MAGNETOOPTIC STRUCTURES FOR SYNCHROTRONS WITH NEGATIVE MOMENTUM COMPACTION FACTORS

Yu.V. Senichevª¹²

¹Institut für Kernphysik, Forschungszentrum Jülich GmbH, Jülich, Deutsch

²Institute for Nuclear Research of Russian Academy of Sciences, Moscow, Russia

Abstract

In synchrotrons the transition energy W_tr=m₀c²(γ_tr- 1) is fundamentally important because it determines the maximum attainable accelerated currents. From this point of view it is desirable that the momentum compaction factor α= 1/γ_tr² be as small as possible or even negative, which makes γ_tr imaginary and accordingly rules out transition energy crossing by particles under acceleration.

On the basis of the theory of "resonant" lattices for synchrotrons with complex transition energy developed in [1, 2], examples of such lattice with application to various accelerators are proposed.

The "resonant" lattice was first proposed for the Moscow Kaon Factory [3]. This lattice was then adapted for the TRIUMF KAON Factory [4]. Later it was considered as the best candidate for the Low Energy Booster of Superconducting Super Collider [5], then was adopted for the main accelerator of the Neutrino Factory at CERN [6], and ultimately was implemented in the Japan Protons Accelerator Research Center [1, 7]. In the Superconducting option of High Energy Storage Ring lattice of the FAIR project the same idea is also accepted [8]. At present the "resonant" lattice is one of the candidates for PS2 in CERN [9].

The "resonant" lattice is appeared to be useful for electron machines as well. In particular, in the electron-positron collider type a small momentum-compaction factor is needed to reduce the synchrotron tune, while keeping the bunch length and momentum spread constant [1]. In synchrotron-light sources the minimum momentum-compaction factor and the minimum modulation of the dispersion function are both required simultaneously to have a small horizontal emittance [10, 11].

ª – corresponding author

Paper Slides

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