Manufacturing and Testing of Accelerator Superconducting Magnets

International Nuclear Information System (INIS)

Rossi, L

2014-01-01

Manufacturing of superconducting magnet for accelerators is a quite complex process that is not yet fully industrialized. In this paper, after a short history of the evolution of the magnet design and construction, we review the main characteristics of the accelerator magnets having an impact on the construction technology. We put in evidence how the design and component quality impact on construction and why the final product calls for a total-quality approach. LHC experience is widely discussed and main lessons are spelled out. Then the new Nb3Sn technology, under development for the next generation magnet construction, is outlined. Finally, we briefly review the testing procedure of accelerator superconducting magnets, underlining the close connection with the design validation and with the manufacturing process

Manufacturing and Testing of Accelerator Superconducting Magnets

Energy Technology Data Exchange (ETDEWEB)

Rossi, L [European Organization for Nuclear Research, Geneva (Switzerland)

2014-07-01

Manufacturing of superconducting magnet for accelerators is a quite complex process that is not yet fully industrialized. In this paper, after a short history of the evolution of the magnet design and construction, we review the main characteristics of the accelerator magnets having an impact on the construction technology. We put in evidence how the design and component quality impact on construction and why the final product calls for a total-quality approach. LHC experience is widely discussed and main lessons are spelled out. Then the new Nb3Sn technology, under development for the next generation magnet construction, is outlined. Finally, we briefly review the testing procedure of accelerator superconducting magnets, underlining the close connection with the design validation and with the manufacturing process.

Accelerated cardiovascular magnetic resonance of the mouse heart using self-gated parallel imaging strategies does not compromise accuracy of structural and functional measures

Directory of Open Access Journals (Sweden)

Dörries Carola

2010-07-01

Full Text Available Abstract Background Self-gated dynamic cardiovascular magnetic resonance (CMR enables non-invasive visualization of the heart and accurate assessment of cardiac function in mouse models of human disease. However, self-gated CMR requires the acquisition of large datasets to ensure accurate and artifact-free reconstruction of cardiac cines and is therefore hampered by long acquisition times putting high demands on the physiological stability of the animal. For this reason, we evaluated the feasibility of accelerating the data collection using the parallel imaging technique SENSE with respect to both anatomical definition and cardiac function quantification. Results Findings obtained from accelerated data sets were compared to fully sampled reference data. Our results revealed only minor differences in image quality of short- and long-axis cardiac cines: small anatomical structures (papillary muscles and the aortic valve and left-ventricular (LV remodeling after myocardial infarction (MI were accurately detected even for 3-fold accelerated data acquisition using a four-element phased array coil. Quantitative analysis of LV cardiac function (end-diastolic volume (EDV, end-systolic volume (ESV, stroke volume (SV, ejection fraction (EF and LV mass in healthy and infarcted animals revealed no substantial deviations from reference (fully sampled data for all investigated acceleration factors with deviations ranging from 2% to 6% in healthy animals and from 2% to 8% in infarcted mice for the highest acceleration factor of 3.0. CNR calculations performed between LV myocardial wall and LV cavity revealed a maximum CNR decrease of 50% for the 3-fold accelerated data acquisition when compared to the fully-sampled acquisition. Conclusions We have demonstrated the feasibility of accelerated self-gated retrospective CMR in mice using the parallel imaging technique SENSE. The proposed method led to considerably reduced acquisition times, while preserving high

Ablation acceleration of macroparticle in spiral magnetic fields

International Nuclear Information System (INIS)

Ikuta, Kazunari.

1981-05-01

The rocket motion of macroparticles heated by energetic pulses in a spiral magnetic field was studied. The purpose of the present work is to study the ablation acceleration of a macroparticle in a spiral magnetic field with the help of the law of conservation of angular momentum. The basic equation of motion of ablatively accelerated projectile in a spiral magnetic field was derived. Any rocket which is ejecting fully ionized plasma in an intense magnetic field with rotational transform is able to have spin by the law of conservation of momentum. The effect of spiral magnetic field on macroparticle acceleration is discussed. The necessary mass ratio increase exponentially with respect to the field parameter. The spiral field should be employed with care to have only to stabilize the position of macroparticles. As conclusion, it can be said that the ablation acceleration of the projectile in a spiral field can give the accelerated body spin quite easily. (Kato, T.)

Argonne lectures on particles accelerator magnets

International Nuclear Information System (INIS)

Devred, A.

1999-09-01

The quest for elementary particles has promoted the development of particle accelerators producing beams of increasingly higher energies. In a synchrotron, the particle energy is directly proportional to the product of the machine's radius times the bending magnets' field strength. Present proton experiments at the TeV scale require facilities with circumferences ranging from a few to tens of kilometers and relying on a large number (several hundred to several thousand) high field dipole magnets and high field gradient quadrupole magnets. These electro-magnets use high-current-density, low-critical-temperature superconducting cables and are cooled down at liquid helium temperature. They are among the most costly and the most challenging components of the machine. After explaining what are the various types of accelerator magnets and why they are needed (lecture 1), we briefly recall the origins of superconductivity and we review the parameters of existing superconducting particle accelerators (lecture 2). Then, we review the superconducting materials that are available at industrial scale (chiefly, NbTi and Nb 3 Sn) and we explain in details the manufacturing of NbTi wires and cables (lecture 3). We also present the difficulties of processing and insulating Nb 3 Sn conductors, which so far have limited the use of this material in spite of its superior performances. We continue by discussing the two dimensional current distributions which are the most appropriate for generating pure dipole and quadrupole fields and we explain how these ideal distributions can be approximated by so called cosθ and cos 2θ coil designs (lecture 4). We also present a few alternative designs which are being investigated and we describe the difficulties of realizing coil ends. Next, we present the mechanical design concepts that are used in existing accelerator magnets (lecture 5) and we describe how the magnets are assembled (lecture 6). Some of the toughest requirements on the

Argonne lectures on particles accelerator magnets

Energy Technology Data Exchange (ETDEWEB)

Devred, A

1999-09-01

The quest for elementary particles has promoted the development of particle accelerators producing beams of increasingly higher energies. In a synchrotron, the particle energy is directly proportional to the product of the machine's radius times the bending magnets' field strength. Present proton experiments at the TeV scale require facilities with circumferences ranging from a few to tens of kilometers and relying on a large number (several hundred to several thousand) high field dipole magnets and high field gradient quadrupole magnets. These electro-magnets use high-current-density, low-critical-temperature superconducting cables and are cooled down at liquid helium temperature. They are among the most costly and the most challenging components of the machine. After explaining what are the various types of accelerator magnets and why they are needed (lecture 1), we briefly recall the origins of superconductivity and we review the parameters of existing superconducting particle accelerators (lecture 2). Then, we review the superconducting materials that are available at industrial scale (chiefly, NbTi and Nb{sub 3}Sn) and we explain in details the manufacturing of NbTi wires and cables (lecture 3). We also present the difficulties of processing and insulating Nb{sub 3}Sn conductors, which so far have limited the use of this material in spite of its superior performances. We continue by discussing the two dimensional current distributions which are the most appropriate for generating pure dipole and quadrupole fields and we explain how these ideal distributions can be approximated by so called cos{theta} and cos 2{theta} coil designs (lecture 4). We also present a few alternative designs which are being investigated and we describe the difficulties of realizing coil ends. Next, we present the mechanical design concepts that are used in existing accelerator magnets (lecture 5) and we describe how the magnets are assembled (lecture 6). Some of the toughest

Post-LHC accelerator magnets

International Nuclear Information System (INIS)

Gourlay, Stephen A.

2001-01-01

The design and practicality of future accelerators, such as hadron colliders and neutrino factories being considered to supercede the LHC, will depend greatly on the choice of superconducting magnets. Various possibilities will be reviewed and discussed, taking into account recent progress and projected improvements in magnet design and conductor development along with the recommendations from the 2001 Snowmass workshop

Clinical applications of cardiovascular magnetic resonance imaging

International Nuclear Information System (INIS)

Marcu, C.B.; Beek, A.M.; Van Rossum, A.C.

2006-01-01

Cardiovascular magnetic resonance imaging (MRI) has evolved from an effective research tool into a clinically proven, safe and comprehensive imaging modality. It provides anatomic and functional information in acquired and congenital heart disease and is the most precise technique for quantification of ventricular volumes, function and mass. Owing to its excellent interstudy reproducibility, cardiovascular MRI is the optimal method for assessment of changes in ventricular parameters after therapeutic intervention. Delayed contrast enhancement is an accurate and robust method used in the diagnosis of ischemic and nonischemic cardiomyopathies and less common diseases, such as cardiac sarcoidosis and myocarditis. First-pass magnetic contrast myocardial perfusion is becoming an alternative to radionuclide techniques for the detection of coronary atherosclerotic disease. In this review we outline the techniques used in cardiovascular MRI and discuss the most common clinical applications. (author)

Particle Acceleration, Magnetic Field Generation in Relativistic Shocks

Science.gov (United States)

Nishikawa, Ken-Ichi; Hardee, P.; Hededal, C. B.; Richardson, G.; Sol, H.; Preece, R.; Fishman, G. J.

2005-01-01

Shock acceleration is an 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 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

Nb3Sn accelerator magnet development around the world

Energy Technology Data Exchange (ETDEWEB)

Michael J. Lamm

2003-06-23

During the past 30 years superconducting magnet systems have enabled accelerators to achieve energies and luminosities that would have been impractical if not impossible with resistive magnets. By far, NbTi has been the preferred conductor for this application because of its ductility and insensitivity of Jc to mechanical strain. This is despite the fact that Nb{sub 3}Sn has a more favorable Jc vs. B dependence and can operate at much higher temperatures. Unfortunately, NbTi conductor is reaching the limit of it usefulness for high field applications. Despite incremental increases in Jc and operation at superfluid temperatures, magnets are limited to approximately a 10 T field. Improvements in conductor performance combined with future requirements for accelerator magnets to have bore fields greater than 10 T or operate in areas of large beam-induced heat loads now make Nb{sub 3}Sn look attractive. Thus, laboratories in several countries are actively engaged in programs to develop Nb{sub 3}Sn accelerator magnets for future accelerator applications. A summary of this important research activity is presented along with a brief history of Nb{sub 3}Sn accelerator magnet development and a discussion of requirements for future accelerator magnets.

Particle acceleration at a reconnecting magnetic separator

Science.gov (United States)

Threlfall, J.; Neukirch, T.; Parnell, C. E.; Eradat Oskoui, S.

2015-02-01

Context. 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. Aims: We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. Methods: We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. Results: 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 several free parameters, and we study the effect of changing these parameters upon particle acceleration, in particular in view of the final particle energy ranges that agree with observed energy spectra.

CAS CERN Accelerator School. Measurement and alignment of accelerator and detector magnets. Proceedings

International Nuclear Information System (INIS)

Turner, S.

1998-01-01

These proceedings present the lectures given at the eleventh specialised course organised by the CERN Accelerator School (CAS), the topic this time being 'Measurement and Alignment of Accelerator and Detector Magnets'. A similar course was already presented at Montreux, Switzerland in 1992 and its proceedings published as CERN 92-05. However recent progress in the field, especially in the use of superconducting magnets, has been so rapid that a revised course had become imperative. The lectures start with basic magnet theory and the motivation for magnet measurements followed by a review of superconducting magnets and their field dynamics. After a review of measurement methods, the details of search and harmonic coils, magnetic resonance techniques and Hall generators are given followed by methods to minimise errors in mechanical equipment, series production and detector magnet measurements. Turning to magnet metrology and alignment, first data quality control is explained followed by the setting of reference targets, and the alignment methods for accelerators and experiments including alignment by feedback. Finally seminars are presented on the biological effects of magnetic fields and on superconducting magnet fabrication and quality control. (orig.)

Superconducting magnets for accelerators

International Nuclear Information System (INIS)

Denisov, Yu.N.

1979-01-01

Expediency of usage and possibilities arising in application of superconducting devices in magnetic systems of accelerators and experimental nuclear-physical devices are studied. Parameters of specific devices are given. It is emphasized that at the existing level of technological possibilities, construction and usage of superconducting magnetic systems in experimental nuclear physics should be thought of as possible, from the engineering, and expedient, from the economical viewpoints [ru

Magnetic resonance imaging of the cardiovascular system

International Nuclear Information System (INIS)

Masuda, Yoshiaki; Imai, Hiroshi; Watanabe, Sigeru; Inagaki, Yoshiaki; Tateno, Yukio; Ikehira, Hiroo.

1990-01-01

Magnetic resonance imaging (MRI) is a new noninvasive technique for visualization of the cardiovascular system, and is used to evaluate tissue characteristics, cardiac function and blood flow abnormalities, as well as to obtain morphological information. In this paper we presented results of clinical and laboratory research obtained using conventional spin echo MRI with regard to cardiovascular anatomy, tissue characterization and physiology. Furthermore, experience with two new techniques, cine-MRI and volume-selected MR spectroscopy, and their potential clinical usefulness in detecting cardiovascular diseases are documented. (author)

Particle acceleration in relativistic magnetic flux-merging events

Science.gov (United States)

Lyutikov, Maxim; Sironi, Lorenzo; Komissarov, Serguei S.; Porth, Oliver

2017-12-01

Using analytical and numerical methods (fluid and particle-in-cell simulations) we study a number of model problems involving merger of magnetic flux tubes in relativistic magnetically dominated plasma. Mergers of current-carrying flux tubes (exemplified by the two-dimensional `ABC' structures) and zero-total-current magnetic flux tubes are considered. In all cases regimes of spontaneous and driven evolution are investigated. We identify two stages of particle acceleration during flux mergers: (i) fast explosive prompt X-point collapse and (ii) ensuing island merger. The fastest acceleration occurs during the initial catastrophic X-point collapse, with the reconnection electric field of the order of the magnetic field. During the X-point collapse, particles are accelerated by charge-starved electric fields, which can reach (and even exceed) values of the local magnetic field. The explosive stage of reconnection produces non-thermal power-law tails with slopes that depend on the average magnetization . For plasma magnetization 2$ the spectrum power-law index is 2$ ; in this case the maximal energy depends linearly on the size of the reconnecting islands. For higher magnetization, 2$ , the spectra are hard, , yet the maximal energy \\text{max}$ can still exceed the average magnetic energy per particle, , by orders of magnitude (if is not too close to unity). The X-point collapse stage is followed by magnetic island merger that dissipates a large fraction of the initial magnetic energy in a regime of forced magnetic reconnection, further accelerating the particles, but proceeds at a slower reconnection rate.

Technology of magnetically driven accelerators

International Nuclear Information System (INIS)

Brix, D.L.; Hawkins, S.A.; Poor, S.E.; Reginato, L.L.; Smith, M.W.

1985-01-01

The marriage of Induction Linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 MeV/meter, and with power efficiencies approaching 50%. A 2 MeV, 5 kA electron accelerator has been constructed at the Lawrence Livermore National Laboratory (LLNL) to demonstrate these concepts and to provide a test facility for high brightness sources. The pulse drive for the accelerator is based on state-of-the-art magnetic pulse compressors with very high peak power capability, repetition rates exceeding a kilohertz and excellent reliability

Technology of magnetically driven accelerators

International Nuclear Information System (INIS)

Birx, D.L.; Hawkins, S.A.; Poor, S.E.; Reginato, L.L.; Smith, M.W.

1985-01-01

The marriage of Induction Linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 MeV/meter, and with power efficiencies approach 50%. A 2 MeV, 5 kA electron accelerator has been constructed at the Lawrence Livermore National Laboratory (LLNL) to demonstrate these concepts and to provide a test facility for high brightness sources. The pulse drive for the accelerator is based on state-of-the-art magnetic pulse compressors with very high peak power capability, repetition rates exceeding a kilohertz and excellent reliability

High-Field Accelerator Magnets

International Nuclear Information System (INIS)

Rijk, G de

2014-01-01

In this lecture an overview is given of the present technology for high field accelerator magnets. We indicate how to get high fields and what are the most important parameters. The available conductors and their limitations are presented followed by the most relevant types of coils and support structures. We conclude by showing a number of recent examples of development magnets which are either pure R&D objects or models for the LHC luminosity upgrade

Hysteresis effects in the cores of particle accelerator magnets

CERN Document Server

AUTHOR|(CDS)2086181; Schoerling, Daniel

A study of the hysteresis effects in the cores of particle accelerator magnets has been performed in the framework of the work presented in this thesis. This study has been focused on normal conducting particle accelerator magnets whose cores are manufactured using ferromagnetic materials. The magnetic circuits have been modelled using the developed models: one model for the magnetic circuit and one for the magnetization of the material in the core. The parameters of the magnetic circuit model have been identified with the help of simulations which rely on the finite element method (Opera 3D), while the parameters of the magnetic hysteresis model have been identified through experimental measurements performed using a method developed in the framework of this work. The modelling results have been validated by means of experimental measurements performed on two magnets: one small size magnet which has been specifically designed and manufactured, and one magnet which is currently used in a particle accelerator ...

Recent status of superconductors for accelerator magnets

International Nuclear Information System (INIS)

Greene, A.F.

1992-01-01

A survey is given of superconductor wire and cable which has been or will be used for construction of dipole magnets for all of the large European and US superconducting accelerator rings. Included is a simplified view of the construction methods and operating requirements of an accelerator dipole magnet, with emphasis on required superconductor performance. The methods of fabricating Nb-Ti superconductors are described, including the critical parameters and materials requirements. The superconductor performance requirements are summarized in an effort to relate why these are important to accelerator designers. Some of the recently observed time dependent effects are covered briefly

CERN-LHC accelerator superconducting magnet. Development and international cooperation

International Nuclear Information System (INIS)

Yamamoto, Akira; Nakamoto, Tatsushi; Sasaki, Ken-ichi

2009-01-01

CERN-LHC accelerator superconducting magnets and a cooperative work for interaction region quadrupole magnets are introduced. The accelerator commissioning and the incident happened during the commissioning in 2008 is also briefly discussed. (author)

Clinical advances in cardiovascular magnetic resonace imaging and angiography

NARCIS (Netherlands)

Bosch, van den H.C.M.

2018-01-01

Cardiovascular magnetic resonance imaging is an important noninvasive imaging modality for the diagnosis, clinical work‐up and treatment planning in patients suspected for a wide range of cardiovascular pathology. CMR imaging is accurate and reliable, and provides invaluable information to evaluate

Feedback between Accelerator Physicists and magnet builders

International Nuclear Information System (INIS)

Peggs, S.

1995-01-01

Our task is not to record history but to change it. (K. Marx (paraphrased)) How should Accelerator Physicists set magnet error specifications? In a crude social model, they place tolerance limits on undesirable nonlinearities and errors (higher order harmonics, component alignments, etc.). The Magnet Division then goes away for a suitably lengthy period of time, and comes back with a working magnet prototype that is reproduced in industry. A better solution is to set no specifications. Accelerator Physicists begin by evaluating expected values of harmonics, generated by the Magnet Division, before and during prototype construction. Damaging harmonics are traded off against innocuous harmonics as the prototype design evolves, lagging one generation behind the evolution of expected harmonics. Finally, the real harmonics are quickly evaluated during early industrial production, allowing a final round of performance trade-offs, using contingency scenarios prepared earlier. This solution assumes a close relationship and rapid feedback between the Accelerator Physicists and the magnet builders. What follows is one perspective of the way that rapid feedback was used to 'change history' (improve linear and dynamic aperture) at RHIC, to great benefit

The overview and history of permanent magnet devices in accelerator technology

International Nuclear Information System (INIS)

Kraus, R.H.

1994-01-01

This paper looks at the early history of accelerator development with a particular focus on the important discoveries that opened the door for the application of permanent-magnet materials to this area of science. Researchers began to use permanent-magnet materials in particle accelerators soon after the invention of the alternating gradient principle, that showed magnetic fields could be used to control the transverse envelope of charged-particle beams. Since that time, permanent-magnet materials have found wide application in the modern charged particle accelerator. A brief history of permanent-magnet use in accelerator physics and technology is outlined, some of the general design considerations are presented, and several material properties of concern for particle accelerator applications are discussed

The overview and history of permanent magnet devices in accelerator technology

International Nuclear Information System (INIS)

Kraus, R.H. Jr.

1993-01-01

This paper reviews the early history of accelerator development with a particular focus on the important discoveries that opened the door for the application of permanent-magnet materials to this area of science. Researchers began to use permanent-magnet materials in particle accelerators soon after the invention of the alternating gradient principle, that showed magnetic fields could be used to control the transverse envelope of charged-particle beams. Since that time, permanent-magnet materials have found wide application in the modern charged particle accelerator. The history of permanent-magnet use in accelerator physics and technology is outlined, general design considerations are presented, and material properties of concern for particle accelerator applications are discussed

Mechanical Design of Superconducting Accelerator Magnets

International Nuclear Information System (INIS)

Toral, F

2014-01-01

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques

Mechanical Design of Superconducting Accelerator Magnets

CERN Document Server

Toral, Fernando

2014-07-17

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques.

Mechanical Design of Superconducting Accelerator Magnets

Energy Technology Data Exchange (ETDEWEB)

Toral, F [Madrid, CIEMAT (Spain)

2014-07-01

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques.

Specifications, quality control, manufacturing, and testing of accelerator magnets

CERN Document Server

Einfeld, D

2010-01-01

The performance of the magnets plays an important role in the functioning of an accelerator. Most of the magnets are designed at the accelerator laboratory and built by industry. The link between the laboratory and the manufacturer is the contract containing the Technical Specifications of the magnets. For an overview of the contents of the Technical Specifications, the specifications for the magnets of ALBA (bending, quadrupole, and sextupole) are described in this paper. The basic rules of magnet design are reviewed in Appendix A.

Plasma cluster acceleration by means of external magnetic fields

International Nuclear Information System (INIS)

Kracik, J.; Maloch, J.; Sobra, K.

1975-01-01

The electromagnetic shock tubes are used not only for shock wave creation and study but also for pulse plasma acceleration. By applying the rail acceleration the external magnetic field perpendicular to the plasma cluster velocity can be increased. In the present work is theoretically and experimentally confirmed the external magnetic field influence on the plasma cluster acceleration when the 'snow plough' model is used. (Auth.)

Fermilab's SC Accelerator Magnet Program for Future U.S. HEP Facilities

International Nuclear Information System (INIS)

Lamm, Michael; Zlobin, Alexander

2010-01-01

The invention of SC accelerator magnets in the 1970s opened wide the possibilities for advancing the energy frontier of particle accelerators, while limiting the machine circumference and reducing their energy consumption. The successful development of SC accelerator magnets based on NbTi superconductor have made possible a proton-antiproton collider (Tevatron) at Fermilab, an electron-proton collider (HERA) at DESY, a relativistic heavy ion collider (RHIC) at BNL and recently a proton-proton collider (LHC) at CERN. Further technological innovations and inventions are required as the US HEP looks forward towards the post-LHC energy or/and intensity frontiers. A strong, goal oriented national SC accelerator magnet program must take on this challenge to provide a strong base for the future of HEP in the U.S. The results and experience obtained by Fermilab during the past 30 years will allow us to play a leadership role in the SC accelerator magnet development in the U.S., in particular, focusing on magnets for a Muon Collider/Neutrino Factory (1)-(2). In this paper, we summarize the required Muon Collider magnet needs and challenges, summarize the technology advances in the Fermilab accelerator magnet development over the past few years, and present and discuss our vision and long-term plans for these Fermilab-supported accelerator initiatives.

Virtual reality visualization of accelerator magnets

International Nuclear Information System (INIS)

Huang, M.; Papka, M.; DeFanti, T.; Kettunen, L.

1995-01-01

The authors describe the use of the CAVE virtual reality visualization environment as an aid to the design of accelerator magnets. They have modeled an elliptical multipole wiggler magnet being designed for use at the Advanced Photon Source at Argonne National Laboratory. The CAVE environment allows the authors to explore and interact with the 3-D visualization of the magnet. Capabilities include changing the number of periods the magnet displayed, changing the icons used for displaying the magnetic field, and changing the current in the electromagnet and observing the effect on the magnetic field and particle beam trajectory through the field

Application of permanent magnets in accelerators and electron storage rings

International Nuclear Information System (INIS)

Halbach, K.

1984-09-01

After an explanation of the general circumstances in which the use of permanent magnets in accelerators is desirable, a number of specific magnets will be discussed. That discussion includes magnets needed for the operation of accelerators as well as magnets that are employed for the utilization of charged particle beams, such as the production of synchrotron radiation. 15 references, 8 figures

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Shocks

Science.gov (United States)

Nishikawa, Ken-IchiI.; Hededal, C.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G.

2004-01-01

Shock acceleration is an 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 3-D relativistic electromagnetic particle (m) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

Properties of the superconductor in accelerator dipole magnets

Science.gov (United States)

Teravest, Derk

Several aspects of the application of superconductors to high field dipole magnets for particle accelerators are discussed. The attention is focused on the 10 tesla (1 m model) magnet that is envisaged for the future Large Hadron Collider (LHC) accelerator. The basic motivation behind the study is the intention of employing superconductors to their utmost performance. An overview of practical supercomputers, their applications and their impact on high field dipole magnets used for particle accelerators, is presented. The LHC reference design for the dipole magnets is outlined. Several models were used to study the influence of a number of factors in the shape and in particular, the deviation from the shape that is due to the flux flow state. For the investigated extrinsic and intrinsic factors, a classification can be made with respect to the effect on the shape of the characteristic of a multifilamentary wire. The optimization of the coil structure for high field dipole magnets, with respect to the field quality is described. An analytical model for solid and hollow filaments, to calculate the effect of filament magnetization in the quality of the dipole field, is presented.

Simple motion correction strategy reduces respiratory-induced motion artifacts for k-t accelerated and compressed-sensing cardiovascular magnetic resonance perfusion imaging.

Science.gov (United States)

Zhou, Ruixi; Huang, Wei; Yang, Yang; Chen, Xiao; Weller, Daniel S; Kramer, Christopher M; Kozerke, Sebastian; Salerno, Michael

2018-02-01

Cardiovascular magnetic resonance (CMR) stress perfusion imaging provides important diagnostic and prognostic information in coronary artery disease (CAD). Current clinical sequences have limited temporal and/or spatial resolution, and incomplete heart coverage. Techniques such as k-t principal component analysis (PCA) or k-t sparcity and low rank structure (SLR), which rely on the high degree of spatiotemporal correlation in first-pass perfusion data, can significantly accelerate image acquisition mitigating these problems. However, in the presence of respiratory motion, these techniques can suffer from significant degradation of image quality. A number of techniques based on non-rigid registration have been developed. However, to first approximation, breathing motion predominantly results in rigid motion of the heart. To this end, a simple robust motion correction strategy is proposed for k-t accelerated and compressed sensing (CS) perfusion imaging. A simple respiratory motion compensation (MC) strategy for k-t accelerated and compressed-sensing CMR perfusion imaging to selectively correct respiratory motion of the heart was implemented based on linear k-space phase shifts derived from rigid motion registration of a region-of-interest (ROI) encompassing the heart. A variable density Poisson disk acquisition strategy was used to minimize coherent aliasing in the presence of respiratory motion, and images were reconstructed using k-t PCA and k-t SLR with or without motion correction. The strategy was evaluated in a CMR-extended cardiac torso digital (XCAT) phantom and in prospectively acquired first-pass perfusion studies in 12 subjects undergoing clinically ordered CMR studies. Phantom studies were assessed using the Structural Similarity Index (SSIM) and Root Mean Square Error (RMSE). In patient studies, image quality was scored in a blinded fashion by two experienced cardiologists. In the phantom experiments, images reconstructed with the MC strategy had higher

Magnetic resonance imaging in cardiovascular disease

International Nuclear Information System (INIS)

Eckel, C.G.; Mettler, F.A. Jr.; Wicks, J.D.; Stevens, G.F.

1986-01-01

How does magnetic resonance imaging (MRI) currently contribute in the evaluation of patients with suspected heart disease? What role will MRI play in the future in evaluation of cardiovascular disease? To understand better where MRI fits into the diagnostic algorithm of cardiovascular disease the authors first consider the characteristics that they would like to see in the ideal diagnostic test and then survey the available cardiac diagnostic tests to note the characteristics that limit or recommend a test. In the final analysis, the justification for expensive diagnostic tests such as MRI must be an overall improvement in survival or quality of life in those patients treated after diagnosis

Superconducting magnet technology for particle accelerators and detectors seminar

CERN Multimedia

CERN. Geneva

2006-01-01

This lecture is an introduction to superconducting magnets for particle accelerators and detectors, the aim being to explain the vocabulary and describe the basic technology of modern superconducting magnets, and to explore the limits of the technology. It will include the following: - Why we need superconducting magnets - Properties of superconductors, critical field, critical temperature - Why accelerators need fine filaments and cables; conductor manufacture - Temperature rise and temperature margin: the quench process, training - Quench protection schemes. Protection in the case of the LHC. - Magnets for detectors - The challenges of state-of-the-art magnets for High Energy Physics

Magnetic field measurements of superconducting magnets for the colliding beam accelerator

International Nuclear Information System (INIS)

Herrera, J.; Kirk, H.; Prodell, A.; Willen, E.

1983-01-01

An important aspect of the development and production of superconducting magnets for the Colliding Beam Accelerator is the measurement of the magnetic field in the aperture of these magnets. The measurements have the three-fold purpose of determining the field quality as compared to the lattice requirements of the CBA, of obtaining the survey data necessary to position the magnets in the CBA tunnel, and lastly, of characterizing the magnetic fields for use in initial and future orbit studies of the CBA proton beams. Since for a superconducting storage accelerator it is necessary to carry out these detailed measurements on many (approx. 1000) magnets and at many current values (approx. 1000), we have chosen, in agreement with previous experience, to develop a system which Fourier analyses the voltages induced in a number of rotating windings and thereby obtains the multipole field components. The important point is that such a measuring system can be fast and precise. It has been used for horizontal measurements of the CBA ring dipoles

Rarefaction acceleration of ultrarelativistic magnetized jets in gamma-ray burst sources

Science.gov (United States)

Komissarov, Serguei S.; Vlahakis, Nektarios; Königl, Arieh

2010-09-01

When a magnetically dominated superfast-magnetosonic long/soft gamma-ray burst (GRB) jet leaves the progenitor star, the external pressure support will drop and the jet may enter the regime of ballistic expansion, during which additional magnetic acceleration becomes ineffective. However, recent numerical simulations by Tchekhovskoy et al. have suggested that the transition to this regime is accompanied by a spurt of acceleration. We confirm this finding numerically and attribute the acceleration to a sideways expansion of the jet, associated with a strong magnetosonic rarefaction wave that is driven into the jet when it loses pressure support, which induces a conversion of magnetic energy into kinetic energy of bulk motion. This mechanism, which we dub rarefaction acceleration, can only operate in a relativistic outflow because in this case the total energy can still be dominated by the magnetic component even in the superfast-magnetosonic regime. We analyse this process using the equations of relativistic magnetohydrodynamics and demonstrate that it is more efficient at converting internal energy into kinetic energy when the flow is magnetized than in a purely hydrodynamic outflow, as was found numerically by Mizuno et al. We show that, just as in the case of the magnetic acceleration of a collimating jet that is confined by an external pressure distribution - the collimation-acceleration mechanism - the rarefaction-acceleration process in a magnetized jet is a consequence of the fact that the separation between neighbouring magnetic flux surfaces increases faster than their cylindrical radius. However, whereas in the case of effective collimation-acceleration the product of the jet opening angle and its Lorentz factor does not exceed ~1, the addition of the rarefaction-acceleration mechanism makes it possible for this product to become >>1, in agreement with the inference from late-time panchromatic breaks in the afterglow light curves of long/soft GRBs.

High temperature superconductor accelerator magnets

NARCIS (Netherlands)

van Nugteren, J.

2016-01-01

For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

Compact and energy saving magnet technology for particle accelerators

International Nuclear Information System (INIS)

Baurichter, A.

2013-01-01

Despite the fact that funding agencies and industrial users of particle accelerators get more and more alerted about costs of civil engineering, installation and operation, only little effort has been put into development of sustainable, energy and cost saving accelerator technology. In order to reduce the total-cost-of ownership of accelerator magnets, operating at high electrical power for twenty years or more, permanent magnet based Green Magnet technology has been developed at a consortium around Danfysik's R and D team. Together with our partners from ISA, Aarhus University, the Aarhus School of Engineering, the company Sintex and Aalborg University all obstacles in applying permanent magnet technology as e.g. thermal drift and inhomogeneities of magnetic fields have been overcome. The first Green Magnet has now been operated for more than half a year in an Accelerator Mass Spectrometry facility at the ETH in Zurich. The performance of this B=0.43T 90 deg. H-type bending magnet and the most recently builtB=1T, 30 deg. C-type Green Magnet for the synchrotron light source ASTRID2 at ISA in Aarhus will be presented. Danfysik also is designing, manufacturing and testing 60 compact magnet systems, developed at MAX-Lab for the new MAXIV 3.0 GeV synchrotron light source. In addition, 12 for the 1.5 GeV light source and another 12 for the new SOLARIS light source in Krakow, Poland are buying built. Up to a dozen or more magnet functions have been integrated into one yoke of these compact magnet systems, which makes the new MAXIV light sources compact, energy saving and at the same time very bright. Test results and design concepts of the new MAXIV and SOLARIS magnets will be presented. (author)

Concepts and limitations of macroparticle accelerators using travelling magnetic waves

International Nuclear Information System (INIS)

Wipf, S.L.

1980-01-01

The concept of an accelerator using a travelling magnetic wave acting on magnetized projectiles is discussed. Although superconductors have a high potential as projectile material, their low critical temperature makes them unsuitable. Among ferromagnetic materials dysprosium seems to be superior. For stable suspension and guidance a high conductivity, preferably superconducting, guide sheet is necessary. Magnetic field gradients of 10 9 A/m 2 travelling at 10 6 m/s should be achievable using present state-of-the-art components; resulting accelerations are greater than or equal to 500 km/s 2 . A linear accelerator for final speeds of 50 km/s needs a length of 2.5 km. Guidance forces sufficient to produce acceleration of 2 x 10 6 m/s 2 allow circular accelerators of reasonable size to achieve hypervelocities for small (50 to 100 mg) projectiles. An accelerator of 170 m diameter would surpass the best results from light gas guns. Travelling waves suitable for accelerations of the order of 10 4 m/s 2 can be produced without switching, by means of flux displacing rotors, easily adapted to circular accelerators

Magnetization, critical current, and injection field harmonics in superconducting accelerator magnets

International Nuclear Information System (INIS)

Ghosh, A.K.; Sampson, W.B.; Wanderer, P.

1985-01-01

The very large energy ratio of machines such as the SSC dictates rather low injection field (for 6T, 20 TeV it is approximately 0.3T). Since the harmonic content at such low fields is largely determined by magnetization currents in the superconductor, the random errors depend on the uniformity of the superconducting wire. In principle the magnitude of the residual fields can be reduced indefinitely by using finer filaments, but in practice there is a lower limit of a few microns. We have compared the injection field harmonics for a number of accelerator dipoles with magnetization measurements made on samples of the conductor used to wind the coils. In addition both the magnetization and harmonics have been compared with short sample critical current measurements made at 5T. The results indicated that an accurate estimate of the variation in injection field harmonics can only be obtained from direct measurements of the magnetization of the cable. It appears feasible to use such measurements to ''shuffle'' magnets for a large accelerator by predicting the low field properties of a magnet before actually winding the coils. 10 refs., 4 figs., 2 tabs

Workshop on Accelerator Magnet Superconductors, Design and Optimization

CERN Document Server

WAMSDO Workshop

2009-01-01

This report contains the proceedings of the CARE-HHH-AMT Workshop on Accelerator Magnet Superconductors, Design and Optimization (WAMSDO) held at CERN from 19 to 23 May 2008. The needs in terms of superconducting magnets for the accelerator projects were discussed, mainly for the LHC interaction regions and injector upgrades, and for the GSI FAIR complex. The first part of the workshop focused on the development of superconductor and cables, i.e., low-loss Nb-Ti cables, Nb$_{3}$Sn and high-temperature superconductors. An industry session summarized the actual plans and status of the activities in the main European industries. Then, a worldwide status of the high field magnets programme was presented. A special session was devoted to fast cycled magnets, including FAIR facilities and LHC injector upgrades. A final session focused on the optimization methods and numerical tools for magnet design.

Workshop on accelerator magnet superconductors. Proceedings

International Nuclear Information System (INIS)

2004-01-01

The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors

Workshop on accelerator magnet superconductors. Proceedings

Energy Technology Data Exchange (ETDEWEB)

NONE

2004-07-01

The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors.

Decay and snapback in superconducting accelerator magnets

NARCIS (Netherlands)

Haverkamp, M.

2003-01-01

This thesis deals with the explanation and compensation of the effects ‘decay’ and ‘snapback’ in superconducting accelerator magnets, in particular in those used in the new Large Hardron Collider at CERN. During periods of constant magnet excitation, as for example during the injection of particles

Design of digital logic control for accelerator magnet power supply

International Nuclear Information System (INIS)

Long Fengli; Hu Wei; Cheng Jian

2008-01-01

For the accelerator magnet power supply, usually the Programmable Logic Controller (PLC) is used to server as the controller for logic protection and control. Along with the development of modern accelerator technology, it is a trend to use fully-digital control to the magnet power supply. It is possible to integrate the logic control part into the digital control component of the power supply, for example, the Field Programmable Gate Array (FPGA). The paper introduces to different methods which are designed for the logic protection and control for accelerator magnet power supplies with the FPGA as the control component. (authors)

Turbulence, Magnetic Reconnection in Turbulent Fluids and Energetic Particle Acceleration

Science.gov (United States)

Lazarian, A.; Vlahos, L.; Kowal, G.; Yan, H.; Beresnyak, A.; de Gouveia Dal Pino, E. M.

2012-11-01

Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfvén, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets fast and we present numerical evidence supporting the predictions of the Lazarian and Vishniac (Astrophys. J. 517:700-718, 1999) model of fast reconnection. The efficiency of this process suggests that magnetic reconnection can release substantial amounts of energy in short periods of time. As the particle tracing numerical simulations show that the particles can be efficiently accelerated during the reconnection, we argue that the process of magnetic reconnection may be much more important for particle acceleration than it is currently accepted. In particular, we discuss the acceleration arising from reconnection as a possible origin of the anomalous cosmic rays measured by Voyagers as well as the origin cosmic ray excess in the direction of Heliotail.

Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate

International Nuclear Information System (INIS)

C.Z. Cheng; Y. Ren; G.S. Choe; Y.-J. Moon

2003-01-01

A physical mechanism of flares, in particular for the flare rise phase, has emerged from our 2-1/2-dimensional resistive MHD simulations. The dynamical evolution of current-sheet formation and magnetic reconnection and flux-rope acceleration subject to continuous, slow increase of magnetic shear in the arcade are studied by employing a non-uniform anomalous resistivity in the reconnecting current sheet under gravity. The simulation results directly relate the flux rope's accelerated rising motion with an enhanced magnetic reconnection rate and thus an enhanced reconnection electric field in the current sheet during the flare rise phase. The simulation results provide good quantitative agreements with observations of the acceleration of flux rope, which manifests in the form of SXR ejecta or erupting filament or CMEs, in the low corona. Moreover, for the X-class flare events studied in this paper the peak reconnection electric field is about O(10 2 V/m) or larger, enough to accelerate p articles to over 100 keV in a field-aligned distance of 10 km. Nonthermal electrons thus generated can produce hard X-rays, consistent with impulsive HXR emission observed during the flare rise phase

Superconducting materials for particle accelerator magnets

International Nuclear Information System (INIS)

Larbalestier, D.C.

1983-01-01

Present accelerator designs are clustered around a field of 5 Tesla with several future studies looking at the 8-to-10 Tesla range. There has also been some recent interest in low-field iron-dominated dipoles in which the superconductor will see a field of about 2 Tesla. The demands of this present range of interest can still be met, with the upper limit at about 10 Tesla, by the use of Nb-Ti (or Nb-Ti-Ta) or Nb 3 Sn. Both of these conductors are available in multifilamentary form from industrial sources and are suitable for accelerator magnets. The upper critical field and transition temperature of both types of composite cover the foreseeable range of demand for such magnets. There is no magical new composite on the horizon that is likely to replace Nb-Ti or Nb 3 Sn. One class of materials which has a potentially exciting prospect is that of the ternary molybdenum sulfides. These can have an upper critical field of greater than 50 T, which extends their superconductivity into field ranges unattainable with A15 compounds; the two drawbacks to such materials, however, are the amount of development needed to produce superconductors from them with useful current densities and the fact that it does not appear that they would offer any features not already possessed by Nb-Ti or Nb 3 Sn in the field range presently of interest to accelerator designers. Using this pragmatic approach, this paper addresses these and other superconducting composites in terms of their fabrication, their testing, the measurement aspects of their critical current densities, and other properties which are pertinent to their selection for particle accelerator magnet use

Magnetic linear accelerator (MAGLAC) for hypervelocity acceleration in impact fusion (IF)

International Nuclear Information System (INIS)

Chen, K.W.

1980-01-01

This paper presents considerations on the design of a magnetic linear accelerator suitable as driver for impact fusion. We argue that the proposed approach offers an attractive option to accelerate macroscopic matter to centiluminal velocity suitable for fusion applications. The design goal is to attain a velocity approaching 200 km/sec. Recent results in suitable target design suggest that a velocity in the range of 40-100 km/sec might be sufficient to include fusion. An accelerator in this velocity range can be constructed with current-day technology. We present both design and practical engineering considerations. Future work are outlined and recommended. (orig.)

Stripline magnetic modulators for lasers and accelerators

International Nuclear Information System (INIS)

Nunnally, W.C.

1981-01-01

The basics of magnetic modulators including magnetic element and circuit considerations as applied to accelerators and lasers requiring repetitive (1 to 10 kHz), high voltage (50 to 500 kV), short pulse (50 to 100 ns) are discussed. The scaling of energy losses and switching parameters with material are included

High-current power supply for accelerator magnets

International Nuclear Information System (INIS)

Bourkland, K.R.; Winje, R.A.

1978-01-01

A power supply for controlling the current to accelerator magnets produces a high current at a precisely controlled time rate of change by varying the resonant frequency of an RLC circuit that includes the magnet and applying the current to the magnet during a predetermined portion of the waveform of an oscillation. The current is kept from going negative despite the reverse-current characteristics of thyristors by a quenching circuit

NONTHERMALLY DOMINATED ELECTRON ACCELERATION DURING MAGNETIC RECONNECTION IN A LOW-β PLASMA

International Nuclear Information System (INIS)

Li, Xiaocan; Li, Gang; Guo, Fan; Li, Hui

2015-01-01

By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization. We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. The nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the  highly efficient electron acceleration in solar flares and other astrophysical systems

Correcting coils in end magnets of accelerators

Directory of Open Access Journals (Sweden)

L. R. P. Kassab

1998-05-01

Full Text Available We present an empirical investigation of the correcting coils behavior used to homogenize the field distribution of the race-track microtron accelerator end magnets. These end magnets belong to the second stage of the 30.0 MeV cw electron accelerator under construction at IFUSP, the race-track microtron booster, in which the beam energy is raised from 1.97 to 5.1 MeV. The correcting coils are attached to the pole faces and are based on the inhomogeneities of the magnetic field measured. The performance of these coils, when operating the end magnets with currents that differ by ±10% from the one used in the mappings that originated the coils copper leads, is presented. For one of the magnets, adjusting conveniently the current of the correcting coils makes it possible to homogenize field distributions of different intensities, once their shapes are practically identical to those that originated the coils. For the other one, the shapes are changed and the coils are less efficient. This is related to intrinsic factors that determine the inhomogeneities. However, we obtained uniformity of 0.001% in both cases.

CAS - CERN Accelerator School: Specialised course on Magnets

CERN Document Server

CAS 2009

2010-01-01

These proceedings present the lectures given at the twenty-third specialized course organized by the CERN Accelerator School (CAS), the topic being 'Magnets'. The course was held in Bruges, Belgium, from 16 to 25 June 2009. This is the first time this topic has been selected for a specialized course. Taking into account the number of related applications currently in use in accelerators around the world, but, even more important, the worrying decrease in the corresponding expertise in the different laboratories, it was recognized that such a topic should definitively be incorporated into the CAS series of specialized courses. The specific aim of the course was to introduce the participants to the basics of resistive magnet design and its underlying theoretical concepts. The first part of the school dealt with basic introductory courses such as Maxwell's equations for magnets, beam optics, physics and measurement of magnetic materials, the different types of resistive magnets and their respective performance, ...

Dipole-sheet multipole magnets for accelerators

International Nuclear Information System (INIS)

Walstrom, P.L.

1993-01-01

The dipole-sheet formalism can be used to describe both cylindrical current-sheet multipole magnets and cylindrical-bore magnets made up of permanent magnet blocks. For current sheets, the formalism provides a natural way of finding a finite set of turns that approximate a continuous distribution. The formalism is especially useful In accelerator applications where large-bore, short, high-field-quality magnets that are dominated by fringe fields are needed. A further advantage of the approach is that in systems with either open or cylindrically symmetric magnetic boundaries, analytical expressions for the three-dimensional fields that are suitable for rapid numerical evaluation can be derived. This development is described in some detail. Also, recent developments in higher-order particle-beam optics codes based on the formalism are described briefly

Eddy currents in accelerator magnets

CERN Document Server

Moritz, G

2010-01-01

This paper covers the main eddy current effects in accelerator magnets - field modification (time delay and field quality) and resistive power losses. In the first part, starting from the Maxwell equations, a basic understanding of the processes is given and explained with examples of simple geometry and time behaviour. Useful formulas are derived for an analytic estimate of the size of the effects. In the second part the effects in real magnets are analysed and described in comparison with numerical and measured results. Finally, based on the previous parts, design recommendations are given regarding how to minimize eddy current effects.

Development of the kicker magnet system for the IHEP accelerator

International Nuclear Information System (INIS)

Andreev, V.N.; Kurnaev, O.V.; Sychev, V.A.; Trofimov, Yu.D.

1982-01-01

The KM-14 kicker magnet intended for joint operation with the KM-16 kicker magnet in the U-70 accelerator fast beam extraction system is described. The main characteristics and specific features of the magnet, pulse generators and power supplies are considered. The total aperture type KM-14 magnet (aperture height is equal to 100 mm, its width amounts 150 mm) consists of four modules which are supplied in pair-parallel by two pulse generators. The length of each module is 0.56 m, the field in a gap amounts 0.045 Tl. Joint use of the KM-14 and KM-16 magnets provides beam shooting into bending septum magnet when operating with the booster and beam extraction in the direction of the storage-accelerator complex

Superconductor Requirements and Characterization for High Field Accelerator Magnets

Energy Technology Data Exchange (ETDEWEB)

Barzi, E.; Zlobin, A. V.

2015-05-01

The 2014 Particle Physics Project Prioritization Panel (P5) strategic plan for U.S. High Energy Physics (HEP) endorses a continued world leadership role in superconducting magnet technology for future Energy Frontier Programs. This includes 10 to 15 T Nb₃Sn accelerator magnets for LHC upgrades and a future 100 TeV scale pp collider, and as ultimate goal that of developing magnet technologies above 20 T based on both High Temperature Superconductors (HTS) and Low Temperature Superconductors (LTS) for accelerator magnets. To achieve these objectives, a sound conductor development and characterization program is needed and is herein described. This program is intended to be conducted in close collaboration with U.S. and International labs, Universities and Industry.

R and D of Nb(3)Sn accelerator magnets at Fermilab

International Nuclear Information System (INIS)

Zlobin, A.V.; Ambrosio, G.; Andreev, N.; Barzi, E; Bordini, B.; Bossert, R.; Carcagno, R.; Chichili, D.R.; DiMarco, J.; Elementi, L.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Kephart, R.; Lamm, M.; Limon, P.J.; Novitski, I.; Orris, D.; Pischalnikov, Yu.; Schlabach, P.; Stanek, R.

2004-01-01

Fermilab is developing and investigating different high-field magnet designs for present and future accelerators. The magnet RandD program was focused on the 10-12 T accelerator magnets based on Nb 3 Sn superconductor and explored both basic magnet technologies for brittle superconductors--wind-and-react and react-and-wind. Magnet design studies in support of LHC upgrades and VLHC are being performed. A series of 1-m long single-bore models of cos-theta Nb 3 Sn dipoles based on wind-and-react technique was fabricated and tested. Three 1-m long flat racetracks and the common coil dipole model, based on a single-layer coil and wide reacted Nb 3 Sn cable, have also been fabricated and tested. Extensive theoretical studies of magnetic instabilities in Nb 3 Sn strands, cable and magnet were performed which led to successful 10 T dipole model. This paper presents the details of the Fermilab's high field accelerator magnet program, reports its status and major results, and formulates the program next steps

R and D of Nb(3)Sn accelerator magnets at Fermilab

Energy Technology Data Exchange (ETDEWEB)

Zlobin, A.V.; Ambrosio, G.; Andreev, N.; Barzi, E; Bordini, B.; Bossert, R.; Carcagno, R.; Chichili, D.R.; DiMarco, J.; Elementi, L.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Kephart, R.; Lamm, M.; Limon, P.J.; Novitski, I.; Orris, D.; Pischalnikov, Yu.; Schlabach, P.; Stanek, R.; /Fermilab

2004-11-01

Fermilab is developing and investigating different high-field magnet designs for present and future accelerators. The magnet R&D program was focused on the 10-12 T accelerator magnets based on Nb{sub 3}Sn superconductor and explored both basic magnet technologies for brittle superconductors--wind-and-react and react-and-wind. Magnet design studies in support of LHC upgrades and VLHC are being performed. A series of 1-m long single-bore models of cos-theta Nb{sub 3}Sn dipoles based on wind-and-react technique was fabricated and tested. Three 1-m long flat racetracks and the common coil dipole model, based on a single-layer coil and wide reacted Nb{sub 3}Sn cable, have also been fabricated and tested. Extensive theoretical studies of magnetic instabilities in Nb{sub 3}Sn strands, cable and magnet were performed which led to successful 10 T dipole model. This paper presents the details of the Fermilab's high field accelerator magnet program, reports its status and major results, and formulates the program next steps.

Future Accelerator Magnet Needs

International Nuclear Information System (INIS)

Devred, Arnaud; Gourlay, Stephen A.; Yamamoto, Akira

2005-01-01

Superconducting magnet technology is continually evolving in order to meet the demanding needs of new accelerators and to provide necessary upgrades for existing machines. A variety of designs are now under development, including high fields and gradients, rapid cycling and novel coil configurations. This paper presents a summary of R and D programs in the EU, Japan and the USA. A performance comparison between NbTi and Nb 3 Sn along with fabrication and cost issues are also discussed

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

Science.gov (United States)

Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

2006-01-01

We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

Magnetic field, reconnection, and particle acceleration in extragalactic jets

Science.gov (United States)

Romanova, M. M.; Lovelace, R. V. E.

1992-01-01

Extra-galactic radio jets are investigated theoretically taking into account that the jet magnetic field is dragged out from the central rotating source by the jet flow. Thus, magnetohydrodynamic models of jets are considered with zero net poloidal current and flux, and consequently a predominantly toroidal magnetic field. The magnetic field naturally has a cylindrical neutral layer. Collisionless reconnection of the magnetic field in the vicinity of the neutral layer acts to generate a non-axisymmetric radial magnetic field. In turn, axial shear-stretching of reconnected toroidal field gives rise to a significant axial magnetic field if the flow energy-density is larger than the energy-density of the magnetic field. This can lead to jets with an apparent longitudinal magnetic field as observed in the Fanaroff-Riley class II jets. In the opposite limit, where the field energy-density is large, the field remains mainly toroidal as observed in Fanaroff-Riley class I jets. Driven collisionless reconnection at neutral layers may lead to acceleration of electrons to relativistic energies in the weak electrostatic field of the neutral layer. A simple model is discussed for particle acceleration at neutral layers in electron/positron and electron/proton plasmas.

Acceleration of superparamagnetic particles with magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Stange, R., E-mail: Robert.stange@tu-dresden.de; Lenk, F.; Bley, T.; Boschke, E.

2017-04-01

High magnetic capture efficiency in the context of Biomagnetic Separation (BMS) using superparamagnetic particles (SMPs) requires efficient mixing and high relative velocities between cellular and other targets and SMPs. For this purpose, batch processes or microfluidic systems are commonly used. Here, we analyze the characteristics of an in-house developed batch process experimental setup, the Electromagnetic Sample Mixer (ESM) described earlier. This device uses three electromagnets to increase the relative velocity between SMPs and targets. We carry out simulations of the magnetic field in the ESM and in a simpler paradigmatic setup, and thus were able to calculate the force field acting on the SMPs and to simulate their relative velocities and fluid dynamics due to SMP movement. In this way we were able to show that alternate charging of the magnets induces a double circular stream of SMPs in the ESM, resulting in high relative velocities of SMPs to the targets. Consequently, due to the conservation of momentum, the fluid experiences an acceleration induced by the SMPs. We validated our simulations by microscopic observation of the SMPs in the magnetic field, using a homemade apparatus designed to accommodate a long working-distance lens. By comparing the results of modeling this paradigmatic setup with the experimental observations, we determined that the velocities of the SMPs corresponded to the results of our simulations. - Highlights: • Investigation of a batch process setup for complex forming at Biomagnetic Separation. • Simulation of fluid flow characteristics in this Electro Magnetic Samplemixer. • Simulation of relative velocities between magnetic particles and fluid in the setup. • Simulation of fluid flow induced by the acceleration of magnet particles. • Validation of magnetic fields and flow characteristics in paradigmatic setups. • Reached relative velocity is higher than the sedimentation velocity of the particles • Alternating

AIR-MRF: Accelerated iterative reconstruction for magnetic resonance fingerprinting.

Science.gov (United States)

Cline, Christopher C; Chen, Xiao; Mailhe, Boris; Wang, Qiu; Pfeuffer, Josef; Nittka, Mathias; Griswold, Mark A; Speier, Peter; Nadar, Mariappan S

2017-09-01

Existing approaches for reconstruction of multiparametric maps with magnetic resonance fingerprinting (MRF) are currently limited by their estimation accuracy and reconstruction time. We aimed to address these issues with a novel combination of iterative reconstruction, fingerprint compression, additional regularization, and accelerated dictionary search methods. The pipeline described here, accelerated iterative reconstruction for magnetic resonance fingerprinting (AIR-MRF), was evaluated with simulations as well as phantom and in vivo scans. We found that the AIR-MRF pipeline provided reduced parameter estimation errors compared to non-iterative and other iterative methods, particularly at shorter sequence lengths. Accelerated dictionary search methods incorporated into the iterative pipeline reduced the reconstruction time at little cost of quality. Copyright © 2017 Elsevier Inc. All rights reserved.

Technical competence in cardiovascular magnetic resonance and computed tomography

International Nuclear Information System (INIS)

Fernandes, Juliano Lara; Shiozaki, Afonso Akio; Azevedo Filho, Clerio Francisco de; Rochitte, Carlos Eduardo; Pinto, Ibraim Marciarelli Francisco; Lopes, Marly Maria Uellendahl; Schvartzman, Paulo Roberto

2009-01-01

Cardiovascular magnetic resonance and computed tomography have evolved as very practical and useful techniques applied in clinical cardiology. Due to their rapid acceptance in the cardiology community and widespread use, training of both cardiologists and radiologists on this subspecialty has not been homogeneous so far. This in part explains significant differences observed in the diverse background found in today’s practicing physicians who execute these exams. In order to guide training facilities as well as both payers, contractors and general cardiologists ordering the exam, this document provides a minimum standard that should be accomplished by all physicians who pursue education in the field and for those who already practice in it. The clinical competences listed in this statement are by no means thorough but should be required by all those involved in cardiovascular magnetic resonance and computed tomography as the customary requirements for current and future practitioners. (author)

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

Science.gov (United States)

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

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel, and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a three-dimensional relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic electron-positron jet front propagating into an ambient electron-positron plasma with and without initial magnetic fields. We find small differences in the results for no ambient and modest ambient magnetic fields. New simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. Furthermore, the nonlinear fluctuation amplitudes of densities, currents, and electric and magnetic fields in the electron-positron shock are larger than those found in the electron-ion shock studied in a previous paper at a comparable simulation time. This comes from the fact that both electrons and positrons contribute to generation of the Weibel instability. In addition, we have performed simulations with different electron skin depths. We find that growth times scale inversely with the plasma frequency, and the sizes of structures created by tine Weibel instability scale proportionally to the electron skin depth. This is the expected result and indicates that the simulations have sufficient grid resolution. While some Fermi acceleration may occur at the jet front, the majority of electron and positron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying nonuniform, small-scale magnetic fields, which contribute to the electron s (positron s) transverse deflection behind the jet head. This

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

Science.gov (United States)

Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

Review of Journal of Cardiovascular Magnetic Resonance 2009

Directory of Open Access Journals (Sweden)

Neubauer S

2010-03-01

Full Text Available Abstract There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR. In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.

Prospects for 10T accelerator dipole magnets

International Nuclear Information System (INIS)

Taylor, C.E.; Meuser, R.B.

1981-03-01

A next-generation major accelerator will require the highest possible field to minimize the circumference; however, there have been no proven designs for suitable magnets with fields substantially higher than 5T. A number of successful 4 to 5T dipole magnets have been built in recent years; these have involved long and difficult development projects. The 3'' bore 4.25T magnets for the Doubler are being produced by the hundreds at Fermilab, and a number of prototypes of the 5.2'' bore 5T ISABELLE magnets have been built. Successful short, approx. 5T models have been made at SACLAY, KEK, and Serpukhov, and a number of model magnets with lower fields have been built at many laboratories. Field uniformity achieved in these magnets is about ΔB/B approx. = 10 -3 . 10T magnets with higher field uniformity will be a challenging development task. The general problems of high-field (10T) magnets are discussed in terms of superconductor performance and mechanical limitations

Magnetic Materials Characterization and Modeling for the Enhanced Design of Magnetic Shielding of Cryomodules in Particle Accelerators

Energy Technology Data Exchange (ETDEWEB)

Sah, Sanjay [Virginia Commonwealth Univ., Richmond, VA (United States)

2016-05-31

Particle accelerators produce beams of high-energy particles, which are used for both fundamental and applied scientific research and are critical to the development of accelerator driven sub-critical reactor systems. An effective magnetic shield is very important to achieve higher quality factor (Qo) of the cryomodule of a particle accelerator. The allowed value of field inside the cavity due to all external fields (particularly the Earth’s magnetic field) is ~15 mG or less. The goal of this PhD dissertation is to comprehensively study the magnetic properties of commonly used magnetic shielding materials at both cryogenic and room temperatures. This knowledge can be used for the enhanced design of magnetic shields of cryomodes (CM) in particle accelerators. To this end, we first studied the temperature dependent magnetization behavior (M-H curves) of Amumetal and A4K under different annealing and deformation conditions. This characterized the effect of stress or deformation induced during the manufacturing processes and subsequent restoration of high permeability with appropriate heat treatment. Next, an energy based stochastic model for temperature dependent anhysteretic magnetization behavior of ferromagnetic materials was proposed and benchmarked against experimental data. We show that this model is able to simulate and explain the magnetic behavior of as rolled, deformed and annealed amumetal and A4K over a large range of temperatures. The experimental results for permeability are then used in a finite element model (FEM) in COMSOL to evaluate the shielding effectiveness of multiple shield designs at room temperature as well as cryogenic temperature. This work could serve as a guideline for future design, development and fabrication of magnetic shields of CMs.

Magnetized particle motion and acceleration around a Schwarzschild black hole in a magnetic field

International Nuclear Information System (INIS)

Abdujabbarov, Ahmadjon; Bobomurat Ahmedov; Rahimov, Ozodbek; Salikhbaev, Umar

2014-01-01

The capture cross section of magnetized particles with nonvanishing magnetic moment by a Schwarzschild black hole immersed in an asymptotically uniform magnetic field has been studied as an extension of the approach developed in Zakharov (1994 Class. Quantum Grav. 11 1027) for neutral unmagnetized particles in the Reissner–Nordström spacetime. The magnetic moment of the particle is chosen as in de Felice and Sorge (2003 Class. Quantum Grav. 20 469). It is shown that the spin of the particle sustains the stability of particles circularly orbiting around the black hole immersed in a magnetic field, i.e., a spinning particle's motion near the Schwarzschild black hole horizon is more stable than that of a particle with zero spin. It is shown that the magnetic parameter essentially changes the value of the critical angular momentum and affects the process of capture of the particles by the central black hole. Furthermore, the interaction between the magnetic moment of the particle and the magnetic field forces stable circular orbits to shift to the central object, and this effect should be taken into account in astrophysical scenarios related to the accretion discs and in measuring the spin of the black holes. The magnetized particle's acceleration mechanism near the black hole in an external magnetic field is studied. It is shown that due to the presence of a magnetic field, magnetized particles can accelerate to unlimited high energies. (paper)

ECG gated magnetic resonance imaging in cardiovascular disease

International Nuclear Information System (INIS)

Park, Jae Hyung; Im, Chung Kie; Han, Man Chung; Kim, Chu Wan

1985-01-01

Using KAIS 0.15 Tesla resistive magnetic imaging system, ECG gated magnetic resonance (MR) image of various cardiovascular disease was obtained in 10 patients. The findings of MR image of the cardiovascular disease were analysed and the results were as follows: 1. In 6 cases of acquired and congenital cardiac diseases, there were 2 cases of myocardial infarction, 1 case of mitral stenosis and 3 cases of corrected transportation of great vessels. The others were 3 cases of aortic disease and 1 case of pericardial effusion with lymphoma. 2. Myocardial thinning and left ventricular aneurysm were detected in MR images of myocardial infarction. The left atrium was well delineated and enlarged in the case of mitral stenosis. And segmental analysis was possible in the cases of corrected transposition since all cardiac structures were well delineated anatomically. 3. In aortic diseases, the findings of MR image were enlarged lumen, compressed cardiac chambers in ascending aortic aneurysm, intimal flap, enhanced false lumen in dissecting aneurysm and irregular narrowing of aorta with arterial obstruction in Takayasu's arteritis. 4. Pericardial effusion revealed a conspicuous contrast with neighboring mediastinal fat and cardiac wall due to it low signal encircling cardiac wall. 5. ECG gated MR image is an accurate non-invasive imaging modality for the diagnosis of cardiovascular disease and better results of its clinical application are expected in the future with further development in the imaging system and more clinical experiences

Numerical and experimental investigations of coupled electromagnetic and thermal fields in superconducting accelerator magnets

International Nuclear Information System (INIS)

Mierau, Anna

2013-01-01

The new international facility for antiproton and ion research FAIR will be built in Darmstadt (Germany). The existing accelerator facility of GSI Helmholtzzentrum for Heavy Ion Research will serve as a pre-accelerator for the new facility. FAIR will provide high-energy antiproton and ion beams with unprecedented intensity and quality for fundamental research of states of matter and the evolution of the universe. The central component of FAIR's accelerator and storage rings complex is a double-ring accelerator consisting of two heavy ion synchrotrons SIS100 and SIS300. The SIS100 is the primary accelerator of FAIR. The desired beam properties of SIS100 require a design of the machine much more challenging than the conventional design of existing proton and ion synchrotrons. The key technical components of each synchrotron are the special electromagnets, which allow guiding the charged particles on their orbits in the synchrotron during the acceleration processes. For a stable operation of the SIS100's the magnets have to produce extremely homogeneous magnetic fields. Furthermore, the SIS100 high-intensity ion beam modes, for example with U 28+ ions, require an ultra-high vacuum in the beam pipe of the synchrotron, which can be generated effectively only at low temperatures below 15 K. Due to the field quality requirements for the magnets, the properties of the dynamic vacuum in the beam pipe but also in order to minimise future operating costs, fast ramped superconducting magnets will be used to guide the beam in SIS100. These magnets have been developed at GSI within the framework of the FAIR project. Developing a balanced design of a superconducting accelerator magnet requires a sound understanding of the interaction between its thermal and electromagnetic fields. Of special importance in this case are the magnetic field properties such as the homogeneity of the static magnetic field in the aperture of the magnet, and the dynamic heat losses of the whole magnet

State-of-the-art superconducting accelerator magnets

CERN Document Server

Rossi, L

2002-01-01

With the LHC the technology of NbTi-based accelerator magnets has been pushed to the limit. By operating in superfluid helium, magnetic fields in excess of 10 T have been reached in various one meter-long model magnets while full scale magnets, 15 meter-long dipoles, have demonstrated possibility of safe operation in the 8.3-9 tesla range, with the necessary, very tight, field accuracy. The paper reviews the key points of the technology that has permitted the construction of the largest existing superconducting installations (Fermilab, Desy and Brookhaven), highlighting the novelties of the design of the LHC dipoles, quadrupoles and other superconducting magnets. All together the LHC project will need more than 5000 km of fine filament superconducting cables capable of 14 kA @ 10 T, 1.9 K. (13 refs).

Technical competence in cardiovascular magnetic resonance and computed tomography; Competencia tecnica em ressonancia e tomografia cardiovascular

Energy Technology Data Exchange (ETDEWEB)

Fernandes, Juliano Lara; Shiozaki, Afonso Akio; Azevedo Filho, Clerio Francisco de; Rochitte, Carlos Eduardo; Pinto, Ibraim Marciarelli Francisco; Lopes, Marly Maria Uellendahl; Schvartzman, Paulo Roberto, E-mail: jlaraf@fcm.unicamp.br [Universidade de Campinas (UNICAMP/GERT) SP (Brazil). Grupo de Estudo em Ressonancia e Tomografia Cardiovascular

2009-10-15

Cardiovascular magnetic resonance and computed tomography have evolved as very practical and useful techniques applied in clinical cardiology. Due to their rapid acceptance in the cardiology community and widespread use, training of both cardiologists and radiologists on this subspecialty has not been homogeneous so far. This in part explains significant differences observed in the diverse background found in today’s practicing physicians who execute these exams. In order to guide training facilities as well as both payers, contractors and general cardiologists ordering the exam, this document provides a minimum standard that should be accomplished by all physicians who pursue education in the field and for those who already practice in it. The clinical competences listed in this statement are by no means thorough but should be required by all those involved in cardiovascular magnetic resonance and computed tomography as the customary requirements for current and future practitioners. (author)

Collection of ions in a plasma by magnetic field acceleration with selective polarization

International Nuclear Information System (INIS)

Forsen, H.K.

1976-01-01

Method and apparatus are described for generating and accelerating ions in a vapor by use of relatively polarized laser radiation and a magnetic field. As applied to uranium isotope enrichment, a flowing uranium vapor has particles of the 235 U isotope type selectively ionized by laser radiation and the ionized flow is subjected to a transverse gradient in a magnetic field. The magnetic field gradient induces an acceleration on the ionized particles of 235 U which deflects them from their normal flow path toward a collecting structure. High magnetic field and corresponding high ion accelerations are achieved without loss in ionization selectivity by maintaining a polarization between the applied laser radiation and magnetic field which minimizes Zeeman splitting of the uranium energy states

''Theta gun,'' a multistage, coaxial, magnetic induction projectile accelerator

International Nuclear Information System (INIS)

Burgess, T.J.; Duggin, B.W.; Cowan, M. Jr.

1985-11-01

We experimentally and theoretically studied a multistage coaxial magnetic induction projectile accelerator. We call this system a ''theta gun'' to differentiate it from other coaxial accelerator concepts such as the mass driver. We conclude that this system can theoretically attain railgun performance only for large caliber or very high injection velocity and, even then, only for long coil geometry. Our experiments with a three-stage, capactor bank-driven accelerator are described. The experiments are modeled with a 1-1/2 dimensional equivalent circuit-hydrodynamics code which is also described. We derive an expression for the conditions of coaxial accelerator-railgun ''velocity breakeven'' in the absence of ohmic and hydrodynamic effects. This, in conjunction with an expression for the magnetic coupling coefficient, defines a set of geometric relations which the coaxial system must simultaneously satisfy. Conclusions concerning both the existence and configuration of a breakeven coaxial system follow from this requirement. The relative advantages and disadvantages of the coaxial induction projectile accelerator, previously cited in the literature, are critiqued from the viewpoint of our analysis and experimental results. We find that the advantages vis-a-vis the railgun have been overstated. 13 refs., 17 figs

ELECTRON ACCELERATION IN CONTRACTING MAGNETIC ISLANDS DURING SOLAR FLARES

Energy Technology Data Exchange (ETDEWEB)

Borovikov, D.; Tenishev, V.; Gombosi, T. I. [University of Michigan, Department of Climate and Space Sciences and Engineering, 2455 Hayward Street, Ann Arbor, MI 48104-2143 (United States); Guidoni, S. E. [The Catholic University of America, 620 Michigan Avenue Northeast, Washington, DC 20064 (United States); DeVore, C. R.; Karpen, J. T.; Antiochos, S. K. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2017-01-20

Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integration of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons’ energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.

Case Studies on Superconducting Magnets for Particle Accelerators

International Nuclear Information System (INIS)

Ferracin, P

2014-01-01

During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes

Case Studies on Superconducting Magnets for Particle Accelerators

Energy Technology Data Exchange (ETDEWEB)

Ferracin, P [European Organization for Nuclear Research, Geneva (Switzerland)

2014-07-01

During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes.

The role of magnetic-field-aligned electric fields in auroral acceleration

International Nuclear Information System (INIS)

Block, L.P.; Faelthammar, C.G.

1990-01-01

Electric field measurements on the Swedish satellite Viking have confirmed and extended earlier observations on S3-3 and provided further evidence of the role of dc electric fields in auroral acceleration processes. On auroral magnetic field lines the electric field is strongly fluctuating both transverse and parallel to the magnetic field. The significance of these fluctuations for the auroral acceleration process is discussed. A definition of dc electric fields is given in terms of their effects on charged particles. Fluctuations below several hertz are experienced as dc by typical auroral electrons if the acceleration length is a few thousand kilometers. For ions the same is true below about 0.1 Hz. The magnetic-field-aligned (as well as the transverse) component of the electric field fluctuations has a maximum below 1 Hz, in a frequency range that appears as dc to the electrons but not to the ions. This allows it to cause a selective acceleration, which may be important in explaining some of the observed characteristics of auroral particle distributions. The electric field observations on Viking support the conclusion that magnetic-field-aligned potential drops play an important role in auroral acceleration, in good agreement with particle observations boht on Viking and on the DE satellites. They also show that a large part, or even all, of the accelerating potential drop may be accounted for by numerous weak (about a volt) electric double layers, in agreement with earlier observations on the S3-3 satellite and with an early theoretical suggestion by L. Block

Design and test of a superconducting magnet in a linear accelerator for an Accelerator Driven Subcritical System

International Nuclear Information System (INIS)

Peng, Quanling; Xu, Fengyu; Wang, Ting; Yang, Xiangchen; Chen, Anbin; Wei, Xiaotao; Gao, Yao; Hou, Zhenhua; Wang, Bing; Chen, Yuan; Chen, Haoshu

2014-01-01

A batch superconducting solenoid magnet for the ADS proton linear accelerator has been designed, fabricated, and tested in a vertical dewar in Sept. 2013. A total of ten superconducting magnets will be installed into two separate cryomodules. Each cryomodule contains six superconducting spoke RF cavities for beam acceleration and five solenoid magnets for beam focusing. The multifunction superconducting magnet contains a solenoid for beam focusing and two correctors for orbit correction. The design current for the solenoid magnet is 182 A. A quench performance test shows that the operating current of the solenoid magnet can reach above 300 A after natural quenching on three occasions during current ramping (260 A, 268 A, 308 A). The integrated field strength and leakage field at the nearby superconducting spoke cavities all meet the design requirements. The vertical test checked the reliability of the test dewar and the quench detection system. This paper presents the physical and mechanical design of the batch magnets, the quench detection technique, field measurements, and a discussion of the residual field resulting from persistent current effects

3D accelerator magnet calculations using MAGNUS-3D

International Nuclear Information System (INIS)

Pissanetzky, S.; Miao, Y.

1989-01-01

The steady trend towards increased magnetic and geometric complexity in the design of accelerator magnets has caused a need for reliable 3D computer models and a better understanding of the behavior of magnetic system in three dimensions. The capabilities of the MAGNUS-3D family of programs are ideally suited to solve this class of problems and provide insight into 3D effects. MAGNUS-3D can solve any problem of magnetostatics involving permanent magnets, nonlinear ferromagnetic materials and electric conductors. MAGNUS-3D uses the finite element method and the two-scalar-potentials formulation of Maxwell's equations to obtain the solution, which can then be used interactively to obtain tables of field components at specific points or lines, plots of field lines, function graphs representing a field component plotted against a coordinate along any line in space (such as the beam line), and views of the conductors, the mesh and the magnetic bodies. The magnetic quantities that can be calculated include the force or torque on conductors or magnetic parts, the energy, the flux through a specified surface, line integrals of any field component along any line in space, and the average field or potential harmonic coefficients. We describe the programs with emphasis placed on their use for accelerator magnet design, and present an advanced example of actual calculations. (orig.)

Properties and practical performance of SC magnets in accelerators

International Nuclear Information System (INIS)

Schmueser, P.

1992-01-01

A report is given on the properties and performance of superconducting accelerator magnets in the 5-6 Tesla regime. Most of the information stems from the industrially produced HERA magnets which were thoroughly tested both at industry and at DESY; data from prototype magnets for RHIC and SSC are also included. Persistent current effects were studied in detail. During the commissioning of the proton-electron collider HERA the superconducting magnets worked with high reliability and their properties were exactly as predicted from the magnetic measurements. (author) 11 refs.; 8 figs

Quantitative characterization of myocardial infarction by cardiovascular magnetic resonance predicts future cardiovascular events in patients with ischemic cardiomyopathy

Directory of Open Access Journals (Sweden)

Pauly John M

2008-04-01

Full Text Available Abstract Background Cardiovascular magnetic resonance (CMR can provide quantitative data of the myocardial tissue utilizing high spatial and temporal resolution along with exquisite tissue contrast. Previous studies have correlated myocardial scar tissue with the occurrence of ventricular arrhythmia. This study was conducted to evaluate whether characterization of myocardial infarction by CMR can predict cardiovascular events in patients with ischemic cardiomyopathy (ICM. Results We consecutively studied 86 patients with ICM (LVEF Conclusion Quantification of the scar volume and scar percentage by CMR is superior to LVEDV, LVESV, and LVEF in prognosticating the future likelihood of the development of cardiovascular events in patients with ICM.

MAGNUS-3D: Accelerator magnet calculations in 3-dimensions

Science.gov (United States)

Pissanetzky, S.

1988-12-01

MAGNUS-3D is a professional finite element code for nonlinear magnetic engineering. MAGNUS-3D can solve numerically any general problem of linear or nonlinear magnetostatics in three dimensions. The problem is formulated in a domain with Dirichlet, Neumann or periodic boundary conditions, that can contain any combination of conductors of any shape in space, nonlinear magnetic materials with magnetic properties specified by magnetization tables, and nonlinear permanent magnets with any given demagnetization curve. MAGNUS-3D uses the two-scalar-potentials formulation of Magnetostatics and the finite element method, has an automatic 3D mesh generator, and advanced post-processing features that include graphics on a variety of supported devices, tabulation, and calculation of design quantities required in Magnetic Engineering. MAGNUS-3D is a general purpose 3D code, but it has been extensively used for accelerator work and many special features required for accelerator engineering have been incorporated into the code. One of such features is the calculation of field harmonic coefficients averaged in the direction of the beam, so important for the design of magnet ends. Another feature is its ability to calculate line integrals of any field component along the direction of the beam, or plot the field as a function of the z coordinate. MAGNUS-3D has found applications to the design of accelerator magnets and spectrometers, steering magnets, wigglers and undulators for free electron lasers, microtrons and magnets for synchrotron light sources, as well as magnets for NMR and medical applications, recording heads and various magnetic devices. There are three more programs closely associated with MAGNUS-3D. MAGNUS-GKS is the graphical postprocessor for the package; it supports a numer of output devices, including color vector or bit map devices. WIRE is an independent program that can calculate the field produced by any configuration of electric conductors in space, at any

Characteristics of magnetic switch used as main switch of solid-state accelerator

International Nuclear Information System (INIS)

Li Song; Qian Baoliang; Yang Hanwu; Meng Zhipeng; Yang Shi

2012-01-01

In order to improve the performance of solid-state accelerator, the characteristics of magnetic switch used as the main switch of the accelerator have been investigated. The volume of magnetic core, the loss, and saturated inductance of the magnetic switch have been derived. The results show that the spacing factor of the magnetic switch reaches the peak when the height of the magnetic materials is 0.05 m for selected magnetic cores. The saturated inductance of the windings changes slowly when the average magnetic path length of the core is greater than 1 m. The physical process of saturation in the cores was analyzed by using saturation-wave theory. The rise-time factor of the output pulse was derived. The thickness, resistivity and magnetic path length difference of the magnetic core are shown to be key parameters affecting the rise-time factor. (authors)

1999 Review of superconducting dipole and quadrupole magnets for particle accelerators

International Nuclear Information System (INIS)

Devred, A.

1999-12-01

The quest for elementary particles has promoted the development of particle accelerators producing beams of increasingly higher energies. In a synchrotron-type accelerator, the particle energy is directly proportional to the product of the machine's radius times the bending magnets' field strength. Present proton experiments at the TeV scale require facilities with circumferences ranging from a few to tens of kilometers and relying on a large number (several hundreds to several thousands) of high field dipole magnets and high field gradient quadrupole magnets. These electro-magnets use high current density, low critical temperature superconducting cables and are cooled down at liquid helium temperature. They are among the most costly and the most challenging components of the machine. After explaining what are the various types of accelerator magnets and why they are needed (section 1), we present a brief history of large superconducting particle accelerators, and we detail ongoing superconducting accelerator magnet R and D programs around the world (Section 2). Then, we review the superconducting materials that are available at industrial scale (chiefly, NbTi and Nb3Sn), and we describe the manufacturing of NbTi wires and cables (section 3). We also present the difficulties of processing and insulating Nb3Sn conductors which, so far, have limited the use of this material in spite of its superior performances. We continue by presenting the complex formalism used to represent two-dimensional fields (section 4), and we discuss the two-dimensional current distributions that are the most appropriate for generating pure dipole and pure quadrupole fields (section 5). We explain how these ideal distributions can be approximated by so-called cosθ and cos 2 θ coil designs and we describe the difficulties of realizing coil ends. Next, we present the mechanical design concepts that have been developed to restrain magnet coils and to ensure proper conductor positioning

1999 Review of superconducting dipole and quadrupole magnets for particle accelerators

Energy Technology Data Exchange (ETDEWEB)

Devred, A. [CEA/Saclay, Dept. d' Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l' Instrumentation Associee (DAPNIA), 91 - Gif-sur-Yvette (France); CERN, Conseil Europeen pour la recherche nucleaire, Laboratoire europeen pour la physique des particules Geneve (Switzerland)

1999-12-01

The quest for elementary particles has promoted the development of particle accelerators producing beams of increasingly higher energies. In a synchrotron-type accelerator, the particle energy is directly proportional to the product of the machine's radius times the bending magnets' field strength. Present proton experiments at the TeV scale require facilities with circumferences ranging from a few to tens of kilometers and relying on a large number (several hundreds to several thousands) of high field dipole magnets and high field gradient quadrupole magnets. These electro-magnets use high current density, low critical temperature superconducting cables and are cooled down at liquid helium temperature. They are among the most costly and the most challenging components of the machine. After explaining what are the various types of accelerator magnets and why they are needed (section 1), we present a brief history of large superconducting particle accelerators, and we detail ongoing superconducting accelerator magnet R and D programs around the world (Section 2). Then, we review the superconducting materials that are available at industrial scale (chiefly, NbTi and Nb3Sn), and we describe the manufacturing of NbTi wires and cables (section 3). We also present the difficulties of processing and insulating Nb3Sn conductors which, so far, have limited the use of this material in spite of its superior performances. We continue by presenting the complex formalism used to represent two-dimensional fields (section 4), and we discuss the two-dimensional current distributions that are the most appropriate for generating pure dipole and pure quadrupole fields (section 5). We explain how these ideal distributions can be approximated by so-called cos{theta} and cos{sup 2}{theta} coil designs and we describe the difficulties of realizing coil ends. Next, we present the mechanical design concepts that have been developed to restrain magnet coils and to ensure proper

Ambipolar ion acceleration in an expanding magnetic nozzle

Energy Technology Data Exchange (ETDEWEB)

Longmier, Benjamin W; Carter, Mark D; Cassady, Leonard D; Chancery, William J; Diaz, Franklin R Chang; Glover, Tim W; Ilin, Andrew V; McCaskill, Greg E; Olsen, Chris S; Squire, Jared P [Ad Astra Rocket Company, 141 W. Bay Area Blvd, Webster, TX (United States); Bering, Edgar A III [Department of Physics and Department of Electrical and Computer Engineering, University of Houston, 617 Science and Research Building 1, Houston, TX (United States); Hershkowitz, Noah [Department of Engineering Physics, University of Wisconsin, 1500 Engineering Dr., Madison, WI (United States)

2011-02-15

The helicon plasma stage in the Variable Specific Impulse Magnetoplasma Rocket (VASIMR (registered)) VX-200i device was used to characterize an axial plasma potential profile within an expanding magnetic nozzle region of the laboratory based device. The ion acceleration mechanism is identified as an ambipolar electric field produced by an electron pressure gradient, resulting in a local axial ion speed of Mach 4 downstream of the magnetic nozzle. A 20 eV argon ion kinetic energy was measured in the helicon source, which had a peak magnetic field strength of 0.17 T. The helicon plasma source was operated with 25 mg s{sup -1} argon propellant and 30 kW of RF power. The maximum measured values of plasma density and electron temperature within the exhaust plume were 1 x 10{sup 20} m{sup -3} and 9 eV, respectively. The measured plasma density is nearly an order of magnitude larger than previously reported steady-state helicon plasma sources. The exhaust plume also exhibits a 95% to 100% ionization fraction. The size scale and spatial location of the plasma potential structure in the expanding magnetic nozzle region appear to follow the size scale and spatial location of the expanding magnetic field. The thickness of the potential structure was found to be 10{sup 4} to 10{sup 5} {lambda}{sub De} depending on the local electron temperature in the magnetic nozzle, many orders of magnitude larger than typical laboratory double layer structures. The background plasma density and neutral argon pressure were 10{sup 15} m{sup -3} and 2 x 10{sup -5} Torr, respectively, in a 150 m{sup 3} vacuum chamber during operation of the helicon plasma source. The agreement between the measured plasma potential and plasma potential that was calculated from an ambipolar ion acceleration analysis over the bulk of the axial distance where the potential drop was located is a strong confirmation of the ambipolar acceleration process.

Novel Approach to Linear Accelerator Superconducting Magnet System

International Nuclear Information System (INIS)

Kashikhin, Vladimir

2011-01-01

Superconducting Linear Accelerators include a superconducting magnet system for particle beam transportation that provides the beam focusing and steering. This system consists of a large number of quadrupole magnets and dipole correctors mounted inside or between cryomodules with SCRF cavities. Each magnet has current leads and powered from its own power supply. The paper proposes a novel approach to magnet powering based on using superconducting persistent current switches. A group of magnets is powered from the same power supply through the common, for the group of cryomodules, electrical bus and pair of current leads. Superconducting switches direct the current to the chosen magnet and close the circuit providing the magnet operation in a persistent current mode. Two persistent current switches were fabricated and tested. In the paper also presented the results of magnetic field simulations, decay time constants analysis, and a way of improving quadrupole magnetic center stability. Such approach substantially reduces the magnet system cost and increases the reliability.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

Science.gov (United States)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Mizuno, Y.

2005-01-01

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 by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

THE EFFECT OF COOLING ON PARTICLE TRAJECTORIES AND ACCELERATION IN RELATIVISTIC MAGNETIC RECONNECTION

Energy Technology Data Exchange (ETDEWEB)

Kagan, Daniel; Nakar, Ehud [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Piran, Tsvi, E-mail: daniel.kagan@mail.huji.ac.il [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)

2016-12-20

The maximum synchrotron burnoff limit of 160 MeV represents a fundamental limit to radiation resulting from electromagnetic particle acceleration in one-zone ideal plasmas. In magnetic reconnection, however, particle acceleration and radiation are decoupled because the electric field is larger than the magnetic field in the diffusion region. We carry out two-dimensional particle-in-cell simulations to determine the extent to which magnetic reconnection can produce synchrotron radiation above the burnoff limit. We use the test particle comparison (TPC) method to isolate the effects of cooling by comparing the trajectories and acceleration efficiencies of test particles incident on such a reconnection region with and without cooling them. We find that the cooled and uncooled particle trajectories are typically similar during acceleration in the reconnection region, and derive an effective limit on particle acceleration that is inversely proportional to the average magnetic field experienced by the particle during acceleration. Using the calculated distribution of this average magnetic field as a function of uncooled final particle energy, we find analytically that cooling does not affect power-law particle energy spectra except at energies far above the synchrotron burnoff limit. Finally, we compare fully cooled and uncooled simulations of reconnection, confirming that the synchrotron burnoff limit does not produce a cutoff in the particle energy spectrum. Our results indicate that the TPC method accurately predicts the effects of cooling on particle acceleration in relativistic reconnection, and that, even far above the burnoff limit, the synchrotron energy of radiation produced in reconnection is not limited by cooling.

THE EFFECT OF COOLING ON PARTICLE TRAJECTORIES AND ACCELERATION IN RELATIVISTIC MAGNETIC RECONNECTION

International Nuclear Information System (INIS)

Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

2016-01-01

The maximum synchrotron burnoff limit of 160 MeV represents a fundamental limit to radiation resulting from electromagnetic particle acceleration in one-zone ideal plasmas. In magnetic reconnection, however, particle acceleration and radiation are decoupled because the electric field is larger than the magnetic field in the diffusion region. We carry out two-dimensional particle-in-cell simulations to determine the extent to which magnetic reconnection can produce synchrotron radiation above the burnoff limit. We use the test particle comparison (TPC) method to isolate the effects of cooling by comparing the trajectories and acceleration efficiencies of test particles incident on such a reconnection region with and without cooling them. We find that the cooled and uncooled particle trajectories are typically similar during acceleration in the reconnection region, and derive an effective limit on particle acceleration that is inversely proportional to the average magnetic field experienced by the particle during acceleration. Using the calculated distribution of this average magnetic field as a function of uncooled final particle energy, we find analytically that cooling does not affect power-law particle energy spectra except at energies far above the synchrotron burnoff limit. Finally, we compare fully cooled and uncooled simulations of reconnection, confirming that the synchrotron burnoff limit does not produce a cutoff in the particle energy spectrum. Our results indicate that the TPC method accurately predicts the effects of cooling on particle acceleration in relativistic reconnection, and that, even far above the burnoff limit, the synchrotron energy of radiation produced in reconnection is not limited by cooling.

Pulsed high field magnets. An efficient way of shaping laser accelerated proton beams for application

Energy Technology Data Exchange (ETDEWEB)

Kroll, Florian; Schramm, Ulrich [Helmholtz-Zentrum Dresden - Rossendorf, 01328 Dresden (Germany); Technische Universitaet Dresden, 01062 Dresden (Germany); Bagnoud, Vincent; Blazevic, Abel; Busold, Simon [GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Helmholtz Institut Jena, 07734 Jena (Germany); Brabetz, Christian; Schumacher, Dennis [GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Deppert, Oliver; Jahn, Diana; Roth, Markus [Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Karsch, Leonhard; Masood, Umar [OncoRay-National Center for Radiation Research in Oncology, TU Dresden, 01307 Dresden (Germany); Kraft, Stephan [Helmholtz-Zentrum Dresden - Rossendorf, 01328 Dresden (Germany)

2015-07-01

Compact laser-driven proton accelerators are a potential alternative to complex, expensive conventional accelerators, enabling unique beam properties, like ultra-high pulse dose. Nevertheless, they still require substantial development in reliable beam generation and transport. We present experimental studies on capture, shape and transport of laser and conventionally accelerated protons via pulsed high-field magnets. These magnets, common research tools in the fields of solid state physics, have been adapted to meet the demands of laser acceleration experiments.Our work distinctively shows that pulsed magnet technology makes laser acceleration more suitable for application and can facilitate compact and efficient accelerators, e.g. for material research as well as medical and biological purposes.

Dynamics of particles accelerated by head-on collisions of two magnetized plasma shocks

Science.gov (United States)

Takeuchi, Satoshi

2018-02-01

A kinetic model of the head-on collision of two magnetized plasma shocks is analyzed theoretically and in numerical calculations. When two plasmas with anti-parallel magnetic fields collide, they generate magnetic reconnection and form a motional electric field at the front of the collision region. This field accelerates the particles sandwiched between both shock fronts to extremely high energy. As they accelerate, the particles are bent by the transverse magnetic field crossing the magnetic neutral sheet, and their energy gains are reduced. In the numerical calculations, the dynamics of many test particles were modeled through the relativistic equations of motion. The attainable energy gain was obtained by multiplying three parameters: the propagation speed of the shock, the magnitude of the magnetic field, and the acceleration time of the test particle. This mechanism for generating high-energy particles is applicable over a wide range of spatial scales, from laboratory to interstellar plasmas.

Cardiovascular magnetic resonance imaging of hypoplastic left heart syndrome in children

International Nuclear Information System (INIS)

Dillman, Jonathan R.; Hernandez, Ramiro J.; Dorfman, Adam L.; Attili, Anil K.; Agarwal, Prachi P.; Mueller, Gisela C.; Bell, Aaron

2010-01-01

Cardiovascular magnetic resonance imaging (CMR) plays an important complementary role to echocardiography and conventional angiography in the evaluation of hypoplastic left heart syndrome. This imaging modality is particularly useful for assessing cardiovascular postsurgical changes, extracardiac vascular anatomy, ventricular and valvular function, and a variety of complications. The purpose of this article is to provide a contemporary review of the role of CMR in the management of untreated and surgically palliated hypoplastic left heart syndrome in children. (orig.)

Accelerator magnet power supply using storage generator

International Nuclear Information System (INIS)

Karady, G.; Thiessen, H.A.

1987-01-01

Recently, a study investigated the feasibility of a large, 60 GeV accelerator. This paper presents the conceptual design of the magnet power supply (PS() and energy storage system. The main ring magnets are supplied by six, high-voltage and two, low-voltage power supplies. These power supplies drive a trapezoidal shaped current wave through the magnets. The peak current is 10 kA and the repetition frequency is 3.3 Hz. During the acceleration period the current is increased from 1040 A to 10,000 A within 50 msec which requires a loop voltage of 120 kV and a peak power of 1250 MW. During the reset period, the PS operates as an inverter with a peak power of -1250 MW. The large energy fluctuation necessitates the use of a storage generator. Because of the relatively high operation frequency, this generator operates in a transient mode which significantly increases the rotor current and losses. The storage generator is directly driven by a variable speed drive, which draws a practically constant power of 17 MW from the ac supply network and eliminates the pulse loading. For the reduction of dc ripple, the power supplies operate in a 24 pulse mode

Advanced multipoles for accelerator magnets theoretical analysis and their measurement

CERN Document Server

Schnizer, Pierre

2017-01-01

This monograph presents research on the transversal beam dynamics of accelerators and evaluates and describes the respective magnetic field homogeneity.  The widely used cylindrical circular multipoles have disadvantages for elliptical apertures or curved trajectories, and the book also introduces new types of advanced multipole magnets, detailing their application, as well as the numerical data and measurements obtained. The research presented here provides more precise descriptions of the field and better estimates of the beam dynamics. Moreover, the effects of field inhomogeneity can be estimated with higher precision than before. These findings are further elaborated to demonstrate their usefulness for real magnets and accelerator set ups, showing their advantages over cylindrical circular multipoles. The research findings are complemented with data obtained from the new superconducting beam guiding magnet models (SIS100) for the FAIR (Facility for Antiproton and Ion Research) project.  Lastly, the book...

Factors associated with accelerated subclinical atherosclerosis in patients with spondyloarthritis without overt cardiovascular disease.

Science.gov (United States)

Giollo, Alessandro; Dalbeni, Andrea; Cioffi, Giovanni; Ognibeni, Federica; Gatti, Davide; Idolazzi, Luca; Orsolini, Giovanni; Minuz, Pietro; Rossini, Maurizio; Fava, Cristiano; Viapiana, Ombretta

2017-11-01

Data on the progression of atherosclerosis in spondyloarthritis (SpA) are scarce, despite a high burden of cardiovascular diseases (CVD). The aim of this study was to identify the predictors of an accelerated subclinical atherosclerosis in patients with SpA. Study participants were 66 patients free of CVD classified according to ASAS criteria. The patients were evaluated at baseline and after 13.5 ± 3.6 months. Ultrasound measurements of carotid intima-media thickness (cIMT) and distensibility coefficient (cDC) were used to assess the extent of subclinical atherosclerosis. cIMT progression rate was calculated dividing the cIMT change by the time between the scans. Accelerated atherosclerosis was defined as the top cIMT progression rate quartile. At baseline, the mean Framingham Risk Score was 14 ± 11%. At follow-up, cIMT increased in 39 patients (59%; mean difference 0.01 ± 0.10; p = 0.334). Mean cIMT progression rate was 0.01 mm/year (95% CI - 0.02 to 0.03). cDC was unchanged at follow-up. Patients with accelerated atherosclerosis (n = 16) had significantly higher serum creatinine and lower glomerular filtration rate (eGFR) at baseline. In multiple logistic regression, only eGFR and the presence of syndesmophytes were associated with an accelerated atherosclerosis, independent of traditional cardiovascular risk factors. In patients with SpA without overt CV disease, a decrease in renal function and radiographic damage are conditions associated with the development of subclinical accelerated atherosclerosis. Longitudinal assessment of cIMT could be useful to better evaluate the individual CV risk of these patients improving their prognostic stratification.

Electrodeless plasma acceleration system using rotating magnetic field method

Directory of Open Access Journals (Sweden)

T. Furukawa

2017-11-01

Full Text Available We have proposed Rotating Magnetic Field (RMF acceleration method as one of electrodeless plasma accelerations. In our experimental scheme, plasma generated by an rf (radio frequency antenna, is accelerated by RMF antennas, which consist of two-pair, opposed, facing coils, and these antennas are outside of a discharge tube. Therefore, there is no wear of electrodes, degrading the propulsion performance. Here, we will introduce our RMF acceleration system developed, including the experimental device, e.g., external antennas, a tapered quartz tube, a vacuum chamber, external magnets, and a pumping system. In addition, we can change RMF operation parameters (RMF applied current IRMF and RMF current phase difference ϕ, focusing on RMF current frequency fRMF by adjusting matching conditions of RMF, and investigate the dependencies on plasma parameters (electron density ne and ion velocity vi; e.g., higher increases of ne and vi (∼360 % and 55 %, respectively than previous experimental results were obtained by decreasing fRMF from 5 MHz to 0.7 MHz, whose RMF penetration condition was better according to Milroy’s expression. Moreover, time-varying component of RMF has been measured directly to survey the penetration condition experimentally.

Formation of spectrum of accelerated particles and the hydromagnetic turbulence in the variable magnetic field

International Nuclear Information System (INIS)

Savane, Y. Sy; Diaby, I.; Faza Barry, M.; Lomonossov, V.

2002-11-01

We study the acceleration of charged particles by the variable magnetic field. The study is based on the determination of spectrum of accelerated particles and the spectrum of hydro magnetic turbulence. We plan the self-consistent system of equation and we also find out the solution of the system for the spectrum of particles and hydro magnetic turbulence with the conditions of effective acceleration in the cosmic space of solar system. (author)

Cardiovascular magnetic resonance in carotid atherosclerotic disease

Directory of Open Access Journals (Sweden)

Chen Huijun

2009-12-01

Full Text Available Abstract Atherosclerosis is a chronic, progressive, inflammatory disease affecting many vascular beds. Disease progression leads to acute cardiovascular events such as myocardial infarction, stroke and death. The diseased carotid alone is responsible for one third of the 700,000 new or recurrent strokes occurring yearly in the United States. Imaging plays an important role in the management of atherosclerosis, and cardiovascular magnetic resonance (CMR of the carotid vessel wall is one promising modality in the evaluation of patients with carotid atherosclerotic disease. Advances in carotid vessel wall CMR allow comprehensive assessment of morphology inside the wall, contributing substantial disease-specific information beyond luminal stenosis. Although carotid vessel wall CMR has not been widely used to screen for carotid atherosclerotic disease, many trials support its potential for this indication. This review summarizes the current state of knowledge regarding carotid vessel wall CMR and its potential clinical application for management of carotid atherosclerotic disease.

Application of Java Technology to Simulation of Transient Effects in Accelerator Magnets

CERN Multimedia

CERN. Geneva

2017-01-01

Superconducting magnets are one of the key building blocks of modern high-energy particle accelerators. Operating at extremely low temperatures (1.9 K), superconducting magnets produce high magnetic field needed to control the trajectory of beams travelling at nearly the speed of light. With high performance comes considerable complexity represented by several coupled physical domains characterized by multi-rate and multi-scale behaviour. The full exploitation of the LHC, as well as the design of its upgrades and future accelerators calls for more accurate simulations. With such a long-term vision in mind, the STEAM (Simulation of Transient Effects in Accelerator Magnets) project has been establish and is based on two pillars: (i) models developed with optimised solvers for particular sub-problems, (ii) coupling interfaces allowing to exchange information between the models. In order to tackle these challenges and develop a maintainable and extendable simulation framework, a team of developers implemented a ...

Accelerated two-dimensional cine DENSE cardiovascular magnetic resonance using compressed sensing and parallel imaging.

Science.gov (United States)

Chen, Xiao; Yang, Yang; Cai, Xiaoying; Auger, Daniel A; Meyer, Craig H; Salerno, Michael; Epstein, Frederick H

2016-06-14

Cine Displacement Encoding with Stimulated Echoes (DENSE) provides accurate quantitative imaging of cardiac mechanics with rapid displacement and strain analysis; however, image acquisition times are relatively long. Compressed sensing (CS) with parallel imaging (PI) can generally provide high-quality images recovered from data sampled below the Nyquist rate. The purposes of the present study were to develop CS-PI-accelerated acquisition and reconstruction methods for cine DENSE, to assess their accuracy for cardiac imaging using retrospective undersampling, and to demonstrate their feasibility for prospectively-accelerated 2D cine DENSE imaging in a single breathhold. An accelerated cine DENSE sequence with variable-density spiral k-space sampling and golden angle rotations through time was implemented. A CS method, Block LOw-rank Sparsity with Motion-guidance (BLOSM), was combined with sensitivity encoding (SENSE) for the reconstruction of under-sampled multi-coil spiral data. Seven healthy volunteers and 7 patients underwent 2D cine DENSE imaging with fully-sampled acquisitions (14-26 heartbeats in duration) and with prospectively rate-2 and rate-4 accelerated acquisitions (14 and 8 heartbeats in duration). Retrospectively- and prospectively-accelerated data were reconstructed using BLOSM-SENSE and SENSE. Image quality of retrospectively-undersampled data was quantified using the relative root mean square error (rRMSE). Myocardial displacement and circumferential strain were computed for functional assessment, and linear correlation and Bland-Altman analyses were used to compare accelerated acquisitions to fully-sampled reference datasets. For retrospectively-undersampled data, BLOSM-SENSE provided similar or lower rRMSE at rate-2 and lower rRMSE at rate-4 acceleration compared to SENSE (p cine DENSE provided good image quality and expected values of displacement and strain. BLOSM-SENSE-accelerated spiral cine DENSE imaging with 2D displacement encoding can be

Highlights of the 16th annual scientific sessions of the Society for Cardiovascular Magnetic Resonance.

Science.gov (United States)

Carpenter, John-Paul; Patel, Amit R; Fernandes, Juliano Lara

2013-07-19

The 16th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance (SCMR) took place in San Francisco, USA at the end of January 2013. With a faculty of experts from across the world, this congress provided a wealth of insight into cutting-edge research and technological development. This review article intends to provide a highlight of what represented the most significant advances in the field of cardiovascular magnetic resonance (CMR) during this year's meeting.

Cardiovascular Magnetic Resonance in Cardiology Practice: A Concise Guide to Image Acquisition and Clinical Interpretation.

Science.gov (United States)

Valbuena-López, Silvia; Hinojar, Rocío; Puntmann, Valentina O

2016-02-01

Cardiovascular magnetic resonance plays an increasingly important role in routine cardiology clinical practice. It is a versatile imaging modality that allows highly accurate, broad and in-depth assessment of cardiac function and structure and provides information on pertinent clinical questions in diseases such as ischemic heart disease, nonischemic cardiomyopathies, and heart failure, as well as allowing unique indications, such as the assessment and quantification of myocardial iron overload or infiltration. Increasing evidence for the role of cardiovascular magnetic resonance, together with the spread of knowledge and skill outside expert centers, has afforded greater access for patients and wider clinical experience. This review provides a snapshot of cardiovascular magnetic resonance in modern clinical practice by linking image acquisition and postprocessing with effective delivery of the clinical meaning. Copyright © 2015 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

Plasma acceleration by magnetic nozzles and shock waves

International Nuclear Information System (INIS)

Hattori, Kunihiko; Murakami, Fumitake; Miyazaki, Hiroyuki; Imasaki, Atsushi; Yoshinuma, Mikirou; Ando, Akira; Inutake, Masaaki

2001-01-01

We have measured axial profiles of ion acoustic Mach number, M i , of a plasma flow blowing off from an MPD (magneto-plasma-dynamic) arc-jet in various magnetic configurations. It is found that the Mach number increases in a divergent nozzle up to 3, while it stays at about unity in a uniform magnetic channel. When a magnetic bump is added in the exit of the divergent magnetic nozzle, the Mach number suddenly decreases below unity, due to an occurrence of shock wave. The subsonic flow after the shock wave is re-accelerated to a supersonic flow through a magnetic Laval nozzle. This behavior is explained well by the one-dimensional isotropic flow model. The shock wave is discussed in relation to the Rankine-Hugoniot relation. (author)

Acceleration of particles by electron plasma waves in a moderate magnetic field

International Nuclear Information System (INIS)

Smith, D.F.

1976-01-01

A general scheme is established to examine any magnetohydrodynamic (MHD) configuration for its acceleration potential including the effects of various types of plasma waves. The analysis is restricted to plasma waves in a magnetic field with electron cyclotron frequency less than, but comparable to, the electron plasma frequency (moderate field). The general role of electron plasma waves is examined in this paper independent of a specific MHD configuration or generating mechanism in the weak turbulence limit. The evolution of arbitrary wave spectra in a non-relativistic plasma is examined, and it is shown that the nonlinear process of induced scattering on the polarization clouds of ions leads to the collapse of the waves to an almost one-dimensional spectrum directed along the magnetic field. The subsequent acceleration of non-relativistic and relativistic particles is considered. It is shown for non-relativistic particles that when the wave distribution has a negative slope the acceleration is retarded for lower velocities and enhanced for higher velocities compared to acceleration by an isotropic distribution of electron plasma waves in a magnetic field. This change in behaviour is expected to affect the development of wave spectra and the subsequent acceleration spectrum. (Auth.)

Measurement of the magnetic field coefficients of particle accelerator magnets

International Nuclear Information System (INIS)

Herrera, J.; Ganetis, G.; Hogue, R.; Rogers, E.; Wanderer, P.; Willen, E.

1989-01-01

An important aspect in the development of magnets to be used in particle accelerators is the measurement of the magnetic field in the beam aperture. In general it is necessary to measure the harmonic multipoles in the dipole, quadrupole, and sextupole magnets for a series of stationary currents (plateaus). This is the case for the Superconducting Super Collider (SSC) which will be ramped to high field over a long period (/approximately/1000 sec.) and then remain on the flat top for the duration of the particle collision phase. In contrast to this mode of operation, the Booster ring being constructed for the Brookhaven AGS, will have a fast ramp rate of approximately 10 Hz. The multipole fields for these Booster magnets must therefore be determined ''on the ramp.'' In this way the effect of eddy currents will be taken into account. The measurement system which we will describe in this paper is an outgrowth of that used for the SSC dipoles. It has the capability of measuring the field multipoles on both a plateau or during a fast ramp. In addition, the same basic coil assembly is used to obtain the magnetic multipoles in dipole, quadrupole, and sextupole magnets. 2 refs., 3 figs., 1 tab

SMALL-SCALE MAGNETIC ISLANDS IN THE SOLAR WIND AND THEIR ROLE IN PARTICLE ACCELERATION. II. PARTICLE ENERGIZATION INSIDE MAGNETICALLY CONFINED CAVITIES

International Nuclear Information System (INIS)

Khabarova, Olga V.; Zank, Gary P.; Li, Gang; Le Roux, Jakobus A.; Webb, Gary M.; Malandraki, Olga E.

2016-01-01

We explore the role of heliospheric magnetic field configurations and conditions that favor the generation and confinement of small-scale magnetic islands associated with atypical energetic particle events (AEPEs) in the solar wind. Some AEPEs do not align with standard particle acceleration mechanisms, such as flare-related or simple diffusive shock acceleration processes related to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs). As we have shown recently, energetic particle flux enhancements may well originate locally and can be explained by particle acceleration in regions filled with small-scale magnetic islands with a typical width of ∼0.01 au or less, which is often observed near the heliospheric current sheet (HCS). The particle energization is a consequence of magnetic reconnection-related processes in islands experiencing either merging or contraction, observed, for example, in HCS ripples. Here we provide more observations that support the idea and the theory of particle energization produced by small-scale-flux-rope dynamics (Zank et al. and Le Roux et al.). If the particles are pre-accelerated to keV energies via classical mechanisms, they may be additionally accelerated up to 1–1.5 MeV inside magnetically confined cavities of various origins. The magnetic cavities, formed by current sheets, may occur at the interface of different streams such as CIRs and ICMEs or ICMEs and coronal hole flows. They may also form during the HCS interaction with interplanetary shocks (ISs) or CIRs/ICMEs. Particle acceleration inside magnetic cavities may explain puzzling AEPEs occurring far beyond ISs, within ICMEs, before approaching CIRs as well as between CIRs.

Cardiovascular magnetic resonance frontiers: Tissue characterisation with mapping

OpenAIRE

Schofield, R.; Bhuva, A.; Manacho, K.; Moon, J. C.

2016-01-01

The clinical use of cardiovascular magnetic resonance (CMR) imaging has expanded rapidly over the last decade. Its role in cardiac morphological and functional assessment is established, with perfusion and late gadolinium enhancement (LGE) imaging for scar increasingly used in day-to-day clinical decision making. LGE allows a virtual histological assessment of the myocardium, with the pattern of scar suggesting disease aetiology, and the extent of predicting risk. However, even combined, the ...

Cardiovascular magnetic resonance activity in the United Kingdom: a survey on behalf of the british society of cardiovascular magnetic resonance

Directory of Open Access Journals (Sweden)

Dargie Henry J

2011-10-01

Full Text Available Abstract Background The indications, complexity and capabilities of cardiovascular magnetic resonance (CMR have rapidly expanded. Whether actual service provision and training have developed in parallel is unknown. Methods We undertook a systematic telephone and postal survey of all public hospitals on behalf of the British Society of Cardiovascular Magnetic Resonance to identify all CMR providers within the United Kingdom. Results Of the 60 CMR centres identified, 88% responded to a detailed questionnaire. Services are led by cardiologists and radiologists in equal proportion, though the majority of current trainees are cardiologists. The mean number of CMR scans performed annually per centre increased by 44% over two years. This trend was consistent across centres of different scanning volumes. The commonest indication for CMR was assessment of heart failure and cardiomyopathy (39%, followed by coronary artery disease and congenital heart disease. There was striking geographical variation in CMR availability, numbers of scans performed, and distribution of trainees. Centres without on site scanning capability refer very few patients for CMR. Just over half of centres had a formal training programme, and few performed regular audit. Conclusion The number of CMR scans performed in the UK has increased dramatically in just two years. Trainees are mainly located in large volume centres and enrolled in cardiology as opposed to radiology training programmes.

The periodically pulsed mode of operation of magnet systems in particle accelerators

International Nuclear Information System (INIS)

Stange, G.

1980-01-01

Since in many applications in particle accelerator technology the beam duty factor, defined by the ratio of beam pulse length to the pulse to pulse period, is very small- typically in the order of 10 - 3 to 10 - 9 - it is interesting to operate the beam optical magnetic system in the periodically pulsed mode as well. Thus, by reducing the average Ohmic losses, it is possible to save energy and material. The pulsed mode of operation of magnet systems is especially adapted to those of linear accelerators and their beam transport systems, since linear accelerators are exclusively operated in this mode. But it is equally suitable for transport systems between cyclic accelerators and large storage rings as they are under development at present. (orig./WL) [de

Magnetic Reconnection and Particle Acceleration in the Solar Corona

Science.gov (United States)

Neukirch, Thomas

Reconnection plays a major role for the magnetic activity of the solar atmosphere, for example solar flares. An interesting open problem is how magnetic reconnection acts to redistribute the stored magnetic energy released during an eruption into other energy forms, e.g. gener-ating bulk flows, plasma heating and non-thermal energetic particles. In particular, finding a theoretical explanation for the observed acceleration of a large number of charged particles to high energies during solar flares is presently one of the most challenging problems in solar physics. One difficulty is the vast difference between the microscopic (kinetic) and the macro-scopic (MHD) scales involved. Whereas the phenomena observed to occur on large scales are reasonably well explained by the so-called standard model, this does not seem to be the case for the small-scale (kinetic) aspects of flares. Over the past years, observations, in particular by RHESSI, have provided evidence that a naive interpretation of the data in terms of the standard solar flare/thick target model is problematic. As a consequence, the role played by magnetic reconnection in the particle acceleration process during solar flares may have to be reconsidered.

Conduction cooled high temperature superconducting dipole magnet for accelerator applications

DEFF Research Database (Denmark)

Zangenberg, N.; Nielsen, G.; Hauge, N.

2012-01-01

A 3T proof-of-principle dipole magnet for accelerator applications, based on 2nd generation high temperature superconducting tape was designed, built, and tested by a consortium under the lead of Danfysik. The magnet was designed to have a straight, circular bore with a good field region of radius...

Magnetic field alignment for a 20 MeV linear induction accelerator

International Nuclear Information System (INIS)

Zhang Wenwei; Pan Haifeng; Li Hong; Liu Yunlong; Zhang Linwen

2002-01-01

'Dragon-1' accelerator now is being constructed in CAEP. It will produce high current pulse electron beams. The main components of the accelerator include 72 induction accelerating cells and 18 connection cells with ports for beam di gnostic hardware and vacuum pump. In order to acquire high quality beams, a lot of problems have to be addressed such as to reduce the emittance, to control the increase of corkscrew and so on. The alignment of the focus magnetic field is the most concerned. A laser track has been used for mechanical alignment, magnetic alignment is performed by using pulsed-wire technique, and the natural tilt errors is corrected by a pair of steering coil, which is located inside the cell

Electron Surfing Acceleration in Magnetic Reconnection

OpenAIRE

Hoshino, Masahiro

2005-01-01

We discuss that energetic electrons are generated near the X-type magnetic reconnection region due to a surfing acceleration mechanism. In a thin plasma sheet, the polarization electric fields pointing towards the neutral sheet are induced around the boundary between the lobe and plasma sheet in association with the Hall electric current. By using a particle-in-cell simulation, we demonstrate that the polarization electric fields are strongly enhanced in an externally driven reconnection syst...

Stability of superconducting Rutherford cables for accelerator magnets

NARCIS (Netherlands)

Willering, G.P.

2009-01-01

The stability of superconducting magnets has a high priority for particle accelerators, since the operational time and operational collision energy depend strongly on it. Local heat dissipation due to beam loss and conductor movement is inevitable, causing local hot spots in the conductor, possibly

Technological Innovations in Magnetic Resonance for Early Detection of Cardiovascular Diseases.

Science.gov (United States)

Santarelli, Maria F; Positano, Vincenzo; Martini, Nicola; Valvano, Giuseppe; Landini, Luigi

2016-01-01

Most recent technical innovations in cardiovascular MR imaging (CMRI) are presented in this review. They include hardware and software developments, and novelties in parametric mapping. All these recent improvements lead to high spatial and temporal resolution and quantitative information on the heart structure and function. They make it achievable ambitious goals in the field of magnetic resonance, such as the early detection of cardiovascular pathologies. In this review article, we present recent innovations in CMRI, emphasizing the progresses performed and the solutions proposed to some yet opened technical problems.

Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets

International Nuclear Information System (INIS)

Wang, X.; Ambrosio, G.; Chlachidze, G.; Collings, E. W.; Dietderich, D. R.; DiMarco, J.; Felice, H.; Ghosh, A. K.; Godeke, A.; Gourlay, S. A.; Marchevsky, M.; Prestemon, S. O.; Sabbi, G.; Sumption, M. D.; Velev, G. V.; Xu, X.; Zlobin, A. V.

2015-01-01

Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3 Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnet designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed

Kinetic Simulations of Plasma Energization and Particle Acceleration in Interacting Magnetic Flux Ropes

Science.gov (United States)

Du, S.; Guo, F.; Zank, G. P.; Li, X.; Stanier, A.

2017-12-01

The interaction between magnetic flux ropes has been suggested as a process that leads to efficient plasma energization and particle acceleration (e.g., Drake et al. 2013; Zank et al. 2014). However, the underlying plasma dynamics and acceleration mechanisms are subject to examination of numerical simulations. As a first step of this effort, we carry out 2D fully kinetic simulations using the VPIC code to study the plasma energization and particle acceleration during coalescence of two magnetic flux ropes. Our analysis shows that the reconnection electric field and compression effect are important in plasma energization. The results may help understand the energization process associated with magnetic flux ropes frequently observed in the solar wind near the heliospheric current sheet.

Cardiovascular magnetic resonance in hypertrophic cardiomyopathy and infiltrative cardiomyopathy

OpenAIRE

Schofield, Rebecca; Manacho, Katia; Castelletti, Silvia; Moon, James C.

2016-01-01

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. Cardiac imaging plays a key role in the diagnosis and management, with cardiovascular magnetic resonance (CMR) an important modality. CMR provides a number of different techniques in one examination: structure and function, flow imaging and tissue characterisation particularly with the late gadolinium enhancement (LGE) technique. Other techniques include vasodilator perfusion, mapping (especially T1 mapping and ex...

Modeling of electron cyclotron resonance acceleration in a stationary inhomogeneous magnetic field

Directory of Open Access Journals (Sweden)

Valeri D. Dougar-Jabon

2008-04-01

Full Text Available In this paper, the cyclotron autoresonance acceleration of electrons in a stationary inhomogeneous magnetic field is studied. The trajectory and energy of electrons are found through a numerical solution of the relativistic Newton-Lorentz equation by a finite difference method. The electrons move along a TE_{112} cylinder cavity in a steady-state magnetic field whose axis coincides with the cavity axis. The magnetic field profile is such that it keeps the phase difference between the electric microwave field and the electron velocity vector within the acceleration phase band. The microwaves amplitude of 6  kV/cm is used for numerical calculations. It is shown that an electron with an initial longitudinal energy of 8 keV can be accelerated up to 260 keV by 2.45 GHz microwaves at a distance of 17 cm.

Acceleration of cardiovascular MRI using parallel imaging: basic principles, practical considerations, clinical applications and future directions

International Nuclear Information System (INIS)

Niendorf, T.; Sodickson, D.

2006-01-01

Cardiovascular Magnetic Resonance (CVMR) imaging has proven to be of clinical value for non-invasive diagnostic imaging of cardiovascular diseases. CVMR requires rapid imaging; however, the speed of conventional MRI is fundamentally limited due to its sequential approach to image acquisition, in which data points are collected one after the other in the presence of sequentially-applied magnetic field gradients and radiofrequency coils to acquire multiple data points simultaneously, and thereby to increase imaging speed and efficiency beyond the limits of purely gradient-based approaches. The resulting improvements in imaging speed can be used in various ways, including shortening long examinations, improving spatial resolution and anatomic coverage, improving temporal resolution, enhancing image quality, overcoming physiological constraints, detecting and correcting for physiologic motion, and streamlining work flow. Examples of these strategies will be provided in this review, after some of the fundamentals of parallel imaging methods now in use for cardiovascular MRI are outlined. The emphasis will rest upon basic principles and clinical state-of-the art cardiovascular MRI applications. In addition, practical aspects such as signal-to-noise ratio considerations, tailored parallel imaging protocols and potential artifacts will be discussed, and current trends and future directions will be explored. (orig.)

Characteristics of the magnetic wall reflection model on ion acceleration in gas-puff z pinch

International Nuclear Information System (INIS)

Nishio, M.; Takasugi, K.

2013-01-01

The magnetic wall reflection model was examined with the numerical simulation of the trajectory calculation of particles. This model is for the ions accelerated by some current-independent mechanism. The trajectory calculation showed angle dependency of highest velocities of accelerated particles. This characteristics is of the magnetic wall reflection model, not of the other current-independent acceleration mechanism. Thomson parabola measurements of accelerated ions produced in the gas-puff z-pinch experiments were carried out for the verification of the angle dependency. (author)

Permanent Magnets In Steerers Of The Beam Extracted From The Electron Accelerator

CERN Document Server

Dovbnya, A N; Shendrik, V A; Tolstoj, A E

2004-01-01

The results of test bench simulation and magnetic measurements were used to develop and manufacture "dipole magnet"-type units with a constant field of intensity up to 1.8 kOe in the working gap, 3 to 3.5 cm in height. The operating experience at the technological accelerators has shown that these devices are convenient in service, are easy-to-transport and can be used for solving the various problems in electron beam formation and steering at the exit of the accelerator.

A Novel Permanent Magnetic Angular Acceleration Sensor

Directory of Open Access Journals (Sweden)

Hao Zhao

2015-07-01

Full Text Available Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s−2. Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability.

Quantification of right and left ventricular function by cardiovascular magnetic resonance

International Nuclear Information System (INIS)

Bellenger, N.G.; Smith, G.C.; Pennell, D.J.; Grothues, F.

2000-01-01

Cardiac dysfunction is a major cause of cardiovascular morbidity and mortality. Accurate and reproducible assessment of cardiac function is essential for the diagnosis, the assessment of prognosis and evaluation of a patient's response to therapy. Cardiovascular magnetic resonance (CMR) provides a measure of global and regional function that is not only accurate and reproducible but is noninvasive, free of ionising radiation, and independent of the geometric assumptions and acoustic windows that limit echocardiography. With the advent of faster scanners, automated analysis, increasing availability and reducing costs, CMR is fast becoming a clinically tenable reference standard for the measurement of cardiac function. (orig.) [de

3-D computations and measurements of accelerator magnets for the APS

International Nuclear Information System (INIS)

Turner, L.R.; Kim, S.H.; Kim, K.

1993-01-01

The Advanced Photon Source (APS), now under construction at Argonne National Laboratory (ANL), requires dipole, quadrupole, sextupole, and corrector magnets for each of its circular accelerator systems. Three-dimensional (3-D) field computations are needed to eliminate unwanted multipole fields from the ends of long quadrupole and dipole magnets and to guarantee that the flux levels in the poles of short magnets will not cause saturation. Measurements of the magnets show good agreement with the computations

Procedures for measuring the electrical properties of superconductors for accelerator magnets

International Nuclear Information System (INIS)

Sampson, W.B.

1986-01-01

There are three important electrical properties associated with the superconductor used to fabricate accelerator magnets. The most important is the critical current since this determines the performance potential of the magnet. The normal state resistivity and the volume magnetization are the other principal electrical parameters. In this report methods for measuring these parameters are presented and procedures for including self field effect and magnetoresistance are discussed

Electron ring diagnostics with magnetic probes during roll-out and acceleration

International Nuclear Information System (INIS)

Schumacher, U.; Ulrich, M.

1976-03-01

Different methods using magnetic field probes to determine the properties of electron rings during their compression, roll-out and acceleration are presented. The results of the measurements of the electron number and the axial velocity and acceleration of the rings, as obtained with the various diagnostic devices, are discussed and compared. (orig.) [de

The Role of Cardiovascular Magnetic Resonance Imaging in Heart Failure.

Science.gov (United States)

Peterzan, Mark A; Rider, Oliver J; Anderson, Lisa J

2016-11-01

Cardiovascular imaging is key for the assessment of patients with heart failure. Today, cardiovascular magnetic resonance imaging plays an established role in the assessment of patients with suspected and confirmed heart failure syndromes, in particular identifying aetiology. Its role in informing prognosis and guiding decisions around therapy are evolving. Key strengths include its accuracy; reproducibility; unrestricted field of view; lack of radiation; multiple abilities to characterise myocardial tissue, thrombus and scar; as well as unparalleled assessment of left and right ventricular volumes. T2* has an established role in the assessment and follow-up of iron overload cardiomyopathy and a role for T1 in specific therapies for cardiac amyloid and Anderson-Fabry disease is emerging.

Magnetic field structure of the U-120 cyclotron for heavy ions acceleration

International Nuclear Information System (INIS)

Schwabe, J.; Starzewski, J.

1975-01-01

The proposed magnetic structure makes possible the acceleration, in quasi-isochronous conditions, of ions having the ratio Z/A=0,665 - 0,1 on the U-120 cyclotron in Cracow. Simultaneously, significant improvement of the accelerated beam emittance, decrease in energy scattering down to a value of about 10 -3 , and an increase in the maximum accelerated beam energy may be obtained. (author)

Particle acceleration through the resonance of high magnetic field and high frequency electromagnetic wave

International Nuclear Information System (INIS)

Hong, Liu; He, X.T.; Chen, S.G.; Zhang, W.Y.; He, X.T.; Hong, Liu

2004-01-01

We propose a new particle acceleration mechanism. Electrons can be accelerated to relativistic energy within a few electromagnetic wave cycles through the mechanism which is named electromagnetic and magnetic field resonance acceleration (EMRA). We find that the electron acceleration depends not only on the electromagnetic wave intensity, but also on the ratio between electron Larmor frequency and electromagnetic wave frequency. As the ratio approaches to unity, a clear resonance peak is observed, corresponding to the EMRA. Near the resonance regime, the strong magnetic fields still affect the electron acceleration dramatically. We derive an approximate analytical solution of the relativistic electron energy in adiabatic limit, which provides a full understanding of this phenomenon. In typical parameters of pulsar magnetospheres, the mechanism allows particles to increase their energies through the resonance of high magnetic field and high frequency electromagnetic wave in each electromagnetic wave period. The energy spectra of the accelerated particles exhibit the synchrotron radiation behavior. These can help to understand the remaining emission of high energy electron from radio pulsar within supernova remnant. The other potential application of our theory in fast ignition scheme of inertial confinement fusion is also discussed. (authors)

Nb3Sn accelerator magnet technology R&D at Fermilab

Energy Technology Data Exchange (ETDEWEB)

Zlobin, A.V.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; Carcagno, R.; Chlachidze, G.; DiMarco, J.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; /Fermilab

2007-06-01

Accelerator magnets based on Nb{sub 3}Sn superconductor are being developed at Fermilab. Six nearly identical 1-m long dipole models and several mirror configurations were built and tested demonstrating magnet performance parameters and their reproducibility. The technology scale up program has started by building and testing long dipole coils. The results of this work are reported in the paper.

A hybrid data acquisition system for magnetic measurements of accelerator magnets

International Nuclear Information System (INIS)

Wang, X.; Hafalia, R.; Joseph, J.; Lizarazo, J.; Martchevsky, M.; Sabbi, G.L.

2011-01-01

A hybrid data acquisition system was developed for magnetic measurement of superconducting accelerator magnets at LBNL. It consists of a National Instruments dynamic signal acquisition (DSA) card and two Metrolab fast digital integrator (FDI) cards. The DSA card records the induced voltage signals from the rotating probe while the FDI cards records the flux increment integrated over a certain angular step. This allows the comparison of the measurements performed with two cards. In this note, the setup and test of the system is summarized. With a probe rotating at a speed of 0.5 Hz, the multipole coefficients of two magnets were measured with the hybrid system. The coefficients from the DSA and FDI cards agree with each other, indicating that the numerical integration of the raw voltage acquired by the DSA card is comparable to the performance of the FDI card in the current measurement setup.

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

Science.gov (United States)

Danby, Gordon T.; Jackson, John W.

1991-01-01

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.

Quench behavior of a superconducting accelerator magnet

International Nuclear Information System (INIS)

McInturff, A.D.; Sampson, W.B.; Garber, M.; Dahl, P.F.

1980-01-01

Data are presented on the minimum energy required to cause quenches to propagate in an accelerator dipole magnet. The amount of stored energy dissipated into the magnet was measured as a function of dipole excitation current. This in turn determines the maximum coil temperature reached in a given magnet. Quench velocities in the longitudinal direction of the conductor were as high as 11m/sec. The azimuthal velocities or turn to turn velocities were found to be a function of the number of fiberglass layers of insulation that the quench had to cross and were on the order of a few tens of centimeters/sec. The field shape of a given magnet was found to be unchanged for more than 100 quenches. The coil to coil connection and inter-coil splice resistances were found to be less than a namo-ohm and therefore of litle consequence in the cryogenic load considerations. No definitive answers were found on how to decrease the rate of training (130 Gauss/Quench average) required from 4.OT to 5.1T

Accelerator Quality HTS Dipole Magnet Demonstrator designs for the EuCARD-2, 5 Tesla 40 mm Clear Aperture Magnet

CERN Document Server

Kirby, G; Ballarino, A; Bottura, L; Chouika, N; Clement, S; Datskov, V; Fajardo, L; Fleiter, J; Gauthier, R; Lambert, L; Lopes, M; Perez, J; DeRijk, G; Rijllart, A; Rossi, L; Ten Kate, H; Durante, M; Fazilleau, P; Lorin, C; Haro, E; Stenvall, A; Caspi, S; Marchevsky, M; Goldacker, W; Kario, A

2014-01-01

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.

Accelerator Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2, 5 Tesla 40 mm Clear Aperture Magnet

CERN Document Server

Kirby, G A; Ballarino, A; Bottura, L; Chouika, N; Clement, S; Datskov, V; Fajardo, L; Fleiter, J; Gauthier, R; Gentini, L; Lambert, L; Lopes, M; Perez, J C; de Rijk, G; Rijllart, A; Rossi, L; ten Kate, H; Durante, M; Fazilleau, P; Lorin, C; Härö, E; Stenvall, A; Caspi, S; Marchevsky, M; Goldacker, W; Kario, A

2015-01-01

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.

SMALL-SCALE MAGNETIC ISLANDS IN THE SOLAR WIND AND THEIR ROLE IN PARTICLE ACCELERATION. I. DYNAMICS OF MAGNETIC ISLANDS NEAR THE HELIOSPHERIC CURRENT SHEET

Energy Technology Data Exchange (ETDEWEB)

Khabarova, O. [Heliophysical Laboratory, Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation RAS (IZMIRAN), Troitsk, Moscow 142190 (Russian Federation); Zank, G. P.; Li, G.; Roux, J. A. le; Webb, G. M.; Dosch, A. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Malandraki, O. E. [IAASARS, National Observatory of Athens, GR-15236 Penteli (Greece)

2015-08-01

Increases of ion fluxes in the keV–MeV range are sometimes observed near the heliospheric current sheet (HCS) during periods when other sources are absent. These resemble solar energetic particle events, but the events are weaker and apparently local. Conventional explanations based on either shock acceleration of charged particles or particle acceleration due to magnetic reconnection at interplanetary current sheets (CSs) are not persuasive. We suggest instead that recurrent magnetic reconnection occurs at the HCS and smaller CSs in the solar wind, a consequence of which is particle energization by the dynamically evolving secondary CSs and magnetic islands. The effectiveness of the trapping and acceleration process associated with magnetic islands depends in part on the topology of the HCS. We show that the HCS possesses ripples superimposed on the large-scale flat or wavy structure. We conjecture that the ripples can efficiently confine plasma and provide tokamak-like conditions that are favorable for the appearance of small-scale magnetic islands that merge and/or contract. Particles trapped in the vicinity of merging islands and experiencing multiple small-scale reconnection events are accelerated by the induced electric field and experience first-order Fermi acceleration in contracting magnetic islands according to the transport theory of Zank et al. We present multi-spacecraft observations of magnetic island merging and particle energization in the absence of other sources, providing support for theory and simulations that show particle energization by reconnection related processes of magnetic island merging and contraction.

Electron Fermi acceleration in collapsing magnetic traps: Computational and analytical models

International Nuclear Information System (INIS)

Gisler, G.; Lemons, D.

1990-01-01

The authors consider the heating and acceleration of electrons trapped on magnetic field lines between approaching magnetic mirrors. Such a collapsing magnetic trap and consequent electron energization can occur whenever a curved (or straight) flux tube drifts into a relatively straight (or curved) perpendicular shock. The relativistic, three-dimensional, collisionless test particle simulations show that an initial thermal electron distribution is bulk heated while a few individual electrons are accelerated to many times their original energy before they escape the trap. Upstream field-aligned beams and downstream pancake distributions perpendicular to the field are predicted. In the appropriate limit the simulation results agree well with a nonrelativistic analytic model of the distribution of escaping electrons which is based on the first adiabatic invariant and energy conservation between collisions with the mirrors. Space science and astrophysical applications are discussed

Qualitative models of magnetic field accelerated propagation in a plasma due to the Hall effect

International Nuclear Information System (INIS)

Kukushkin, A.B.; Cherepanov, K.V.

2000-01-01

Two qualitatively new models of accelerated magnetic field propagation (relative to normal diffusion) in a plasma due to the Hall effect are developed within the frames of the electron magnetic hydrodynamics. The first model is based on a simple hydrodynamic approach, which, in particular, reproduces the number of known theoretical results. The second one makes it possible to obtain exact analytical description of the basic characteristics of the magnetic field accelerated propagation in a inhomogeneous iso-thermic plasma, namely, the magnetic field front and its effective width [ru

Particle acceleration at the magnetic poles of a neutron star

International Nuclear Information System (INIS)

Jones, P.B.

1977-01-01

The magnetic conversion of a photon in a neutron star magnetosphere near one of the magnetic poles is followed by acceleration of the electron and positron to ultra-relativistic energies. The positron moves along open magnetic flux lines to the light cylinder. The electron incident on the stellar surface produces an electromagnetic shower. Following a comment by Cheng and Ruderman (Astrophys.J.;214:598 (1977)), an order of magnitude estimate has been made of the spectrum of backward moving photons created in the electron shower. The most important source of photons is shown to be the formation of the giant dipole state in Fe 56 . Under the assumption that the surface magnetic flux density exceeds 10 12 G, the photons have, with high probability, mean free paths for magnetic conversion in the magnetosphere of 1 4 cm. An equation for the maximum acceleratin potential has been obtained in a one-dimensional model of pair creation and electron multiplication based on this photon source. The model has been applied to the phenomenon of subpulse drift in pulsars. The plasma accelerated at the magnetic pole has three components; positrons, protons and light nuclei (Z < approximately 6) formed by spallation, and iron group nuclei. Equations determining their relative fluxes have been found. The light nuclei include those with Z = 3 to 5, usually considered to be present in galactic cosmic rays only as a result of the interaction of heavier nuclei with the interstellar medium. (author)

A New Concept of Controller for Accelerators' Magnet Power Supplies

Science.gov (United States)

Visintini, Roberto; Cleva, Stefano; Cautero, Marco; Ciesla, Tomasz

2016-04-01

The complexity of a particle accelerator implies the remote control of very large numbers of devices, with many different typologies, either distributed along the accelerator or concentrated in locations, often far away from each other. Local and global control systems handle the devices through dedicated communication channels and interfaces. Each controlled device is practically a “smart node” performing a specific task. In addition, very often, those tasks are managed in real-time mode. The performances required to the control interface has an influence on the cost of the distributed nodes as well as on their hardware and software implementation. In large facilities (e.g. CERN) the “smart nodes” derive from specific in-house developments. Alternatively, it is possible to find on the market commercial devices, whose performances (and prices) are spread over a broad range, and spanning from proprietary design (customizable to the user's needs) to open source/design. In this paper, we will describe some applications of smart nodes in the particle accelerators field, with special focus on the power supplies for magnets. In modern accelerators, in fact, magnets and their associated power supplies constitute systems distributed along the accelerator itself, and strongly interfaced with the remote control system as well as with more specific (and often more demanding) orbit/trajectory feedback systems. We will give examples of actual systems, installed and operational on two light sources, Elettra and FERMI, located in the Elettra Research Center in Trieste, Italy.

Precision Magnet Measurements for X-Band Accelerator Quadrupole Triplets

Energy Technology Data Exchange (ETDEWEB)

Marsh, R A; Anderson, S G; Armstrong, J P

2012-05-16

An X-band test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray (MEGa-Ray) technology at LLNL. Beamline magnets will include an emittance compensation solenoid, windowpane steering dipoles, and quadrupole magnets. Demanding tolerances have been placed on the alignment of these magnets, which directly affects the electron bunch beam quality. A magnet mapping system has been established at LLNL in order to ensure the delivered magnets match their field specification, and the mountings are aligned and capable of reaching the specified alignment tolerances. The magnet measurement system will be described which uses a 3-axis Lakeshore gauss probe mounted on a 3-axis translation stage. Alignment accuracy and precision will be discussed, as well as centering measurements and analysis. The dependence on data analysis over direct multi-pole measurement allows a significant improvement in useful alignment information. Detailed analysis of measurements on the beamline quadrupoles will be discussed, including multi-pole content both from alignment of the magnets, and the intrinsic level of multi-pole magnetic field.

Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

Science.gov (United States)

Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J.

2016-01-01

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

Use of permanent magnets in accelerator technology: Present and future

International Nuclear Information System (INIS)

Halbach, K.

1987-05-01

This report is a collection of viewgraphs discussing accelerator magnets. Permanent magnet systems have some generic properties that, under some circumstances, make them not only mildly preferable over electromagnets, but make it possible to do things that can not be done with any other technology. After a general discussion of these generic advantages, some specific permanent magnet systems will be described. Special emphasis will be placed on systems that have now, or are likely to have in the future, a significant impact on how some materials research is conducted. 4 refs., 33 figs

2-D and 3-D computations of curved accelerator magnets

International Nuclear Information System (INIS)

Turner, L.R.

1991-01-01

In order to save computer memory, a long accelerator magnet may be computed by treating the long central region and the end regions separately. The dipole magnets for the injector synchrotron of the Advanced Photon Source (APS), now under construction at Argonne National Laboratory (ANL), employ magnet iron consisting of parallel laminations, stacked with a uniform radius of curvature of 33.379 m. Laplace's equation for the magnetic scalar potential has a different form for a straight magnet (x-y coordinates), a magnet with surfaces curved about a common center (r-θ coordinates), and a magnet with parallel laminations like the APS injector dipole. Yet pseudo 2-D computations for the three geometries give basically identical results, even for a much more strongly curved magnet. Hence 2-D (x-y) computations of the central region and 3-D computations of the end regions can be combined to determine the overall magnetic behavior of the magnets. 1 ref., 6 figs

Design of MgB2 superconducting dipole magnet for particle beam transport in accelerators

DEFF Research Database (Denmark)

Abrahamsen, A.B.; Zangenberg, N.; Baurichter, A.

2006-01-01

for the collaborating company Danfysik A/S, which has a strongtradition in building resistive magnets for particle accelerators[4]. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European...... in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the criticalcurrent density of primarily MgB2 will be compared with current density determined by specifications similar to the Tevatron...... accelerator, B = 4:4 Tesla and coil aperture D = 76 mm [6], which has been identified by Danfysik A/S as interesting. It isconcluded that MgB2 is useful for the dipole application and construction of a small test coil of one half of the magnet is planned in 2007....

Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

Science.gov (United States)

Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Development of scanning magnet for 750 keV DC accelerator

International Nuclear Information System (INIS)

Pramod, R.; Pankaj Kumar; Venkateswaran, S.V.; Bapna, S.C.

2003-01-01

In the radiation processing technologies, the surface to be irradiated has to be as large as possible, but keeping a good uniformity of the absorbed dose. To attain such a goal, the beam should be scanned in a plane perpendicular on the displacement of the conveyor belt. Therefore, scanning magnets are necessary. A scanning magnet should ensure the homogeneity of the absorbed dose (and, similarly, of the beam current distribution) on the items to be irradiated. In this paper some simple relations needed in the design of the scanning magnets are deduced, the design and fabrication aspects of the scanning magnet for the 750 keV DC accelerator are discussed

An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

Energy Technology Data Exchange (ETDEWEB)

Masters, A.; Dougherty, M. K. [The Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Sulaiman, A. H. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Stawarz, Ł. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Krakow (Poland); Reville, B. [School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Sergis, N. [Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, 11527 Athens (Greece); Fujimoto, M. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Burgess, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom); Coates, A. J., E-mail: a.masters@imperial.ac.uk [Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom)

2017-07-10

A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream–downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ∼100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.

Grid Connected Power Supplies for Particle Accelerator Magnets

DEFF Research Database (Denmark)

Nielsen, Rasmus Ørndrup

Power supplies play a large role in particle accelerators, for creating, accelerating, steering and shaping the beam. This thesis covers the power supplies for steering and shaping the beam, namely the magnet power supplies. These power supplies have a special set of requirements regarding output...... on this topology is constructed using a single power module on the grid side of the transformer, consisting of a boost rectifier and a dual half-bridge isolated DC/DC converter. It is shown that it is possible to create a power supply using a single module and that this approach can lead to improved layout...... and smaller converter size. A high efficiency converter based on Silicon Carbide switching devices is also presented exhibiting above 96 % efficiency for the entire power range. Finally reliability issues are considered as the reliability of a particle accelerator supply is of utmost importance. Particle...

A procedure for combining rotating-coil measurements of large-aperture accelerator magnets

Energy Technology Data Exchange (ETDEWEB)

Köster, Oliver, E-mail: oliver.koester@cern.ch; Fiscarelli, Lucio, E-mail: lucio.fiscarelli@cern.ch; Russenschuck, Stephan, E-mail: stephan.russenschuck@cern.ch

2016-05-11

The rotating search coil is a precise and widely used tool for measuring the magnetic field harmonics of accelerator magnets. This paper deals with combining several such multipole measurements, in order to cover magnet apertures largely exceeding the diameter of the available search coil. The method relies on the scaling laws for multipole coefficients and on the method of analytic continuation along zero-homotopic paths. By acquiring several measurements of the integrated magnetic flux density at different transverse positions within the bore of the accelerator magnet, the uncertainty on the field harmonics can be reduced at the expense of tight tolerances on the positioning. These positioning tolerances can be kept under control by mounting the rotating coil and its motor-drive unit on precision alignment stages. Therefore, the proposed technique is able to yield even more precise results for the higher-order field components than a dedicated rotating search coil of larger diameter. Moreover, the versatility of the measurement bench is enhanced by avoiding the construction of rotating search coils of different measurement radii.

Current variables, definitions and endpoints of the European Cardiovascular Magnetic Resonance Registry

Directory of Open Access Journals (Sweden)

Schwitter Juerg

2009-11-01

Full Text Available Abstract Background Cardiovascular Magnetic Resonance (CMR is increasingly used in daily clinical practice. However, little is known about its clinical utility such as image quality, safety and impact on patient management. In addition, there is limited information about the potential of CMR to acquire prognostic information. Methods The European Cardiovascular Magnetic Resonance Registry (EuroCMR Registry will consist of two parts: 1 Multicenter registry with consecutive enrolment of patients scanned in all participating European CMR centres using web based online case record forms. 2 Prospective clinical follow up of patients with suspected coronary artery disease (CAD and hypertrophic cardiomyopathy (HCM every 12 months after enrolment to assess prognostic data. Conclusion The EuroCMR Registry offers an opportunity to provide information about the clinical utility of routine CMR in a large number of cases and a diverse population. Furthermore it has the potential to gather information about the prognostic value of CMR in specific patient populations.

ESCAR, tests of superconducting bending magnets at the accelerator site

International Nuclear Information System (INIS)

Gilbert, W.S.; Lambertson, G.R.; Meuser, R.B.; Rechen, J.B.

1979-03-01

ESCAR (Experimental Superconducting Accelerator Ring) was conceived as a project in accelerator technology development which would provide data and experience to insure that planning for larger superconducting synchrotrons would proceed in a knowledgeable and responsible manner. It was to consist of the fabrication and operation of a relatively small proton synchrotron and storage ring with superconducting magnet elements for all of the main ring. The project was funded and design work began in July 1974. During the next two years it became increasingly apparent that the funding rate was directly limiting the rate of completion of ESCAR and that an intermediate goal, a test of the unconventional aspects of the project, was desirable. To that end, twelve dipole bending magnets, one-half of those required for the total ring, were installed at the site along with the 1500 watt helium refrigerator, cryogenic distribution system, electrical power supplies, vacuum systems, and necessary instrumentation. This truncated system was put through an extended series of tests which were completed in June 1978 at which time the ESCAR Project was terminated. ESCAR, and the dipole magnets have been described previously. The results of the systems tests have also been reported. The tests involving the dipole magnets are described

Nb3Sn accelerator magnet technology R and D at Fermilab

International Nuclear Information System (INIS)

Zlobin, A.V.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; Carcagno, R.; Chlachidze, G.; DiMarco, J.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Fermilab

2007-01-01

Accelerator magnets based on Nb 3 Sn superconductor are being developed at Fermilab. Six nearly identical 1-m long dipole models and several mirror configurations were built and tested demonstrating magnet performance parameters and their reproducibility. The technology scale up program has started by building and testing long dipole coils. The results of this work are reported in the paper

Non-cardiovascular findings in clinical cardiovascular magnetic resonance imaging in children

International Nuclear Information System (INIS)

Ghadimi Mahani, Maryam; Morani, Ajaykumar C.; Lu, Jimmy C.; Dorfman, Adam L.; Fazeli Dehkordy, Soudabeh; Jeph, Sunil; Agarwal, Prachi P.

2016-01-01

With increasing use of pediatric cardiovascular MRI, it is important for all imagers to become familiar with the spectrum of non-cardiovascular imaging findings that can be encountered. This study aims to ascertain the prevalence and nature of these findings in pediatric cardiovascular MRIs performed at our institution. We retrospectively evaluated reports of all cardiovascular MRI studies performed at our institute from January 2008 to October 2012 in patients younger than18 years. Most studies (98%) were jointly interpreted by a pediatric cardiologist and a radiologist. We reviewed the electronic medical records of all cases with non-cardiovascular findings, defined as any imaging finding outside the cardiovascular system. Non-cardiovascular findings were classified into significant and non-significant, based on whether they were known at the time of imaging or they required additional workup or a change in management. In 849 consecutive studies (mean age 9.7 ± 6.3 years), 145 non-cardiovascular findings were found in 140 studies (16.5% of total studies). Overall, 51.0% (74/145) of non-cardiovascular findings were in the abdomen, 30.3% (44/145) were in the chest, and 18.6% (27/145) were in the spine. A total of 19 significant non-cardiovascular findings were observed in 19 studies in individual patients (2.2% of total studies, 47% male, mean age 5.9 ± 6.7 years). Significant non-cardiovascular findings included hepatic adenoma, arterially enhancing focal liver lesions, asplenia, solitary kidney, pelvicaliectasis, renal cystic diseases, gastric distention, adrenal hemorrhage, lung hypoplasia, air space disease, bronchial narrowing, pneumomediastinum and retained surgical sponge. Non-cardiovascular findings were seen in 16.5% of cardiovascular MRI studies in children, of which 2.2% were clinically significant findings. Prevalence and nature of these non-cardiovascular findings are different from those reported in adults. Attention to these findings is important

Non-cardiovascular findings in clinical cardiovascular magnetic resonance imaging in children

Energy Technology Data Exchange (ETDEWEB)

Ghadimi Mahani, Maryam [University of Michigan Health System, C.S. Mott Children' s Hospital, Department of Radiology, Section of Pediatric Radiology, Ann Arbor, MI (United States); Morani, Ajaykumar C. [The University of Texas MD Anderson Cancer Center, Department of Diagnostic Radiology, Houston, TX (United States); Lu, Jimmy C.; Dorfman, Adam L. [University of Michigan Health System, C.S. Mott Children' s Hospital, Department of Pediatrics and Communicable Diseases, Division of Pediatric Cardiology, Ann Arbor, MI (United States); Fazeli Dehkordy, Soudabeh [University of Michigan Health System, C.S. Mott Children' s Hospital, Department of Radiology, Section of Pediatric Radiology, Ann Arbor, MI (United States); Providence Hospital and Medical Centers, Department of Graduate Medical Education, Southfield, MI (United States); Jeph, Sunil [The University of Texas MD Anderson Cancer Center, Department of Diagnostic Radiology, Houston, TX (United States); Geisinger Medical Center, Department of Radiology, Danville, PA (United States); Agarwal, Prachi P. [University of Michigan Health System, Department of Radiology, Division of Cardiothoracic Radiology, Ann Arbor, MI (United States)

2016-04-15

With increasing use of pediatric cardiovascular MRI, it is important for all imagers to become familiar with the spectrum of non-cardiovascular imaging findings that can be encountered. This study aims to ascertain the prevalence and nature of these findings in pediatric cardiovascular MRIs performed at our institution. We retrospectively evaluated reports of all cardiovascular MRI studies performed at our institute from January 2008 to October 2012 in patients younger than18 years. Most studies (98%) were jointly interpreted by a pediatric cardiologist and a radiologist. We reviewed the electronic medical records of all cases with non-cardiovascular findings, defined as any imaging finding outside the cardiovascular system. Non-cardiovascular findings were classified into significant and non-significant, based on whether they were known at the time of imaging or they required additional workup or a change in management. In 849 consecutive studies (mean age 9.7 ± 6.3 years), 145 non-cardiovascular findings were found in 140 studies (16.5% of total studies). Overall, 51.0% (74/145) of non-cardiovascular findings were in the abdomen, 30.3% (44/145) were in the chest, and 18.6% (27/145) were in the spine. A total of 19 significant non-cardiovascular findings were observed in 19 studies in individual patients (2.2% of total studies, 47% male, mean age 5.9 ± 6.7 years). Significant non-cardiovascular findings included hepatic adenoma, arterially enhancing focal liver lesions, asplenia, solitary kidney, pelvicaliectasis, renal cystic diseases, gastric distention, adrenal hemorrhage, lung hypoplasia, air space disease, bronchial narrowing, pneumomediastinum and retained surgical sponge. Non-cardiovascular findings were seen in 16.5% of cardiovascular MRI studies in children, of which 2.2% were clinically significant findings. Prevalence and nature of these non-cardiovascular findings are different from those reported in adults. Attention to these findings is important

Cardiovascular magnetic resonance physics for clinicians: part I.

Science.gov (United States)

Ridgway, John P

2010-11-30

There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject

Electron Acceleration in the Field-reversed Configuration (FRC) by Slowly Rotation Odd-parity Magnetic Fields (RMFo)

International Nuclear Information System (INIS)

Glasser, A.H.; Cohen, S.A.

2001-01-01

The trajectories of individual electrons are studied numerically in a 3D, prolate, FRC [field-reversed configuration] equilibrium magnetic geometry with added small-amplitude, slowly rotating, odd-parity magnetic fields (RMFos). RMFos cause electron heating by toroidal acceleration near the O-point line and by field-parallel acceleration away from it, both followed by scattering from magnetic-field inhomogeneities. Electrons accelerated along the O-point line move antiparallel to the FRC's current and attain average toroidal angular speeds near that of the RMFo, independent of the sense of RMFo rotation. A conserved transformed Hamiltonian, dependent on electron energy and RMFo sense, controls electron flux-surface coordinate

Cardiovascular magnetic resonance in hypertrophic cardiomyopathy

International Nuclear Information System (INIS)

Shiozaki, Afonso Akio; Parga, Jose Rodrigues; Arteaga, Edmundo; Rochitte, Carlos Eduardo; Tassi, Eduardo Marinho

2007-01-01

Hypertrophic cardiomyopathy (HCM) is the most frequent genetic cardiac disease that causes sudden death in young people, with an incidence of 1:500 adults. The routinely used criteria for worst prognosis have limited sensitivity and specificity. Thus, the estimated risk of evolving to dilated cardiomyopathy or sudden death is somewhat inaccurate, leading to management uncertainty of HCM patients. Therefore, an accurate noninvasive method for the diagnosis of HCM with prognostic value is of great importance. In the last years, Cardiovascular Magnetic Resonance (CMR) emerged not only as a diagnostic tool, but also as a study with prognostic values, by characterizing myocardial fibrosis with great accuracy in HCM patients. Additionally, CMR identifies the types of hypertrophy, analyses the ventricular function, estimates the intraventricular gradient and allows the determination of differential diagnosis. Moreover, CMR can uniquely access myocardial fibrosis in HCM. (author)

The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field

Energy Technology Data Exchange (ETDEWEB)

Giacalone, J. [Department of Planetary Sciences, University of Arizona, Tucson, AZ (United States)

2017-10-20

We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean and an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.

The role of magnetic loops in particle acceleration at nearly perpendicular shocks

Science.gov (United States)

Decker, R. B.

1993-01-01

The acceleration of superthermal ions is investigated when a planar shock that is on average nearly perpendicular propagates through a plasma in which the magnetic field is the superposition of a constant uniform component plus a random field of transverse hydromagnetic fluctuations. The importance of the broadband nature of the transverse magnetic fluctuations in mediating ion acceleration at nearly perpendicular shocks is pointed out. Specifically, the fluctuations are composed of short-wavelength components which scatter ions in pitch angle and long-wavelength components which are responsible for a spatial meandering of field lines about the mean field. At nearly perpendicular shocks the field line meandering produces a distribution of transient loops along the shock. As an application of this model, the acceleration of a superthermal monoenergetic population of seed protons at a perpendicular shock is investigated by integrating along the exact phase-space orbits.

Physics of the saturation of particle acceleration in relativistic magnetic reconnection

Science.gov (United States)

Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

2018-05-01

We investigate the saturation of particle acceleration in relativistic reconnection using two-dimensional particle-in-cell simulations at various magnetizations σ. We find that the particle energy spectrum produced in reconnection quickly saturates as a hard power law that cuts off at γ ≈ 4σ, confirming previous work. Using particle tracing, we find that particle acceleration by the reconnection electric field in X-points determines the shape of the particle energy spectrum. By analysing the current sheet structure, we show that physical cause of saturation is the spontaneous formation of secondary magnetic islands that can disrupt particle acceleration. By comparing the size of acceleration regions to the typical distance between disruptive islands, we show that the maximum Lorentz factor produced in reconnection is γ ≈ 5σ, which is very close to what we find in our particle energy spectra. We also show that the dynamic range in Lorentz factor of the power-law spectrum in reconnection is ≤40. The hardness of the power law combined with its narrow dynamic range implies that relativistic reconnection is capable of producing the hard narrow-band flares observed in the Crab nebula but has difficulty producing the softer broad-band prompt gamma-ray burst emission.

High field accelerator magnet R&D in Europe

CERN Document Server

Devred, Arnaud; Bottura, L; Chorowski, M; Fabbricatore, P; Leroy, D; den Ouden, A; Rifflet, J M; Rossi, L; Vincent-Viry, O; Volpini, G

2004-01-01

The LHC magnet R&D program has shown that the limit of NbTi technology at 1.9 K was in the 10-to-10.5-T range. Hence, to go beyond the 10-T threshold, it is necessary to change the superconducting material. Given the state of the art in HTS, the only serious candidate is Nb$_{3}$Sn. A series of dipole magnet models built at Twente University and LBNL as well as a vigorous program carried out at Fermilab have demonstrated the feasibility of Nb$_{3}$Sn magnet technology. The next step is to bring this technology to maturity, which require further conductor and conductor insulation development and a simplification of manufacturing processes. After a brief history, we review ongoing R&D programs in Europe and we present the Next European Dipole (NED) initiative promoted by the European Steering Group on Accelerator R&D (ESGARD).

Measurements of Pulmonary Artery Size for Assessment of Pulmonary Hypertension by Cardiovascular Magnetic Resonance and Clinical Application

Directory of Open Access Journals (Sweden)

Fan YANG

2017-02-01

Full Text Available Background and objective Pulmonary hypertension (PH often leads to dilatation of main pulmonary artery (MPA. MPA measurements can be used to predict PH. This aim of this study is to investigate power of MPA vessel indices, which are acquired from cardiovascular magnetic resonance, to evaluate PH. Methods Cardiovascular-magnetic-resonance-determined parameters of MPA were acquired and calculated in 83 PH patients, whose diagnosis were confirmed with right heart catheterization and 49 healthy volunteers; these parameters included MPA diameter (DPA, ratio of DPA and ascending aorta diameter (DPA/DAo, max mean diameter (MDmax, min mean diameter (MDmin, fraction transverse diameter (fTD, fraction longitudinal diameter (fLD, and distensibility. Results Compared with control group, DPA, DPA/DAo, MDmax, and MDmin were significantly higher in patients with PH (P28.4 mm, and MDmax>32.4 mm (area under the curve, AUC=0.979, 0.981 showed best performance in predicting PH, yielding highest specificity at 100%. Conclusion Noninvasive cardiovascular-magnetic-resonance-derived MPA measurements provide excellent and practical reference in clinical settings for detecting PH.

THE EFFECT OF LARGE-SCALE MAGNETIC TURBULENCE ON THE ACCELERATION OF ELECTRONS BY PERPENDICULAR COLLISIONLESS SHOCKS

International Nuclear Information System (INIS)

Guo Fan; Giacalone, Joe

2010-01-01

We study the physics of electron acceleration at collisionless shocks that move through a plasma containing large-scale magnetic fluctuations. We numerically integrate the trajectories of a large number of electrons, which are treated as test particles moving in the time-dependent electric and magnetic fields determined from two-dimensional hybrid simulations (kinetic ions and fluid electron). The large-scale magnetic fluctuations effect the electrons in a number of ways and lead to efficient and rapid energization at the shock front. Since the electrons mainly follow along magnetic lines of force, the large-scale braiding of field lines in space allows the fast-moving electrons to cross the shock front several times, leading to efficient acceleration. Ripples in the shock front occurring at various scales will also contribute to the acceleration by mirroring the electrons. Our calculation shows that this process favors electron acceleration at perpendicular shocks. The current study is also helpful in understanding the injection problem for electron acceleration by collisionless shocks. It is also shown that the spatial distribution of energetic electrons is similar to in situ observations. The process may be important to our understanding of energetic electrons in planetary bow shocks and interplanetary shocks, and explaining herringbone structures seen in some type II solar radio bursts.

Proton beam transport experiments with pulsed high-field magnets at the Dresden laser acceleration source Draco

Energy Technology Data Exchange (ETDEWEB)

Kroll, Florian; Schramm, Ulrich [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Universitaet Dresden, Dresden (Germany); Kraft, Stephan; Metzkes, Josefine; Schlenvoigt, Hans-Peter; Zeil, Karl [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)

2016-07-01

Compact laser-driven ion accelerators are a potential alternative to large and expensive conventional accelerators. High-power short-pulse lasers, impinging on e.g. thin metal foils, enable multi-MeV ion acceleration on μm length and fs to ps time scale. The generated ion bunches (typically protons) show unique beam properties, like ultra-high pulse dose. Nevertheless, laser accelerators still require substantial development in reliable beam generation and transport. Recently developed pulsed magnets meet the demands of laser acceleration and open up new research opportunities: We present a pulsed solenoid for effective collection and focusing of laser-accelerated protons that acts as link between fundamental research and application. The solenoid is powered by a capacitor-based pulse generator and can reach a maximum magnetic field of 20 T. It was installed in the target chamber of the Draco laser at HZDR. The transported beam was detected by means of radiochromic film, scintillator and Thomson parabola spectrometer. We present the characterization of the solenoid with regard to future application in radiobiological irradiation studies. Furthermore, a detailed comparison to previous experiments with a similar magnet at the PHELIX laser at GSI, Darmstadt is provided.

Electron acceleration by wave turbulence in a magnetized plasma

Science.gov (United States)

Rigby, A.; Cruz, F.; Albertazzi, B.; Bamford, R.; Bell, A. R.; Cross, J. E.; Fraschetti, F.; Graham, P.; Hara, Y.; Kozlowski, P. M.; Kuramitsu, Y.; Lamb, D. Q.; Lebedev, S.; Marques, J. R.; Miniati, F.; Morita, T.; Oliver, M.; Reville, B.; Sakawa, Y.; Sarkar, S.; Spindloe, C.; Trines, R.; Tzeferacos, P.; Silva, L. O.; Bingham, R.; Koenig, M.; Gregori, G.

2018-05-01

Astrophysical shocks are commonly revealed by the non-thermal emission of energetic electrons accelerated in situ1-3. Strong shocks are expected to accelerate particles to very high energies4-6; however, they require a source of particles with velocities fast enough to permit multiple shock crossings. While the resulting diffusive shock acceleration4 process can account for observations, the kinetic physics regulating the continuous injection of non-thermal particles is not well understood. Indeed, this injection problem is particularly acute for electrons, which rely on high-frequency plasma fluctuations to raise them above the thermal pool7,8. Here we show, using laboratory laser-produced shock experiments, that, in the presence of a strong magnetic field, significant electron pre-heating is achieved. We demonstrate that the key mechanism in producing these energetic electrons is through the generation of lower-hybrid turbulence via shock-reflected ions. Our experimental results are analogous to many astrophysical systems, including the interaction of a comet with the solar wind9, a setting where electron acceleration via lower-hybrid waves is possible.

Enhancement of electron energy during vacuum laser acceleration in an inhomogeneous magnetic field

Energy Technology Data Exchange (ETDEWEB)

Saberi, H.; Maraghechi, B., E-mail: behrouz@aut.ac.ir [Department of Physics, Amirkabir University of Technology, 15875-4413 Tehran (Iran, Islamic Republic of)

2015-03-15

In this paper, the effect of a stationary inhomogeneous magnetic field on the electron acceleration by a high intensity Gaussian laser pulse is investigated. A focused TEM (0,0) laser mode with linear polarization in the transverse x-direction that propagates along the z-axis is considered. The magnetic field is assumed to be stationary in time, but varies longitudinally in space. A linear spatial profile for the magnetic field is adopted. In other words, the axial magnetic field increases linearly in the z-direction up to an optimum point z{sub m} and then becomes constant with magnitude equal to that at z{sub m}. Three-dimensional single-particle simulations are performed to find the energy and trajectory of the electron. The electron rotates around and stays near the z-axis. It is shown that with a proper choice of the magnetic field parameters, the electron will be trapped at the focus of the laser pulse. Because of the cyclotron resonance, the electron receives enough energy from the laser fields to be accelerated to relativistic energies. Using numerical simulations, the criteria for optimum regime of the acceleration mechanism is found. With the optimized parameters, an electron initially at rest located at the origin achieves final energy of γ=802. The dynamics of a distribution of off-axis electrons are also investigated in which shows that high energy electrons with small energy and spatial spread can be obtained.

Superconducting accelerator magnet technology in the 21st century: A new paradigm on the horizon?

Science.gov (United States)

Gourlay, S. A.

2018-06-01

Superconducting magnets for accelerators were first suggested in the mid-60's and have since become one of the major components of modern particle colliders. Technological progress has been slow but steady for the last half-century, based primarily on Nb-Ti superconductor. That technology has reached its peak with the Large Hadron Collider (LHC). Despite the superior electromagnetic properties of Nb3Sn and adoption by early magnet pioneers, it is just now coming into use in accelerators though it has not yet reliably achieved fields close to the theoretical limit. The discovery of the High Temperature Superconductors (HTS) in the late '80's created tremendous excitement, but these materials, with tantalizing performance at high fields and temperatures, have not yet been successfully developed into accelerator magnet configurations. Thanks to relatively recent developments in both Bi-2212 and REBCO, and a more focused international effort on magnet development, the situation has changed dramatically. Early optimism has been replaced with a reality that could create a new paradigm in superconducting magnet technology. Using selected examples of magnet technology from the previous century to define the context, this paper will describe the possible innovations using HTS materials as the basis for a new paradigm.

R&D of Nb$_{3}$Sn accelerator magnets at Fermilab

CERN Document Server

Zlobin, A V; Andreev, N; Barzi, E; Bordini, B; Bossert, R; Carcagno, R; Chichili, D R; Di Marco, J; Elementi, L; Fehér, S; Kashikhin, V S; Kashikhin, V V; Kephart, R; Lamm, M J; Limon, P J; Novitski, I; Orris, D; Pischalnikov, Y; Schlabach, P; Stanek, R; Strait, J; Sylvester, C D; Tartaglia, M; Tompkins, J C; Turrioni, D; Velev, G; Yamada, R; Yarba, V A; 10.1109/TASC.2005.849507

2005-01-01

Fermilab is developing and investigating different high-field magnets (HFM) for present and future accelerators. The HFM R&D program focused on the 10-12 T magnets based on Nb/sub 3/Sn superconductor and explored both basic magnet technologies for brittle superconductors-wind-and-react and react-and-wind. Magnet design studies in support of LHC upgrades and VLHC were conducted. A series of 1-m long cos-theta dipole models based on the wind-and-react technique was fabricated and tested. Three 1-m long flat racetracks and the common coil dipole model, based on a single-layer coil and react-and-wind technique, were also fabricated and tested. Extensive theoretical and experimental studies of electro-magnetic instabilities in Nb/sub 3/Sn strands, cables and magnets were performed and led to a successful 10 T dipole model. This paper presents the details of Fermilab's HFM program, reports its status and major results, and formulates the next steps for the program.

A flexible and configurable system to test accelerator magnets

Energy Technology Data Exchange (ETDEWEB)

Jerzy M. Nogiec et al.

2001-07-20

Fermilab's accelerator magnet R and D programs, including production of superconducting high gradient quadrupoles for the LHC insertion regions, require rigorous yet flexible magnetic measurement systems. Measurement systems must be capable of handling various types of hardware and extensible to all measurement technologies and analysis algorithms. A tailorable software system that satisfies these requirements is discussed. This single system, capable of distributed parallel signal processing, is built on top of a flexible component-based framework that allows for easy reconfiguration and run-time modification. Both core and domain-specific components can be assembled into various magnet test or analysis systems. The system configured to comprise a rotating coil harmonics measurement is presented. Technologies as Java, OODB, XML, JavaBeans, software bus and component-based architectures are used.

Cardiovascular assessment of patients with Ullrich-Turner's Syndrome on Doppler echocardiography and magnetic resonance imaging

Directory of Open Access Journals (Sweden)

Castro Ana Valéria Barros de

2002-01-01

Full Text Available OBJECTIVE: To assess the cardiovascular features of Ullrich-Turner's syndrome using echocardiography and magnetic resonance imaging, and to correlate them with the phenotype and karyotype of the patients. The diagnostic concordance between the 2 methods was also assessed. METHODS: Fifteen patients with the syndrome were assessed by echocardiography and magnetic resonance imaging (cardiac chambers, valves, and aorta. Their ages ranged from 10 to 28 (mean of 16.7 years. The karyotype was analyzed in 11 or 25 metaphases of peripheral blood lymphocytes, or both. RESULTS: The most common phenotypic changes were short stature and spontaneous absence of puberal development (100%; 1 patient had a cardiac murmur. The karyotypes detected were as follows: 45,X (n=7, mosaics (n=5, and deletions (n=3. No echocardiographic changes were observed. In regard to magnetic resonance imaging, coarctation and dilation of the aorta were found in 1 patient, and isolated dilation of the aorta was found in 4 patients. CONCLUSION: The frequencies of coarctation and dilation of the aorta detected on magnetic resonance imaging were similar to those reported in the literature (5.5% to 20%, and 6.3% to 29%, respectively. This confirmed the adjuvant role of magnetic resonance imaging to Doppler echocardiography for diagnosing cardiovascular alterations in patients with Ullrich-Turner's syndrome.

Combining rotating-coil measurements of large-aperture accelerator magnets

CERN Document Server

AUTHOR|(CDS)2089510

2016-10-05

The rotating coil is a widely used tool to measure the magnetic field and the field errors in accelerator magnets. The coil has a length that exceeds the entire magnetic field along the longitudinal dimension of the magnet and gives therefore a two-dimensional representation of the integrated field. Having a very good precision, the rotating coil lacks in versatility. The fixed dimensions make it impractical and inapplicable in situations, when the radial coil dimension is much smaller than the aperture or when the aperture is only little covered by the coil. That being the case for rectangular apertures with large aspect ratio, where a basic measurement by the rotating coil describes the field only in a small area of the magnet. A combination of several measurements at different positions is the topic of this work. Very important for a combination is the error distribution on the measured field harmonics. To preserve the good precision of the higher-order harmonics, the combination must not rely on the main ...

Analysis and design of a slotless tubular permanent magnet actuator for high acceleration applications

NARCIS (Netherlands)

Meessen, K.J.; Paulides, J.J.H.; Lomonova, E.A.

2009-01-01

This paper presents the design of a linear actuator for high acceleration applications. In the analysis, a slotless tubular permanent magnet actuator is modeled by means of semianalytical field solutions. Several slotless topologies are modeled and compared to achieve the highest acceleration. A

Bulk ion acceleration and particle heating during magnetic reconnection in a laboratory plasma

Energy Technology Data Exchange (ETDEWEB)

Yoo, Jongsoo; Yamada, Masaaki; Ji, Hantao; Jara-Almonte, Jonathan; Myers, Clayton E. [Center for Magnetic Self-Organization, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2014-05-15

Bulk ion acceleration and particle heating during magnetic reconnection are studied in the collisionless plasma of the Magnetic Reconnection Experiment (MRX). The plasma is in the two-fluid regime, where the motion of the ions is decoupled from that of the electrons within the ion diffusion region. The reconnection process studied here is quasi-symmetric since plasma parameters such as the magnitude of the reconnecting magnetic field, the plasma density, and temperature are compatible on each side of the current sheet. Our experimental data show that the in-plane (Hall) electric field plays a key role in ion heating and acceleration. The electrostatic potential that produces the in-plane electric field is established by electrons that are accelerated near the electron diffusion region. The in-plane profile of this electrostatic potential shows a “well” structure along the direction normal to the reconnection current sheet. This well becomes deeper and wider downstream as its boundary expands along the separatrices where the in-plane electric field is strongest. Since the in-plane electric field is 3–4 times larger than the out-of-plane reconnection electric field, it is the primary source of energy for the unmagnetized ions. With regard to ion acceleration, the Hall electric field causes ions near separatrices to be ballistically accelerated toward the outflow direction. Ion heating occurs as the accelerated ions travel into the high pressure downstream region. This downstream ion heating cannot be explained by classical, unmagnetized transport theory; instead, we conclude that ions are heated by re-magnetization of ions in the reconnection exhaust and collisions. Two-dimensional (2-D) simulations with the global geometry similar to MRX demonstrate downstream ion thermalization by the above mechanisms. Electrons are also significantly heated during reconnection. The electron temperature sharply increases across the separatrices and peaks just outside of the

Mechanical engineering and design criteria for the Magnetically Insulated Transmission Experiment Accelerator

International Nuclear Information System (INIS)

Staller, G.E.; Hamilton, I.D.; Aker, M.F.; Fifer, H.G.

1978-02-01

A single-unit electron beam accelerator was designed, fabricated, and assembled in Sandia's Technical Area V to conduct magnetically insulated transmission experiments. Results of these experiments will be utilized in the future design of larger, more complex accelerators. This design makes optimum use of existing facilities and equipment. When designing new components, possible future applications were considered as well as compatibility with existing facilities and hardware

Value of Cardiovascular Magnetic Resonance Imaging in Noninvasive Risk Stratification in Tetralogy of Fallot

NARCIS (Netherlands)

Bokma, Jouke P.; de Wilde, Koen C.; Vliegen, Hubert W.; van Dijk, Arie P.; van Melle, Joost P.; Meijboom, Folkert J.; Zwinderman, Aeilko H.; Groenink, Maarten; Mulder, Barbara J. M.; Bouma, Berto J.

IMPORTANCE Adults late after total correction of tetralogy of Fallot (TOF) are at risk for majorcomplications. Cardiovascular magnetic resonance (CMR) imaging is recommended toquantify right ventricular (RV) and left ventricular (LV) function. However, a commonly usedrisk model by Khairy et al

In situ baking method for degassing of a kicker magnet in accelerator beam line

International Nuclear Information System (INIS)

Kamiya, Junichiro; Ogiwara, Norio; Yanagibashi, Toru; Kinsho, Michikazu; Yasuda, Yuichi

2016-01-01

In this study, the authors propose a new in situ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs toward the kicker magnet. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. A graphite heater was selected in this application to bake-out the kicker magnet in the beam line to ensure reliability and easy maintainability of the heater. The vacuum characteristics of graphite were suitable for heater operation in the beam line. A preliminary heat-up test conducted in the accelerator beam line also showed that each part of the kicker magnet was successfully heated and that thermal expansion of the chamber was negligibly small

In situ baking method for degassing of a kicker magnet in accelerator beam line

Energy Technology Data Exchange (ETDEWEB)

Kamiya, Junichiro, E-mail: kamiya.junichiro@jaea.go.jp; Ogiwara, Norio; Yanagibashi, Toru; Kinsho, Michikazu [Japan Atomic Energy Agency, J-PARC Center, Ooaza Shirakata 2-4, Tokai, Naka, Ibaraki 319-1195 (Japan); Yasuda, Yuichi [SAKAGUCHI E.H VOC CORP., Sakura Dai-san Kogyodanchi 1-8-6, Osaku, Sakura, Chiba 285-0802 (Japan)

2016-03-15

In this study, the authors propose a new in situ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs toward the kicker magnet. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. A graphite heater was selected in this application to bake-out the kicker magnet in the beam line to ensure reliability and easy maintainability of the heater. The vacuum characteristics of graphite were suitable for heater operation in the beam line. A preliminary heat-up test conducted in the accelerator beam line also showed that each part of the kicker magnet was successfully heated and that thermal expansion of the chamber was negligibly small.

The LACARA Vacuum Laser Accelerator Experiment: Beam Positioning and Alignment in a Strong Magnetic Field

International Nuclear Information System (INIS)

Shchelkunov, Sergey V.; Marshall, T. C.; Hirshfield, J. L.; Wang, Changbiao; LaPointe, M. A.

2006-01-01

LACARA (laser cyclotron auto-resonance accelerator) is a vacuum laser accelerator of electrons that is under construction at the Accelerator Test Facility (ATF), Brookhaven National Laboratory. It is expected that the experiment will be assembled by September 2006; this paper presents progress towards this goal. According to numerical studies, as an electron bunch moves along the LACARA solenoidal magnetic field (∼5.2 T, length ∼1 m), it will be accelerated from 50 to ∼75 MeV by interacting with a 0.8 TW Gaussian-mode circularly polarized optical pulse provided by the ATF CO2 10.6μm laser system. The LACARA laser transport optics must handle 10 J and be capable of forming a Gaussian beam inside the solenoid with a 1.4 mm waist and a Rayleigh range of 60 cm. The electron optics must transport a bunch having input emittance of 0.015 mm-mrad and 100 μm waist through the magnet. Precision alignment between the electron beam and the solenoid magnetic axis is required, and a method to achieve this is described in detail. Emittance- filtering may be necessary to yield an accelerated bunch having a narrow (∼1%) energy-spread

Magnetic field simulation of wiggler on LUCX accelerator facility using Radia

Science.gov (United States)

Sutygina, Y. N.; Harisova, A. E.; Shkitov, D. A.

2016-11-01

A flat wiggler consisting of NdFeB permanent magnets was installed on a compact linear electron accelerator LUCX (KEK) in Japan. After installing the wiggler on LUCX, the experiments on the generation of undulator radiation (UR) in the terahertz wavelength range is planned. To perform the detailed calculations and optimization of UR characteristics, it is necessary to know the parameters of the magnetic field generated in the wiggler. In this paper extended simulation results of wiggler magnetic field over the entire volume between the poles are presented. The obtained in the Radia simulation magnetic field is compared with the field calculated by another code, which is based on the finite element method.

Cardiovascular magnetic resonance in pulmonary hypertension

Science.gov (United States)

2012-01-01

Pulmonary hypertension represents a group of conditions characterized by higher than normal pulmonary artery pressures. Despite improved treatments, outcomes in many instances remain poor. In recent years, there has been growing interest in the use of Cardiovascular Magnetic Resonance (CMR) in patients with pulmonary hypertension. This technique offers certain advantages over other imaging modalities since it is well suited to the assessment of the right ventricle and the proximal pulmonary arteries. Reflecting the relatively sparse evidence supporting its use, CMR is not routinely recommended for patients with pulmonary hypertension. However, it is particularly useful in patient with pulmonary arterial hypertension associated with congenital heart disease. Furthermore, it has proven informative in a number of ways; illustrating how right ventricular remodeling is favorably reversed by drug therapies and providing explicit confirmation of the importance of the right ventricle to clinical outcome. This review will discuss these aspects and practical considerations before speculating on future applications. PMID:22257586

Injection septum magnets for the Loma Linda medical accelerator

International Nuclear Information System (INIS)

Satti, J.A.

1987-01-01

The injection beamline runs over the last magnet before a long straight section and is then displaced downward 55.88 cm to the accelerator beamline. The displacement is magnetic and the final deflection onto the synchrotron orbit is by an electric kicker. The first component, the reverse septum magnet, bends the injection beam 25/degree/ downward. This is followed by the injection septum (20/degree/ bend upward) and the final injection kicker (5/degree/ bend upward). The septum magnets produce a peak field of 3.4 K gauss at a current of 28,000 amperes within a 0.1 msec long pulse. The electric kicker produces a field of 7.3 KV/cm with a pulse length of 0.0011 msec. The septum magnets are similar to each other in construction with a bending radium of 72.7 cm. The curvature is required to increase the effective aperture. Each magnet has a single-turn copper coil bonded to a stainless steel plate for reinforcement. This eliminates insulating material, which could be subject to radiation damage, at the septum. The stainless steel plate is welded to the magnet laminations. The current is confined to the septum by the insulation between the laminations, which are a standard core material. The total septum thickness with shield is 1.227 cm. Pulsing the magnet eliminates the need for water cooling. 2 refs., 4 figs

Cardiovascular nuclear medicine and MRI

International Nuclear Information System (INIS)

Reiber, J.H.C.; Wall, E.E. van der

1992-01-01

This book is based on a meeting of the Working Group on Nuclear Cardiology, which held March 22-23,1991 under the auspices of the European Society of Cardiology and the Interuniversity Cardiology Institute of the Netherlands, and on the Second International Symposium on Computer Applications in Nuclear Medicine and Cardiac Magnetic Resonance Imaging, which was held March 20-22,1991 in Rotterdam, the Netherlands. It covers almost every aspect of quantitative cardio-vascular nuclear medicine and magnetic resonance imaging. The main topics are: single photon emission computed tomography (technical aspects); new development in cardiovascular nuclear medicine; advances in cardiovascular imaging; cardiovascular clinical applications; and cardiac magnetic resonance imaging. (A.S.). refs.; figs.; tabs

Electrostatic/magnetic ion acceleration through a slowly diverging magnetic nozzle between a ring anode and an on-axis hollow cathode

Directory of Open Access Journals (Sweden)

A. Sasoh

2017-06-01

Full Text Available Ion acceleration through a slowly diverging magnetic nozzle between a ring anode and a hollow cathode set on the axis of symmetry has been realized. Xenon was supplied as the propellant gas from an annular slit along the inner surface of the ring anode so that it was ionized near the anode, and the applied electric potential was efficiently transformed to an ion kinetic energy. As an electrostatic thruster, within the examined operation conditions, the thrust, F, almost scaled with the propellant mass flow rate; the discharge current, Jd, increased with the discharge voltage, Vd. An important characteristic was that the thrust also exhibited electromagnetic acceleration performance, i.e., the so-called “swirl acceleration,” in which F≅JdBRa ∕2, where B and Ra were a magnetic field and an anode inner radius, respectively. Such a unique thruster performance combining both electrostatic and electromagnetic accelerations is expected to be useful as another option for in-space electric propulsion in its broad functional diversity.

BOLD cardiovascular magnetic resonance at 3.0 tesla in myocardial ischemia.

OpenAIRE

Manka, R; Paetsch, I; Schnackenburg, B; Gebker, R; Fleck, E; Jahnke, C

2010-01-01

Abstract Background The purpose of this study was to determine the ability of Blood Oxygen Level Dependent (BOLD) cardiovascular magnetic resonance (CMR) to detect stress-inducible myocardial ischemic reactions in the presence of angiographically significant coronary artery disease (CAD). Methods Forty-six patients (34 men; age 65 ± 9 years,) with suspected or known coronary artery disease underwent CMR at 3Tesla prior to clinically indicated invasive coronary angiography. BOLD CMR was perfor...

Properties and parameters of the electron beam injected into the mirror magnetic trap of a plasma accelerator

Energy Technology Data Exchange (ETDEWEB)

Andreev, V. V., E-mail: temple18@mail.ru; Novitsky, A. A.; Vinnichenko, L. A.; Umnov, A. M.; Ndong, D. O. [Peoples’ Friendship University of Russia (Russian Federation)

2016-03-15

The parameters of the injector of an axial plasma beam injected into a plasma accelerator operating on the basis of gyroresonance acceleration of electrons in the reverse magnetic field are determined. The trapping of the beam electrons into the regime of gyroresonance acceleration is numerically simulated by the particle- in-cell method. The optimal time of axial injection of the beam into a magnetic mirror trap is determined. The beam parameters satisfying the condition of efficient particle trapping into the gyromagnetic autoresonance regime are found.

Experimental studies on the thermal properties of fast pulsed superconducting accelerator magnets

International Nuclear Information System (INIS)

Bleile, Alexander

2016-01-01

The new Facility for Antiproton and Ion Research FAIR is being constructed at the GSI research center in Darmstadt (Germany). This wordwide unique accelerator facility will provide beams of ions and antiprotons at high intensities and high energies for the fundamental research in nuclear, atomic and plasma physics as well as for applied science. The superconducting synchrotron SIS100 with a magnetic rigidity of 100 T/m, the core component of the FAIR facility will provide primary ion beams of all types from hydrogen up to uranium. One of the key technical systems of a new synchrotron are fast ramped electromagnets for the generation of fast ramped magnetic fields for deflecting and focusing of the ion beams. To reduce the energy consumption and to keep the operating costs of the synchrotron as low as possible superconducting magnet technology is applied in the SIS100. Superconducting magnets have been developed at GSI within the scope of the FAIR project. Although the superconducting magnet technology promises high cost saving, the power consumption of the fast ramped superconducting magnets can't be completely neglected. The pulsed operation generates dynamic losses in the iron yokes as well as in the superconducting coils of the magnets. A forced two-phase helium flow provides effective cooling for supercounducting magnets exposed to a continous relative high heat flow. The subject of this PhD thesis is experimental investigations and analysis of the dynamic power losses in fast ramped superconducting magnets and their dependencies on the operation cycles of the synchrotron. This research was conducted on the the first series SIS100 dipole magnet. Based on the experimentally defined dynamic heat loads and helium mass flow rates in the dipole magnet the heat loads and helium consumption for all other types of superconducting magnet modules of the SIS100 have been estimated. These results are essential for the development of the cooling system for the the

Laboratory studies of magnetized collisionless flows and shocks using accelerated plasmoids

Science.gov (United States)

Weber, T. E.; Smith, R. J.; Hsu, S. C.

2015-11-01

Magnetized collisionless shocks are thought to play a dominant role in the overall partition of energy throughout the universe, but have historically proven difficult to create in the laboratory. The Magnetized Shock Experiment (MSX) at LANL creates conditions similar to those found in both space and astrophysical shocks by accelerating hot (100s of eV during translation) dense (1022 - 1023 m-3) Field Reversed Configuration (FRC) plasmoids to high velocities (100s of km/s); resulting in β ~ 1, collisionless plasma flows with sonic and Alfvén Mach numbers of ~10. The FRC subsequently impacts a static target such as a strong parallel or anti-parallel (reconnection-wise) magnetic mirror, a solid obstacle, or neutral gas cloud to create shocks with characteristic length and time scales that are both large enough to observe yet small enough to fit within the experiment. This enables study of the complex interplay of kinetic and fluid processes that mediate cosmic shocks and can generate non-thermal distributions, produce density and magnetic field enhancements much greater than predicted by fluid theory, and accelerate particles. An overview of the experimental capabilities of MSX will be presented, including diagnostics, selected recent results, and future directions. Supported by the DOE Office of Fusion Energy Sciences under contract DE-AC52-06NA25369.

Uncomplicated obesity is associated with abnormal aortic function assessed by cardiovascular magnetic resonance

Directory of Open Access Journals (Sweden)

Channon Keith M

2008-02-01

Full Text Available Abstract Aims Obese subjects with insulin resistance and hypertension have abnormal aortic elastic function, which may predispose them to the development of left ventricular dysfunction. We hypothesised that obesity, uncomplicated by other cardiovascular risk factors, is independently associated with aortic function. Methods and results We used magnetic resonance imaging to measure aortic compliance, distensibility and stiffness index in 27 obese subjects (BMI 33 kg/m2 without insulin resistance and with normal cholesterol and blood pressure, and 12 controls (BMI 23 kg/m2. Obesity was associated with reduced aortic compliance (0.9 ± 0.1 vs. 1.5 ± 0.2 mm2/mmHg in controls, p -1 × 10-3, p Conclusion Aortic elastic function is abnormal in obese subjects without other cardiovascular risk factors. These findings highlight the independent importance of obesity in the development of cardiovascular disease.

Concepts for the magnetic design of the MITICA neutral beam test facility ion accelerator.

Science.gov (United States)

Chitarin, G; Agostinetti, P; Marconato, N; Marcuzzi, D; Sartori, E; Serianni, G; Sonato, P

2012-02-01

The megavolt ITER injector concept advancement neutral injector test facility will be constituted by a RF-driven negative ion source and by an electrostatic Accelerator, designed to produce a negative Ion with a specific energy up to 1 MeV. The beam is then neutralized in order to obtain a focused 17 MW neutral beam. The magnetic configuration inside the accelerator is of crucial importance for the achievement of a good beam efficiency, with the early deflection of the co-extracted and stripped electrons, and also of the required beam optic quality, with the correction of undesired ion beamlet deflections. Several alternative magnetic design concepts have been considered, comparing in detail the magnetic and beam optics simulation results, evidencing the advantages and drawbacks of each solution both from the physics and engineering point of view.

Experimental study of ion heating and acceleration during magnetic reconnection

Energy Technology Data Exchange (ETDEWEB)

Hsu, S.C.

2000-01-28

This dissertation reports an experimental study of ion heating and acceleration during magnetic reconnection, which is the annihilation and topological rearrangement of magnetic flux in a conductive plasma. Reconnection is invoked often to explain particle heating and acceleration in both laboratory and naturally occurring plasmas. However, a simultaneous account of reconnection and its associated energy conversion has been elusive due to the extreme inaccessibility of reconnection events, e.g. in the solar corona, the Earth's magnetosphere, or in fusion research plasmas. Experiments for this work were conducted on MRX (Magnetic Reconnection Experiment), which creates a plasma environment allowing the reconnection process to be isolated, reproduced, and diagnosed in detail. Key findings of this work are the identification of local ion heating during magnetic reconnection and the determination that non-classical effects must provide the heating mechanism. Measured ion flows are sub-Alfvenic and can provide only slight viscous heating, and classical ion-electron interactions can be neglected due to the very long energy equipartition time. The plasma resistivity in the reconnection layer is seen to be enhanced over the classical value, and the ion heating is observed to scale with the enhancement factor, suggesting a relationship between the magnetic energy dissipation mechanism and the ion heating mechanism. The observation of non-classical ion heating during reconnection has significant implications for understanding the role played by non-classical dissipation mechanisms in generating fast reconnection. The findings are relevant for many areas of space and laboratory plasma research, a prime example being the currently unsolved problem of solar coronal heating. In the process of performing this work, local measurements of ion temperature and flows in a well-characterized reconnection layer were obtained for the first time in either laboratory or observational

Experimental study of ion heating and acceleration during magnetic reconnection

International Nuclear Information System (INIS)

Hsu, S.C.

2000-01-01

This dissertation reports an experimental study of ion heating and acceleration during magnetic reconnection, which is the annihilation and topological rearrangement of magnetic flux in a conductive plasma. Reconnection is invoked often to explain particle heating and acceleration in both laboratory and naturally occurring plasmas. However, a simultaneous account of reconnection and its associated energy conversion has been elusive due to the extreme inaccessibility of reconnection events, e.g. in the solar corona, the Earth's magnetosphere, or in fusion research plasmas. Experiments for this work were conducted on MRX (Magnetic Reconnection Experiment), which creates a plasma environment allowing the reconnection process to be isolated, reproduced, and diagnosed in detail. Key findings of this work are the identification of local ion heating during magnetic reconnection and the determination that non-classical effects must provide the heating mechanism. Measured ion flows are sub-Alfvenic and can provide only slight viscous heating, and classical ion-electron interactions can be neglected due to the very long energy equipartition time. The plasma resistivity in the reconnection layer is seen to be enhanced over the classical value, and the ion heating is observed to scale with the enhancement factor, suggesting a relationship between the magnetic energy dissipation mechanism and the ion heating mechanism. The observation of non-classical ion heating during reconnection has significant implications for understanding the role played by non-classical dissipation mechanisms in generating fast reconnection. The findings are relevant for many areas of space and laboratory plasma research, a prime example being the currently unsolved problem of solar coronal heating. In the process of performing this work, local measurements of ion temperature and flows in a well-characterized reconnection layer were obtained for the first time in either laboratory or observational

CAS CERN Accelerator School superconductivity in particle accelerators

International Nuclear Information System (INIS)

Turner, S.

1989-01-01

One of the objectives of the CERN Accelerator School is to run courses on specialised topics in the particle accelerator field. The present volume contains the proceedings of one such course, this time organized in conjunction with the Deutsches Elektronen Synchrotron (DESY) on the subject of superconductivity in particle accelerators. This course reflects the very considerable progress made over the last few years in the use of the technology for the magnet and radio-frequency systems of many large and small accelerators already in use or nearing completion, while also taking account of the development work now going on for future machines. The lectures cover the theory of superconductivity, cryogenics and accelerator magnets and cavities, while the seminars include superfluidity, superconductors, special magnets and the prospects for high-temperature superconductors. (orig.)

Cardiovascular mortality and exposure to extremely low frequency magnetic fields: a cohort study of Swiss railway workers

Directory of Open Access Journals (Sweden)

Pfluger Dominik

2008-07-01

Full Text Available Abstract Background Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields. Methods We studied a cohort of 20,141 Swiss railway employees between 1972 and 2002, including highly exposed train drivers (median lifetime exposure 120.5 μT-years, and less or little exposed shunting yard engineers (42.1 μT-years, train attendants (13.3 μT-years and station masters (5.7 μT-years. During 464,129 person-years of follow up, 5,413 deaths were recorded and 3,594 deaths were attributed to cardio-vascular diseases. We analyzed data using Cox proportional hazards models. Results For all cardiovascular mortality the hazard ratio compared to station masters was 0.99 (95%CI: 0.91, 1.08 in train drivers, 1.13 (95%CI: 0.98, 1.30 in shunting yard engineers, and 1.09 (95%CI: 1.00, 1.19 in train attendants.Corresponding hazard ratios for arrhythmia related deaths were 1.04 (95%CI: 0.68, 1.59, 0.58 (95%CI: 0.24, 1.37 and 1.30 (95%CI: 0.87, 1.93 and for acute myocardial infarction 1.00 (95%CI: 0.73, 1.36, 1.56 (95%CI: 1.04, 2.32, and 1.14 (95%CI: 0.85, 1.53. The hazard ratio for arrhythmia related deaths per 100 μT-years of cumulative exposure was 0.94 (95%CI: 0.71, 1.24 and 0.91 (95%CI: 0.75, 1.11 for acute myocardial infarction. Conclusion This study provides evidence against an association between long-term occupational exposure to intermittent 16.7 Hz magnetic fields and cardiovascular mortality.

Effects of Turbulent Magnetic Fields on the Transport and Acceleration of Energetic Charged Particles: Numerical Simulations with Application to Heliospheric Physics

Science.gov (United States)

Guo, Fan

2012-11-01

Turbulent magnetic fields are ubiquitous in space physics and astrophysics. The influence of magnetic turbulence on the motions of charged particles contains the essential physics of the transport and acceleration of energetic charged particles in the heliosphere, which is to be explored in this thesis. After a brief introduction on the energetic charged particles and magnetic fields in the heliosphere, the rest of this dissertation focuses on three specific topics: 1. the transport of energetic charged particles in the inner heliosphere, 2. the acceleration of ions at collisionless shocks, and 3. the acceleration of electrons at collisionless shocks. We utilize various numerical techniques to study these topics. In Chapter 2 we study the propagation of charged particles in turbulent magnetic fields similar to the propagation of solar energetic particles in the inner heliosphere. The trajectories of energetic charged particles in the turbulent magnetic field are numerically integrated. The turbulence model includes a Kolmogorov-like magnetic field power spectrum containing a broad range of scales from those that lead to large-scale field-line random walk to small scales leading to resonant pitch-angle scattering of energetic particles. We show that small-scale variations in particle intensities (the so-called "dropouts") and velocity dispersions observed by spacecraft can be reproduced using this method. Our study gives a new constraint on the error of "onset analysis", which is a technique commonly used to infer information about the initial release of energetic particles. We also find that the dropouts are rarely produced in the simulations using the so-called "two-component" magnetic turbulence model (Matthaeus et al., 1990). The result questions the validity of this model in studying particle transport. In the first part of Chapter 3 we study the acceleration of ions in the existence of turbulent magnetic fields. We use 3-D self-consistent hybrid simulations

Dilation of the ascending aorta in Turner syndrome - a prospective cardiovascular magnetic resonance study

Directory of Open Access Journals (Sweden)

Pedersen Erik M

2011-04-01

Full Text Available Abstract Background The risk of aortic dissection is 100-fold increased in Turner syndrome (TS. Unfortunately, risk stratification is inadequate due to a lack of insight into the natural course of the syndrome-associated aortopathy. Therefore, this study aimed to prospectively assess aortic dimensions in TS. Methods Eighty adult TS patients were examined twice with a mean follow-up of 2.4 ± 0.4 years, and 67 healthy age and gender-matched controls were examined once. Aortic dimensions were measured at nine predefined positions using 3D, non-contrast and free-breathing cardiovascular magnetic resonance. Transthoracic echocardiography and 24-hour ambulatory blood pressure were also performed. Results At baseline, aortic diameters (body surface area indexed were larger at all positions in TS. Aortic dilation was more prevalent at all positions excluding the distal transverse aortic arch. Aortic diameter increased in the aortic sinus, at the sinotubular junction and in the mid-ascending aorta with growth rates of 0.1 - 0.4 mm/year. Aortic diameters at all other positions were unchanged. The bicuspid aortic valve conferred higher aortic sinus growth rates (p Conclusion A general aortopathy is present in TS with enlargement of the ascending aorta, which is accelerated in the presence of a bicuspid aortic valve.

Nonlinear Monte Carlo model of superdiffusive shock acceleration with magnetic field amplification

Science.gov (United States)

Bykov, Andrei M.; Ellison, Donald C.; Osipov, Sergei M.

2017-03-01

Fast collisionless shocks in cosmic plasmas convert their kinetic energy flow into the hot downstream thermal plasma with a substantial fraction of energy going into a broad spectrum of superthermal charged particles and magnetic fluctuations. The superthermal particles can penetrate into the shock upstream region producing an extended shock precursor. The cold upstream plasma flow is decelerated by the force provided by the superthermal particle pressure gradient. In high Mach number collisionless shocks, efficient particle acceleration is likely coupled with turbulent magnetic field amplification (MFA) generated by the anisotropic distribution of accelerated particles. This anisotropy is determined by fast particle transport, making the problem strongly nonlinear and multiscale. Here, we present a nonlinear Monte Carlo model of collisionless shock structure with superdiffusive propagation of high-energy Fermi accelerated particles coupled to particle acceleration and MFA, which affords a consistent description of strong shocks. A distinctive feature of the Monte Carlo technique is that it includes the full angular anisotropy of the particle distribution at all precursor positions. The model reveals that the superdiffusive transport of energetic particles (i.e., Lévy-walk propagation) generates a strong quadruple anisotropy in the precursor particle distribution. The resultant pressure anisotropy of the high-energy particles produces a nonresonant mirror-type instability that amplifies compressible wave modes with wavelengths longer than the gyroradii of the highest-energy protons produced by the shock.

Cardiovascular magnetic resonance in pericardial diseases

Directory of Open Access Journals (Sweden)

Francone Marco

2009-05-01

Full Text Available Abstract The pericardium and pericardial diseases in particular have received, in contrast to other topics in the field of cardiology, relatively limited interest. Today, despite improved knowledge of pathophysiology of pericardial diseases and the availability of a wide spectrum of diagnostic tools, the diagnostic challenge remains. Not only the clinical presentation may be atypical, mimicking other cardiac, pulmonary or pleural diseases; in developed countries a shift for instance in the epidemiology of constrictive pericarditis has been noted. Accurate decision making is crucial taking into account the significant morbidity and mortality caused by complicated pericardial diseases, and the potential benefit of therapeutic interventions. Imaging herein has an important role, and cardiovascular magnetic resonance (CMR is definitely one of the most versatile modalities to study the pericardium. It fuses excellent anatomic detail and tissue characterization with accurate evaluation of cardiac function and assessment of the haemodynamic consequences of pericardial constraint on cardiac filling. This review focuses on the current state of knowledge how CMR can be used to study the most common pericardial diseases.

An FPGA-based quench detection and protection system for superconducting accelerator magnets

International Nuclear Information System (INIS)

Carcagno, R.H.; Feher, S.; Lamm, M.; Makulski, A.; Nehring, R.; Orris, D.F.; Pischalnikov, Y.; Tartaglia, M.; Fermilab

2005-01-01

A new quench detection and protection system for superconducting accelerator magnets was developed for the Fermilab's Magnet Test Facility (MTF). This system is based on a Field-Programmable Gate Array (FPGA) module, and it is made of mostly commercially available, integrated hardware and software components. It provides all the functions of our existing VME-based quench detection and protection system, but in addition the new system is easily scalable to protect multiple magnets powered independently and a more powerful user interface and analysis tools. The new system has been used successfully for testing LHC Interaction Region Quadrupoles correctors and High Field Magnet HFDM04. In this paper we describe the system and present results

An FPGA-based quench detection and protection system for superconducting accelerator magnets

Energy Technology Data Exchange (ETDEWEB)

Carcagno, R.H.; Feher, S.; Lamm, M.; Makulski, A.; Nehring, R.; Orris, D.F.; Pischalnikov, Y.; Tartaglia, M.; /Fermilab

2005-05-01

A new quench detection and protection system for superconducting accelerator magnets was developed for the Fermilab's Magnet Test Facility (MTF). This system is based on a Field-Programmable Gate Array (FPGA) module, and it is made of mostly commercially available, integrated hardware and software components. It provides all the functions of our existing VME-based quench detection and protection system, but in addition the new system is easily scalable to protect multiple magnets powered independently and a more powerful user interface and analysis tools. The new system has been used successfully for testing LHC Interaction Region Quadrupoles correctors and High Field Magnet HFDM04. In this paper we describe the system and present results.

Time variations of fields in superconducting magnets and their effects on accelerators

Energy Technology Data Exchange (ETDEWEB)

Herrup, D.A.; Syphers, M.J.; Johnson, D.E.; Johnson, R.P.; Tollestrup, A.V.; Hanft, R.W.; Brown, B.C.; Lamm, M.J.; Kuchnir, M.; McInturff, A.D.

1988-08-22

A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs.

Time variations of fields in superconducting magnets and their effects on accelerators

International Nuclear Information System (INIS)

Herrup, D.A.; Syphers, M.J.; Johnson, D.E.

1988-01-01

A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs

Effects of laser-polarization and wiggler magnetic fields on electron acceleration in laser-cluster interaction

Science.gov (United States)

Singh Ghotra, Harjit; Kant, Niti

2018-06-01

We examine the electron dynamics during laser-cluster interaction. In addition to the electrostatic field of an individual cluster and laser field, we consider an external transverse wiggler magnetic field, which plays a pivotal role in enhancing the electron acceleration. Single-particle simulation has been presented with a short pulse linearly polarized as well as circularly polarized laser pulses for electron acceleration in a cluster. The persisting Coulomb field allows the electron to absorb energy from the laser field. The stochastically heated electron finds a weak electric field at the edge of the cluster from where it is ejected. The wiggler magnetic field connects the regions of the stochastically heated, ejected electron from the cluster and high energy gain by the electron from the laser field outside the cluster. This increases the field strength and hence supports the electron to meet the phase of the laser field for enhanced acceleration. A long duration resonance appears with an optimized magnetic wiggler field of about 3.4 kG. Hence, the relativistic energy gain by the electron is enhanced up to a few 100 MeV with an intense short pulse laser with an intensity of about 1019 W cm‑2 in the presence of a wiggler magnetic field.

Collective acceleration of laser plasma in a nonstationary and nonuniform magnetic field

Science.gov (United States)

Isaev, A.; Kozlovskiy, K.; Shikanov, A.; Vovchenko, E.

2017-12-01

This paper presents the new experimental results concerning acceleration of deuterium ions extracted from laser plasma in the rapid-growing nonuniform magnetic field in order to initiate the nuclear reactions D(d, n)3He and T(d, n)4He. For obtaining of laser plasma a Nd: YAG laser (λ = 1,06 μm) that generates in Q-switched mode the radiation pulses with the energy W ≤ 0,85 J and duration of τ ≈ 10 ns was used. Rapid-growing magnetic field was created with the discharge of Arkadyev-Marx pulsed-voltage generator to conical coil with the inductance of 0,65 μΗ. At characteristic discharge time of 30 ns, the rate of magnetic field growth achieved 2·107 T/s. Ion velocity was determined with the time-of-flight technique. During the experiment on deuterium plasma an ion flux velocity of ∼3 · 108 cm/s was obtained, which corresponds to the deuteron energy of ∼100 keV. Herewith, for target power density of ∼5·1011 W/cm2 obtaining of up to 1015 of accelerated deuterons and up to 108 of neutrons per a pulse is expected.

The role of cardiovascular magnetic resonance in assessment of patients after radical surgical correction of tetralogy of Fallot

International Nuclear Information System (INIS)

Genova, K.; Dasheva, A.

2014-01-01

Surgical management of tetralogy of Fallot (TOF) results in residual anatomic and functional abnormalities in majority of patients. Primarily considered as a benign pulmonary regurgitation with the time results in right ventricular overload, loses the compensatory mechanisms and irreversible right ventricular dilatation and dysfunction. Cardiovascular magnetic resonance (CMR) has evolved during the last two decades as the reference standard imaging modality to assess the anatomic and functional changes in patients with repaired TOF. This article reviews the role of CMR to assess the right ventricular function and to evaluate the degree of pulmonary regurgitation and comments some technical aspects, based to our experience. Key words: Tetralogy of Fallot. Cardiovascular Magnetic Resonance. Pulmonary regurgitation. Right ventricular assessment

A fiber optic strain measurement and quench localization for use in superconducting accelerator dipole magnets

International Nuclear Information System (INIS)

van Oort, J.M.; Scanlan, R.M.; ten Kate, H.H.J.

1994-01-01

A novel fiber-optic measurement system for superconducting accelerator magnets is described. The principal component is an extrinsic Fabry-Perot Interferometer to determine localized strain and stress in coil windings. The system can be used either as a sensitive relative strain measurement system or as an absolute strain detector. Combined, one can monitor the mechanical behaviour of the magnet system over time during construction, long time storage and operation. The sensing mechanism is described, together with various tests in laboratory environments. The test results of a multichannel test matrix to be incorporated first in the dummy coils and then in the final version of a 13T Nb 3 Sn accelerator dipole magnet are presented. Finally, the possible use of this system as a quench localization system is proposed

Acceleration of magnetized plasma rings

International Nuclear Information System (INIS)

Hartman, D.; Eddleman, J.; Hammer, J.H.

1982-01-01

One scheme is considered, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focussing) during acceleration. Because the allowable acceleration force F/sub a/ = kappa U/sub m//R (kappa - 2 , the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency

Superconducting accelerator technology

International Nuclear Information System (INIS)

Grunder, H.A.; Hartline, B.K.

1986-01-01

Modern and future accelerators for high energy and nuclear physics rely increasingly on superconducting components to achieve the required magnetic fields and accelerating fields. This paper presents a practical overview of the phenomenon of superconductivity, and describes the design issues and solutions associated with superconducting magnets and superconducting rf acceleration structures. Further development and application of superconducting components promises increased accelerator performance at reduced electric power cost

Flow imaging of the cardiovascular system using magnetic resonance imaging

International Nuclear Information System (INIS)

Imai, Hitoshi; Sakakibara, Makoto; Sunami, Yuko

1988-01-01

Blood flow images by magnetic resonance imaging (MRI) using a 0.25 T unit were evaluated for nine normal volunteers and 108 subjects with a variety of cardiovascular abnormalities. Using the non-gated short-spin echo (SE) technique, blood flow in the cardiovascular systems was not imaged in the normal volunteers. Using end-systolic and end-diastolic SE techniques for the normal subjects, blood flow in the cardiac chambers was not clearly imaged. Blood flow in the ascending aorta and aortic arch often did not appear in the gated SE images of the normal subjects. However, blood flow in the descending aorta was often observed in the gated SE images. Blood flow imaging was demonstrated by both non-gated and gated SE techniques in regions where blood flow was relatively slow; for example, in the left atrium of mitral stenosis, in an aortic aneurysm, in a false lumen of an aortic dissection, and in the left ventricle having old myocardial infarction. Using the non-gated inversion recovery (IR) technique, no blood flow was imaged in the cardiovascular system except in the left atrium of one case with mitral stenosis. Using the non-gated short SE technique, there was good correlation between the thrombus formation and the presence of blood flow images in the left atria of 17 patients with mitral stenosis, and in the aneurysmal portions of the aorta or in the false lumens of aortic dissection of 18 patients. It was suggested that mural thrombi in such diseases were related to the relatively slow blood flow. Blood flow imaging easily distinguished stagnant blood flow from mural thrombi using non-gated short SE, end-systolic SE, and IR techniques. Thus, blood flow imaging using MRI should become an important means of evaluating the cardiovascular system. (author)

Magnet R and D for the US LHC Accelerator Research Program (LARP)

International Nuclear Information System (INIS)

Gourlay, S.A.; Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S.; Dietderich, D.R.; Ferracin, P.; Gupta, R.; Ghosh, A.; Hafalia, A.R.; Hannaford, C.R.; Harrison, M.; Kashikhin, V.S.; Kashikhin, V.V.; Lietzke, A.F.; Mattafirri, S.; McInturff, A.D.; Nobrega, F.; Novitsky, I.; Sabbi, G.L.; Schmazle, J.; Stanek, R.; Turrioni, D.; Wanderer, P.; Yamada, R.; Zlobin, A.V.

2006-01-01

In 2004, the US DOE established the LHC Accelerator Research Program (LARP) with the goal of developing a technology base for future upgrades of the LHC. The focus of the magnet program, which is a collaboration of three US laboratories, BNL, FNAL and LBNL, is on development of high gradient quadrupoles using Nb 3 Sn superconductor. Other program components address issues regarding magnet design, radiation-hard materials, long magnet scale-up, quench protection, fabrication techniques and conductor and cable R and D. This paper presents an overall view of the program with emphasis on the current quadrupole project and outlines the long-term goals of the program

Repeated superovulation increases the risk of osteoporosis and cardiovascular diseases by accelerating ovarian aging in mice.

Science.gov (United States)

Zhang, Jinjin; Lai, Zhiwen; Shi, Liangyan; Tian, Yong; Luo, Aiyue; Xu, Zheyuan; Ma, Xiangyi; Wang, Shixuan

2018-05-22

Superovulation procedures and assisted reproductive technologies have been widely used to treat couples who have infertility problems. Although generally safe, the superovulation procedures are associated with a series of complications, such as ovarian hyper-stimulation syndrome, thromboembolism, and adnexal torsion. The role of long-term repeated superovulation in ovarian aging and especially in associated disorders such as osteoporosis and cardiovascular diseases is still unclear. In this study, we sought to determine if repeated superovulation by ten cycles of treatment with pregnant mare serum gonadotropin/human chorionic gonadotropin could affect ovarian reserve, ovarian function, bone density and heart function. Ovarian reserve and function were reflected by the size of the primordial follicle pool, anti-Mullerian hormone expressions, hormone levels and fertility status. Furthermore, we examined bone density and heart function by microCT and cardiovascular ultrasonography, respectively. After repeated superovulation, the size of the primordial follicle pool and the expression of anti-mullerian hormone decreased, along with the concentrations of estrogen and progesterone. Mice exposed to repeated superovulation showed an obvious decrease in fertility and fecundity. Furthermore, both bone density and heart ejection fraction significantly decreased. These results suggest that repeated superovulation may increase the risk of osteoporosis and cardiovascular diseases by accelerating ovarian aging.

Ponderomotive ion acceleration in dense magnetized laser-irradiated thick target plasmas

Science.gov (United States)

Sinha, Ujjwal; Kaw, Predhiman

2012-03-01

When a circularly polarized laser pulse falls on an overdense plasma, it displaces the electrons via ponderomotive force creating a double layer. The double layer constitutes of an ion and electron sheath with in which the electrostatic field present is responsible for ion acceleration. In this paper, we have analyzed the effect a static longitudinal magnetic field has over the ion acceleration mechanism. The longitudinal magnetic field changes the plasma dielectric constant due to cyclotron effects which in turn enhances or reduces the ponderomotive force exerted by the laser depending on whether the laser is left or right circularly polarized. Also, the analysis of the ion space charge region present behind the ion sheath of the laser piston that undergoes coulomb explosion has been explored for the first time. We have studied the interaction of an incoming ion beam with the laser piston and the ion space charge. It has been found that the exploding ion space charge has the ability to act as an energy amplifier for incoming ion beams.

Comparison of mechanical concepts for $Nb_3Sn$ high field accelerator magnets

CERN Document Server

AUTHOR|(CDS)2084469; Peter, Schmolz

Several magnets using Nb$_{3}$Sn as conductor are currently developed at CERN; these magnets are either slated for future updates of the LHC or for research purposes relating to future accelerators. The mechanical structure is one of the challenging aspects of superconducting high-field magnets. The main purpose of the mechanical structure is to keep the coils in compression till the emergence of the highest electromagnetic forces that are developed in the ultimate field of the magnet. Any loss of pre-compression during the magnet’s excitation would cause too large deformation of the coil and possibly a quench in the conductor owing to relative movements of strands in contact associated with excessive local heat release. However, too high pre-compression would overstrain the conductor and thereby limit the performance of the magnet. This thesis focuses on the mechanical behaviour of three of these magnets. All of them are based on different mechanical designs, “bladder and key” and “collar-based”, ...

KEK digital accelerator

Directory of Open Access Journals (Sweden)

T. Iwashita

2011-07-01

Full Text Available The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.

Low-noise pulse-mode current power supply for magnetic field measurements of magnets for accelerators

International Nuclear Information System (INIS)

Omel'yanenko, M.M.; Borisov, V.V.; Donyagin, A.M.; Kostromin, S.A.; Makarov, A.A.; Khodzhibagiyan, G.G.; Shemchuk, A.V.

2017-01-01

The described pulse-mode current power supply has been designed and fabricated for the magnetic field measurement system of superconducting magnets for accelerators. The power supply is based on a current regulator with pass transistor bank in linear mode. The output current pulses (0-100 A) are produced by using the energy of preliminary charged capacitor bank (5-40 V), which is charged additionally after each pulse. There is no AC-line frequency and harmonics ripple in the output current, the relative noise level is less than -100 dB (or 10 -5 ) of RMS value (it is defined as the ratio of output RMS noise current to the maximal output current 100 A within the operating bandwidth, expressed in dB).

TU-H-BRA-02: The Physics of Magnetic Field Isolation in a Novel Compact Linear Accelerator Based MRI-Guided Radiation Therapy System

Energy Technology Data Exchange (ETDEWEB)

Low, D [UCLA, Los Angeles, CA (United States); Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Shvartsman, S; Chmielewski, T; Fought, G; Sharma, A; Dempsey, J [ViewRay, Inc., Oakwood Village, OH (United States)

2016-06-15

Purpose: To develop a method for isolating the MRI magnetic field from field-sensitive linear accelerator components at distances close to isocenter. Methods: A MRI-guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. In order to accomplish this, the magnetron, port circulator, radiofrequency waveguide, gun driver, and linear accelerator needed to be placed in locations with low magnetic fields. The system was also required to be compact, so moving these components far from the main magnetic field and isocenter was not an option. The magnetic field sensitive components (exclusive of the waveguide) were placed in coaxial steel sleeves that were electrically and mechanically isolated and whose thickness and placement were optimized using E&M modeling software. Six sets of sleeves were placed 60° apart, 85 cm from isocenter. The Faraday effect occurs when the direction of propagation is parallel to the magnetic RF field component, rotating the RF polarization, subsequently diminishing RF power. The Faraday effect was avoided by orienting the waveguides such that the magnetic field RF component was parallel to the magnetic field. Results: The magnetic field within the shields was measured to be less than 40 Gauss, significantly below the amount needed for the magnetron and port circulator. Additional mu-metal was employed to reduce the magnetic field at the linear accelerator to less than 1 Gauss. The orientation of the RF waveguides allowed the RT transport with minimal loss and reflection. Conclusion: One of the major challenges in designing a compact linear accelerator based MRI-guided radiation therapy system, that of creating low magnetic field environments for the magnetic-field sensitive components, has been solved. The measured magnetic fields are sufficiently small to enable system integration. This work supported by ViewRay, Inc.

TU-H-BRA-02: The Physics of Magnetic Field Isolation in a Novel Compact Linear Accelerator Based MRI-Guided Radiation Therapy System

International Nuclear Information System (INIS)

Low, D; Mutic, S; Shvartsman, S; Chmielewski, T; Fought, G; Sharma, A; Dempsey, J

2016-01-01

Purpose: To develop a method for isolating the MRI magnetic field from field-sensitive linear accelerator components at distances close to isocenter. Methods: A MRI-guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. In order to accomplish this, the magnetron, port circulator, radiofrequency waveguide, gun driver, and linear accelerator needed to be placed in locations with low magnetic fields. The system was also required to be compact, so moving these components far from the main magnetic field and isocenter was not an option. The magnetic field sensitive components (exclusive of the waveguide) were placed in coaxial steel sleeves that were electrically and mechanically isolated and whose thickness and placement were optimized using E&M modeling software. Six sets of sleeves were placed 60° apart, 85 cm from isocenter. The Faraday effect occurs when the direction of propagation is parallel to the magnetic RF field component, rotating the RF polarization, subsequently diminishing RF power. The Faraday effect was avoided by orienting the waveguides such that the magnetic field RF component was parallel to the magnetic field. Results: The magnetic field within the shields was measured to be less than 40 Gauss, significantly below the amount needed for the magnetron and port circulator. Additional mu-metal was employed to reduce the magnetic field at the linear accelerator to less than 1 Gauss. The orientation of the RF waveguides allowed the RT transport with minimal loss and reflection. Conclusion: One of the major challenges in designing a compact linear accelerator based MRI-guided radiation therapy system, that of creating low magnetic field environments for the magnetic-field sensitive components, has been solved. The measured magnetic fields are sufficiently small to enable system integration. This work supported by ViewRay, Inc.

Adenosine stress cardiovascular magnetic resonance with variable-density spiral pulse sequences accurately detects coronary artery disease: initial clinical evaluation.

Science.gov (United States)

Salerno, Michael; Taylor, Angela; Yang, Yang; Kuruvilla, Sujith; Ragosta, Michael; Meyer, Craig H; Kramer, Christopher M

2014-07-01

Adenosine stress cardiovascular magnetic resonance perfusion imaging can be limited by motion-induced dark-rim artifacts, which may be mistaken for true perfusion abnormalities. A high-resolution variable-density spiral pulse sequence with a novel density compensation strategy has been shown to reduce dark-rim artifacts in first-pass perfusion imaging. We aimed to assess the clinical performance of adenosine stress cardiovascular magnetic resonance using this new perfusion sequence to detect obstructive coronary artery disease. Cardiovascular magnetic resonance perfusion imaging was performed during adenosine stress (140 μg/kg per minute) and at rest on a Siemens 1.5-T Avanto scanner in 41 subjects with chest pain scheduled for coronary angiography. Perfusion images were acquired during injection of 0.1 mmol/kg Gadolinium-diethylenetriaminepentacetate at 3 short-axis locations using a saturation recovery interleaved variable-density spiral pulse sequence. Significant stenosis was defined as >50% by quantitative coronary angiography. Two blinded reviewers evaluated the perfusion images for the presence of adenosine-induced perfusion abnormalities and assessed image quality using a 5-point scale (1 [poor] to 5 [excellent]). The prevalence of obstructive coronary artery disease by quantitative coronary angiography was 68%. The average sensitivity, specificity, and accuracy were 89%, 85%, and 88%, respectively, with a positive predictive value and negative predictive value of 93% and 79%, respectively. The average image quality score was 4.4±0.7, with only 1 study with more than mild dark-rim artifacts. There was good inter-reader reliability with a κ statistic of 0.67. Spiral adenosine stress cardiovascular magnetic resonance results in high diagnostic accuracy for the detection of obstructive coronary artery disease with excellent image quality and minimal dark-rim artifacts. © 2014 American Heart Association, Inc.

Cardiovascular magnetic resonance in the follow-up of patients with corrected tetralogy of Fallot: a review

NARCIS (Netherlands)

Oosterhof, Thomas; Mulder, Barbara J. M.; Vliegen, Hubert W.; de Roos, Albert

2006-01-01

Cardiovascular magnetic resonance (CMR) is becoming an important tool in the clinical management of patients with congenital heart disease. Because of the diverse problems patients may face after initial correction for tetralogy of Fallot and the large amount of CMR techniques that can be applied,

An FPGA-Based Quench Detection and Protection System for Superconducting Accelerator Magnets

CERN Document Server

Carcagno, Ruben H; Lamm, Michael J; Makulski, Andrzej; Nehring, Roger; Orris, Darryl; Pishchalnikov, Yu M; Tartaglia, M

2005-01-01

A new quench detection and protection system for superconducting accelerator magnets was developed at the Fermilab's Magnet Test Facility (MTF). This system is based on a Field-Programmable Gate Array (FPGA) module, and it is made of mostly commerically available, integrated hardware and software components. It provides most of the functionality of our existing VME-based quench detection and protection system, but in addition the new system is easily scalable to protect multiple magnets powered independently and has a more powerful user interface and analysis tools. First applications of the new system will be for testing corrector coil packages. In this paper we describe the new system and present results of testing LHC Interaction Region Quadrupole (IRQ) correctors.

Fiber Bragg Grating Sensors Based Monitoring System for Superconducting Accelerator Magnets

CERN Document Server

Chiuchiolo, A; Perez, J C; Bajas, H; Consales, M; Giordano, M; Breglio, G; Cusano, A

2014-01-01

New generation of accelerator magnets for high energy applications currently designed, manufactured and tested at the European Organization for Nuclear Research (CERN) require the implementation of precise cryogenic sensors with long-term robustness and reliability able to withstand cryogenic temperature and to monitor the mechanical stresses affecting the winding during all the stages of his service life, assembly, cool down and powering. Monitoring the mechanical behavior of the magnet from assembly to operation is a critical task which aims to assure the integrity of the magnet and to safely handle the coils made of new brittle material. This contribution deals with the first successful embedding of Fiber Bragg Grating sensors in a subscale Nb$_{3}$Sn dipole magnet in order to monitor the strain developed in the coil during the cool down to 1.9 K, the powering up to 15.8 kA and the warm up, offering new perspectives for the development of a complementary sensing technology based on fiber optic sensors.

Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma

Energy Technology Data Exchange (ETDEWEB)

Werner, Gregory R.; Uzdensky, Dmitri A., E-mail: Greg.Werner@colorado.edu [Center for Integrated Plasma Studies, Physics Department, University of Colorado, 390 UCB, Boulder, CO 80309 (United States)

2017-07-10

As a fundamental process converting magnetic to plasma energy in high-energy astrophysical plasmas, relativistic magnetic reconnection is a leading explanation for the acceleration of particles to the ultrarelativistic energies that are necessary to power nonthermal emission (especially X-rays and gamma-rays) in pulsar magnetospheres and pulsar wind nebulae, coronae and jets of accreting black holes, and gamma-ray bursts. An important objective of plasma astrophysics is therefore the characterization of nonthermal particle acceleration (NTPA) effected by reconnection. Reconnection-powered NTPA has been demonstrated over a wide range of physical conditions using large 2D kinetic simulations. However, its robustness in realistic 3D reconnection—in particular, whether the 3D relativistic drift-kink instability (RDKI) disrupts NTPA—has not been systematically investigated, although pioneering 3D simulations have observed NTPA in isolated cases. Here, we present the first comprehensive study of NTPA in 3D relativistic reconnection in collisionless electron–positron plasmas, characterizing NTPA as the strength of 3D effects is varied systematically via the length in the third dimension and the strength of the guide magnetic field. We find that, while the RDKI prominently perturbs 3D reconnecting current sheets, it does not suppress particle acceleration, even for zero guide field; fully 3D reconnection robustly and efficiently produces nonthermal power-law particle spectra closely resembling those obtained in 2D. This finding provides strong support for reconnection as the key mechanism powering high-energy flares in various astrophysical systems. We also show that strong guide fields significantly inhibit NTPA, slowing reconnection and limiting the energy available for plasma energization, yielding steeper and shorter power-law spectra.

Design of MgB2 superconducting dipole magnet for particle beam transport in accelerators

International Nuclear Information System (INIS)

Abrahamsen, A.B.; Givel, J.C.; Andersen, N.H.; Zangenberg, N.; Baurichter, A.

2006-11-01

A comprehensive analysis of the innovation potential of superconductivity at Risoe was performed in February 2004 by the main author of this report. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risoe. The existing markets of superconducting technology is within highly specialized scientific areas such as magnetic confinement in fusion energy, sample environment in neutron scattering and large scale accelerators such as the Large Hadron Collider(LHC) at Cern, or in the nuclear magnetic resonance (NMR) community using MR-imaging scanners in medicine and phase identification in organic chemistry. Only the NMR applications can be categorized as a highly profitable and commercial market today. The superconductivity group of Risoe formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept, but further initiatives were stopped due to unclear patent possibilities. The experience of the innovation review was used in the STVF framework program 'New superconductors: mechanisms, processes and products' to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition in building resistive magnets for particle accelerators. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European Framework Program 6 project HIPERMAG. It was presented at the Risoe innovation seminar January 2006, and recently a collaboration between Risoe and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB 2 superconductors in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the

Vp x B acceleration

International Nuclear Information System (INIS)

Sugihara, Ryo.

1987-05-01

A unique particle acceleration by an electrostatic (ES) wave, a magnetosonic shock wave as well as an electromagnetic (EM) wave is reviewed. The principle of the acceleration is that when a charged particle is carried across an external magnetic field the charge feels a DC field (the Lorentz force) and is accelerated. The theory for the ES wave acceleration is experimentally verified thought it is semi-quantitative. The shock acceleration is extensively studied theoretically and in a particle simulation method and the application is extended to phenomena in interplanetary space. The EM wave acceleration is based on a trapping in a moving neutral sheet created by the wave magnetic field and the external magnetic field, and the particle can be accelerated indefinitely. A brief sketch on a slow-wave-structure for this acceleration will be given. (author)

Generation of mesoscale magnetic fields and the dynamics of Cosmic Ray acceleration

Science.gov (United States)

Diamond, P. H.; Malkov, M. A.

The problem of the cosmic ray origin is discussed in connection with their acceleration in supernova remnant shocks. The diffusive shock acceleration mechanism is reviewed and its potential to accelerate particles to the maximum energy of (presumably) galactic cosmic rays (1018eV ) is considered. It is argued that to reach such energies, a strong magnetic field at scales larger than the particle gyroradius must be created as a result of the acceleration process, itself. One specific mechanism suggested here is based on the generation of Alfven wave at the gyroradius scale with a subsequent transfer to longer scales via interaction with strong acoustic turbulence in the shock precursor. The acoustic turbulence in turn, may be generated by Drury instability or by parametric instability of the Alfven waves. The generation mechanism is modulational instability of CR generated Alfven wave packets induced, in turn, by scattering off acoustic fluctuations in the shock precursor which are generated by Drury instability.

A Scaling Law for the Snapback in Superconducting Accelerator Magnets

CERN Document Server

Bottura, L; Bauer, P; Haverkamp, M; Pieloni, T; Sanfilippo, S; Velev, G

2005-01-01

The decay of the sextupole component in the bending dipoles during injection and the subsequent snapback at the start of beam acceleration are issues of common concern for all superconducting colliders built or in construction. Recent studies performed on LHC and Tevatron dipole magnets revealed many similarities in the snapback characteristics. Some are expected, e.g. the effect of operational history. One particular similarity, however, is striking and is the subject of this paper. It appears that there is a simple linear relation between the amount of sextupole drift during the decay and the magnet current (or field) change during the ramp required to resolve the snapback. It is surprising that the linear correlation between snapback amplitude and snapback field holds very well for all magnets of the same family (e.g. Tevatron or LHC dipoles). In this paper we present the data collected to date and discuss a simple theory that explains the scaling found.

Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers

International Nuclear Information System (INIS)

Goodzeit, C.L.; Anerella, M.D.; Ganetis, G.L.

1988-01-01

An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effect in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation. 13 figs., 1 tab

Intense laser driven collision-less shock and ion acceleration in magnetized plasmas

Science.gov (United States)

Mima, K.; Jia, Q.; Cai, H. B.; Taguchi, T.; Nagatomo, H.; Sanz, J. R.; Honrubia, J.

2016-05-01

The generation of strong magnetic field with a laser driven coil has been demonstrated by many experiments. It is applicable to the magnetized fast ignition (MFI), the collision-less shock in the astrophysics and the ion shock acceleration. In this paper, the longitudinal magnetic field effect on the shock wave driven by the radiation pressure of an intense short pulse laser is investigated by theory and simulations. The transition of a laminar shock (electro static shock) to the turbulent shock (electromagnetic shock) occurs, when the external magnetic field is applied in near relativistic cut-off density plasmas. This transition leads to the enhancement of conversion of the laser energy into high energy ions. The enhancement of the conversion efficiency is important for the ion driven fast ignition and the laser driven neutron source. It is found that the total number of ions reflected by the shock increases by six time when the magnetic field is applied.

Isometric stress in cardiovascular magnetic resonance - a simple and easily replicable method of assessing cardiovascular differences not apparent at rest

International Nuclear Information System (INIS)

Mortensen, Kristian H.; Jones, Alexander; Steeden, Jennifer A.; Taylor, Andrew M.; Muthurangu, Vivek

2016-01-01

Isometric exercise may unmask cardiovascular disease not evident at rest, and cardiovascular magnetic resonance (CMR) imaging is proven for comprehensive resting assessment. This study devised a simple isometric exercise CMR methodology and assessed the hemodynamic response evoked by isometric exercise. A biceps isometric exercise technique was devised for CMR, and 75 healthy volunteers were assessed at rest, after 3-minute biceps exercise, and 5-minute of recovery using: (1) blood pressure (BP) and (2) CMR measured aortic flow and left ventricular function. Total peripheral resistance (SVR) and arterial compliance (TAC), cardiac output (CO), left ventricular volumes and function (ejection fraction, stroke volume, power output), blood pressure (BP), heart rate (HR), and rate pressure product were assessed at all time points. Image quality was preserved during stress. During exercise there were increases in CO (+14.9 %), HR (+17.0 %), SVR (+9.8 %), systolic BP (+22.4 %), diastolic BP (+25.4 %) and mean BP (+23.2 %). In addition, there were decreases in TAC (-22.0 %) and left ventricular ejection fraction (-6.3 %). Age and body mass index modified the evoked response, even when resting measures were similar. Isometric exercise technique evokes a significant cardiovascular response in CMR, unmasking physiological differences that are not apparent at rest. (orig.)

Isometric stress in cardiovascular magnetic resonance - a simple and easily replicable method of assessing cardiovascular differences not apparent at rest

Energy Technology Data Exchange (ETDEWEB)

Mortensen, Kristian H.; Jones, Alexander; Steeden, Jennifer A.; Taylor, Andrew M.; Muthurangu, Vivek [UCL Centre for Cardiovascular MR, UCL Institute of Cardiovascular Science, Level 6 Old Nurses Home, Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London (United Kingdom)

2016-04-15

Isometric exercise may unmask cardiovascular disease not evident at rest, and cardiovascular magnetic resonance (CMR) imaging is proven for comprehensive resting assessment. This study devised a simple isometric exercise CMR methodology and assessed the hemodynamic response evoked by isometric exercise. A biceps isometric exercise technique was devised for CMR, and 75 healthy volunteers were assessed at rest, after 3-minute biceps exercise, and 5-minute of recovery using: (1) blood pressure (BP) and (2) CMR measured aortic flow and left ventricular function. Total peripheral resistance (SVR) and arterial compliance (TAC), cardiac output (CO), left ventricular volumes and function (ejection fraction, stroke volume, power output), blood pressure (BP), heart rate (HR), and rate pressure product were assessed at all time points. Image quality was preserved during stress. During exercise there were increases in CO (+14.9 %), HR (+17.0 %), SVR (+9.8 %), systolic BP (+22.4 %), diastolic BP (+25.4 %) and mean BP (+23.2 %). In addition, there were decreases in TAC (-22.0 %) and left ventricular ejection fraction (-6.3 %). Age and body mass index modified the evoked response, even when resting measures were similar. Isometric exercise technique evokes a significant cardiovascular response in CMR, unmasking physiological differences that are not apparent at rest. (orig.)

Plasma particle accelerators

International Nuclear Information System (INIS)

Dawson, J.M.

1988-01-01

The Superconducting Supercollider (SSC) will require an 87-kilometer accelerator ring to boost particles to 40 TeV. The SSC's size is due in part to the fact that its operating principle is the same one that has dominated accelerator design for 50 years: it guides particles by means of magnetic fields and propels them by strong electric fields. If one were to build an equally powerful but smaller accelerator, one would need to increase the strength of the guiding and propelling fields. Actually, however, conventional technology may not be able to provide significant increases in field strength. There are two reasons. First, the forces from magnetic fields are becoming greater than the structural forces that hold a magnetic material together; the magnets that produce these fields would themselves be torn apart. Second, the energy from electric fields is reaching the energies that bind electrons to atoms; it would tear electrons from nuclei in the accelerator's support structures. It is the electric field problem that plasma accelerators can overcome. Plasma particle accelerators are based on the principle that particles can be accelerated by the electric fields generated within a plasma. Because the plasma has already been ionized, plasma particle accelerators are not susceptible to electron dissociation. They can in theory sustain accelerating fields thousands of times stronger that conventional technologies. So far two methods for creating plasma waves for accelerators have been proposed and tested: the wakefield and the beat wave. Although promising electric fields have been produced, more research is necessary to determine whether plasma particle accelerators can compete with the existing accelerators. 7 figs

Double-layer ion acceleration triggered by ion magnetization in expanding radiofrequency plasma sources

International Nuclear Information System (INIS)

Takahashi, Kazunori; Charles, Christine; Boswell, Rod W.; Fujiwara, Tamiya

2010-01-01

Ion energy distribution functions downstream of the source exit in magnetically expanding low-pressure plasmas are experimentally investigated for four source tube diameters ranging from about 5 to 15 cm. The magnetic-field threshold corresponding to a transition from a simple expanding plasma to a double layer-containing plasma is observed to increase with a decrease in the source tube diameter. The results demonstrate that for the four geometries, the double layer and the accelerated ion beam form when the ion Larmour radius in the source becomes smaller than the source tube radius, i.e., when the ions become magnetized in the source tube.

Gamma radiation and magnetic field mediated delay in effect of accelerated ageing of soybean

International Nuclear Information System (INIS)

Mahesh Kumar; Anand, Anjali; Singh, Bhupinder; Ahuja, Sumedha; Dahuja, Anil

2015-01-01

Soybean seeds were exposed to gamma radiation (0.5, 1, 3 and 5 kGy), static magnetic field (50, 100 and 200 mT) and a combination of gamma radiation and magnetic energy (0.5 kGy+200 mT and 5 kGy+50 mT) and stored at room temperature for six months. These seeds were later subjected to accelerated ageing treatment at 42°C temperature and 95-100 % relative humidity and were compared for various physical and biochemical characteristics between the untreated and the energized treatments. Energy treatment protected the quality of stored seeds in terms of its protein and oil content. Accelerated aging conditions, however, affected the oil and protein quantity and quality of seed negatively. Antioxidant enzymes exhibited a decline in their activity during aging while the LOX activity, which reflects the rate of lipid peroxidation, in general, increased during the aging. Gamma irradiated (3 and 5 kGy) and magnetic field treated seeds (100 and 200 mT) maintained a higher catalase and ascorbate peroxidase activity which may help in efficient scavenging of deleterious free radical produced during the aging. Aging caused peroxidative changes to lipids, which could be contributed to the loss of oil quality. Among the electromagnetic energy treatments, a dose of 1-5 kGy of gamma and 100 mT, 200 mT magnetic field effectively slowed the rate of biochemical degradation and loss of cellular integrity in seeds stored under conditions of accelerated aging and thus, protected the deterioration of seed quality. Energy combination treatments did not yield any additional protection advantage. (author)

Accurate Calculation of Magnetic Fields in the End Regions of Superconducting Accelerator Magnets using the BEM-FEM Coupling Method

CERN Document Server

Kurz, S

1999-01-01

In this paper a new technique for the accurate calculation of magnetic fields in the end regions of superconducting accelerator magnets is presented. This method couples Boundary Elements (BEM) which discretize the surface of the iron yoke and Finite Elements (FEM) for the modelling of the nonlinear interior of the yoke. The BEM-FEM method is therefore specially suited for the calculation of 3-dimensional effects in the magnets, as the coils and the air regions do not have to be represented in the finite-element mesh and discretization errors only influence the calculation of the magnetization (reduced field) of the yoke. The method has been recently implemented into the CERN-ROXIE program package for the design and optimization of the LHC magnets. The field shape and multipole errors in the two-in-one LHC dipoles with its coil ends sticking out of the common iron yoke is presented.

Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence

Science.gov (United States)

Montag, Peter; Egedal, Jan; Lichko, Emily; Wetherton, Blake

2017-10-01

Previous work has shown that Fermi acceleration can be an effective heating mechanism during magnetic island coalescence, where electrons may undergo repeated reflections as the magnetic field lines contract. This energization has the potential to account for the power-law distributions of particle energy inferred from observations of solar flares. Here, we develop a generalized framework for the analysis of Fermi acceleration that can incorporate the effects of compressibility and non-uniformity along field lines, which have commonly been neglected in previous treatments of the problem. Applying this framework to the simplified case of the uniform flux tube allows us to find both the power-law scaling of the distribution function and the rate at which the power-law behavior develops. We find that a guide magnetic field of order unity effectively suppresses the development of power-law distributions. The work was supported by NASA Grant No. NNX14AC68G, NSF GEM Grant No. 1405166, NSF Award 1404166, and NASA Award NNX15AJ73G.

Results from the RACE [Ring ACceleration Experiment] Compact Torus Acceleration Experiment

International Nuclear Information System (INIS)

Hammer, J.H.; Hartman, C.W.; Eddleman, J.L.; Kusse, B.

1987-06-01

RACE (Ring ACceleration Experiment) is a proof-of-principle experiment aimed at demonstrating acceleration of magnetically confined compact torus plasma rings to directed kinetic energies well in excess of their magnetic and thermal energies. In the course of the first year of operation the following have been observed: successful formation of rings in the RACE geometry; acceleration of rings with large forces, F/sub accelerate/ ∼F/sub equilibrium/ without apparent degradation of the ring structure; peak velocities of ≅2.5 x 10 8 cm/sec; acceleration efficiency of >30% at speeds of 1.5 x 10 8 cm/sec inferred from trajectory and capacitor bank data; kinetic to magnetic energy ratios ∼10 were observed. Experiments in the near future will be aimed at confirmation of the mass/energy measurements by calorimetry and direct density measurements

Devices for launching 0.1-g projectiles to 150 km/s or more to initiate fusion. Part 1. Magnetic-gradient and electrostatic accelerators

International Nuclear Information System (INIS)

Brittingham, J.N.

1979-01-01

The feasibility of using magnetic-gradient and electrostatic accelerators to launch a 0.1-g projectile to hypervelocities (150 km/s or more) is studied. Such hypervelocity projectiles could be used to ignite deuterium-tritium fuel pellets in a fusion reactor. For the magnetic-gradient accelerator, several types of projectile were studied: shielded and unshielded copper, ferromagnetic, and superconducting. The calculations revealed the superconducting projectile to be the best of those materials. It would require a 3.2-km-long magnetic-gradient accelerator and achieve a 92% efficiency. This accelerator-projectile combination would be the one most likely to launch a 0.1-g projectile to 150 km/s or more. Its components would cost $58.9 million. The electrostatic accelerator was found to be impractical because of its excessive length of 23 km

Radiation Field Forming for Industrial Electron Accelerators Using Rare-Earth Magnetic Materials

Science.gov (United States)

Ermakov, A. N.; Khankin, V. V.; Shvedunov, N. V.; Shvedunov, V. I.; Yurov, D. S.

2016-09-01

The article describes the radiation field forming system for industrial electron accelerators, which would have uniform distribution of linear charge density at the surface of an item being irradiated perpendicular to the direction of its motion. Its main element is non-linear quadrupole lens made with the use of rare-earth magnetic materials. The proposed system has a number of advantages over traditional beam scanning systems that use electromagnets, including easier product irradiation planning, lower instantaneous local dose rate, smaller size, lower cost. Provided are the calculation results for a 10 MeV industrial electron accelerator, as well as measurement results for current distribution in the prototype build based on calculations.

Magnetic field design for a Penning ion source for a 200 keV electrostatic accelerator

Energy Technology Data Exchange (ETDEWEB)

Fathi, A., E-mail: Atefeh.Fathi115@gmail.com [Radiation Applications Department, Shahid Beheshti University, G. C., Tehran (Iran, Islamic Republic of); Feghhi, S.A.H.; Sadati, S.M. [Radiation Applications Department, Shahid Beheshti University, G. C., Tehran (Iran, Islamic Republic of); Ebrahimibasabi, E. [Department of Physics, Shahrood University of Technology, 3619995161, Shahrood (Iran, Islamic Republic of)

2017-04-01

In this study, the structure of magnetic field for a Penning ion source has been designed and constructed with the use of permanent magnets. The ion source has been designed and constructed for a 200 keV electrostatic accelerator. With using CST Studio Suite, the magnetic field profile inside the ion source was simulated and an appropriate magnetic system was designed to improve particle confinement. Designed system consists of two ring magnets with 9 mm distance from each other around the anode. The ion source was constructed and the cylindrical magnet and designed magnetic system were tested on the ion source. The results showed that the ignition voltage for ion source with the designed magnetic system is almost 300 V lower than the ion source with the cylindrical magnet. Better particle confinement causes lower voltage discharge to occur.

Non Hodgkin lymphoma metastasis to the heart detected by cardiovascular magnetic resonance

International Nuclear Information System (INIS)

Martinez, Florange; Morales, Marisela; Pedreanez, Norma; Pabon, Luz; Carrillo, Milton

2009-01-01

Primary and secondary heart tumors are relatively rare occurrences but usually imply significant treatment decisions. The differential diagnosis among these tumors and other masses can sometimes be difficult and require the use of different imaging modalities to establish a confident verdict. Cardiovascular magnetic resonance CMR imaging is a very useful tool in these cases by allowing for the application of different strategies to better delineate masses, heart structures and adjacent tissues. In this case description, we present a woman with shortness of breath and a paracardiac mass showing how CMR can be applied. (author)

Cardiovascular Magnetic Resonance T2-STIR Imaging is Unable to Discriminate Between Intramyocardial Haemorrhage and Microvascular Obstruction

DEFF Research Database (Denmark)

Søvsø Szocska Hansen, Esben; Pedersen, Steen Fjord; Pedersen, Steen Bønløkke

2015-01-01

Recent studies have used cardiovascular magnetic resonance (CMR) and T2-weighted short tau inversion recovery (T2-STIR) imaging to detect intramyocardial haemorrhage (IMH) as a measure of ischemic/reperfusion injury. We investigated the ability of T2-STIR to differentiate between microvascular...

Measurement of asymmetric optical pumping of ions accelerating in a magnetic-field gradient

International Nuclear Information System (INIS)

Sun Xuan; Scime, Earl; Miah, Mahmood; Cohen, Samuel; Skiff, Frederick

2004-01-01

We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic-field gradient. The signature is a difference in the laser-induced-fluorescence emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities

Measurement of Asymmetric Optical Pumping of Ions Accelerating in a Magnetic-field Gradient

Energy Technology Data Exchange (ETDEWEB)

Xuan Sun; Earl Scime; Mahmood Miah; Samuel Cohen; Frederick Skiff

2004-10-28

We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic field gradient. The signature is a difference in the laser-induced-fluorescence (LIF) emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities.

Measurement of Asymmetric Optical Pumping of Ions Accelerating in a Magnetic-field Gradient

International Nuclear Information System (INIS)

Xuan Sun; Earl Scime; Mahmood Miah; Samuel Cohen; Frederick Skiff

2004-01-01

We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic field gradient. The signature is a difference in the laser-induced-fluorescence (LIF) emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities

Cardiovascular Magnetic Resonance Imaging—Incremental Value in a Series of 361 Patients Demonstrating Cost Savings and Clinical Benefits: An Outcome-Based Study

Science.gov (United States)

Hegde, Vinayak A; Biederman, Robert WW; Mikolich, J Ronald

2017-01-01

BACKGROUND This study was designed to assess the clinical impact and cost-benefit of cardiovascular magnetic resonance imaging (CMR). In the face of current health care cost concerns, cardiac imaging modalities have come under focused review. Data related to CMR clinical impact and cost-benefit are lacking. METHODS AND RESULTS Retrospective review of 361 consecutive patients (pts) who underwent CMR exams was conducted. Indications for CMR were tabulated for appropriateness criteria. Components of the CMR exam were identified along with evidence of clinical impact. The cost of each CMR exam was ascertained along with cost savings attributable to the CMR exam for calculation of an incremental cost-effectiveness ratio. A total of 354 of 361 pts (98%) had diagnostic quality studies. Of the 361 pts, 350 (97%) had at least 1 published Appropriateness Criterion for CMR. A significant clinical impact attributable to CMR exam results was observed in 256 of 361 pts (71%). The CMR exam resulted in a new diagnosis in 69 of 361 (27%) pts. Cardiovascular magnetic resonance imaging results avoided invasive procedures in 38 (11%) pts and prevented additional diagnostic testing in 26 (7%) pts. Comparison of health care savings using CMR as opposed to current standards of care showed a net cost savings of $833 037, ie, per patient cost savings of $2308. CONCLUSIONS Cardiovascular magnetic resonance imaging provides diagnostic image quality in >98% of cases. Cardiovascular magnetic resonance imaging findings have documentable clinical impact on patient management in 71% of pts undergoing the exam, in a cost beneficial manner. PMID:28579858

Cardiovascular Magnetic Resonance Imaging-Incremental Value in a Series of 361 Patients Demonstrating Cost Savings and Clinical Benefits: An Outcome-Based Study.

Science.gov (United States)

Hegde, Vinayak A; Biederman, Robert Ww; Mikolich, J Ronald

2017-01-01

This study was designed to assess the clinical impact and cost-benefit of cardiovascular magnetic resonance imaging (CMR). In the face of current health care cost concerns, cardiac imaging modalities have come under focused review. Data related to CMR clinical impact and cost-benefit are lacking. Retrospective review of 361 consecutive patients (pts) who underwent CMR exams was conducted. Indications for CMR were tabulated for appropriateness criteria. Components of the CMR exam were identified along with evidence of clinical impact. The cost of each CMR exam was ascertained along with cost savings attributable to the CMR exam for calculation of an incremental cost-effectiveness ratio. A total of 354 of 361 pts (98%) had diagnostic quality studies. Of the 361 pts, 350 (97%) had at least 1 published Appropriateness Criterion for CMR. A significant clinical impact attributable to CMR exam results was observed in 256 of 361 pts (71%). The CMR exam resulted in a new diagnosis in 69 of 361 (27%) pts. Cardiovascular magnetic resonance imaging results avoided invasive procedures in 38 (11%) pts and prevented additional diagnostic testing in 26 (7%) pts. Comparison of health care savings using CMR as opposed to current standards of care showed a net cost savings of $833 037, ie, per patient cost savings of $2308. Cardiovascular magnetic resonance imaging provides diagnostic image quality in >98% of cases. Cardiovascular magnetic resonance imaging findings have documentable clinical impact on patient management in 71% of pts undergoing the exam, in a cost beneficial manner.

Cardiovascular Magnetic Resonance Imaging—Incremental Value in a Series of 361 Patients Demonstrating Cost Savings and Clinical Benefits: An Outcome-Based Study

Directory of Open Access Journals (Sweden)

Vinayak A Hegde

2017-05-01

Full Text Available Background: This study was designed to assess the clinical impact and cost-benefit of cardiovascular magnetic resonance imaging (CMR. In the face of current health care cost concerns, cardiac imaging modalities have come under focused review. Data related to CMR clinical impact and cost-benefit are lacking. Methods and Results: Retrospective review of 361 consecutive patients (pts who underwent CMR exams was conducted. Indications for CMR were tabulated for appropriateness criteria. Components of the CMR exam were identified along with evidence of clinical impact. The cost of each CMR exam was ascertained along with cost savings attributable to the CMR exam for calculation of an incremental cost-effectiveness ratio. A total of 354 of 361 pts (98% had diagnostic quality studies. Of the 361 pts, 350 (97% had at least 1 published Appropriateness Criterion for CMR. A significant clinical impact attributable to CMR exam results was observed in 256 of 361 pts (71%. The CMR exam resulted in a new diagnosis in 69 of 361 (27% pts. Cardiovascular magnetic resonance imaging results avoided invasive procedures in 38 (11% pts and prevented additional diagnostic testing in 26 (7% pts. Comparison of health care savings using CMR as opposed to current standards of care showed a net cost savings of $833 037, ie, per patient cost savings of $2308. Conclusions: Cardiovascular magnetic resonance imaging provides diagnostic image quality in >98% of cases. Cardiovascular magnetic resonance imaging findings have documentable clinical impact on patient management in 71% of pts undergoing the exam, in a cost beneficial manner.

An in situ accelerator-based diagnostic for plasma-material interactions science on magnetic fusion devices.

Science.gov (United States)

Hartwig, Zachary S; Barnard, Harold S; Lanza, Richard C; Sorbom, Brandon N; Stahle, Peter W; Whyte, Dennis G

2013-12-01

This paper presents a novel particle accelerator-based diagnostic that nondestructively measures the evolution of material surface compositions inside magnetic fusion devices. The diagnostic's purpose is to contribute to an integrated understanding of plasma-material interactions in magnetic fusion, which is severely hindered by a dearth of in situ material surface diagnosis. The diagnostic aims to remotely generate isotopic concentration maps on a plasma shot-to-shot timescale that cover a large fraction of the plasma-facing surface inside of a magnetic fusion device without the need for vacuum breaks or physical access to the material surfaces. Our instrument uses a compact (~1 m), high-current (~1 milliamp) radio-frequency quadrupole accelerator to inject 0.9 MeV deuterons into the Alcator C-Mod tokamak at MIT. We control the tokamak magnetic fields--in between plasma shots--to steer the deuterons to material surfaces where the deuterons cause high-Q nuclear reactions with low-Z isotopes ~5 μm into the material. The induced neutrons and gamma rays are measured with scintillation detectors; energy spectra analysis provides quantitative reconstruction of surface compositions. An overview of the diagnostic technique, known as accelerator-based in situ materials surveillance (AIMS), and the first AIMS diagnostic on the Alcator C-Mod tokamak is given. Experimental validation is shown to demonstrate that an optimized deuteron beam is injected into the tokamak, that low-Z isotopes such as deuterium and boron can be quantified on the material surfaces, and that magnetic steering provides access to different measurement locations. The first AIMS analysis, which measures the relative change in deuterium at a single surface location at the end of the Alcator C-Mod FY2012 plasma campaign, is also presented.

Design of MgB{sub 2} superconducting dipole magnet for particle beam transport in accelerators

Energy Technology Data Exchange (ETDEWEB)

Abrahamsen, A.B.; Givel, J.C.; Andersen, N.H. [Risoe National Lab., Materials Research Dept., Roskilde (Denmark); Zangenberg, N.; Baurichter, A. [Danfysik A/S, Jyllinge (Denmark)

2006-11-15

A comprehensive analysis of the innovation potential of superconductivity at Risoe was performed in February 2004 by the main author of this report. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risoe. The existing markets of superconducting technology is within highly specialized scientific areas such as magnetic confinement in fusion energy, sample environment in neutron scattering and large scale accelerators such as the Large Hadron Collider(LHC) at Cern, or in the nuclear magnetic resonance (NMR) community using MR-imaging scanners in medicine and phase identification in organic chemistry. Only the NMR applications can be categorized as a highly profitable and commercial market today. The superconductivity group of Risoe formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept, but further initiatives were stopped due to unclear patent possibilities. The experience of the innovation review was used in the STVF framework program 'New superconductors: mechanisms, processes and products' to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition in building resistive magnets for particle accelerators. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European Framework Program 6 project HIPERMAG. It was presented at the Risoe innovation seminar January 2006, and recently a collaboration between Risoe and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB{sub 2} superconductors in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive

Stochastic acceleration by a single wave in a magnetized plasma

International Nuclear Information System (INIS)

Smith, R.

1977-01-01

A particularly simple problem exhibiting stochasticity is the motion of a charged particle in a uniform magnetic field and a single wave. Detailed studies of this wave-particle interaction show the following features. An electrostatic wave propagating obliquely to the magnetic field causes stochastic motion if the wave amplitude exceeds a certain threshold. The overlap of cyclotron resonances then destroys a constant of the motion, allowing strong particle acceleration. A wave of large enough amplitude would thus suffer severe damping and lead to rapid heating of a particle distribution. The stochastic motion resembles a diffusion process even though the wave spectrum contains only a single wave. The motion of ions in a nonuniform magnetic field and a single electrostatic wave is treated in our study of a possible saturation mechanism of the dissipative trapped-ion instability in a tokamak. A theory involving the overlap of bounce resonances predicts the main features found in the numerical integration of the equations of motion. Ions in a layer near the trapped-circulating boundary move stochastically. This motion leads to nonlinear stabilization mechanisms which are described qualitatively

Pulmonary Arterial Hypertension: Use of Delayed Contrast-Enhanced Cardiovascular Magnetic Resonance in Risk Assessment

International Nuclear Information System (INIS)

Bessa, Luiz Gustavo Pignataro; Junqueira, Flávia Pegado; Bandeira, Marcelo Luiz da Silva; Garcia, Marcelo Iorio; Xavier, Sérgio Salles; Lavall, Guilherme; Torres, Diego; Waetge, Daniel

2013-01-01

Pulmonary arterial hypertension is a severe and progressive disease. Its early diagnosis is the greatest clinical challenge. To evaluate the presence and extension of the delayed myocardial contrast-enhanced cardiovascular magnetic resonance, as well as to verify if the percentage of the myocardial fibrosis mass is a severity predictor. Cross-sectional study with 30 patients with pulmonary arterial hypertension of groups I and IV, subjected to clinical, functional and hemodynamic evaluation, and to cardiac magnetic resonance. The mean age of patients was 52 years old, with female predominance (77%). Among the patients, 53% had right ventricular failure at diagnosis, and 90% were in functional class II/III. The mean of the 6-minute walk test was 395m. In hemodynamic study with right catheterism, the mean average pulmonary arterial pressure was 53.3mmHg, of the cardiac index of 2.1L/ min.m 2 , and median right atrial pressure was 13.5 mmHg. Delayed myocardial contrast enhanced cardiovascular magnetic resonance was found in 28 patients. The mean fibrosis mass was 9.9 g and the median percentage of fibrosis mass was 6.17%. The presence of functional class IV, right ventricular failure at diagnosis, 6-minute walk test < 300 meters and right atrial pressure ≥ 15 mmHg, with cardiac index < 2.0 L/ min.m 2 , there was a relevant association with the increased percentage of myocardial fibrosis. The percentage of the myocardial fibrosis mass indicates a non-invasive marker with promising perspectives in identifying patients with high risk factors for pulmonary hypertension

Pulmonary Arterial Hypertension: Use of Delayed Contrast-Enhanced Cardiovascular Magnetic Resonance in Risk Assessment

Energy Technology Data Exchange (ETDEWEB)

Bessa, Luiz Gustavo Pignataro, E-mail: lgpignataro@ig.com.br; Junqueira, Flávia Pegado; Bandeira, Marcelo Luiz da Silva; Garcia, Marcelo Iorio; Xavier, Sérgio Salles; Lavall, Guilherme; Torres, Diego; Waetge, Daniel [Hospital Universitário Clementino Fraga Filho, Ilha do Fundão, RJ (Brazil)

2013-10-15

Pulmonary arterial hypertension is a severe and progressive disease. Its early diagnosis is the greatest clinical challenge. To evaluate the presence and extension of the delayed myocardial contrast-enhanced cardiovascular magnetic resonance, as well as to verify if the percentage of the myocardial fibrosis mass is a severity predictor. Cross-sectional study with 30 patients with pulmonary arterial hypertension of groups I and IV, subjected to clinical, functional and hemodynamic evaluation, and to cardiac magnetic resonance. The mean age of patients was 52 years old, with female predominance (77%). Among the patients, 53% had right ventricular failure at diagnosis, and 90% were in functional class II/III. The mean of the 6-minute walk test was 395m. In hemodynamic study with right catheterism, the mean average pulmonary arterial pressure was 53.3mmHg, of the cardiac index of 2.1L/ min.m{sup 2}, and median right atrial pressure was 13.5 mmHg. Delayed myocardial contrast enhanced cardiovascular magnetic resonance was found in 28 patients. The mean fibrosis mass was 9.9 g and the median percentage of fibrosis mass was 6.17%. The presence of functional class IV, right ventricular failure at diagnosis, 6-minute walk test < 300 meters and right atrial pressure ≥ 15 mmHg, with cardiac index < 2.0 L/ min.m{sup 2}, there was a relevant association with the increased percentage of myocardial fibrosis. The percentage of the myocardial fibrosis mass indicates a non-invasive marker with promising perspectives in identifying patients with high risk factors for pulmonary hypertension.

Cardiovascular magnetic resonance frontiers: Tissue characterisation with mapping

Directory of Open Access Journals (Sweden)

Rebecca Schofield

2016-11-01

Full Text Available The clinical use of cardiovascular magnetic resonance (CMR imaging has expanded rapidly over the last decade. Its role in cardiac morphological and functional assessment is established, with perfusion and late gadolinium enhancement (LGE imaging for scar increasingly used in day-to-day clinical decision making. LGE allows a virtual histological assessment of the myocardium, with the pattern of scar suggesting disease aetiology, and the extent of predicting risk. However, even combined, the full range of pathological processes occurring in the myocardium are not interrogated. Mapping is a new frontier where the intrinsic magnetic properties of heart muscle are measured to probe further. T1, T2 and T2* mapping measures the three fundamental tissue relaxation rate constants before contrast, and the extracellular volume (ECV after contrast. These are displayed in colour, often providing an immediate appreciation of pathology. These parameters are differently sensitive to pathologies. Iron (cardiac siderosis, intramyocardial haemorrhage makes T1, T2 and T2* fall. T2 also falls with fat infiltration (Fabry disease. T2 increases with oedema (acute infarction, takotsubo cardiomyopathy, myocarditis, rheumatological disease. Native T1 increases with fibrosis, oedema and amyloid. Some of these changes are large (e.g. iron, oedema, amyloid, others more modest (diffuse fibrosis. They can be used to detect early disease, distinguish aetiology and, in some circumstances, guide therapy. In this review, we discuss these processes, illustrating clinical application and future advances.

EXTREME PARTICLE ACCELERATION IN MAGNETIC RECONNECTION LAYERS: APPLICATION TO THE GAMMA-RAY FLARES IN THE CRAB NEBULA

Energy Technology Data Exchange (ETDEWEB)

Cerutti, Benoit; Uzdensky, Dmitri A. [CIPS, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Begelman, Mitchell C., E-mail: benoit.cerutti@colorado.edu, E-mail: uzdensky@colorado.edu, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, UCB 440, Boulder, CO 80309-0440 (United States)

2012-02-20

The gamma-ray space telescopes AGILE and Fermi detected short and bright synchrotron gamma-ray flares at photon energies above 100 MeV in the Crab Nebula. This discovery suggests that electron-positron pairs in the nebula are accelerated to PeV energies in a milligauss magnetic field, which is difficult to explain with classical models of particle acceleration and pulsar wind nebulae. We investigate whether particle acceleration in a magnetic reconnection layer can account for the puzzling properties of the flares. We numerically integrate relativistic test-particle orbits in the vicinity of the layer, including the radiation reaction force, and using analytical expressions for the large-scale electromagnetic fields. As they get accelerated by the reconnection electric field, the particles are focused deep inside the current layer where the magnetic field is small. The electrons suffer less from synchrotron losses and are accelerated to extremely high energies. Population studies show that, at the end of the layer, the particle distribution piles up at the maximum energy given by the electric potential drop and is focused into a thin fan beam. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum peaks above 100 MeV and is close to the spectral shape of a single electron. The flare inverse Compton emission is negligible and no detectable emission is expected at other wavelengths. This mechanism provides a plausible explanation for the gamma-ray flares in the Crab Nebula and could be at work in other astrophysical objects such as relativistic jets in active galactic nuclei.

EXTREME PARTICLE ACCELERATION IN MAGNETIC RECONNECTION LAYERS: APPLICATION TO THE GAMMA-RAY FLARES IN THE CRAB NEBULA

International Nuclear Information System (INIS)

Cerutti, Benoît; Uzdensky, Dmitri A.; Begelman, Mitchell C.

2012-01-01

The gamma-ray space telescopes AGILE and Fermi detected short and bright synchrotron gamma-ray flares at photon energies above 100 MeV in the Crab Nebula. This discovery suggests that electron-positron pairs in the nebula are accelerated to PeV energies in a milligauss magnetic field, which is difficult to explain with classical models of particle acceleration and pulsar wind nebulae. We investigate whether particle acceleration in a magnetic reconnection layer can account for the puzzling properties of the flares. We numerically integrate relativistic test-particle orbits in the vicinity of the layer, including the radiation reaction force, and using analytical expressions for the large-scale electromagnetic fields. As they get accelerated by the reconnection electric field, the particles are focused deep inside the current layer where the magnetic field is small. The electrons suffer less from synchrotron losses and are accelerated to extremely high energies. Population studies show that, at the end of the layer, the particle distribution piles up at the maximum energy given by the electric potential drop and is focused into a thin fan beam. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum peaks above 100 MeV and is close to the spectral shape of a single electron. The flare inverse Compton emission is negligible and no detectable emission is expected at other wavelengths. This mechanism provides a plausible explanation for the gamma-ray flares in the Crab Nebula and could be at work in other astrophysical objects such as relativistic jets in active galactic nuclei.

The acceleration of a gaseous plasma by intense microwave fields in a constant inhomogeneous magnetic field

International Nuclear Information System (INIS)

Mourier, Georges

1971-01-01

A gaseous plasma excited by a powerful microwave source (up to 300 kW) was studied theoretically and experimentally. The large amplitude electric field excites, in a constant inhomogeneous magnetic field, a plasma near to the electron cyclotron resonance. These particles are accelerated to energies of between 100 and 10000 eV and subsequently drift to the regions of lower magnetic field. The ions are accelerated by the resulting electrostatic forces. Ion and electron currents of some tens of milli-amperes to a few amperes are obtained. The energy of the electrons is limited by their relativistic mass; a three-dimensional of space charge model is set up to describe the particle flow. (author) [fr

Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

International Nuclear Information System (INIS)

Jing, C.; Konecny, R.; Antipov, S.; Chang, C.; Gold, S. H.; Schoessow, P.; Kanareykin, A.; Gai, W.

2013-01-01

Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications

Applied metrology in the production of superconducting model magnets for particle accelerators

Energy Technology Data Exchange (ETDEWEB)

Ferradas Troitino, Jose [CERN; Bestmann, Patrick [CERN; Bourcey, Nicolas [CERN; Carlon Zurita, Alejandro [CERN; Cavanna, Eugenio [ASG Supercond., Genova; Ferracin, Paolo [CERN; Ferradas Troitino, Salvador [CERN; Holik, Eddie Frank [Fermilab; Izquierdo Bermudez, Susana [CERN; Lackner, Friedrich [CERN; Löffler, Christian [CERN; Maury, Gregory [CERN; Perez, Juan Carlos [CERN; Savary, Frederic [CERN; Semeraro, Michela [CERN; Vallone, Giorgio [CERN

2017-12-22

The production of superconducting magnets for particle accelerators involves high precision assemblies and tight tolerances, in order to achieve the requirements for their appropriate performance. It is therefore essential to have a strict control and traceability over the geometry of each component of the system, and also to be able to compensate possible inherent deviations coming from the production process.

Electromagnetic nonlinearities in a Roebel-cable-based accelerator magnet prototype: variational approach

Science.gov (United States)

Ruuskanen, J.; Stenvall, A.; Lahtinen, V.; Pardo, E.

2017-02-01

Superconducting magnets are the most expensive series of components produced in the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN). When developing such magnets beyond state-of-the-art technology, one possible option is to use high-temperature superconductors (HTS) that are capable of tolerating much higher magnetic fields than low-temperature superconductors (LTS), carrying simultaneously high current densities. Significant cost reductions due to decreased prototype construction needs can be achieved by careful modelling of the magnets. Simulations are used, e.g. for designing magnets fulfilling the field quality requirements of the beampipe, and adequate protection by studying the losses occurring during charging and discharging. We model the hysteresis losses and the magnetic field nonlinearity in the beampipe as a function of the magnet’s current. These simulations rely on the minimum magnetic energy variation principle, with optimization algorithms provided by the open-source optimization library interior point optimizer. We utilize this methodology to investigate a research and development accelerator magnet prototype made of REBCO Roebel cable. The applicability of this approach, when the magnetic field dependence of the superconductor’s critical current density is considered, is discussed. We also scrutinize the influence of the necessary modelling decisions one needs to make with this approach. The results show that different decisions can lead to notably different results, and experiments are required to study the electromagnetic behaviour of such magnets further.

Circular induction accelerator for borehole logging

International Nuclear Information System (INIS)

Chen, F.K.; Bertozzi, W.; Corris, G.W.; Diamond, W.; Doucet, J.A.; Schweitzer, J.S.

1992-01-01

This patent describes a downhole logging sonde adapted to be moved through a borehole, a source of gamma rays in the sonde for irradiating earth formations traversed by the borehole, one or more gamma ray detectors for detecting gamma rays scattered back to the sonde from the irradiated earth formations, and means for transmitting signals representative of the detected gamma rays to the earth's surface for processing. This patent describes improvement in the gamma ray source comprises a magnetic induction particle accelerator, including: a magnetic circuit having a field magnet, generally circular opposed pole pieces, and a core magnet metal ions from the group consisting of Mn, Zn and Ni; an excitation circuit including a field coil surrounding the field magnet and the core magnet and a core coil surrounding the central axially leg of the core magnet; an annular acceleration chamber interposed between the pole pieces; means for applying time-varying acceleration voltage pulses across the primary excitation circuit; means for injecting charged particles into orbit within the acceleration chamber; means for compressing the particle orbits to trap particles within generally circular orbits within the acceleration chamber; means for generating a particle accelerating magnetic flux in the magnetic circuit; and means for ejecting charged particles from the generally circular orbits and into contact with a target to produce gamma ray photons

Acceleration of the charged particles due to chaotic scattering in the combined black hole gravitational field and asymptotically uniform magnetic field

International Nuclear Information System (INIS)

Stuchlik, Zdenek; Kolos, Martin

2016-01-01

To test the role of large-scale magnetic fields in accretion processes, we study the dynamics of the charged test particles in the vicinity of a black hole immersed into an asymptotically uniform magnetic field. Using the Hamiltonian formalism of the charged particle dynamics, we examine chaotic scattering in the effective potential related to the black hole gravitational field combined with the uniform magnetic field. Energy interchange between the translational and oscillatory modes of the charged particle dynamics provides a mechanism for charged particle acceleration along the magnetic field lines. This energy transmutation is an attribute of the chaotic charged particle dynamics in the combined gravitational and magnetic fields only, the black hole rotation is not necessary for such charged particle acceleration. The chaotic scatter can cause a transition to the motion along the magnetic field lines with small radius of the Larmor motion or vanishing Larmor radius, when the speed of the particle translational motion is largest and it can be ultra-relativistic. We discuss the consequences of the model of ionization of test particles forming a neutral accretion disc, or heavy ions following off-equatorial circular orbits, and we explore the fate of heavy charged test particles after ionization where no kick of heavy ions is assumed and only the switch-on effect of the magnetic field is relevant. We demonstrate that acceleration and escape of the ionized particles can be efficient along the Kerr black hole symmetry axis parallel to the magnetic field lines. We show that a strong acceleration of the ionized particles to ultra-relativistic velocities is preferred in the direction close to the magnetic field lines. Therefore, the process of ionization of Keplerian discs around the Kerr black holes can serve as a model of relativistic jets. (orig.)

Acceleration of the charged particles due to chaotic scattering in the combined black hole gravitational field and asymptotically uniform magnetic field

Energy Technology Data Exchange (ETDEWEB)

Stuchlik, Zdenek; Kolos, Martin [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Opava (Czech Republic)

2016-01-15

To test the role of large-scale magnetic fields in accretion processes, we study the dynamics of the charged test particles in the vicinity of a black hole immersed into an asymptotically uniform magnetic field. Using the Hamiltonian formalism of the charged particle dynamics, we examine chaotic scattering in the effective potential related to the black hole gravitational field combined with the uniform magnetic field. Energy interchange between the translational and oscillatory modes of the charged particle dynamics provides a mechanism for charged particle acceleration along the magnetic field lines. This energy transmutation is an attribute of the chaotic charged particle dynamics in the combined gravitational and magnetic fields only, the black hole rotation is not necessary for such charged particle acceleration. The chaotic scatter can cause a transition to the motion along the magnetic field lines with small radius of the Larmor motion or vanishing Larmor radius, when the speed of the particle translational motion is largest and it can be ultra-relativistic. We discuss the consequences of the model of ionization of test particles forming a neutral accretion disc, or heavy ions following off-equatorial circular orbits, and we explore the fate of heavy charged test particles after ionization where no kick of heavy ions is assumed and only the switch-on effect of the magnetic field is relevant. We demonstrate that acceleration and escape of the ionized particles can be efficient along the Kerr black hole symmetry axis parallel to the magnetic field lines. We show that a strong acceleration of the ionized particles to ultra-relativistic velocities is preferred in the direction close to the magnetic field lines. Therefore, the process of ionization of Keplerian discs around the Kerr black holes can serve as a model of relativistic jets. (orig.)

Nb3Sn accelerator magnet technology scale up using cos-theta dipole coils

Energy Technology Data Exchange (ETDEWEB)

Nobrega, F.; Andreev, N.; Ambrosio, G.; Barzi, E.; Bossert, R.; Carcagno, R.; Chlachidze, G.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; /Fermilab

2007-06-01

Fermilab is working on the development of Nb{sub 3}Sn accelerator magnets using shell-type dipole coils and the wind-and-react method. As a part of the first phase of technology development, Fermilab built and tested six 1 m long dipole model magnets and several dipole mirror configurations. The last three dipoles and two mirrors reached their design fields of 10-11 T. The technology scale up phase has started by building 2 m and 4 m dipole coils and testing them in a mirror configuration in which one of the two coils is replaced by a half-cylinder made of low carbon steel. This approach allows for shorter fabrication times and extensive instrumentation preserving almost the same level of magnetic field and Lorentz forces in the coils as in a complete dipole model magnet. This paper presents details on the 2 m (HFDM07) and 4 m long (HFDM08) Nb{sub 3}Sn dipole mirror magnet design and fabrication technology, as well as the magnet test results which are compared with 1 m long models.

Nb3Sn accelerator magnet technology scale up using cos-theta dipole coils

International Nuclear Information System (INIS)

Nobrega, F.; Andreev, N.; Ambrosio, G.; Barzi, E.; Bossert, R.; Carcagno, R.; Chlachidze, G.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Fermilab

2007-01-01

Fermilab is working on the development of Nb 3 Sn accelerator magnets using shell-type dipole coils and the wind-and-react method. As a part of the first phase of technology development, Fermilab built and tested six 1 m long dipole model magnets and several dipole mirror configurations. The last three dipoles and two mirrors reached their design fields of 10-11 T. The technology scale up phase has started by building 2 m and 4 m dipole coils and testing them in a mirror configuration in which one of the two coils is replaced by a half-cylinder made of low carbon steel. This approach allows for shorter fabrication times and extensive instrumentation preserving almost the same level of magnetic field and Lorentz forces in the coils as in a complete dipole model magnet. This paper presents details on the 2 m (HFDM07) and 4 m long (HFDM08) Nb 3 Sn dipole mirror magnet design and fabrication technology, as well as the magnet test results which are compared with 1 m long models

Dealing with post-accelerated electrons in the ITER SINGAP accelerator

International Nuclear Information System (INIS)

Esch, H. de; Hemsworth, R.S.

2006-01-01

Electrons formed by stripping of the negative deuterium beam can be accelerated up to 960 keV in the 1 MeV SINGAP 40 A negative ion accelerator proposed by Europe for the ITER neutral beam injectors. SINGAP accelerates 1280 pre-accelerated 40 keV deuterium beamlets to 1 MeV in a single 350 mm wide gap. At the expected gas pressure of 0.03 Pa inside the accelerator, 2.7 MW of electrons are calculated to leave the accelerator and strike various beamline components, especially the neutraliser. The accelerators of the ITER injectors are designed to produce 4 '' column '' beams which pass through the 4 vertical channels of the neutraliser. Unperturbed the accelerated electrons create small, high power density, 3.3 kW/cm 2 , spots on the leading edges of the neutraliser channels, which is far in excess of their power handling capability. The hot spots arise from the overlapping of beamlets due to the bending induced by the far field of the magnetic filter in the ion source. The proposed solution bends the electrons further downwards, redistributing the power over the neutraliser floor, a vertical electron dump perpendicular to the beam axis located below the neutraliser entrance, and the neutraliser entrance. The bending is to be effected by a magnetic field transverse to the beam direction at the exit of the post-acceleration grid. This field is created by vertical columns of permanent magnets either side of each column beam. After passing between the magnet columns, the electron beams reach the electron dump with a maximum power density of 2.1 kW/cm 2 . The peak power density on the neutraliser entrance is 1.35 kW/cm 2 and on the neutraliser floor 0.82 kW/cm 2 . Electron backscattering would reduce all the numbers by 20%. To further reduce the average power density seen by the beamline components it is proposed to sweep the electron beam in an oscillatory fashion. It is suggested that a failsafe, inexpensive, way is to use a power supply with a ripple of ± 10% to

Biological responses of human solid tumor cells to X-ray irradiation within a 1.5-Tesla magnetic field generated by a magnetic resonance imaging–linear accelerator

NARCIS (Netherlands)

Wang, Li; Hoogcarspel, Stan Jelle; Wen, Zhifei; van Vulpen, Marco; Molkentine, David P.; Kok, Jan; Lin, Steven H.; Broekhuizen, Roel; Ang, Kie Kian; Bovenschen, Niels; Raaymakers, Bas W.; Frank, Steven J.

2016-01-01

Devices that combine magnetic resonance imaging with linear accelerators (MRL) represent a novel tool for MR-guided radiotherapy. However, whether magnetic fields (MFs) generated by these devices affect the radiosensitivity of tumors is unknown. We investigated the influence of a 1.5-T MF on cell

Acceleration of a compact torus

International Nuclear Information System (INIS)

Hartmann, C.W.; Eddleman, J.L.; Hammer, J.H.; Kusse, B.

1987-01-01

The authors report the first results of a study of acceleration of spheromak-type compact toruses in the RACE experiment (plasma Ring ACceleration Experiment). The RACE apparatus consists of (1) a magnetized, coaxial plasma gun 50 cm long, 35 cm OD, 20 cm ID, (2) 600 cm long coaxial acceleration electrodes 50 cm OD, 20 cm ID, (3) a 250 kJ electrolytic capacitor bank to drive the gun solenoid for initial magnetization, (4) a 200 kJ gun bank, (5) a 260 kJ accelerator bank, and (6) magnetic probes and other diagnostics, and vacuum apparatus. To outer acceleration electrode is an extension, at larger OD, of the gun outer electrode, and the inner acceleration electrode is supported and fed by a coaxial insert in the gun center electrode as shown

Magnetic resonance imaging of the cardiovascular system: present state of the art and future potential

International Nuclear Information System (INIS)

Jacobson, H.G.

1988-01-01

State-of-the-art magnetic resonance imaging (MRI) generates high-resolution images of the cardiovascular system. Conventional MRI techniques provide images in six to ten minutes per tomographic slice. New strategies have substantially improved the speed of imaging. The technology is relatively expensive, and its cost-effectiveness remains to be defined in relation to other effective, less expensive, and noninvasive technologies, such as echocardiography and nuclear medicine. The ultimate role of MRI will depend on several factors, including the development of specific applications such as (1) noninvasive angiography, especially of the coronary arteries;(2) noninvasive, high-resolution assessment of regional myocardial blood flow distribution (e.g., using paramagnetic contrast agents); (3) characterization of myocardial diseases using proton-relaxation property changes; and (4) evaluation of in vivo myocardial biochemistry. The three-dimensional imaging capability and the ability to image cardiovascular structures without contrast material give MRI a potential advantage over existing noninvasive diagnostic imaging techniques. This report analyzes current applications of MRI to the cardiovascular system and speculates on their future

Study of the implementation of high temperature superconductors to accelerator magnets

International Nuclear Information System (INIS)

Fleiter, Jerome

2013-01-01

Particle colliders are the main tool for investigating and understanding the fundamental laws of physics. The CERN Large Hadron Collider (LHC), is a circular accelerator which steers and collides two counter-rotating protons beams. It has four collision points where detectors are placed to analyze the products emerging from the collisions. In a synchrotron machine a magnetic flux density is used to guide and focus particles around the orbit. The maximum energy that a circular machine with a given geometry can achieve is limited by the maximum strength of the dipole magnetic flux density. There is therefore an interest in the particle physics community in searching for dipole magnets with higher strength. The LHC has a beam trajectory radius of 4.3 km and a collision center-of-mass energy of 14 TeV. The accelerator employs 1232 large superconducting Nb-Ti dipole magnets operated at a flux density of up to 8.3 T in a bath of superfluid helium at 1.9 K. Energies higher than that achieved with the LHC require magnets made from superconductors with higher upper critical flux density. Nb 3 Sn is an option for magnets operated up to about 14 T. The level of energies of the type being discussed for a potential energy upgrade of the LHC machine - 33 TeV- would require the use of high temperature superconductors (HTS). Three technical HTS are available today: YBCO, Bi-2212 and Bi-2223. At low temperature YBCO conductors present both irreversible flux density and current density in excess of those measured in Bi-2212 and Bi-2223 conductors. In addition, YBCO can be used as reacted conductor, which makes its use for applications simpler than Bi-2212, which requires heat treatment at high temperature and in oxygen atmosphere after cabling and winding. The level of currents required for application to accelerator magnets, which is above 10 kA at the nominal operating temperature and flux density, excludes the use of single strands. The high current and high current density

Amine functionalized magnetic nanoparticles for removal of oil droplets from produced water and accelerated magnetic separation

Energy Technology Data Exchange (ETDEWEB)

Ko, Saebom, E-mail: saebomko@austin.utexas.edu [University of Texas, Department of Petroleum and Geosystems Engineering (United States); Kim, Eun Song [University of Texas, Department of Biomedical Engineering (United States); Park, Siman [University of Texas, Department of Civil, Architectural and Environmental Engineering (United States); Daigle, Hugh [University of Texas, Department of Petroleum and Geosystems Engineering (United States); Milner, Thomas E. [University of Texas, Department of Biomedical Engineering (United States); Huh, Chun [University of Texas, Department of Petroleum and Geosystems Engineering (United States); Bennetzen, Martin V. [Maersk Oil Corporate (Denmark); Geremia, Giuliano A. [Maersk Oil Research and Technology Centre (Qatar)

2017-04-15

Magnetic nanoparticles (MNPs) with surface coatings designed for water treatment, in particular for targeted removal of contaminants from produced water in oil fields, have drawn considerable attention due to their environmental merit. The goal of this study was to develop an efficient method of removing very stable, micron-scale oil droplets dispersed in oilfield produced water. We synthesized MNPs in the laboratory with a prescribed surface coating. The MNPs were superparamagnetic magnetite, and the hydrodynamic size of amine functionalized MNPs ranges from 21 to 255 nm with an average size of 66 nm. The initial oil content of 0.25 wt.% was reduced by as much as 99.9% in separated water. The electrostatic attraction between negatively charged oil-in-water emulsions and positively charged MNPs controls, the attachment of MNPs to the droplet surface, and the subsequent aggregation of the electrically neutral oil droplets with attached MNPs (MNPs-oils) play a critical role in accelerated and efficient magnetic separation. The total magnetic separation time was dramatically reduced to as short as 1 s after MNPs, and oil droplets were mixed, in contrast with the case of free, individual MNPs with which separation took about 36∼72 h, depending on the MNP concentrations. Model calculations of magnetic separation velocity, accounting for the MNP magnetization and viscous drag, show that the total magnetic separation time will be approximately 5 min or less, when the size of the MNPs-oils is greater than 360 nm, which can be used as an optimum operating condition.

Superconducting Magnets

CERN Multimedia

CERN. Geneva

2008-01-01

Starting from the beam requirements for accelerator magnets, we will outline the main issues and the physical limitations for producing strong and pure magnetic fields with superconductors. The seminar will mainly focus on the magnets for the accelerator, and give some hints on the magnets for the experiments. Prerequisite knowledge: Basic knowledge of Maxwell equations, and linear optics for particle accelerators (FODO cell, beta functions).

Superconductivity in high energy particle accelerators

International Nuclear Information System (INIS)

Schmueser, P.

2002-08-01

The basics of superconductivity are outlined with special emphasis on the features which are relevant for the application in magnets and radio frequency cavities for high energy particle accelerators. The special properties of superconducting accelerator magnets are described in detail: design principles, magnetic field calculations, magnetic forces, quench performance, persistent magnetization currents and eddy currents. The design principles and basic properties of superconducting cavities are explained as well as the observed performance limitations and the countermeasures. The ongoing research efforts towards maximum accelerating fields are addressed and the coupling of radio frequency power to the particle beam is treated. (orig.)

Fluorine cardiovascular magnetic resonance angiography in vivo at 1.5 T with perfluorocarbon nanoparticle contrast agents.

Science.gov (United States)

Neubauer, Anne M; Caruthers, Shelton D; Hockett, Franklin D; Cyrus, Tillman; Robertson, J David; Allen, J Stacy; Williams, Todd D; Fuhrhop, Ralph W; Lanza, Gregory M; Wickline, Samuel A

2007-01-01

While the current gold standard for coronary imaging is X-ray angiography, evidence is accumulating that it may not be the most sensitive technique for detecting unstable plaque. Other imaging modalities, such as cardiovascular magnetic resonance (CMR), can be used for plaque characterization, but suffer from long scan and reconstruction times for determining regions of stenosis. We have developed an intravascular fluorinated contrast agent that can be used for angiography with cardiovascular magnetic resosnace at clinical field strengths (1.5 T). This liquid perfluorocarbon nanoparticle contains a high concentration of fluorine atoms that can be used to generate contrast on 19F MR images without any competing background signal from surrounding tissues. By using a perfluorocarbon with 20 equivalent fluorine molecules, custom-built RF coils, a modified clinical scanner, and an efficient steady-state free procession sequence, we demonstrate the use of this agent for angiography of small vessels in vitro, ex vivo, and in vivo. The surprisingly high signal generated with very short scan times and low doses of perfluorocarbon indicates that this technique may be useful in clinical settings when coupled with advanced imaging strategies.

Final Report: MATERIALS, STRANDS, AND CABLES FOR SUPERCONDUCTING ACCELERATOR MAGNETS [Grant Number DE-SC0010312

Energy Technology Data Exchange (ETDEWEB)

Sumption, Mike D. [The Ohio State Univ., Columbus, OH (United States). Center for Superconducting and Magnetic Materials (CSMM); Collings, Edward W. [The Ohio State Univ., Columbus, OH (United States). Center for Superconducting and Magnetic Materials (CSMM)

2014-10-29

Our program consisted of the two components: Strand Research and Cable Research, with a focus on Nb3Sn, Bi2212, and YBCO for accelerator magnet applications. We demonstrated a method to refine the grains in Nb3Sn by a factor of two, reaching 45 nm grain sizes, and layer Jcs of 6 kA/mm2 at 12 T. W also measured conductor magnetization for field quality. This has been done both with Nb3Sn conductor, as well as Bi:2212 strand. Work in support of quench studies of YBCO coils was also performed. Cable loss studies in Nb3Sn focused on connecting and comparing persistent magnetization and coupling magnetization for considering their relative impact on HEP machines. In the area of HTS cables, we have investigated both the quench in multistrand YBCO CORC cables, as well as the magnetization of these cables for use in high field magnets. In addition, we examined the magnetic and thermal properties of large (50 T) solenoids.

Predictors of ischaemic mitral regurgitation recurrence in patients undergoing combined surgery: additional value of cardiovascular magnetic resonance imaging.

Science.gov (United States)

Glaveckaite, Sigita; Uzdavinyte-Gateliene, Egle; Petrulioniene, Zaneta; Palionis, Darius; Valeviciene, Nomeda; Kalinauskas, Gintaras; Serpytis, Pranas; Laucevicius, Aleksandras

2018-03-09

We aimed to evaluate (i) the effectiveness of combined surgery (coronary artery bypass grafting with restrictive mitral valve annuloplasty) and (ii) the late gadolinium enhancement cardiovascular magnetic resonance-based predictors of ischaemic mitral regurgitation (IMR) recurrence. The prospective analysis included 40 patients with multivessel coronary artery disease, IMR >II° and left ventricular (LV) dysfunction undergoing combined surgery. The degree of IMR and LV parameters were assessed preoperatively by transthoracic echocardiography, 3D transoesophageal echocardiography and cardiovascular magnetic resonance and postoperatively by transthoracic echocardiography. The effective mitral valve repair group (n = 30) was defined as having recurrent ischaemic mitral regurgitation (RIMR) ≤II° at the end of follow-up (25 ± 11 months). The surgery was effective: freedom from RIMR >II° at 1 and 2 years after surgery was 80% and 75%, respectively. Using multivariable logistic regression, 2 independent predictors of RIMR >II° were identified: ≥3 non-viable LV segments (odds ratio 22, P = 0.027) and ≥1 non-viable segment in the LV posterior wall (odds ratio 11, P = 0.026). Using classification trees, the best combinations of cardiovascular magnetic resonance-based and 3D transoesophageal echocardiography-based predictors for RIMR >II° were (i) posterior mitral valve leaflet angle >40° and LV end-systolic volume index >45 ml/m2 (sensitivity 100%, specificity 89%) and (ii) scar transmurality >68% in the inferior LV wall and EuroSCORE II >8 (sensitivity 83%, specificity 78%). There is a clear relationship between the amount of non-viable LV segments, especially in the LV posterior and inferior walls, and the recurrence of IMR after the combined surgery.

Rarefaction acceleration in magnetized gamma-ray burst jets

Science.gov (United States)

Sapountzis, Konstantinos; Vlahakis, Nektarios

2013-09-01

Relativistic jets associated with long/soft gamma-ray bursts are formed and initially propagate in the interior of the progenitor star. Because of the subsequent loss of their external pressure support after they cross the stellar surface, these flows can be modelled as moving around a corner. A strong steady-state rarefaction wave is formed, and the sideways expansion is accompanied by a rarefaction acceleration. We investigate the efficiency and the general characteristics of this mechanism by integrating the steady-state, special relativistic, magnetohydrodynamic equations, using a special set of partial exact solutions in planar geometry (r self-similar with respect to the `corner'). We also derive analytical approximate scalings in the ultrarelativistic cold/magnetized, and hydrodynamic limits. The mechanism is more effective in magnetized than in purely hydrodynamic flows. It substantially increases the Lorentz factor without much affecting the opening of the jet; the resulting values of their product can be much greater than unity, allowing for possible breaks in the afterglow light curves. These findings are similar to the ones from numerical simulations of axisymmetric jets by Komissarov et al. and Tchekhovskoy et al., although in our approach we describe the rarefaction as a steady-state simple wave and self-consistently calculate the opening of the jet that corresponds to zero external pressure.

Automated installations for reeling up of superconducting magnet windings of the accelerating-storage complex

International Nuclear Information System (INIS)

Dolzhenkov, V.I.; Elistratov, V.V.; Kuznetsov, Yu.V.; Petrov, V.B.; Popov, V.V.; Savel'ev, A.V.; Sokolov, B.V.; Sytnik, V.V.; Tarakanov, N.M.; Ustinov, E.A.

1992-01-01

An automated facility for reeling up the windings of model and full-scale superconducting magnets of the accelerating-storage complex is described. The control system monitors superconducting cable tension, transport carriage linear velocity and some other parameters. Maximum length of the winded coils is 6 m. Cable tension stability - 5%

Design, simulation and construction of quadrupole magnets for focusing electron beam in powerful industrial electron accelerator

Directory of Open Access Journals (Sweden)

S KH Mousavi

2015-09-01

Full Text Available In this paper the design and simulation of quadrupole magnets and electron beam optical of that by CST Studio code has been studied. Based on simulation result the magnetic quadrupole has been done for using in beam line of first Iranian powerful electron accelerator. For making the suitable magnetic field the effects of material and core geometry and coils current variation on quadrupole magnetic field have been studied. For test of quadrupole magnet the 10 MeV beam energy and 0.5 pi mm mrad emittance of input beam has been considered. We see the electron beam through the quadrupole magnet focus in one side and defocus in other side. The optimum of distance between two quadrupole magnets for low emittance have been achieved. The simulation results have good agreement with experimental results

Optimization of accelerator control

International Nuclear Information System (INIS)

Vasiljev, N.D.; Mozin, I.V.; Shelekhov, V.A.; Efremov, D.V.

1992-01-01

Expensive exploitation of charged particle accelerators is inevitably concerned with requirements of effectively obtaining of the best characteristics of accelerated beams for physical experiments. One of these characteristics is intensity. Increase of intensity is hindered by a number of effects, concerned with the influence of the volume charge field on a particle motion dynamics in accelerator's chamber. However, ultimate intensity, determined by a volume charge, is almost not achieved for the most of the operating accelerators. This fact is caused by losses of particles during injection, at the initial stage of acceleration and during extraction. These losses are caused by deviations the optimal from real characteristics of the accelerating and magnetic system. This is due to a number of circumstances, including technological tolerances on structural elements of systems, influence of measuring and auxiliary equipment and beam consumers' installations, placed in the closed proximity to magnets, and instability in operation of technological systems of accelerator. Control task consists in compensation of deviations of characteristics of magnetic and electric fields by optimal selection of control actions. As for technical means, automatization of modern accelerators allows to solve optimal control problems in real time. Therefore, the report is devoted to optimal control methods and experimental results. (J.P.N.)

Cannabis exposure as an interactive cardiovascular risk factor and accelerant of organismal ageing: a longitudinal study.

Science.gov (United States)

Reece, Albert Stuart; Norman, Amanda; Hulse, Gary Kenneth

2016-11-07

Many reports exist of the cardiovascular toxicity of smoked cannabis but none of arterial stiffness measures or vascular age (VA). In view of its diverse toxicology, the possibility that cannabis-exposed patients may be ageing more quickly requires investigation. Cross-sectional and longitudinal, observational. Prospective. Single primary care addiction clinic in Brisbane, Australia. 11 cannabis-only smokers, 504 tobacco-only smokers, 114 tobacco and cannabis smokers and 534 non-smokers. known cardiovascular disease or therapy or acute exposure to alcohol, amphetamine, heroin or methadone. Radial arterial pulse wave tonometry (AtCor, SphygmoCor, Sydney) performed opportunistically and sequentially on patients between 2006 and 2011. Algorithmically calculated VA. other central haemodynamic variables. Differences between group chronological ages (CA, 30.47±0.48 to 40.36±2.44, mean±SEM) were controlled with linear regression. Between-group sex differences were controlled by single-sex analysis. Mean cannabis exposure among patients was 37.67±7.16 g-years. In regression models controlling for CA, Body Mass Index (BMI), time and inhalant group, the effect of cannabis use on VA was significant in males (p=0.0156) and females (p=0.0084). The effect size in males was 11.84%. A dose-response relationship was demonstrated with lifetime exposure (pcannabis was robust to adjustment and was unrelated to its acute effects. Significant power interactions between cannabis exposure and the square and cube of CA were demonstrated (from pCannabis is an interactive cardiovascular risk factor (additional to tobacco and opioids), shows a prominent dose-response effect and is robust to adjustment. Cannabis use is associated with an acceleration of the cardiovascular age, which is a powerful surrogate for the organismal-biological age. This likely underlies and bi-directionally interacts with its diverse toxicological profile and is of considerable public health and regulatory

Cardiovascular fluid dynamics. Methods for flow and pressure field analysis from magnetic resonance imaging

International Nuclear Information System (INIS)

Ebbers, T.

2001-01-01

Cardiovascular blood flow is highly complex and incompletely understood. Blood flow patterns are expected to influence the opening and closing of normal and prosthetic heart valves, the efficiency of cardiac filling and ejection, and the resistance to thrombus formation within the heart. Conventional diagnostic techniques are poorly suited to the study of the three-dimensional (3D) blood flow patterns in the heart chambers and large vessels. Noninvasive methods have also been inadequate in studying intracardiac pressure differences, which are the driving force of flow and are critical in the evaluation of many cardiovascular abnormalities. This thesis focuses on the development of non-invasive methods for analysis of 3D cardiovascular blood flow. Simultaneous study of cardiovascular fluid dynamics allowed knowledge exchange across the two disciplines, facilitating the development process and broadening the applicability of the methods. A time-resolved 3D phase-contrast Magnetic Resonance Imaging (MRI) technique was used to acquire the velocity vector field in a 3D volume encompassing the entire heart or a large vessel. Cardiovascular blood flow patterns were visualized by use of particle traces, which revealed, for instance, vortical flow patterns in the left atrium. By applying the Navier-Stokes equation along a user-defined line in the 3D velocity vector field, the relative pressure could be obtained as an excellent supplement to the flow pattern visualization. Using a delineation of the blood pool, the time-varying 3D relative pressure field in the human left ventricle was obtained from the velocity field by use of the pressure Poisson equation. A delineation of the heart muscle, a task that is almost impossible to perform on 3D MRI either automatically or manually, was also achieved by usage of particle traces. This segmentation allows automatic calculation of the 3D relative pressure field, as well as calculation of well-established parameters such as

Cardiovascular fluid dynamics. Methods for flow and pressure field analysis from magnetic resonance imaging

Energy Technology Data Exchange (ETDEWEB)

Ebbers, T

2001-05-01

Cardiovascular blood flow is highly complex and incompletely understood. Blood flow patterns are expected to influence the opening and closing of normal and prosthetic heart valves, the efficiency of cardiac filling and ejection, and the resistance to thrombus formation within the heart. Conventional diagnostic techniques are poorly suited to the study of the three-dimensional (3D) blood flow patterns in the heart chambers and large vessels. Noninvasive methods have also been inadequate in studying intracardiac pressure differences, which are the driving force of flow and are critical in the evaluation of many cardiovascular abnormalities. This thesis focuses on the development of non-invasive methods for analysis of 3D cardiovascular blood flow. Simultaneous study of cardiovascular fluid dynamics allowed knowledge exchange across the two disciplines, facilitating the development process and broadening the applicability of the methods. A time-resolved 3D phase-contrast Magnetic Resonance Imaging (MRI) technique was used to acquire the velocity vector field in a 3D volume encompassing the entire heart or a large vessel. Cardiovascular blood flow patterns were visualized by use of particle traces, which revealed, for instance, vortical flow patterns in the left atrium. By applying the Navier-Stokes equation along a user-defined line in the 3D velocity vector field, the relative pressure could be obtained as an excellent supplement to the flow pattern visualization. Using a delineation of the blood pool, the time-varying 3D relative pressure field in the human left ventricle was obtained from the velocity field by use of the pressure Poisson equation. A delineation of the heart muscle, a task that is almost impossible to perform on 3D MRI either automatically or manually, was also achieved by usage of particle traces. This segmentation allows automatic calculation of the 3D relative pressure field, as well as calculation of well-established parameters such as

Whole body cardiovascular magnetic resonance imaging to stratify symptomatic and asymptomatic atherosclerotic burden in patients with isolated cardiovascular disease

International Nuclear Information System (INIS)

Weir-McCall, Jonathan R.; Duce, Suzanne L.; Gandy, Stephen J.; Matthew, Shona Z.; Martin, Patricia; Cassidy, Deirdre B.; McCormick, Lynne; Belch, Jill J. F.; Struthers, Allan D.; Colhoun, Helen M.; Houston, J. Graeme

2016-01-01

The aim of this study was to use whole body cardiovascular magnetic resonance imaging (WB CVMR) to assess the heart and arterial network in a single examination, so as to describe the burden of atherosclerosis and subclinical disease in participants with symptomatic single site vascular disease. 64 patients with a history of symptomatic single site vascular disease (38 coronary artery disease (CAD), 9 cerebrovascular disease, 17 peripheral arterial disease (PAD)) underwent whole body angiogram and cardiac MR in a 3 T scanner. The arterial tree was subdivided into 31 segments and each scored according to the degree of stenosis. From this a standardised atheroma score (SAS) was calculated. Cine and late gadolinium enhancement images of the left ventricle were obtained. Asymptomatic atherosclerotic disease with greater than 50 % stenosis in arteries other than that responsible for their presenting complain was detected in 37 % of CAD, 33 % of cerebrovascular and 47 % of PAD patients. Unrecognised myocardial infarcts were observed in 29 % of PAD patients. SAS was significantly higher in PAD patients 24 (17.5-30.5) compared to CAD 4 (2–11.25) or cerebrovascular disease patients 6 (2-10) (ANCOVA p < 0.001). Standardised atheroma score positively correlated with age (β 0.36 p = 0.002), smoking status (β 0.34 p = 0.002), and LV mass (β -0.61 p = 0.001) on multiple linear regression. WB CVMR is an effective method for the stratification of cardiovascular disease. The high prevalence of asymptomatic arterial disease, and silent myocardial infarctions, particularly in the peripheral arterial disease group, demonstrates the importance of a systematic approach to the assessment of cardiovascular disease

A new 3-D integral code for computation of accelerator magnets

International Nuclear Information System (INIS)

Turner, L.R.; Kettunen, L.

1991-01-01

For computing accelerator magnets, integral codes have several advantages over finite element codes; far-field boundaries are treated automatically, and computed field in the bore region satisfy Maxwell's equations exactly. A new integral code employing edge elements rather than nodal elements has overcome the difficulties associated with earlier integral codes. By the use of field integrals (potential differences) as solution variables, the number of unknowns is reduced to one less than the number of nodes. Two examples, a hollow iron sphere and the dipole magnet of Advanced Photon Source injector synchrotron, show the capability of the code. The CPU time requirements are comparable to those of three-dimensional (3-D) finite-element codes. Experiments show that in practice it can realize much of the potential CPU time saving that parallel processing makes possible. 8 refs., 4 figs., 1 tab

Comparison Study of Electromagnet and Permanent Magnet Systems for an Accelerator Using Cost-Based Failure Modes and Effects Analysis

International Nuclear Information System (INIS)

Spencer, C

2004-01-01

The next generation of particle accelerators will be one-of-a-kind facilities, and to meet their luminosity goals they must have guaranteed availability over their several decade lifetimes. The Next Linear Collider (NLC) is one viable option for a 1 TeV electron-positron linear collider, it has an 85% overall availability goal. We previously showed how a traditional Failure Modes and Effects Analysis (FMEA) of a SLAC electromagnet leads to reliability-enhancing design changes. Traditional FMEA identifies failure modes with high risk but does not consider the consequences in terms of cost, which could lead to unnecessarily expensive components. We have used a new methodology, ''Life Cost-Based FMEA'', which measures risk of failure in terms of cost, in order to evaluate and compare two different technologies that might be used for the 8653 NLC magnets: electromagnets or permanent magnets. The availabilities for the two different types of magnet systems have been estimated using empirical data from SLAC's accelerator failure database plus expert opinion on permanent magnet failure modes and industry standard failure data. Labor and material costs to repair magnet failures are predicted using a Monte Carlo simulation of all possible magnet failures over a 30-year lifetime. Our goal is to maximize up-time of the NLC through magnet design improvements and the optimal combination of electromagnets and permanent magnets, while reducing magnet system lifecycle costs

Quasi-adiabatic particle acceleration in a magnetic field reversals and the formation of the plasma sheet boundary layer in the earth's magnetotail

International Nuclear Information System (INIS)

Zelenyi, L.M.; Vogin, D.V.; Buechner, J.

1989-01-01

Two types of regularity exist for the particle motion in the two-dimensional magnetic field reversals (MFR) with the strongly curves magnetic field lines - the usual adiabatic and another one which we called 'quasiadiabatic'. Here we consider the acceleration of MFR particles in stationary and homogeneous electric field induced by the motion of MFR through the ambient plasma (i.e. solar wind). Assuming that the time scale of acceleration is slow in comparison with the period of orbital motion we introduce the new longitudinal invariant I κ . This enables to describe the process of acceleration in a closed form and to obtain for the first time the laws governing the quasiadiabatic ion acceleration in the Earth's mangetotail. The similarities and differences in adiabatic and quasiadiabatic acceleration mechanisms are discussed. The obtained results give and important insights to the problem of the particle heating in hte Earth's magnetotail and to the formation of accelerated plasma streams along the edges of the plasma sheet. (author). 17 refs.; 7 figs

Experience with the procurement of ferrite and temperature compensator for permanent magnets for accelerators

International Nuclear Information System (INIS)

Fowler, W.B.; Brown, B.C.; Volk, J.

1997-07-01

The use of permanent magnets for transporting the 8 GeV proton beam from the Fermilab Booster to the new Fermilab Main Injector accelerator has been implemented and the magnets for a new 8 GeV ring to be installed in the Main Injector tunnel for increasing the luminosity of pbar/p collisions in the Tevatron are about to start being produced. Strontium oxide ferrite was selected for the magnets due to it's low cost and satisfactory magnetic properties for the 1.5 kilogauss fields required in the 2-inch gap magnets. Fermilab has received 96,000 pounds of ferrite and by working with the Vendor (HITACHI, Edmore, MI) improved uniformity of Residual Induction (Br) has reached 3905 gauss ± 0.65%. Further details are given in the paper. Overcoming the magnetic field variation when the temperature of the magnets changes is accomplished by incorporation of approximately 30% nickel steel alloy. The ferrite changes approximately -0.2% per degree C, which is compensated for by the 13% by the volume of compensator alloy incorporated in the magnet. Fourteen thousand (14,000) pounds of this material has been received and in order to obtain sufficient uniformity the authors mixed equal amounts from each batch into each magnet. Results of this process are given in the paper

Analysis of Uncertainties in Protection Heater Delay Time Measurements and Simulations in Nb$_{3}$Sn High-Field Accelerator Magnets

CERN Document Server

Salmi, Tiina; Marchevsky, Maxim; Bajas, Hugo; Felice, Helene; Stenvall, Antti

2015-01-01

The quench protection of superconducting high-field accelerator magnets is presently based on protection heaters, which are activated upon quench detection to accelerate the quench propagation within the winding. Estimations of the heater delay to initiate a normal zone in the coil are essential for the protection design. During the development of Nb3Sn magnets for the LHC luminosity upgrade, protection heater delays have been measured in several experiments, and a new computational tool CoHDA (Code for Heater Delay Analysis) has been developed for heater design. Several computational quench analyses suggest that the efficiency of the present heater technology is on the borderline of protecting the magnets. Quantifying the inevitable uncertainties related to the measured and simulated delays is therefore of pivotal importance. In this paper, we analyze the uncertainties in the heater delay measurements and simulations using data from five impregnated high-field Nb3Sn magnets with different heater geometries. ...

Analysis of Uncertainties in Protection Heater Delay Time Measurements and Simulations in Nb$_{3}$Sn High-Field Accelerator Magnets

CERN Document Server

Salmi, Tiina; Marchevsky, Maxim; Bajas, Hugo; Felice, Helene; Stenvall, Antti

2015-01-01

The quench protection of superconducting high-field accelerator magnets is presently based on protection heaters, which are activated upon quench detection to accelerate the quench propagation within the winding. Estimations of the heater delay to initiate a normal zone in the coil are essential for the protection design. During the development of Nb$_{3}$Sn magnets for the LHC luminosity upgrade, protection heater delays have been measured in several experiments, and a new computational tool CoHDA (Code for Heater Delay Analysis) has been developed for heater design. Several computational quench analyses suggest that the efficiency of the present heater technology is on the borderline of protecting the magnets. Quantifying the inevitable uncertainties related to the measured and simulated delays is therefore of pivotal importance. In this paper, we analyze the uncertainties in the heater delay measurements and simulations using data from five impregnated high-field Nb$_{3}$Sn magnets with different heater ge...

Electron Acceleration by Cascading Reconnection in the Solar Corona. I. Magnetic Gradient and Curvature Drift Effects

Czech Academy of Sciences Publication Activity Database

Zhou, X.; Büchner, J.; Bárta, Miroslav; Gan, W.; Liu, S.

2015-01-01

Roč. 815, č. 1 (2015), 6/1-6/17 ISSN 0004-637X Institutional support: RVO:67985815 Keywords : acceleration of particles * magnetic reconnection * magnetohydrodynamics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.909, year: 2015

submitter On Roebel Cable Geometry for Accelerator Magnet

CERN Document Server

Fleiter, J; Ballarino, A

2016-01-01

Roebel-type cables made of a ReBCO conductor are potential candidates for high-field accelerator magnets. The necessity to promote a large effective transverse section in a Roebel cable to avoid local overstress leading to degradation in electrical performance has been recently addressed. In this paper, a new geometry of meander tapes for a Roebel cable that enhances both the transverse effective section and the current margin at crossing segments is discussed. As Roebel cables are bent at the coil ends, the modulation of the bending radius of strands along the cable pitch leads to a shift of the strands with respect to each other. The shift magnitude is analytically investigated in this paper as a function of both cable features and coil geometry. Finally, the minimum transposition pitch of Roebel cables is determined on the basis of coil characteristics.

Cardiovascular risk in women with polycystic ovary syndrome.

Science.gov (United States)

Cho, L W; Atkin, S L

2007-12-01

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women that has received an immense amount of attention in the recent years due to the possible associated risk of cardiovascular disease. Women with PCOS demonstrate an adverse cardiovascular profile characteristic of the cardiometabolic syndrome and an established risk of progression to type 2 diabetes. Despite the presence of cardiovascular risk factors and increased surrogate markers of cardiovascular disease, it is unclear if they develop accelerated atherosclerosis. This article summarized the recent development and findings of cardiovascular risk in women with PCOS, and finally the therapeutic options will be discussed.

Standard map in magnetized relativistic systems: fixed points and regular acceleration.

Science.gov (United States)

de Sousa, M C; Steffens, F M; Pakter, R; Rizzato, F B

2010-08-01

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlike the traditional form of the standard map, the present map is nonlinear in the wave amplitude and displays a series of peculiar properties. Among these properties we discuss the relation involving fixed points of the maps and accelerator regimes.

Cost Based Failure Modes and Effects Analysis (FMEA) for Systems of Accelerator Magnets

International Nuclear Information System (INIS)

Spencer, Cherrill M

2003-01-01

The proposed Next Linear Collider (NLC) has a proposed 85% overall availability goal, the availability specifications for all its 7200 magnets and their 6167 power supplies are 97.5% each. Thus all of the electromagnets and their power supplies must be highly reliable or quickly repairable. Improved reliability or repairability comes at a higher cost. We have developed a set of analysis procedures for magnet designers to use as they decide how much effort to exert, i.e. how much money to spend, to improve the reliability of a particular style of magnet. We show these procedures being applied to a standard SLAC electromagnet design in order to make it reliable enough to meet the NLC availability specs. First, empirical data from SLAC's accelerator failure database plus design experience are used to calculate MTBF for failure modes identified through a FMEA. Availability for one particular magnet can be calculated. Next, labor and material costs to repair magnet failures are used in a Monte Carlo simulation to calculate the total cost of all failures over a 30-year lifetime. Opportunity costs are included. Engineers choose from amongst various designs by comparing lifecycle costs

Accounting for the fringe magnetic field from the bending magnet in a Monte Carlo accelerator treatment head simulation.

Science.gov (United States)

O'Shea, Tuathan P; Foley, Mark J; Faddegon, Bruce A

2011-06-01

Monte Carlo (MC) simulation can be used for accurate electron beam treatment planning and modeling. Measurement of large electron fields, with the applicator removed and secondary collimator wide open, has been shown to provide accurate simulation parameters, including asymmetry in the measured dose, for the full range of clinical field sizes and patient positions. Recently, disassembly of the treatment head of a linear accelerator has been used to refine the simulation of the electron beam, setting tightly measured constraints on source and geometry parameters used in simulation. The simulation did not explicitly include the known deflection of the electron beam by a fringe magnetic field from the bending magnet, which extended into the treatment head. Instead, the secondary scattering foil and monitor chamber were unrealistically laterally offset to account for the beam deflection. This work is focused on accounting for this fringe magnetic field in treatment head simulation. The magnetic field below the exit window of a Siemens Oncor linear accelerator was measured with a Tesla-meter from 0 to 12 cm from the exit window and 1-3 cm off-axis. Treatment head simulation was performed with the EGSnrc/BEAMnrc code, modified to incorporate the effect of the magnetic field on charged particle transport. Simulations were used to analyze the sensitivity of dose profiles to various sources of asymmetry in the treatment head. This included the lateral spot offset and beam angle at the exit window, the fringe magnetic field and independent lateral offsets of the secondary scattering foil and electron monitor chamber. Simulation parameters were selected within the limits imposed by measurement uncertainties. Calculated dose distributions were then compared with those measured in water. The magnetic field was a maximum at the exit window, increasing from 0.006 T at 6 MeV to 0.020 T at 21 MeV and dropping to approximately 5% of the maximum at the secondary scattering foil. It

Obtaining the intrinsic electron spectrum of linear accelerators using the relation between the current of the bending magnet and the absorbed dose in water

International Nuclear Information System (INIS)

Vega, Jose M. de la; Guirado, Damian; Vilches, Manuel; Perdices, Jose I.; Lallena, Antonio M.

2008-01-01

Purpose. To present a novel methodology to model the intrinsic electron spectra of a linear accelerator and its situation with respect to the energy window. Methods. The spectra are obtained by fitting the variation of R 50 and the maximum dose rate measured in a water phantom with the bending magnet current. The obtained spectra are verified with a realistic Monte Carlo simulation of the accelerator. Results. The intrinsic spectra and their relative position with respect to the energy window of the bending magnet have been obtained for a Siemens Mevatron KDS and an ELEKTA SL20 accelerators. Conclusions. Using this method in the commissioning and scheduled revisions of the accelerator, the tuning of the current of the bending magnet could be done in such a way that both the quality of the beam and the dose rate would reach a better long-term stability

theoretical and experimental study of plasma acceleration by means of R.F. and static magnetic field gradient

International Nuclear Information System (INIS)

Bardet, Rene; Consoli, Terenzio; Geller, Richard

1964-09-01

In the first part of the paper, the theory of the physical mechanism of ion dragging by accelerated electrons due to the superimposition of the gradient of a electromagnetic field and the gradient of a static magnetic field, is described. The resulting trajectory of the electrons is a helicoid and one shows the variations of the diameter and the path of the spirals along the axis as a function of the difference between the gyrofrequency and the applied R.F. frequency. The ion acceleration is due to an electron space charge effect. The grouping of the equations of the electronic and ionic fluid motions leads to the introduction of a tensor mass: along the x and y direction the transverse motion of the fluid is controlled by the relativistic mass of electrons whereas along the z direction the axial motion is determined by the ionic mass. Then we deduce physical consequences of the theoretical study and give three experimental evidences. The second part of the paper is devoted to the experimental device called Pleiade which allowed us to verify some of the theoretical predictions. Pleiade produces a D.C. operating plasma beam in which the electrons exhibit radially oriented energies whereas the ionic energy is mainly axial. The experimental results indicate that the energy of the particles is in the keV range. In the third part we deal with the reflecting properties of the device. We show that the R.F. static magnetic field gradients are not only capable of accelerating a Plasma beam along the axially decreasing magnetic field, but are also capable of stopping and reflecting such a beam when the latter is moving along an axially increasing magnetic field. We describe finally a plasma accumulation experiment in which two symmetric structures form simultaneously an accelerator and a 'dynamic mirror' for the particles. Evidence of accumulation is given. (authors) [fr

Generation of magnetic fields for accelerators with permanent magnets

International Nuclear Information System (INIS)

Meinander, T.

1994-01-01

Commercially available permanent magnet materials and their properties are reviewed. Advantages and disadvantages of using permanent magnets as compared to electromagnets for the generation of specific magnetic fields are discussed. Basic permanent magnet configurations in multipole magnets and insertion devices are presented. (orig.)

FFAGS for muon acceleration

International Nuclear Information System (INIS)

Berg, J. Scott; Kahn, Stephen; Palmer, Robert; Trbojevic, Dejan; Johnstone, Carol; Keil, Eberhard; Aiba, Masamitsu; Machida, Shinji; Mori, Yoshiharu; Ogitsu, Toru; Ohmori, Chihiro; Sessler, Andrew; Koscielniak, Shane

2003-01-01

Due to their finite lifetime, muons must be accelerated very rapidly. It is challenging to make the magnets ramp fast enough to accelerate in a synchrotron, and accelerating in a linac is very expensive. One can use a recirculating accelerator (like CEBAF), but one needs a different arc for each turn, and this limits the number of turns one can use to accelerate, and therefore requires significant amounts of RF to achieve the desired energy gain. An alternative method for muon acceleration is using a fixed field alternating gradient (FFAG) accelerator. Such an accelerator has a very large energy acceptance (a factor of two or three), allowing one to use the same arc with a magnetic field that is constant over time. Thus, one can in principle make as many turns as one can tolerate due to muon decay, therefore reducing the RF cost without increasing the arc cost. This paper reviews the current status of research into the design of FFAGs for muon acceleration. Several current designs are described and compared. General design considerations are also discussed

Cardiovascular magnetic resonance imaging in the assessment of carcinoid heart disease

Energy Technology Data Exchange (ETDEWEB)

Sandmann, H.; Pakkal, M. [Queen Elizabeth Hospital, Birmingham (United Kingdom); Steeds, R. [Queen Elizabeth Hospital, Birmingham (United Kingdom)], E-mail: rick.steeds@uhb.nhs.uk

2009-08-15

Carcinoid disease arises from a low-grade neuroendocrine tumour derived from serotonin-producing enterochromaffin cells. It is the most common tumour affecting the small bowel. The majority of patients who progress to carcinoid syndrome develop cardiac disease selectively involving the right side of the heart, whereas left heart disease is unusual. The most common cause of death is dilatation and dysfunction of the right ventricle. Right ventricular dysfunction is largely secondary to pathological endocardial fibrosis of the tricuspid and pulmonary valves, presenting with regurgitation and stenosis. Average survival falls to only 11 months with the onset of symptoms, but recent evidence suggests that survival can be improved by early surgery in selected individuals. This article reviews the particular role that cardiovascular magnetic resonance imaging has in the management of carcinoid heart disease.

Magnetic and Structural Design of a 15 T $Nb_3Sn$ Accelerator Depole Model

Energy Technology Data Exchange (ETDEWEB)

Kashikhin, V. V. [Fermilab; Andreev, N. [Fermilab; Barzi, E. [Fermilab; Novitski, I. [Fermilab; Zlobin, A. V. [Fermilab

2015-01-01

Hadron Colliders (HC) are the most powerful discovery tools in modern high energy physics. A 100 TeV scale HC with a nominal operation field of at least 15 T is being considered for the post-LHC era. The choice of a 15 T nominal field requires using the Nb3Sn technology. Practical demonstration of this field level in an accelerator-quality magnet and substantial reduction of the magnet costs are the key conditions for realization of such a machine. FNAL has started the development of a 15 T $Nb_{3}Sn$ dipole demonstrator for a 100 TeV scale HC. The magnet design is based on 4-layer shell type coils, graded between the inner and outer layers to maximize the performance. The experience gained during the 11-T dipole R&D campaign is applied to different aspects of the magnet design. This paper describes the magnetic and structural designs and parameters of the 15 T $Nb_3Sn$ dipole and the steps towards the demonstration model.

A fiber-optic strain measurement and quench localization system for use in superconducting accelerator dipole magnets

NARCIS (Netherlands)

van Oort, J.M.; Scanlan, Ronald M.; ten Kate, Herman H.J.

1995-01-01

A novel fiber-optic measurement system for superconducting accelerator magnets is described. The principal component is an extrinsic Fabry-Perot interferometer to determine localized strain and stress in coil windings. The system can be used either as a sensitive relative strain measurement system

Machine learning based analysis of cardiovascular images

NARCIS (Netherlands)

Wolterink, JM

2017-01-01

Cardiovascular diseases (CVDs), including coronary artery disease (CAD) and congenital heart disease (CHD) are the global leading cause of death. Computed tomography (CT) and magnetic resonance imaging (MRI) allow non-invasive imaging of cardiovascular structures. This thesis presents machine

Cardiovascular involvement in myositis

DEFF Research Database (Denmark)

Diederichsen, Louise P

2017-01-01

PURPOSE OF REVIEW: The purpose of this review is to provide an update on cardiovascular involvement in idiopathic inflammatory myopathy (IIM). Studies from the past 18 months are identified and reviewed. Finally, the clinical impact of these findings is discussed. RECENT FINDINGS: Epidemiological...... on cardiac magnetic resonance (CMR) imaging suggests that CMR should be considered as a potentially viable diagnostic tool to evaluate the possibility of silent myocardial inflammation in IIM with normal routine noninvasive evaluation. SUMMARY: Updated literature on cardiovascular involvement in IIM has...... identified an increased risk for subclinical and clinical cardiovascular disease in these rare inflammatory muscle diseases....

Value of black blood T2* cardiovascular magnetic resonance

Directory of Open Access Journals (Sweden)

Carpenter John Paul

2011-03-01

Full Text Available Abstract Purpose To assess whether black blood T2* cardiovascular magnetic resonance is superior to conventional white blood imaging of cardiac iron in patients with thalassaemia major (TM. Materials and methods We performed both conventional white blood and black blood T2* CMR sequences in 100 TM patients to determine intra and inter-observer variability and presence of artefacts. In 23 patients, 2 separate studies of both techniques were performed to assess interstudy reproducibility. Results Cardiac T2* values ranged from 4.5 to 43.8 ms. The mean T2* values were not different between black blood and white blood acquisitions (20.5 vs 21.6 ms, p = 0.26. Compared with the conventional white blood diastolic acquisition, the coefficient of variance of the black blood CMR technique was superior for intra-observer reproducibility (1.47% vs 4.23%, p Conclusions Black blood T2* CMR has superior reproducibility and reduced imaging artefacts for the assessment of cardiac iron, in comparison with the conventional white blood technique, which make it the preferred technique for clinical practice.

Non-isochronous spiral orbit particle accelerator and fixed frequency closed orbit particle accelerator

International Nuclear Information System (INIS)

Fujisawa, Takashi; Hattori, Toshiyuki

2006-01-01

One of the present inventions provides a spiral orbit charged particle accelerator in which the magnetic field increases as the radius increases more rapidly than an isochronous magnetic field distribution, and the distribution of fixed-frequency accelerating RF voltage is formed so that a harmonic number changes in integer for every particle revolution. The other invention realizes to make the closed orbit charged particle accelerator having a fixed frequency amplitude modulator that is able to modulate amplitude of the RF voltage so that a harmonic number decreases in integer in an every particle revolution. (author)

Can cardiovascular magnetic resonance prompt early cardiovascular/rheumatic treatment in autoimmune rheumatic diseases? Current practice and future perspectives.

Science.gov (United States)

Mavrogeni, Sophie I; Sfikakis, Petros P; Dimitroulas, Theodoros; Koutsogeorgopoulou, Loukia; Katsifis, Gikas; Markousis-Mavrogenis, George; Kolovou, Genovefa; Kitas, George D

2018-06-01

Life expectancy in autoimmune rheumatic diseases (ARDs) remains lower compared to the general population, due to various comoborbidities. Cardiovascular disease (CVD) represents the main contributor to premature mortality. Conventional and biologic disease-modifying antirheumatic drugs (DMARDs) have considerably improved long-term outcomes in ARDs not only by suppressing systemic inflammation but also by lowering CVD burden. Regarding atherosclerotic disease prevention, EULAR has recommended tight disease control accompanied by regular assessment of traditional CVD risk factors and lifestyle changes. However, this approach, although rational and evidence-based, does not account for important issues such as myocardial inflammation and the long asymptomatic period that usually proceeds clinical manifestations of CVD disease in ARDs before or after the diagnosis of systemic disease. Cardiovascular magnetic resonance (CMR) can offer reliable, reproducible and operator independent information regarding myocardial inflammation, ischemia and fibrosis. Some studies suggest a role for CMR in the risk stratification of ARDs and demonstrate that oedema/fibrosis visualisation with CMR may have the potential to inform cardiac and rheumatic treatment modification in ARDs with or without abnormal routine cardiac evaluation. In this review, we discuss how CMR findings could influence anti-rheumatic treatment decisions targeting optimal control of both systemic and myocardial inflammation irrespective of clinical manifestations of cardiac disease. CMR can provide a different approach that is very promising for risk stratification and treatment modification; however, further studies are needed before the inclusion of CMR in the routine evaluation and treatment of patients with ARDs.

Electron acceleration from rest to GeV energy by chirped axicon Gaussian laser pulse in vacuum in the presence of wiggler magnetic field

Science.gov (United States)

Kant, Niti; Rajput, Jyoti; Singh, Arvinder

2018-03-01

This paper presents a scheme of electron energy enhancement by employing frequency - chirped lowest order axicon focussed radially polarised (RP) laser pulse in vacuum under the influence of wiggler magnetic field. Terawatt RP laser can be focussed down to ∼5μm by an axicon optical element, which produces an intense longitudinal electric field. This unique property of axicon focused Gaussian RP laser pulse is employed for direct electron acceleration in vacuum. A linear frequency chirp increases the time duration of laser-electron interaction, whereas, the applied magnetic wiggler helps in improving the strength of ponderomotive force v→ ×B→ and periodically deflects electron in order to keep it traversing in the accelerating phase up to longer distance. Numerical simulations have been carried out to investigate the influence of laser, frequency chirp and magnetic field parameters on electron energy enhancement. It is noticed that an electron from rest can be accelerated up to GeV energy under optimized laser and magnetic field parameters. Significant enhancement in the electron energy gain of the order of 11.2 GeV is observed with intense chirped laser pulse in the presence of wiggler magnetic field of strength 96.2 kG.

Magnetic resonance imaging (MRI) of congenital cardiovascular malformations

International Nuclear Information System (INIS)

Sakakibara, Makoto; Kobayashi, Shirou; Imai, Hitoshi; Watanabe, Shigeru; Masuda, Yoshiaki; Inagaki, Yoshiaki; Morita, Huminori; Uematsu, Sadao; Arimizu, Noboru

1986-01-01

In order to determine the value of MRI in diagnosing congenital cardiovascular malformations, MR Images were obtained in 25 adult patients with congenital cardiovascular malformations. Gated MRI detected all of 13 atrial septal defects, and all of 4 ventricular septal defects, but ungated MRI detected none of 3 atrial septal defects. Other congenital cardiovascular malformations (2 with Ebstein's disease, 1 with Fallot's pentalogy, and 1 with Pulmonary stenosis) were well visualized. Vascular malformations (1 with Patent ducts arteriosus, 1 with Supravalvelar aortic stenosis, 1 with Coarctation of Aorta, 1 with Right Aortic Arch) were well visualized in all of 7 patients by ungated MRI. MRI was a valuable noninvasive method of diagnosing congenital heart disease. (author)

Design and construction of a novel compact doubly achromatic asymmetric 2700 magnet system for 25 MeV therapy electron accelerator

International Nuclear Information System (INIS)

Hutcheon, R.M.; Hodge, S.B.

1980-09-01

A modern cancer therapy electron accelerator unit must satisfy many design constraints, one of which is the isocentric height above floor level. Usually 130 cm is considered the maximum height at which a nurse can work with a patient. The advent of higher energy machines has increasingly made this more difficult to achieve, as higher magnetic fields are required in the magnet that directs the beam onto the patient. A new 270 degree doubly-achromatic magnet configuration has been developed which minimizes the isocentre height for a given maximum energy and maximum magnetic field. The system is an asymmetric two-magnet configuration, with zero field index, equal fields and a bend of greater than 180 degrees in the first magnet. It is compact, easy to manufacture and relatively insensitive to assembly tolerances. Energy defining slits are easily incorporated in the design and can readily be radiation shielded. Input and output beam matching and steering is easily accomplished with a compact input quadrupole doublet and small steering windings. This report details the design and bench testing of a head magnet for a 25 MeV electron accelerator with +- 10 percent energy acceptance. The output beam requirement is < 3 mm diameter with < +- 17 mrad angular divergence. (auth)

Magnetic discharge accelerating diode for the gas-filled pulsed neutron generators based on inertial confinement of ions

International Nuclear Information System (INIS)

Kozlovskij, K I; Shikanov, A E; Vovchenko, E D; Shatokhin, V L; Isaev, A A; Martynenko, A S

2016-01-01

The paper deals with magnetic discharge diode module with inertial electrostatic ions confinement for the gas-filled pulsed neutron generators. The basis of the design is geometry with the central hollow cathode surrounded by the outer cylindrical anode and electrodes made of permanent magnets. The induction magnitude about 0.1-0.4 T in the central region of the discharge volume ensures the confinement of electrons in the space of hollow (virtual) cathode and leads to space charge compensation of accelerated ions in the centre. The research results of different excitation modes in pulsed high-voltage discharge are presented. The stable form of the volume discharge preserveing the shape and amplitude of the pulse current in the pressure range of 10 -3 -10 -1 Torr and at the accelerating voltage up to 200 kV was observed. (paper)

D.C. side active filter for high stability accelerator magnet power supplies

International Nuclear Information System (INIS)

Singh, Yash Pal; Thakurta, A.C.; Kotaiah, S.

2006-01-01

Accelerator d.c, magnets have to produce a highly stable magnetic field which in turn needs highly stable d.c. current sources to energise them. Indus-II Q4 and Q5 power supplies are SCR based power supplies wherein the rectified voltage is fed to a passive filter to reduce the ripple voltage. The output of the passive filter still contains some ripple particularly on the low frequency side. The design and the test results of an active filter module have been discussed wherein the low frequency attenuation can be very effectively taken care of by allowing this to be absorbed in a coupling transformer put after the passive filter. Considerable size reduction has been achieved by using switching techniques. Low frequency attenuation has been made quite a simple task. This filter also helps in handling transients from input. (author)

Ultra-small superparamagnetic particles of iron oxide in magnetic resonance imaging of cardiovascular disease

Directory of Open Access Journals (Sweden)

Stirrat CG

2014-10-01

Full Text Available Colin G Stirrat,1 Alex T Vesey,1 Olivia MB McBride,1 Jennifer MJ Robson,1 Shirjel R Alam,1 William A Wallace,2 Scott I Semple,1,3 Peter A Henriksen,1 David E Newby1 1British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; 2Department of Pathology, University of Edinburgh, Edinburgh, UK; 3Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK Abstract: Ultra-small superparamagnetic particles of iron oxide (USPIO are iron-oxide based contrast agents that enhance and complement in vivo magnetic resonance imaging (MRI by shortening T1, T2, and T2* relaxation times. USPIO can be employed to provide immediate blood pool contrast, or to act as subsequent markers of cellular inflammation through uptake by inflammatory cells. They can also be targeted to specific cell-surface markers using antibody or ligand labeling. This review will discuss the application of USPIO contrast in MRI studies of cardiovascular disease. Keywords: cardiac, aortic, MRI, USPIO, carotid, vascular, molecular imaging

The EuCARD2 Future Magnets Program for Particle Accelerator High-Field Dipoles : Review of Results and Next Steps

NARCIS (Netherlands)

Rossi, Lucio; Badel, Arnaud; Bajas, Hugues; Bajko, Marta; Ballarino, Amalia; Barth, Christian; Betz, Ulrich; Bottura, Luca; Broggi, Francesco; Chiuchiolo, Antonella; Dhalle, Marc; Durante, Maria; Fazilleau, Philippe; Fleiter, Jerome; Gao, Peng; Goldacker, Wilfried; Kario, Anna; Kirby, Glyn; Haro, E.; Himbele, J.; Lorin, C.; Murtomaki, J.; Van Nugteren, Jeroen; Petrone, Carlo; De Rijk, Gijs; Ruuskanen, J.; Senatore, Carmine; Statera, Marco; Stenvall, Antti; Tixador, Pascal; Yang, Yifeng; Usoskin, Alexander; Zangenberg, Nikolaj

The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be tested in small coils and magnets capable to deliver 3-5 T when energized in stand-alone mode, and 15-18 T when inserted in a 12-13 T background

Accelerated healing of cardiovascular textiles promoted by an RGD peptide.

Science.gov (United States)

Tweden, K S; Harasaki, H; Jones, M; Blevitt, J M; Craig, W S; Pierschbacher, M; Helmus, M N

1995-07-01

Polytetrafluoroethylene (PTFE) and polyethylene terephthalate (Dacron polyester) fabrics are used extensively in cardiovascular devices, e.g. heart valve sewing cuffs and vascular prostheses. While devices containing these fabrics are generally successful, it is recognized that fabrics cause complications prior to tissue ingrowth due to their thrombogenic nature. A surface active synthetic peptide, called PepTite Coating (PepTite), which was modeled after the cell attachment domain of human fibronectin has been marketed as a biocompatible coating. This peptide stimulates cell attachment through the arginine-glycine-aspartic acid (RGD) sequence. Modification of medical implants with PepTite has been shown to promote ingrowth of surrounding cells into the material leading to better tissue integration, reduced inflammation and reduced fibrotic encapsulation. In this study, polyester and PTFE textiles were modified with PepTite. The effectiveness of this coating in enhancing wound healing was investigated in a simple vascular and cardiac valve model. Our results indicate that the RGD-containing peptide, PepTite, promoted the formation of an endothelial-like cell layer on both polyester and PTFE vascular patches in the dog model. PepTite was also found to promote the formation of a significantly thinner neointima (pannus) on polyester as compared to that on its uncoated control. These results were corroborated in the cardiac valve model in which a greater amount of thin pannus and less thrombus were seen on coated polyester sewing cuffs than on control uncoated cuffs. This research shows the promising tissue response to RGD coated textiles and the potential role of this peptide in material passivation via accelerated healing.

Advanced Accelerators for Medical Applications

Science.gov (United States)

Uesaka, Mitsuru; Koyama, Kazuyoshi

We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter “linac”); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laser-based acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

SSC accelerator physics

International Nuclear Information System (INIS)

Anon.

1985-01-01

Accelerator physicists at LBL began intensive work on the SSC in 1983, in support of the proposed 6.5-T magnet design, which, in turn, became reference design A during the Reference Designs Study. In that same study, LBL physicists formed the core of the accelerator physics group led by Fermilab's Don Edwards. In a period of only a few months, that group established preliminary parameters for a near-optimal design, produced conceptual designs based on three magnet types, addressed all significant beam lifetime and stability issues, and identified areas requiring further R and D. Since the conclusion of the Reference Designs Study, work has focused on the key SSC design issue, namely, single-particle stability in an imperfect magnetic field. At the end of fiscal 1984, much of the LBL accelerator physics group took its place in the SSC Central Design Group, whose headquarters at LBL will be the focus of nationwide SSC R and D efforts over the next several years

A permanent magnet electron beam spread system used for a low energy electron irradiation accelerator

International Nuclear Information System (INIS)

Huang Jiang; Xiong Yongqian; Chen Dezhi; Liu Kaifeng; Yang Jun; Li Dong; Yu Tiaoqin; Fan Mingwu; Yang Bo

2014-01-01

The development of irradiation processing industry brings about various types of irradiation objects and expands the irradiation requirements for better uniformity and larger areas. This paper proposes an innovative design of a permanent magnet electron beam spread system. By clarifying its operation principles, the author verifies the feasibility of its application in irradiation accelerators for industrial use with the examples of its application in electron accelerators with energy ranging from 300 keV to 1 MeV. Based on the finite element analyses of electromagnetic fields and the charged particle dynamics, the author also conducts a simulation of electron dynamics in magnetic field on a computer. The results indicate that compared with the traditional electron beam scanning system, this system boosts the advantages of a larger spread area, non-power supply, simple structure and low cost, etc., which means it is not only suitable for the irradiation of objects with the shape of tubes, strips and panels, but can also achieve a desirable irradiation performance on irregular constructed objects of large size. (authors)

Application of magnetically insulated transmission lines for high current, high voltage electron beam accelerators

International Nuclear Information System (INIS)

Shope, S.L.; Mazarakis, M.G.; Frost, C.A.; Poukey, J.W.; Turman, B.N.

1993-01-01

Self Magnetically Insulated Transmission Lines (MITL) adders have been used successfully in a number of Sandia accelerators such as HELIA, HERMES III, and SABRE. Most recently the authors used a MITL adder in the RADLAC/SMILE electron beam accelerator to produce high quality, small radius (r b < 2 cm), 11 to 15 MeV, 50 to 100-kA beams with a small transverse velocity v perpendicular/c = β perpendicular ≤ 0.1. In RADLAC/SMILE, a coaxial MITL passed through the eight, 2 MV vacuum envelopes. The MITL summed the voltages of all eight feeds to a single foilless diode. The experimental results are in good agreement with code simulations. The authors' success with the MITL technology led them to investigate the application to higher energy accelerator designs. They have a conceptual design for a cavity-fed MITL that sums the voltages from 100 identical, inductively-isolated cavities. Each cavity is a toroidal structure that is driven simultaneously by four 8-ohm pulse-forming lines, providing a 1-MV voltage pulse to each of the 100 cavities. The point design accelerator is 100 MV, 500 kA, with a 30-50-ns FWHM output pulse

Application of Magnetically Insulated Transmission Lines for high current, high voltage electron beam accelerators

International Nuclear Information System (INIS)

Shope, S.L.; Mazarakis, M.G.; Frost, C.A.; Poukey, J.W.; Turman, B.N.

1991-01-01

Self Magnetically Insulated Transmission Lines (MITL) adders have been used successfully in a number of Sandia accelerators such as HELIA, HERMES III, and SABRE. Most recently we used at MITL adder in the RADLAC/SMILE electron beam accelerator to produce high quality, small radius (r ρ < 2 cm), 11 to 15 MeV, 50 to 100-kA beams with a small transverse velocity v perpendicular/c = β perpendicular ≤ 0.1. In RADLAC/SMILE, a coaxial MITL passed through the eight, 2 MV vacuum envelopes. The MITL summed the voltages of all eight feeds to a single foilless diode. The experimental results are in good agreement with code simulations. Our success with the MITL technology led us to investigate the application to higher energy accelerator designs. We have a conceptual design for a cavity-fed MITL that sums the voltages from 100 identical, inductively-isolated cavities. Each cavity is a toroidal structure that is driven simultaneously by four 8-ohm pulse-forming lines, providing a 1-MV voltage pulse to each of the 100 cavities. The point design accelerator is 100 MV, 500 kA, with a 30--50 ns FWHM output pulse. 10 refs

Application of magnetically insulated transmission lines for high current, high voltage electron beam accelerators

Science.gov (United States)

Shope, S. L.; Mazarakis, M. G.; Frost, C. A.; Poukey, J. W.; Turman, B. N.

Self Magnetically Insulated Transmission Lines (MITL) adders were used successfully in a number of Sandia accelerators such as HELIA, HERMES III, and SABRE. Most recently we used at MITL adder in the RADLAC/SMILE electron beam accelerator to produce high quality, small radius (r(sub rho) less than 2 cm), 11 - 15 MeV, 50 - 100-kA beams with a small transverse velocity v(perpendicular)/c = beta(perpendicular) less than or equal to 0.1. In RADLAC/SMILE, a coaxial MITL passed through the eight, 2 MV vacuum envelopes. The MITL summed the voltages of all eight feeds to a single foilless diode. The experimental results are in good agreement with code simulations. Our success with the MITL technology led us to investigate the application to higher energy accelerator designs. We have a conceptual design for a cavity-fed MITL that sums the voltages from 100 identical, inductively-isolated cavities. Each cavity is a toroidal structure that is driven simultaneously by four 8-ohm pulse-forming lines, providing a 1-MV voltage pulse to each of the 100 cavities. The point design accelerator is 100 MV, 500 kA, with a 30 - 50 ns FWHM output pulse.

Particle acceleration by inverse-Weibel instability

International Nuclear Information System (INIS)

Kawata, S.

1996-01-01

A high demagnetization rate delta B/delta t can be obtained through fast decoupling of a magnetic field from an electric circuit which generates the magnetic field. Nowadays fast decoupling is possible by present switching technologies. A high particle-acceleration gradient can be obtained in an inductive acceleration system compared with that in a conventional induction accelerator. Based on this new proposal, inductive ion and electron accelerations were investigated numerically. The mechanism presented can be considered as pseudo-inverse Weibel instability. (author). 3 figs., 7 refs

Particle acceleration by inverse-Weibel instability

Energy Technology Data Exchange (ETDEWEB)

Kawata, S [Nagaoka Univ. of Technology (Japan). Dept. of Electrical Engineering

1997-12-31

A high demagnetization rate delta B/delta t can be obtained through fast decoupling of a magnetic field from an electric circuit which generates the magnetic field. Nowadays fast decoupling is possible by present switching technologies. A high particle-acceleration gradient can be obtained in an inductive acceleration system compared with that in a conventional induction accelerator. Based on this new proposal, inductive ion and electron accelerations were investigated numerically. The mechanism presented can be considered as pseudo-inverse Weibel instability. (author). 3 figs., 7 refs.

Reducing sedation for pediatric body MRI using accelerated and abbreviated imaging protocols

International Nuclear Information System (INIS)

Ahmad, Rizwan; Hu, Houchun Harry; Krishnamurthy, Ramkumar; Krishnamurthy, Rajesh

2018-01-01

Magnetic resonance imaging (MRI) is an established diagnostic imaging tool for investigating pediatric disease. MRI allows assessment of structure, function, and morphology in cardiovascular imaging, as well as tissue characterization in body imaging, without the use of ionizing radiation. For MRI in children, sedation and general anesthesia (GA) are often utilized to suppress patient motion, which can otherwise compromise image quality and diagnostic efficacy. However, evidence is emerging that use of sedation and GA in children might have long-term neurocognitive side effects, in addition to the short-term procedure-related risks. These concerns make risk-benefit assessment of sedation and GA more challenging. Therefore, reducing or eliminating the need for sedation and GA is an important goal of imaging innovation and research in pediatric MRI. In this review, the authors focus on technical and clinical approaches to reducing and eliminating the use of sedation in the pediatric population based on image acquisition acceleration and imaging protocols abbreviation. This paper covers important physiological and technical considerations for pediatric body MR imaging and discusses MRI techniques that offer the potential of recovering diagnostic-quality images from accelerated scans. In this review, the authors also introduce the concept of reporting elements for important indications for pediatric body MRI and use this as a basis for abbreviating the MR protocols. By employing appropriate accelerated and abbreviated approaches based on an understanding of the imaging needs and reporting elements for a given clinical indication, it is possible to reduce sedation and GA for pediatric chest, cardiovascular and abdominal MRI. (orig.)

Reducing sedation for pediatric body MRI using accelerated and abbreviated imaging protocols

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Rizwan [The Ohio State University, Department of Biomedical Engineering, Columbus, OH (United States); Hu, Houchun Harry; Krishnamurthy, Ramkumar; Krishnamurthy, Rajesh [Nationwide Children' s Hospital, Department of Radiology, Columbus, OH (United States)

2018-01-15

Magnetic resonance imaging (MRI) is an established diagnostic imaging tool for investigating pediatric disease. MRI allows assessment of structure, function, and morphology in cardiovascular imaging, as well as tissue characterization in body imaging, without the use of ionizing radiation. For MRI in children, sedation and general anesthesia (GA) are often utilized to suppress patient motion, which can otherwise compromise image quality and diagnostic efficacy. However, evidence is emerging that use of sedation and GA in children might have long-term neurocognitive side effects, in addition to the short-term procedure-related risks. These concerns make risk-benefit assessment of sedation and GA more challenging. Therefore, reducing or eliminating the need for sedation and GA is an important goal of imaging innovation and research in pediatric MRI. In this review, the authors focus on technical and clinical approaches to reducing and eliminating the use of sedation in the pediatric population based on image acquisition acceleration and imaging protocols abbreviation. This paper covers important physiological and technical considerations for pediatric body MR imaging and discusses MRI techniques that offer the potential of recovering diagnostic-quality images from accelerated scans. In this review, the authors also introduce the concept of reporting elements for important indications for pediatric body MRI and use this as a basis for abbreviating the MR protocols. By employing appropriate accelerated and abbreviated approaches based on an understanding of the imaging needs and reporting elements for a given clinical indication, it is possible to reduce sedation and GA for pediatric chest, cardiovascular and abdominal MRI. (orig.)

Virtual Accelerator for Accelerator Optics Improvement

CERN Document Server

Yan Yi Ton; Decker, Franz Josef; Ecklund, Stanley; Irwin, John; Seeman, John; Sullivan, Michael K; Turner, J L; Wienands, Ulrich

2005-01-01

Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling eigen-plane ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and linear coupling reduction to improve PEP-II luminosity.

Recent results of studies of acceleration of compact toroids

International Nuclear Information System (INIS)

Hammer, J.H.; Hartman, C.W.; Eddleman, J.

1984-01-01

The observed gross stability and self-contained structure of compact toroids (CT's) give rise to the possibility, unique among magnetically confined plasmas, of translating CT's from their point of origin over distances many times their own length. This feature has led us to consider magnetic acceleration of CT's to directed kinetic energies much greater than their stored magnetic and thermal energies. A CT accelerator falls in the very broad gap between traditional particle accelerators at one extreme, which are limited in the number of particles per bunch by electrostatic repulsive forces, and mass accelerators such as rail guns at the other extreme, which accelerate many particles but are forced by the stress limitations of solids to far smaller accelerations. A typical CT has about a Coulomb of particles, weighs 10 micrograms and can be accelerated by magnetic forces of several tons, leading to an acceleration on the order of 10 11 gravities

Compact toroid formation, compression, and acceleration

International Nuclear Information System (INIS)

Degnan, J.H.; Peterkin, R.E. Jr.; Baca, G.P.; Beason, J.D.; Bell, D.E.; Dearborn, M.E.; Dietz, D.; Douglas, M.R.; Englert, S.E.; Englert, T.J.; Hackett, K.E.; Holmes, J.H.; Hussey, T.W.; Kiuttu, G.F.; Lehr, F.M.; Marklin, G.J.; Mullins, B.W.; Price, D.W.; Roderick, N.F.; Ruden, E.L.; Sovinec, C.R.; Turchi, P.J.; Bird, G.; Coffey, S.K.; Seiler, S.W.; Chen, Y.G.; Gale, D.; Graham, J.D.; Scott, M.; Sommars, W.

1993-01-01

Research on forming, compressing, and accelerating milligram-range compact toroids using a meter diameter, two-stage, puffed gas, magnetic field embedded coaxial plasma gun is described. The compact toroids that are studied are similar to spheromaks, but they are threaded by an inner conductor. This research effort, named MARAUDER (Magnetically Accelerated Ring to Achieve Ultra-high Directed Energy and Radiation), is not a magnetic confinement fusion program like most spheromak efforts. Rather, the ultimate goal of the present program is to compress toroids to high mass density and magnetic field intensity, and to accelerate the toroids to high speed. There are a variety of applications for compressed, accelerated toroids including fast opening switches, x-radiation production, radio frequency (rf) compression, as well as charge-neutral ion beam and inertial confinement fusion studies. Experiments performed to date to form and accelerate toroids have been diagnosed with magnetic probe arrays, laser interferometry, time and space resolved optical spectroscopy, and fast photography. Parts of the experiment have been designed by, and experimental results are interpreted with, the help of two-dimensional (2-D), time-dependent magnetohydrodynamic (MHD) numerical simulations. When not driven by a second discharge, the toroids relax to a Woltjer--Taylor equilibrium state that compares favorably to the results of 2-D equilibrium calculations and to 2-D time-dependent MHD simulations. Current, voltage, and magnetic probe data from toroids that are driven by an acceleration discharge are compared to 2-D MHD and to circuit solver/slug model predictions. Results suggest that compact toroids are formed in 7--15 μsec, and can be accelerated intact with material species the same as injected gas species and entrained mass ≥1/2 the injected mass

Plasma wave accelerator. II

International Nuclear Information System (INIS)

Mori, W.; Joshi, C.; Dawson, J.M.

1982-01-01

It was shown that the insertion of a cross magnetic field prevents the particles from getting out of phase with the electric field of the plasma wave in the beat wave accelerator scheme. Thus, using a CO 2 laser, n/sub c//n/sub e/ = (ω 0 /ω/sub p/) 2 approx. 35, and a 300 kG magnetic field, electrons can be (in principle) accelerated to 100 GeV in 2 meters. For comparison without the magnetic field, the same energies may be obtained in a n/sub c//n/sub e/ approx. 10 5 plasma over a distance of 100 meters

Magnetic permeability of stainless steel for use in accelerator beam transport systems

International Nuclear Information System (INIS)

Wilson, N.G.; Bunch, P.

1991-01-01

High-vacuum beam transport tubes are being designed for use in an accelerator under development at Los Alamos. In areas such as weld-heat-affected zones, the tubes will require localized magnetic permeability of less than 1.02. Seven austenitic stainless steel candidates, 304L, 310, 316L, 317LN, 20Cb-3, Nitronic 33, and Nitronic 40, have been evaluated to determine their permeability in cold-worked, annealed, and weld-affected zones. 310 and 20Cb-3 showed permeability after welding of less than 1.01. 1 ref., 1 fig., 1 tab

Low-field permanent magnet quadrupoles in a new relativistic-klystron two-beam accelerator design

Energy Technology Data Exchange (ETDEWEB)

Yu, S.; Sessler, A. [Lawrence Berkeley Lab., CA (United States)

1995-02-01

Permanent magnets play a central role in the new relativistic klystron two-beam-accelerator design. The two key goals of this new design, low cost and the suppression of beam break-up instability are both intimately tied to the permanent magnet quadrupole focusing system. A recently completed systems study by a joint LBL-LLNL team concludes that a power source for a 1 TeV center-of-mass Next Linear Collider based on the new TBA design can be as low as $1 billion, and the efficiency (wall plug to rf) is estimated to be 36%. End-to-end simulations of longitudinal and transverse beam dynamics show that the drive beam is stable over the entire TBA unit.

Particle acceleration in pulsar magnetospheres

International Nuclear Information System (INIS)

Baker, K.B.

1978-10-01

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

The histological basis of late gadolinium enhancement cardiovascular magnetic resonance in a patient with Anderson-Fabry disease

OpenAIRE

Moon, J. C.; Sheppard, M.; Reed, E.; Lee, P.; Elliott, P. M.; Pennell, D. J.

2006-01-01

Anderson-Fabry Disease (AFD) is a storage disease that mimics hypertrophic cardiomyopathy. Late gadolinium enhancement (LGE) by cardiovascular magnetic resonance occurs in approximately 50% of patients in the basal inferolateral LV wall, but how an intracellular storage disease causes focal LGE is unknown. We present a whole-heart histological validation that LGE is caused by focal myocardial collagen scarring. This scarring may be the substrate for electrical re-entry and sudden arrhythmic d...

Instabilities of bellows: Dependence on internal pressure, end supports, and interactions in accelerator magnet systems

International Nuclear Information System (INIS)

Shutt, R.P.; Rehak, M.L.

1990-01-01

For superconducting magnets, one needs many bellows for connection of various helium cooling transfer lines in addition to beam tube bellows. There could be approximately 10,000 magnet interconnection bellows in the SSC exposed to an internal pressure. When axially compressed or internally pressurized, bellows can become unstable, leading to gross distortion or complete failure. If several bellows are contained in an assembly, failure modes might interact. If designed properly, large bellows can be a very feasible possibility for connecting the large tubular shells that support the magnet iron yokes and superconducting coils and contain supercritical helium for magnet cooling. We present here (1) a spring-supported bellows model, in order to develop necessary design features for bellows and end supports so that instabilities will not occur in the bellows pressure operating region, including some margin, (2) a model of three superconducting accelerator magnets connected by two large bellows, in order to ascertain that support requirements are satisfied and in order to study interaction effects between the two bellows. Reliability of bellows for our application will be stressed. 3 refs., 4 figs

Non Hodgkin lymphoma metastasis to the heart detected by cardiovascular magnetic resonance; Metastasis cardiaca secundaria al linfoma de Hodgkin detectada por la resonancia magnetica cardiovascular

Energy Technology Data Exchange (ETDEWEB)

Martinez, Florange; Morales, Marisela; Pedreanez, Norma [Hospital Cardiologico Infantil Latinoamericano Dr Gilberto Rodriguez Ochoa, Carcacas (Venezuela, Bolivarian Republic of); Pabon, Luz; Carrillo, Milton [Universidad Central de Venezuela (UCV/HUC), Caracas (Venezuela, Bolivarian Republic of). Instituto de Hematoncologia. Hospital Universitario; Fernandes, Juliano Lara [Universidade de Campinas (UNICAMP), SP (Brazil)

2009-10-15

Primary and secondary heart tumors are relatively rare occurrences but usually imply significant treatment decisions. The differential diagnosis among these tumors and other masses can sometimes be difficult and require the use of different imaging modalities to establish a confident verdict. Cardiovascular magnetic resonance CMR imaging is a very useful tool in these cases by allowing for the application of different strategies to better delineate masses, heart structures and adjacent tissues. In this case description, we present a woman with shortness of breath and a paracardiac mass showing how CMR can be applied. (author)

Accelerated plan to develop magnetic fusion energy

International Nuclear Information System (INIS)

Fowler, T.K.

1986-01-01

We have shown that, despite funding delays since the passage of the Magnetic Fusion Engineering Act of 1980, fusion development could still be carried to the point of a demonstration plant by the year 2000 as called for in the Act if funding, now about $365 million per year, were increased to the $1 billion range over the next few years (see Table I). We have also suggested that there may be an economic incentive for the private sector to become in accelerating fusion development on account of the greater stability of energy production costs from fusion. Namely, whereas fossil fuel prices will surely escalate in the course of time, fusion fuel will always be abundantly available at low cost; and fusion technology poses less future risk to the public and the investor compared to conventional nuclear power. In short, once a fusion plant is built, the cost of generating electricity mainly the amortization of the plant capital cost - would be relatively fixed for the life of the plant. In Sec. V, we found that the projected capital cost of fusion plants ($2000 to $4000 per KW/sub e/) would probably be acceptable if fusion plants were available today

On radiation heating of superconducting magnets of the accelerating-storage complex

International Nuclear Information System (INIS)

Maslov, M.A.; Mokhov, N.V.

1981-01-01

To analyze regularities of energy release formation in a superconducting winding (SCW) of superconducting magnets (SCM) of the IHEP accelerating-storage facility the energy release values in the SCM when 400-3000 GeV proton beam incidence onto the SCM vacuum chamber are calculated. Two SCM modifications (a dipole one and a quadrupole one) and two modes of irradiation (uniform irradiation along the SCM azimuth and length and a thin beam incidence uniform along the SCM length) are considered. It is shown that for the SCM with the 26 cm aperture at the 1 mrad angle of incidence 25% of the initial proton energy is released [ru

A data processing method for determining instantaneous angular speed and acceleration of crankshaft in an aircraft engine-propeller system using a magnetic encoder

Science.gov (United States)

Yu, S. D.; Zhang, X.

2010-05-01

This paper presents a method for determining the instantaneous angular speed and instantaneous angular acceleration of the crankshaft in a reciprocating engine and propeller dynamical system from electrical pulse signals generated by a magnetic encoder. The method is based on accurate determination of the measured global mean angular speed and precise values of times when leading edges of individual magnetic teeth pass through the magnetic sensor. Under a steady-state operating condition, a discrete deviation time vs. shaft rotational angle series of uniform interval is obtained and used for accurate determination of the crankshaft speed and acceleration. The proposed method for identifying sub- and super-harmonic oscillations in the instantaneous angular speeds and accelerations is new and efficient. Experiments were carried out on a three-cylinder four-stroke Saito 450R model aircraft engine and a Solo propeller in connection with a 64-teeth Admotec KL2202 magnetic encoder and an HS-4 data acquisition system. Comparisons with an independent data processing scheme indicate that the proposed method yields noise-free instantaneous angular speeds and is superior to the finite difference based methods commonly used in the literature.

Electron cyclotron harmonic wave acceleration

Science.gov (United States)

Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

1987-01-01

A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

Electron cyclotron harmonic wave acceleration

International Nuclear Information System (INIS)

Karimabadi, H.; Menyuk, C.R.; Sprangle, P.; Vlahos, L.; Salonika Univ., Greece)

1987-01-01

A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts. 31 references

Ion optics for accelerators

International Nuclear Information System (INIS)

Enge, H.A.

1974-01-01

A review is given of ion-optic devices used in particle accelerators, including electrostatic lenses, magnetic quadrupoles, and deflecting magnets. Tube focusing in dc accelerators is also treated, and a novel scheme for shaping the electrodes to produce strong focusing is described. The concepts of emittance (phase space) and emittance conservation are briefly discussed. Chromatic and spatial aberrations are introduced, and it is shown how they can be calculated and sometimes substantially reduced. Some examples are given

A cyclotron resonance laser accelerator

International Nuclear Information System (INIS)

Sprangle, P.; Tang, C.M.; Vlahos, L.

1983-01-01

A laser acceleration mechanism which utilizes a strong static, almost uniform, magnetic field together with an intense laser pulse is analyzed. The interaction and acceleration mechanism relies on a self resonance effect. Since the laser field is assumed to be diffraction limited, the magnetic field must be spatially varied to maintain resonance. The effective accelerating gradient is shown to scale like 1/√E /SUB b/ , where E /SUB b/ is the electron energy. For a numerical illustration the authors consider a 1 x 10 13 W/cm 2 , CO 2 laser and show that electrons can be accelerated to more than 500 MeV in a distance of 15 m (approximately two Rayleigh lengths)

Advanced accelerator research and development

International Nuclear Information System (INIS)

Anon.

1974-01-01

Research and development on the Positron-Electron Project (PEP), the electron rings, the superconducting accelerator (ESCAR), and the superconductivity program are reported. Efforts relating to the proposed PEP include work on: (1) the injection system; (2) the rf system; (3) the main-ring bend magnets; (4) the magnet power supplies and controls; (5) alignment; (6) radiation and shielding; (7) the vacuum system; and (8) conventional facilities (utilities, etc.). Experimental and theoretical work continued on the development of suitably intense electron rings as vehicles for the collective acceleration of ions. The most difficult problem was found to be the longitudinal (negative mass) instability. Design work was begun for ESCAR (Experimental Superconducting Accelerating Ring), a small proton synchrotron and storage ring using superconducting magnets, which should aid in the design of future large superconducting facilities. Magnet development was largely directed toward the detailed design of the dipole units. A superconducting beam transport line was installed at the Bevatron. (PMA)

Cardiovascular responses of semi-arboreal snakes to chronic, intermittent hypergravity

Science.gov (United States)

Lillywhite, H. B.; Ballard, R. E.; Hargens, A. R.

1996-01-01

Cardiovascular functions were studied in semi-arboreal rat snakes (Elaphe obsoleta) following long-term, intermittent exposure to +1.5 Gz (head-to-tail acceleration) on a centrifuge. Snakes were held in a nearly straight position within horizontal plastic tubes during periods of centrifugation. Centrifugal acceleration, therefore, subjected snakes to a linear force gradient with the maximal force being experienced at the tail. Compared to non-centrifuged controls, Gz-acclimated snakes showed greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of corticosterone, and higher blood ratios of prostaglandin F 2 alpha/prostaglandin E2. Cardiovascular tolerance to increased gravity during graded Gz acceleration was measured as the maximum (caudal) acceleration force at which carotid arterial blood flow became null. When such tolerances were adjusted for effects of body size and other continuous variables incorporated into an analysis of covariance, the difference between the adjusted mean values of control and acclimated snakes (2.37 and 2.84 Gz, respectively) corresponded closely to the 0.5 G difference between the acclimation G (1.5) and Earth gravity (1.0). As in other vertebrates, cardiovascular tolerance to Gz stress tended to be increased by acclimation, short body length, high arterial pressure, and comparatively large blood volume. Voluntary body movements were important for promoting carotid blood flow at the higher levels of Gz stress.

Acceleration mechanisms flares, magnetic reconnection and shock waves

International Nuclear Information System (INIS)

Colgate, S.A.

1979-01-01

Several mechanisms are briefly discussed for the acceleration of particles in the astrophysical environment. Included are hydrodynamic acceleration, spherically convergent shocks, shock and a density gradient, coherent electromagnetic acceleration, the flux tube origin, symmetries and instabilities, reconnection, galactic flares, intergalactic acceleration, stochastic acceleration, and astrophysical shocks. It is noted that the supernova shock wave models still depend critically on the presupernova star structure and the assumption of highly compact presupernova models for type I supernovae. 37 references

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS

International Nuclear Information System (INIS)

2004-01-01

Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation

ELECTRON ACCELERATION BY MULTI-ISLAND COALESCENCE

International Nuclear Information System (INIS)

Oka, M.; Phan, T.-D.; Krucker, S.; Fujimoto, M.; Shinohara, I.

2010-01-01

Energetic electrons of up to tens of MeV are created during explosive phenomena in the solar corona. While many theoretical models consider magnetic reconnection as a possible way of generating energetic electrons, the precise roles of magnetic reconnection during acceleration and heating of electrons still remain unclear. Here, we show from two-dimensional particle-in-cell simulations that coalescence of magnetic islands that naturally form as a consequence of tearing mode instability and associated magnetic reconnection leads to efficient energization of electrons. The key process is the secondary magnetic reconnection at the merging points, or the 'anti-reconnection', which is, in a sense, driven by the converging outflows from the initial magnetic reconnection regions. By following the trajectories of the most energetic electrons, we found a variety of different acceleration mechanisms but the energization at the anti-reconnection is found to be the most important process. We discuss possible applications to the energetic electrons observed in the solar flares. We anticipate our results to be a starting point for more sophisticated models of particle acceleration during the explosive energy release phenomena.

Gadolinium enhanced cardiovascular magnetic resonance in Anderson-Fabry disease. Evidence for a disease specific abnormality of the myocardial interstitium.

Science.gov (United States)

Moon, James C C; Sachdev, Bhavesh; Elkington, Andrew G; McKenna, William J; Mehta, Atul; Pennell, Dudley J; Leed, Philip J; Elliott, Perry M

2003-12-01

Anderson-Fabry Disease (AFD), an X-linked disorder of sphingolipid metabolism, is a cause of idiopathic left ventricular hypertrophy but the mechanism of hypertrophy is poorly understood. Gadolinium enhanced cardiovascular magnetic resonance can detect focal myocardial fibrosis. We hypothesised that hyperenhancement would be present in AFD. Eighteen males (mean 43+/-14 years) and eight female heterozygotes (mean 48+/-12 years) with AFD underwent cine and late gadolinium cardiovascular magnetic resonance. Nine male (50%) had myocardial hyperenhancement ranging from 3.4% to 20.6% (mean 7.7+/-5.7%) of total myocardium; in males, percentage hyperenhancement related to LV mass index (r=0.78, P=0.0002) but not to ejection fraction or left ventricular volumes. Lesser hyperenhancement was also found in four (50%) heterozygous females (mean 4.6%). In 12 (92%) patients with abnormal gadolinium uptake, hyperenhancement occurred in the basal infero-lateral wall where, unlike myocardial infarction, it was not sub-endocardial. In two male patients with severe LVH (left ventricular hypertrophy) and systolic impairment there was additional hyperenhancement in other myocardial segments. These observations suggests that myocardial fibrosis occurs in AFD and may contribute to the hypertrophy and the natural history of the disease.

Heavy ion acceleration strategies in the AGS accelerator complex -- 1994 Status report

International Nuclear Information System (INIS)

Ahrens, L.A.; Benjamin, J.; Blaskiewicz, M.

1995-01-01

The strategies invoked to satisfy the injected beam specifications for the Brookhaven Relativistic Heavy Ion Collider (RHIC) continue to evolve, in the context of the yearly AGS fixed target heavy ion physics runs. The primary challenge is simply producing the required intensity. The acceleration flexibility available particularly in the Booster main magnet power supply and rf accelerating systems, together with variations in the charge state delivered from the Tandem van de Graaff, and accommodation by the AGS main magnet and rf systems allow the possibility for a wide range of options. The yearly physics run provides the opportunity for exploration of these options with the resulting significant evolution in the acceleration plan. This was particularly true in 1994 with strategies involving three different charge states and low and high acceleration rates employed in the Booster. The present status of this work will be presented

21 CFR 870.3690 - Pacemaker test magnet.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pacemaker test magnet. 870.3690 Section 870.3690...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3690 Pacemaker test magnet. (a) Identification. A pacemaker test magnet is a device used to test an inhibited or triggered type...

Electron acceleration by turbulent plasmoid reconnection

Science.gov (United States)

Zhou, X.; Büchner, J.; Widmer, F.; Muñoz, P. A.

2018-04-01

In space and astrophysical plasmas, like in planetary magnetospheres, as that of Mercury, energetic electrons are often found near current sheets, which hint at electron acceleration by magnetic reconnection. Unfortunately, electron acceleration by reconnection is not well understood yet, in particular, acceleration by turbulent plasmoid reconnection. We have investigated electron acceleration by turbulent plasmoid reconnection, described by MHD simulations, via test particle calculations. In order to avoid resolving all relevant turbulence scales down to the dissipation scales, a mean-field turbulence model is used to describe the turbulence of sub-grid scales and their effects via a turbulent electromotive force (EMF). The mean-field model describes the turbulent EMF as a function of the mean values of current density, vorticity, magnetic field as well as of the energy, cross-helicity, and residual helicity of the turbulence. We found that, mainly around X-points of turbulent reconnection, strongly enhanced localized EMFs most efficiently accelerated electrons and caused the formation of power-law spectra. Magnetic-field-aligned EMFs, caused by the turbulence, dominate the electron acceleration process. Scaling the acceleration processes to parameters of the Hermean magnetotail, electron energies up to 60 keV can be reached by turbulent plasmoid reconnection through the thermal plasma.

Magnetic design of a FFAG superconducting magnet

International Nuclear Information System (INIS)

Obana, T.; Ogitsu, T.; Nakamoto, T.; Sasaki, K.; Yamamoto, A.; Yoshimoto, M.; Mori, Y.; Orikasa, T.

2005-01-01

A superconducting magnet for a Fixed Field Alternating Gradient (FFAG) accelerator has been proposed. The required magnetic field is static and proportional to the k-th power of the orbit radius where k is the geometrical field index of the accelerator. In 2D, the required magnetic field can be generated with the optimized cross section of the coil. The cross section of the coils is a left-right asymmetry to simplify the cross section and ellipse to downsize the magnet. Local and integral 3D fields along the beam trajectory are evaluated with using new type of 3D coil configuration

The use of induction linacs with nonlinear magnetic drive as high average power accelerators

International Nuclear Information System (INIS)

Birx, D.L.; Cook, E.G.; Hawkins, S.A.; Newton, M.A.; Poor, S.E.; Reginato, L.L.; Schmidt, J.A.; Smith, M.W.

1985-01-01

The marriage of induction linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 MeV/m, and with power efficiences approaching 50%. A 2 MeV, 5 kA electron accelerator is under construction at Lawrence Livermore National Laboratory (LLNL) to allow us to demonstrate some of these concepts. Progress on this project is reported here. (orig.)

Accelerator and Fusion Research Division. Annual report, October 1977--September 1978

Energy Technology Data Exchange (ETDEWEB)

1979-04-01

Research is reported for the combined groups consisting of the Accelerator Division and the Magnetic Fusion Energy Group. Major topics reported include accelerator operations, magnetic fusion energy, and advanced accelerator development. (GHT)

Pulsed-focusing recirculating linacs for muon acceleration

Energy Technology Data Exchange (ETDEWEB)

Johnson, Rolland [Muons, Inc., Batavia, IL (United States)

2014-12-31

Since the muon has a short lifetime, fast acceleration is essential for high-energy applications such as muon colliders, Higgs factories, or neutrino factories. The best one can do is to make a linear accelerator with the highest possible accelerating gradient to make the accelerating time as short as possible. However, the cost of such a single linear accelerator is prohibitively large due to expensive power sources, cavities, tunnels, and related infrastructure. As was demonstrated in the Thomas Jefferson Accelerator Facility (Jefferson Lab) Continuous Electron Beam Accelerator Facility (CEBAF), an elegant solution to reduce cost is to use magnetic return arcs to recirculate the beam through the accelerating RF cavities many times, where they gain energy on each pass. In such a Recirculating Linear Accelerator (RLA), the magnetic focusing strength diminishes as the beam energy increases in a conventional linac that has constant strength quadrupoles. After some number of passes the focusing strength is insufficient to keep the beam from going unstable and being lost. In this project, the use of fast pulsed quadrupoles in the linac sections was considered for stronger focusing as a function of time to allow more successive passes of a muon beam in a recirculating linear accelerator. In one simulation, it was shown that the number of passes could be increased from 8 to 12 using pulsed magnet designs that have been developed and tested. This could reduce the cost of linac sections of a muon RLA by 8/12, where more improvement is still possible. The expense of a greater number of passes and corresponding number of return arcs was also addressed in this project by exploring the use of ramped or FFAG-style magnets in the return arcs. A better solution, invented in this project, is to use combined-function dipole-quadrupole magnets to simultaneously transport two beams of different energies through one magnet string to reduce costs of return arcs by almost a factor of

Performance of magnetically-injected-plasma opening switches on the particle beam fusion accelerator 2

International Nuclear Information System (INIS)

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

1990-01-01

Plasma opening switch (POS) experiments have been performed on the PBFA II ion beam accelerator to develop a switch which will provide voltage and power gain to an applied-B lithium ion diode. These experiments have successfully coupled power to electron and ion beam diodes using a Magnetically-Injected-Plasma (MIP) POS. Carbon plasma with electron densities of 1 x 10 12 to 2 x 10 13 /cm 3 have been injected from the anode into the 8 cm gap of the 20-ohm Magnetically-Insulated-Transmission Line (MITL) of PBFA II along a B r,z magnetic field. The MIP switch uses the inertia of the plasma to keep the switch closed and the magnetic pressure of B θ from the conduction current to open the switch. The configuration of the injecting magnetic field and the plasma source has a significant effect on the efficiency of coupling power to high impedance loads. Plasma near the center of the injecting magnetic field limits the opening impedance of the switch and subsequently the power delivered to the load. The axial location of the switch with respect to the load has also been identified as a critical parameter in increasing the coupling efficiency. A length of 10 to 20 cm of MITL between the POS and the load has increased the power delivered to the load. Data on switch performance with high impedance loads and factors which improved performance are discussed

Permanent magnet based dipole magnets for next generation light sources

Directory of Open Access Journals (Sweden)

Takahiro Watanabe

2017-07-01

Full Text Available We have developed permanent magnet based dipole magnets for the next generation light sources. Permanent magnets are advantageous over electromagnets in that they consume less power, are physically more compact, and there is a less risk of power supply failure. However, experience with electromagnets and permanent magnets in the field of accelerators shows that there are still challenges to replacing main magnets of accelerators for light sources with permanent magnets. These include the adjustability of the magnetic field, the temperature dependence of permanent magnets, and the issue of demagnetization. In this paper, we present a design for magnets for future light sources, supported by experimental and numerical results.

Experimental studies on the thermal properties of fast pulsed superconducting accelerator magnets; Experimentelle Untersuchungen thermischer Eigenschaften schnell gepulster supraleitender Beschleunigermagnete

Energy Technology Data Exchange (ETDEWEB)

Bleile, Alexander

2016-01-06

The new Facility for Antiproton and Ion Research FAIR is being constructed at the GSI research center in Darmstadt (Germany). This wordwide unique accelerator facility will provide beams of ions and antiprotons at high intensities and high energies for the fundamental research in nuclear, atomic and plasma physics as well as for applied science. The superconducting synchrotron SIS100 with a magnetic rigidity of 100 T/m, the core component of the FAIR facility will provide primary ion beams of all types from hydrogen up to uranium. One of the key technical systems of a new synchrotron are fast ramped electromagnets for the generation of fast ramped magnetic fields for deflecting and focusing of the ion beams. To reduce the energy consumption and to keep the operating costs of the synchrotron as low as possible superconducting magnet technology is applied in the SIS100. Superconducting magnets have been developed at GSI within the scope of the FAIR project. Although the superconducting magnet technology promises high cost saving, the power consumption of the fast ramped superconducting magnets can't be completely neglected. The pulsed operation generates dynamic losses in the iron yokes as well as in the superconducting coils of the magnets. A forced two-phase helium flow provides effective cooling for supercounducting magnets exposed to a continous relative high heat flow. The subject of this PhD thesis is experimental investigations and analysis of the dynamic power losses in fast ramped superconducting magnets and their dependencies on the operation cycles of the synchrotron. This research was conducted on the the first series SIS100 dipole magnet. Based on the experimentally defined dynamic heat loads and helium mass flow rates in the dipole magnet the heat loads and helium consumption for all other types of superconducting magnet modules of the SIS100 have been estimated. These results are essential for the development of the cooling system for the the

Magnets becoming more super

Energy Technology Data Exchange (ETDEWEB)

Anon.

1986-09-15

With the twenty year struggle to master superconducting magnets for accelerators behind them, magnet specialists are now very confident of their ability to use superconductivity in accelerator design. Superconductor performance has improved considerably in the past few years and we may well see the number of these magnets escalate from the present figure of about a thousand to over fifteen thousand within the next decade. This confidence emerged clearly from a recent Workshop at Brookhaven, organized by the Panel on Superconducting Magnets and Cryogenics set up by the International Committee on Future Accelerators (ICFA)

Induction accelerators for the phase rotator system

International Nuclear Information System (INIS)

Reginato, Lou; Yu, Simon; Vanecek, Dave

2001-01-01

The principle of magnetic induction has been applied to the acceleration of high current beams in betatrons and a variety of induction accelerators. The linear induction accelerator (LIA) consists of a simple nonresonant structure where the drive voltage is applied to an axially symmetric gap that encloses a toroidal ferromagnetic material. The change in flux in the magnetic core induces an axial electric field that provides particle acceleration. This simple nonresonant (low Q) structure acts as a single turn transformer that can accelerate from hundreds of amperes to tens of kiloamperes, basically only limited by the drive impedance. The LIA is typically a low gradient structure that can provide acceleration fields of varying shapes and time durations from tens of nanoseconds to several microseconds. The efficiency of the LIA depends on the beam current and can exceed 50% if the beam current exceeds the magnetization current required by the ferromagnetic material. The acceleration voltage available is simply given by the expression V=A dB/dt. Hence, for a given cross section of material, the beam pulse duration influences the energy gain. Furthermore, a premium is put on minimizing the diameter, which impacts the total weight or cost of the magnetic material. The diameter doubly impacts the cost of the LIA since the power (cost) to drive the cores is proportional to the volume as well. The waveform requirements during the beam pulse makes it necessary to make provisions in the pulsing system to maintain the desired dB/dt during the useful part of the acceleration cycle. This is typically done two ways, by using the final stage of the pulse forming network (PFN) and by the pulse compensation network usually in close proximity of the acceleration cell. The choice of magnetic materials will be made by testing various materials both ferromagnetic and ferrimagnetic. These materials will include the nickel-iron, silicon steel amorphous and various types of ferrites not

Vol. 34 - Optimization of quench protection heater performance in high-field accelerator magnets through computational and experimental analysis

CERN Document Server

Salmi, Tiina

2016-01-01

Superconducting accelerator magnets with increasingly hi gh magnetic fields are being designed to improve the performance of the Large Hadron Collider (LHC) at CERN. One of the technical challenges is the magnet quench p rotection, i.e., preventing damage in the case of an unexpected loss of superc onductivity and the heat generation related to that. Traditionally this is d one by disconnecting the magnet current supply and using so-called protection he aters. The heaters suppress the superconducting state across a large fraction of the winding thus leading to a uniform dissipation of the stored energy. Preli minary studies suggested that the high-field Nb 3 Sn magnets under development for the LHC luminosity upgrade (HiLumi) could not be reliably protected using the existing heaters. In this thesis work I analyzed in detail the present state-of-the-art protection heater technology, aiming to optimize its perfo rmance and evaluate the prospects in high-field magnet protection. The heater efficiency analyses ...

Acceleration of compact torus plasma rings in a coaxial rail-gun

International Nuclear Information System (INIS)

Hartman, C.W.; Hammer, J.H.; Eddleman, J.

1986-01-01

They discuss here theoretical studies of magnetic acceleration of Compact Torus plasma rings in a coaxial, rail-gun accelerator. The rings are formed using a magnetized coaxial plasma gun and are accelerated by injection of B/sub Theta/ flux from an accelerator bank. After acceleration, the rings enter a focusing cone where the ring is decelerated and reduced in radius. As the ring radius decreases, the ring magnetic energy increases until it equals the entering kinetic energy and the ring stagnates. Scaling laws and numerical calculations of acceleration using a O-D numerical code are presented. 2-D, MHD simulations are shown which demonstrate ring formation, acceleration, and focusing. Finally, 3-D calculations are discussed which determine the ideal MHD stability of the accelerated ring

Acceleration of compact torus plasma rings in a coaxial rail-gun

International Nuclear Information System (INIS)

Hartman, C.W.; Hammer, J.H.; Eddleman, J.

1985-01-01

We discuss here theoretical studies of magnetic acceleration of Compact Torus plasma rings in a coaxial, rail-gun accelerator. The rings are formed using a magnetized coaxial plasma gun and are accelerated by injection of B/sub theta/ flux from an accelerator bank. After acceleration, the rings enter a focusing cone where the ring is decelerated and reduced in radius. As the ring radius decreases, the ring magnetic energy increases until it equals the entering kinetic energy and the ring stagnates. Scaling laws and numerical calculations of acceleration using a O-D numerical code are presented. 2-D, MHD simulations are shown which demonstrate ring formation, acceleration, and focusing. Finally, 3-D calculations are discussed which determine the ideal MHD stability of the accelerated ring

Plasma-focused cyclic accelerators

International Nuclear Information System (INIS)

Mondelli, A.A.; Chernin, D.P.

1985-01-01

The use of ambient plasma to neutralize the transverse forces of an intense particle beam has been known for many years. Most recently, the so-called ion-focused regime (IFR) for beam propagation has been used as a means of focusing intense electron beams in linear accelerators and suggested for injecting an electron beam across magnetic field lines into a high-current cyclic accelerator. One technique for generating the required background plasma for IFR propagation is to use a laser to ionize ambient gas in the accelerator chamber. For cyclic accelerators a technique is required for carrying the plasma channel and the beam around a bend. Multiple laser-generated channels with dipole magnetic fields to switch the beam from one channel to the next have been tested at Sandia. This paper discusses an alternative means of plasma production for IFR, viz. by using rf breakdown. For this approach the accelerator chamber acts as a waveguide. With a suitable driving frequency, a waveguide mode can be driven which has its peak field intensity on the axis with negligible fields at the chamber walls. The plasma production and hence the beam propagation is thereby isolated from the walls. This technique is not limited to toroidal accelerators. It may be applied to any accelerator or recirculator geometry as well as for beam steering and for injection or extraction of beams in closed accelerator configurations

Accelerator Technology Division annual report, FY 1989

International Nuclear Information System (INIS)

1990-06-01

This paper discusses: accelerator physics and special projects; experiments and injectors; magnetic optics and beam diagnostics; accelerator design and engineering; radio-frequency technology; accelerator theory and simulation; free-electron laser technology; accelerator controls and automation; and high power microwave sources and effects

Racetrack linear accelerators

International Nuclear Information System (INIS)

Rowe, C.H.; Wilton, M.S. de.

1979-01-01

An improved recirculating electron beam linear accelerator of the racetrack type is described. The system comprises a beam path of four straight legs with four Pretzel bending magnets at the end of each leg to direct the beam into the next leg of the beam path. At least one of the beam path legs includes a linear accelerator. (UK)

Strong ion accelerating by collisionless magnetosonic shock wave propagating perpendicular to a magnetic field

International Nuclear Information System (INIS)

Ohsawa, Yukiharu.

1984-12-01

A 2-1/2 dimensional fully relativistic, fully electromagnetic particle code is used to study a time evolution of nonlinear magnetosonic pulse propagating in the direction perpendicular to a magnetic field. The pulse is excited by an instantaneous piston acceleration, and evolves totally self-consistently. Large amplitude pulse traps some ions and accelerates them parallel to the wave front. They are detrapped when their velocities become of the order of the sum of the ExB drift velocity and the wave phase velocity, where E is the electric field in the direction of wave propagation. The pulse develops into a quasi-shock wave in a collisionless plasma by a dissipation due to the resonant ion acceleration. Simple nonlinear wave theory for a cold plasma well describes the shock properties observed in the simulation except for the effects of resonant ions. In particular, magnitude of an electric potential across the shock region is derived analytically and is found to be in good agreement with our simulations. The potential jump is proportional to B 2 , and hence the ExB drift velocity of the trapped ions is proportional to B. (author)

Injection and extraction techniques in circular accelerators

International Nuclear Information System (INIS)

Tang Jingyu

2008-01-01

Injection and extraction are usually the key systems in circular accelerators. They play important roles in transferring the beam from one stage acceleration to the other or to experimental stations. It is also in the injection and extraction regions where beam losses happen mostly. Due to the tight space and to reduce the perturbation to the circulating orbit, the devices are usually designed to meet special requirements such as compactness, small stray field, fast rise time or fall time, etc. Usual injection and extraction devices include septum magnets, kicker magnets, electrostatic deflectors, slow bump magnets and strippers. In spite of different accelerators and specification for the injection and extraction devices, many techniques are shared in the design and manufacturing. This paper gives a general review on the techniques employed in the major circular accelerators in China. (authors)

Magnetic, Acceleration Fields and Gyroscope Quaternion (MAGYQ-Based Attitude Estimation with Smartphone Sensors for Indoor Pedestrian Navigation

Directory of Open Access Journals (Sweden)

Valérie Renaudin

2014-12-01

Full Text Available The dependence of proposed pedestrian navigation solutions on a dedicated infrastructure is a limiting factor to the deployment of location based services. Consequently self-contained Pedestrian Dead-Reckoning (PDR approaches are gaining interest for autonomous navigation. Even if the quality of low cost inertial sensors and magnetometers has strongly improved, processing noisy sensor signals combined with high hand dynamics remains a challenge. Estimating accurate attitude angles for achieving long term positioning accuracy is targeted in this work. A new Magnetic, Acceleration fields and GYroscope Quaternion (MAGYQ-based attitude angles estimation filter is proposed and demonstrated with handheld sensors. It benefits from a gyroscope signal modelling in the quaternion set and two new opportunistic updates: magnetic angular rate update (MARU and acceleration gradient update (AGU. MAGYQ filter performances are assessed indoors, outdoors, with dynamic and static motion conditions. The heading error, using only the inertial solution, is found to be less than 10° after 1.5 km walking. The performance is also evaluated in the positioning domain with trajectories computed following a PDR strategy.

Accelerator and fusion research division

International Nuclear Information System (INIS)

1992-12-01

This report contains brief discussions on research topics in the following area: Heavy-Ion Fusion Accelerator Research; Magnetic Fusion Energy; Advanced Light Source; Center for Beam Physics; Superconducting Magnets; and Bevalac Operations

Convectively driven decadal zonal accelerations in Earth's fluid core

Science.gov (United States)

More, Colin; Dumberry, Mathieu

2018-04-01

Azimuthal accelerations of cylindrical surfaces co-axial with the rotation axis have been inferred to exist in Earth's fluid core on the basis of magnetic field observations and changes in the length-of-day. These accelerations have a typical timescale of decades. However, the physical mechanism causing the accelerations is not well understood. Scaling arguments suggest that the leading order torque averaged over cylindrical surfaces should arise from the Lorentz force. Decadal fluctuations in the magnetic field inside the core, driven by convective flows, could then force decadal changes in the Lorentz torque and generate zonal accelerations. We test this hypothesis by constructing a quasi-geostrophic model of magnetoconvection, with thermally driven flows perturbing a steady, imposed background magnetic field. We show that when the Alfvén number in our model is similar to that in Earth's fluid core, temporal fluctuations in the torque balance are dominated by the Lorentz torque, with the latter generating mean zonal accelerations. Our model reproduces both fast, free Alfvén waves and slow, forced accelerations, with ratios of relative strength and relative timescale similar to those inferred for the Earth's core. The temporal changes in the magnetic field which drive the time-varying Lorentz torque are produced by the underlying convective flows, shearing and advecting the magnetic field on a timescale associated with convective eddies. Our results support the hypothesis that temporal changes in the magnetic field deep inside Earth's fluid core drive the observed decadal zonal accelerations of cylindrical surfaces through the Lorentz torque.

Heavy ion accelerators at GSI

International Nuclear Information System (INIS)

Angert, N.

1984-01-01

The status of the Unilac heavy ion linear accelerator at GSI, Darmstadt is given. A schematic overall plan view of the Unilac is shown and its systems are described. List of isotopes and intensities accelerated at the Unilac is presented. The experimental possibilities at GSI should be considerably extended by a heavy ion synchrotron (SIS 18) in combination with an experimental storage ring (ESR). A prototype of the rf-accelerating system of the synchrotron has been built and tested. Prototypes for the quadrupole and dipole magnets for the ring are being constructed. The SIS 18 is desigmed for a maximum magnetic rigidity of 18Tm so that neon can be accelerated to 2 GeV/W and uranium to 1 GeV/u. The design allows also the acceleration of protons up to 4.5 GeV. The ESR permits to storage fully stripped uranium ions up to an energy of approximately R50 MeV/u

Particle acceleration near Halley's comet

International Nuclear Information System (INIS)

Somogyi, Antal

1987-01-01

Vega and Giotto space probes observed energetic ions of cometary origin near Halley's comet. The water molecules evaporating from the cometary nucleus were ionized by the solar UV radiation. These 'standing' ions were accelerated from 1 km/s to a few 1000 km/s. Present paper analyses the possible mechanisms of acceleration based on the data of TUENDE detector (constructed by CRIP, Hungary) working on board of Vega probes. The basic mechanism is the ExB Lorentz acceleration by interplanetary magnetic field and electric field induced by magnetic field frozen into solar wind plasma. It is followed by an acceleration caused by the adiabatic compression of the plasma at shock wave front. These processes can not explain the observed velocity of ions. It is shown that the second order Fermi acceleration which dissipates the ion distribution in the velocity space can lead to the observed velocities. The circumstances required to the occurrence of this process are present at the cometary environment. (D.G.) 2 figs

Physics and measurements of magnetic materials

CERN Document Server

Sgobba, S

2010-01-01

Magnetic materials, both hard and soft, are used extensively in several components of particle accelerators. Magnetically soft iron-nickel alloys are used as shields for the vacuum chambers of accelerator injection and extraction septa; Fe-based material is widely employed for cores of accelerator and experiment magnets; soft spinel ferrites are used in collimators to damp trapped modes; innovative materials such as amorphous or nanocrystalline core materials are envisaged in transformers for high-frequency polyphase resonant convertors for application to the International Linear Collider (ILC). In the field of fusion, for induction cores of the linac of heavy-ion inertial fusion energy accelerators, based on induction accelerators requiring some 107 kg of magnetic materials, nanocrystalline materials would show the best performance in terms of core losses for magnetization rates as high as 105 T/s to 107 T/s. After a review of the magnetic properties of materials and the different types of magnetic behaviour...

PONDEROMOTIVE ACCELERATION IN CORONAL LOOPS

International Nuclear Information System (INIS)

Dahlburg, R. B.; Obenschain, K.; Laming, J. M.; Taylor, B. D.

2016-01-01

Ponderomotive acceleration has been asserted to be a cause of the first ionization potential (FIP) effect, the well-known enhancement in abundance by a factor of 3–4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a “by-product” of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of coronal loops with an axial magnetic field from 0.005 to 0.02 T and lengths from 25,000 to 75,000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets, which act to heat the loop. As a consequence of coronal magnetic reconnection, small-scale, high-speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.