The Paul Trap Simulator Experiment (PTSX) is a linear Paul trap whose purpose is to simulate the nonlinear transverse dynamics of intense charged particle beam propagation in periodic-focusing quadrupole magnetic transport systems. Externally created cesium ions are injected and trapped in the long central electrodes of the PTSX device. In order to have well-matched one-component plasma equilibria for various beam physics experiments, it is important to optimize the ion injection. From the experimental studies reported in this paper, it is found that the injection process can be optimized by minimizing the beam mismatch between the source and the focusing lattice, and by minimizing the number of particles present in the vicinity of the injection electrodes when the injection electrodes are switched from the fully oscillating voltage waveform to their static trapping voltage.

Recent laser wakefield acceleration experiments have demonstrated the generation of femtosecond, nano-Coulomb, low emittance, nearly monokinetic relativistic electron bunches of sufficient quality to produce bright, tunable, ultrafast x-rays via Compton scattering. Design parameters for a proof-of-concept experiment are presented using a three-dimensional Compton scattering code and a laser-plasma interaction particle-in-cell code modeling the wakefield acceleration process; x-ray fluxes exceeding ${10}^{21}{\mathrm{s}}^{-1}$ are predicted, with a peak brightness $>{10}^{19}\mathrm{\text{photons}}/({\mathrm{mm}}^2{\mathrm{mrad}}^2\mathrm{s}0.1\%\mathrm{\text{bandwidth}})$).

Bent crystal situated in a circulating beam can serve for efficient slow extraction or active collimation of the beams. This technique, well established at 1–1000 GeV, could be efficient also at the energies as low as 0.1–1 GeV according to the computer simulations presented in this paper. Applications might include halo scraping in the spallation neutron sources or slow extraction from medical synchrotrons.

Efficient transfer of electron beams from one accelerator to another is important for 3rd-generation light sources that operate using top-up. In top-up mode, a constant amount of charge is injected at regular intervals into the storage ring to replenish beam lost primarily due to Touschek scattering. Top-up therefore requires that the complex of injector accelerators that fill the storage ring transport beam with a minimum amount of loss. Injection can be a source of significant beam loss if not carefully controlled. In this note we describe a method of processing injection transient signals produced by beam-position monitors and using the processed data in feedback. Feedback control using the technique described here has been incorporated in the Advanced Photon Source (APS) booster synchrotron to correct injection transients.

Wakefields defining beam stability affect also the beam optics and beam properties in high current machines. In this paper we present observations and analysis of the optical effects in the PEP-II Stanford Linear Accelerator Center B Factory, which has the record in achievement of high electron and positron currents. We study the synchronous phase and the bunch length variation along the train of bunches, overall bunch lengthening, and effects of the wakes on the tune and on the Twiss parameters. This analysis is being used in upgrades of PEP-II and may be applied to future B factories and damping rings for linear colliders.

We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches with hard and soft edges. This theory is relevant for diagnostics of ellipsoidal electron bunches. Realization of such bunches would solve the problem of space-charge induced emittance degradation.

In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR) deflector which is composed of a DR radiator and three beam position monitors (BPMs). When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency $\Delta {\nu }_{\mathrm{spin}}$ of the beam (particularly due to its energy spread) is sufficiently large that the spin precession phases of individual particles smear out completely during the time $\tau$ between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference-overlap effect and a spin echo effect. This paper is to address these two effects. The interference-overlap effect occurs when $\Delta {\nu }_{\mathrm{spin}}$ is too small, or when $\tau$ is too short, to complete the smearing process. In this case, the two resonance crossings overlap each other, and the final polarization exhibits constructive or destructive interference patterns depending on the exact value of $\tau$. Typically, the beam’s energy spread is large and this interference-overlap effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time $\tau$ after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when $\tau$ is very large, and could be a sensitive (albeit challenging) way to experimentally test the intricate spin dynamics in a synchrotron. After giving an analysis of the interference-overlap and the echo effects, two possible experiments to explore them are suggested.

In this paper we present a complete linear synchrobetatron coupling formalism by studying the transfer matrix which describes linear horizontal and longitudinal motions. With the technique established in the linear horizontal-vertical coupling study [D. Sagan and D. Rubin, Phys. Rev. ST Accel. Beams 2, 074001 (1999)], we found a transformation to block diagonalize the transfer matrix and decouple the betatron motion and the synchrotron motion. By separating the usual dispersion term from the horizontal coordinate first, we were able to obtain analytic expressions of the transformation under reasonable approximations. We also obtained the perturbations to the betatron tune and the Courant-Snyder functions. The closed-orbit changes due to finite energy gains at rf cavities and radiation energy losses were studied by the $5\times 5$ extended transfer matrix with the fifth column describing kicks in the 4-dimension phase space.

The design and operation support of hadron (proton and heavy-ion) linear accelerators require substantial use of beam dynamics simulation tools. The beam dynamics code TRACK has been originally developed at Argonne National Laboratory (ANL) to fulfill the special requirements of the rare isotope accelerator (RIA) accelerator systems. From the beginning, the code has been developed to make it useful in the three stages of a linear accelerator project, namely, the design, commissioning, and operation of the machine. To realize this concept, the code has unique features such as end-to-end simulations from the ion source to the final beam destination and automatic procedures for tuning of a multiple charge state heavy-ion beam. The TRACK code has become a general beam dynamics code for hadron linacs and has found wide applications worldwide. Until recently, the code has remained serial except for a simple parallelization used for the simulation of multiple seeds to study the machine errors. To speed up computation, the TRACK Poisson solver has been parallelized. This paper discusses different parallel models for solving the Poisson equation with the primary goal to extend the scalability of the code onto 1024 and more processors of the new generation of supercomputers known as BlueGene (BG/L). Domain decomposition techniques have been adapted and incorporated into the parallel version of the TRACK code. To demonstrate the new capabilities of the parallelized TRACK code, the dynamics of a 45 mA proton beam represented by ${10}^8$ particles has been simulated through the 325 MHz radio frequency quadrupole and initial accelerator section of the proposed FNAL proton driver. The results show the benefits and advantages of large-scale parallel computing in beam dynamics simulations.

A synchrotron radiation (SR) interferometer with Herschelian reflective optics has been developed for the measurement of beams of several $\mu \mathrm{m}$ in size. In a conventional refractive SR interferometer, the dispersion effect of the objective lens limits the instrument to a smaller range of beam-size measurements. To avoid this problem, we designed a Herschelian arrangement of reflective optics for the interferometer. The effectiveness of the reflective SR interferometer was confirmed at the KEK Accelerator Test Facility (ATF) damping ring. The measured vertical beam size obtained using the reflective SR interferometer was $4.7\mu \mathrm{m}$ and the estimated vertical emittance was $0.97\times {10}^{-11}\mathrm{m}$.

A comprehensive analysis is presented that describes amplification of a seed THz pulse in a single-pass free-electron laser (FEL) driven by a photoinjector. The dynamics of the radiation pulse and the modulated electron beam are modeled using the time-dependent FEL code, GENESIS 1.3. A 10-ps (FWHM) electron beam with a peak current of 50–100 A allows amplification of a $\sim 1\mathrm{kW}$ seed pulse in the frequency range 0.5–3 THz up to 10–100 MW power in a relatively compact 2-m long planar undulator. The electron beam driving the FEL is strongly modulated, with some inhomogeneity due to the slippage effect. It is shown that THz microbunching of the electron beam is homogeneous over the entire electron pulse when saturated FEL amplification is utilized at the very entrance of an undulator. This requires seeding of a 30-cm long undulator buncher with a 1–3 MW of pump power with radiation at the resonant frequency. A narrow-band seed pulse in the THz range needed for these experiments can be generated by frequency mixing of ${\mathrm{CO}}_2$ laser lines in a GaAs nonlinear crystal. Two schemes for producing MW power pulses in seeded FELs are considered in some detail for the beam parameters achievable at the Neptune Laboratory at UCLA: the first uses a waveguide to transport radiation in the 0.5–3 THz range through a 2-m long FEL amplifier and the second employs high-gain third harmonic generation using the FEL process at 3–9 THz.

The Spallation Neutron Source ring employs doublet quadrupoles and dipole correctors in its straight sections. The electromagnetic quadrupoles have a large aperture, small aspect ratio, and relatively short iron-to-iron distance. The corrector is even closer to one of the quads. There have been concerns on the magnetic fringe field and interference in the doublet magnets and their assemblies. We have performed 3D computing simulations to study magnetic field distributions in the doublet magnets. Further, we have analyzed the particle optics based on the $z$-dependent focusing functions of the quads. The effect of the magnetic fringe field and interference, including the third-order aberrations, on the particle motion are investigated. The lens parameters and the first-order hard edge models are derived and compared with the parameters used in the ring lattice calculations.

The Cornell Electron Storage Ring (CESR) operates with 2 GeV multibunch electron and positron beams in a single beam pipe. Electrostatic separators are used to separate the two counterrotating beams at the parasitic crossings. When the beam energy was lowered from 5 GeV in 2003, the strength of the beam-beam interaction became a more important factor in beam-current limitations, resulting in extensive experimental and modeling studies of their characteristics. The CESR lattice design procedure has been modified recently to account explicitly for their dynamic consequences. We describe our modeling of the beam-beam interaction, experimental validation techniques, and investigations into compensation strategies.

The drift motion of cooling electrons makes them able to respond to transverse perturbations of a cooled ion beam. This response may lead to dipole or quadrupole transverse instabilities at specific longitudinal wave numbers. While the dipole instabilities can be suppressed by a combination of the Landau damping, machine impedance, and the active damper, the quadrupole and higher order modes can lead to either emittance growth, or a lifetime degradation, or both. The growth rates of these instabilities are strongly determined by the machine $x-y$ coupling. Thus, tuning out of the coupling resonance and/or reduction of the machine coupling can be an efficient remedy for these instabilities.

Simultaneous tune and coupling feedback were successfully implemented during RHIC run 6. In this paper we describe the measurement and control hardware and software used to accomplish this, present some of the results, discuss areas that require further investigation, and finally offer a few comments on possible implications of these results for LHC commissioning.

We present a new technique to continuously measure and compensate the global difference coupling coefficient through the continuous measurements of eigenmode projection parameters, using a high resolution phase-locked-loop tune meter. First, four eigenmode projection parameters are defined as the observables for weak difference coupling. Then, their analytical expressions are obtained using the strict matrix treatment and the Hamiltonian perturbation theory of linear coupling. From these parameters, the complex global coupling coefficient can be fully determined and compensated. This method was successfully demonstrated in the Relativistic Heavy Ion Collider (RHIC) 2006 run.

A method for producing short electron bunches in an electron storage ring using pulsed phase modulation has been demonstrated. A simple theoretical model was validated using the particle tracking code elegant, and the bunch compression process was observed experimentally in the Advanced Photon Source storage ring using a visible light streak camera. Compression to 54% of the initial bunch length was achieved.