A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z    

Zhou, J.Z.

Paper Title Page
MPPT027 Three-Dimensional Design of a Non-Axisymmetric Periodic Permanent Magnet Focusing System 1964
 
  • C. Chen, R. Bhatt, A. Radovinsky, J.Z. Zhou
    MIT/PSFC, Cambridge, Massachusetts
 
  Funding: Work supported by the MIT Deshpande Center for Technological Innovation, the U.S. Department of Energy, High-Energy Physics Division, Grant No. DE-FG02-95ER40919, and the Air Force Office of Scientific Research, Grant No. F49620-03-1-0230.

A three-dimensional (3D) design is presented of a non-axisymmetric periodic permanent magnet focusing system which will be used to focus a large-aspect-ratio, ellipse-shaped, space-charge-dominated electron beam. In this design, an analytic theory is used to specify the magnetic profile for beam transport. The OPERA3D code is used to compute and optimize a realizable magnet system. Results of the magnetic design are verified by two-dimensional particle-in-cell and three-dimensional trajectory simulations of beam propagation using PFB2D and OMNITRAK, respectively. Results of fabrication tolerance studies are discussed.

 
TPAT002 Three-Dimensional Simulation of Large-Aspect-Ratio Ellipse-Shaped Charged-Particle Beam Propagation 823
 
  • R. Bhatt, C. Chen, J.Z. Zhou
    MIT/PSFC, Cambridge, Massachusetts
 
  Funding: U.S. Department of Energy: Grant No. DE-FG02-95ER40919, Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research: Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation.

The three-dimensional trajectory code, OMNITRAK, is used to simulate a space-charge-dominated beam of large-aspect-ratio elliptic cross-section propagating in a non-axisymmetric periodic permanent magnet focusing field. The simulation results confirm theoretical predictions in the paraxial limit. A realistic magnetic field profile is applied, and the beam sensitivity to magnet nonlinearities and misalignments is studied. The image-charge effect of conductor walls is examined for a variety of beam tunnel sizes and geometries.

 
TPAT003 Cold-Fluid Equilibrium of a Large-Aspect-Ratio Ellipse-Shaped Charged-Particle Beam in a Non-Axisymmetric Periodic Permanent Magnet Focusing Field 853
 
  • J.Z. Zhou, R. Bhatt, C. Chen
    MIT/PSFC, Cambridge, Massachusetts
 
  Funding: U.S. DOE, Grant: No. DE-FG02-95ER40919,Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research, Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation.

A new class of equilibrium is discovered for a large-aspect-ratio ellipse-shaped charged-particle beam in a non-axisymmetric periodic permanent magnet focusing field. A paraxial cold-fluid model is employed to derive the equilibrium flow properties and generalized envelope equations with negligibly small emittance. A periodic beam equilibrium solution is obtained numerically from the generalized envelope equations. It is shown that the beam edges are well confined in both transverse directions, and that the equilibrium beam exhibits a small-angle periodic wobble as it propagates. A two-dimensional particle-in-cell (PIC) code, PFB2D, is used to verify the theoretical predictions in the paraxial limit, and to establish validity under non-paraxial situations and the influence of the conductor walls of the beam tunnel.

 
FPAT030 Parametric Studies of Image-Charge Effects in Small-Aperture Alternating-Gradient Focusing Systems 2128
 
  • J.Z. Zhou, C. Chen
    MIT/PSFC, Cambridge, Massachusetts
 
  Funding: The U.S. Department of Energy, Office of High-Energy Physics, Grant No. DE-FG02-95ER40919, Office of Fusion Energy Science, Grant No. DE-FG02-01ER54662, and in part by Air Force Office of Scientific Research, Grant No. F49620-03-1-0230.

Image charges have important effects on an intense charged-particle beam propagating through an alternating-gradient (AG) focusing channel with a small circular aperture. This is especially true with regard to chaotic particle motion, halo formation, and beam loss.* In this paper, we examine the dependence of these effects on system parameters such as the filling factor of the AG focusing field, the vacuum phase advance, the beam perveance, and the ratio of the beam size to the aperture. We calculate the percentage of beam loss to the conductor wall as a function of propagating distance and aperture, and compare theoretical results with simulation results from the particle-in-cell (PIC) code PFB2D.

*Zhou, Qian and Chen, Phys. Plasmas 10, 4203 (2003).