arXiv subjects

Boaz Nash

Publications and source records attributed to Boaz Nash.

4 recordsLinked to original sources

arXiv2026

Elaboration on the kinetic approach of Derbenev and Kondratenko to spin-polarized beams in electron storage rings

We present a detailed account of the kinetic approach for describing the effect of synchrotron radiation on electron and positron spin polarization in storage rings. This approach was introduced in 1974 by Derbenev and Kondratenko and was extended by us since 2001. The kinetic approach is much less frequently utilized but it is more general than the original non-kinetic approach of Derbenev and Kondratenko from 1972 since the kinetic approach is not centered on the invariant spin field. As with the non-kinetic approach the kinetic approach covers the radiative depolarization effect, the Sokolov-Ternov effect and its Baier-Katkov correction as well as the kinetic polarization effect but it enables the calculation of corrections to the original Derbenev-Kondratenko formulas and thereby provides estimates of the reliability of the latter. The kinetic approach is applicable to storage rings with energies from a few GeV up to the energies of the FCC-ee and CEPC and beyond. The kinetic approach is based on the spin-orbit Wigner functions which lead to the so-called Bloch equation for the polarization density which is a generalization of Fokker-Planck equations to spin motion. In turn, as discovered in 2019, the Bloch equation is based on stochastic ordinary differential equations which can be used to develop Monte-Carlo spin tracking codes covering the key effects beyond the radiative depolarization effect. These stochastic ordinary differential equations lead to a new viewpoint of the physical effects, in particular the kinetic polarization effect.

physics.acc-ph↗

arXiv2023

Optimization of Magnetized Electron Cooling with JSPEC

The Electron-Ion-Collider (EIC) will be a next-generation facility located at Brookhaven National Laboratory (BNL), built with the goal of accelerating heavy ions up to 275 GeV. To prevent ion beam size growth during the acceleration phase, cooling techniques will be required to keep the beam size from growing due to intra-beam scattering. The JSPEC (JLab Simulation Package for Electron Cooling) $\texttt{C++}$ package is a tool designed to numerically model magnetized and unmagnetized cooling through friction forces between co-propagating electron and ion bunches. Here we describe a feature that has been added to the JSPEC package, which implements a Nelder-Mead Simplex optimization algorithm to allow a user to optimize certain beam parameters in order to achieve a target cooling time.

physics.acc-ph↗

arXiv2023

Propagation of a Gaussian Wigner Function Through a Matrix-Aperture Beamline

In the framework of statistical optics, a Wigner function represents partially coherent radiation. A Gaussian Wigner function, which is an equivalent representation of the more commonly used Gaussian Schell-model cross-spectral density, may be defined in terms of its covariance matrix and centroid. Starting from the relationship between Gaussian Wigner functions and the Gaussian Schell model, we derive coherence properties of the Gaussian Wigner function, including coherence length and degree of coherence. We define a simplified beamline called a matrix-aperture beamline composed of linear transport sections separated by physical apertures. This is an idealized form for a transport beamline in a synchrotron light source or X-ray free electron laser. An envelope model provides a basic foundation for understanding the optics of a given beamline, in a manner analogous to how linear optics are treated in particle beam dynamics, with corresponding definitions of emittance and Twiss parameters. One major challenge to such an envelope model lies in the hard-edge apertures which break the Gaussian condition, raising the question as to the adequacy of a Gaussian model. We present a consistent way to construct a Gaussian approximation of the far-field Wigner function following the hard edge aperture. To this end, we introduce the concept of a Gaussian aperture and analyze its effects on the radiation Wigner function. A software implementation of this model is described as well.

physics.acc-ph↗

arXiv2020

Propagation of partially coherent radiation using Wigner functions

Undulator radiation from synchrotron light sources must be transported down a beamline from the source to the sample. A partially coherent photon beam may be represented in phase space using a Wigner function, and its transport may use some similar techniques as is familiar in particle beam transport. We describe this process in the case that the beamline is composed of linear focusing and defocusing sections as well as apertures. We present a compact representation of the beamline map involving linear transformations and convolutions. We create a 1:1 imaging system (4f system) with a single slit on the image plane and observe the radiation downstream to it. We propagate a Gaussian beam and undulator radiation down this sample beamline, drawing parameters from current and future ultra low emittance light sources. We derive an analytic expression for the partially coherent Gaussian case including passage through a single slit aperture. We benchmark the Wigner function calculation against the analytical expression and a partially coherent calculation in the Synchrotron Radiation Workshop (SRW) code.

physics.acc-ph↗