Michael F. Reusch

A problem related to Earnshaw's Theorem

An alternative to Earnshaws Theorem, based on perturbation theory, is discussed that predicts the stable or unstable behavior of classical electromagnetic physical systems in a two dimensional situation. >

High‐order optics with space charge: The TOPKARK code

TOPKARK is a three‐dimensional high‐order optics code that incorporates a simple space charge model. This code uses the differential algebra library DA to generate an arbitrary‐order Taylor map describing a given lattice, then the Lie algebra library LIELIB is used to obtain the Dragt‐Finn Factorization of the corresponding Lie polynomial. The Lie polynomial generated by TOPKARK without space charge has been successfully benchmarked through third order against MARYLIE 3.0 and through fifth‐order (for a single example) against TLIE. With space charge turned on, TOPKARK generates a linear map that agrees well with TRACE 3‐D. We describe here the various algorithms employed by TOPKARK and address the issue of verifying the high‐order map when space charge is turned on.

Design and operation of the Compact Infrared Free-Electron Laser (CIRFEL)

The Compact Infrared Free Electron Laser (CIRFEL) was built as part of a joint collaboration between Northrop Grumman and Princeton University to develop FELs for use by researchers in the materials, medical and physical sciences. The CIRFEL was designed to laser in the Mid-IR and Far-IR regimes with picosecond pulses, megawatt level peak powers and an average power of a few watts. The CIRFEL utilizes an RF photocathode gun to produce high-brightness time synchronized electron bunches. The micropulse separation is 7 nsec which allows a number of relaxation phenomena to be observed. In addition, the photocathode illumination laser can be used in combination with the FEL IR light for pump- probe experiments. The CIRFEL is presently being commissioned and working towards lasing. The present status of the machine is presented.

Particle tracking and map analysis for compact storage rings

Compact electron storage rings, like the BNL (Brookhaven National Laboratory) Superconducting X-ray Lithography Source, present a significant challenge to the accelerator designer. The Krakpot code, which has been developed to overcome some of the difficulties presented by these rings, is discussed. Some of the techniques employed in this code may find an application in other accelerators.<<ETX>>

Beam diagnostics and modeling in CIRFEL

Abstract In this paper results of phase stability measurements of the photocathode drive laser at different points in the drive laser system, as well as the electron current micro-pulse phase stability measurements results are reported. Summary results of CIRFEL bend modeling and emittance measurements are also described. Result of a 5th order perturbation model for wiggler focusing is also reported.

Effect of space charge forces on particle tracking and generation of high order maps

TOPKARK is a beam optics program consisting of two Fortran codes developed in parallel: a 3-D high-order mapping code and a particle tracking code; both utilize a space charge model which treats the particle bunch as a uniformly-filled 3-D ellipsoid. The map code uses the differential algebra library DA to generate an arbitrary-order Taylor map describing a given lattice, then the Lie algebra library LIELIB is used to obtain the Dragt-Finn factorization of the corresponding Lie polynomial. The Lie polynomial generated by TOPKARK without space charge has been successfully bench-marked through third order against MARYLIE 3.0 and through fifth order against TLIE. With space charge on, TOPKARK generates a linear map that agrees well with TRACE 3-D. The tracking code uses a symplectic integration scheme when space charge is off, and it includes a more general space charge model which assumes only ellipsoidal symmetry of the spatial distribution.<<ETX>>

Optimization of the end winding geometry of dipole magnets

A simple, almost entirely analytic method for the optimization of stress-reduced magnet-end winding paths for ribbonlike superconducting cable is presented. This technique is based on characterization of these paths as developable surfaces, i.e. surfaces show intrinsic geometry is flat. The method is applicable to winding mandrels of arbitrary geometry. Computational searches for optimal winding paths are easily implemented via the technique. Its application to the end configuration of the cylindrical SSC (Superconducting Super Collider) magnet is discussed. The method may be useful for other engineering problems involving the placement of thin sheets of material.<<ETX>>

Explicit Lie group integrators

In this paper, we review the theory of explicit symplectic integration. We present a non‐trivial application going beyond Ruth’s original paper. Finally, we contrast the explicit and the implicit methods by deriving a hybrid integrator for a special one dimensional Hamiltonian.

A beamline systems model for Accelerator‐Driven Transmutation Technology (ADTT) facilities

A beamline systems code, that is being developed for Accelerator‐Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G. H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance‐of‐plant and facility costing analysis will be performed externally. An interfacing external balance‐of‐plant and facility costing model, which will permit the performance of iterative facility trade studies, ...

High-order space charge effects using automatic differentiation

The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach.