Chun-xi Wang

Linear theory of transverse and longitudinal ionization cooling in a quadrupole channel.

Abstract Ionization cooling is the best-known cooling mechanism for the envisioned muon colliders and neutrino factories. In this paper, using the moment-equation approach, we present a linear theory of ionization cooling dynamics in 6D phase space in a quadrupole focusing channel. A simple set of differential equations that governs the evolution of both the transverse and longitudinal emittances is derived, and closed-form solutions are given. Two new significant heating processes have been identified. This theory is analogous to the standard linear theory in electron storage rings. Multiple scattering integrals and energy straggling integrals, quantities like the synchrotron radiation integrals, are introduced to specify the cooling process and the equilibrium emittances in a periodic cooling channel.

Magnetic field expansion in a bent-solenoid channel

Bent-solenoid channels are being considered for generating dispersions desired for emittance exchange between the transverse and longitudinal motions of a muon beam in a longitudinal ionization cooling channel. Correct field expansion around the reference orbit is important for reliable particle-tracking simulation as well as beam dynamics analysis. This paper reviews the magnetic field expansion for a bent-solenoid channel. In particular, ready-to-use formulas for the magnetic field and its potentials are given.

Dispersion in a bent-solenoid channel

Abstract Longitudinal ionization cooling of a muon beam is essential for muon colliders and will be useful for neutrino factories. Bent-solenoid channels with symmetric focusing has been considered for beam focusing and for generating the required dispersion in the “emittance exchange” scheme of longitudinal cooling. In this paper, we derive the Hamiltonian that governs the linear beam dynamics of a bent-solenoid channel, solve the single-particle dynamics, and give equations for determining the lattice functions, in particular, the dispersion functions.

BPM system evaluation using model-independent analysis

An effort is underway at the Advanced Photon Source (APS) to explore the Model-Independent Analysis method on the APS storage ring. Effective methods are developed to efficiently evaluate the beam position monitors (BPMs) performance and to easily identify the malfunctioning BPMs. Such a monitoring procedure can help to improve the overall reliability and performance of the BPMs, and thus benefit machine operation and physics studies. We show that the Model-Independent Analysis can resolve beam motion below the individual BPM resolution.

Progress in the linear beam dynamics study of ionization cooling channel

Abstract We review recent progresses in the study of linear beam dynamics of the ionization cooling in solenoidal focusing channels. The topics included are: understanding of the solenoidal focusing in the rotating frame; beam parameterization in terms of the envelope functions, emittance, and angular momentum; the coupled equation for emittance and angular momentum in periodic focusing channels; general solution and comparison with simulation; analytic approach for calculating the stability criteria and envelope function in periodic focusing channels.