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Physical Review Special Topics - Accelerators and Beams
Physical Review Special Topics - Accelerators and Beams, is a peer reviewed, purely electronic journal, distributed without charge to readers and funded by contributions from national laboratories. It covers the full range of accelerator science and technology: subsystem and component technologies, beam dynamics; accelerator applications; and design, operation, and improvement of accelerators used in science and industry. This includes accelerators for high energy and nuclear physics, synchrotron radiation production, spallation neutron sources, medical therapy, and intense beam applications. More...
October 13, 2009 The first update to REVTeX since 2001 is now available. REVTeX 4.1 includes bug fixes, improved functionality, and support for a wider range of journals, including those of the American Institute of Physics (AIP). REVTEX 4.1 was developed jointly by APS, AIP, and Arthur Ogawa. Additional work was done by Patrick Daly to incorporate our suggested improvements into his natbib package to address many new features concerning bibliographies. For more information, please visit http://authors.aps.org/revtex4/. More News/Announcements
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April 27, 2009 Physical Review Special Topics - Accelerators and Beams is offering a Special Edition for the 2009 Particle Accelerator Conference that will be held May 4-8, 2009 in Vancouver, Canada. This Special Edition offers the opportunity to expand upon original research presented at PAC09 in a peer-reviewed journal. More Information.... More News/Announcements
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March 13, 2009 Starting March 2009, the PRST-AB web site features selected "cover"
images extracted from recently published papers. Selections are based on
aesthetics; in making our selection we look for attractive and
interesting graphics. If a choice must be made between several promising
contenders, we will also consider the contents both of the image and of
its associated paper. The image will be identified by the title of the
paper; there will also be a link to the article. The image itself may be
slightly modified. Kaleidoscope images, one per issue, rotate
on the main web site and may be browsed in an archive. The PRST-AB image archive already
contains some interesting PRST-AB images which have caught our attention
during the last couple of months. Read More | More News/Announcements
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December 1, 2008
We deeply regret the passing of our friend and colleague, Robert H. Siemann, on September 16, 2008. He was the founding Editor of Physical Review Special Topics - Accelerators and Beams. We are now publishing a dedicated section of essays in memory of Bob Siemann. The essays are from different angles of Bob’s remarkable career and life. We hope these anecdotes and educational remarks are a benefit to our readers.
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October 7, 2008 We deeply regret the passing of our friend and colleague, Robert H. Siemann, on September 16, 2008. He was the Editor of Physical Review Special Topics - Accelerators and Beams from its founding in 1998 through 2007, when he stepped down for health reasons—not without ensuring a smooth and efficient transition to his successors.
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May 22, 2008 Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.
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May 5, 2008 On 14 May 2008, Physical Review Special Topics - Accelerators and Beams is celebrating its 10th anniversary. PRST-AB was founded by Robert Siemann and the APS in 1998 to provide the accelerator community with its own journal, covering all aspects of accelerators from fundamental physics to technology.
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January 10, 2008 Physical Review Special Topics - Accelerators and Beams is offering a Special Edition for the 11th European Particle Accelerator Conference that will be held June 23-27, 2008 in Genoa, Italy. This Special Edition offers the opportunity to expand upon original research presented at EPAC 2008 in a peer-reviewed journal. APS would like to acknowledge the financial contribution made by EPAC'08 in support of the journal. More Information.... More News/Announcements
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Affilitated Professional Groups
The Division of Physics of Beams of the American Physical Society and the European Physical Society Accelerators Group serve as Affiliated Professional Groups for Physical Review Topics Special Accelerators and Beams. Together they share the responsibility for the health and vitality of the journal by providing advice and encouraging scholarly publication in accelerator science and technology.
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Because of the generous support by sponsors, this journal is provided without charge to either authors or readers; no subscription is necessary. For more information about becoming a sponsor, please contact the Editor, Frank Zimmermann.
Physical Review Special Topics — Accelerators and Beams (PRST-AB) publishes Conference Editions, Special Editions and Special Collections. The Special and Conference Editions are associated with accelerator conferences, and the Special Collections bring together the work of groups and collaborations.
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Review articles in Physical Review Special Topics - Accelerators and Beams examine active areas of research in a form that is useful to both practitioners and people entering the field. Progress on the topic is analyzed critically, the most successful methods identified, and areas for future development suggested.
Review Articles
Roger M. Jones
The transverse wakefield excited by multiple bunches in ultrarelativistic charged particle beams in a linear collider must be adequately damped in order to preserve the luminosity of the colliding beams and to prevent a beam breakup instability developing. A review of the means of achieving this wak...
[Phys. Rev. ST Accel. Beams 12, 104801
] Published Thu Oct 8, 2009
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Edgar Mahner
During high-intensity heavy-ion operation of several particle accelerators worldwide, large dynamic pressure rises of orders of magnitude were caused by lost beam ions that impacted under grazing angle onto the vacuum chamber walls. This ion-induced desorption, observed, for example, at CERN, GSI, a...
[Phys. Rev. ST Accel. Beams 11, 104801
] Published Wed Oct 29, 2008
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Ute Linz and Jose Alonso
After many years on the periphery of cancer therapy, the successes of proton and ion beams in tumor therapy are gradually receiving a higher degree of recognition. The considerable construction and acquisition costs are usually invoked to explain the slow market penetration of this favorable treatme...
[Phys. Rev. ST Accel. Beams 10, 094801
] Published Mon Sep 24, 2007
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Zhirong Huang and Kwang-Je Kim
High-gain free-electron lasers (FELs) are being developed as extremely bright sources for a next-generation x-ray facility. In this paper, we review the basic theory of the start-up, the exponential growth, and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emiss...
[Phys. Rev. ST Accel. Beams 10, 034801
] Published Mon Mar 12, 2007
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F. Zimmermann
Electrons generated and accumulated inside the beam-pipe form an “electron cloud” that interacts with a charged particle beam. If the number of electrons is sizable, this beam-cloud interaction can give rise to a two-stream instability, resulting in beam loss or emittance growth. The instability...
[Phys. Rev. ST Accel. Beams 7, 124801
] Published Tue Dec 21, 2004
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Ronald C. Davidson, Igor Kaganovich, Hong Qin, Edward A. Startsev, Dale R. Welch, David V. Rose, and Han S. Uhm
This paper presents a survey of the present theoretical understanding of collective processes and beam-plasma interactions affecting intense heavy ion beam propagation in heavy ion fusion systems. In the acceleration and beam transport regions, the topics covered include discussion of the conditions...
[Phys. Rev. ST Accel. Beams 7, 114801
] Published Wed Nov 17, 2004
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Ian D. Smith
Induction voltage adders (IVA) and induction accelerators of various types are described and their principles and advantages are discussed. The designs and technologies used in the various subsections and components of high-current IVAs are described. Some features of the pulse power that drives IVA...
[Phys. Rev. ST Accel. Beams 7, 064801
] Published Mon Jun 14, 2004
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Steven M. Lund and Boris Bukh
The transverse evolution of the envelope of an intense, unbunched ion beam in a linear transport channel can be modeled for the approximation of linear self-fields by the Kapchinskij-Vladimirskij (KV) envelope equations. Here we employ the KV envelope equations to analyze the linear stability proper...
[Phys. Rev. ST Accel. Beams 7, 024801
] Published Wed Feb 11, 2004
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Luca Giannessi
The high brightness electron beam required by a short wavelength self-amplified spontaneous emission free-electron laser (FEL) may be reached only with an accurate design of the beam dynamics from the generation in the rf injector up to the undulator. The beam dynamics is affected by strong self-con...
[Phys. Rev. ST Accel. Beams 6, 114802
] Published Mon Nov 10, 2003
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L. Nadolski and J. Laskar
Frequency map analysis [J. Laskar, Icarus 88, 266 (1990)] is used here to analyze the transverse dynamics of four third generation synchrotron light sources: the ALS, the ESRF, the SOLEIL project, and Super-ACO. Time variations of the betatron tunes give additional information for the global dynamic...
[Phys. Rev. ST Accel. Beams 6, 114801
] Published Tue Nov 4, 2003
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Recently published articles in Physical Review Special Topics - Accelerators and Beams. See the current issue for more.
Pulsed-Power Accelerators, Technology, and Dynamics
Eduardo M. Waisman and M. E. Cuneo
We extend the variational calculus technique for inductance minimization of constant gap axisymmetric transmission lines (TL), introduced by Hurricane [J. Appl. Phys. 95, 4503 (2004)], to the case in which the anode-cathode gap is a linear function of the midgap radius. The full analytic optimal mid...
[Phys. Rev. ST Accel. Beams 12, 090401
] Published Wed Sep 30, 2009
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Synchrotron Radiation and Free-Electron Lasers
J. Qiang, R. D. Ryne, M. Venturini, A. A. Zholents, and I. V. Pogorelov
In this paper we report on large-scale high resolution simulations of beam dynamics in electron linacs for the next-generation x-ray free electron lasers (FELs). We describe key features of a parallel macroparticle simulation code including three-dimensional (3D) space-charge effects, short-range st...
[Phys. Rev. ST Accel. Beams 12, 100702
] Published Wed Oct 14, 2009
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Vitaliy A. Goryashko, Kostyantyn Ilyenko, and Anatoliy Opanasenko
We study the operation regime of a hybrid planar free-electron maser (FEM) amplifier near the magnetoresonant value of the uniform longitudinal (guide) magnetic field. Using analytical expressions for individual test electron trajectories and normal frequencies of their three-dimensional oscillation...
[Phys. Rev. ST Accel. Beams 12, 100701
] Published Wed Oct 7, 2009
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High-Energy Accelerators and Colliders
Yi-Peng Sun (孙一鹏), Ralph Assmann, Javier Barranco, Rogelio Tomás, Thomas Weiler, Frank Zimmermann, Rama Calaga, and Akio Morita (森田 昭夫)
Modern colliders bring into collision a large number of bunches to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effectiv...
[Phys. Rev. ST Accel. Beams 12, 101002
] Published Wed Oct 14, 2009
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G. S. Nusinovich, D. Kashyn, and T. M. Antonsen
High-gradient accelerating structures should operate reliably for a long time. Therefore studies of various processes which may lead to disruption of such an operation are so important. In the present paper, the dissipation of rf electromagnetic energy in metallic microparticles is analyzed accounti...
[Phys. Rev. ST Accel. Beams 12, 101001
] Published Tue Oct 13, 2009
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Y. Ohnishi, K. Ohmi, H. Koiso, M. Masuzawa, A. Morita, K. Mori, K. Oide, Y. Seimiya, and D. Zhou
We have measured and corrected chromatic X-Y coupling at an interaction point to improve the luminosity of KEKB. We have measured the beam position of betatron oscillations induced by the kicker using turn-by-turn beam position monitors. A phase space structure reconstructed by the beam position pro...
[Phys. Rev. ST Accel. Beams 12, 091002
] Published Mon Sep 28, 2009
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New Acceleration Techniques
T. Plettner, R. L. Byer, C. McGuinness, and P. Hommelhoff
We propose a dielectric photonic structure for ultrafast deflection and focusing of relativistic charged particle beams. The structure is designed to transform a free-space laser beam into a deflection force that acts on the free particles with the same optical phase over a distance of travel that i...
[Phys. Rev. ST Accel. Beams 12, 101302
] Published Mon Oct 26, 2009
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S. Becker, P. B. Hilz, F. Grüner, and D. Habs
Laser-plasma accelerators are expected to deliver electron bunches with high space charge fields. Several recent publications have addressed the impact of space charge effects on such bunches after the extraction into vacuum. Artifacts due to the approximation of retardation effects are addressed, w...
[Phys. Rev. ST Accel. Beams 12, 101301
] Published Thu Oct 22, 2009
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Radio Frequency Calculations and Technology
A. Grudiev, S. Calatroni, and W. Wuensch
A new local field quantity is presented which gives the high gradient performance limit of accelerating structures due to vacuum rf breakdown. The new field quantity, a modified Poynting vector Sc, is derived from a model of the breakdown trigger in which field emission currents from potential break...
[Phys. Rev. ST Accel. Beams 12, 102001
] Published Mon Oct 26, 2009
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A. Descoeudres, Y. Levinsen, S. Calatroni, M. Taborelli, and W. Wuensch
Breakdowns occurring in rf accelerating structures will limit the ultimate performance of future linear colliders such as the Compact Linear Collider (CLIC). Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN to better understand the vacuum bre...
[Phys. Rev. ST Accel. Beams 12, 092001
] Published Tue Sep 29, 2009
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Magnet Calculations and Technology
Nicholas Sammut, Luca Bottura, Guy Deferne, and Walter Venturini Delsolaro
The Large Hadron Collider (LHC) at CERN is equipped with a feed-forward control system known as the field description for the LHC (FiDeL) which is designed to predict the magnetic field and its multipoles, hence reducing the burden on beam based feedback. FiDeL consists of a physical and empirical p...
[Phys. Rev. ST Accel. Beams 12, 102401
] Published Tue Oct 27, 2009
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Beam Control, Diagnostics, and Feedback
Shaoheng Wang, J. C. Dooling, K. C. Harkay, R. L. Kustom, and G. E. McMichael
The rapid cycling synchrotron of the intense pulsed neutron source at Argonne National Laboratory normally operates at an average beam current of 14 to 15 μA, accelerating protons from 50 to 450 MeV 30 times per second. The beam current is limited by a single-bunch vertical instability that o...
[Phys. Rev. ST Accel. Beams 12, 102802
] Published Tue Oct 27, 2009
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S. Becker, M. Bussmann, S. Raith, M. Fuchs, R. Weingartner, P. Kunz, W. Lauth, U. Schramm, M. El Ghazaly, F. Grüner, H. Backe, and D. Habs
The application of quadrupole devices with high field gradients and small apertures requires precise control over higher order multipole field components. We present a new scheme for performance control and tuning, which allows the illumination of most of the quadrupole device aperture because of th...
[Phys. Rev. ST Accel. Beams 12, 102801
] Published Mon Oct 19, 2009
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Other Accelerator Subsystems and Technologies
O. A. Ivanov, A. A. Vikharev, A. M. Gorbachev, V. A. Isaev, M. A. Lobaev, A. L. Vikharev, S. V. Kuzikov, J. L. Hirshfield, and M. A. LaPointe
Results of numerical calculations and experimental investigations of an active Ka-band microwave pulse compressor are presented. The compressor is based on a running-wave, three-mirror, quasioptical resonator utilizing a diffraction grating whose channels embody plasma discharge tubes that constitut...
[Phys. Rev. ST Accel. Beams 12, 093501
] Published Fri Sep 11, 2009
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Single-Particle Dynamics
Stephen G. Peggs and Valentina Previtali
The grazing function g is introduced—a synchrobetatron optical quantity that is analogous (and closely connected) to the Twiss and dispersion functions β, α, η, and η′. It parametrizes the rate of change of total angle with respect to synchrotron amplitude for grazing particles, which just t...
[Phys. Rev. ST Accel. Beams 12, 114001
] Published Mon Nov 2, 2009
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Low-Energy, Multiple-Particle Dynamics
A. R. Rossi, A. Bacci, L. Serafini, C. Maroli, and V. Petrillo
A form is given of the retarded electric field and magnetic induction generated by the motion of a charged particle that expresses these fields as integrals of the retarded charge density only, with kernels depending on the charge velocity and acceleration fields. In the case of a single pointlike c...
[Phys. Rev. ST Accel. Beams 12, 104202
] Published Tue Oct 20, 2009
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Alexander W. Chao
Gravitational instability of the distribution of stars in a galaxy is a well-known phenomenon in astrophysics. This report is an attempt to analyze this phenomenon by applying standard tools developed in accelerator physics. It is found that a nonrotating galaxy would become unstable if its size exc...
[Phys. Rev. ST Accel. Beams 12, 104201
] Published Wed Oct 7, 2009
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Relativistic, Multiple-Particle Dynamics
G. V. Stupakov and I. A. Kotelnikov
We study an impedance due to coherent synchrotron radiation (CSR) generated by a short bunch of charged particles passing through a dipole magnet of finite length in a vacuum chamber of a given cross section. In our method we decompose the electromagnetic field of the beam over the eigenmodes of the...
[Phys. Rev. ST Accel. Beams 12, 104401
] Published Fri Oct 30, 2009
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Tomonori Agoh
We study longitudinal fields of coherent synchrotron radiation in a perfectly conducting rectangular pipe. Our theory is based on the paraxial approximation of electromagnetic waves in the frequency domain. The longitudinal impedance of coherent radiation is obtained. By considering the pole structu...
[Phys. Rev. ST Accel. Beams 12, 094402
] Published Wed Sep 23, 2009
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Yoshihiro Shobuda, Yong Ho Chin, and Koji Takata
We have developed a theory to calculate both longitudinal and transverse impedances of a resistive short (typically shorter than the chamber radius) insert with cylindrical symmetry, sandwiched by perfectly conductive chambers on both sides. It is found that unless the insert becomes extremely thin ...
[Phys. Rev. ST Accel. Beams 12, 094401
] Published Thu Sep 17, 2009
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Review Articles
Roger M. Jones
The transverse wakefield excited by multiple bunches in ultrarelativistic charged particle beams in a linear collider must be adequately damped in order to preserve the luminosity of the colliding beams and to prevent a beam breakup instability developing. A review of the means of achieving this wak...
[Phys. Rev. ST Accel. Beams 12, 104801
] Published Thu Oct 8, 2009
Read article
Comments and Replies
S. R. Mane
Bai and Roser {Phys. Rev. ST Accel. Beams 11, 091001 (2008) [Phys. Rev. ST Accel. Beams 12, 019901(E) (2009)]} have published an idea for a design of a spin flipper, consisting of two radial field rf dipoles with correlated phases, to operate with full strength Siberian Snakes, at a spin tune of 1 ...
[Phys. Rev. ST Accel. Beams 12, 099001
] Published Tue Sep 15, 2009
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Errata
A. Burov
[Phys. Rev. ST Accel. Beams 12, 109901
] Published Mon Oct 12, 2009
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G. Weber, C. Omet, R. D. DuBois, O. de Lucio, Th. Stöhlker, C. Brandau, A. Gumberidze, S. Hagmann, S. Hess, C. Kozhuharov, R. Reuschl, P. Spiller, U. Spillmann, M. Steck, M. Thomason, and S. Trotsenko
[Phys. Rev. ST Accel. Beams 12, 099901
] Published Wed Sep 23, 2009
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Papers recently accepted for publication in Physical Review Special Topics - Accelerators and Beams (view more).
Pulsed-Power Accelerators, Technology, and Dynamics
Effect of a transition section between the Blumlein line and a load on the output voltage of gigawatt intense electron beam accelerators
XinBing Cheng, JinLiang Liu, Yu Zhang, BaoLiang Qian and JiaHuai Feng
The flat voltage of main pulse on the load of intense electron-beam accelerators (IEBA) is one of the important factors which affect the quality and characteristic of the output beam current of IEBA. In this paper, the effect of transition section between the Blumlein pulse forming line (BPFL) and load on the output voltage of IEBA is analyzed in theory. Based on the telegraph equations of the BPFL, a formula which is used to calculate the output voltage of IEBA is obtained, and the factor which affects the output voltage is analyzed. It is found from the theoretical analysis that the wave impedance and transmission time of the transition section influence considerably the fluctuation of the main pulse voltage waveform at the load. In order to get a well-shaped square wave form at load and to improve the electron beam quality of such an accelerator, there should be a proper wave impedance of the transition section, and the transmission time of the transition section should be designed as short as possible. At last, some experiments are performed on IEBA, and the experimental results shows reasonable agreement with theoretical analysis.
Accepted Thu Oct 22, 2009
55 TW magnetically insulated transmission line system: Design, performance, and simulations
W. A. Stygar, P. A. Corcoran, H. C. Ives, R. B. Spielman, J. W. Douglas, B. A. Whitney, M. A. Mostrom, T. C. Wagoner, C. S. Speas, T. L. Gilliland, G. A. Allshouse, R. E. Clark, G. L. Donovan, T. P. Hughes, D. R. Humphreys, D. M. Jaramillo, M. F. Johnson, J. W. Kellogg, R. J. Leeper, F. W. Long, T. H. Martin, T. D. Mulville, M. D. Pelock and B. P. Peyton
We describe herein a system of self magnetically insulated vacuum transmission lines (MITLs) that operated successfully at 20 MA, 3 MV, and 50 TW. The system delivered the electromagnetic power pulse generated by the Z accelerator to a physics-package load on over 1700 Z shots. The system included four levels that were electrically in parallel. Each level consisted of a water flare, vacuum-insulator stack, vacuum flare, and 1.3-mradius conical outer MITL. The outputs of the four outer MITLs were connected in parallel by a 7.6-cm-radius 12-post double-post-hole vacuum convolute. The convolute added the currents of the four outer MITLs, and delivered the combined current to a single 6-cm-long inner MITL. The inner MITL delivered the current to the load. The total initial inductance of the stack-MITL system was 11 nH. A 300-element transmission-line circuit model of the system has been developed using the TL code. The model accounts for the following: (i) impedance and electrical length of each of the 300 circuit elements, (ii) electron emission from MITL-cathode surfaces wherever the electric field has previously exceeded a constant threshold value, (iii) Child-Langmuir electron loss in the MITLs before magnetic insulation is established, (iv) MITL-flow-electron loss after insulation, assuming either collisionless or collisional electron flow, (v) MITL-gap closure, (vi) energy loss to MITL conductors operated at high lineal current densities, (vii) time-dependent self-consistent inductance of an imploding z-pinch load, and (viii) load resistance, which is assumed to be constant. Simulations performed with the TL model demonstrate that the nominal geometric outer-MITL-system impedance that optimizes overall performance is a factor of ~3.3 greater than the convolute-load impedance, which is consistent with an analytic model 3 of an idealized MITL-load system. Power-flow measurements demonstrate that, until peak current, the Z stack-MITL system performed as expected. TL calculations of the peak electromagnetic power at the stack, stack energy, stack voltage, outer-MITL current, and load current, as well as the pinch-implosion time, agree with measurements to within 5%. After peak current, TL calculations and measurements diverge, which appears to be due in part to the idealized pinch model assumed by TL. The results presented suggest that the design of the Z-accelerator's stack-MITL system, and the TL model, can serve as starting points for the design of stack-MITL systems of future superpower accelerators.
Accepted Mon Sep 28, 2009
Synchrotron Radiation, Free-Electron Lasers, and Coherent Radiation Sources
Observation of coherent Smith Purcell radiation using an initially continuous flat beam
J. Gardelle, L. Courtois, P. Modin and J. T. Donohue
A few years ago a new theory for producing coherent Smith-Purcell (SP) radiation from an initially continuous beam was proposed. This experiment confirms that two-dimensional theory. The beam was typically 10 cm wide, a few mm thick, with a peak current of 200 A and beam energy of 85 keV. The 10 cm-wide grating had twenty 2-cm periods, and radiation was produced at the fundamental frequency near 4.5 GHz. Second and third harmonics were observed at the expected angles. Beam bunching was measured using a Bdot probe placed at the end of a groove. Generally good agreement between this experiment and the 2-D theory is found.
Accepted Wed Oct 21, 2009
Experimental demonstration and visual observation of dust trapping in an electron storage ring
Yasunori Tanimoto, Tohru Honda and Shogo Sakanaka
Sudden decreases in the beam lifetime, which are attributed to the dust trappings, sometimes occur at the electron storage ring PF-AR. Since these dust events cause difficulties in user operations, we have been carefully observing this phenomenon for many years. Our observations indicated that the dust trappings could be caused by electric discharges in vacuum ducts. In order to demonstrate this hypothesis experimentally, we designed a new vacuum device that intentionally generates electric discharges and installed it in PF-AR. Using this device, we could repeatedly induce sudden decreases in the beam lifetime because of the generated electric discharge. We also detected decreases in the beam lifetime caused by mechanical movement of the electrodes in the device. Moreover, we could visually observe the dust trapping phenomenon; the trapped dust particle was observed by two video cameras and appeared as a luminous body that resembled a shooting star. This was the first direct observation of a luminous dust particle trapped by the electron beam.
Accepted Fri Oct 2, 2009
New Acceleration Techniques
Electron bunch compression using a laser plasma compressor
W. van Dijk, M. J. van der Wiel and G. J. H. Brussaard
A new scheme for the compression of electron bunches is proposed. This scheme uses a plasma wave generated by a high intensity laser pulse to compress an electron bunch produced by a typical RF-photogun. In the scheme, the electron bunch is injected into a plasma channel in front of the high intensity laser pulse. The laser pulse generates a plasma wave which 'sweeps up' the electron bunch resulting in both compression and acceleration. The electron bunch will eventually overtake the laser pulse so that afterwards, the electrons travel in front of the plasma wave. The scheme differs from previous schemes using a plasma wave to accelerate and compress electron bunches by sacrificing part of the acceleration to get a lower final energy spread and decrease the sensitivity to jitter in the synchronization between laser and electrons. Using a hybrid model, combining particle tracking for the electrons and a relativistic fluid model for the plasma, the scheme is investigated. The model is used to study the effects of the size of the injected bunches, the initial energy spread and jitter in the laser-bunch synchronization. Also, one of the ways to vary the compression ratio of the scheme is explored by varying the plasma density. From these simulations, it can be concluded that the proposed scheme can compress bunches from an initial size of picoseconds to below one hundred femtoseconds with a energy spread below 0.2%. The scheme can also be adjusted to still produce these bunches in the presence of synchronization jitter up to 1nbsp;ps (for the parameters chosen).
Accepted Mon Nov 2, 2009
Dimuon production by laser wakefield accelerated electrons
A. I. Titov, B. Kampfer and H. Takabe
We analyze m+m- pair production generated by high-energy electrons emerging from a laser-wakefield accelerator. The m+m- pairs are created in a solid thick high-Z target, following the electron accelerating plasma region. Numerical estimates are presented for 1 to 10 GeV electron beams which are expected to be reliable in the nearest future. Reactions induced by the secondary bremsstrahlung photons dominate the dimuon production. According to our estimates, a 20 pC electron bunch with energy of 1 (10) GeV may create about 100 (5000) muon pairs. The produced m can be used in studying various aspects of muon-related physics in table top installations. This may be considered as an important step towards the investigation of more complicated elementary processes induced by laser driven electrons.
Accepted Wed Oct 7, 2009
Other Accelerator Subsystems and Technologies
Coaxial type water load for measuring high voltage, high current and short pulse of a compact Marx system for a high power microwave source
Jaeeun Han, Jungho Kim, Sangduck Park, Moohyun Yoon, Soo Yong Park, Do Won Choi, Jin Woo Shin and Joo Son Ho
A coaxial-type water load was used to measure the voltage output from a Marx generator for a high power microwave source. This output had a rise time of 20 ns, a pulse duration of a few hundred ns and an amplitude up to 500 kV. The design of the coaxial water load showed that it is an ideal resistive divider and can also accurately measure a short pulse. Experiments were performed to test the performance of the Marx generator with the calibrated coaxial water load.
Accepted Tue Oct 20, 2009
Virtual cathode emission of an annular cold cathode
S.d. Park, J.h. Kim, J. Han, M. Yoon, S. Y. Park, D. W. Choi, J. W. Shin and J.H So.
Recent measurement of voltage V and current I of the electron gun of a relativistic klystron amplifier (RKA) revealed that the resulting current-voltage relationship appeared to differ from the usual Child-Langmuir law (I V3/2) especially during the initial period of voltage increase. This paper attempts to explain this deviation by examining the emission mechanism using particle-in-cell (PIC) simulation. The emission area in the cathode increased stepwise as the applied voltage increased and within each step the current and voltage followed the Child-Langmuir law. The electron emission began when the voltage reached a threshold, and the perveance increased with the emission area. Furthermore, an apparent virtual cathode was formed which was larger than the cathode tip. This occurs because above a certain voltage the emission from the edge and the side of the cathode surface dominates the emission from the front-end surface.
Accepted Mon Oct 5, 2009
Relativistic, Multiple-Particle Dynamics
Incoherent effect of space charge and electron cloud
G. Franchetti, I. Hofmann, W. Fischer and F. Zimmermann
Trapping by resonances or scattering off resonances induced by space charge (SC) or electron cloud (EC) in conjunction with synchrotron motion can explain observations of slow beam loss and emittance growth, which are often accompanied by changes in the longitudinal beam profile. In this paper we review the recent progress in understanding and modeling of the underlying mechanisms, highlight the differences and similarities between space charge and electron cloud, and discuss simulation results in the light of experimental observations, e.g., at GSI, CERN and BNL. In particular we address the role of the pinched electrons and describe in detail the complexity of the electron pinch formation. We present simulation results within a dipole or in a field-free region of the beam pipe, which reveal the morphology and main features of this phenomenon, explain the physical origin of the complex electron structures like "stripes" in either field configuration, and discuss the dependence on some key parameters.
Accepted Wed Oct 14, 2009
Applications
Optimal choice of cell geometry for a multicell superconducting cavity
Valery Shemelin
An algorithm for optimization of the multicell cavity cells is proposed. Inner cells are optimized for minimal losses or minimal magnetic field, when the aperture diameter, pk acc E E the ratio of peak electric field to the accelerating field, and the wall slope angle are given. Optimization of the end cells is done for minimal losses or maximal acceleration in them. Two shapes of the end cells with and without the end irises are analyzed. This approach facilitates further optimization for higher order modes extraction because it permits keeping the achieved optimal values nearly the same while changing some dimensions of the cells. Comparison of the proposed cavity geometry with the TESLA cavity geometry illustrates the traits of the presented approach. It is also shown that lower values of the wall slope angle, which lead to the reentrant shape for the inner cells, are also beneficial for the end cells. For the Cornell Energy Recovery Linac most dangerous are dipole modes causing the beam break-up (BBU). Minimization of power of higher order modes (HOMs) in a multicell cavity was done using derivatives of the BBU parameter with respect to geometric parameters of the cavity cells. As a start point of optimization the shape with minimal losses at the fundamental mode was taken. Further changing the shape for better propagation of HOMs was done with degradation of the fundamental mode loss parameter G R Q sh within 1 % while decrease of the BBU parameter was nearly 3 orders of magnitude. The BBU threshold current tends to be inversely proportional to this parameter.
Accepted Wed Sep 9, 2009
Review Articles
Generation of initial kinetic distributions for simulation of long pulse charged particle beams with high space charge intensity
Steven M. Lund, Takashi Kikuchi and Ronald C. Davidson
Self-consistent Vlasov-Poisson simulations of beams with high space-charge intensity often require specification of initial phase-space distributions that reflect properties of a beam that is well adapted to the transport channel - both in terms of low-order rms (envelope) properties as well as the higher-order phase-space structure. Here, we first review broad classes of kinetic distributions commonly in use as initial Vlasov distributions in simulations of unbunched or weakly bunched beams with intense space-charge fields including: the Kapchinskij-Vladimirskij (KV) equilibrium, continuous-focusing equilibria with specific detailed examples, and various non-equilibrium distributions, such as the semi-Gaussian distribution and distributions formed from specified functions of linear-field Courant-Snyder invariants. Important practical details necessary to specify these distributions in terms of standard accelerator inputs are presented in a unified format. Building on this presentation, a new class of approximate initial kinetic distributions are constructed using transformations that preserve linear-focusing, single-particle Courant-Snyder invariants to map initial continuous-focusing equilibrium distributions to a form more appropriate for non-continuous focusing channels. Self-consistent particle-in-cell simulations are employed to show that the approximate initial distributions generated in this manner are better adapted to the focusing channels for beams with high space-charge intensity. This improved capability enables simulations that more precisely probe intrinsic stability properties and machine performance.
Accepted Fri Sep 25, 2009
Errata
Erratum: Quantum efficiency and thermal emittance of metal photocathodes [Phys. Rev. ST Accel. Beams \textbf{12}, 074201 (2009)]
David H. Dowell and John F. Schmerge
Accepted Tue Nov 3, 2009
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Of the referees used for Physical Review journals in 2008, 66% were from outside the US.
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