherical Particles in Intense Turbulence  

NASA Astrophysics Data System (ADS)

We measure acceleration statistics of neutrally buoyant spherical particles with a diameter 0.4particles in a flow between counterrotating disks. The measurements of acceleration variance ?a2? clearly resolve the transition from the tracer like behavior of small particles to the much smaller accelerations of large particles. Two models of this transition from small to large particle behavior are critically examined. For d>5?, ?a2? decreases with the diameter as d-2/3, in agreement with inertial range scaling arguments. Consistent with earlier work, we find that the scaled acceleration probability density function shows very little dependence on particle size.

Brown, Rachel D.; Warhaft, Z.; Voth, Greg A.

2009-11-01

275

Possibility for ultra-bright electron beam acceleration in dielectric wakefield accelerators  

SciTech Connect

We describe a conceptual proposal to combine the Dielectric Wakefield Accelerator (DWA) with the Emittance Exchanger (EEX) to demonstrate a high-brightness DWA with a gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam. We currently evaluate the DWA concept as a performance upgrade for the future LANL signature facility MaRIE with the goal of significantly reducing the electron beam energy spread. The preconceptual design for MaRIE is underway at LANL, with the design of the electron linear accelerator being one of the main research goals. Although generally the baseline design needs to be conservative and rely on existing technology, any future upgrade would immediately call for looking into the advanced accelerator concepts capable of boosting the electron beam energy up by a few GeV in a very short distance without degrading the beam's quality. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerators for free-electron lasers. We describe simulations demonstrating that trapezoidal bunch shapes can be used in a DWA to greatly reduce the induced beam energy spread, and, in doing so, also preserve the beam brightness at levels never previously achieved. This concept has the potential to advance DWA technology to a level that would make it suitable for the upgrades of the proposed Los Alamos MaRIE signature facility.

Simakov, Evgenya I.; Carlsten, Bruce E.; Shchegolkov, Dmitry Yu. [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545 (United States)

2012-12-21

276

Long pulse H- ion beam acceleration in MeV accelerator.  

PubMed

A multiaperture multigrid accelerator called "MeV accelerator" has been developed for neutral beam injection system of international thermonuclear experimental reactor. In the present work, long pulse H(-) ion beam acceleration was performed by the MeV accelerator equipped with new water-cooled grids. At present, the pulse length was extended to 5 s for the beams of 750 keV, 221 mA, and 10 s for the beams of 600 keV, 158 mA. Energy density, defined as products of beam energy (keV), current (mA), and pulse (s) divided by aperture area (m(2)), increased more than one order of magnitude higher compared with original MeV accelerator without water cooling in its grids. At higher energy and current, the grid was melted by beam deflection. Due to this grid melting, breakdowns occurred between the grids, and hence, the pulse length was limited. Beam deflection will be compensated by aperture displacement in next experiment. PMID:20192408

Taniguchi, M; Mizuno, T; Umeda, N; Kashiwagi, M; Watanabe, K; Tobari, H; Kojima, A; Tanaka, Y; Dairaku, M; Hanada, M; Sakamoto, K; Inoue, T

2010-02-01

277

Possibility for ultra-bright electron beam acceleration in dielectric wakefield accelerators  

NASA Astrophysics Data System (ADS)

We describe a conceptual proposal to combine the Dielectric Wakefield Accelerator (DWA) with the Emittance Exchanger (EEX) to demonstrate a high-brightness DWA with a gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam. We currently evaluate the DWA concept as a performance upgrade for the future LANL signature facility MaRIE with the goal of significantly reducing the electron beam energy spread. The preconceptual design for MaRIE is underway at LANL, with the design of the electron linear accelerator being one of the main research goals. Although generally the baseline design needs to be conservative and rely on existing technology, any future upgrade would immediately call for looking into the advanced accelerator concepts capable of boosting the electron beam energy up by a few GeV in a very short distance without degrading the beam's quality. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerators for free-electron lasers. We describe simulations demonstrating that trapezoidal bunch shapes can be used in a DWA to greatly reduce the induced beam energy spread, and, in doing so, also preserve the beam brightness at levels never previously achieved. This concept has the potential to advance DWA technology to a level that would make it suitable for the upgrades of the proposed Los Alamos MaRIE signature facility.

Simakov, Evgenya I.; Carlsten, Bruce E.; Shchegolkov, Dmitry Yu.

2012-12-01

278

Earth's Most Powerful Natural Particle Accelerator  

NASA Technical Reports Server (NTRS)

Thunderstorms launch antimatter, gamma rays, and highly energetic electrons and neutrons to the edge of space. This witches' brew of radiation is generated at the edge of the stratopause, by the strong electric fields associated with lightning discharges. In less than a quarter millisecond, an explosive feedback process takes an initial seed population of electrons, perhaps produced by cosmic rays from dying stars, and amplifies them a billion billion-fold in the rarefied air over high altitude thunderheads. The electrons generate gamma radiation as they travel through the stratosphere and lower mesosphere, momentarily brighter and of harder spectrum than cosmic gamma ray bursts. These electrons ultimately are absorbed by the atmosphere, but the gamma rays continue on, into the upper reaches of the atmosphere, where they in turn generate a new population of electrons, positrons, and energetic neutrons. These secondary electrons and positrons move along the magnetic field, and can reach near-earth space, streaming through the inner radiation belts, and possibly contributing to the trapped populations there. First postulated by Wilson in 1925, and serendipitously discovered by the Compton Gamma Ray Observatory in 1994 [Fishman et al.], these events, known as "Terrestrial Gamma ray Flashes" (TGFs), represent the most intense episodes of particle acceleration on or near the Earth, resulting in electrons with energies up to 100 MeV. Recent observations by the RHESSI [Smith et al., 2004], Fermi [Briggs et al., 2010], and AGILE [Tavani et al., 2011] satellites, and theoretical and computational modeling, have suggested that the relativistic runaway electron avalanche (RREA) mechanism [Gurevich, 1992], and important modifications, such as the relativistic feedback discharge (RFD) model [Dwyer 2012] can best explain the observations at present. In these models, strong thunderstorm electric fields drive seed electrons, generated from cosmic ray interactions, into a runaway discharge, in which the seed electrons continually gain energy from the electric field, creating a host of secondaries as they interact with the background atmospheric gas. The feedback mechanisms include backwards-propagating positrons and gamma rays, which then can generate new "seed" electrons at the base of the acceleration region, and themselves generate further avalanche chain reactions, greatly amplifying the initial seed population. All these processes happen in the stratosphere, in the altitude range near 15-20 km, where the electric fields and mean free paths are appropriate to allow the discharge to develop.

Rowland, Doug

2012-01-01

279

Design for low beam loss in accelerators for intense neutron source applications  

SciTech Connect

Control of beam loss in intense ion linacs involves keeping beam spill below parts in 10[sup [minus]5]--10[sup [minus]8]/m by preventing total beam size from extending to the limiting apertures. Starting from good rms design practices, new analysis of the machine architecture is described in terms of the effects of the machine tune with space-charge, free-energy constraint, and halo-producing mechanisms. It is shown that halos are produced by the time- (or position-) varying nature of common linac aspects (such as misalignment, mismatching, acceleration, and construction techniques) through collective core/single-particle interaction dynamics plus resonances.

Jameson, R.A.

1993-01-01

280

Design for low beam loss in accelerators for intense neutron source applications  

SciTech Connect

Control of beam loss in intense ion linacs involves keeping beam spill below parts in 10{sup {minus}5}--10{sup {minus}8}/m by preventing total beam size from extending to the limiting apertures. Starting from good rms design practices, new analysis of the machine architecture is described in terms of the effects of the machine tune with space-charge, free-energy constraint, and halo-producing mechanisms. It is shown that halos are produced by the time- (or position-) varying nature of common linac aspects (such as misalignment, mismatching, acceleration, and construction techniques) through collective core/single-particle interaction dynamics plus resonances.

Jameson, R.A.

1993-06-01

281

Effects of solar cycle on auroral particle acceleration  

NASA Astrophysics Data System (ADS)

We present the results of two studies designed to assess the effect of solar cycle on auroral particle acceleration processes. The first study is of data obtained from the S3-3 satellite at geocentric distances from 1.3 to 2.2 Re during solar minimum and the rising phase of the solar cycle. The S3-3 study included electrostatic shocks, ion beams and conics, and electron beams, but did not include ion composition. The second study is of data obtained by the ISEE-1 satellite when the ion mass spectrometer was operating in a special mode designed to study auroral ion distributions. This study covers geocentric distances from ˜2.5 to 7 Re during solar maximum and includes O+ and H+ beams and conics, and electrostatic shocks and low frequency turbulence. The S3-3 statistics for shocks with ion beams imply that the auroral parallel potential drop usually occurs above ˜2.2 Re at solar maximum, while the ISEE-1 observations suggest the potential drop, at solar maximum, may be located at ˜2.5 to 4 Re. The ISEE-1 beam observations (usually at energies less than or equal to 1 keV) imply that the potential drop is less, on average, for solar maximum than for solar minimum. Both data sets provide evidence for increased perpendicular acceleration of ions during solar maximum, associated with electrostatic shocks and enhanced low frequency turbulence. The ISEE-1 data show that the flux of upflowing O+ continues to increase as F10.7 increases from "low" to "high" solar maximum. These data also provide evidence that the ion two-stream instability is important in modifying the ion distributions. Most of these observations may be understood as being due to increased heating of the atmosphere during solar maximum which results in an increase in the H+ - O+ charge exchange altitude and an increase in the ionospheric density and temperature. Some effects, including the F10.7 dependence of the local time distribution of electrostatic shocks and the apparent decrease in the magnitude of the auroral potential drop at solar maximum, are still not understood.

Cattell, C. A.; Nguyen, T.; Temerin, M.; Lennartsson, W.; Peterson, W.

282

Induction accelerators and free-electron lasers at LLNL: Beam Research Program  

SciTech Connect

Linear induction accelerators have been developed to produce pulses of charged particles at voltages exceeding the capabilities of single-stage, diode-type accelerators and at currents too high rf accelerators. In principle, one can accelerate charged particles to arbitrarily high voltages using a multistage induction machine. The advent of magnetic pulse power systems makes sustained operation at high repetition rates practical, and high-average-power capability is very likely to open up many new applications of induction machines. In Part A of this paper, we survey the US induction linac technology, emphasizing electron machines. We also give a simplified description of how induction machines couple energy to the electron beam to illustrate many general issues that designers of high-brightness and high-average-power induction linacs must consider. We give an example of the application of induction accelerator technology to the relativistic klystron, a power source for high-gradient accelerators. In Part B we address the application of LIAs to free-electron lasers. The multikiloampere peak currents available from linear induction accelerators make high-gain, free-electron laser amplifier configurations feasible. High extraction efficiencies in a single mass of the electron beam are possible if the wiggler parameters are appropriately ''tapered'', as recently demonstrated at millimeter wavelengths on the 4-MeV ELF facility. Key issues involved in extending the technology to shorter wavelengths and higher average powers are described. Current FEL experiments at LLNL are discussed. 5 refs., 16 figs.

Briggs, R.J.

1989-02-15

283

Irradiation damage to the beam window in the 800MWth accelerator-driven system  

NASA Astrophysics Data System (ADS)

Irradiation damage to the beam window in the concept of 800MWth accelerator-driven system is evaluated. Heat produced in the window is also evaluated. Transport of proton and neutron up to 3.0 GeV is calculated by both PHITS that is the Monte Carlo code for particles and heavy ions and TWODANT that is two-dimensional deterministic transport code. The beam window is irradiated at the center of the accelerator-driven system with 20 MW proton beam power and neutron from the core during 300 full power days. Heat, displacement per atom, production rate of hydrogen and helium isotopes, and neutron and proton fields are estimated, assuming the Gaussian and flat beam profiles.

Nishihara, Kenji; Kikuchi, Kenji

2008-06-01

284

Electron trapping and acceleration by the plasma wakefield of a self-modulating proton beam  

E-print Network

It is shown that co-linear injection of electrons or positrons into the wakefield of the self-modulating particle beam is possible and ensures high energy gain. The witness beam must co-propagate with the tail part of the driver, since the plasma wave phase velocity there can exceed the light velocity, which is necessary for efficient acceleration. If the witness beam is many wakefield periods long, then the trapped charge is limited by beam loading effects. The initial trapping is better for positrons, but at the acceleration stage a considerable fraction of positrons is lost from the wave. For efficient trapping of electrons, the plasma boundary must be sharp, with the density transition region shorter than several centimeters. Positrons are not susceptible to the initial plasma density gradient.

Lotov, K V; Petrenko, A V; Amorim, L D; Vieira, J; Fonseca, R A; Silva, L O; Gschwendtner, E; Muggli, P

2014-01-01

285

ALPI Setup as the SPES Accelerator of Exotic Beams  

NASA Astrophysics Data System (ADS)

The SPES (Selective Production of Exotic Species) project for a national exotic beam facility in Legnaro includes pivotal upgrades of the existing superconducting linac ALPI (Acceleratore Lineare Per Ioni), to make it appropriate as the RIB (Radioactive Ion Beam) accelerator. The new injector, consisting of an Electron Cyclotron Resonance (ECR)-type charge breeder and a radiofrequency quadrupole (RFQ), will be described. Upgrade measures in ALPI to improve beam transmission and final energy, and handle low-intensity RIB will be explained, with the aim of increasing transmission to T > 90%, Ef by ~ 20%, reaching 10 MeV/u for the reference beam 132Sn.

Bisoffi, G.; Bassato, G.; Battistella, A.; Bermudez, J.; Bortolato, D.; Canella, S.; Chalykh, B.; Comunian, M.; Facco, A.; Fagotti, E.; Galatà, A.; Giacchini, M.; Gramegna, F.; Lamy, T.; Modanese, P.; Palmieri, A.; Pengo, R.; Pisent, A.; Poggi, M.; Porcellato, A.; Roncolato, C.; Scarpa, D.

2014-03-01

286

Polarization of fast particle beams by collisional pumping  

DOEpatents

The invention relates to method and apparatus for polarizing a fast beam of particles by collisional pumping, including generating a fast beam of particles, and generating a thick electron-spin-polarized medium positioned as a target for said beam, said medium being sufficiently thick to allow said beam to interact with said medium to produce collisional pumping whereby said particle beam becomes highly polarized.

Stearns, J.W.; Kaplan, S.N.; Pyle, R.V.; Anderson, L.W.; Schlachter, A.S.; Ruby, L.

1984-10-19

287

Ion acceleration and abundance enhancements by electron beam instabilities in impulsive solar flares  

NASA Astrophysics Data System (ADS)

We show that a nonrelativistic electron beam in a hydrogen-helium solar flare plasma will excite H(+) electromagnetic ion cyclotron, shear Alfven, and R-X waves, in addition to waves resulting from the two-stream instability. The H(+) electromagnetic ion cyclotron and shear Alfven waves are able to selectively accelerate ambient He-3 and Fe, respectively, to MeV energies through first harmonic gyroresonance, and thereby account for the large (He-3)/(He-4) and Fe/C ratios seen in the energetic particles from impulsive solar flares. In this model, separate heating and acceleration mechanisms for either He-3 or Fe are not required, and Fe acceleration is quite efficient since it does not need to occur by second harmonic gyroresonance. The combination of the other two unstable modes is able to accelerate ions to hundreds of MeV if the particles become trapped in an electrostatic potential well of a two-stream wave.

Miller, James A.; Vinas, Adolfo F.

1993-07-01

288

Ion acceleration and abundance enhancements by electron beam instabilities in impulsive solar flares  

NASA Technical Reports Server (NTRS)

We show that a nonrelativistic electron beam in a hydrogen-helium solar flare plasma will excite H(+) electromagnetic ion cyclotron, shear Alfven, and R-X waves, in addition to waves resulting from the two-stream instability. The H(+) electromagnetic ion cyclotron and shear Alfven waves are able to selectively accelerate ambient He-3 and Fe, respectively, to MeV energies through first harmonic gyroresonance, and thereby account for the large (He-3)/(He-4) and Fe/C ratios seen in the energetic particles from impulsive solar flares. In this model, separate heating and acceleration mechanisms for either He-3 or Fe are not required, and Fe acceleration is quite efficient since it does not need to occur by second harmonic gyroresonance. The combination of the other two unstable modes is able to accelerate ions to hundreds of MeV if the particles become trapped in an electrostatic potential well of a two-stream wave.

Miller, James A.; Vinas, Adolfo F.

1993-01-01

289

Electron Accelerators for Radioactive Ion Beams  

SciTech Connect

The summary of this paper is that to optimize the design of an electron drive, one must: (a) specify carefully the user requirements--beam energy, beam power, duty factor, and longitudinal and transverse emittance; (b) evaluate different machine options including capital cost, 10-year operating cost and delivery time. The author is convinced elegant solutions are available with existing technology. There are several design options and technology choices. Decisions will depend on system optimization, in-house infrastructure and expertise (e.g. cryogenics, SRF, lasers), synergy with other programs.

Lia Merminga

2007-10-10

290

Particle acceleration in time-developing magnetic reconnection process  

Microsoft Academic Search

Particle trajectories and acceleration are numerically studied in time-varying electric and magnetic fields that are obtained by a previous MHD simulation of an externally driven reconnection. Electron and proton orbits are traced under the influence of the developing reconnection fields for various initial particle positions and velocities. A method of continuation of local analytic solution in a particle-pushing algorithm is

Tetsuya Sato; Hiroshi Matsumoto; Keisuke Nagai

1982-01-01

291

H-mode Accelerating Structures with PMQ Focusing for Low-Beta Beams  

SciTech Connect

We report on results of the project developing high-efficiency normal-conducting RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of IH-PMQ structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. The H-PMQ accelerating structures following a short RFQ can be used both in the front end of ion linacs or in stand-alone applications. Results of the combined 3-D modeling -- electromagnetic computations, beam-dynamics simulations with high currents, and thermal-stress analysis -- for a full IH-PMQ accelerator tank are presented. The accelerating field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of EM and beamdynamics modeling. Multi-particle simulations withParmela and CST Particle Studio have been used to confirm the design. Measurement results of a cold model of the IH-PMQ tank are presented.

Kurennoy, Sergey S. [Los Alamos National Laboratory; O'Hara, James F. [Los Alamos National Laboratory; Olivas, Eric R. [Los Alamos National Laboratory; Rybarcyk, Lawrence J. [Los Alamos National Laboratory

2011-01-01

292

GeV electron beams from a cm-scale accelerator  

SciTech Connect

GeV electron accelerators are essential to synchrotron radiation facilities and free electron lasers, and as modules for high-energy particle physics. Radio frequency based accelerators are limited to relatively low accelerating fields (10-50 MV/m) and hence require tens to hundreds of meters to reach the multi-GeV beam energies needed to drive radiation sources, and many kilometers to generate particle energies of interest to the frontiers of high-energy physics.Laser wakefield accelerators (LWFA) in which particles are accelerated by the field of a plasma wave driven by an intense laser pulse produce electric fields several orders of magnitude stronger (10-100 GV/m) and so offer the potential of very compact devices. However, until now it has not been possible to maintain the required laser intensity, and hence acceleration, over the several centimeters needed to reach GeV energies.For this reason laser-driven accelerators have to date been limited to the 100 MeV scale. Contrary to predictions that PW-class lasers would be needed to reach GeV energies, here we demonstrate production of a high-quality electron beam with 1 GeV energy by channeling a 40 TW peak power laser pulse in a 3.3 cm long gas-filled capillary discharge waveguide. We anticipate that laser-plasma accelerators based on capillary discharge waveguides will have a major impact on the development of future femtosecond radiation sources such as x-ray free electron lasers and become a standard building block for next generation high-energy accelerators.

Leemans, W.P.; Nagler, B.; Gonsalves, A.J.; Toth, C.; Nakamura,K.; Geddes, C.G.R.; Esarey, E.B.; Schroeder, C.; Hooker, S.M.

2006-05-04

293

Using Nonlinear RF Acceleration for FEL Beam Conditioning  

SciTech Connect

We consider a new approach to condition an electron beam using nonlinear effects in the RF field. We demonstrate that such effects can generate a desirable--for the FEL interaction--radial variation of the particle's energy in the beam, and calculate the induced energy spread in the limit of weak field.

Stupakov, G.; Huang, Z.; /SLAC

2005-12-14

294

Shock Surface Undulation and Particle Acceleration at Oblique Shocks  

NASA Astrophysics Data System (ADS)

Considering the average Parker spiral magnetic field configuration, CME-driven interplanetary (IP) shocks within 1 AU should have oblique portions over much of their domain. Indeed, CME-driven shocks observed close to Earth are often oblique. However, it is well known that the standard diffusive shock acceleration mechanism, which relies on self-consistent wave generation via upstream propagating ions and their scattering, becomes increasingly inefficient with greater shock normal angle. Not only is a higher threshold energy required for the ions to leave the shock upstream, but also, approximately-parallel propagating waves are more quickly convected back into the shock, and the growth rate for waves propagating normal to the shock (the ones with the largest convective growth) decreases. As a result, typical, small-scale hybrid simulations of oblique shocks only show a dilute upstream beam, similar to what is often observed at the oblique Earth's bow shock - and no scattered, highly-energized ions. On the other hand, there are many "energetic storm particle" (ESP) events associated with oblique shocks that have significant fluxes of energetic ions. Recently, we have found that when run for a long time, our hybrid simulations (kinetic ions, electron fluid) show that the initial, weak beam is sufficient to generate compressive, steepening upstream waves. These waves are capable of disturbing the shock surface, resulting in an undulation that is propagating along the surface and growing in amplitude over time. The process is akin to that of the well-known reformation occurring at sufficiently strong quasi-parallel shocks. However, here the perturbations require at least two dimensions, show a strong spatial correlation, and travel along the shock surface. This process not only leads to enhanced ion acceleration, but also means that the shock characteristics are difficult to pinpoint, observationally: both the local jumps and the shock normal angle are highly variable. Shock undulation is also of interest to electron acceleration, since the undulated surface gives locally much larger shock normal angles and provides multiple mirroring and escape opportunities to accelerated electrons. We compare our simulations with a set of oblique shocks that we compiled from ACE observations, and discuss the results in the context of developing quantitative models of the flux and spectrum of energetic ions at IP shocks.

Krauss-Varban, D.; Li, Y.; Luhmann, J. G.

2006-12-01

295

Plasma flow and fast particles in a hypervelocity accelerator - A color presentation. [micrometeoroid simulation  

NASA Technical Reports Server (NTRS)

A new concept for particle acceleration for micrometeoroid simulation was developed at NASA Marshall Space Flight Center, using a high-density self-luminescent fast plasma flow to accelerate glass beads (with a diameter up to 1.0 mm) to velocities between 15-20 km/sec. After a short introduction to the operation of the hypervelocity range, the eight-converter-camera unit used for the photographs of the plasma flow and the accelerated particles is described. These photographs are obtained with an eight-segment reflecting pyramidal beam splitter. Wratten filters were mounted between the beam splitter and the converter tubes of the cameras. The photographs, which were recorded on black and white film, were used to make the matrices for the dye-color process, which produced the prints shown.

Igenbergs, E. B.; Cour-Palais, B.; Fisher, E.; Stehle, O.

1975-01-01

296

Beam loading and cavity compensation for the ground test accelerator  

SciTech Connect

The Ground Test Accelerator (GTA) will be a heavily beam-loaded H/sup minus/ linac with tight tolerances on accelerating field parameters. The methods used in modeling the effects of beam loading in this machine are described. The response of the cavity to both beam and radio-frequency (RF) drive stimulus is derived, including the effects of cavity detuning. This derivation is not restricted to a small-signal approximation. An analytical method for synthesizing a predistortion network that decouples the amplitude and phase responses of the cavity is also outlined. Simulation of performance, including beam loading, is achieved through use of a control system analysis software package. A straightforward method is presented for extrapolating this work to model large coupled structures with closely spaced parasitic modes. Results to date have enabled the RF control system designs for GTA to be optimized and have given insight into their operation. 6 refs., 10 figs.

Jachim, S.P.; Natter, E.F.

1989-01-01

297

Transport and acceleration of high current uranium ion beams  

SciTech Connect

Measurements have been made of the transport of beams produced by the high current ion source, MEVVA, and of the injection of these beams into the GSI heavy ion RFQ linac. This configuration has provided initial tests of the MEVVA ion source in an injector environment, and of the RFQ with uranium as the accelerated species. Beam currents of 78 mA of titanium and 19 mA of uranium, at an extraction voltage of 40 kV, have been transported through a 4.7 m long beam transport channel, and up to 40 mA of uranium has been transported through a single-gap accelerating column at a voltage of about 150 kV. A current of up to 5 mA of UT has been measured at the exit detector of the RFQ.

Brown, I.G.; Galvin, J.E.; Keller, R.; Spaedtke, P.; Mueller, R.W; Bolle, J.

1985-10-01

298

A Phenomenological Cost Model for High Energy Particle Accelerators  

E-print Network

Accelerator-based high-energy physics have been in the forefront of scientific discoveries for more than half a century. The accelerator technology of the colliders has progressed immensely, while the beam energy, luminosity, facility size, and cost have grown by several orders of magnitude. The method of colliding beams has not fully exhausted its potential but has slowed down considerably in its progress. In this paper we derive a simple scaling model for the cost of large accelerators and colliding beam facilities based on costs of 17 big facilities which have been either built or carefully estimated. Although this approach cannot replace an actual cost estimate based on an engineering design, this parameterization is to indicate a somewhat realistic cost range for consideration of what future frontier accelerator facilities might be fiscally realizable.

Vladimir Shiltsev

2014-04-15

299

Theoretical and Computational Investigation of Periodically Focused Intense Charged-Particle Beams  

SciTech Connect

The purpose of this report is to summarize results of theoretical and computational investigations of periodically focused intense charged-particle beams in parameter regimes relevant to the development of advanced high-brightness, high-power accelerators for high-energy physics research. The breakthroughs and highlights in our research in the period from April 1, 2010 to March 30, 2013 were: a) Theory and simulation of adiabatic thermal Child-Langmuir flow; b) Particle-in-cell simulations of adiabatic thermal beams in periodic solenoidal focusing field; c)Dynamics of charged particles in an adiabatic thermal beam equilibrium in a periodic solenoidal focusing field; d) Training of undergraduate researchers and graduate student in accelerator and beam physics. A brief introduction and summary is presented. Detailed descriptions of research results are provided in an appendix of publications at the end of the report.

Chen, Chiping [Massachusetts Institute of Technology

2013-06-26

300

Optimization and beam control in large-emittance accelerators: Neutrino factories;  

SciTech Connect

Schemes for intense sources of high-energy muons require collection, rf capture, and transport of particle beams with unprecedented emittances, both longitudinally and transversely. These large emittances must be reduced or ''cooled'' both in size and in energy spread before the muons can be efficiently accelerated. Therefore, formation of muon beams sufficiently intense to drive a Neutrino Factory or Muon Collider requires multi-stage preparation. Further, because of the large beam phase space which must be successfully controlled, accelerated, and transported, the major stages that comprise such a facility: proton driver, production, capture, phase rotation, cooling, acceleration, and storage are complex and strongly interlinked. Each of the stages must be consecutively matched and simultaneously optimized with upstream and downstream systems, meeting challenges not only technically in the optics and component design, but also in the modeling of both new and extended components. One design for transverse cooling, for example, employs meter-diameter solenoids to maintain strong focusing--300-500 mr beam divergences--across ultra-large momentum ranges, {ge} {+-}20% {delta}p/p, defying conventional approximations to the dynamics and field representation. To now, the interplay of the different systems and staging strategies has not been formally addressed. This work discusses two basic, but different approaches to a Neutrino Factory and how the staging strategy depends on beam parameters and method of acceleration.

Carol Johnstone

2004-08-23

301

Pulsed particle beam vacuum-to-air interface  

DOEpatents

A vacuum-to-air interface (10) is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve (18), from which extends a vacuum-tight duct (26), that termintes in an aperture (28). Means (32, 34, 36, 38, 40, 42, 44, 46, 48) are provided for periodically advancing a foil strip (30) across the aperture (28) at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band (62) urges foil strip (30), when stationary, against and into the aperture (28). Gas pressure means (68, 70) periodically lift off and separate foil strip (30) from aperture (28), so that it may be readily advanced.

Cruz, Gilbert E. (Pleasanton, CA); Edwards, William F. (Livermore, CA)

1988-01-01

302

Stochastic particle acceleration and the problem of backgroud plasma overheating  

E-print Network

The origin of hard X-ray (HXR) excess emission from clusters of galaxies is still an enigma, whose nature is debated. One of the possible mechanism to produce this emission is the bremsstrahlung model. However, previous analytical and numerical calculations showed that in this case the intracluster plasma had to be overheated very fast because suprathermal electrons emitting the HXR excess lose their energy mainly by Coulomb losses, i.e., they heat the background plasma. It was concluded also from these investigations that it is problematic to produce emitting electrons from a background plasma by stochastic (Fermi) acceleration because the energy supplied by external sources in the form of Fermi acceleration is quickly absorbed by the background plasma. In other words the Fermi acceleration is ineffective for particle acceleration. We revisited this problem and found that at some parameter of acceleration the rate of plasma heating is rather low and the acceleration tails of non-thermal particles can be gene...

Chernyshov, D O; Ko, C M

2012-01-01

303

Accelerators for the PS neutrino beam  

NASA Astrophysics Data System (ADS)

A recent memorandum for an experimental proposal [1] was discussed during the CERN PS and SPS experimental committee (SPSC) of April 2011 and at the Research Board of June 2011. The proposed experiment, with objective to investigate the anomalous ?? ? ?e oscillations, aims at re-using the discontinued CERN PS Neutrino Facility (PSNF) and experimental zones to install a 150 ton liquid argon time projection chamber (LArTPC) as near detector and a 600 ton LArTPC as far detector. This article will summarize the experimental needs, the proposed facility layout, a primary beam production scheme and the requirements for the reconstruction of the PSNF.

Steerenberg, R.; Calviani, M.; Gschwendtner, E.; Pardons, A.; Vincke, H.

2013-02-01

304

Investigation of accelerated neutral atom beams created from gas cluster ion beams  

NASA Astrophysics Data System (ADS)

A new concept for ultra-shallow processing of surfaces known as accelerated neutral atom beam (ANAB) technique employs conversion of energetic gas cluster ions produced by the gas cluster ion beam (GCIB) method into intense collimated beams of coincident neutral gas atoms having controllable average energies from less than 10 eV per atom to beyond 100 eV per atom. A beam of accelerated gas cluster ions is first produced as is usual in GCIB, but conditions within the source ionizer and extraction regions are adjusted such that immediately after ionization and acceleration the clusters undergo collisions with non-ionized gas atoms. Energy transfer during these collisions causes the energetic cluster ions to release many of their constituent atoms. An electrostatic deflector is then used to eliminate charged species, leaving the released neutral atoms to still travel collectively at the same velocities they had as bonded components of their parent clusters. Upon target impact, the accelerated neutral atom beams produce effects similar to those normally associated with GCIB, but to shallower depths, with less surface damage and with superior subsurface interfaces. The paper discusses generation and characterization of the accelerated neutral atom beams, describes interactions of the beams with target surfaces, and presents examples of ongoing work on applications for biomedical devices.

Kirkpatrick, A.; Kirkpatrick, S.; Walsh, M.; Chau, S.; Mack, M.; Harrison, S.; Svrluga, R.; Khoury, J.

2013-07-01

305

Seventy Five Years of Particle Accelerators (LBNL Summer Lecture Series)  

ScienceCinema

Summer Lecture Series 2006: Andy Sessler, Berkeley Lab director from 1973 to 1980, sheds light on the Lab's nearly eight-decade history of inventing and refining particle accelerators, which continue to illuminate the nature of the universe.

Sessler, Andy

2011-04-28

306

Particle Acceleration in Gamma-Ray Burst Jets  

E-print Network

Gradual shear acceleration of energetic particles in gamma-ray burst (GRB) jets is considered. Special emphasis is given to the analysis of universal structured jets, and characteristic acceleration timescales are determined for a power-law and a Gaussian evolution of the bulk flow Lorentz factor $\\gamma_b$ with angle $\\phi$ from the jet axis. The results suggest that local power-law particle distributions may be generated and that higher energy particles are generally concentrated closer to the jet axis. Taking several constraints into account we show that efficient electron acceleration in gradual shear flows, with maximum particle energy successively decreasing with time, may be possible on scales larger than $r \\sim 10^{15}$ cm, provided the jet magnetic field becomes sufficiently weak and/or decreases rapidly enough with distance, while efficient acceleration of protons to ultra-high energies $> 10^{20}$ eV may be possible under a wide range of conditions.

Frank M. Rieger; Peter Duffy

2005-09-16

307

Laser-Driven Proton Beams: Acceleration Mechanism, Beam Optimization, and Radiographic Applications  

Microsoft Academic Search

This paper reviews recent experimental activity in the area of optimization, control, and application of laser-accelerated proton beams, carried out at the Rutherford Appleton Laboratory and the Laboratoire pour lpsilaUtilisation des Lasers Intenses 100 TW facility in France. In particular, experiments have investigated the role of the scale length at the rear of the plasma in reducing target-normal-sheath-acceleration acceleration efficiency.

Marco Borghesi; Carlo Alberto Cecchetti; Toma Toncian; Julien Fuchs; Lorenzo Romagnani; Satyabrata Kar; P. A. Wilson; Patrizio Antici; Patrick Audebert; Erik Brambrink; Ariane Pipahl; Munib Amin; Ralph Jung; Jens Osterholz; Oswald Willi; Wigen Nazarov; Robert J. Clarke; Margaret Notley; David Neely; Patrick Mora; Thomas Grismayer; Guy Schurtz; Angelo Schiavi; Yasuhiko Sentoku

2008-01-01

308

Acceleration of energetic charged particles: Shocks, reconnection or turbulence?  

NASA Astrophysics Data System (ADS)

Acceleration of energetic charged charged particles, most-often with power-law energy spectra occurs everywhere is space where particle-particle collision mean free paths are significantly larger than their gyro-radii. Shocks, reconnection events and turbulence have variously been proposed as acceleration mechanisms, and each must currently be considered a viable mechanism. Shocks have the advantage that they produce naturally power-law spectra in the observed range which are not very sensitive to the parameters. They are usually also fast accelerators. I first discuss the constraints which observations place on the acceleration mechanisms and show that there are both temporal and spatial constraints. Stochastic acceleration tends to be slow, so the rate of acceleration is important. In the inner heliosphere, this rate must exceed the rate of adiabatic cooling ~ 2Vw/r, where Vw is the radial solar-wind velocity. Acceleration of anomalous cosmic rays (ACR) in the heliosheath must occur on a time scale of on year to avoid producing too many multiply charged ACR. It is shown that here, stochastic acceleration has difficulties in the inner heliosheath. Reconnection events are essentially incompressible, so the divergence of the flow velocity is nearly zero, and the Parker equation would give little acceleration. Acceleration at reconnection therefore must go beyond the Parker equation - either by invoking large pitch-angle anisotropies or by extending the equation to higher order in the flow speed relative to the particle speed. An approach to using an extension of Parker's equation is discussed. Diffusive shock acceleration at the heliospheric termination shock is also discussed. It is suggested that inclusion of upstream turbulence and shock geometry provides reasonable solutions to the perceived problems with this mechanism. Finally, observation evidence is presented which suggests, strongly, that the acceleration of the ACR occurs in the inner heliosphere, not far from the heliospheric termination shock.

Jokipii, J. R.

2012-05-01

309

Injector and beam transport simulation study of proton dielectric wall accelerator  

NASA Astrophysics Data System (ADS)

A simulation study of a short-pulsed proton injector for, and beam transport in, a dielectric wall accelerator (DWA) has been carried out using the particle-in-cell (PIC) code Warp. It was shown that applying "tilt pulse" voltage waveforms on three electrodes enables the production of a shorter bunch by the injector. The fields in the DWA beam tube were simulated using Computer Simulation Technology's Microwave Studio (CST MWS) package, with various choices for the boundary conditions. For acceleration in the DWA, the beam transport was simulated with Warp, using applied fields obtained by running CST MWS. Our simulations showed that the electric field at the entrance to the DWA represents a challenging issue for the beam transport. We thus simulated a configuration with a mesh at the entrance of the DWA, intended to improve the entrance field. In these latter simulations, a proton bunch was successfully accelerated from 130 keV to about 36 MeV in a DWA with a length of 36.75 cm. As the beam bunch progresses, its transverse dimensions diminish from (roughly) 0.5×0.5 cm to 0.2×0.4 cm. The beam pulse lengthens from 1 cm to 2 cm due to lack of longitudinal compression fields.

Zhao, Quantang; Yuan, P.; Zhang, Z. M.; Cao, S. C.; Shen, X. K.; Jing, Y.; Ma, Y. Y.; Yu, C. S.; Li, Z. P.; Liu, M.; Xiao, R. Q.; Zhao, H. W.

2012-12-01

310

Accelerating particles in general relativity (stationary C-metric)  

Microsoft Academic Search

The physical and geometrical properties of uniformly accelerating particles in the general theory of relativity are examined. The structure of the Killing horizons in the static vacuum C-metric which represents the gravitational field of a uniformly accelerating Schwarzschild like particle (nonrotating and spherically symmetric) is studied. It is shown that for A(2)m(2) 1\\/27 there exist two physically meaningful Killing horizons.

H. Farhoosh

1979-01-01

311

Acceleration and Trapping of Particles by Radiation Pressure  

Microsoft Academic Search

Micron-sized particles have been accelerated and trapped in stable optical potential wells using only the force of radiation pressure from a continuous laser. It is hypothesized that similar accelerations and trapping are possible with atoms and molecules using laser light tuned to specific optical transitions. The implications for isotope separation and other applications of physical interest are discussed.

A. Ashkin

1970-01-01

312

The phase of particle acceleration in the flare development  

Microsoft Academic Search

Evidence is given that the particle acceleration in flares is confined to the initial phase of the flare development preceding the Ha flare maximum and lasting for less than 10 min. The impulsive acceleration process is confined to a relatively small limited volume of about 5 × 1027 cm3 in the region of highest magnetic gradient in the flare, and

Z. Švestka

1970-01-01

313

Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil  

SciTech Connect

By using multidimensional particle-in-cell simulations, we present a new regime of stable proton beam acceleration which takes place when a two-ion-species shaped foil is illuminated by a circularly polarized laser pulse. In the simulations, the lighter protons are nearly instantaneously separated from the heavier carbon ions due to the charge-to-mass ratio difference. The heavy ion layer expands in space and acts to buffer the proton layer from the Rayleigh-Taylor-like (RT) instability that would have otherwise degraded the proton beam acceleration. A simple three-interface model is formulated to explain qualitatively the stable acceleration of the light ions. In the absence of the RT instability, the high quality monoenergetic proton bunch persists even after the laser-foil interaction ends.

Yu, Tong-Pu [Institut fuer Theoretische Physik I, Heinrich-Heine-Universitaet Duesseldorf, 40225 Duesseldorf (Germany); Department of Physics, National University of Defense Technology, Changsha 410073 (China); Pukhov, Alexander [Institut fuer Theoretische Physik I, Heinrich-Heine-Universitaet Duesseldorf, 40225 Duesseldorf (Germany); Shvets, Gennady [Univ Texas Austin, Dept Phys, Austin, Texas 78712 (United States); Univ Texas Austin, Inst Fus Studies, Austin, Texas 78712 (United States); Chen, Min [Institut fuer Theoretische Physik I, Heinrich-Heine-Universitaet Duesseldorf, 40225 Duesseldorf (Germany); Accelerator Fusion Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-08-06

314

Electron acceleration to energies beyond GeV by a relativistic ion beam instability.  

PubMed

Synchrotron emission suggests the presence of TeV electrons at various astrophysical objects. We propose a mechanism for the acceleration of electrons to ultrahigh energies (UHE) by intense electrostatic waves (ESWs). The latter are driven by dense proton beams that move at relativistic speeds relative to a background plasma and the electrons are accelerated by their nonlinear interaction with the ESWs. We follow the evolution of the wave instability by means of particle-in-cell (PIC) simulations. After the instability has saturated, we obtain spatially confined electron voids in which secondary instabilities develop due to resonant interactions between the beams and the background protons, generating intense ESWs which accelerate electrons to ultrarelativistic speeds within times of a few hundred inverse plasma frequencies. PMID:15524640

Dieckmann, M E; Eliasson, B; Shukla, P K

2004-09-01

315

Interactions of Airy beams, nonlinear accelerating beams, and induced solitons in Kerr and saturable nonlinear media.  

PubMed

We investigate numerically interactions between two in-phase or out-of-phase Airy beams and nonlinear accelerating beams in Kerr and saturable nonlinear media in one transverse dimension. We discuss different cases in which the beams with different intensities are launched into the medium, but accelerate in opposite directions. Since both the Airy beams and nonlinear accelerating beams possess infinite oscillating tails, we discuss interactions between truncated beams, with finite energies. During interactions we see solitons and soliton pairs generated that are not accelerating. In general, the higher the intensities of interacting beams, the easier to form solitons; when the intensities are small enough, no solitons are generated. Upon adjusting the interval between the launched beams, their interaction exhibits different properties. If the interval is large relative to the width of the first lobes, the generated soliton pairs just propagate individually and do not interact much. However, if the interval is comparable to the widths of the maximum lobes, the pairs strongly interact and display varied behavior. PMID:24664064

Zhang, Yiqi; Beli?, Milivoj R; Zheng, Huaibin; Chen, Haixia; Li, Changbiao; Li, Yuanyuan; Zhang, Yanpeng

2014-03-24

316

STOCHASTIC PARTICLE ACCELERATION AND THE PROBLEM OF BACKGROUND PLASMA OVERHEATING  

SciTech Connect

The origin of hard X-ray (HXR) excess emission from clusters of galaxies is still an enigma, whose nature is debated. One of the possible mechanisms to produce this emission is the bremsstrahlung model. However, previous analytical and numerical calculations showed that in this case the intracluster plasma had to be overheated very fast because suprathermal electrons emitting the HXR excess lose their energy mainly by Coulomb losses, i.e., they heat the background plasma. It was concluded also from these investigations that it is problematic to produce emitting electrons from a background plasma by stochastic (Fermi) acceleration because the energy supplied by external sources in the form of Fermi acceleration is quickly absorbed by the background plasma. In other words, the Fermi acceleration is ineffective for particle acceleration. We revisited this problem and found that at some parameter of acceleration the rate of plasma heating is rather low and the acceleration tails of nonthermal particles can be generated and exist for a long time while the plasma temperature is almost constant. We showed also that for some regime of acceleration the plasma cools down instead of being heated up, even though external sources (in the form of external acceleration) supply energy to the system. The reason is that the acceleration withdraws effectively high-energy particles from the thermal pool (analog of Maxwell demon).

Chernyshov, D. O.; Dogiel, V. A. [I. E. Tamm Theoretical Physics Division of P. N. Lebedev Institute, Leninskii pr 53, 119991 Moscow (Russian Federation); Ko, C. M., E-mail: cmko@astro.ncu.edu.tw [Institute of Astronomy, National Central University, JhongLi 320, Taiwan (China)

2012-11-10

317

LATTICES FOR HIGH-POWER PROTON BEAM ACCELERATION AND SECONDARY BEAM COLLECTION AND COOLING.  

SciTech Connect

Rapid cycling synchrotrons are used to accelerate high-intensity proton beams to energies of tens of GeV for secondary beam production. After primary beam collision with a target, the secondary beam can be collected, cooled, accelerated or decelerated by ancillary synchrotrons for various applications. In this paper, we first present a lattice for the main synchrotron. This lattice has: (a) flexible momentum compaction to avoid transition and to facilitate RF gymnastics (b) long straight sections for low-loss injection, extraction, and high-efficiency collimation (c) dispersion-free straights to avoid longitudinal-transverse coupling, and (d) momentum cleaning at locations of large dispersion with missing dipoles. Then, we present a lattice for a cooler ring for the secondary beam. The momentum compaction across half of this ring is near zero, while for the other half it is normal. Thus, bad mixing is minimized while good mixing is maintained for stochastic beam cooling.

WANG, S.; WEI, J.; BROWN, K.; GARDNER, C.; LEE, Y.Y.; LOWENSTEIN, D.; PEGGS, S.; SIMOS, N.

2006-06-23

318

Crystal-Assisted Beam Extraction and Collimation at the U-70 Circular Accelerator  

E-print Network

New crystal technique - array of bent strips and a fan-type reflector, based on thin straight plates - have been used for research of extraction and collimation a circulating beam in the U-70 accelerator at the energy 50 GeV and 1.3 GeV. It is shown, that new devices can effectively steer a beam in a wide energy range. For protons with energy 50 GeV efficiency of extraction and collimation about 90 % has been achieved which is record for this method. Reduction of particle losses in 2-3 times was observed also in accelerator at application of different crystals in comparison with the usual one-stage collimation scheme of beam with a steel absorber.

Afonin, A G; Bellucci, S; Belov, S A; Bini, S; Gorlov, V N; Giannini, G; Ermolaev, A D; Ivanova, I V; Krylov, D M; Maisheev, V A; Savin, D A; Syshchikov, E A; Terekhov, V I; Chepegin, V N; Chesnokov, Yu A; Chirkov, P N; Yazynin, I A

2011-01-01

319

An improved 8 GeV beam transport system for the Fermi National Accelerator Laboratory  

SciTech Connect

A new 8 GeV beam transport system between the Booster and Main Ring synchrotrons at the Fermi National Accelerator Laboratory is presented. The system was developed in an effort to improve the transverse phase space area occupied by the proton beam upon injection into the Main Ring accelerator. Problems with the original system are described and general methods of beamline design are formulated. Errors in the transverse properties of a beamline at the injection point of the second synchrotron and their effects on the region in transverse phase space occupied by a beam of particles are discussed. Results from the commissioning phase of the project are presented as well as measurements of the degree of phase space dilution generated by the transfer of 8 GeV protons from the Booster synchrotron to the Main Ring synchrotron.

Syphers, M.J.

1987-06-01

320

Observation of laser multiple filamentation process and multiple electron beams acceleration in a laser wakefield accelerator  

SciTech Connect

The multiple filaments formation process in the laser wakefield accelerator (LWFA) was observed by imaging the transmitted laser beam after propagating in the plasma of different density. During propagation, the laser first self-focused into a single filament. After that, it began to defocus with energy spreading in the transverse direction. Two filaments then formed from it and began to propagate independently, moving away from each other. We have also demonstrated that the laser multiple filamentation would lead to the multiple electron beams acceleration in the LWFA via ionization-induced injection scheme. Besides, its influences on the accelerated electron beams were also analyzed both in the single-stage LWFA and cascaded LWFA.

Li, Wentao; Liu, Jiansheng; Wang, Wentao; Chen, Qiang; Zhang, Hui; Tian, Ye; Zhang, Zhijun; Qi, Rong; Wang, Cheng; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)] [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2013-11-15

321

Focused transport of intense charged particle beams. Final technical report FY/93  

SciTech Connect

Many recent developments in accelerator technology have increased the need for a better understanding of the physics of intense-beam transport. Of particular interest to the work described here is the appearance, as beam intensities are increased, of a class of nonlinear phenomena which involve the collective interaction of the beam particles. Beam intensity, used as a measure of the importance of space-charge collective behavior, depends on the ratio of current to emittance. The nonlinear beam dynamics, and any resulting emittance growth, which are characteristic of the intense-beam regime, can therefore occur even at low currents in any accelerator system with sufficiently high intensity, especially in the low beta section. Furthermore, since emittance of a beam is difficult to reduce, the ultimate achievement of necessary beam luminosities requires the consideration of possible causes of longitudinal and transverse emittance growth at every stage of the beam lifetime. The research program described here has addressed the fundamental physics which comes into play during the transport, acceleration and focusing of intense beams. Because of the long term and ongoing nature of the research program discussed here, this report is divided into two sections. The first section constitutes a long term revue of the accomplishments which have resulted from the research effort reported, especially in pioneering the use of particle-in-cell (PIC) computer simulation techniques for simulation of the dynamics of space-charge-dominated beams in particle accelerators. The following section emphasizes, in more detail, the accomplishments of the FY 92/93 period immediately prior to the termination of this particular avenue of support. 41 refs.

NONE

1997-06-01

322

Particle trajectories and acceleration during 3D fan reconnection  

E-print Network

Context. The primary energy release in solar flares is almost certainly due to magnetic reconnection, making this a strong candidate as a mechanism for particle acceleration. While particle acceleration in 2D geometries has been widely studied, investigations in 3D are a recent development. Two main classes of reconnection regimes at a 3D magnetic null point have been identified: fan and spine reconnection Aims. Here we investigate particle trajectories and acceleration during reconnection at a 3D null point, using a test particle numerical code, and compare the efficiency of the fan and spine regimes in generating an energetic particle population. Methods. We calculated the time evolution of the energy spectra. We discuss the geometry of particle escape from the two configurations and characterise the trapped and escaped populations. Results. We find that fan reconnection is less efficent than spine reconnection in providing seed particles to the region of strong electric field where acceleration is possible. The establishment of a steady-state spectrum requires approximately double the time in fan reconnection. The steady-state energy spectrum at intermediate energies (protons 1 keV to 0.1 MeV) is comparable in the fan and spine regimes. While in spine reconnection particle escape takes place in two symmetric jets along the spine, in fan reconnection no jets are produced and particles escape in the fan plane, in a ribbon-like structure.

S. Dalla; P. K. Browning

2008-11-07

323

Beam by design: Laser manipulation of electrons in modern accelerators  

NASA Astrophysics Data System (ADS)

Accelerator-based light sources such as storage rings and free-electron lasers use relativistic electron beams to produce intense radiation over a wide spectral range for fundamental research in physics, chemistry, materials science, biology, and medicine. More than a dozen such sources operate worldwide, and new sources are being built to deliver radiation that meets with the ever-increasing sophistication and depth of new research. Even so, conventional accelerator techniques often cannot keep pace with new demands and, thus, new approaches continue to emerge. In this article, a variety of recently developed and promising techniques that rely on lasers to manipulate and rearrange the electron distribution in order to tailor the properties of the radiation are reviewed. Basic theories of electron-laser interactions, techniques to create microstructures and nanostructures in electron beams, and techniques to produce radiation with customizable waveforms are reviewed. An overview of laser-based techniques for the generation of fully coherent x rays, mode-locked x-ray pulse trains, light with orbital angular momentum, and attosecond or even zeptosecond long coherent pulses in free-electron lasers is presented. Several methods to generate femtosecond pulses in storage rings are also discussed. Additionally, various schemes designed to enhance the performance of light sources through precision beam preparation including beam conditioning, laser heating, emittance exchange, and various laser-based diagnostics are described. Together these techniques represent a new emerging concept of "beam by design" in modern accelerators, which is the primary focus of this article.

Hemsing, Erik; Stupakov, Gennady; Xiang, Dao; Zholents, Alexander

2014-07-01

324

Vacuum chamber for containing particle beams  

DOEpatents

A vacuum chamber for containing a charged particle beam in a rapidly changing magnetic environment comprises a ceramic pipe with conducting strips oriented along the longitudinal axis of the pipe and with circumferential conducting bands oriented perpendicular to the longitudinal axis but joined with a single longitudinal electrical connection. When both strips and bands are on the outside of the ceramic pipe, insulated from each other, a high-resistance conductive layer, such as nickel can be coated on the inside of the pipe.

Harvey, Alexander (Los Alamos, NM)

1987-01-01

325

Charged particle beam current monitoring tutorial  

SciTech Connect

A tutorial presentation is made on topics related to the measurement of charged particle beam currents. The fundamental physics of electricity and magnetism pertinent to the problem is reviewed. The physics is presented with a stress on its interpretation from an electrical circuit theory point of view. The operation of devices including video pulse current transformers, direct current transformers, and gigahertz bandwidth wall current style transformers is described. Design examples are given for each of these types of devices. Sensitivity, frequency response, and physical environment are typical parameters which influence the design of these instruments in any particular application. Practical engineering considerations, potential pitfalls, and performance limitations are discussed.

Webber, R.C.

1994-10-01

326

Extraction of the Proton Beam from the 70 GeV IHEP Accelerator  

E-print Network

This paper presents the physical background for particle extraction from IHEP accelerator using short bent silicon crystals, analyses the results of the studies, considers in detail the regime of simultaneous work of crystal extraction and several internal targets. It is experimentally shown that the use of short crystals allows the extraction of beams with intensity of 10e12 proton/cycle with efficiency of 85%.

Afonin, A G; Biryukov, V M; Ivanov, I M; Kardash, A A; Kotov, V I; Maisheev, V A; Terekhov, V I; Troyanov, E F; Fedotov, Y S; Chepegin, V N; Chesnokov, Yu A; Fedotov, Yu.S.; Chesnokov, Yu.A.

2005-01-01

327

GPU-accelerated automatic identification of robust beam setups for proton and carbon-ion radiotherapy  

NASA Astrophysics Data System (ADS)

We demonstrate acceleration on graphic processing units (GPU) of automatic identification of robust particle therapy beam setups, minimizing negative dosimetric effects of Bragg peak displacement caused by treatment-time patient positioning errors. Our particle therapy research toolkit, RobuR, was extended with OpenCL support and used to implement calculation on GPU of the Port Homogeneity Index, a metric scoring irradiation port robustness through analysis of tissue density patterns prior to dose optimization and computation. Results were benchmarked against an independent native CPU implementation. Numerical results were in agreement between the GPU implementation and native CPU implementation. For 10 skull base cases, the GPU-accelerated implementation was employed to select beam setups for proton and carbon ion treatment plans, which proved to be dosimetrically robust, when recomputed in presence of various simulated positioning errors. From the point of view of performance, average running time on the GPU decreased by at least one order of magnitude compared to the CPU, rendering the GPU-accelerated analysis a feasible step in a clinical treatment planning interactive session. In conclusion, selection of robust particle therapy beam setups can be effectively accelerated on a GPU and become an unintrusive part of the particle therapy treatment planning workflow. Additionally, the speed gain opens new usage scenarios, like interactive analysis manipulation (e.g. constraining of some setup) and re-execution. Finally, through OpenCL portable parallelism, the new implementation is suitable also for CPU-only use, taking advantage of multiple cores, and can potentially exploit types of accelerators other than GPUs.

Ammazzalorso, F.; Bednarz, T.; Jelen, U.

2014-03-01

328

Beam dynamics design for uranium drift tube linear accelerator  

NASA Astrophysics Data System (ADS)

KONUS beam dynamics design of uranium DTL with LORASR code is presented. The 238U34+ beam, whose current is 5.0 emA, is accelerated from injection energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operated at 81.25 MHz in HIAF project at IMP of CAS. It achieves a transmission efficiency of 94.95% with a cavity length of 267.8 cm. The optimization aims are the reduction of emittance growth, beam loss and project costs. Because of the requirements of CW mode operation, the designed average acceleration gradient is about 2.48 MV/m. The maximum axial field is 10.2 MV/m, meanwhile the Kilpatrick breakdown field is 10.56 MV/m at 81.25 MHz.

Dou, Wei-Ping; He, Yuan; Lu, Yuan-Rong

2014-07-01

329

Potential mapping with charged-particle beams  

NASA Technical Reports Server (NTRS)

Experimental methods of mapping the equipotential surfaces near some structure of interest rely on the detection of charged particles which have traversed the regions of interest and are detected remotely. One method is the measurement of ion energies for ions created at a point of interest and expelled from the region by the fields. The ion energy at the detector in eV corresponds to the potential where the ion was created. An ionizing beam forms the ions from background neutrals. The other method is to inject charged particles into the region of interest and to locate their exit points. A set of several trajectories becomes a data base for a systematic mapping technique. An iterative solution of a boundary value problem establishes concepts and limitations pertaining to the mapping problem.

Robinson, J. W.; Tillery, D. G.

1979-01-01

330

Solar particles /observations, relationship to the sun acceleration, interplanetary medium/  

NASA Technical Reports Server (NTRS)

The major features of the propagation of flare particles in the interplanetary medium are discussed in terms of the classic well-behaved flare having unique impulsive injection and a smooth time profile. Topics include flare events, their frequency of occurrence, development of a typical event, energy spectra, proton and electron types, charge and isotopic composition, solar flares and particle accelerations, radio and X-ray observations, the Fermi mechanism, the betatron mechanism, acceleration models, plasma instabilities, two-stage acceleration, propagation mechanisms, the anisotropic stage, the diffusive stage, and the convection and energy loss stage.

Mcdonald, F. B.; Fichtel, C. E.; Fisk, L. A.

1974-01-01

331

Improved Purification and Dissolution Properties of Carbon Nanotubes by Irradiation of Accelerated Particles.  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) have recently attracted much interest for their exceptional chemical and physical properties and unique aspect ratio. Yet, CNTs applications have been somewhat limited due to their retained impurities and limited solubility in most organic solvents. In this work, we study the feasibility of using accelerated particles (electrons and protons) to covalently modify CNT surface. Results show that accelerated proton radiation with a energy of 10 MeV, both in an ambient atmospheric condition, can generate oxygen-rich functional groups, e.g. carboxylic acid and phenol, on CNTs surfaces and significantly improve their solubility without any significant surface damage. On the other hand, accelerated electron beam induced effective removal of SP^3 carbon bonding, resulting that physical welding of crossed carbon nanotubes. This work is supported by the Proton Accelerator (No. M202AK010021-04A1101-02110) and Accelerated Electron User Program from the Nuclear R&D Program.

Najafi, Ebrahim

2005-03-01

332

SINGLE BUNCH TRANSIENT DETECTION FOR THE BEAM PHASE MEASUREMENT IN SUPERCONDUCTING ACCELERATORS  

Microsoft Academic Search

During commissioning and operation of linear accelerators the beam phase must be determined with respect to the accelerating rf fields. It is desirable to perform these measurements at low beam current and with a short beam pulse duration to avoid unnecessary beam loss during start-up when the correct beam phase is not guaranteed. In the case of the European X-FEL

P. Pawlik; M. Grecki

333

Current and future uses of accelerators in particle astrophysics  

NASA Technical Reports Server (NTRS)

Beams of artificially accelerated heavy ions, protons, antiprotons, electrons, and positrons currently available at (and planned for) numerous facilities around the world are a valuable resource to the Cosmic Ray community. Such beams have been used to test detector concepts, calibrate balloon-borne and space flight experiments and to measure fundamental nuclear physics parameter necessary for the interpretation of Cosmic Ray data. As new experiments are flown the quality and extent of Cosmic Ray measurements will continue to improve. It will be necessary to increase activity at ground based accelerators in order to test/calibrate these new instruments and to maintain (or possibly improve) the ability to interpret these data. In this area, the newly formed Transport Collaboration, supported by NASA, will be providing new nuclear interaction cross section measurements for beams with Z less than or = 58 and supporting new instrument calibrations at the Lawrence Berkeley Laboratory Bevalac accelerator.

Guzik, T. G.

1990-01-01

334

Particle Acceleration in Pair-Starved Pulsars  

E-print Network

We investigate the physical situation above the pulsar polar cap (PC) where the accelerating primaries (electrons) are not capable of producing sufficient numbers of electron-positron pairs at low altitudes (within 1-2 stellar radii above the PC surface) to screen the accelerating electric field, and continue accelerating up to, at least, very high altitudes nearly approaching the light cylinder. We derive an analytic solution for the parallel electric field valid at high altitudes. The solution is based on the physical condition of asymptotic vanishing of the rotationally induced transverse electric field within the magnetic flux tube. This condition constrains the asymptotic value of the effective space charge that determines the distribution of the parallel electric field within the magnetic tube. Our estimates of low- to high-altitude values of the parallel electric field imply the occurrence of a regime of primary acceleration (with the characteristic Lorentz factor up to 1-2 X 10^7) all the way from the PC to the light cylinder limited by curvature-radiation reaction. In this model the primary outflow becomes asymptotically force-free, and may turn into a relativistic wind beyond the light cylinder. Such a solution will apply to both older pulsars producing only inverse Compton scattering pairs and younger very high B pulsars (magnetars). We suggest that pulsars, which are lying below the pair death line, may be radio-quiet gamma-ray sources.

Alex G. Muslimov; Alice K. Harding

2004-08-20

335

Self-consistent radiative effect on relativistic electromagnetic particle acceleration  

E-print Network

We study the radiation damping effect on the relativistic acceleration of electron-positron plasmas with two-and-half-dimensional particle-in-cell (PIC) simulation. Particles are accelerated by Poynting flux via the diamagnetic relativistic pulse accelerator (DRPA), and decelerated by the self-consistently solved radiation damping force. With $\\Omega_{ce}/\\omega_{pe}\\geq 10$, the Lorentz factor of the highest energy particles reaches gamma>100, and the acceleration still continues. The emitted radiation is peaked within few degrees from the direction of Poynting flux and strongly linearly polarized, which may be detectable in gamma-ray burst(GRB) observations. We also show that the DRPA is insensitive to the initial supporting currents.

K. Noguchi; E. Liang; K. Nishimura

2005-04-27

336

Turbulence Evolution and Shock Acceleration of Solar Energetic Particles  

NASA Technical Reports Server (NTRS)

We model the effects of self-excitation/damping and shock transmission of Alfven waves on solar-energetic-particle (SEP) acceleration at a coronal-mass-ejection (CME) driven parallel shock. SEP-excited outward upstream waves speedily bootstrap acceleration. Shock transmission further raises the SEP-excited wave intensities at high wavenumbers but lowers them at low wavenumbers through wavenumber shift. Downstream, SEP excitation of inward waves and damping of outward waves tend to slow acceleration. Nevertheless, > 2000 km/s parallel shocks at approx. 3.5 solar radii can accelerate SEPs to 100 MeV in < 5 minutes.

Chee, Ng K.

2007-01-01

337

Particle Acceleration Asymmetry in a Reconnecting Nonneutral Current Sheet  

Microsoft Academic Search

The acceleration of electrons and protons caused by a super-Dreicer electric field directed along the longitudinal component By of the magnetic field is investigated. The three-component magnetic field in a nonneutral current sheet occurring at the top of the reconnecting flaring loops on the charged particle trajectories and energies is considered. Particle trajectories in the reconnecting current sheet (RCS) and

Valentina V. Zharkova; Mykola Gordovskyy

2004-01-01

338

Magnetic reconnection configurations and particle acceleration in solar flares  

E-print Network

types of solar flares. Upper panel: two-ribbon flares; Lower panel: compact flares. The color showsMagnetic reconnection configurations and particle acceleration in solar flares P. F. Chen, W. J space under different magnetic configurations. Key words: solar flares, magnetic reconnection, particle

Chen, P. F.

339

Particle Acceleration by Fast Modes in Solar Flares  

E-print Network

We address the problem of particle acceleration in solar flares by fast modes which may be excited during the reconnection and undergo cascade and are subjected to damping. We extend the calculations beyond quasilinear approximation and compare the acceleration and scattering by transit time damping and gyroresonance interactions. We find that the acceleration is dominated by the so called transit time damping mechanism. We estimate the total energy transferred into particles, and show that our approach provides sufficiently accurate results We compare this rate with energy loss rate. Scattering by fast modes appears to be sufficient to prevent the protons from escaping the system during the acceleration. Confinement of electrons, on the other hand, requires the existence of plasma waves. Electrons can be accelerated to GeV energies through the process described here for solar flare conditions.

Huirong Yan; A. Lazarian; V. Petrosian

2008-01-24

340

Solid-particle jet formation under shock-wave acceleration.  

PubMed

When solid particles are impulsively dispersed by a shock wave, they develop a spatial distribution which takes the form of particle jets whose selection mechanism is still unidentified. The aim of the present experimental work is to study particle dispersal with fingering effects in an original quasi-two-dimensional experiment facility in order to accurately extract information. Shock and blast waves are generated in the carrier gas at the center of a granular medium ring initially confined inside a Hele-Shaw cell and impulsively accelerated. With the present experimental setup, the particle jet formation is clearly observed. From fast flow visualizations, we notice, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point has not been observed in three-dimensional experiments. We highlight that the number of jets is unsteady and decreases with time. For a fixed configuration, considering the very early times following the initial acceleration, the jet size selection is independent of the particle diameter. Moreover, the influence of the initial overpressure and the material density on the particle jet formation have been studied. It is shown that the wave number of particle jets increases with the overpressure and with the decrease of the material density. The normalized number of jets as a function of the initial ring acceleration shows a power law valid for all studied configurations involving various initial pressure ratios, particle sizes, and particle materials. PMID:24483561

Rodriguez, V; Saurel, R; Jourdan, G; Houas, L

2013-12-01

341

Solid-particle jet formation under shock-wave acceleration  

NASA Astrophysics Data System (ADS)

When solid particles are impulsively dispersed by a shock wave, they develop a spatial distribution which takes the form of particle jets whose selection mechanism is still unidentified. The aim of the present experimental work is to study particle dispersal with fingering effects in an original quasi-two-dimensional experiment facility in order to accurately extract information. Shock and blast waves are generated in the carrier gas at the center of a granular medium ring initially confined inside a Hele-Shaw cell and impulsively accelerated. With the present experimental setup, the particle jet formation is clearly observed. From fast flow visualizations, we notice, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point has not been observed in three-dimensional experiments. We highlight that the number of jets is unsteady and decreases with time. For a fixed configuration, considering the very early times following the initial acceleration, the jet size selection is independent of the particle diameter. Moreover, the influence of the initial overpressure and the material density on the particle jet formation have been studied. It is shown that the wave number of particle jets increases with the overpressure and with the decrease of the material density. The normalized number of jets as a function of the initial ring acceleration shows a power law valid for all studied configurations involving various initial pressure ratios, particle sizes, and particle materials.

Rodriguez, V.; Saurel, R.; Jourdan, G.; Houas, L.

2013-12-01

342

Fluid particle accelerations in fully developed turbulence  

Microsoft Academic Search

The motion of fluid particles as they are pushed along erratic trajectories\\u000aby fluctuating pressure gradients is fundamental to transport and mixing in\\u000aturbulence. It is essential in cloud formation and atmospheric transport,\\u000aprocesses in stirred chemical reactors and combustion systems, and in the\\u000aindustrial production of nanoparticles. The perspective of particle\\u000atrajectories has been used successfully to describe mixing

Greg A. Voth; Alice M. Crawford; Jim Alexander; Eberhard Bodenschatz; A. La Porta

2001-01-01

343

Monte Carlo simulation of particle acceleration at astrophysical shocks  

NASA Technical Reports Server (NTRS)

A Monte Carlo code was developed for the simulation of particle acceleration at astrophysical shocks. The code is implemented in Turbo Pascal on a PC. It is modularized and structured in such a way that modification and maintenance are relatively painless. Monte Carlo simulations of particle acceleration at shocks follow the trajectories of individual particles as they scatter repeatedly across the shock front, gaining energy with each crossing. The particles are assumed to scatter from magnetohydrodynamic (MHD) turbulence on both sides of the shock. A scattering law is used which is related to the assumed form of the turbulence, and the particle and shock parameters. High energy cosmic ray spectra derived from Monte Carlo simulations have observed power law behavior just as the spectra derived from analytic calculations based on a diffusion equation. This high energy behavior is not sensitive to the scattering law used. In contrast with Monte Carlo calculations diffusive calculations rely on the initial injection of supra-thermal particles into the shock environment. Monte Carlo simulations are the only known way to describe the extraction of particles directly from the thermal pool. This was the triumph of the Monte Carlo approach. The question of acceleration efficiency is an important one in the shock acceleration game. The efficiency of shock waves efficient to account for the observed flux of high energy galactic cosmic rays was examined. The efficiency of the acceleration process depends on the thermal particle pick-up and hence the low energy scattering in detail. One of the goals is the self-consistent derivation of the accelerated particle spectra and the MHD turbulence spectra. Presumably the upstream turbulence, which scatters the particles so they can be accelerated, is excited by the streaming accelerated particles and the needed downstream turbulence is convected from the upstream region. The present code is to be modified to include a better description of particle scattering (pitch-angle instead of hard-sphere) and as iterative procedure for treating the self-excitation of the MHD turbulence.

Campbell, Roy K.

1989-01-01

344

Monte Carlo simulation of particle acceleration at astrophysical shocks  

NASA Astrophysics Data System (ADS)

A Monte Carlo code was developed for the simulation of particle acceleration at astrophysical shocks. The code is implemented in Turbo Pascal on a PC. It is modularized and structured in such a way that modification and maintenance are relatively painless. Monte Carlo simulations of particle acceleration at shocks follow the trajectories of individual particles as they scatter repeatedly across the shock front, gaining energy with each crossing. The particles are assumed to scatter from magnetohydrodynamic (MHD) turbulence on both sides of the shock. A scattering law is used which is related to the assumed form of the turbulence, and the particle and shock parameters. High energy cosmic ray spectra derived from Monte Carlo simulations have observed power law behavior just as the spectra derived from analytic calculations based on a diffusion equation. This high energy behavior is not sensitive to the scattering law used. In contrast with Monte Carlo calculations diffusive calculations rely on the initial injection of supra-thermal particles into the shock environment. Monte Carlo simulations are the only known way to describe the extraction of particles directly from the thermal pool. This was the triumph of the Monte Carlo approach. The question of acceleration efficiency is an important one in the shock acceleration game. The efficiency of shock waves efficient to account for the observed flux of high energy galactic cosmic rays was examined. The efficiency of the acceleration process depends on the thermal particle pick-up and hence the low energy scattering in detail. One of the goals is the self-consistent derivation of the accelerated particle spectra and the MHD turbulence spectra. Presumably the upstream turbulence, which scatters the particles so they can be accelerated, is excited by the streaming accelerated particles and the needed downstream turbulence is convected from the upstream region. The present code is to be modified to include a better description of particle scattering (pitch-angle instead of hard-sphere) and as iterative procedure for treating the self-excitation of the MHD turbulence.

Campbell, Roy K.

1989-09-01

345

Radiative Effects on Particle Acceleration in Electromagnetic Dominated Outflows  

E-print Network

Plasma outflows from gamma-ray bursts (GRB), pulsar winds, relativistic jets, and ultra-intense laser targets radiate high energy photons. However, radiation damping is ignored in conventional PIC simulations. In this letter, we study the radiation damping effect on particle acceleration via Poynting fluxes in two-and-half-dimensional particle-in-cell (PIC) plasma simulation of electron-positron plasmas. Radiation damping force is self-consistently calculated for each particle and reduces the net acceleration force. The emitted radiation is peaked within a few degrees from the direction of Poynting flux and strongly linear-polarized.

Koichi Noguchi; Edison Liang; Kazumi Nishimura

2004-12-14

346

First order particle acceleration in magnetically-driven flows  

E-print Network

We demonstrate that particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. Some examples of such flows include spontaneous turbulent reconnection and decaying magnetohydrodynamic (MHD) turbulence, where magnetic field relaxes to a lower-energy configuration and transfers part of its energy to kinetic motions. The opposite process, such as dynamo, will actually result in the net cooling of particles by the curvature drift. Being very generic, this acceleration mechanism is likely to be responsible in production of non-thermal particle distribution in magnetically-dominant environments such as solar chromosphere, pulsar magnetosphere, jets from supermassive black holes, $\\gamma$-ray bursts, etc.

Beresnyak, Andrey

2014-01-01

347

Collisionless Shocks -- Magnetic Field Generation and Particle Acceleration  

E-print Network

We present numerical results from plasma particle simulations of collisionless shocks and ultra-relativistic counter-streaming plasmas. We demonstrate how the field-particle interactions lead to particle acceleration behind the shock-front. Further, we demonstrate how ultra relativistic counter-streaming plasmas create large scale patchy magnetic field structures and that these field structures propagate down-stream of the shock front. These results may help explain the origin of the magnetic fields and accelerated electrons responsible for afterglow synchrotron radiation from gamma ray bursts.

J. Trier Frederiksen; C. B. Hededal; T. Haugboelle; A. Nordlund

2003-03-16

348

Electron beam ion sources for use in second generation synchrotrons for medical particle therapya)  

NASA Astrophysics Data System (ADS)

Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C4 + and C6 + ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, "A survey of Hadron therapy accelerator technology," in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., "Cyclinac medical accelerators using pulsed C6 +/H+_2 ion sources," in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 109 protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA.

Zschornack, G.; Ritter, E.; Schmidt, M.; Schwan, A.

2014-02-01

349

Electron beam ion sources for use in second generation synchrotrons for medical particle therapy.  

PubMed

Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C(4 +) and C(6 +) ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, "A survey of Hadron therapy accelerator technology," in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., "Cyclinac medical accelerators using pulsed C(6 +)/H2(+) ion sources," in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 10(9) protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA. PMID:24593601

Zschornack, G; Ritter, E; Schmidt, M; Schwan, A

2014-02-01

350

Laser-driven shock acceleration of monoenergetic ion beams  

NASA Astrophysics Data System (ADS)

Ion acceleration from laser-plasma interactions is a promising approach for compact and bright ion sources. However, the conditions for optimization of the beam quality and energy are not yet fully understood. We show that the use of tailored critical-density targets, with a steep density ramp at the front and an exponential ramp at the back, which can be obtained in realistic experimental conditions, enables the generation of high quality and high energy ion beams accelerated by a laser-driven electrostatic shock. The laser deposits most of its energy in a localized region at critical density, heating the electrons and generating an electrostatic shock. The shock can then reflect most of the ions from the back of the target to high energies before competing accelerating fields (like TNSA) develop significantly, leading to high quality beams. Our PIC simulation results illustrate the possibility of generating high quality proton beams with energies in the required range for medical applications (100-300 MeV) with moderate laser intensities (a0 ˜ 10).

Boella, Elisabetta; Fiuza, Frederico; Fonseca, Ricardo A.; Silva, Luis O.; Haberberger, Dan; Tochitsky, Sergei; Gong, Chao; Mori, Warren B.; Joshi, Chan

2011-11-01

351

Modeling the Solar Atmospheric Response to Flare-Accelerated Ion Beams  

NASA Astrophysics Data System (ADS)

In the standard model of the impulsive phase of flares, particles accelerated to high energy at the flare reconnection site are the main source of heating in the lower atmosphere. These particles travel down magnetic flux tubes transferring their energy to the ambient plasma along the way through Coulomb collisions. It is likely that electrons as well as ions are accelerated by flare reconnection, and much work has been done understanding the response of the solar atmosphere to electron beam heating. However, since the presence of ions is much more difficult to directly detect than electrons, their role in flare heating is less understood. To better understand this, we have performed simulations of the solar atmospheric response to ion beam heating. Our models solve the equations of non-LTE radiation hydrodynamics for the conditions of the flaring solar atmosphere with an ion beam energy source term. Radiative transfer is solved in detail for many important optically thick hydrogen and helium transitions and numerous optically thin EUV lines. Thus, these models are ideally suited to study the emission that is produced during flares. We will pay special attention to understanding how key EUV lines respond to ion beam heating. We will compare these results to simulations performed with electron beam heating.

Allred, Joel C.; Holman, G. D.

2012-05-01

352

Tunneling of Dirac particles from accelerating and rotating black holes  

E-print Network

Hawking radiation from black holes has been studied as a phenomenon of quantum tunneling of particles through their horizons. We have extended this approach to study the tunneling of Dirac particles from a large class of black holes which includes those with acceleration and rotation as well. We have calculated the tunneling probability of incoming and outgoing particles, and recovered the correct Hawking temperature by this method.

Usman A. Gillani; K. Saifullah

2010-10-28

353

A PSO Accelerated Immune Particle Filter for Dynamic State Estimation  

Microsoft Academic Search

Particle Filter (PF) is a flexible and powerful Sequential Monte Carlo (SMC) technique to solve the nonlinear state\\/parameter estimation problems. The generic PF suffers due to degeneracy or sample impoverishment, which adversely affects its performance. In order to overcome this issue of the generic PF, a Particle Swarm Optimization accelerated Immune Particle Filter (PSO-acc-IPF) is proposed in this work. It

S. Akhtar; A. R. Ahmad; E. M. Abdel-Rahman; T. Naqvi

2011-01-01

354

UNDULATOR-BASED LASER WAKEFIELD ACCELERATOR ELECTRON BEAM DIAGNOSTIC  

SciTech Connect

to couple the THUNDER undulator to the LOASIS Lawrence Berkeley National Laboratory (LBNL) laser wakefield accelerator (LWFA). Currently the LWFA has achieved quasi-monoenergetic electron beams with energies up to 1 GeV. These ultra-short, high-peak-current, electron beams are ideal for driving a compact XUV free electron laser (FEL). Understanding the electron beam properties such as the energy spread and emittance is critical for achieving high quality light sources with high brightness. By using an insertion device such as an undulator and observing changes in the spontaneous emission spectrum, the electron beam energy spread and emittance can be measured with high precision. The initial experiments will use spontaneous emission from 1.5 m of undulator. Later experiments will use up to 5 m of undulator with a goal of a high gain, XUV FEL.

Bakeman, M.S.; Fawley, W.M.; Leemans, W. P.; Nakamura, K.; Robinson, K.E.; Schroeder, C.B.; Toth, C.

2009-05-04

355

PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS C. B. Schroeder, E. Esarey, C. Benedetti, Cs. Toth, C. G. R. Geddes, W. P. Leemans  

E-print Network

PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS C. B. Schroeder, E. Esarey, C. Benedetti, Cs. T´oth, C. G. R. Geddes, W. P. Leemans LBNL, Berkeley, CA 94720, USA Abstract Plasma accelerators may beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications

Geddes, Cameron Guy Robinson

356

Quasimonoenergetic electron beams from laser wakefield acceleration in pure nitrogen  

SciTech Connect

Quasimonoenergetic electron beams with maximum energy >0.5 GeV and 2 mrad divergence have been generated in pure nitrogen gas via wakefield acceleration with 80 TW, 30 fs laser pulses. Long low energy tail features were typically observed due to continuous ionization injection. The measured peak electron energy decreased with the plasma density, agreeing with the predicted scaling for electrons. The experiments showed a threshold electron density of 3x10{sup 18}cm{sup -3} for self-trapping. Our experiments suggest that pure Nitrogen is a potential candidate gas to achieve GeV monoenergetic electrons using the ionization induced injection scheme for laser wakefield acceleration.

Mo, M. Z.; Ali, A.; Fedosejevs, R. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Fourmaux, S.; Lassonde, P.; Kieffer, J. C. [INRS-EMT, Universite du Quebec, 1650 Lionel Boulet, Varennes, Quebec J3X 1S2 (Canada)

2012-02-13

357

Thermal equilibrium theory of periodically focused charged-particle beams  

E-print Network

A thermal equilibrium theory of periodically focused charged-particle beams is presented in the framework of both warm-fluid and kinetic descriptions. In particular, the thermal beam equilibria are discussed for paraxial ...

Samokhvalova, Ksenia R

2008-01-01

358

Modeling of Particle Acceleration at Multiple Shocks via Diffusive Shock Acceleration: Preliminary Results  

NASA Technical Reports Server (NTRS)

Successful forecasting of energetic particle events in space weather models require algorithms for correctly predicting the spectrum of ions accelerated from a background population of charged particles. We present preliminary results from a model that diffusively accelerates particles at multiple shocks. Our basic approach is related to box models in which a distribution of particles is diffusively accelerated inside the box while simultaneously experiencing decompression through adiabatic expansion and losses from the convection and diffusion of particles outside the box. We adiabatically decompress the accelerated particle distribution between each shock by either the method explored in Melrose and Pope (1993) and Pope and Melrose (1994) or by the approach set forth in Zank et al. (2000) where we solve the transport equation by a method analogous to operator splitting. The second method incorporates the additional loss terms of convection and diffusion and allows for the use of a variable time between shocks. We use a maximum injection energy (E(sub max)) appropriate for quasi-parallel and quasi-perpendicular shocks and provide a preliminary application of the diffusive acceleration of particles by multiple shocks with frequencies appropriate for solar maximum (i.e., a non-Markovian process).

Parker, L. Neergaard; Zank, G. P.

2013-01-01

359

Simon van der Meer and his legacy to CERN and particle accelerators  

E-print Network

Simon van der Meer was a brilliant scientist and a true giant in the field of accelerators. His seminal contributions to accelerator science are essential to this day in our quest to satisfy the demands of modern particle physics. Whether we are talking of long-baseline neutrino physics or antiproton-proton physics at CERN and Fermilab, or proton-proton physics at the LHC, his techniques and inventions have been a vital and necessary part of modern-day successes. Simon van der Meer and Carlo Rubbia were the first CERN scientists to become Nobel laureates in Physics in 1984. His less well-known contributions spanned a whole range of subjects in accelerator science from magnet design to power supply design, beam measurements, slow beam extraction, sophisticated programs, and controls.

Chohan, Vinod

2012-01-01

360

Particle Acceleration at the Sun and in the Heliosphere  

NASA Technical Reports Server (NTRS)

Energetic particles are accelerated in rich profusion at sites throughout the heliosphere. They come from solar flares in the low corona, from shock waves driven outward by coronal mass ejections (CMEs), from planetary magnetospheres and bow shocks. They come from corotating interaction regions (CIRs) produced by high-speed streams in the solar wind, and from the heliospheric termination shock at the outer edge of the heliospheric cavity. We sample all these populations near Earth, but can distinguish them readily by their element and isotope abundances, ionization states, energy spectra, angular distributions and time behavior. Remote spacecraft have probed the spatial distributions of the particles and examined new sources in situ. Most acceleration sources can be "seen" only by direct observation of the particles; few photons are produced at these sites. Wave-particle interactions are an essential feature in acceleration sources and, for shock acceleration, new evidence of energetic-proton-generated waves has come from abundance variations and from local cross-field scattering. Element abundances often tell us the physics the source plasma itself, prior to acceleration. By comparing different populations, we learn more about the sources, and about the physics of acceleration and transport, than we can possibly learn from one source alone.

Reames, Donald V.

1999-01-01

361

A particle-in-cell mode beam dynamics simulation of medium energy beam transport for the SSC-Linac  

NASA Astrophysics Data System (ADS)

A new linear accelerator system, called the SSC-Linac injector, is being designed at HIRFL (the heavy ion research facility of Lanzhou). As part of the SSC-Linac, the medium energy beam transport (MEBT) consists of seven magnetic quadrupoles, a re-buncher and a diagnose box. The total length of this segment is about 1.75 m. The beam dynamics simulation in MEBT has been studied using the TRACK 3D particle-in-cell code, and the simulation result shows that the beam accelerated from the radio frequency quadrupole (RFQ) matches well with the acceptance of the following drift tube linac (DTL) in both the transverse and longitudinal phase spaces, and that most of the particles can be captured by the final sector focusing cyclotron for further acceleration. The longitudinal emittance of the RFQ and the longitudinal acceptance of the DTL was calculated in detail, and a multi-particle beam dynamics simulation from the ion source to the end of the DTL was done to verify the original design.

Xiao, Chen; He, Yuan; Yuan, You-Jin; Lu, Yuan-Rong; Liu, Yong; Wang, Zhi-Jun; Du, Xiao-Nan; Yao, Qing-Gao; Liu, Ge; Xu, Meng-Xin; He, Shou-Bo; Xia, Jia-Wen

2012-01-01

362

Diffusive particle acceleration by an ensemble of shock waves  

NASA Astrophysics Data System (ADS)

The theory of diffusive acceleration of cosmic rays by shock waves (first order Fermi acceleration) is generalized to the case that the particles propagate through a medium in which many shocks are present simultaneously. The basic assumption underlying the theory presented here is that the typical time between two shock transitions a particle undergoes is much longer than the time of spectral formation at an individual shock. This allows the separation of the process of shock acceleration from other propagation effects. We consider as such particle escape from the system (catastrophic losses) and continuous energy losses. The interplay of shock acceleration and these other propagation effects leads to the formation of particle spectra with spectral features such as breaks at characteristic momenta, or humps. In particular, for special choices of the parameters describing the propagation of cosmic rays, results derived earlier (such as the spectral slope of particles produced by a periodic shock structure derived by Spruit, or the particle pile-up obtained by Schlickeiser) are reobtained. The approach followed in this paper is then compared with the one used by Blandford & Ostriker where they included an integral operator in the cosmic ray transport equation to describe impulsive acceleration. The theory considered here may find its application in the study of cosmic ray (re)acceleration in our galaxy, but is likely to be as important in other astrophysical environments, such as the central regions of active galactic nuclei, where we expect highly turbulent flows to be present. It can therefore be expected that in such objects there is a region in which many shocks are present. The multiple shock acceleration theory may then be used to study the formation of spectra in such objects.

Schneider, P.

1993-10-01

363

Study of a multi-beam accelerator driven thorium reactor  

SciTech Connect

The primary advantages that accelerator driven systems have over critical reactors are: (1) Greater flexibility regarding the composition and placement of fissile, fertile, or fission product waste within the blanket surrounding the target, and (2) Potentially enhanced safety brought about by operating at a sufficiently low value of the multiplication factor to preclude reactivity induced events. The control of the power production can be achieved by vary the accelerator beam current. Furthermore, once the beam is shut off the system shuts down. The primary difference between the operation of an accelerator driven system and a critical system is the issue of beam interruptions of the accelerator. These beam interruptions impose thermo-mechanical loads on the fuel and mechanical components not found in critical systems. Studies have been performed to estimate an acceptable number of trips, and the value is significantly less stringent than had been previously estimated. The number of acceptable beam interruptions is a function of the length of the interruption and the mission of the system. Thus, for demonstration type systems and interruption durations of 1sec < t < 5mins, and t > 5mins 2500/yr and 50/yr are deemed acceptable. However, for industrial scale power generation without energy storage type systems and interruption durations of t < 1sec., 1sec < t < 10secs., 10secs < t < 5mins, and t > 5mins, the acceptable number of interruptions are 25000, 2500, 250, and 3 respectively. However, it has also been concluded that further development is required to reduce the number of trips. It is with this in mind that the following study was undertaken. The primary focus of this study will be the merit of a multi-beam target system, which allows for multiple spallation sources within the target/blanket assembly. In this manner it is possible to ameliorate the effects of sudden accelerator beam interruption on the surrounding reactor, since the remaining beams will still be supplying source neutrons. The proton beam will be assumed to have an energy of 1 GeV, and the target material will be natural lead, which will also be the coolant for the reactor assembly. Three proton beam arrangements will be considered, first a single beam (the traditional arrangement) with an entry at the assembly center, two more options will consist of three and six entry locations. The reactor fuel assembly parameters will be based on those of the S-PRISM fast reactor proposed by GE, and the fuel composition and type will be based on that proposed by Aker Solutions for use in their accelerator driven thorium reactor. The following table summarizes the parameters to be used in this study. The isotopic composition of the fertile material is 100% Th-232, and the plutonium isotopic distribution corresponds to that characteristic of the discharge from a typical LWR, following five years of decay. Thus, the isotopic distribution for the plutonium is; Pu-238 2.5%, Pu-239 53.3%, Pu-240 25.1%, Pu-241 11.8%, and Pu-242 7.3%.

Ludewig, H.; Aronson, A.

2011-03-01

364

High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.  

PubMed

We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness bunches. This injection principle is explained by example of three-dimensional particle-in-cell calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blowout regime inside a fully ionized hydrogen plasma of density 5×10(17)cm-3. Within an embedded 100???m long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a 1.5 kA peak current, 1.5???m transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length. PMID:24483670

Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

2013-12-13

365

Particle propagation and acceleration in the heliosphere  

Microsoft Academic Search

A realistic model of interplanetary magnetic field perturbations is constructed using data from spacecraft and used to study pitch angle scattering suffered by energetic particles as they propagate in the heliosphere. The pitch angle diffusion coefficient is found to be always smaller than implied by quasi-linear theory, leading to radial mean free paths that are at least three times larger.

J. F. Valdes-Galicia; J. J. Quenby; X. Moussas

1988-01-01

366

Particle acceleration in reconnecting current sheets  

Microsoft Academic Search

We study motions of charged particles in reconnecting current sheets (CS) which have both transverse (perpendicular to the current sheet plane) and longitudinal (parallel to the electric current inside the sheet) components of the magnetic field. Such CS, called non-neutral, are formed in regions of magnetic field line reconnection in the solar atmosphere. We develop an analytical technique which allows

Yu. E. Litvinenko; B. V. Somov

1993-01-01

367

Beam by design: laser manipulation of electrons in modern accelerators  

E-print Network

Accelerator-based light sources such as storage rings and free-electron lasers use relativistic electron beams to produce intense radiation over a wide spectral range for fundamental research in physics, chemistry, materials science, biology and medicine. More than a dozen such sources operate worldwide, and new sources are being built to deliver radiation that meets with the ever increasing sophistication and depth of new research. Even so, conventional accelerator techniques often cannot keep pace with new demands and, thus, new approaches continue to emerge. In this article, we review a variety of recently developed and promising techniques that rely on lasers to manipulate and rearrange the electron distribution in order to tailor the properties of the radiation. Basic theories of electron-laser interactions, techniques to create micro- and nano-structures in electron beams, and techniques to produce radiation with customizable waveforms are reviewed. We overview laser-based techniques for the generation ...

Hemsing, Erik; Xiang, Dao; Zholents, Alexander

2014-01-01

368

Million revolution accelerator beam instrument for logging and evaluation  

SciTech Connect

A data acquisition and analysis instrument for the processing of accelerator beam position monitor (BPM) signals has been assembled and used preliminarily for beam diagnosis of the Fermilab accelerators. Up to eight BPM (or other analogue) channels are digitized and transmitted to an acquisition Sun workstation and from there both to a monitor workstation and a workstation for off-line (but immediate) data analysis. A coherent data description format permits fast data object transfers to and from memory, disk and tape, across the Sun ethernet. This has helped the development of both general purpose and experiment-specific data analysis, presentation and control tools. Flexible software permits immediate graphical display in both time and frequency domains. The instrument acts simultaneously as a digital oscilloscope, as a network analyzer and as a correlating, noise-reducing spectrum analyzer. 2 refs., 3 figs.

Peggs, S.; Saltmarsh, C.; Talman, R.

1988-03-01

369

Bipolar pulse generator for intense pulsed ion beam accelerator  

NASA Astrophysics Data System (ADS)

A new type of pulsed ion beam accelerator named "bipolar pulse accelerator" (BPA) has been proposed in order to improve the purity of intense pulsed ion beams. To confirm the principle of the BPA, we developed a bipolar pulse generator for the bipolar pulse experiment, which consists of a Marx generator and a pulse forming line (PFL) with a rail gap switch on its end. In this article, we report the first experimental result of the bipolar pulse and evaluate the electrical characteristics of the bipolar pulse generator. When the bipolar pulse generator was operated at 70% of the full charge condition of the PFL, the bipolar pulse with the first (-138kV, 72ns) and the second pulse (+130kV, 70ns) was successfully obtained. The evaluation of the electrical characteristics indicates that the developed generator can produce the bipolar pulse with fast rise time and sharp reversing time.

Ito, H.; Igawa, K.; Kitamura, I.; Masugata, K.

2007-01-01

370

Multiple-source models for electron beams of a medical linear accelerator using BEAMDP computer code  

PubMed Central

Aim The aim of this work was to develop multiple-source models for electron beams of the NEPTUN 10PC medical linear accelerator using the BEAMDP computer code. Background One of the most accurate techniques of radiotherapy dose calculation is the Monte Carlo (MC) simulation of radiation transport, which requires detailed information of the beam in the form of a phase-space file. The computing time required to simulate the beam data and obtain phase-space files from a clinical accelerator is significant. Calculation of dose distributions using multiple-source models is an alternative method to phase-space data as direct input to the dose calculation system. Materials and methods Monte Carlo simulation of accelerator head was done in which a record was kept of the particle phase-space regarding the details of the particle history. Multiple-source models were built from the phase-space files of Monte Carlo simulations. These simplified beam models were used to generate Monte Carlo dose calculations and to compare those calculations with phase-space data for electron beams. Results Comparison of the measured and calculated dose distributions using the phase-space files and multiple-source models for three electron beam energies showed that the measured and calculated values match well each other throughout the curves. Conclusion It was found that dose distributions calculated using both the multiple-source models and the phase-space data agree within 1.3%, demonstrating that the models can be used for dosimetry research purposes and dose calculations in radiotherapy. PMID:24377026

Jabbari, Nasrollah; Barati, Amir Hoshang; Rahmatnezhad, Leili

2012-01-01

371

Trends for Electron Beam Accelerator Applications in Industry  

NASA Astrophysics Data System (ADS)

Electron beam (EB) accelerators are major pieces of industrial equipment used for many commercial radiation processing applications. The industrial use of EB accelerators has a history of more than 50 years and is still growing in terms of both its economic scale and new applications. Major applications involve the modification of polymeric materials to create value-added products, such as heat-resistant wires, heat-shrinkable sheets, automobile tires, foamed plastics, battery separators and hydrogel wound dressing. The surface curing of coatings and printing inks is a growing application for low energy electron accelerators, resulting in an environmentally friendly and an energy-saving process. Recently there has been the acceptance of the use of EB accelerators in lieu of the radioactive isotope cobalt-60 as a source for sterilizing disposable medical products. Environmental protection by the use of EB accelerators is a new and important field of application. A commercial plant for the cleaning flue gases from a coal-burning power plant is in operation in Poland, employing high power EB accelerators. In Korea, a commercial plant uses EB to clean waste water from a dye factory.

Machi, Sueo

2011-02-01

372

Negative hydrogen ion source research and beam parameters for accelerators  

Microsoft Academic Search

H beams are useful for multi-turn charge-exchange stripping injection into circular accelerators. Studies on a modified ion source for this purpose are presented. This paper includes some theory about a H magnetron discharge, ion-electron emission, emittance and problems linked with emittance measurement and calculations. Investigated parameters of the emittance probe for optimal performance give a screen voltage of 150 V

Timofey V. Zolkin

2006-01-01

373

Particle accelerators inside spinning black holes.  

PubMed

On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical black holes are internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability. PMID:20867083

Lake, Kayll

2010-05-28

374

Spinning black holes as particle accelerators.  

PubMed

It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with an arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim to elucidate the mechanism for this fascinating result, and to point out its practical limitations, which imply that ultraenergetic collisions cannot occur near black holes in nature. PMID:20366583

Jacobson, Ted; Sotiriou, Thomas P

2010-01-15

375

On scaling properties of crossing the third-order resonance in particle accelerator  

SciTech Connect

We study effects of charged particle beams crossing a third-order resonance in an accelerator. The distortion of invariant torus during the resonance crossing is used to set 20% emittance growth or 2.5% of trap fraction as the critical resonance strength. We find a simple scaling law for the critical resonance strength vs the tune ramp rate and the initial emittance. The scaling law can be derived by solving Hamilton's equation of motion with stationary phase condition. Such scaling law can be used to evaluate the performance in high power accelerators, such as the FFAG and cyclotron.

Lee, S.Y.; Pang, X.; Jing, Y.; Luo, T.; /Indiana U.; Ng, K.Y.; /Fermilab

2011-12-01

376

Charged spinning black holes as particle accelerators  

SciTech Connect

It has recently been pointed out that the spinning Kerr black hole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning black hole, the Kerr-Newman black hole. The center-of-mass energy of collision for two uncharged particles falling freely from rest at infinity depends not only on the spin a but also on the charge Q of the black hole. We find that an unlimited center-of-mass energy can be approached with the conditions: (1) the collision takes place at the horizon of an extremal black hole; (2) one of the colliding particles has critical angular momentum; (3) the spin a of the extremal black hole satisfies (1/{radical}(3)){<=}(a/M){<=}1, where M is the mass of the Kerr-Newman black hole. The third condition implies that to obtain an arbitrarily high energy, the extremal Kerr-Newman black hole must have a large value of spin, which is a significant difference between the Kerr and Kerr-Newman black holes. Furthermore, we also show that, for a near-extremal black hole, there always exists a finite upper bound for center-of-mass energy, which decreases with the increase of the charge Q.

Wei Shaowen; Liu Yuxiao; Guo Heng; Fu Chune [Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000 (China)

2010-11-15

377

Hydrodynamic simulation of supernova remnants including efficient particle acceleration  

Microsoft Academic Search

A number of supernova remnants (SNRs) show nonthermal X-rays assumed to be synchrotron emission from shock accelerated TeV electrons. The existence of these TeV electrons strongly suggests that the shocks in SNRs are sources of galactic cosmic rays (CRs). In addition, there is convincing evidence from broad-band studies of individual SNRs and elsewhere that the particle acceleration process in SNRs

D. C. Ellison; Anne Decourchelle; Jean Ballet

2004-01-01

378

Characterization of a simple explosively driven particle acceleration  

SciTech Connect

Experiments are carried out to characterize the performance of a compact cylindrical (2-inch x 3-inch-long) single-point detonation ring-lit fast shock tube that has been designed to accelerate particles to velocity in excess of 10 km/s. The experimental results from the study of propellant flow and plate acceleration will be presented and compared with the code calculation. Various interesting measurement techniques will also be discussed.

Tan, T.H.; Fritz, J.N.; Marsh, S.P.; McQueen, R.G.; Steele, R.D.

1987-01-01

379

Energetic particle acceleration at corotating interaction regions: Ulysses results  

SciTech Connect

We present here statistical properties of energetic ions (tilde 1 MeV) accelerated by corotating interaction regions observed at the Ulysses spacecraft. We have correlated the tilde 1 MeV proton intensity measured near the trailing edges of the interaction regions with their compression ratio. We interpret our results in terms of the plasma conditions experienced at Ulysses and identify a likely source of the low energy seed particles accelerated at the interaction regions.

Desai, M.I.; Marsden, R.G.; Sanderson, T.R. [ESTEC/ESA, Noordwijk (Netherlands). Space Science Dept.; Balogh, A.; Forsyth, R.J. [Imperial Coll., London (United Kingdom). Blackett Lab.; Gosling, J.T. [Los Alamos National Lab., NM (United States)

1997-07-01

380

LONGITUDINAL REFERENCE PARTICLE MOTION IN NEARLY ISOCHRONOUS FFAG RECIRCULATING ACCELERATORS.  

SciTech Connect

A Fixed Field Alternating Gradient (FFAG) arc can be used to reduce the cost of a recirculating accelerator. Path length variation with energy in such an arc can limit its usefulness, however, due to phase offset at the linac. This paper examines the dynamics of the reference particle in an FFAG recirculating accelerator, and describes the limitations on the design because of path length variation with energy.

BERG,J.S.

2001-07-01

381

The Maximum Energy of Accelerated Particles in Relativistic Collisionless Shocks  

NASA Astrophysics Data System (ADS)

The afterglow emission from gamma-ray bursts (GRBs) is usually interpreted as synchrotron radiation from electrons accelerated at the GRB external shock that propagates with relativistic velocities into the magnetized interstellar medium. By means of multi-dimensional particle-in-cell simulations, we investigate the acceleration performance of weakly magnetized relativistic shocks, in the magnetization range 0 <~ ? <~ 10-1. The pre-shock magnetic field is orthogonal to the flow, as generically expected for relativistic shocks. We find that relativistic perpendicular shocks propagating in electron-positron plasmas are efficient particle accelerators if the magnetization is ? <~ 10-3. For electron-ion plasmas, the transition to efficient acceleration occurs for ? <~ 3 × 10-5. Here, the acceleration process proceeds similarly for the two species, since the electrons enter the shock nearly in equipartition with the ions, as a result of strong pre-heating in the self-generated upstream turbulence. In both electron-positron and electron-ion shocks, we find that the maximum energy of the accelerated particles scales in time as ?maxvpropt 1/2. This scaling is shallower than the so-called (and commonly assumed) Bohm limit ?maxvpropt, and it naturally results from the small-scale nature of the Weibel turbulence generated in the shock layer. In magnetized plasmas, the energy of the accelerated particles increases until it reaches a saturation value ?sat/?0 mic 2 ~ ?-1/4, where ?0 mic 2 is the mean energy per particle in the upstream bulk flow. Further energization is prevented by the fact that the self-generated turbulence is confined within a finite region of thickness vprop?-1/2 around the shock. Our results can provide physically grounded inputs for models of non-thermal emission from a variety of astrophysical sources, with particular relevance to GRB afterglows.

Sironi, Lorenzo; Spitkovsky, Anatoly; Arons, Jonathan

2013-07-01

382

Optimisation of the pointing stability of laser-wakefield accelerated electron beams  

E-print Network

Laser-wakefield acceleration is a promising technique for the next generation of ultra-compact, high-energy particle accelerators. However, for a meaningful use of laser-driven particle beams it is necessary that they present a high degree of pointing stability in order to be injected into transport lines and further acceleration stages. Here we show a comprehensive experimental study of the main factors limiting the pointing stability of laser-wakefield accelerated electron beams. It is shown that gas-cells provide a much more stable electron generation axis, if compared to gas-jet targets, virtually regardless of the gas density used. A sub-mrad shot-to-shot fluctuation in pointing is measured and a consistent non-zero offset of the electron axis in respect to the laser propagation axis is found to be solely related to a residual angular dispersion introduced by the laser compression system and can be used as a precise diagnostic tool for compression oprtimisation in chirped pulse amplified lasers.

Garland, R J; Cole, J; Schumaker, W; Doria, D; Gizzi, L A; Grittani, G; Krushelnick, K; Kuschel, S; Mangles, S P D; Najmudin, Z; Symes, D; Thomas, A G R; Vargas, M; Zepf, M; Sarri, G

2014-01-01

383

Particle production and survival in muon acceleration  

SciTech Connect

Because of the relative immunity of muons to synchrotron radiation, the idea of using them instead of electrons as probes in high-energy physics experiments has existed for some time, but applications were limited by the short muon lifetime. The production and survival of an adequate supply of low-emittance muons will determine the available luminosity in a high-energy physics collider. In this paper the production of pions by protons, their decay to muons and the survival of muons during acceleration are studied. Based on a combination of the various efficiencies, the number of protons needed at the pion source for every muon required in the final high-energy collider is estimated.

Noble, R.J.

1992-06-01

384

Particle Acceleration by Cme-driven Shock Waves  

NASA Technical Reports Server (NTRS)

In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

Reames, Donald V.

1999-01-01

385

NON-STANDARD ENERGY SPECTRA OF SHOCK-ACCELERATED SOLAR PARTICLES  

SciTech Connect

We consider a numerical model for the shock acceleration of energetic ions in the magnetic environment of the solar corona. The model is motivated by observations of the deka-to-hecto-MeV proton energy spectra, ion and electron timing, and abundances in the beginning of major solar energetic particle (SEP) events, prior to the event's main phase associated with coronal mass ejection (CME) driven shock in the solar wind. Inasmuch as the obliquity of the CME-liftoff-associated shocks in solar corona and hence the seed-particle supply for the shock acceleration are essentially time dependent, a steady state energy spectrum of accelerated protons near the shock could not be attained. Energy spectrum of the SEP emission depends on the spatial and energy distribution of seed particles for the coronal shock acceleration, on the shock wave history, and on the location and scenario of the energetic particle escape into the interplanetary medium. We use a numerical model of the shock acceleration on a semicircular magnetic field line to learn a significance of different effects. If the shock geometry in a particular magnetic tube changes from nearly parallel to perpendicular, the resulting SEP spectrum in most distant sections of the tube, e.g., at the top of a transequatorial loop, resembles a wide beam, which is very different from the standard power-law spectrum that would be expected in a steady state. Possible escape of the shock-accelerated particles from more than one coronal location, stochastic re-acceleration, and the magnetic tube expansion can make the SEP spectra even more complicated.

Kocharov, Leon; Vainio, Rami; Pomoell, Jens [Department of Physics, P.O. Box 64, University of Helsinki, FI-00014 (Finland); Valtonen, Eino [Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 (Finland); Klassen, Andreas [Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet Kiel, D-24118 (Germany); Young, C. Alex [ADNET Systems Inc., NASA Goddard Space Flight Center, Greenbelt, MD 20850 (United States)

2012-07-01

386

Compressive-Diffusive Acceleration of Energetic Charged Particles  

NASA Astrophysics Data System (ADS)

We discuss the phenomenon of the acceleration of charged particles in a compressing di~@usive medium and apply it to recent ACE observations in the interplanetary medium. It has been recognized that the phenomenon of di~@usive shock acceleration can readily be generalized to the case where the the shock isreplaced by a gradual change in the velocity of the ~Bow over a length scale LL . Let U be the ~Bow speed and ? the energetic particle di~@usion coe~Ccientt normal to the plane of the compression. Then, if the dimensionless parameter ?/(UL) is large compared with unity, the energetic particles are accelerated much as indi~@usive shock acceleration. We have applied this to the case of a co-rotatinn g interaction region near the Sun, where it has not yet developed into a shock. We ~And signi~Acant acceleration of charged particles. Our results are compaa red with recent observations carried out on the ACE spacecraft.

Jokipii, J. R.; Kota, J.; Giacalone, J.

2001-08-01

387

Case Studies in Space Charge and Plasma Acceleration of Charged Beams  

E-print Network

Plasma acceleration with electron or proton driver beams is a challenging opportunity for high energy physics. An energy doubling experiment with electron drivers was successfully performed at SLAC and a key experiment AWAKE with proton drivers is on schedule at CERN. Simulations play an important role in choosing the best experimental conditions and in interpreting the results. The Vlasov equation is the theoretical tool to describe the interaction of a driver particle beam or a driver laser pulse with a plasma. Collective effects, such as tune shift and mismatch instabilities, appear in high intensity standard accelerators and are described by the Poisson-Vlasov equation. In the paper we review the Vlasov equation in electrostatic and fully electromagnetic case. The general framework of variational principles is used to derive the equation, the local form of the balance equations and related conservation laws. In the electrostatic case we remind the analytic Kapchinskij-Vladimirskij (K-V) model and we propo...

Bazzani, A; Londrillo, P; Sinigardi, S; Turchetti, G

2014-01-01

388

Efficient acceleration of monoenergetic proton beam by sharp front laser pulse  

SciTech Connect

Stable acceleration of relativistic ions by the radiation pressure of a superintense, circularly polarized laser pulse with sharp front is investigated by analytical modeling and particle-in-cell simulation. For foils with given density and thickness, the suitable steepness of the laser front is found to suppress instabilities and efficiently drive a stable monoenergetic ion beam. With a laser pulse of peak amplitude a{sub 0}=200, a proton beam of energy about 10 GeV can be generated. The dynamics of the laser-compressed electron layer and the ions in the hole-boring stage are investigated. In the case studied, the ions initially in the middle of the target are found to be accelerated to the back surface of the target ahead of the other ions.

Wang, W. P.; Shen, B. F.; Zhang, X. M.; Ji, L. L.; Wen, M.; Xu, J. C.; Yu, Y. H.; Xu, Z. Z. [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China); Li, Y. L. [Accelerator Systems Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) and Argonne Accelerator Institute, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2011-01-15

389

Resolving EMI Issues To Optimize Accelerator Beam Diagnostic Performance  

SciTech Connect

If you have struggled to get the last bit of performance from a beam diagnostic only to find your dynamic range limited by external sources of electromagnetic interference (EMI) once the system is installed, then you will find this tutorial on electromagnetic compatibility and grounding useful. The tutorial will provide some simple, direct methods to analyze, understand and mitigate the impact of EMI on beam diagnostic systems. Several common and unique accelerator EMI sources will be characterized. The dependencies of source frequency and distance to the source on the optimal choice of grounding and shielding methods will be illustrated. The emphasis is on a stepwise process that leads to understanding and cost-effective resolution of EMI impacts on beam diagnostic systems.

Thuot, Michael [Los Alamos National Laboratory, LANSCE Division, Los Alamos, New Mexico (United States)

2004-11-10

390

Negative hydrogen ion source research and beam parameters for accelerators  

SciTech Connect

H{sup -} beams are useful for multi-turn charge-exchange stripping injection into circular accelerators. Studies on a modified ion source for this purpose are presented. This paper includes some theory about a H{sup -} magnetron discharge, ion-electron emission, emittance and problems linked with emittance measurement and calculations. Investigated parameters of the emittance probe for optimal performance give a screen voltage of 150 V and a probe step of about 5 mil. Normalized 90% emittance obtained for this H{sup -} source is 0.22 {pi} mm-mr, for an extraction voltage of 18 kV at a beam energy of 30 keV and a beam current of 11 mA.

Zolkin, Timofey V.; /Fermilab

2006-09-01

391

A Plasma Drag Hypervelocity Particle Accelerator (HYPER)  

NASA Technical Reports Server (NTRS)

Current debris models are able to predict the growth of the space debris problem and suggest that spacecraft must employ armor or bumper shields for some orbital altitudes now and that the problem will become worse as a function of time. The practical upper limit to the velocity distribution is on the order of 40 km/s and is associated with the natural environment. The velocity distribution of the man-made component peaks at 9-10 km/s with maximum velocity in the 14-16 km/s range. Experience in space has verified that the "high probability of impact" particles are in the microgram to milligram range. These particles can have very significant effects on coatings, insulators, and thin metallic layers. The surface of thick materials becomes pitted and the local debris component is enhanced by ejecta from the impact events. In this paper, the HYPER facility is described which produces a reasonable simulation of the man-made space debris spectrum in a controlled environment. The facility capability is discussed in terms of drive geometry, energetics, velocity distribution, diagnostics, and projectile/debris loading. The facility has been used to study impact phenomena on Space Station Freedom's solar array structure, the calibration of space debris collectors, other solar array materials, potential structural materials for use in space, electrical breakdown in the space environment, and as a means of clarifying or duplicating the impact phenomena on surfaces which have been exposed in space.

Best, Steve R.; Rose, M. Frank

1998-01-01

392

Beam Momentum Changes due to Discharges in High-gradient Accelerator Structures  

E-print Network

The key questions left unanswered by the Standard Model, and the recent discovery of a Standard Model-like Higgs boson, demand an extension of the research on particle physics to the TeV energy scale. The Compact Linear Collider, CLIC, is a candidate project to achieve such goal. It is a linear lepton collider based on a novel two-beam acceleration scheme capable of high-gradient acceleration in X-band accelerator structures. The high electric fields required, however, entail the occurrence of vacuum discharges, or rf breakdowns, a phenomenon whose microscopic dynamics is not yet completely understood, and whose impact on the beam can lead to a severe degradation of the collider luminosity. The understanding of the physics of rf breakdowns has therefore become a significant issue in the design of a reliable accelerator based on CLIC technology. That is addressed experimentally through the study of accelerator structures performance during high-power operations. We report on such a study carried out on a CLIC...

Palaia, Andrea; Ruber, Roger; Ekelöf, Tord

2013-11-21

393

Stochastic particle acceleration and statistical closures  

SciTech Connect

In a recent paper, Maasjost and Elsasser (ME) concluded, from the results of numerical experiments and heuristic arguments, that the Bourret and the direct-interaction approximation (DIA) are ''of no use in connection with the stochastic acceleration problem'' because (1) their predictions were equivalent to that of the simpler Fokker-Planck (FP) theory, and (2) either all or none of the closures were in good agreement with the data. Here some analytically tractable cases are studied and used to test the accuracy of these closures. The cause of the discrepancy (2) is found to be the highly non-Gaussian nature of the force used by ME, a point not stressed by them. For the case where the force is a position-independent Ornstein-Uhlenbeck (i.e., Gaussian) process, an effective Kubo number K can be defined. For K << 1 an FP description is adequate, and conclusion (1) of ME follows; however, for K greater than or equal to 1 the DIA behaves much better qualitatively than the other two closures. For the non-Gaussian stochastic force used by ME, all common approximations fail, in agreement with (2).

Dimits, A.M.; Krommes, J.A.

1985-10-01

394

Program development for the modelling of carbon wire heating by particle beams:  

E-print Network

A wire scanner is a device which moves a thin carbon target fast through a particle beam with a constant velocity [1]. They are widely used in accelerators to measure the beam profile, because they provide accurate measurements with a resolution down to 1 micrometer. In a high intensity beam the target suffers from strong heating, from the the electromagnetic coupling to the beam current [2]. After the fast initial heating, the wire is cooled down by various processes – heat transport along the wire, thermal radiation and thermionic emission. It might even sublimate or melt. The particles produced during the proton passage through the wire are measured in the detectors outside the vacuum pipe and based on their intensity the beam profile is reconstructed.

Vester, Peter

2014-01-01

395

Steps Toward an Innovative Electrospray-Based Particle Source for Dust Accelerators  

NASA Astrophysics Data System (ADS)

We are developing a new particle source for dust accelerators that charges particles regardless of their electrical conductivity. This overcomes a major limitation of current dust accelerator particle sources.

Daly, R. T.; Kerby, J. D.; Austin, D. E.

2012-03-01

396

On-line system identification for control system applications in particle accelerators  

NASA Astrophysics Data System (ADS)

Particle accelerators require a number of feedback systems in order to stabilize a variety of parameters. The Continuous Electron Beam Accelerator at Thomas Jefferson National Accelerator Facility presents a unique set of control and identification problems. This accelerator produces a continuous electron beam with energies between 0.5 and 4.0 GeV to be delivered to the experimental halls. In order to meet stringent beam quality requirements specified by the experimental halls, the position and the energy of the electron beam needs to stabilized at various locations in the accelerator. A number of noise measurement tests were conducted at various locations in the accelerator to obtain accurate information about the amplitude and the frequency of disturbances on the beam orbit and energy. Results of these measurements indicate that the line power harmonics were the primary source of disturbance on the beam orbit and energy. A prototype fast feedback system was implemented in the injector and the East Arc regions of the accelerator to stabilize the beam position and energy at these locations. The scheme of implementation of these systems and measurements of their performance are presented here. These feedback systems have to operate under conditions of varying noise characteristics and changing dynamics of the systems. For the feedback systems to always perform optimally, the knowledge of time varying noise characteristics and changing system dynamics needs to be incorporated into the feedback strategy. The approach presented in this work is to perform on-line system identification using a formulation of Fast Transversal Filter (FTF) in order to extract the time varying information from input/output data of the feedback system. A simulation test stand was developed using an analog computer to represent a continuous time system whose noise characteristics and dynamics could be changed in a controlled manner. An on-line system identification algorithm was implemented on a microprocessor similar to the ones used in the accelerator control system. Experience with the hardware-in-loop simulation for various cases of changing system dynamics and noise characteristics and the performance results of the on- line system identification algorithm operating under these conditions are presented in this dissertation.

Chowdhary, Mahesh

1997-08-01

397

Particle acceleration in helical magnetic fields in the corona  

NASA Astrophysics Data System (ADS)

Twisted magnetic fields should be ubiquitous in the solar corona. Emerging twisted ropes as well as complex photospheric motions provide continuous influx of the magnetic helicity. Twisted coronal fields, in turn, contain excess magnetic energy, which can be released, causing solar flares and other explosive phenomena. It has been shown recently, that reconnection in helical magnetic structures results in particle acceleration distributed within large volume, including the lower corona and chromosphere. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated in a small volume located in the upper corona. We discuss our recent results on the energy release and particle acceleration during magnetic reconnection in twisted coronal loops. Evolution of various helical structures is described in terms of resistive MHD, including heat conduction and radiation. We consider the effects of field topology and photospheric motions on the energy accumulation and release. In particular, we focus on scenarios with continuous helicity injection, leading to recurrent explosive events. Using the obtained MHD models, ion and electron acceleration is investigated, taking into account Coulomb collisions. We derive time-dependent energy spectra and spatial distribution for these species, and calculate resulting non-thermal radiation intensities. Based on the developed numerical models, we investigate observational implications of particle acceleration in helical magnetic structures. Thus, we compare temporal variations of thermal and non-thermal emission in different configurations. Furthermore, we consider spatial distributions of the thermal EUV and X-ray emission and non-thermal X-ray emission and compare them with observational data.

Gordovskyy, Mykola; Browning, Philippa; Bareford, Michael; Pinto, Rui; Kontar, Eduard; Bian, Nicolas

2014-05-01

398

Particle acceleration by inductive electric fields in the inner magnetosphere  

Microsoft Academic Search

We review some features of charged particle dynamics during substorm dipolarization of the magnetic field lines in the inner magnetosphere. In the parallel direction, particles traveling at low latitudes are subjected to prominent equatorward-oriented acceleration due to the rapid direction-changing E×B drift. This centrifugal effect leads to focusing of ions with small parallel speeds into the equatorial region, which in

D. C. Delcourt

2002-01-01

399

When is quasi-linear theory exact. [particle acceleration  

NASA Technical Reports Server (NTRS)

We use the cumulant expansion technique of Kubo (1962, 1963) to derive an integrodifferential equation for the average one-particle distribution function for particles being accelerated by electric and magnetic fluctuations of a general nature. For a very restricted class of fluctuations, the equation for this function degenerates exactly to a differential equation of Fokker-Planck type. Quasi-linear theory, including the adiabatic assumption, is an exact theory only for this limited class of fluctuations.

Jones, F. C.; Birmingham, T. J.

1975-01-01

400

A compact solution for ion beam therapy with laser accelerated protons  

NASA Astrophysics Data System (ADS)

The recent advancements in the field of laser-driven particle acceleration have made Laser-driven Ion Beam Therapy (L-IBT) an attractive alternative to the conventional particle therapy facilities. To bring this emerging technology to clinical application, we introduce the broad energy assorted depth dose deposition model which makes efficient use of the large energy spread and high dose-per-pulse of Laser Accelerated Protons (LAP) and is capable of delivering homogeneous doses to tumors. Furthermore, as a key component of L-IBT solution, we present a compact iso-centric gantry design with 360° rotation capability and an integrated shot-to-shot energy selection system for efficient transport of LAP with large energy spread to the patient. We show that gantry size could be reduced by a factor of 2-3 compared to conventional gantry systems by utilizing pulsed air-core magnets.

Masood, U.; Bussmann, M.; Cowan, T. E.; Enghardt, W.; Karsch, L.; Kroll, F.; Schramm, U.; Pawelke, J.

2014-10-01

401

Particle Acceleration via Reconnection Processes in the Supersonic Solar Wind  

NASA Astrophysics Data System (ADS)

An emerging paradigm for the dissipation of magnetic turbulence in the supersonic solar wind is via localized small-scale reconnection processes, essentially between quasi-2D interacting magnetic islands. Charged particles trapped in merging magnetic islands can be accelerated by the electric field generated by magnetic island merging and the contraction of magnetic islands. We derive a gyrophase-averaged transport equation for particles experiencing pitch-angle scattering and energization in a super-Alfvénic flowing plasma experiencing multiple small-scale reconnection events. A simpler advection-diffusion transport equation for a nearly isotropic particle distribution is derived. The dominant charged particle energization processes are (1) the electric field induced by quasi-2D magnetic island merging and (2) magnetic island contraction. The magnetic island topology ensures that charged particles are trapped in regions where they experience repeated interactions with the induced electric field or contracting magnetic islands. Steady-state solutions of the isotropic transport equation with only the induced electric field and a fixed source yield a power-law spectrum for the accelerated particles with index ? = –(3 + MA )/2, where MA is the Alfvén Mach number. Considering only magnetic island contraction yields power-law-like solutions with index –3(1 + ? c /(8?diff)), where ? c /?diff is the ratio of timescales between magnetic island contraction and charged particle diffusion. The general solution is a power-law-like solution with an index that depends on the Alfvén Mach number and the timescale ratio ?diff/? c . Observed power-law distributions of energetic particles observed in the quiet supersonic solar wind at 1 AU may be a consequence of particle acceleration associated with dissipative small-scale reconnection processes in a turbulent plasma, including the widely reported c –5 (c particle speed) spectra observed by Fisk & Gloeckler and Mewaldt et al.

Zank, G. P.; le Roux, J. A.; Webb, G. M.; Dosch, A.; Khabarova, O.

2014-12-01

402

Commissioning measurements for photon beam data on three TrueBeam linear accelerators, and comparison with Trilogy and Clinac 2100 linear accelerators.  

PubMed

This study presents the beam data measurement results from the commissioning of three TrueBeam linear accelerators. An additional evaluation of the measured beam data within the TrueBeam linear accelerators contrasted with two other linear accelerators from the same manufacturer (i.e., Clinac and Trilogy) was performed to identify and evaluate any differences in the beam characteristics between the machines and to evaluate the possibility of beam matching for standard photon energies. We performed a comparison of commissioned photon beam data for two standard photon energies (6 MV and 15 MV) and one flattening filter-free ("FFF") photon energy (10 FFF) between three different TrueBeam linear accelerators. An analysis of the beam data was then performed to evaluate the reproducibility of the results and the possibility of "beam matching" between the TrueBeam linear accelerators. Additionally, the data from the TrueBeam linear accelerator was compared with comparable data obtained from one Clinac and one Trilogy linear accelerator models produced by the same manufacturer to evaluate the possibility of "beam matching" between the TrueBeam linear accelerators and the previous models. The energies evaluated between the linear accelerator models are the 6 MV for low energy and the 15 MV for high energy. PDD and output factor data showed less than 1% variation and profile data showed variations within 1% or 2 mm between the three TrueBeam linear accelerators. PDD and profile data between the TrueBeam, the Clinac, and Trilogy linear accelerators were almost identical (less than 1% variation). Small variations were observed in the shape of the profile for 15 MV at shallow depths (< 5 cm) probably due to the differences in the flattening filter design. A difference in the penumbra shape was observed between the TrueBeam and the other linear accelerators; the TrueBeam data resulted in a slightly greater penumbra width. The diagonal scans demonstrated significant differences in the profile shapes at a distance greater than 20 cm from the central axis, and this was more notable for the 15 MV energy. Output factor differences were found primarily at the ends of the field size spectrum, with observed differences of less than 2% as compared to the other linear accelerators. The TrueBeam's output factor varied less as a function of field size than the output factors for the previous models; this was especially true for the 6 MV. Photon beam data were found to be reproducible between different TrueBeam linear accelerators well within the accepted clinical tolerance of ± 2%. The results indicate reproducibility in the TrueBeam machine head construction and a potential for beam matching between these types of linear accelerators. Photon beam data (6 MV and 15 MV) from the Trilogy and Clinac 2100 showed several similarities and some small variations when compared to the same data measured on the TrueBeam linear accelerator. The differences found could affect small field data and also very large field sizes in beam matching considerations between the TrueBeam and previous linear accelerator models from the same manufacturer, but should be within the accepted clinical tolerance for standard field sizes and standard treatments. PMID:23318395

Beyer, Gloria P

2013-01-01

403

Design principles for high quality electron beams via colliding pulses in laser plasma accelerators  

NASA Astrophysics Data System (ADS)

Laser plasma based accelerators have the potential to reduce dramatically the size and cost of future particle colliders and light sources. Production of high quality beams along with reproducibility, tunability, and efficiency are required for many applications. We present design principles for two-pulse colliding laser pulse injection mechanisms, which can meet these requirements. Simulations are used to determine the best conditions for the production of high quality beams: high charge, low energy spread, and low emittance. Simulations also allow access to the internal dynamics of the interaction, providing insight regarding further improvement of the beam quality. We find that a 20 pC beam can be accelerated to 300 MeV in 4 mm with only a few percent energy spread and transverse normalized emittance close to 1 mm mrad, using a 10 TW laser. We demonstrate that this design scales according to linear theory. Control of the laser pulse mode content and subsequent evolution in the plasma channel are shown to be critical for achieving the highest beam quality.

Cormier-Michel, E.; Ranjbar, V. H.; Bruhwiler, D. L.; Cary, J. R.; Chen, M.; Geddes, C. G. R.; Plateau, G. R.; Matlis, N. H.; Leemans, W. P.

2014-09-01

404

THE CONTINUOUS ELECTRON BEAM ACCELERATOR FACILITY: CEBAF at the Jefferson Laboratory  

NASA Astrophysics Data System (ADS)

The Jefferson Laboratory's superconducting radiofrequency (srf) Continuous Electron Beam Accelerator Facility (CEBAF) provides multi-GeV continuous-wave (cw) beams for experiments at the nuclear and particle physics interface. CEBAF comprises two antiparallel linacs linked by nine recirculation beam lines for up to five passes. By the early 1990s, accelerator installation was proceeding in parallel with commissioning. By the mid-1990s, CEBAF was providing simultaneous beams at different but correlated energies up to 4 GeV to three experimental halls. By 2000, with srf development having raised the average cavity gradient to 7.5 MV/m, energies up to nearly 6 GeV were routine, at 1-150 µA for two halls and 1-100 nA for the other. Also routine are beams of >75% polarization. Physics results have led to new questions about the quark structure of nuclei, and therefore to user demand for a planned 12 GeV upgrade. CEBAF's enabling srf technology is also being applied in other projects.

Leemann, Christoph W.; Douglas, David R.; Krafft, Geoffrey A.

405

Designing accelerator-based epithermal neutron beams for boron neutron capture therapy.  

PubMed

The 7Li(p,n)7Be reaction has been investigated as an accelerator-driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials, Al/AlF3, 7LiF, and D2O, have been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte Carlo N-particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth-dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator-based neutron source with Al/AlF3 or 7LiF as moderator material can produce depth-dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to approximately 50% higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and a 7LiF moderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy-Eq. PMID:9775379

Bleuel, D L; Donahue, R J; Ludewigt, B A; Vujic, J

1998-09-01

406

Roles for neutral particle beams in strategic defense  

Microsoft Academic Search

Neutral particle beams can play a number of unique, critical roles in strategic defense because of their robust mechanism for discrimination and kill. Their operation, status, and applications are evaluated, showing that their near term roles are complementary to kinetic energy weapons. In addition, particle beams are shown to be the primary candidates for interrogating space objects, discriminating numerous light

G. H. Canavan; J. Browne

1988-01-01

407

GENERATION AND CONTROL OF HIGH PRECISION BEAMS AT LEPTON ACCELERATORS  

SciTech Connect

Parity violation experiments require precision manipulation of helicity-correlated beam coordinates on target at the nm/nrad-level. Achieving this unprecedented level of control requires a detailed understanding of the particle optics and careful tuning of the beam transport to keep anomalies from compromising the design adiabatic damping. Such efforts are often hindered by machine configuration and instrumentation limitations at the low energy end. A technique has been developed at CEBAF including high precision measurements, Mathematica-based analysis for obtaining corrective solutions, and control hardware/software developments for realizing such level of control at energies up to 5 GeV.

Yu-Chiu Chao

2007-06-25

408

GEANT4 SIMULATIONS OF GAMMA-RAY EMISSION FROM ACCELERATED PARTICLES IN SOLAR FLARES  

SciTech Connect

Gamma-ray spectroscopy provides diagnostics of particle acceleration in solar flares, but care must be taken when interpreting the spectra due to effects of the angular distribution of the accelerated particles (such as relativistic beaming) and Compton reprocessing of the radiation in the solar atmosphere. In this paper, we use the GEANT4 Monte Carlo package to simulate the interactions of accelerated electrons and protons and study the effects of these interactions on the gamma rays resulting from electron bremsstrahlung and pion decay. We consider the ratio of the 511 keV annihilation-line flux to the continuum at 200 keV and in the energy band just above the nuclear de-excitation lines (8-15 MeV) as a diagnostic of the accelerated particles and a point of comparison with data from the X17 flare of 2003 October 28. We also find that pion secondaries from accelerated protons produce a positron annihilation line component at a depth of {approx}10 g cm{sup -2} and that the subsequent Compton scattering of the 511 keV photons produces a continuum that can mimic the spectrum expected from the 3{gamma} decay of orthopositronium.

Tang Shichao [Department of Physics and Center for Astrophysics, Tsinghua University, Beijing 10084 (China); Smith, David M. [Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States)

2010-10-01

409

Radiation from Accelerated Particles in Shocks and Reconnections  

NASA Technical Reports Server (NTRS)

Plasma instabilities are responsible not only for the onset and mediation of collisionless shocks but also for the associated acceleration of particles. We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection and, more generally, relativistic acceleration behind the shock. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. Our initial results of a jet-ambient interaction with anti-parallelmagnetic fields show pile-up of magnetic fields at the colliding shock, which may lead to reconnection and associated particle acceleration. We will investigate the radiation in a transient stage as a possible generation mechanism of precursors of prompt emission. In our simulations we calculate the radiation from electrons in the shock region. The detailed properties of this radiation are important for understanding the complex time evolution and spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Nishikawa, K. I.; Choi, E. J.; Min, K. W.; Niemiec, J.; Zhang, B.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

2012-01-01

410

Particle accelerators in space: resolving them for the first time  

NASA Astrophysics Data System (ADS)

The detection of optical counterparts of hot spots in radio galaxies has been a challenge in astrophysics since the 1960s. Being located at several 100 kpc away from the AGN, they represent the most striking sites of interaction between the AGN ejecta and the ambient inter-galactic medium. Particle acceleration is thought to drive their emission and therefore, due to their remote locations, hot spots are the best laboratories to study the physics of that mechanism in detail. Using carefully directed selection criteria and the VLT we have discovered hot spots in the optical at an unprecedented detection rate, all of them disclosing very intriguing structure. This structure pinpoints the regions where electrons are accelerated to highly relativistic energies -- the particle accelerators. With HST we aim at resolving these accelerators for the very first time. This will enable us to establish the nature and origin of these relativistic particles in the hot spots of radio galaxies. The results of these studies not only represent a key for understanding the evolution of radio sources but also provide important input to plasma acceleration problems in general.

Prieto, Almudena

2004-07-01

411

Particle Diffusion and Localized Acceleration in Inhomogeneous AGN Jets  

NASA Astrophysics Data System (ADS)

We present an inhomogeneous AGN jet model built on our time-dependent multi-zone radiation code that permits studying how particle acceleration and spatial diffusion complicate the energy-dependent jet inhomogeneity.In the code, a Fokker-Planck equation is used to describe the electrons accelerated through a second-order Fermi process. A Monte Carlo method is used for the radiative transfer, so that light travel time effects are taken into account.To account for inhomogeneity, we use a 2D axi-symmetric cylindrical geometry for both relativistic electrons and magnetic field. We found that small isolated acceleration regions in a much larger emission volume are sufficient to generate high energy particles needed for the X-ray and gamma-ray emission. Diffusive escape from these regions provides a natural explanation for the spectral form of the jet emission. Characteristic spectral hardening can be identified at high energies if diffusive escape is relatively inefficient.Various possible geometries and locations of the acceleration region are evaluated to further assess the structure of the relativistic jets and the energy dissipation processes in them. If the acceleration region is not located at the center of the emission region, the electron spectrum is an atypical broken power-law. The change in the power-law index, which is a result of both particle cooling and escape, is less than 1, the traditionally assumed value.

Chen, Xuhui; Pohl, Martin; Boettcher, Markus

2014-08-01

412

Improved dispensing targets for ion beam particle generators  

NASA Technical Reports Server (NTRS)

Beam impinges on palladium-silver tube, which is target, and heats impinged surface causing local hot spot. Contained gas diffuses through hot spot to meet incoming beam and produce desired particles. When beam is turned off, target spot cools and stops dispensing contained gas.

Miller, C. G.

1974-01-01

413

PARTICLE ACCELERATION BY ELECTROSTATIC WAVES WITH SPATIALLY VARYING PHASE VELOCITIES  

Microsoft Academic Search

We present here the results of numerical calculations connected with a mechanism recently proposed [Swift, 1968] for the acceleration of charged particles in a strong dc magnetic field. An electrostatic plasma wave propagates nearly perpendicularly to the magnetic field, and a weak density gradient exists parallel to the magnetic field. The wave propagates into the region of increasing plasma density

S. Peter Gary; David Montgomery; Daniel W. Swift

1968-01-01

414

Stochastic and Adiabatic Behavior of Particles Accelerated by Periodic Forces  

Microsoft Academic Search

The mechanism by which periodic nonrandom forces lead to stochastic acceleration of particles is examined. Two examples considered are (i) the Fermi problem of a ball bouncing between a fixed and an oscillating wall, with various wall-oscillation functions, and (ii) cyclotron-resonance heating in a magnetic mirror. Numerical studies show that the phase plane consists of a complicated but regular structure

M. A. Lieberman; A. J. Lichtenberg

1972-01-01

415

Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron  

E-print Network

, particle and astroparticle physics as well as accelerator physics. The Center for Free-Electron Laser) and its use in phase stabilized few-cycle pulse synthesizers, Free-Electron Lasers and Attosecond Science � Development of turn-key, burst-mode, OPCPA technology for Free- Electron Lasers, including, thermal management

416

Particle acceleration in solar flares: observations versus numerical simulations  

E-print Network

Particle acceleration in solar flares: observations versus numerical simulations A O Benz, P C@astro.phys.ethz.ch Abstract. Solar flares are generally agreed to be impulsive releases of magnetic energy. Reconnection­ray observations, transit­time damping simulation, reconnection, astrophysics #12; 2 1. Introduction Solar flares

417

Critical Issues For Understanding Particle Acceleration in Impulsive Solar Flares  

Microsoft Academic Search

This paper, a review of the present status of existing models for particle acceleration during impulsive solar flares, was inspired by a week-long workshop held in the Fall of 1993 at NASA Goddard Space Flight Center. Recent observations from Yohkoh and the Compton Gamma Ray Observatory, and a reanalysis of older observations from the Solar Maximum Mission, have led to

James A. Miller; Peter J. Cargill; A. Gordon Emslie; Gordon D. Holman; Brian R. Dennis; Ted N. La Rosa; Robert M. Winglee; Stephen G. Benka; S. Tsuneta

1997-01-01

418

Investigations of turbulent motions and particle acceleration in solar flares  

NASA Technical Reports Server (NTRS)

Investigations of X-raya spectra of solar flares show that intense random (turbulent) motions are present in hot flare plasma. Here it is argued that the turbulent motions are of great importance for flare development. They can efficiently enhance flare energy release and accelerate particles to high energies.

Jakimiec, J.; Fludra, A.; Lemen, J. R.; Dennis, B. R.; Sylwester, J.

1986-01-01

419

Correcting the beam centroid motion in an induction accelerator and reducing the beam breakup instability  

NASA Astrophysics Data System (ADS)

Axial beam centroid and beam breakup (BBU) measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, ???, of 19% and a reduction in the BBU growth rate (?) of 4% by reducing beam centroid misalignments ˜50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.

Coleman, J. E.; Ekdahl, C. A.; Moir, D. C.; Sullivan, G. W.; Crawford, M. T.

2014-09-01

420

Concentrated ion beam emitted from an enlarged cylindrical-anode-layer Hall plasma accelerator and mechanism  

SciTech Connect

An enlarged cylindrical-anode-layer Hall plasma accelerator with an outlet diameter of 150 mm is experimentally demonstrated to produce a concentrated ion beam, especially at a high discharge voltage, with a high current utilization efficiency of up to {approx}0.9. Numerical investigation based on the three-dimensional particle-in-cell method is performed to study the ion dynamics and elucidate the origin of the ion beam characteristics. The simulation results reveal that the equipotential lines play an important role in the surface near the anode emitting the ions. The ion emitting surface is determined by the magnetic field lines near the anode and the magnetic mirror contributes to the concentrated beam significantly. The high current utilization efficiency results from the appropriate obliquity of the magnetic mirror.

Geng, S. F.; Wang, C. X. [Southwestern Institute of Physics, Chengdu 610041 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Tang, D. L.; Qiu, X. M. [Southwestern Institute of Physics, Chengdu 610041 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

2013-01-28

421

Signatures of particle acceleration at SN 1987A  

NASA Technical Reports Server (NTRS)

At least eight experiments are currently monitoring SN 1987A for photons or neutrinos with energies in the TeV range or higher. Observation of such signals would indicate that the supernova is the site of acceleration of charged particles to even higher energies. The way that the acceleration might occur is discussed, and the prospects for detection of such signals in light of current limits on power in the supernova from sources other than the nickel-cobalt-iron decay chain are evaluated. It is pointed out that signals of particle acceleration may show up in continuum MeV gamma rays as well as in the 100 MeV range.

Gaisser, T. K.; Stanev, Todor; Harding, Alice K.

1989-01-01

422

Development of a He- and He0 beam source for alpha particle measurement in a burning plasma.  

PubMed

Proof of principle experiments of neutral helium beam production for alpha particle diagnostics was carried out on a test stand. Negative helium ions were produced in the Li charge exchange cell, in which stable and long time operation was possible. He(-) beam was accelerated to 157 keV. Finally, He(0) beam was successfully produced after the flight in the drift-tube through the auto-electron-detachment process from He(-) to He(0). A neutral beam detector using a pyroelectric device