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The distribution function of a moving charge experiencing multiple Coulomb scattering has been used to derive relationships for the scattered beam parameters through the parameters of a beam incident on a target. The notion of a beam consistent with a target has been introduced, and a formula has been derived that relates the emittances of the incident and scattered beams.
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Low energy electrons (often referred to as "electron clouds") in the beam chambers of high intensity accelerators and storage rings can limit their performance. They can limit intensity by causing instabilities, unacceptable pressure increases or increases in beam size. Thus, reliable simulations of electron cloud generation in the Los Alamos high intensity Proton Storage Ring (PSR) and similar machines would be a most valuable tool for improving our understanding of its origin, the parameters that affect it and how it might be controlled. Such tools would provide cost-effective methods for designing mitigation measures and evaluating them before going to the expense of fabrication and experimental testing in an operating accelerator facility. In this project we have developed and tested several significant improvements to a widely used electron cloud simulation code, POSINST. In our version, LANLPOSINST V6, we have add several important features including the capability to model a multi-element section of the ring consisting of two quadrupole magnets with 3-dimensional magnetic fields, dipole magnet end fields, several drift spaces and various electron cloud diagnostics. Improvements were also added to the modeling of the initial primary or seed electrons from proton beam losses. One important conclusion from benchmarking these improvements was the need to include seed electrons produced from secondary particles resulting from the primary proton beam losses.
The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off—axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.
A short-pulse mode (otherwise known as pulse stacking) has long been pursued as the initial purpose of the Los Alamos Proton Storage Ring (PSR) c. 1979 and since then as an addition to the WNR facility to measure a variety of neutron cross sections important to many Lab missions.
A frequently used method for generation of terahertz wavelengths is based on transition radiation. A relativistic beam impinges a metal foil at 45 degrees and the radiation is collected and focused onto an image plane at 90 degrees relative to the beam orbit. While there are computer codes available to calculate the electric field at the focus, it is desirable to have a simple theory that would allow a quick estimate of the fields and provide scaling relations between the beam parameters and those of the radiation. The goal of this paper is to develop such a theory. It follows the original calculations done by Lebedev and Loos and extends those from the frequency to the time domain. While in reality the transport line for the THz radiation may have several focusing elements, to simplify analysis, we consider the setup shown in Fig. 1 with a single lens that provides the focusing. The numerical aperture of the lens $\theta_a$ is assumed to be much larger than the inverse gamma factor, $\theta_a \gg 1/\gamma$.
We calculate the electric currents induced in a metal foil by an impinging relativistic beam and the foil heating due to the ohmic losses in the foil. Conditions when the foil melts are obtained and calculated for three metals: titanium, beryllium and tungsten, and for several beam parameters relevant for the FACET experiment at SLAC.
Summary (in advance): Longitudinal space-charge effects manifest themselves in several fascinating ways: – Self-consistent stationary longitudinal distribution – Synchrotron modes shifts with beam current; These effects are easily accessible in low-energy electron-cooled ion beams; This talk is based on my research at the Indiana University Cyclotron Facility (IUCF) Cooler, but easily applicable to all other cooler rings.
To estimate the vertical impedance of more complex geometry as an In-Vacuum Undulator we crosschecked first the results for simplified geometries. Axially symmetric tapered structures and rectangular structures are under discussion. Comparisons of analytical results with numerical results obtained with the electromagnetic field solver GdfidL are presented. Intensive studies were carried out to determine the dependence of the wake potential and kick factor on the collimator’s geometric parameters. We discuss the relationship of our results to the earlier work of G. Stupakov.
Abstract not provided.
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This final technical report summarizes the development of structure wakefield accelerator (SWFA) technology to enable high-gradient, efficient particle acceleration.
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He-Ne laser light intensity distribution cumulants for nonlinear oscillation threshold operation