Single-invariant nonlinear optics for a small electron recirculator

Abstract

This paper describes the design and simulation of a proof-of-concept quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). This experiment tests the feasibility of nonlinear integrable optics, a novel technique that is expected to mitigate resonant beam loss and enable low-loss high-intensity beam transport in rings. Integrable lattices with large amplitudedependent tune spreads, created by nonlinear focusing elements, are proposed to damp beam response to resonant driving perturbations while maintaining large dynamic aperture [Danilov and Nagaitsev, PRSTAB, 2010]. At UMER, a lattice with a single octupole insert is designed to test the predictions of this theory. The planned experiment employs a low-current high-emittance beam with low space charge tune shift (∼ 0.005) to probe the dynamics of a lattice with large externally-induced tune spread. Design studies show that a lattice composed of a 25-cm octupole insert and existing UMER optics can induce a tune spread of ∼ 0.13. Stable transport is observed in PIC simulation for many turns at space charge tune spread 0.008. A maximum spread of ∆ν = 0.11 (RMS 0.015) is observed for modest octupole strength (peak 50 T /m 3 ). A simplified model of the system explores beam sensitivity to steering and focusing errors. Results suggest that control of orbit distortion to < 0.2 mm within the insert region is essential. However, we see only weak dependence on deviations of lattice phase advance (≤ 0.1 rad.) from the invariant-conserving condition.

Rapid-cycling synchrotron for multi-megawatt proton facility at Fermilab

“…Two technologies under development at FAST/IOTA, Nonlinear integrable optics is an innovation in acceleration design to provide immense nonlinear focusing without generating parametric resonances [83]. Nonlinear lattices which preserve at least one invariant of motion have also demonstrated an improvement in dynamic aperture over conventional nonlinear lattice design [84,85].…”

Hamiltonian preserving nonlinear optics

“…We consider a lattice that is implemented in IOTA [6] and UMER [7] for the quasi-integrable and integrable optics experiments. The linear part of the lattice consists of the so called T-insert introduced in [2], and a drift of length L. The T-insert is an arrangement where part of the linear optics effectively acts as a focusing matrix in both x and y directions, leading to a degenerated case of equal transverse β-functions in a drift space.…”

“…[2], the concept has been expanded to more realistic cases with space charge and chromaticity effects accounted for [3,4]. Experimental demonstration of the integrable optics concept is currently being conducted at the IOTA facility at Fermilab [5,6] as well as at UMER ring at the University of Maryland [7].…”

“…The system is arranged in a way that the effective Hamiltonian for the lattice is almost time-independent and the potential produced by one nonlinear magnet warrants separation of variables, and thus a second integral of motion [2,8]. Initial designs of the nonlinear insert considered for both experiments [6,7] were based on an idea of approximating the smooth nonlinear potential with a certain number of nonlinear magnets (17 in the case of IOTA and 7 in the case of UMER) with their strength scaled according to a prescription derived in Ref. [2] and placed equidistantly.…”

Derivative-Free Optimization of a Rapid-Cycling Synchrotron

“…A promising application of integrable optics is in high-intensity rings, where nonlinearities are known to suppress the formation of beam halos [15,16,52] and enhance Landau damping of charge-dominated collective instabilities [31]. Over the next several years, the application of nonlinear integrable optics for intense beams will be studied experimentally at the Fermilab Accelerator Science and Technology Integrable Optics Test Accelerator (IOTA) [5,50], as well as smaller-scale test accelerators at the University of Maryland [45] and at the Rutherford Appleton Laboratory [32].…”