JAI, Oxford
Accelerator physics is often viewed as a difficult subject to communicate to schools and the public. The "Accelerate!" project, initiated in the UK in 2008, engages audiences with accelerator physics through a 45-minute live, interactive demonstration show, using basic physics demonstrations to explain the physics of particle accelerators and what they are used for. Feedback has been overwhelmingly positive from all areas, and demand for the show is very high, with over 3000 students involved in the first year of running. The program is also contributing to the science communication skills of physics graduate students. I discuss how to portray basic accelerator concepts through easy to access demonstrations and initial results of audience evaluation of the show.
GSI, Darmstadt
IPCP, Chernogolovka, Moscow region
Universidad de Castilla-La Mancha, Ciudad Real
Rostock University, Rostock
Intense particle beams lead to volumetric heating of solid targets that generates large samples of High Energy Density (HED) matter. Such samples are very suitable to study the thermophysical properties of this important state of matter that spans over numerous fields of basic and applied physics. Facility for Antiprotons and Ion Research (FAIR) at Darmstadt, will generate very powerful bunched beams of the heaviest particles (uranium) that will deposit unprecedented high levels of specific power in the target. Extensive theoretical work has been carried out over the past decade to design HED physics experiments at the FAIR. So far, four different experimental schemes have been proposed. These include, HIHEX (Heavy Ion Heating and Expansion, which is suitable to study equation-of-state properties of HED matter), LAPLAS (Laboratory Planetary Science, which is suitable to generate physical conditions that exist in the interiors of the giant planets), Study of the growth of the Richtmyer-Meshkov instability and finally , the ion beam driven Ramp Compression which is suitable to study material properties like shear modulus and yield strength, under dynamic conditions.
JAEA, Kyoto
Parametric X-ray generation is one of the ways to obtain a monochromatic X-ray. The X-ray is generated through the interaction between high energy electrons and a crystal. The relationship between an X-ray wavelength and an angle of emission is followed by the Bragg condition. Therefore the monochromatic energy of the X-ray can be varied continuously by rotating the crystal. This tunability of X-ray wavelength is suitable for various applications. Usually a single photon counting method is utilized for measuring of the parametric X-rays. Although this method has an advantage to obtain clear energy spectrum, it takes long time. Here, we have measured 10 keV parametric X-rays with applying a rocking curve method. In this scheme, a large number of parametric X-rays are detected simultaneously. This enables us to find and tune the parametric X-ray quickly. As a result, we could find the sharp peak from this method with the Microtron accelerator (150MeV, 20 - 30 pC) at JAEA and a Si crystal. Since the peak angle is consistent to the Bragg condition for the 10 keV parametric X-ray generation, we think 10 keV photons have been generated through the parametric X-ray mechanism.
JAEA/Kansai, Kyoto
Intense laser pulse is utilized to generate compact sources of electrons, ions, x-rays, neutrons. Recently, high energy negative ions are also observed in experiments using cluster or gas target*. To explain the acceleration of negative ions from laser-generated plasmas, we proposed Coulomb implosion mechanism**. When clusters or underdense plasmas are irradiated by an intense laser pulse, positive ions are accelerated inside the clusters or in the self-focusing channel by the Coulomb explosion. This could lead to the acceleration of negative ions towards target center. The maximum energy of negative ions is typically several times lower than that of positive ions. A theoretical description and corresponding Particle-in-Cell simulations of Coulomb implosion mechanism are presented. We show the evidence of the negative ion acceleration observed in our experiments using high intensity laser pulse and the cluster-gas targets.
* S.Ter-Avetisyan et al., J. Phys. B 37 (2004) 3633.
** T.Nakamura et al., Phys. Plasmas 16 (2009) 113106.
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
TIT, Yokohama
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
BNL, Upton, Long Island, New York
Warm Dense Matter (WDM) is an challenging problem because WDM, which is beyond ideal plasma, is low temperature and high density state with partially degenerate electrons and coupled ions. WDM is a common state of matter in astrophysical objects such as cores of giant planets and white dwarfs. The WDM studies require large energy deposition into a small target volume in a shorter time than the hydrodynamical time and need uniformity across the full thickness of the target. Since moderate energy ion beams (~ 0.3 MeV/amu) can be useful tool for WDM physics*, we propose WDM generation using Direct Plasma Injection Scheme (DPIS). In the DPIS, laser ion source is connected to the Radio Frequency Quadrupole (RFQ) linac directly without the beam transport line. The discussions of DPIS for WDM are presented.
* L. R. Grisham, Physics of Plasmas, 11, 5727 (2004).
RCNP, Osaka
The RCNP accelerator cascade consists of an injector Azimuthally Varying Field (AVF) cyclotron (K=140) and a ring cyclotron (K=400). It provides ultra-high-quality beams and moderately high-intensity beams for a wide range of research in nuclear physics, fundamental physics, applications, and interdisciplinary fields. The maximum energy of protons and heavy ions are 400 and 100 MeV/u, respectively. Experimental apparatuses are used like a pair spectrometer, a neutron time of flight facility with a 100 m long tunnel, a radioactive nuclei separator, a super-thermal ultra cold neutron (UCN) source, a white neutron source, and a RI production system for nuclear chemistry. Such ultra high resolution measurements as dE/E = 5x10-5 are routinely performed with the Grand-Raiden spectrometer by utilizing the dispersion matching technique. The UCN density was observed to be 15 UCN/cm3 at the experimental port at a beam power of 400 W. Some topics on the research are discussed in the talk.
KEK, Ibaraki
Nagaoka University of Technology, Nagaoka, Niigata
Sokendai, Ibaraki
Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture
KEK digital accelerator (DA) capable of accelerating all species of ion* is an induction synchrotron employing no large scale injectors. At the beginning of its operation, Ar ions from the ECR ion source (ECRIS) embedded in the 200 kV high voltage terminal (HVT) are directly injected into KEK-DA though the low energy BT line (LEBT). The permanent magnet ECRIS was assembled at KEK. Its characteristics such as a charge-state spectrum, emittance, and intensity are presented. The 200 kV HVT has been also assembled at KEK. Its voltage stability in the pulse mode operation, where a plasma of 1 msec is created by x-band microwaves at 10 Hz, is discussed. The LEBT consists of the Eintzel lens, momentum analyzer, B magnets with edge focusing, electrostatic chopper**, and a combination of Q magnets. In the upper LEBT from the ion extraction hall to the entrance of the analyzer, possible charge-state ions are contaminated in the space-charge limit and beam focusing is realized through the Eintzel lens and tandem acceleration gaps. In the lower LEBT from the analyzer to the KEK-DA injection point, the lattice has been optimized so as to meet optics matching at the injection point.
*K. Takayama, J. of Appl. Phys. 101 063304(2007), "KEK digital accelerator for material and biological sciences" in this conference
**T.Adachi, "Injection and extraction system" in this conference
Kyoto ICR, Uji, Kyoto
We aim to develop a small and high intensity proton source for a compact accelerator based neutron source. Because this proton source shall be located close to RFQ for simplification, ratio of H+ to molecular ions such as H2+ or H3+ must be large. Therefore, we selected an ECR ion source with permanent magnets as small and high intensity ion source. ECR ion sources can provide high H+ ratio because of their high plasma temperature. Using permanent magnets makes the ion source small and running cost low. Because there is no hot cathode, longer MTBF is expected. Usually, gas is fed into ion sources continuously, even if ion sources run in pulse operation mode. But, continuous gas flow doesn't make vacuum in good level. So, we decided to install pulse gas valve directly to the plasma chamber. Feeding the gas only when the ion source is in operation reduces the gas load to the evacuation system and the vacuum level can be kept high. Up to now, we developed the first and second model of the ion source. And the research is being conducted using the second model. Recent experimental results will be presented.
Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova
INFN/LNL, Legnaro (PD)
GREPHE/LAPLACE, Toulouse
The thermonuclear fusion experiment ITER, requires 33 MW of auxiliary heating power from two Neutral Beam Injectors (NBI), each of them providing 40 A of negative deuterium ions. The EU activities oriented to the realisation of the electrostatic accelerator comprise the construction in Padova of SPIDER, a facility devoted to the optimisation of the beam source. SPIDER parameters are: 100 keV acceleration, 40/60 A (deuterium/hydrogen) current. For the optimised SPIDER accelerator the present contribution provides a characterisation of secondary particles, which include electrons produced by impact of ions on grid surfaces, stripped from negative ions inside the accelerator, and produced by ionisation of the background gas, and the corresponding positive ions. Currents and heat deposited on the various grids and spatial distribution by secondaries will be described. It is found that most of the heat loads on the accelerator grids is due to electrons; moreover the features of secondaries exiting the accelerator and back-streaming towards the source will be presented. The results will be compared with old investigations concerning the NBI 1 MeV accelerator.
BNL, Upton, Long Island, New York
We report recent progresses on analytical studies of Coherent Electron Cooling. The phase space electron beam distribution obtained from the 1D FEL amplifier is applied to an infinite electron plasma model and the electron density evolution inside the kicker is derived. We also investigate the velocity modulation in the modulator and obtain a closed form solution for the current density evolution for infinite homogeneous electron plasma.
HU/AdSM, Higashi-Hiroshima
The University of Tokyo, Institute of Physics, Tokyo
MPQ, Garching, Munich
RIKEN, Wako, Saitama
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima
Tokyo University of Science, Tokyo
In Antiproton Decelerator (AD) at CERN, unique low energy antiproton beams of 5.6 MeV have been delivered for physics experiments. Furthermore, the RFQ decelerator (RFQD) dedicated for Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) collaboration enables the use of 100 keV pulsed antiproton beams for experiments. What is more, Mono-energetic Ultra Slow Antiproton Source for High-precision Investigations (MUSASHI) in ASACUSA can produce antiproton beams with the energy of 100 ~ 1000 eV. Since the successful extraction of 250 eV antiproton beams reported in 2005, continuous improvements on beam quality and equipments have been conducted. Here, the basic properties of a tank circuit attached to MUSASHI trap are reported. Signals from a tank circuit provide information on the trapped antiprotons, as Shottky signals do for high energy beams in accelerators. In fact, it is known that this kind of trap-based beams are physically equivalent with those in a FODO lattice. Monitoring the tank circuit signals will be useful for on-line handling of the low energy antiproton beams from MUSASHI.
JAEA, Rokkasho, Kamikita, Aomori
NIFS, Gifu
Tohoku University, School of Engineering, Sendai
Doshisha University, Graduate School of Engineering, Kyoto
We propose a negative ion beam probe system as a new scheme to diagnose beam profile of high power positive ion beams. Two RF linacs of IFMIF have to drive the neutron source by providing continuous-wave (CW) positive deuterium ion beams with the intensity of 125 mA each at the beam energy of 40 MeV. During the CW beam operations, the extreme intensity of the beam and the severe radiation levels make the beam diagnostics with conventional techniques in the transport lines terribly difficult. A beam of negative ions liable to lose the additional electron at the occasion of impact with a high energy particle can work as a probe to measure the positive ion beam profile. On possible configuration to achieve high intensity beam profile measurement is to inject a negative ion probe beam into the target beam perpendicularly, and measure the attenuation of the negative ion beam by beam-beam interaction at each position. We have started an experimental study for the proof-of-principle of the new beam profile monitoring system. The paper presents the status quo of this beam profile monitor system development and the prospects to apply the system to the IFMIF beam line controls.
ITEP, Moscow
Application of a plasma lens to focusing of ion beams has a number of essential advantages. It is important that the focusing capabilities of the lens depend on the stage of plasma development. Under certain conditions a magnetic field is linear, that allow to focus the beam to a very small spot. In other conditions, the magnetic field is nonlinear, that allow formation of hollow and other beam structures. Hollow cylinder-shaped beams of high energetic heavy ions are efficient drivers for implosion targets to create matter in a highly compressed state. The work deals with the study the possibility of using a plasma lens to transformation the density distribution of ions in the beam. Calculations and measurements were performed for a C6+ and Fe26+ beams of 200 MeV/a.u.m. energy. The obtained results and analysis are reported.
Saint-Petersburg State University, Saint-Petersburg
LETI, Saint-Petersburg
We describe both analytically and numerically beams radiation in presence of media which can be realized as modern metamaterials. In particular, effects of reversed Cherenkov radiation (RCR)* and reversed Cherenkov-transition radiation (RCTR)** are considered. These phenomena can be used for detection of charged particles and diagnostics of beams. Earlier we noted some useful properties of radiation in the case of the boundary between an ordinary medium and an isotropic left-handed metamaterial (LHM)*. Now we continue to analyze prospects of use of LHM for beam diagnostics. Moreover, we investigate RCR and RCTR in the case of certain anisotropic materials with properties being similar to properties of LHM. The useful features are reversed character of radiation and, particularly, existence of two thresholds for RCTR (lower threshold and upper one). This fact allows selection of particles (or beams) with energy in some predetermined range. The specific radiation patterns (having two or three lobes in anisotropic metamaterial) can be useful for particle energy measurement as well.
* Z.Y. Duan, B.-I. Wu, S. Xi, H.S. Chen., M. Chen, Progress in Electromagn. Research, v.90, p.75 (2009).
** S.N. Galyamin, A.V. Tyukhtin, A. Kanareykin, P. Schoessow, PRL, v.103, p.194802 (2009).
Saint-Petersburg State University, Saint-Petersburg
Euclid TechLabs, LLC, Solon, Ohio
We consider the particles energy measurement method offered in our papers (footnotes). It is based on measurement of the modes frequencies in waveguide loaded with certain material. For this method, the modes frequencies must depend on the particles energy strong enough. Here we discuss the problem of selection of materials for this technique. It is shown that high precision of energy measurement can be reached by use of the system of specific parallel conductors. The approximate analytical approach for obtaining effective permittivity of such structure is developed. It is shown that selection of parameters of the structure allows ruling an effective permittivity characterized by both frequency dispersion and spatial one. The structure is simple enough for production. It allows measuring the particles energy for different predetermined ranges. The other ways of realization of the method are discussed as well. One of them consists in use of thin layer of ordinary dielectric. Selection of the layer thickness and dielectric constant allows obtaining strong enough dependence of frequency on Lorentz-factor in the relatively wide range.
A.V. Tyukhtin, S.P. Antipov, A. Kanareykin, P. Schoessow, PAC07, p.4156;
A.V. Tyukhtin, EPAC08, p.1302;
A.V. Tyukhtin, Technical Physics Letters, v.34, p.884 (2008), v.35, p.263 (2009).
USTRAT/SUPA, Glasgow
University of Dundee, Nethergate, Dundee, Scotland
TUE, Eindhoven
UAD, Dundee
The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme at the University of Strathclyde is developing laser-plasma wakefield accelerators to produce high energy, ultra-short duration electron bunches as drivers of radiation sources. Coherent emission will be produced in a free-electron laser by focussing the electron bunches into an undulator. To achieve net gain, a high peak current, low energy spread and low emittance are required. A high intensity ultra-short pulse from a 30 TW Ti:sapphire laser is focussed into a helium gas jet to produce femtosecond duration electron bunches in the range of 80 - 200 MeV. Beam transport is monitored using a series of Lanex screens positioned along the beam line. We present measurements of the electron beam energy spread as low as 0.7% (at 90 MeV) obtained using a high resolution magnetic dipole spectrometer. We also present pepper-pot measurements of the normalised transverse emittance of the order of 1 pi mm mrad. With further acceleration to 1 GeV, the beam parameters indicate the feasibility of a compact X-ray FEL with a suitable undulator.
JAI, Oxford
Although the pepper-pot method has been used for decades at low energy to measure the transverse emittance of particles sources, it has only been extended to high energy very recently. We report on some of the recent measurements done at high energy (several hundred MeVs) and discuss the practical consideration of such measurements. We show demonstrate that an extended pepper-pot does not significantly affect the phase space of the beam and thus provides a valid transverse emittance measurement.
ANL, Argonne
Peta-scalable software packages for beam dynamic simulations are being developed and used at the Argonne Leadership Computing Facility. The standard Particle-In-Cell (PIC) method and direct Vlasov solvers in 4 dimensions have been developed and benchmarked with respect to each other. Both of them have been successfully run on 32 thousands processors on BG/P at Argonne National Laboratory. Challenges and prospects of developing Vlasov solvers in higher dimensions will be discussed. Several scalable Poisson solvers have been developed and incorporated with these software packages. Domain decomposition method has been used for the parallelization. In the future developments, these algorithms will be applied to hundreds of thousands processors for peta-scale computing. These software packages have been applied for the design of accelerators, and some large scale simulations will be shown and discussed.
UFPel, Pelotas
IF-UFRGS, Porto Alegre
Beams of charged particles usually reach their stationary state by the development of a halo. Halo formation in charged beams is in fact a macroscopic transcription of microscopic instabilities acting inside the beam and upon its constituent particles. In previous works, investigations have been carried out to understand the role of the initial envelope mismatch and of magnitude of inhomogeneity in the beam route to the equilibrium. Although in that works the action of the mentioned instabilities has been studied individually, it is clear that in real implemented beams both act together. In this sense, the main purpose of this work is to generalize previous models, considering now concomitantly the effects of the envelope mismatch and of the inhomogeneity. As a final product of the investigation, a particle-core model for beam constituent particles is presented. The agreement with full self-consistent N-particle beam numerical simulations is satisfactory and the results provided by the model seem to be more compatible with that would be expected experimentally.
Hiroshima University, Higashi-Hiroshima
Osaka University, Graduate School of Science, Osaka
HU/AdSM, Higashi-Hiroshima
Space charge effects due to the strong Coulomb interactions expected in high intensity accelerator beams result in undesirable beam degradation and radio-activation of the vacuum tubes through halo formations. Various space charge effects have been studied intensively with particle simulations. This is partly because the analytical formulation of the nonlinear evolution in high intensity beams is not possible in general cases. And the systematic study of space charge effects with the real accelerators is not feasible. Although the development of computation environment is outstanding, some approximations are still necessary so far. Thus, it was proposed to use solenoid traps and linear Paul traps for investigating some properties of space charge dominated beams. The key idea is that the charged particles in these traps are physically equivalent with a beam in a FODO lattice. Some experimental results have been reported with the use of Paul traps. Here, a solenoid trap with a beam imaging system composed of a charge coupled device camera and a phosphor screen was employed to study the mismatch induced oscillations of a space charge dominated beams.
HU/AdSM, Higashi-Hiroshima
Hiroshima University, Higashi-Hiroshima
LLNL, Livermore, California
S-POD (Simulator for Particle Orbit Dynamics) is a tabletop, non-neutral plasma trap system developed at Hiroshima University for fundamental beam physics studies. The main components of S-POD include a compact radio-frequency quadrupole trap, various AC and DC power supplies, a vacuum system, a laser cooler, several diagnostics, and a comprehensive computer control system. A large number of ions, produced through the electron bombardment process, are captured and confined in the RFQ trap to emulate collective phenomena in space-charge-dominated beams traveling in periodic linear focusing lattices. This unique experiment is based on the isomorphism between a one-component plasma in the laboratory frame and a charged-particle beam in the center-of-mass frame. We here employ S-POD to explore the coherent betatron resonance instability which is an important issue in modern high-power accelerators. Ion loss behaviors and transverse plasma profiles are measured under various conditions to identify the parameter-dependence of resonance stopbands. Experimental observations are compared with PIC simulation results obtained with the WARP code.
PPPL, Princeton, New Jersey
To achieve high focal spot intensities in ion-beam-driven high energy density physics and heavy ion fusion applications, the ion beam must be compressed longitudinally by factors of ten to one hundred before it is focused onto the target. The longitudinal compression is achieved by imposing an initial velocity profile tilt on the drifting beam, and allowing the beam to compress longitudinally until the space-charge force or the internal thermal pressure stops the longitudinal compression of the charge bunch. In this paper, the problem of longitudinal drift compression of intense charged particle beams is analyzed analytically and numerically for the two important cases corresponding to a cold beam, and a pressure-dominated beam, using a one-dimensional warm-fluid model describing the longitudinal beam dynamics. The hodograph transformation is used to transform the nonlinear fluid equations into a single, second-order, linear partial differential equation (PDE). The general solution of this equation describing the intense beam system with stagnation point is analyzed and illustrated with several examples.
INFN-Ferrara, Ferrara
UNIFE, Ferrara
IHEP Protvino, Protvino, Moscow Region
We present an analytical model to calculate the physical quantities of interest experienced by relativistic particles in their motion aligned with periodic complex atomic structures. Classical physics equations and the expansion of periodic functions as a Fourier series have been used for the calculation. This method allows calculating the contribution from all the planes and axes inside the crystal, in contrast to other simulation codes for which the motion is evaluated only on nearest neighbors atomic strings. Based on the calculation technique we have developed the "ECHARM" program, which allows calculating one- and two- dimensional averaged physical quantities of interest. The calculation holds for the main axes of any orthorhombic and tetragonal structures and for any orientation in the cubic structure. To underline the capability of the program, complex structures such as zeolites have been worked out. Based on the "ECHARM" code, simulation of the relativistic particle motion within complex structures has been developed. With this code it is possible to simulate the motion in bent crystal to study planar and axial channeling volume reflection.
BNL, Upton, Long Island, New York
PVI, Oxnard
Institute of High Current Electronics, Tomsk
Electron clouds, which can limit machine performance, have been observed in many accelerators including RHIC at BNL. They can be suppressed by low secondary electron yield beam pipe surfaces. Additional concern for the RHIC machine, whose vacuum chamber is made from relatively high resistivity 316LN stainless steel, is high wall resistivity that can result in unacceptably high ohmic heating for superconducting magnets. The high resistivity can be addressed with a copper (Cu) coating; a reduction in the secondary electron yield can be achieved with a TiN or amorphous carbon (a-C) coating. Applying such coatings in an already constructed machine is rather challenging. We started developing a robotic plasma deposition technique for in-situ coating of long, small diameter tubes. The technique entails fabricating a device comprising of staged magnetrons mounted on a mobile mole for deposition of about 5 μm (a few skin depths) of Cu followed by about 0.1 μm of a-C. As a first step, a 15-cm Cu cathode magnetron is being designed and fabricated, after which, 30-cm long sample of the RHIC pipe are to be Cu coated. Deposition rates and affects on RF resistivity are to be measured.
Tech-X, Boulder, Colorado
Data organization of simulations outputs differs from application to application. This makes development of uniform visualization and analysis tools difficult and impedes comparison of simulation results. VizSchema is an effort to standardize metadata of HDF5 format so that the subsets of data needed to visualize physics can be identified and interpreted by visualization tools. Based on this standard, we developed a powerful VisIt-based visualization tool. It allows a uniform approach for 3D visualization of large data of various kinds (fields, particles, meshes) from the COMPASS suite for SRF cavities and laser-plasma acceleration. In addition, we developed a specialized graphical interface to streamline visualization of VORPAL outputs and submit remote VORPAL runs. In this paper we will describe our approach and show some visualizations results.
TUB, Beijing
Tsinghua University, Beijing
HU/AdSM, Higashi-Hiroshima
LBNL, Berkeley, California
JAEA/TARRI, Gunma-ken
During the beam crystallization process, the main heating source is Intra-beam scattering (IBS), in which the Coulomb collisions among particles lead to a growth in the 6D phase space volume of the beam. The results of molecular dynamics (MD) simulation have shown an increase of heating rate as the temperature is increased from absolute zero, but then a peak in the heating rate, and subsequent decrease with ever increasing temperature*. This phenomenon has been carefully studied by Y. Yuri, H. Okamoto, and H. Sugimoto**. On the other hand, in the traditional IBS theory valid at high temperatures, heating rate is monotonically increasing as the temperature becomes lower***. In this paper we attempt to understand the "matching" at low temperatures between the MD results and traditional IBS theory, by including many body effects in the traditional IBS theory. In particular the Debye shielding is included. We shall present how the traditional theory is modified by shielding, and show how this effect improves the "matching" with the results from MD.
* J. Wei, H. Okamoto, and A. Sessler, Phys. Rev. Lett. 80, 2606
** Y.Yuri, H. Okamoto, and H. Sugimoto, J. Phys. Soc. Jpn. 78, 124501
***A. Piwinski, Lect. Notes Phys. 296, 297 (1988)
LBNL, Berkeley, California
The propagation of TE waves is sensitive to the presence of an electron cloud primarily through phase shifts generated by the altered dielectric function, but can also lead to polarization changes and other effects, especially in the presence of magnetic fields. These effects are studied theoretically and also through simulations using WARP-POSINST. Full electromagnetic simulations are performed for CesrTA parameters, and used as a benchmark for simplified phase shift estimates that are also implemented in WARP/POSINST. Nonlinear effects such as electron heating are also examined.
ODU, Norfolk, Virginia
JLAB, Newport News, Virginia
Plasma based surface modification provides an excellent opportunity to eliminate non-superconductive pollutants in the penetration depth region of the SRF cavity surface and to remove mechanically damaged surface layer improving surface roughness. We have demonstrated on flat samples that plasma etching in Ar/Cl2 of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. The geometry of SRF cavities made of bulk Nb defines the use of asymmetric RF discharge configuration for plasma etching. In a specially designed single cell cavity with sample holders, discharge parameters are combined with etched surface diagnostics to obtain optimum combination of etching rates, roughness and homogeneity in a variety of discharge types, conditions, and sequences. The optimized experimental conditions will ultimately be applied to single cell SRF cavities.
ODU, Norfolk, Virginia
JLAB, Newport News, Virginia
The tomographic reconstruction of local plasma parameters for nonequilibrium plasma sources is a developing approach, which has a great potential in understanding the fundamental processes and phenomena during plasma processing of SRF cavity walls. Any type of SRF cavity presents a plasma rector with limited or distorted symmetry and possible presence of high gradients. Development of the tomographic method for SRF plasma analysis consists of several steps. First, we define the method based on the inversion of the Abel integral equation for a hollow spherical reactor. Second step is application of the method for the actual elliptical cavity shape. Third step consists of study of the effects of various shapes of the driven electrode. Final step consists of testing the observed line-integrated optical emission data. We will show the typical results in each step and the final result will be presented in the form of correlation between local plasma parameter distributions and local etching characteristics.
Fermilab, Batavia
Muons, Inc, Batavia
IIT, Chicago, Illinois
ANL, Argonne
University of Chicago, Chicago, Illinois
Voss Scientific, Albuquerque, New Mexico
A high pressurizing hydrogen gas filled RF cavity has a great potential to apply for muon colliders. It generates high electric field gradients in strong magnetic fields with various conditions. As the remaining demonstration, it must work under high radiation conditions. A high intensity muon beam will generate a beam-induced electron swarm via the ionization process in the cavity. A large amount of RF power will be consumed into the swarm. We show the recent non-beam test and discuss the electron swarm dynamics which plays a key role to develop a high pressure RF cavity.
JAEA, Kyoto
Laser wakefield acceleration (LWFA) is regarded as a basis for the next-generation of charged particle accelerators. In experiments, it has been demonstrated that LWFA is capable of generating electron bunches with high quality: quasi-monoenergetic, low in emittance, and a very short duration of the order of ten femto-seconds. Such femtosecond bunches can be used to measure ultrafast phenomena. In applications of the laser accelerated electron beam, it is necessary to generate a stable electron beam and to control the electron beam. A 40 fs laser pulse with the energy of 200 mJ is focused onto a supersonic gas jet. We succeed to generate a stable electron beam by using a Nitrogen gas target. The profile of the electron beam can be manipulated by rotating the laser polarization. When we use a S-polarized laser pulse, a 20 MeV electron beam is observed with an oscillation in the image of the energy spectrum. From the oscillation, the pulse width of the electron beam is calculated to at most a few tens fs. The direction of the electron beam can be controlled by changing the gas-jet position. The self-injected electron beam can be controlled by the control of the laser and gas jet.
ITEP, Moscow
GSI, Darmstadt
Terra Watt Accumulator project (ITEP-TWAC) is aiming the accumulation of an ion beam accelerated up to 0.7 GeV/u in a storage ring providing intensity of heavy ions up to 10 power 12 particles per pulse for experiments on heavy ion beam-plasma interaction. For advanced experiments on high energy density physics the hollow cylindrical target is needed. A new method for RF rotation of the ion beam is applied for reliable formation of the hollow cylindrical beam. A principle of fast beam rotation by using a system of the multi-cell RF deflectors is considered in this paper. A four-cell H-mode deflecting cavity operating at the frequency of 298 MHz has been developed; similar 1.5 m long cavities being applied for both x- and y- directions. The shape of the deflecting electrodes has been optimized in order to provide the uniform deflection over the whole aperture taking into account both electric and magnetic components of the RF field. A deflecting system and a focusing quadrupole triplet applied to the beam with the energy of 450 MeV/u and normalized transverse emittance of 10*pi mrad*mm may form the quasi-hollow configuration with the inner radius up to 1.5 mm and thickness of 1 mm.
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
LETI, Saint-Petersburg
Ceramics Ltd., St. Petersburg
Fermilab, Batavia
The BST based ferroelectric-oxide compounds have been found as suitable materials for a fast electrically-controlled RF switches and phase shifters that are under development for accelerator applications in X, Ka and L - frequency bands. The BST(M) material (BST ferroelectric with Mg-based additives) allows fast switching and tuning in vacuum and in air both; switching time of material samples < 10 ns has been demonstrated*. One of the problems related to accelerator application of BST ferroelectric is its high dielectric constant. Decreasing the permittivity however is usually strongly correlated with a decrease in the tunability (k(E)=ε(0)/ε(E)) of ferroelectrics. The use of linear dielectric inclusions in BST ceramics could result in significant suppression of the mentioned k(E) dependence, with the best case being that the tunability vs. ε decrease could be unchanged. On the basis of our measurements we report here two unusual phenomena observed**: (i) the increase both the dc and the dynamic tunability with a decrease of the dielectric constant; (ii) the dynamic tunability was observed to exceed the static tunability at specific magnitudes of the applied field.
* A.Kanareykin et al, Proceedings PAC'09.
** A.Kozyrev et al Applied Physics Letters,v.95,p.012908,(2009).
Lucknow University, Lucknow
BARC, Mumbai
CBS, Mumbai
Nonlinear, high-amplitude plasma waves are excited in the wake of an intense laser pulse propagating in a cold plasma, providing acceleration gradients up to GeV/m. Linear analytic analyses have shown that the wakefield amplitude is optimal for a certain ratio of the pulse length and plasma wavelength*,**. Here we present results of simulation studies to optimize the nonlinear wakefield amplitudes. Variation in the laser pulse length is considered for maximizing amplitudes of wakefields generated by half-sine and Gaussian pulse profiles. Further, the advantages of using a transversely inhomogeneous plasma for the generation of the nonlinear wakefields are studied and compared with the homogeneous case.
* E. Esarey, P. Sprengle, J. Krall and A. Ting, IEEE Trans. Palsma Sci. 24, 252 (1996)
** L. M. Gorbunov and V. I. Kirsanov, Zh. Eksp. Teor. Fiz. 93, 509 (1987), Sov. Phys. JETP, 46, 290 (1988).
BARC, Mumbai
Lucknow University, Lucknow
CBS, Mumbai
We study electron acceleration by two laser pulses co-propagating one behind the other in a homogeneous plasma. We show, using one-dimensional simulations, that the wake amplitude can be amplified or diminished depending on the time delay between the two lasers, in agreement with linear analytic theory. We extend the study to the bubble regime using two-dimensional simulations. We find that the one-dimensional optimization holds in two dimensions also. Trapping and acceleration of quasi-monoenergetic electrons (up to around 300 MeV) is found in the bucket behind the second laser, even for low intensities, where there is no trapping with a single laser. Thus, this scheme could be very useful for achieving a desired accelerated energy with less intense lasers, or, equivalently, increasing the accelerated energy for a given laser intensity.
* G. Raj, A. K. Upadhyay, R. K. Mishra and P. Jha, Phys. Rev. ST Accel. and Beams 11, 071301 (2008).
JAEA, Ibaraki-ken
JAEA APRC, Ibaraki-ken
JAEA/Kansai, Kyoto
ILE Osaka, Suita
The pointing stability and the divergence of a quasi-monoenergetic electron bunch generated in a self-injected laser-plasma acceleration regime were investigated. Gas-jet targets have been irradiated with focused 40 fs laser pulses at the 4-TW peak power. A pointing stability of 2.4 mrad root-mean-square (RMS) and a beam divergence of 10.6 mrad (RMS) were obtained using argon gas-jet target for 50 sequential shots, while these values were about three times smaller than at the optimum condition using helium. In particular, the peak electron energy was 9 MeV using argon, which is almost three times lower than that using helium. This result implies that the formation of the wake-field is different between argon and helium, and it plays an important role in the generation of a electron bunch. This stabilization scheme is available for another gas material such as nitrogen. At nitrogen gas-jet target, the pointing stability is more improved to 1.4 times smaller (1.7 mrad (RMS)) than that in argon gas-jet target and the peak energy is increased to grater than 40 MeV. These results prove that this method not only stabilize the e-beam but also allows controlling the electron energy.
University of Tokyo, Tokyo
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa
We are studying the artificial injection of initial electrons into the wakefield for producing stable electron bunch (the charge is 100 pC, the energy stability is better than a few per cent). The objective of our research is to produce 100-keV class monochromatic X-ray pulses for measuring concentrations of nuclear materials in a reprocessing plant. A K-edge densitometry using monochromatic hard x-ray beams is one of the effective technique to measure concentrations of nuclear materials in a reprocessing solutions. An inverse Compton scattering process between an IR-laser beam of 800 nm and high-energy electron bunch of above 80 MeV makes it possible to deliver tunable monochromatic x-rays near K-absorption edges of nuclear materials of 115-129 keV. In order to use in a reprocessing plant, the equipment for the K-edge densitometry must be smaller than a compact car. The only solution to realize the compact system is to use a laser wakefield accelerator instead of a radio frequency linac. An ultra-short ten-TW laser pulse focused on a supersonic jet makes it possible to accelerate electrons up to 100 MeV in a plasma length of 2.5 mm.
KERI, Changwon
Using the nonlinear interaction between the high power laser and the plasma, we can generate strong acceleration field, called the laser wake field acceleration. The plasma density is very crucial to generate high energy electron. In this work, we studied the effect of the plasma density structure on the accelerated electron energy. We used 20 TW, 40 fs laser system to generate the plasma wakefield. A gas jet was used as a target. The plasma density was controlled by the back pressure of the gas nozzle and measured by the interferometer. The accelerated electron energy was measured using the electron energy spectrometer with 0.5 T magnet. The bunch charge was measured integrated charge transformer (ICT). When the plasma density is uniform, 2×1019 cm-3 we can generate 200 MeV electron beam with bunch charge 33 pC. The electron beam divergence was less than 5 degree. If there exists the downward density tramp, the electron energy is only 50 MeV. The PIC simulation also indicates that if there is density ramp structure, the electron is not accelerated well. In this presentation, the overall experimental and simulation results are presented.
APRI-GIST, Gwangju
In recent years, the laser-driven plasma wakefield acceleration has attracted much attention as it has a much higher acceleration gradient (>100 GeV/m) compared with the RF-based conventional accelerators. In the past, the supersonic gas jet method for plasma wakefield acceleration was widely used, but this method has a limitation in acceleration distance and energy because the focused laser beam is diffracted severely over a very short distance (~ a few mm range). To avoid the diffraction problem, a capillary plasma source can be used, where a high power laser beam can be guided over a long distance (~ a few cm range) by a parabolic plasma density profile in the capillary plasma channel. We have developed a gas-filled capillary plasma source for generation of GeV-level electron beams in collaboration with the University of Oxford team. In this presentation, the detailed test results and the near-future experimental plan for GeV-level e-beam generation are shown.
University of Michigan, FOCUS Center for Ultrafast Optical Science, Ann Arbor, Michigan
Recent experimental results will be discussed with regard to the use of the 300 TW, 30 fsec HERCULES laser system at the Center for Ultrafast Optical Science at Michigan to generate GeV range electron beams using Laser Wakefield Acceleration (LWFA). The electron beam quality is shown to be improved substantially using gas mixtures- causing an increase in beam charge and a decrease in emittance. The dynamics of the acceleration process are also determined by measurements of spatially resolved scattered laser radiation and the use of femtosecond optical probing techniques.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Penn State University, University Park, Pennsylvania
USC, Los Angeles, California
Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This uses of very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced ~2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Angstroms, or be used to permit 1.5 Angstrom operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.
INFN/LNL, Legnaro (PD)
In singly charged positive ion sources, the study of beam extraction is greatly simplified by the existence of a well defined place for plasma to beam transition, given by the well known Bohm criterion, where the ion flow speed equals the speed of sonic perturbation, known as Bohm speed. Most of the ion extraction simulation codes are implicity based on the concept of quasi neutrality in the plasma region, as limited by the Bohm criterion. In negative ion source the existence of an electron coextracted beam and of a magnetic filter makes the relevant speed less clear. Moreover there are several scale lengths to be considered: the Debye length, that is typically 0.01 mm, the electron and ion gyroradius, the H- scattering, absorbtion and production length. In the development of negative ion source for NBI injector for ITER, the production of H- at wall and the negative sheath so generated is also important. A critical evaluation of these regimes is obtained with 1D (one space dimension) models, mostly restricted to magnetic filter parallel to the extraction wall. Some remarks on 2D simulation codes is also given.
INFN/LNL, Legnaro (PD)
Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova
The development of neutral beam injectors (NBI) for tokamak like the ITER project and beyond requires high performance and huge negative ion sources (40 A of D- beam required); it was recently accepted that inductive plasma coupled (ICP) radiofrequency sources are the preferred option. It is therefore useful to have a moderate size source of modular design to test and verify both construction technologies and components and simulation codes; here the NIO1 design (60 kV, 9 beamlets of 15 mA H- each) and construction status are described. Source is assembled from disk shaped modules, for rapid replacement; the beamlets are arranged in 3 times 3 square matrix so that 90 degree rotation of modules is possible and allows to cross or to align the magnetic filters used in the source. The 2 MHz rf coil and the rf window are a simply replaceable module. Extensive rf absorption and magnetic coil simulations were performed. Related beam simulation and fast emittance scanner development are described elsewhere.
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
BNL, Upton, Long Island, New York
RIKEN Nishina Center, Wako
In a laser ion source, a high power pulsed laser shot focused on a solid state target produces laser ablation plasma. This plasma has initial velocity towards the normal direction of the target and simultaneously expands three dimensionally. Since charge state distribution, velocity distribution and plasma temperature strongly depends on laser power density, power density is one of the important parameter to the angular distribution of plasma. Angular distribution of expanding plasma was measured by changing laser power density. Details of the experiment will be shown in the paper.
RCNP, Osaka
The upgrade program of the AVF cyclotron is in progress since 2004 at Research Center for Nuclear Physics (RCNP), Osaka Univ., for improving the quality, stability and intensity of accelerated beams. An 18 GHz superconducting ECRIS has been installed to increase beam currents and to extend the variety of ions, especially for highly charged heavy ions which can be accelerated by RCNP cyclotrons. The production development of several ion like B, C ~ Xe by gas mixing or MIVOC has been performed. In order to extend the variety of ions more, metal viper or spatter system has also been installed to 10GHz NEOMAFIOS with minimum modifications. The details of these recent developments will be presented.
The University of Tokyo, Institute of Physics, Tokyo
HU/AdSM, Higashi-Hiroshima
MPQ, Garching, Munich
RIKEN, Wako, Saitama
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima
Tokyo University of Science, Tokyo
University of Tokyo, Chiba
KEK, Tsukuba
The ASACUSA collaboration at CERN has been developed a unique Mono-energetic Ulta-Slow Antiproton beam Source for High-precision Investigation (MUSASHI) for collision studies between antiproton and atoms at very low energy region, which also used as an intense ultra-low energy antiproton source for the synthesis of antihydrogen atoms in order to test CPT symmetry. MUSASHI consists of a multi-ring electrode trap housed in a bore surrounded by a superconducting solenoid, which works with a sequential combination of the CERN Antiproton Decelerator and the Radio-Frequency Quadrupole Decelerator. GM-type refrigerators were used to cool the solenoid and also the bore at 4K to avoid losses of antiprotons with residual gasses. Up to 1.8 millions of antiprotons per one AD cycle were successfully trapped and cooled. MUSASHI achieved to accumulate more than 12 millions of cold antiprotons by stacking several AD shots. Such cooled antiprotons were extracted as 150 or 250eV beams with various bunch lengths from 2 micoroseconds to 30 seconds long, whose energy width was the order of sub-eV. The beam intensity was enhanced by a radial compression technique for the trapped antiproton cloud.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
The operation of the RHIC facility at BNL and the Electron Ion Colliders (EIC) under development at Jefferson Laboratory and BNL need high brightness ion beams with the highest polarization. Charge exchange injection into a storage ring or synchrotron and Siberian snakes have the potential to handle the needed polarized beam currents, but first the ion sources must create beams with the highest possible polarization to maximize collider productivity, which is proportional to a high power of the polarization. We are developing one universal H-/D- ion source design which will synthesize the most advanced developments in the field of polarized ion sources to provide high current, high brightness, ion beams with greater than 90% polarization, good lifetime, high reliability, and good power efficiency. The new source will be an advanced version of an atomic beam polarized ion source (ABPIS) with resonant charge exchange ionization by negative ions. An integrated ABPIS design will be prepared based on new materials and an optimized magnetic focusing system. Polarized atomic and ion beam formation, extraction, and transport for the new source will be computer simulated.
Muons, Inc, Batavia
ORNL, Oak Ridge, Tennessee
Development of novel modifications of H- source designs is proposed. The new source will be an advanced version of a Penning DT SPS (Dudnikov-Type Penning Surface Plasma Source) which will generate brighter beam in noiseless discharge, deliver up to 20 mA average current with better electrode cooling using new materials, and have longer lifetime, fast beam chopping capability, and reduced cesium loss.
Muons, Inc, Batavia
UMD, College Park, Maryland
ORNL, Oak Ridge, Tennessee
In this project we are developing an RF H- surface plasma source which will synthesize the most important developments in the field of negative ion sources to provide high pulsed and average current, high brightness, good lifetime, high reliability, and higher power efficiency. We describe two planned modifications to the present SNS external antenna source in order to increase the plasma density near the output aperture: 1) replacing the present 2 MHz plasma-forming solenoid antenna with a 13 MHz saddle-type antenna and 2) replacing the permanent multicusp magnetic system with a weaker electro-magnet. Progress of this development will be presented.
Muons, Inc, Batavia
LBNL, Berkeley, California
Induction linear accelerators are featured in accelerator-based research currently supported by the Office of Fusion Energy Sciences. Over the next few years, the research will concentrate on developing intense ion sources and on studying the physics of spatial compression, neutralized transport, and focusing of the beam. The large diameter of lithium alumino-silicate ion emitters for large currents represents the current state of the art for emission densities of 1-1.5 mA/cm2. Also, operating temperatures of the surface are limited by the temperature of alumina-potted heater packages. We propose a novel system for increasing the emission of lithium ions from β-eucryptite through modification of the surface morphology by sputter etching with argon plus other gases. The resulting local field enhancement will increase the ion emission over that of a microscopically flat surface. In addition, a free-standing graphite heater assembly will be used to increase the temperature of the surface of the emission source.
BNL, Upton, Long Island, New York
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
The Laser Ion Source is an efficient method for generating heavy ions for acceleration. The output produces high current and high charge-state beams from almost any type of elemental species. Using the Laser Ion Source apparatus, we consider improving the efficiency of this method by heating the target prior to laser irradiation. Prior deposition of any thermal energy into the target could add with the energy being delivered by the pulsed laser to produce higher current beams. These beams could be composed of higher charge-state ions and/or an increased net number of ions. We investigate by using a retrofitted heater to heat the target to a variety of high temperatures and subsequently analyze the produced beam.
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
BNL, Upton, Long Island, New York
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
A laser ion source can provide high-current highly-charged ions with a simple structure. Previously we have demonstrated acceleration of >60 mA carbon and aluminum ion beams using a direct plasma injection scheme. However, it was not easy to control the ion pulse width. Especially to provide longer ion pulse, a plasma drift length which is the distance between laser target and extraction point, has to be extended and the plasma is diluted severely. We apply a solenoid field to prevent reduction of ion density at the extraction point. A solenoid field of a few hundred Gauss enhanced the ion density up to 40 times. We present these results, including details of the solenoidal field effects on the expanding laser plasma.
IF-UFRGS, Porto Alegre
In this work the nonlinear relativistic propagation of intense lasers in plasmas is investigated. It is known that, under appropriate conditions, the ponderomotive force associated with the laser envelope can excite large amplitude electron waves (wakefields), which can be of interest for particle acceleration schemes. Numerical solutions showing some of the possible behaviors of this system are presented and compared to analytical ones, obtained through an effective potential approach using a one-dimensional Lagrangian formalism.
Indian Institute of Technology Delhi, Plasma Physics Group, New Delhi
Indian Institute of Technology Delhi, New Delhi
A Gaussian whistler pulse is shown to cause ponderomotive acceleration of electrons in a plasma when the peak whistler amplitude exceeds a threshold value. The threshold amplitude decreases with the ratio of plasma frequency to electron cyclotron frequency ωp / ωc. However above the threshold amplitude the acceleration energy decreases with ωp / ωc. The electrons gain velocities about twice the group velocity of the whistler. For acceleration of electrons one requires a whistler pulse of ω > ωc/2. It is seen that to enhance the energy gain the value of peak laser amplitude should be above a threshold value.
JAEA, Kyoto
APRI-GIST, Gwangju
ILE Osaka, Suita
Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa
High-intensity laser and thin-foil interactions produce high-energy particles, hard x-ray, high-order harmonics, and terahertz radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical applications. We have performed the high intensity laser-matter interaction experiments using a thin-foil target irradiated by Ti:sapphire laser (J-KAREN) at JAEA. In this laser system, the pulse duration is 40 fs (FWHM). The laser beam is focused by an off-axis parabolic mirror at the target. The estimated peak intensity is ~5x1019 W/cm2. We have developed on-line real time monitors such as a time-of-flight proton spectrometer which is placed behind the target and interferometer for electron density profile measurement of preformed plasma. We observed the maximum proton energy of ~7 MeV.
National University of Defense Technology, Changsha, Hunan
Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang
Center for Optical Research and Education, Utsunomiya University, Utsunomiya
National University of Defense Technology, Graduate School, Changsha
National University of Defense Technology, Parallel and Distributed Processing, Changsha
Ruhr-Universität Bochum, Bochum
We have proposed a scheme for the generation of collimated proton beams from the interaction of an ultra-intense laser pulse with a rear hole target, which is studied by a 2.5D particle-in-cell (PIC) code PLASIM. When an ultraintense short laser pulse irradiates on such a target, the hot electrons will expand fast into the hole from the inner surfaces of the hole, and strong longitudinal sheath electric field and transverse electric field are produced. However, the plasma in the corners expand slower and be compressed strongly, and then a strong plasma jet is sprayed out from the corner with very high speed, which is just like what happened in armor piercing bullet due to the cumulative energy effect. The two jets extend into the hole and focus along the axis of the hole. At last, a high quality collimated proton beam can be obtained near the end of the hole along the propagation axis. It's found that the beam can propagate over a much longer distance without divergence. The effect of the hole diameter on the collimated proton beam is also investigated. Such target may serve as an important source for collimated proton beam in practical applications.
UCLA, Los Angeles
PBPL, Los Angeles
Manhattanville College, Purchase, New York
Pyroelectric crystals, which produce large surface electric fields during heating and cooling, have been proposed as a mechanism for constructing a stand-alone electron beam source. We report on experimental tests of this concept, using a variety of field emission tips combined with a pyroelectric crystal to produce a low-energy electron beam during thermal cycling. The mechanism is suitable for generating very small electron bunches, with energies up to tens of kilovolts, for use in microaccelerator structures.
MPI-P, München
CERN, Geneva
BINP SB RAS, Novosibirsk
HHUD, Dusseldorf
Proton driven plasma wakefield acceleration holds promise to accelerate a bunch of electrons to the energy frontier in a single acceleration channel. To verify this novel idea, a demonstration experiment is now being planned. The idea is to use the high energy proton bunches from the Super Proton Synchrotron (SPS) at CERN, to shoot them into a plasma cell and drive large amplitude of plasma wake. The interactions between the plasma and protons are simulated and the results are presented in this paper.
MPI-P, München
A high energy, intense and short proton bunch can be employed to excite an interesting plasma wakefield for the electron beam acceleration. To excite a large amplitude of plasma wave, a short driver is thus required. In this paper, several proton bunch compression scenarios are analyzed. A magnetic bunch compressor is designed to compress the SPS proton beam for the demonstration experiment at CERN. The simulation results of bunch compression are given.
Center for Optical Research and Education, Utsunomiya University, Utsunomiya
Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang
National University of Defense Technology, Graduate School, Changsha
Shanghai Jiao Tong University, Shanghai
National University of Defense Technology, Changsha, Hunan
Ruhr-Universität Bochum, Bochum
National University of Defense Technology, Parallel and Distributed Processing, Changsha
Energetic protons of tens MeV or more produced by intense lasers have been observed in recent experiments and numerical simulations. Meanwhile, significant efforts have been made to improve the proton beam quality *,**,***. For most applications, it is important to improve the quality of the proton beam both during the production and during the propagation. Some schemes are proposed to improve the quality of the proton beam both during the production form the laser plasma interaction and during the propagation. The physics is investigated by 2D3V and 3D particle-in-cell codes PLASIM and PLASIM3D. In this paper, we propose to use an umbrella-like target to accelerate, and collimate protons. It is found that high intensity collimated MeV-proton beams can be produced ****. We also propose a scheme to generate quasi-monoenergetic proton beam from the interactions of an ultra-intense laser pulse and a thin tailored hole target. Particle simulation shows that a monoenergetic proton beam is generated from the hole. The propagation of a proton beam both in vacuum and in a plasma is also studied. Compared with the propagation in vacuum, the proton beam quality can be improved obviously.
* T. Toncian, et al. Science 312, 410(2006).
** B. M. Hegelich, et al. Nature 439, 441(2006).
*** H. Schwoerer, et al. Nature 439, 445(2006).
**** Y. Y. Ma et al., Phys Plasmas 16, 34502(2009).
BNL, Upton, Long Island, New York
Imperial College of Science and Technology, Department of Physics, London
UMD, College Park, Maryland
Stony Brook University, StonyBrook
Recent theoretical and experimental studies point to better efficiency of laser-driven ion acceleration when approaching the critical plasma density regime. Simultaneously, this is the condition for observing solitons: "bubble"-like quasi-stationary plasma formations with laser radiation trapped inside. Exploring this regime with ultra-intense solid state lasers is problematic due to the lack of plasma sources and imaging methods at ~1021/cc electron density. The terawatt picosecond CO2 laser operated at Brookhaven's Accelerator Test Facility offers a solution to this problem. At 10 μm laser wavelength, the CO2 laser shifts the critical plasma density to 1019/cc which is attainable with gas jets and can be optically probed with visible light. Capitalizing on this approach, we focused a circular-polarized CO2 laser beam with a0=0.5 onto a hydrogen gas jet and observed monoenergetic proton beams in the 1 MeV range. Simultaneously, the laser/plasma interaction region has been optically probed with a 2nd harmonic picosecond Nd:YAG laser to reveal stationary soliton-like plasma formations. 2D PIC simulations agree with experimental results and aid in their interpretation.
PPPL, Princeton, New Jersey
This paper presents results of advanced numerical simulations demonstrating the feasibility of tight collective focusing of intense ion beams for the Neutralizing Drift Compression Experiment (NDCX-I). In the collective focusing scheme, a weak magnetic lens provides strong focusing of an intense ion beam carrying an equal amount of neutralizing electron background [S. Roberston, Phys. Rev. Lett. 48, 149 (1982)]. For instance, a solenoidal magnetic field of several hundred gauss can focus an intense neutralized ion beam within a short distance of several centimeters. The enhanced focusing is provided by a strong self-electric field, which is produced by the collective electron dynamics. The numerical simulations are performed with the LSP particle-in-cell (PIC) code, and the results of the simulations are found to be in good agreement with analytical predictions. Collective focusing limitations due to possible heating of the co-moving electrons during the transverse compression are also discussed.
HU/AdSM, Higashi-Hiroshima
LLNL, Livermore, California
Resonant instabilities of ion plasmas confined in a linear Paul trap are studied using the particle-in-cell code WARP. Transverse two-dimensional model is employed to save computing time and perform systematic investigations. Both applied and self-field forces are calculated with a boundary condition assuming a quadrupole electrode structure. A large number of simulations were carried out with rms matched plasmas to clarify characteristics of the instability caused by linear and nonlinear coherent resonances. Stop band distributions produced by the simulation runs are consistent with theoretical prediction. These results are also compared to experimental results obtained from Hiroshima University Paul trap that is developed to study beam dynamics. It is shown that the stop band distributions of both numerical and experimental results are good agreement each other. We confirmed from these results that coherent resonances are excited when one of the coherent tunes is close to a half integer.
MIT/PSFC, Cambridge, Massachusetts
The dynamics of charged particles in a recently-discovered adiabatic thermal beam equilibrium* are studied. In particular, test particle motion is analyzed numerically, assuming the beam equilibrium fields are in a periodic solenoidal focusing channel. Poincare surface-of-section maps are generated to examine the behavior of the test particles in phase space such as nonlinear resonances and chaotic regions. Comparisons are made between the adiabatic thermal and rigid-rotor Vlasov beam equilibria**.
* J. Zhou, K.R. Samokhvalova, and C. Chen, Phys. Plasmas 15, 023102 (2008)
** C. Chen, R. Pakter and R.C. Davidson, Phys. Rev. Lett. 79, 225 (1997)