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The injection of laser-generated protons through conventional drift tube linear accelerators (linacs) has been studied numerically. For this, we used the parameters of the proton source produced by ultraintense lasers, i.e., with an intrinsic high beam quality. The numerical particle tracing code PARMELA [L. M. Young and J. H. Billen, LANL Report No. LA-UR-96-1835, 2004] is then used to inject experimentally measured laser-generated protons with energies of 7±0.1 MeV and rms un-normalized emittance of 0.180 mm mrad into one drift tube linac tank that accelerated them to more than 14 MeV. The simulations exhibit un-normalized emittance growths of 8 in x direction and 22.6 in y direction, with final emittances lower than those produced using conventional sources, allowing a potential luminosity gain for the final beam. However, the simulations also exhibit a limitation in the allowed injected proton charge as, over 0.112 mA, space charge effect worsens significantly the beam emittance. [ABSTRACT FROM AUTHOR]

We have determined limits on the cross section for both electronically nonadiabatic excitation and quenching in the Cl(2Pj)+D2 system. Our experiment incorporates crossed-molecular-beam scattering with state-selective Cl(2P1/2,3/2) detection and velocity-mapped ion imaging. By colliding atomic chlorine with D2, we address the propensity for collisions that result in a change of the spin-orbit level of atomic chlorine either through electronically nonadiabatic spin-orbit excitation Cl(2P3/2)+D2→Cl*(2P1/2)+D2 or through electronically nonadiabatic spin-orbit quenching Cl*(2P1/2)+D2→Cl(2P3/2)+D2. In the first part of this report, we estimate an upper limit for the electronically nonadiabatic spin-orbit excitation cross section at a collision energy of 5.3 kcal/mol, which lies above the energy of the reaction barrier (4.9 kcal/mol). Our analysis and simulation of the experimental data determine an upper limit for the excitation cross section as σNA≤0.012 Å2. In the second part of this paper we investigate the propensity for electronically nonadiabatic spin-orbit quenching of Cl* following a collision with D2 or He. We perform these experiments at collision energies above and below the energy of the reaction barrier. By comparing the amount of scattered Cl* in our images to the amount of Cl* lost from the atomic beam we obtain the maximum cross section for electronically nonadiabatic quenching as σNA≤15-15+44 Å2 for a collision energy of 7.6 kcal/mol. Our experiments show the probability for electronically nonadiabatic quenching in Cl*+D2 to be indistinguishable to that for the kinematically identical system of Cl*+He. [ABSTRACT FROM AUTHOR]

Presents information on a study which derived the heating profile arising from a noiseless beam, using heat propagation equation. Main features of the heating profile for noiseless beams; Analytical derivation of noise-induced heating; Conclusion.

Abstract The long-term macroparticle tracking simulation is computationally challenging but needed in order to study space-charge effects in high intensity circular accelerators. To address the challenge, in this paper, we proposed using a fully symplectic particle-in-cell model for the long-term space-charge simulation. We analyzed the artificial numerical emittance growth in the simulation and suggested using threshold numerical filtering in frequency domain to mitigate the emittance growth in the simulation. We also explored alternative frozen space-charge simulations and observed qualitative agreement with the self-consistent simulations. [ABSTRACT FROM AUTHOR]

Abstract The transverse beam emittance is a crucial parameter determining the brightness of an electron storage ring based synchrotron radiation source. The beam emittance is typically determined using the transverse electron beam size and the beta function at a particular location. For a low energy storage ring, the direct imaging method using visible/UV light has many advantages, including being simple, straightforward, and cost-effective. The resolution of such a system can be quite adequate for measuring electron beams with a reasonably large transverse beam size. In this work, we present the development of a new transverse beam profile measurement system for the Duke storage ring. This new system has been characterized to allow absolute measurements of the electron beam size while achieving better system resolution than previously thought possible for the direct imaging technique. The preliminary measurement results show that this system is capable of measuring the horizontal beam size over a wide range of the electron beam energies and currents. The system has also been demonstrated as a useful tool to study the intra-beam scattering related emittance increase in the storage ring. [ABSTRACT FROM AUTHOR]

Abstract Active plasma lenses are promising technologies for the focusing of high brightness electron beams due to their radially symmetric focusing and their high field gradients (up to several kT/m). However, in a number of experimental situations, the transverse non-uniformity of the current density flowing in the lens causes beam emittance growth and increases the minimum achievable spot size. To study the physics of the capillary discharge processes employed as active plasma lenses, we developed a 2-D hydrodynamic computational model. Here, we present preliminary simulation results and we compare the computed magnetic field profile with one from literature, which has been experimentally inferred. The result of the comparison is discussed. [ABSTRACT FROM AUTHOR]

Abstract In laser-driven wakefield, ionization induced injection is an efficient way to inject electrons in the plasma wave. A detailed study on the beam dynamics under the influence of beam loading effects, which can be controlled by the concentration of nitrogen impurity introduced in the hydrogen gas was conducted. For a specific value of this percentage, the final energy of the high-energy electron bunch becomes nearly independent of the trapped positions, thus leading to a small energy dispersion. We also show that the final beam emittance is mainly determined by the injection process. [ABSTRACT FROM AUTHOR]

The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) Linac consists of two independent beam lines that facilitate simultaneous injection of H + and H − beams into the linear accelerator. The efficiency of beam transport within this structure is largely controlled by the effects of space-charge neutralization. In this paper, we report a series of experiments that were performed to determine the level, as well as the required timescale for the onset of beam space charge neutralization. Measurements performed along the structure indicate significant variation of neutralized space charge beam dynamics in the beamline, and the corresponding results have been used to substantially improve beam transport with diminished beam losses. The analysis of experimental and theoretical data employed in optimization of beam performance in the transport line is discussed. [ABSTRACT FROM AUTHOR]

The surface plasmon polaritons make the emittance of the electron beam emitted from the photocathode complicated. In this article, numerical investigations are carried out to study the influence of the plasmonic near field (PNF) excited by a square hole array on the beam emittance. The characteristics of the emittance induced by PNF are studied. The coupling between the emittance caused by PNF and the original intrinsic emittance due to the excess energy of electrons and the surface roughness of the cathode is discussed. The results provide insights into the suppression of the emittance caused by PNF and new possibilities to break the limits of the nature of the materials, improving the performance of a photocathode. [ABSTRACT FROM AUTHOR]

Abstract: Since orbital angular momentum (OAM) being investigated intensively in the optical region, there have been growing interests in employing OAM to solve the problem in wireless communications as a new method. It is found that the independence between different OAM modes is crucial to wireless communications. Motivated by the tremendous potential of OAM in communication systems, a novel method to generate vortex beams by spoof surface plasmon polariton (SPP) is proposed. A looped double‐layer spoof SPP waveguide is applied to realize the transmission of electromagnetic waves. Beam emitting is accomplished through a series of circular patches, whose role is not only the radiation units but also resonators giving rise to the phase shifts required by the vortex beam. The proposed method is validated by both numerical simulation and experiment. The measured results show that spoof SPP are radiated by the circular patches and vortex beams carrying different OAM modes are observed at different frequencies. The proposed method possesses smaller size and is much easier to be integrated into systems and integrated circuits. The simple structure and design procedure make the proposed method promising in future wireless communication systems. [ABSTRACT FROM AUTHOR]

The dual-axis radiographic hydrodynamic test (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. On the DARHT-II LIA, we measure an emittance higher than predicted by theoretical simulations, and even though this accelerator produces submillimeter source spots, we are exploring ways to improve the emittance. Some of the possible causes for the discrepancy have been investigated using particle-in-cell codes. The simulations establish that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo. [ABSTRACT FROM PUBLISHER]

An excellent interfacing between injector linac and synchrotron is mandatory to provide ion beams of unprecedented intensities and qualities. One consequence of the single-plane Multi-Turn Injection (MTI) is that the required injection emittance for the injection plane (usually the horizontal one) is very demanding; to the other plane not. Re-partitioning of the injected beam emittances, i.e. round-to-flat transformation would increase the injection efficiency. This benefit effect to the MTI performance of a smaller emittance has been measured as a function of the amount of flatness of the beam. An excellent agreement between simulation and measured injection performance as a function of the injected emittance was achieved thanks to fast adjustment of the beam flatness without changing other beam parameters. [ABSTRACT FROM AUTHOR]

Advanced diagnostic tools for high brightness electron beams are mandatory for the proper optimization of plasma-based accelerators. The accurate measurement of beam parameters at the exit of the plasma channel plays a crucial role in the fine tuning of the plasma accelerator. Electron beam diagnostics will be reviewed with emphasis on emittance measurement, which is particularly complex due to large energy spread and strong focusing of the emerging beams. [ABSTRACT FROM AUTHOR]

The heating of the electronic distribution of a copper photocathode due to an intense drive laser pulse is calculated under the two-temperature model using fluences and pulse lengths typical in RF photoinjector operation. Using the finite temperature-extended relations for the photocathode intrinsic emittance and quantum efficiency, the time-dependent emittance growth due to the same photoemission laser pulse is calculated. This laser heating is seen to limit the intrinsic emittance achievable for photoinjectors using short laser pulses and low quantum efficiency metal photocathodes. A pump-probe photocathode experiment in a standard 1.6 cell S-band gun is proposed, in which simulations show the time dependent thermal emittance modulation within the bunch from laser heating can persist for meters downstream and, in principle, be measured using a slice emittance diagnostic. [ABSTRACT FROM AUTHOR]

Magnetic field errors and misalignments of magnetic and diagnostic components induce spurious emittance growth. The aim of this study is to correct the impact of such errors on the ELI-NP Gamma Beam System low energy line for an effective commissioning of the machine. To perform this study we use the simulation code elegant , for alignment and trajectory stabilization methods such as one-to-one steering, fast-trajectory-feedback (FTF) or global method and Dispersion Free Steering (DFS). We show the latter to be the most robust trajectory control method for magnetic elements and monitor errors. [ABSTRACT FROM AUTHOR]

In this paper we discuss the application of the flat beam transform to generate beams suitable for injection into slab-symmetric dielectric laser-driven accelerators (DLAs). A study of the focusing requirements to keep the particles within the tight apertures characterizing these accelerators shows the benefits of employing ultralow beam emittances. The slab geometry of the many dielectric accelerating structures strongly favors the use of flat beams with large ratio between vertical and horizontal emittances. We employ particle tracking simulations to study the application of the flat beam transform for two injector designs, a DC non relativistic photogun and a 1.6 cell S-band RF photoinjector, obtaining in both cases emittance ratios between the horizontal and vertical plane in excess of 100 in agreement with simple analytical estimates. The 4 MeV RF photoinjector study-case can be directly applied to the UCLA Pegasus beamline and shows normalized emittances down to < 3 nm in the vertical dimension for beam charges up to 20 fC, enabling a two-stage DLA experiment. [ABSTRACT FROM AUTHOR]

Fast ion instability has been identified as one of the most prominent instabilities in the recently constructed NSLS-II storage ring at Brookhaven National Laboratory. At a relatively low beam current (~ 25 mA) multi-bunch fills, ion-induced instabilities have already been observed during the early stages of machine commissioning. At present user operation with 250 mA in ~1000 bunches, the fast ion still remains the dominant instability, even after months of vacuum conditioning at high current. Ion-induced dipole motions of the electron beam have been suppressed using the transverse bunch-by-bunch (BxB) feedback system. However other adverse effects of this instability, such as the vertical beam size increase along the bunch train cannot be cured by the feedback system. Therefore, to achieve the NSLS-II design current of 500 mA while maintaining a small vertical beam emittance, it is important to further understand the fast ion instability and develop mitigation techniques. This paper reports on a series of ion-instability observations at various fill patterns and beam currents using start-of-art NSLS-II diagnostic tools. [ABSTRACT FROM AUTHOR]

A novel bidirectional compression electron gun is designed for a W-band sheet beam traveling-wave tube. A parabolic curved cathode and a beam focusing electrode based on spline interpolation curves are proposed to obtain a beam with good quality. Two directional compressions are introduced to reduce the beam loading of cathode. A 30-kV, 0.97-A beam is emitted by a curved 0.112-cm2 cathode with a beam loading of 8.66 A/cm2. The beam at waist position is 1.4 mm $\times0.4$ mm with a compression ratio of 2 and 10 in two directions separately. Studies of beam emittance and sensitivity of beam dynamics to mechanical errors are also carried out to understand the influence of structure parameters on electron gun performance. [ABSTRACT FROM AUTHOR]

We present the design analysis of a point focused electron beam emitter using numerical techniques. Simulation and modeling were performed followed by the calculation of emission parameters using programming codes EGUN and CST-PS. Beam emittance, average current density and perveance were calculated and are in agreement with the experimental values obtained at 10 kV acceleration potential. The emission parameters were evaluated up to 110 kV. This confirms possibilities of potential application of emitter for a linear accelerator. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) Monte Carlo simulation was used to study the variation of backscattered electron (BSE) signal across pore-solid boundaries in cement-based materials in order to enhance quantitative analysis of pore structure. The effects of pore size, depth and boundary inclination angle were investigated. It is found that pores down to 1 nm can generate sufficient contrast to be detected. Visibility improves with larger pore size, smaller beam probe size and lower acceleration voltage. However, pixels in shallow pores or near pore boundaries display higher grey values (brightness) than expected due to sampling sub-surface or neighbouring solid material. Thus, cement-based materials may appear less porous or the pores appear smaller than they actually are in BSE images. Simulated BSE images were used to test the accuracy of the Overflow pore segmentation method. Results show the method is generally valid and gives low errors for pores that are 1 μm and greater. [ABSTRACT FROM AUTHOR]

The Resonance Ionization Laser Ion Source (RILIS) has emerged as an important technique in many Radioactive Ion Beam (RIB) facilities for its reliability, and ability to ionize target elements efficiently and element selectively. GISELE is an off-line RILIS test bench to study the implementation of an on-line laser ion source at the GANIL separator facility. The aim of this project is to determine the best technical solution which combines high selectivity and ionization efficiency with small ion beam emittance and stable long term operation. The ion source geometry was tested in several configurations in order to find a solution with optimal ionization efficiency and beam emittance. Furthermore, a low work function material was tested to reduce the contaminants and molecular sidebands generated inside the ion source. First results with ZrC ionizer tubes will be presented. Furthermore, a method to measure the energy distribution of the ion beam as a function of the time of flight will be discussed. [ABSTRACT FROM AUTHOR]

Setting up collisions in high energy circular colliders requires beam acceleration and “beta-squeeze”. The latter produces small beam sizes, and hence, high luminosity by applying strong focusing with quadrupoles near the interaction points. At the Relativistic Heavy Ion Collider (RHIC), these two processes, beam acceleration and beta-squeeze, have been performed simultaneously during recent years. In the past, beam optics correction at RHIC has only taken place at injection and at final energy, with interpolation of corrections partially into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats that, if corrected, could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoiding the high-order multipole fields sampled by particles within the bunch. We recently demonstrated beam optics corrections during acceleration at RHIC. As a valuable by-product, these corrections minimized the beta-beat at the profile monitors, so providing more accurate measurements of the evolution of the beam emittances during acceleration. [ABSTRACT FROM AUTHOR]

This paper presents a detailed description of the ion cooler and buncher, installed at the Low Energy Beam and Ion Trap Facility (LEBIT) at the National Superconducting Cyclotron Laboratory (NSCL). NSCL uses gas stopping to provide rare isotopes from projectile fragmentation for its low-energy physics program and to the re-accelerator ReA. The LEBIT ion buncher converts the continuous rare-isotope beam, delivered from the gas stopping cell, into short, low-emittance ion pulses, required for high-precision mass measurements with a 9.4 T Penning trap mass spectrometer. Operation at cryogenic temperatures, a simplified electrode structure and dedicated rugged electronics contribute to the high performance and reliability of the device, which have been essential to the successful LEBIT physics program since 2005. [ABSTRACT FROM AUTHOR]

The noninterceptive four-dimensional transverse emittance measurements are essential for commissioning the high power continue-wave (CW) proton linacs as well as their operations. The conventional emittance measuring devices such as slits and wire scanners are not well suited under these conditions due to sure beam damages. Therefore, the method of using noninterceptive Beam Position Monitor (BPM) is developed and demonstrated on Injector Scheme II at the Chinese Accelerator Driven Sub-critical System (China-ADS) proofing facility inside Institute of Modern Physics (IMP) [1] . The results of measurements are in good agreements with wire scanners and slits at low duty-factor pulsed (LDFP) beam. In this paper, the detailed experiment designs, data analysis and result benchmarking are presented. [ABSTRACT FROM AUTHOR]

Particle-induced X-ray emission is used for determining the elemental composition of materials. This method uses low-energy protons (of several MeV), which can be obtained from high-energy (of tens MeV) accelerators. Instead of manufacturing an accelerator for generating the MeV protons, the use of a PET cyclotron has been suggested for designing the beamline for multipurpose applications, especially for the PIXE experiment, which has a dedicated high-energy (of tens MeV) accelerator. The beam properties of the cyclotron were determined at this experimental facility by using an external beamline before transferring the ion beam to the experimental chamber. We measured the beam profile and calculated the emittance using the pepper-pot method. The beam profile was measured as the beam current using a wire scanner, and the emittance was measured as the beam distribution at the beam dump using a radiochromic film. We analyzed the measurement results and are planning to use the results obtained in the simulations of external beamline and aligned beamline components. We will consider energy degradation after computing the beamline simulation. The experimental study focused on measuring the emittance from the cyclotron, and the results of this study are presented in this paper. [ABSTRACT FROM AUTHOR]

Periodic magnetic structures (wigglers) have been successfully used for a long time for controlling beam parameters in charged-particle storage rings for various purposes (including the reduction of emittance). In this work, we optimize the optical functions of the storage ring gap into which a wiggler is installed for a more effective reduction of the emittance. Optimal solutions are obtained for the first time for FODOtype and theoretical minimum emittance (TME) structures. An original method is proposed for suppressing the contribution of the wiggler fields to the radiation excitation of the phase volume of the beam by modulating the field period along the wiggler axis. [ABSTRACT FROM AUTHOR]

Indus-2 storage ring is a 2.5 GeV third generation synchrotron radiation source. This source was commissioned using a moderate optics. Beam injection was accomplished using an off momentum electron beam to avoid difficulties faced in storage of beam at 550 MeV. The injection procedure and relevant beam dynamical studies are discussed. The switch over from the moderate optics to low emittance optics is done at 2.5 GeV after storing the electron beam. The procedure evolved to reduce the beam emittance and its implementation during the operation is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we present conceptual design of the Iranian Light Source Facility (ILSF) injection systems. Beam dynamics issue and expected performance of the designed injectors have been described. We introduce layout of the injection systems, give the optimized parameters of the components and discuss the injection and extraction procedures with detail. [ABSTRACT FROM AUTHOR]

Alternative acceleration technologies are currently under development for cost-effective, robust, compact, and efficient solutions. One such technology is plasma wakefield acceleration, driven by either a charged particle or laser beam. However, the potential issues must be studied in detail. In this paper, the emittance evolution of a witness beam through elastic scattering from gaseous media and under transverse focusing wakefields is studied. [ABSTRACT FROM AUTHOR]

A 400 keV deuteron (D+) radio frequency quadrupole (RFQ) accelerator has been designed, built, and commissioned at the Bhabha Atomic Research Centre, India. A beam line has been developed for injecting deuterons into the 400 keV RFQ. This comprises of a RF plasma ion source and a low energy beam transport (LEBT) system, consisting of two solenoid magnets and two steerer magnets. The ion source is characterized in terms of transverse beam emittance. A slit-wire scanner based emittance measurement setup has been developed for the transverse emittance measurements of H+ and D+ beams. The measured emittance values are found to be well within the acceptance value for the RFQ. These measured emittance parameters are used to optimize the solenoid ields in LEBT to match the beam from the ion source to RFQ. TRACEWIN simulation code is used for the beam transport simulations. The simulations show 99% transmission of D+ beam through the RFQ, while 95% transmission has been measured experimentally. [ABSTRACT FROM AUTHOR]

We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9-9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers [ABSTRACT FROM AUTHOR]

To exactly answer which density region that some frequently used symmetry-energy-sensitive observables probe, for the first time, we make a study of the decomposition of the sensitivity of some symmetryenergy- sensitive observables. It is found that for the Au+Au reaction at incident beam energies of 200 and 400 MeV/nucleon, frequently used symmetry-energy-sensitive observables mainly probe the density-dependent symmetry energy around 1.25p0 (for pionic observables) or 1.5p0 (for nucleonic observables). Effects of the symmetry energy in the low-density region is in general small but observable. The fact that the symmetry-energysensitive observables are not sensitive to the symmetry energy in the maximal baryon-density region increases the difficulty of studying nuclear symmetry energy at superdensity. [ABSTRACT FROM AUTHOR]

High quality electron beams with flat distributions in both energy and current are critical for many accelerator-based scientific facihties such as free-electron lasers and MeV ultrafast electron diffraction and microscopes. In this Letter, we report on using corrugated structures to compensate for the beam nonlinear energy chirp imprinted by the curvature of the radio-frequency field, leading to a significant reduction in beam energy spread. By using a pair of corrugated structures with orthogonal orientations, we show that the quadrupole wakefields, which, otherwise, increase beam emittance, can be effectively canceled. This work also extends the applications of corrugated structures to the low beam charge (a few pC) and low beam energy (a few MeV) regime and may have a strong impact in many accelerator-based facilities. [ABSTRACT FROM AUTHOR]

In a double bend achromat, Chasman-Green (CG) lattice represents the basic structure for low emittance synchrotron radiation sources. In the basic structure of CG lattice single focussing quadrupole (QF) magnet is used to form an achromat. In this paper, this CG lattice is discussed and an analytical relation is presented, showing the limitation of basic CG lattice to provide the theoretical minimum beam emittance in achromatic condition. To satisfy theoretical minimum beam emittance parameters, achromat having two, three, and four quadrupole structures is presented. In this structure, different arrangements of QF and defocusing quadruple (QD) are used. An analytical approach assuming quadrupoles as thin lenses has been followed for studying these structures. A study of Indus-2 lattice in which QF-QD-QF configuration in the achromat part has been adopted is also presented. [ABSTRACT FROM AUTHOR]