122601857
Experimental studies of longitudinal dynamics of space-charge dominated electron beams
A comprehensive experimental program was carried out at the University of Maryland Beam Transport facility to study the longitudinal beam physics of space-charge dominated bunches. This investigation included the behavior of (a) bunches with parabolic line charge profile, (b) bunches with rectangular line charge profile, and (c) local perturbations (slow and fast waves) in rectangular bunches. The major experimental results are presented in this paper.
117533820
Longitudinal kinetic energy spread from focusing in charged particle beams
A charged particle beam can be given a longitudinal kinetic energy spread through focusing by magnetic solenoid lenses. Measurements of energy spread are reported and are compared with the results of computer simulations, which include several known sources of energy spread. These sources are discussed. The results of the measurements and the simulations agree, giving energy spreads which are two orders of magnitude larger than the initial thermal energy spread.<<ETX>>
27409140
Generation of space-charge waves due to localized perturbations in a space-charge dominated beam.
It has been found for the first time in experiments with an electron beam that space-charge waves can be generated not only in pairs. A single slow wave, a single fast wave, or combinations of the two waves with different amplitude and polarity relations have been produced experimentally in a space-charge dominated beam. Analytical solutions derived from one-dimensional fluid equations show the amplitude and polarity of each space-charge wave as a function of the initial perturbation parameters. The theory provides the correct interpretation of the experimental observations.
39487088
Restoration of rectangular pulse shape after edge erosion for a space-charge dominated electron bunch.
We present in this Letter a novel experimental method that demonstrates the time reversibility of the 1D cold-fluid equations for a space-charge dominated beam. A bunch of charged particles with an initially rectangular line-charge and velocity profile experiences edge erosion during transport through a focusing system due to the nonlinear, longitudinal space-charge forces at the edges. By imposing on the eroded beam pulse a linear velocity gradient at a proper location one can restore the rectangular line-charge profile downstream. [An experiment has been performed to demonstrate this principle.] This technique could be used to offset edge erosion and assure a rectangular pulse shape for efficient acceleration and uniform power flow in the interaction region for applications of intense, high-power beams.
17295428
Influences of the magnetic coupling process on the spectrum of a disk covered by the corona
Context. Recently, much attention has been paid to the magnetic coupling (MC) process, which is supported by the very high emissivity indexes observed in Seyfert 1 galaxy MCG-6-30-15 and GBHC XTE J1650-500. But the rotational energy transferred from a black hole is simply assumed to be radiated away from the surrounding accretion disk in the black-body spectrum, which is obviously not consistent with the observed hard power-law X-ray spectra. Aims. We introduce a corona into the MC model to make it more compatible with observations. Methods. We describe the model and the procedure of a simplified Monte Carlo simulation, compare the output spectra in the cases with and without the MC effects, and discuss the influences of the three parameters involved in the MC process on the output spectra. Results. It is shown that the MC process augments radiation fluxes in the UV or X-ray band. The emergent spectrum is affected by the BH spin and magnetic field strength at the BH horizon, while it is almost unaffected by the radial profile of the magnetic field at the disk. Conclusions. Introducing corona into the MC model will improve the fitting of the output spectra from AGNs and GBHCs.
55579613
Computer simulation of the Maryland Transport Experiment
The longitudinal dynamics of the high-perveance long-pulse electron beam in the Maryland Transport Experiment is examined for the special case of an initially parabolic bunch. Because the longitudinal dynamics can depend on details of time-dependent transverse beam parameters which are difficult to measure, sensitivity studies using r-z simulations have been used to demonstrate that the details of longitudinal beam evolution are insensitive to transverse mismatch, and the bunch length evolution can be accurately described by the one-dimensional envelope equation with the "geometry factor" appropriately chosen. Comparison of experimental data to r,z simulation and to the envelope solution is presented.<<ETX>>
54869476
OPTIMAL RF SYSTEMS FOR LIGHTLY LOADED SUPERCONDUCTING STRUCTURES
one meter cavity would therefore need to supply only 300 W to meet these demands. Recent developments in the field of RF accelerators have created a demand for power amplifiers that can support very high accelerating gradients, 15-25 MV/m, in superconducting structures with extremely low losses. Free electron lasers with modest beam current, I<10 uA, or those based on energy recovery linacs may have intrinsic power demands of less than 1 kW/m. We present a design concept for an amplifier and external tuner system that will efficiently meet this requirement. A likely amplifier for this application is the Inductive Output Tube (IOT) which offers high AC/RF efficiency, flexible power output and switching capability without the need for external modulation. The use of solid state amplifiers is also considered. The external tuner circuit makes use of low loss RF components, include waveguide, circulators and ferrite phase shifters to create a moderate quality standing wave between the amplifier and the superconducting cavity. The potential effective Qext exceeds 3×10 7 .
123071671
Electron beam injector for longitudinal beam physics experiments
Design parameters of the electron beam injector for longitudinal compression and resistive wall instability experiments are discussed. The performance characteristics of its components and the injector system are presented. >
12960221
Study of the Electron Beam Dynamics in the FERMI @ ELETTRA Linac
A study of the electron beam dynamics in the linac is conducted for the FERMI free electron laser (FEL) founded for construction at the Sincrotrone Trieste
38286220
Interaction Region Design for the Electron-Ion Collider eRHIC
To facilitate the study of collisions between 10 GeV polarized electrons and 100 GeV/u heavy ions or 250 GeV polarized protons at luminosities in the 1033cm-2sec-1range (e-p case), adding a 10 GeV electron storage ring to the existing RHIC complex has been proposed. The interaction region of this electron-ion collider eRHIC has to provide the required low-beta focussing, while simultaneously accomodating the synchrotron radiation fan generated by beam separation close to the interaction point, which is particularly challenging. The latest design status of the eRHIC interaction region will be presented.
53867504
On the soliton solutions of the two-dimensional Toda lattice
The two-dimensional Toda lattice (2DTL) is a well-known (2+1)-dimensional integrable system that admits a large class of line-soliton solutions. We classify these soliton solutions by exploiting the structure of the Casoratian expression for its tau function. In general, these solutions consist of unequal numbers of 'incoming' and 'outgoing' line solitons. We classify the incoming and outgoing line solitons based on asymptotic analysis of the tau function of the 2DTL as the discrete variable tends to infinity. We also identify various subclasses of solutions and characterize some of them in terms of the amplitudes and directions of the interacting solitons. As a special case, we obtain the reduction in the soliton solutions of the one-dimensional Toda lattice. Throughout, we point out the similarities with—and the differences from—the corresponding results for the Kadomtsev–Petviashvili equation.