David Douglas

Charged Particle Beam Transport Using Lie Albegraic Methods

Methods have recently been developed enabling one to describe charged particle beam transport in terms of a Lie algebraic representation. We show how this formulation may be applied to the problem of computing transfer maps (including aberrations) for the beam-line elements common in accelerator physics. In addition, explicit calculations are carried out for a variety of common elements including drift sections, static magnetic dipole, quadrupole, and sextupole lengths, and dynamic sectons such as bunchers. The resultant mappings are displayed, and provide a succinct basis for efficient numerical computation of charged particle beam behavior during transport.

MARYLIE: The Maryland Lie Algebraic Transport and Tracking Code

MARYLYE is a Fortran-language beam transport and tracking code developed at the University of Maryland which employs algorithms based on a Lie algebraic formalism for charged particle trajectory calculations and is designed to compute transfer maps for and trace rays through single or multiple beam-line elements. This is done without the use of numerical integration or traditional matrix methods; all nonlinearities, including chromatic effects, through third or octupole order are included. MARYLYE thus includes effects one order higher than those usually handled by existing matrix-based programs. Presently the following beam-line elements are described by MARYLYE: drifts; normal-entry and parallel-faced dipole bends; fringe fields for dipoles; hard-edged magnetic quadrupoles; fringe fields for quadrupoles; hard-edged magnetic sextupoles; hard-edged magnetic octupoles; axial rotations; RF bunchers; and a user specified transfer map through nonlinear terms of degree 3. Particle transport calculations, or ray traces, are carried out at speeds comparable to those of current matrix-based codes.

Multi-component measurements of the Jefferson Lab energy recovery linac electron beam using optical transition and diffraction radiation

DOI: http://dx.doi.org/10.1103/PhysRevSTAB.11.082801 High brightness electron accelerators, such as energy recovery linacs (ERL), often have complex particle distributions that can create difficulties in beam transport as well as matching to devices such as wigglers used to generate radiation from the beam. Optical transition radiation (OTR), OTR interferometry (OTRI) and optical diffraction-transition radiation interferometry (ODTRI) have proven to be effective tools for diagnosing both the spatial and angular distributions of charged particle beams. OTRI and ODTRI have been used to measure rms divergences and optical transverse phase space mapping has been demonstrated using OTRI. In this work we present the results of diagnostic experiments using OTR and ODR conducted at the Jefferson Laboratory 115 MeV ERL which show the presence of two separate components within the spatial and angular distributions of the beam. By assuming a correlation between the spatial and angular fe

Lie algebraic methods for particle tracking calculations

A study of the nonlinear stability of an accelerator or storage ring lattice typically includes particle tracking simulations. Such simulations trace rays through linear and nonlinear lattice elements by numerically evaluating linear matrix or impulsive nonlinear transformations. Using the mathematical tools of Lie groups and algebras, one may construct a formalism which makes explicit use of Hamiltons equations and which allows the description of groups of linear and nonlinear lattice elements by a single transformation. Such a transformation will be exactly canonical and will describe finite length linear and nonlinear elements through third (octupole) order. It is presently possible to include effects such as fringing fields and potentially possible to extend the formalism to include nonlinearities of higher order, multipole errors, and magnet misalignments. We outline this Lie algebraic formalism and its use in particle tracking calculations. A computer code, MARYLIE, has been constructed on the basis of this formalism. We describe the use of this program for tracking and provide examples of its application. 6 references, 3 figures.

ER@CEBAF, a 7 GeV, 5-Pass, Energy Recovery Experiment

A multiple-pass, high-energy ERL experiment at the JLab CEBAF will be instrumental in providing necessary information and technology testing for a number of possible future applications and facilities such as Linac-Ring based colliders, which have been designed at BNL (eRHIC) and CERN (LHeC), and also drivers for high-energy FELs and 4th GLS. ER@CEBAF is aimed at investigating 6D optics and beam dynamics issues in ERLs, such as synchrotron radiation effects, emittance preservation, stability, beam losses, multiple-pass orbit control/correction, multiple-pass beam dynamics in the presence of cavity HOMs, BBU and other halo studies, handling of large (SR induced) momentum spread bunches, and development of multiple-beam diagnostics instrumentation. Figure 1: 12 GeV CEBAF recirculating linac. Location of chicane and dump line for ER@CEBAF. Since it was launched 2+ years ago, the project has progressed in defining the necessary modifications to CEBAF (Fig. 1, Tab. 1, 2), including a 4-dipole phase chicane in recirculation Arc A, beam extraction and a dump line at the end of the south linac, and additional dedicated multiplebeam diagnostics. This equipment can remain in place to Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy, † and by Jefferson Science Associates, LLC under Contract No. DEAC05-06OR23177 with the U.S. Department of Energy. ‡ Spokesperson. fmeot@bnl.gov; satogata@jlab.org Table 1: Machine/Lattice Parameters of ER@CEBAF fRF 1497 MHz RF frequency Elinac 700 MeV Gain per linac (baseline) Einj 79 MeV = Elinac × 123/1090 φFODO 60 deg Per cell, at first NL pass and last SL pass M56 <90 cm Compression, Arc A Extraction 8 deg Angle to dump line

Suppression of Upstream Field Emission in RF Accelerators

This paper illustrates the idea of suppressing prevalent field emission in RF accelerators in the upstream direction with a rather minor change to the typical configuration, i.e. not requiring a modification to the accelerating structures, but the interconnecting beam tube lengths. An example is presented for a pair of superconducting RF cavities for simplification.

The Jefferson lab FEL driver ERLs

Jefferson Lab has - for over a decade - been operating high power IR and UV FELs using CW energy recovering linacs based on DC photocathode electron sources and CEBAF SRF technology. These machines have unique combinations of beam quality, power, and operational flexibility, and thus offer significant opportunity for experiments that use low and medium energy (several tens - few hundreds of MeV) electron beams. We will describe the systems and detail their present and near-term (potential) performance. Recent internal-target analysis and validation testing will be discussed, and schemes for single- and two-pass fixed target operation described. An introduction to subsequent discussions of beam quality and upgrade paths to polarized operation/higher energy will be given.