MOP2WB05
UNIST, Ulsan, Republic of Korea
PPPL, Princeton, New Jersey, USA
Analysis of the small-amplitude perturbations around the matched beam envelope has been used as a basic theoretical framework to characterize the high-intensity beam transport. The beam stability properties in periodic quadrupole and solenoid channels have been analyzed by many authors in terms of that framework. In general, the linearized perturbed envelope equations are coupled. Therefore, application of the conventional Courant-Snyder theory to this problem has not been straightforward. In this work, we adopt the recently developed generalized Courant-Snyder formulation, and revisit the spectral and structural stability properties of the envelope perturbations. The generalized Courant-Snyder invariant of the envelope perturbations is identified, and its physical interpretation will be given. Since the generalized Courant-Snyder formulation can be easily extended to three-dimensional cases, we also investigate the three-dimensional envelope instability by means of the generalized Courant-Snyder formulation.
mchung@unist.ac.kr
GSI, Darmstadt, Germany
UNIST, Ulsan, Republic of Korea
HIM, Mainz, Germany
Mainz University, Mainz, Germany
Northern Illinois University, DeKalb, Illinois, USA
Northern Illinois Univerity, DeKalb, Illinois, USA
UNIST, Ulsan, Republic of Korea
Fermilab, Batavia, Illinois, USA
LBNL, Berkeley, California, USA
Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam.
UNIST, Ulsan, Republic of Korea
The IFMIF (International Fusion Material Irradiation Facility) project is being considered to build fusion material test facility. The IFMIF will use two accelerators to generate high energy neutrons. However, the IFMIF accelerators have been designed to have much higher beam power and beam current than the existing accelerators, so space charge effect is very strong. This raises big concerns about beam loss and beam transport stability, thus detailed high-intensity beam dynamics study of the IFMIF-like accelerators is indispensable. This research aims to perform source to target simulation of the IFMIF-like accelerator. The simulation has been carried out by two different kinds of simulation codes because the IFMIF accelerator has distinctive features. One is TRACEWIN simulation code which was used in IFMIF initial design. The other is WARP 3D PIC code which can precisely calculate space charge effects. This presentation will focus on beam simulations for LEBT, RFQ, and MEBT of the IFMIF accelerator
UNIST, Ulsan, Republic of Korea
Transport of intense beams over long distances can be restricted by space-charge fields which force the trajectories of charged particles to deviate from the stable regions of propagation. The space-charge fields can be calculated from the density distribution of the beam particles, and Poisson's equation. As the space-charge term is put in the equations of motion, it affects the envelope equations and betatron wave number of a charged particle in the beam. Also, with different initial conditions of the beam particles, there can be perturbations on the matched beam envelopes which can generate a resonant interaction between the beam core and test particles. Unlike for the K-V beam, for nonuniform density beams such as Gaussian beams in the periodic quadrupole or solenoidal focusing fields, there exists higher order terms and non-periodic solutions of beam particle oscillations, which can generate halo regions and chaotic motions during the beam propagation. In this study, we have investigated the higher order resonances and non-periodic solutions of the Gaussian beam in the solenoidal focusing fields to understand halo formation mechanisms of the intense beams.