Searcharxiv⌕ Search

arXiv · physics/0209074

Impedance Measurement Setup for Higher-Order Mode Studies in NLC Accelerator Structures with the Wire Method

Abstract

Dipole modes are the main cause of transverse emittance dilution in the Japanese Linear Collider / Next Linear Collider (JLC/NLC). A diagnostic setup has been built in order to investigate them. The method is based on using a coaxial wire to excite and measure electromagnetic modes of accelerating structures. This method can offer a more efficient and less expensive procedure than the ASSET facility. Initial measurements have been made and are presented in this paper.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

N. Baboi, R. M. Jones, J. W. Wang, G. B. Bowden, V. A. Dolgashev, J. Lewandowski, S. G. Tantawi, P. B. Wilson. 2002-09-20. Impedance Measurement Setup for Higher-Order Mode Studies in NLC Accelerator Structures with the Wire Method. https://arxiv.org/abs/physics/0209074

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

The problem of self-consistent particle phase space distributions for periodic focusing channels

Charged particle beams in equilibrium with their collective fields are represented by self-consistent phase space distributions. As the starting point, we assume the external focusing forces to act continuously on the beam. In the collisionless mean-field approximation, a broad class of stationary self-consistent particle phase space distributions can then be constructed. The method is reviewed how to determine the single-particle Hamiltonian of the focusing system for a given phase space density function. Subsequently, canonical transformations are used to relate this description to a beam passing through a non-continuous transport system. The correspondence is exact for the linear K-V model and provides an approximate matching prescription for distributions with nonlinear space-charge forces. The transverse Hamiltonian generally changes with the focusing strength, including in a rotationally symmetric periodic solenoid channel. Our computer simulations, presented in the second part of the paper, indicate very small rms-emittance changes for appropriately matched beams in the continuous and periodic solenoid channels investigated. The simulation for a periodic quadrupole channel yields a small persistent increase of the rms-emittance, whose physical interpretation requires control of numerical errors. Revised version of: Particle~Accelerators 39, 219--249 (1992)}

physics.acc-ph↗

Improved envelope and emittance description of particle beams using the Fokker-Planck approach

Beam dynamics calculations based on the collisionless Vlasov equation omit collisional correlations such as intra-beam scattering. For a short-correlated process dominated by small momentum changes, a Fokker-Planck equation can describe their effect on the one-particle distribution. From this equation we derive equations of motion for the beam envelopes and for the rms-emittances. Prescribed friction against an external bath is distinguished from momentum- and energy-conserving self-collisions. For the latter, an affine mean-flow approximation and a scalar relaxation coefficient give simple equations for temperature balancing within the beam. The longitudinal diffusion and temperature are expressed in terms of the physical random momentum rather than the signed effective longitudinal mass. The resulting growth-rate formulas apply to this reduced relaxation model. The original numerical examples are retained for comparison, with the limitations of the storage-ring and numerical-noise applications made explicit. Revised version of: Particle Accelerators~{\bf 45}, 229 (1994)

physics.acc-ph↗

Theoretical studies of envelope oscillations and instabilities of mismatched intense charged-particle beams in periodic focusing channels

The behavior of mismatched intense charged-particle beams in periodic transport channels of the solenoid and quadrupole type is studied theoretically. The envelope-oscillation frequencies of the mismatched beam are obtained by the smooth-approximation method and by numerical evaluation of the linearly perturbed K-V envelope equations. Phase shifts of the envelope oscillations and growth factors per focusing period in the case of instability are calculated for a solenoid and a magnetic quadrupole (FODO) channel using the parameters of the Maryland and GSI beam transport experiments. For comparison and the purpose of illustration, the K-V equations are integrated numerically, and envelope curves as well as single-particle trajectories for mismatched beams are shown in graphical form. In addition, computer simulation studies with the PARMILA code were performed, and results are presented both for K-V and a Gaussian distribution in transverse phase space.\\~\\ Revised version of: Particle~Accelerators~{\bf 14}, 227--260 (1984)}

physics.acc-ph↗