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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...
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Image from V. A. Goryashko et al. Phys. Rev. ST Accel Beams 12 100701 (2009), Hybrid planar free-electron maser in the magnetoresonance regime.
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September 1, 2010 Physical Review Special Topics - Accelerators and Beams is publishing a conference edition for the 32nd International Free Electron Laser Conference (FEL2010) held in Malmö, Sweden, 23-27 August 2010 (http://fel2010.maxlab.lu.se/). Dr. Atoosa Meseck of HZB (currently at Cornell), also chair of the FEL2010 Scientific Program Committee, will act as the special editor of this edition. More information... More News/Announcements
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July 28, 2010 The American Physical Society (APS) announces a new public access initiative that will give readers and researchers in public libraries in the United States full use of all online APS journals.
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July 6, 2010 APS and CERN are pleased to announce that the initial experimental results from the LHC published in Physical Review Letters and Physical Review will be made available Open Access and under a Creative Commons license, for all interested parties to read and reuse. With this gesture, APS and CERN acknowledge the fundamental significance of the work being performed by these large international collaborations.
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April 2, 2010 Physical Review Special Topics - Accelerators and Beams is offering a Special Edition for the 2010 International Particle Accelerator Conference that will be held May 23-28, 2010 in Kyoto, Japan. This Special Edition offers the opportunity to expand upon original research presented at IPAC'10 in a peer-reviewed journal. More information... More News/Announcements
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January 26, 2010  The editors of the APS journals have selected 157 new Outstanding Referees for 2010, out of more than 42,000 currently active referees. Initiated in 2008, the highly selective Outstanding Referee program recognizes scientists who have been exceptionally helpful in assessing manuscripts for publication in the APS journals. Selections are based on two decades of records on the number, quality, and timeliness of referee reports. The 2010 honorees come from 30 different countries, with large contingents from the US, Germany, UK, Canada, and France. The decisions were difficult and there are many excellent referees who have yet to be recognized. By means of the program, APS expresses appreciation to all referees, whose efforts in peer review not only keep the standards of the journals at a high level, but in many cases also help authors to improve the quality and readability of their articles—even those that are not published by APS. For more information and a sortable listing of all Outstanding Referees, please visit http://publish.aps.org/OutstandingReferees.
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January 4, 2010 As part of a new APS initiative all APS journal content from 1893 to present is now hosted on a single platform run by the APS Editorial Office. In addition, we have added new APS Journal accounts that will allow us to better integrate all APS services provided to readers, authors, referees, and members during the coming year while allowing users to have a more personalized view. This new foundation will allow APS to move quickly to introduce many new features across all of our web sites.
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December 11, 2009 Physical Review Special Topics - Accelerators and Beams is publishing a conference edition for the International Conference on RF Superconductivity held in Berlin and Dresden, Germany, 17-25 September 2009 (http://srf2009.bessy.de/index.htm). Prof. Jean Delayen of the Thomas Jefferson National Accelerator Facility will act as the special editor of this edition. More Information.... More News/Announcements
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December 11, 2009 Physical Review Special Topics - Accelerators and Beams is publishing a conference edition for the International Workshop on The Physics and Applications of High Brightness Electron Beams held on Maui, Hawaii, 16-19 November 2009 (http://pbpl.physics.ucla.edu/HBEB/index.html). Prof. James Rosenzweig of UCLA, also the Conference Chair, will act as the special editor of this edition.. More Information... 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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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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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
R. Tomás
The CLIC study is exploring the scheme for an electron-positron collider with a center-of-mass energy of 3 TeV in order to make the multi-TeV range accessible for lepton physics. The current goal of the project is to demonstrate the feasibility of the technology by the year 2010. Recently, importan...
[Phys. Rev. ST Accel. Beams 13, 014801
] Published Mon Jan 11, 2010
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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 ...
[Phys. Rev. ST Accel. Beams 12, 114801
] Published Thu Nov 19, 2009
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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.
Low- and Intermediate-Energy Accelerators
Chuan Zhang, Marco Busch, Horst Klein, Holger Podlech, Ulrich Ratzinger, Rudolf Tiede, and Jean-Luc Biarrotte
EUROTRANS is a European research program for the transmutation of high level nuclear waste in an accelerator-driven system (ADS). As proposed, the driver linac needs to deliver a 2.5–4 mA, 600 MeV continuous-wave (CW) proton beam and later a 20 mA, 800 MeV one to the spallation target in the p...
[Phys. Rev. ST Accel. Beams 13, 080101
] Published Wed Aug 11, 2010
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Pulsed-Power Accelerators, Technology, and Dynamics
J. R. Woodworth, W. A. Stygar, L. F. Bennett, M. G. Mazarakis, H. D. Anderson, M. J. Harden, J. R. Blickem, F. R. Gruner, and R. White
We have developed two new gas switches that are designed to be used with linear transformer drivers. The switches, which can be DC charged to 200 kV and triggered with less than a 2-ns 1-σ jitter, have overall inductances ranging from 69 to 85 nH. When transferring 400 J of energy per shot, the ...
[Phys. Rev. ST Accel. Beams 13, 080401
] Published Wed Aug 25, 2010
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Synchrotron Radiation and Free-Electron Lasers
M. H. Rouhani and B. Maraghechi
Three-dimensional simulation of harmonic up-conversion in a free-electron laser amplifier operating simultaneously with two cold and relativistic electron beams with different energy is presented in the steady-state regime. The fundamental resonance of the higher energy beam is adjusted at the third...
[Phys. Rev. ST Accel. Beams 13, 080706
] Published Wed Aug 18, 2010
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Y. Li, W. Decking, B. Faatz, and J. Pflueger
At the European X-ray Free Electron Laser there is a planar undulator system under construction called SASE3, which produces intense linearly polarized light in the wavelength range from 0.4–1.6 nm. Nevertheless there is a strong demand for circularly polarized radiation in this wavelength range....
[Phys. Rev. ST Accel. Beams 13, 080705
] Published Tue Aug 10, 2010
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M. Venturini, M. Migliorati, C. Ronsivalle, M. Ferrario, and C. Vaccarezza
Free-electron lasers operating in the UV or x-ray radiation spectrum require peak beam currents that are generally higher than those obtainable by present electron sources, thus making bunch compression necessary. Compression, however, may heighten the effects of collective forces and degrade the be...
[Phys. Rev. ST Accel. Beams 13, 080703
] Published Thu Aug 5, 2010
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Kevin L. Jensen, P. G. O’Shea, and D. W. Feldman
The emittance of a photocathode is evaluated using a distribution function (“Moments”) approach to calculate the moments of the momentum. The effects of temperature and field, which affect the electron distribution and transmission probability, respectively, of electrons incident on the surface ...
[Phys. Rev. ST Accel. Beams 13, 080704
] Published Thu Aug 5, 2010
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B. Jia, J. Li, S. Huang, Scott C. Schmidler, and Y. K. Wu
In accelerators, the electron beam longitudinal dynamics critically depend on the energy distribution of the beam. Noninvasive, highly accurate measurement of the energy spread of the electron beam in the storage ring remains a challenge. Conventional techniques are limited to measuring a relatively...
[Phys. Rev. ST Accel. Beams 13, 080702
] Published Wed Aug 4, 2010
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F. Fiuza, L. O. Silva, and C. Joshi
Using multidimensional particle-in-cell simulations, we show that the magnetic undulator-type field of the plasma magnetostatic mode is indeed produced by the interaction of a laser pulse with a relativistic ionization front, as predicted by linear theory for a cold plasma. When the front with this ...
[Phys. Rev. ST Accel. Beams 13, 080701
] Published Tue Aug 3, 2010
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Yu. A. Chesnokov, V. A. Maisheev, D. Bolognini, S. Hasan, M. Prest, and E. Vallazza
The process of photoproduction of electron-positron pairs in bent single crystals is considered. This consideration is based on the theory of coherent pairproduction in straight single crystals and take into account the linear polarization of the photon beam. In particular, it is shown that the prob...
[Phys. Rev. ST Accel. Beams 13, 070706
] Published Thu Jul 29, 2010
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Zh. S. Gevorkian
Radiation of a charged particle moving parallel to an inhomogeneous surface is considered. Within a single formalism periodic and random gratings are examined. For the periodically inhomogeneous surface we derive new expressions for the dispersion relation and the spectral-angular intensity. In part...
[Phys. Rev. ST Accel. Beams 13, 070705
] Published Wed Jul 28, 2010
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F. Albert, S. G. Anderson, D. J. Gibson, C. A. Hagmann, M. S. Johnson, M. Messerly, V. Semenov, M. Y. Shverdin, B. Rusnak, A. M. Tremaine, F. V. Hartemann, C. W. Siders, D. P. McNabb, and C. P. J. Barty
A high peak brilliance, laser-based Compton-scattering γ-ray source, capable of producing quasimonoenergetic photons with energies ranging from 0.1 to 0.9 MeV has been recently developed and used to perform nuclear resonance fluorescence (NRF) experiments. Techniques for characterization of γ-ray...
[Phys. Rev. ST Accel. Beams 13, 070704
] Published Tue Jul 27, 2010
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High-Energy Accelerators and Colliders
I. Strašík, E. Mustafin, and M. Pavlovič
The paper presents results of FLUKA simulations of the residual activity induced by heavy ions in two target configurations representing: (1) a beam pipe of an accelerator and (2) a bulky accelerator structure like a magnet yoke or a coil. The target materials were stainless steel and copper repre...
[Phys. Rev. ST Accel. Beams 13, 071004
] Published Wed Jul 28, 2010
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New Acceleration Techniques
H. K. Avetissian and Kh. V. Sedrakian
Laser acceleration due to the nonlinear-threshold phenomena of charged particle “reflection” and capture by slowed wave in a magnetic undulator is considered. The obtained numerical results prove the particle reflection and capture phenomena in the field of actual laser pulses with temporal and ...
[Phys. Rev. ST Accel. Beams 13, 081301
] Published Wed Aug 4, 2010
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M. Nishiuchi et al.
A laser-driven repetition-rated 1.9 MeV proton beam line composed of permanent quadrupole magnets (PMQs), a radio frequency (rf) phase rotation cavity, and a tunable monochromator is developed to evaluate and to test the simulation of laser-accelerated proton beam transport through an integrated sy...
[Phys. Rev. ST Accel. Beams 13, 071304
] Published Thu Jul 29, 2010
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Radio Frequency Calculations and Technology
A. Neumann, W. Anders, O. Kugeler, and J. Knobloch
Many proposals for next generation light sources based on single pass free electron lasers or energy recovery linac facilities require a continuous wave (cw) driven superconducting linac. The effective beam loading in such machines is very small and in principle the cavities can be operated at a ban...
[Phys. Rev. ST Accel. Beams 13, 082001
] Published Wed Aug 4, 2010
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Beam Control, Diagnostics, and Feedback
A. Araz, U. Bonnes, R. Eichhorn, F. Hug, M. Konrad, M. Platz, A. Richter, and R. Stassen
The low level rf system for the superconducting Darmstadt electron linear accelerator (S-DALINAC) developed 20 years ago and operating since converts the 3 GHz signals from the cavities down to the baseband and not to an intermediate frequency. While designing the new, digital rf control system th...
[Phys. Rev. ST Accel. Beams 13, 082801
] Published Tue Aug 10, 2010
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Stephen Molloy, Paul Emma, Josef Frisch, Rick Iverson, Marc Ross, Doug McCormick, Mike Woods, and Sean Walston
Bunch length and energy-z correlation measurements were performed on the high energy (28.5 GeV) electron test beam of the A-line and End Station A (ESA) facilities at the SLAC National Accelerator Laboratory. The longitudinal profile of each bunch was measured by imaging the synchrotron light emitt...
[Phys. Rev. ST Accel. Beams 13, 082802
] Published Tue Aug 10, 2010
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Other Accelerator Subsystems and Technologies
Hui Tian and Charles E. Reece
Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nanosmoothness. Electropolishing (EP) is the technique of choice being developed for high-field superconducting radio frequency (SRF) cavities. Previous study has shown that the mechanism o...
[Phys. Rev. ST Accel. Beams 13, 083502
] Published Wed Aug 25, 2010
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F. Eozénou, S. Berry, C. Antoine, Y. Gasser, J.-P. Charrier, and B. Malki
Electropolishing (EP) in the HF-H2SO4 electrolyte is the most desirable surface treatment for niobium superconducting radio frequency cavities yet demonstrated, in terms of performance and surface finish. However, the efficiency of the electrolyte declines quickly with time (decrease in removal rate...
[Phys. Rev. ST Accel. Beams 13, 083501
] Published Tue Aug 10, 2010
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Single-Particle Dynamics
Dao Xiang and Yuantao Ding
A longitudinal-to-transverse mapping technique is proposed to measure the length and temporal profile of ultrashort electron bunches. In this scheme a special chicane and a radio-frequency deflecting cavity are used to transform the beam’s longitudinal distribution into angular distribution which ...
[Phys. Rev. ST Accel. Beams 13, 094001
] Published Wed Sep 1, 2010
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V. Danilov and S. Nagaitsev
Integrable systems appeared in physics long ago at the onset of classical dynamics with examples being Kepler’s and other famous problems. Unfortunately, the majority of nonlinear problems turned out to be nonintegrable. In accelerator terms, any 2D nonlinear nonintegrable mapping produces chaotic...
[Phys. Rev. ST Accel. Beams 13, 084002
] Published Wed Aug 25, 2010
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Shinji Machida and Richard Fenning
A scaling fixed field alternating gradient (FFAG) accelerator provides large momentum acceptance despite the fact that magnetic guiding fields are constant in time. Optical functions are identical over the large momentum range as well. We have designed a straight beam transport line (BTL) using a sc...
[Phys. Rev. ST Accel. Beams 13, 084001
] Published Wed Aug 11, 2010
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Low-Energy, Multiple-Particle Dynamics
V. Volkov, J. Knobloch, and A. Matveenko
We present an extension of the calculation of dipole-mode driven beam break-up instabilities, as calculated in [V. Volkov, Phys. Rev. ST Accel. Beams 12, 011301 (2009); V. Volkov, J. Knobloch, and A. Matveenko, Phys. Rev. ST Accel. Beams (to be published)], to the monopole fundamental mode passband....
[Phys. Rev. ST Accel. Beams 13, 084201
] Published Thu Aug 19, 2010
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Aimin Xiao and Michael Borland
We present a Monte Carlo method implementation in the code elegant for simulating Touschek scattering effects in a linac beam. The local scattering rate and the distribution of scattered electrons can be obtained from the code either for a Gaussian-distributed beam or for a general beam whose distr...
[Phys. Rev. ST Accel. Beams 13, 074201
] Published Fri Jul 30, 2010
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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
Circuit models and three dimensional electromagnetic simulations of a 1-MA linear transformer driver stage
D. V. Rose, C. L. Miller, D. R. Welch, R. E. Clark, E. A. Madrid, C. B. Mostrom, W. A. Stygar, K. R. Le Chien, M. A. Mazarakis, W. L. Langston, J. L. Porter and J. R. Woodworth
A 3D fully electromagnetic (EM) model of the principal pulsed-power components of a high-current linear transformer driver (LTD) has been developed. LTD systems are a relatively new modular and compact pulsed-power technology based on high-energy density capacitors and low-inductance switches located within a linear-induction cavity. We model 1-MA, 100-kV, 100-ns rise-time LTD cavities [A. A. Kim, et al., Phys.nbsp;Rev.nbsp;ST Accel.nbsp;Beams 12, 050402 (2009)] which can be used to drive z-pinch and material dynamics experiments. The model simulates the generation and propagation of electromagnetic power from individual capacitors and triggered gas switches to a radially-symmetric output line. Multiple cavities, combined to provide voltage addition, drive a water-filled coaxial transmission line. A 3D fully EM model of a single 1-MA 100-kV LTD cavity driving a simple resistive load is presented and compared to electrical measurements. A new model of the current loss through the ferromagnetic cores is developed for use both in circuit representations of an LTD cavity and in the 3D EM simulations. Good agreement between the measured core current, a simple circuit model, and the 3D simulation model is obtained. A 3D EM model of an idealized 10-cavity LTD accelerator is also developed. The model results demonstrate efficient voltage addition when driving a matched impedance load, in good agreement with an idealized circuit model.
Accepted Mon Aug 9, 2010
Synchrotron Radiation and Free-Electron Lasers
Laser induced narrowband coherent synchrotron radiation: Efficiency versus frequency and laser power
C. Evain, C. Szwaj, S. Bielawski, M. Hosaka, Y. Takashima, M. Shimada, S. Kimura, M. Katoh, A. Mochihashi, T. Takahashi and T. Hara
We analyze the narrowband terahertz emission process occurring from electron bunches passing in a bending magnet, after a laser-induced sinusoidal modulation has been performed. In particular we focus on experimental tunability curves, and power scalings with current and laser power. Theoretically, we simplify the problem formulation using the slowly varying envelope approximation. At low powers, the scaling with laser power appears to be quadratic, and analytical expressions for the tuning curves are obtained. Emission at first passage in the bending magnet, and after one full turn in the storage ring, are considered both experimentally and theoretically. The experiments are performed on the UVSOR-II storage ring.
Accepted Thu Jul 22, 2010
High-Energy Accelerators and Colliders
Time evolution of the luminosity of colliding heavy ion beams in BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider
R. Bruce, J. M. Jowett, M. Blaskiewicz and W. Fischer
We have studied the time evolution of the heavy ion luminosity and bunch intensities in the Relativistic Heavy Ion Collider (RHIC), at BNL, and in the Large Hadron Collider (LHC), at CERN. First, we present measurements from a large number of RHIC stores (from Run 7), colliding 100nbsp;GeV/nucleon nbsp;beams without stochastic cooling. These are compared with two different calculation methods. The first is a simulation based on multi-particle tracking taking into account collisions, intrabeam scattering, radiation damping, and synchrotron and betatron motion. In the second, faster, method, a system of ordinary differential equations with terms describing the corresponding effects on emittances and bunch populations is solved numerically. Results of the tracking method agree very well with the RHIC data. With the faster method, significant discrepancies are found since the losses of particles diffusing out of the RF bucket due to intrabeam scattering are not modeled accurately enough. Finally, we use both methods to make predictions of the time evolution of the future nbsp;beams in the LHC at injection and collision energy. For this machine, the two methods agree well.
Accepted Mon Aug 23, 2010
New Acceleration Techniques
Physics considerations for laser plasma linear colliders
C. B. Schroeder, E. Esarey, C. G. R. Geddes, C. Benedetti and W. P. Leemans
Physics considerations for a next-generation linear collider based on laser-plasma accelerators are discussed. The ultra-high accelerating gradient of a laser-plasma accelerator and short laser coupling distance between accelerator stages allows for a compact linac. Two regimes of laser-plasma acceleration are discussed. The highly nonlinear regime has the advantages of higher accelerating fields and uniform focusing forces, whereas the quasi-linear regime has the advantage of symmetric accelerating properties for electrons and positrons. Scaling of various accelerator and collider parameters with respect to plasma density and laser wavelength are derived. Reduction of beamstrahlung effects implies the use of ultra-short bunches of moderate charge. The total linac length scales inversely with the square root of the plasma density, whereas the total power scales proportional to the square root of the density. A 1nbsp;TeV center-of-mass collider based on stages using a plasma density of 1017nbsp;cm-3 requires tens of J of laser energy per stage (using 1nbsp;mm wavelength lasers) with tens of kHz repetition rate. Coulomb scattering and synchrotron radiation are examined and found not to significantly degrade beam quality. A photon collider based on laser-plasma accelerated beams is also considered. The requirements for the scattering laser energy are comparable to those of a single laser-plasma accelerator stage.
Accepted Mon Aug 30, 2010
Density transition based electron injector for laser driven wakefield accelerators
K. Schmid, A. Buck, C. M. S. Sears, J. M. Mikhailova, R. Tautz, D. Herrmann, M. Geissler, F. Krausz and L. Veisz
We demonstrate a laser wakefield accelerator with a novel electron injection scheme resulting in enhanced stability, reproducibility and ease of use. In order to inject electrons into the accelerating phase of the plasma wave a sharp downward density transition is employed. Prior to ionization by the laser pulse this transition is formed by a shock-front induced by a knife edge inserted into a supersonic gas jet. With laser pulses of 8 fs duration and with only 65 mJ energy on target the accelerator produces a monoenergetic electron beam with tunable energy between 15 and 25nbsp;MeV and on average 3.3 pC charge per electron bunch. The shock-front injector is a simple and powerful new tool to enhance the reproducibility of laser-driven electron accelerators, is easily adapted to different laser parameters and should therefore allow scaling to the energy range of several hundred MeV.
Accepted Mon Aug 23, 2010
Beam Control, Diagnostics, and Feedback
Emittance and divergence of laser wakefield accelerated electrons
Christopher M. S. Sears, Alexander Buck, Karl Schmid, Julia Mikhailova, Ferenc Krausz and Laszlo Veisz
We apply the pepper-pot method to measure in a single shot the transverse emittance of quasi-monoenergetic electrons with 20nbsp;MeV energy produced by laser wakefield acceleration (LWFA). The large divergence of LWFA beams ( 1nbsp;mrad typical) compared to conventional RF accelerator beams places additional restrictions on the pepper-pot design. The LWFA beam is found to have a normalized RMS transverse emittance of eN = 2.3nbsp;pnbsp;mmnbsp;mrad, with a shot-to-shot fluctuation of 17%. This emittance is comparable to state-of-the-art injectors for conventional linear accelerators. In addition we examine the beam divergence of LWFA electrons. Simulations and theory indicate that an adiabatic reduction in the beam divergence occurs when the transition region of the downstream plasma density profile is comparable to the betatron period of the electron beam in the plasma accelerator.
Accepted Wed Sep 1, 2010
Beam based measurement of beam position monitor electrode gains
D. L. Rubin, M. Billing, R. Meller, M. Palmer, M. Rendina, N. Rider, D. Sagan, J. Shanks and C. Strohman
Low emittance tuning at Cornell's CESR Test Accelerator depends on precision measurement of vertical dispersion and transverse coupling. The CESR beam position monitors consist of four button electrodes, instrumented with electronics that allow acquisition of turn by turn data. The response to the beam will vary among the four electrodes due to differences in electronic gain and/or misalignment. This variation in the response of the BPM electrodes will couple real horizontal offset to apparent vertical position, and introduce spurious measurements of coupling and vertical dispersion. To alleviate this systematic effect, a beam based technique to measure the relative response of the four electrodes has been developed. With typical CESR parameters, simulations show that turn-by-turn BPM data can be used to determine electrode gains to within ~ 0.1%.
Accepted Mon Aug 30, 2010
Single shot method for measuring femtosecond bunch length in linac based free electron lasers
Z. Huang, K. Bane, Y. Ding and P. Emma
There is a growing interest in the generation and characterization of femtosecond and sub-femtosecond pulses from linac-based free-electron lasers (FELs). In this report, following the method of K. Ricci and T. Smith [Phys. Rev. ST-AB 3, 032801 (2000)], we investigate the measurement of the longitudinal bunch profile of an ultra-short electron bunch produced by these FELs. We show that this method can be applied in a straightforward manner at x-ray FEL facilities such as the Linac Coherent Light Source by slightly adjusting the second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final linac. We find that the linac wakefield strongly perturbs the measurement, and through analysis show that it can be compensated in a simple way. We demonstrate the effectiveness of this method and wakefield compensation through numerical simulations, including effects of coherent synchrotron radiation and longitudinal space charge. When used in conjunction with a high-resolution electron spectrometer, this method potentially reveals the temporal profile of the electron beam down to the femtosecond and sub-femotsecond scale.
Accepted Tue Aug 24, 2010
Other Accelerator Subsystems and Technologies
Modification on surface oxide layer structure and surface morphology of niobium by gas cluster ion beam treatments
A.T Wu., D. R. Swenson and Z. Insepov
Recently, it was demonstrated that significant reductions in field emission on Nb surfaces could be achieved by means of a new surface treatment technique called gas cluster ion beam (GCIB). Further study as shown in this paper revealed that GCIB treatments could modify surface irregularities and remove surface asperities leading to a smoother surface finish as demonstrated through measurements using a 3-D profilometer, an atomic force microscope, and a scanning electron microscope. These experimental observations were supported by computer simulation via atomistic molecular dynamics and a phenomenological surface dynamics. Measurements employing a secondary ion mass spectrometry found that GCIB could also alter Nb surface oxide layer structure. Possible implications of the experimental results on the performance of Nb superconducting radio frequency cavities treated by GCIB will be discussed. First experimental results on Nb single cell superconducting radio frequency cavities treated by GCIB will be reported.
Accepted Tue Aug 31, 2010
Electron beam characterization of a combined diode rf electron gun
R. Ganter, B. Beutner, S. Binder, H. H. Braun, T. Garvey, C. Gough, C. Hauri, R. Ischebeck, S. Ivkovic, F. Le Pimpec, K. Li, M. L. Paraliev, M. Pedrozzi, T. Schietinger, B. Steffen, A. Trisorio and A. Wrulich
Experimental and simulation results of an electron gun test facility based on pulsed diode acceleration followed by a two-cell rf cavity at 1.5 GHz, are presented here. The main features of this diode – rf combination are: a high peak gradient in the diode (up to 100 MV/m) obtained without breakdown conditioning, a cathode shape providing an electrostatic focusing and an in vacuum pulsed solenoid to focus the electron beam between the diode and the rf cavity. Although the test stand was initially developed for testing field emitter arrays (FEA) cathodes, it became also interesting to explore the limits of this electron gun with metallic photocathodes illuminated by laser pulses. The ultimate goal of this test facility is to fulfill the requirements of the SwissFEL project of PSI [B.D. Patterson et. al. NJP 12 (2010)]; a projected normalized emittance below 0.4 μm for a charge of 200 pC and a bunch length of less than 10 ps (rms). A normalized projected emittance of 0.23 μm with 13 pC has been measured at 5 MeV using a Gaussian laser longitudinal intensity distribution on the photocathode. Good agreements with simulations have been obtained for different electron bunch charge and diode geometries. Emittance measurements at a bunch charge below 1 pC were performed for different laser spot sizes in agreement with intrinsic emittance theory (e.g. 0.54 μm / mm of laser spot size (rms) for Cu at 274 nm). Finally, a projected emittance of 1.25 +/- 0.2 μm was measured with 200 pC and 100 MV/m diode gradient.
Accepted Tue Aug 24, 2010
Charge state distribution measurements of ^{238}U and ^{136}Xe at 11 MeV/nucleon using gas charge stripper
H. Kuboki, H. Okuno, S. Yokouchi, H. Hasebe, T. Kishida, N. Fukunishi, O. Kamigaito, A. Goto, M. Kase and Y. Yano
The charge-state distributions and equilibrium charge states of uraniumnbsp;(238U) and xenonnbsp;(136Xe) ions at 11nbsp;MeV/nucleon were determined using a gas charge stripper. A differential pumping system facilitated the increase of the nitrogen gas thickness up to 1.3nbsp;mg/cm2, which is sufficient for the most probable charge state to attain equilibrium. The charge states of 238U attain equilibrium at 56.0, 56.6, and 55.7 in N2, Ar, and CO2 media with thicknesses of 125, 79, and 126nbsp;mg/cm2, respectively, while those of 136Xe attain equilibrium at 40.5, 40.1, and 40.3 in N2, Ar, CO2 media with thicknesses of 163, 95, and 139nbsp;mg/cm2, respectively. The equilibrium charge states of 136Xe are acceptable for acceleration by the subsequent cyclotron. The measured data of 238U were used to devise an empirical formula for the prediction of the equilibrium charge state in gaseous media over the energy region of 0.01-60nbsp;MeV/nucleon. The equilibrium charge state of 136Xe as predicted by the devised formula is in good agreement with the data.
Accepted Fri Aug 13, 2010
Applications
Solution of the Boltzmann equation for primary light ions and the transport of their fragments
J. Kempe and A. Brahme
The Boltzmann equation for the transport of pencil beams of light ions in semi-infinite uniform media has been calculated. The equation is solved for the practically important generalized 3D case of Gaussian incident primary light ion beams of arbitrary mean square radius, mean square angular spread and covariance. The transport of the associated fragments in three dimensions is derived based on the known transport of the primary particles, taking the mean square angular spread of their production processes, as well as their energy loss and multiple scattering, into account. The analytical pencil and broad beam depth fluence and absorbed dose distributions are accurately expressed using recently derived analytical energy and range formulae. The contributions from low and high Linear Energy Transfer (LET) dose components were separately identified using analytical expressions. The analytical results are compared with SHIELD-HIT Monte Carlo (MC) calculations and found to be in very good agreement. The pencil beam fluence and absorbed dose distributions of the primary particles are mainly influenced by an exponential loss of the primary ions combined with an increasing lateral spread due to multiple scattering and energy loss with increasing penetration depth. The associated fluence of heavy fragments is concentrated at small radii and so is the LET and absorbed dose distribution. Their transport is also characterized by the build up of a slowing down spectrum which is quite similar to that of the primaries but with a wider energy and angular spread at increasing penetration depths. The range of the fragments is shorter or longer depending on their nuclear mass to charge ratio relative to that of the primary ions. The absorbed dose of the heavier fragments is fairly similar to that of the primary ions and also influenced by a rapidly increasing energy loss towards the end of their ranges. The present analytical solution of the Boltzmann equation accurately accounts for the loss of primary particles as well as their energy losses and multiple scattering. At the same time these quantities for the fragments are also accurately derived as based on the generalized Gaussian solution of the primaries and compared both with Monte Carlo and experimental data. The results are useful for fast transport calculations and biologically optimized therapy planning with light ions beams.
Accepted Wed Sep 1, 2010
Single shot femtosecond x-ray diffraction from randomly oriented ellipsoidal nanoparticles
M. J. Bogan, S. Boutet, A. Barty, W. H. Brenner, M. Frank, L. Lomb, R. Shoeman, D. Starodub, M. M. Seibert, S. P. Hau Riege, B. Woods, P. Decorwin Martin, S. Bajt, J. Schulz, U. Rohner, B. Iwan, N. Timneanu, S. Marchesini, I. Schlichting, J. Hajdu and H. N. Chapman
Coherent diffractive imaging of single particles using the single-shot "diffract and destroy" approach with an x-ray free electron laser (FEL) was recently demonstrated. A high-resolution low-noise coherent diffraction pattern, representative of the object before it turns into a plasma and explodes, results from the interaction of the FEL with the particle. Iterative phase retrieval algorithms are used to reconstruct two-dimensional projection images of the object from the recorded intensities alone. Here we describe the first single-shot diffraction data set that mimics the data proposed for obtaining 3D structure from identical particles. Ellipsoidal iron oxide nanoparticles (250 nmx50 nm) were aerosolized and injected through an aerodynamic lens stack into a soft x-ray FEL. Particle orientation was not controlled with this injection method. We observed that at the instant the x-ray pulse interacts with the particle, a snapshot of the particle's orientation is encoded in the diffraction pattern. The results give credence to one of the technical concepts of imaging individual nanometer and sub-nanometer-sized objects such as single molecules or larger clusters of molecules using hard x-ray FELs in the future and will be used to help develop robust algorithms for determining particle orientations and 3D structure.
Accepted Mon Aug 30, 2010
Review Articles
Review of observations of ground diffusion in space and in time and fractal model of ground motion
Vladimir Shiltsev
We present numerous observations of the diffusive motion of the ground and tunnels for scientific instruments and show that if systematic movements are excluded the remaining uncorrelated component of the motion obeys a characteristic fractal law with the displacement variance dY2 scaling with time- and spatial intervals T and L as dY2 \infinity T \alpha L \gamma with both exponents close to 1 (\alpha almost equal to \gamma almost equal to 1). We briefly describe experimental methods of the meso- and microscopic ground motion detection used in measurements at physics research facilities sensitive to ground motion, particularly, large high energy elementary particle accelerators. A simple mathematical model of the fractal motion demonstrating the observed scaling law is also presented and discussed. This paper is a subsequent full detail publication to Ref.[1].
Accepted Thu Aug 19, 2010
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