Induction core alloys are evaluated that are appropriate for heavy-ion induction accelerators to drive heavy-ion inertial fusion (HIF) power plants. Parameters evaluated include the usable flux swing and the energy loss over a range of magnetization rates of $\sim {10}^5–{10}^7\mathrm{T}/\mathrm{s}$, corresponding to pulse durations of $\sim 20$ to $0.2\mu \mathrm{s}$, respectively. The usable flux swing, for minimum core losses, extends from near the reversed remanent field to about 80% of the saturation field. The usable flux swing is enhanced, with little increase in losses, by annealing the core after winding. Maintaining low energy loss at high magnetization rates requires insulation to block interlaminar eddy currents. To obtain annealed cores with a high ratio of remanent to saturation magnetic field, the insulation must withstand annealing temperatures and apply minimum mechanical stress to the core during cooldown. We find that commercially available insulating coatings for amorphous metals either break down near ${10}^6\mathrm{T}/\mathrm{s}$ (a factor of 10 below the requirement), or do not achieve the maximum remanent field and hence the usable flux swing after annealing. More satisfactory coatings are available for silicon steel and nanocrystalline alloys, which could have applications in HIF. Amorphous alloys are capable of meeting most HIF needs, especially with improved coatings.

On-line monitoring of beam quality for high brightness beams is possible only by using noninvasive instruments. For matching measurements, very few such instruments are available. One candidate is a quadrupole pickup. Therefore, a new type of quadrupole pickup has been developed for the 26 GeV Proton Synchrotron at CERN, and a measurement system consisting of two such pickups is now installed in this accelerator. Using the information from these pickups, it is possible to determine both injection matching and emittance in the horizontal and vertical planes, for each bunch separately. This paper presents the measurement method and some of the results from the first year of use, as well as comparisons with other measurement methods.

We discuss the underlying reasoning behind and the details of the numerical algorithm used in the GINGER free-electron laser simulation code to load the initial shot noise microbunching on the electron beam. In particular, we point out that there are some additional subtleties which must be followed for multidimensional codes which are not necessary for one-dimensional formulations. Moreover, requiring that the higher harmonics of the microbunching also be properly initialized with the correct statistics leads to additional complexities. We present some numerical results including the predicted incoherent, spontaneous emission as tests of the shot noise algorithm’s correctness.

Coherent enhancement of the Smith-Purcell radiation produced from the interaction of a 1.8 MeV electron beam with a grating has been observed. The emitted radiation has been measured at angles in the 40° to 120° range, which correspond to wavelengths from 0.65 to 4 mm, approximately. The radiated power was 320 mW at 90°. Its angular distribution agrees well with the description of the process in terms of induced surface currents and has been used to infer the longitudinal profile of the electron bunch. It is concluded that the bunch has an approximately triangular profile, with 85% of the bunch particles contained within 14 ps. The possibilities of the technique as a bunch-shape diagnostic tool are also discussed.

There are several advantages in using a crystal for stripping of the ${\mathrm{H}}^{-}$ ion to obtain efficient injection of protons into a circular accelerator. First, the stripping efficiency of a crystal is at least as large as for an amorphous foil of the same substance and thickness. Second, the emittance increase imposed by the multiple Coulomb scattering of the protons on subsequent turns is drastically lower by a factor of up to $\simeq 7$. Third, the restricted energy loss of the protons is lower by a factor of up to $\simeq 1.5$—this, combined with the fact that the thermal conductivity of a single crystal of diamond is much higher than that of the amorphous material, will reduce the effect of heating of the stripping material. In high-power schemes based on amorphous foils heating of the electron stripping material is a limiting factor. Fourth, the reduced total energy loss is accompanied by a smaller energy loss straggling implying a smaller longitudinal emittance. Last, the so-called random orientation of the crystal can provide the option of stripping the ${\mathrm{H}}^{-}$ ions as in an amorphous foil while preserving the advantage of a high thermal conductivity, simply by changing the orientation of the crystal. A simulation using realistic parameters is presented, which reflects the efficient conservation of emittance using a diamond crystal. The phenomenon should in fact be applicable in general for the stripping of ${\mathrm{H}}^{-}$, although the advantages depend on parameters such as the energy. A reasonable figure of merit is the ratio of the total transverse emittance increase of crystalline and amorphous foils in one turn and in the presented case this is as high as a factor 3.9.

Weak-strong tracking simulations for the Large Hadron Collider have shown that long-range beam-beam collisions give rise to a well-defined diffusive aperture beyond which particles are lost quickly. In order to derive analytical estimates of this stability boundary, we use leading order perturbation theory and the Chirikov resonance overlap criterion applied to a simplified model with a 2-dimensional transverse phase space. In addition, a Fokker-Plank–type diffusion coefficient is calculated through the nonlinear action kicks imparted by the long-range beam-beam force. The analytical results are compared with the tracking data.

A microbunching instability driven by coherent synchrotron radiation (CSR) in a bunch compressor chicane is studied using an iterative solution of the integral equation that governs this process. By including both one-stage and two-stage amplifications, we obtain analytical expressions for CSR microbunching that are valid in both low-gain and high-gain regimes. These formulas can be used to explore the dependence of CSR microbunching on compressed beam current, energy spread, and emittance, and to design stable bunch compressors required for an x-ray free-electron laser.

We have developed a compact high-resolution retarding field energy analyzer for measuring the energy spread of space-charge-dominated electron beams. This energy analyzer has a cylindrical electrode to overcome the defocusing effects due to space-charge forces, beam trajectories, aperture effect, etc. The device provides excellent spatial and temporal information on the beam energy spread. Single-particle simulation shows that this energy analyzer has very good resolution for low-energy electron beams of several kilovolts and with large divergence angles. The energy analyzer has been tested with 2.5 keV, 60 mA electron beams. The measured energy spread is also compared with the theoretical calculations taking into account two main energy spread sources, namely, the Boersch effect and the longitudinal-longitudinal relaxation.

We describe concepts for high power semiconductor rf switches, designed to handle signals at $X$-band with power level near 100 MW. We describe an abstract design methodology and derive a general scaling law for these switches. We also present a design and experimental work of a switch operating at the ${\mathrm{TE}}_{01}$ mode in overmoded circular waveguides. The switch is composed of an array of tee junction elements that have a p-i-n diode array window in the third arm.

Instead of slip stacking, an alternate method of doubling the linear intensity of the Fermilab Main Injector is discussed. This method makes use of rf barriers to transfer 12 booster batches from the Fermilab Booster to the Main Injector in 12 consecutive booster cycles, totaling 800 ms. After that, adiabatic capture of the beam into 53 MHz buckets can be accomplished in about 10 ms. Because the beam is debunched during the injection process and no rf voltage is required, the beam loading voltages in the rf cavities are small and can be eliminated by a combination of counterphasing and mechanical shorts.

The appearance of rings of charge observed near the edge of beams from high-perveance guns is described with a simple ray tracing technique inspired by the particle-core model. We illustrate the technique, which has no analog in light optics, with examples from experiments employing solenoid focusing of an electron beam. The rings of charge result from the combined effects of external focusing and space-charge forces acting on paraxial fringe particles with relatively large initial transverse velocities. The model is independent of the physical mechanisms responsible for the fringe particles. Furthermore, the focal length for edge imaging in a uniform focusing channel is derived using a linearized trajectory equation for the motion of fringe particles. Counterintuitively, the focal length decreases as the beam current increases.

We discuss the choice of bunch length and crossing angle near the beam-beam limit in a storage-ring collider. First, we derive expressions for the tune shifts of either bunched or continuous round beams which are induced by a single collision with arbitrary crossing angle and bunch length and for the associated luminosities. Then, considering two collision points with alternating planes of crossing, we demonstrate that, if the total beam-beam tune shift is held constant, the collider luminosity increases as a function of bunch length and crossing angle. This implies a corresponding increase in the bunch intensity. As an illustration, we present numerical examples for a Large Hadron Collider upgrade and for the Very Large Hadron Collider.

This paper investigates the identification and correction of antisymmetric field components in combined function magnets. A measurement procedure is developed to identify small field components on the order of ${10}^{-3\mathrm{}}$ in the plane of the reference path. Furthermore, a method is proposed to compensate them by surface correction coils on the poles of the magnet. As an example, the measurement and compensation of antisymmetric field components in a $90°$ bending magnet of the double sided microtron HDSM at the MAMI-C electron scattering facility is simulated with the help of the electromagnetic design code TOSCA.

In this paper, a perturbation theory is developed for calculating the 6D transfer matrix of a combined function magnet. Starting from the linear part of the Hamiltonian, the transfer matrix $M$ is decomposed into an infinite sum over matrices $M_n$, which represent an $n$-fold interaction of the beam with the quadrupole content of the magnet. Given the magnetic field in the vicinity of the reference path, each matrix $M_n$ can be calculated either analytically or by numerical integration. As an example, the transfer matrix is calculated of the $90°$ bending magnet of the double sided microtron HDSM at the MAMI-C electron scattering facility, which so far has been possible only by means of particle tracking.

Macroparticle simulation plays an important role in modern accelerator design and operation. Most linear rf accelerators have been designed based on macroparticle simulations using longitudinal position as the independent variable. In this paper, we have done a systematic comparison between using longitudinal position as the independent variable and using time as the independent variable in macroparticle simulations. We have found that, for an rms-matched beam, the maximum relative moment difference for second, fourth moments and beam maximum amplitudes between these two types of simulations is $0.25\%$ in a 10 m reference transport system with physical parameters similar to the Spallation Neutron Source linac design. The maximum $z$-to- $t$ transform error in the space-charge force calculation of the position dependent simulation is about $0.1\%$ in such a system. This might cause a several percent error in a complete simulation of a linac with a length of hundreds of meters. Furthermore, the error may be several times larger in simulations of mismatched beams. However, if such errors are acceptable to the linac designer, then one is justified in using position dependent macroparticle simulations in this type of linac design application.

Field quality in superconducting magnets strongly depends on the geometry of the coil. Fiberglass spacers (shims) placed between the coil and the collars have been used to optimize magnetic and mechanical performances of superconducting magnets in large accelerators. A change in the shim thickness affects both the geometry of the coil and its state of compression (prestress) under operational conditions. In this paper we develop a coupled magnetomechanical model of the main Large Hadron Collider dipole. This model allows us to evaluate the prestress dependence on the shim thickness and the map of deformations of the coil and the collars. Results of the model are compared to experimental measurements carried out in a dedicated experiment, where a magnet model has been reassembled 5 times with different shims. A good agreement is found between simulations and experimental data both on the mechanical behavior and on the field quality. We show that this approach allows us to improve this agreement with respect to models previously used in the literature. We finally evaluate the range of tunability that will be provided by shims during the production of the Large Hadron Collider main dipoles.

The coherent synchrotron radiation of a bunch in a bunch compressor may lead to the microwave instability producing longitudinal modulation of the bunch with wavelengths small compared to the bunch length. It can also be a source of an undesirable emittance growth in the compressor. We derive and analyze the equation that describes linear evolution of the microwave modulation taking into account incoherent energy spread and finite emittance of the beam. Numerical solution of this equation for the Linac Coherent Light Source bunch compressor gives the amplification factor for different wavelengths of the beam microbunching.

We present the results of a detailed study on the acceleration of intense ion beams by relativistic laser plasmas. The experiments were performed at the 100 TW laser at the Laboratoire pour L’Utilisation des Lasers Intenses. We investigated the dependence of the ion beams on the target conditions based on theoretical predictions by the target normal sheath acceleration mechanism. A strong dependence of the ion beam parameters on the conditions on the target rear surface was found. We succeeded in shaping the ion beam by the appropriate tailoring of the target geometry and we performed a characterization of the ion beam quality. The production of a heavy ion beam could be achieved by suppressing the amount of protons at the target surfaces. Finally, we demonstrated the use of short pulse laser driven ion beams for radiography of thick samples with high resolution.