Low-loss design for the high-intensity accumulator ring of the Spallation Neutron Source

Abstract

This paper summarizes the low-loss design for the Spallation Neutron Source accumulator ring ["Spallation Neutron Source Design Manual" (unpublished)]. A hybrid lattice consisting of FODO arcs and doublet straights provides optimum matching and flexibility for injection and collimation. For this lattice, optimization focuses on six design goals: a space-charge tune shift low enough ( below 0.15) to avoid strong resonances, adequate transverse and momentum acceptance for efficient beam collimation, injection optimized for desired target beam shape and minimal halo development, compensation of magnet field errors, control of impedance and instability, and prevention against accidental system malfunction. With an expected collimation efficiency of more than 90%, the uncontrolled fractional beam loss is expected to be at the 10 24 level.

Half-integer resonance crossing in high-intensity rings

“…In this paper we demonstrate the validity of collective beam response to betatron resonances using as an example the Spallation Neutron Source (SNS) accumulator ring which is currently under construction [1]. We also describe the main features of beam envelope resonant response and its application to the space-charge limit in the high-intensity rings.…”

Final test results for the SNS ring dipoles

“…The SNS accumulator ring [2] will contain 32 sector dipoles. To accommodate the high intensity proton beam, the magnet aperture is large.…”

Upgrading the AGS to 1 MW proton beam power

“…The duty cycle is about 0.5 %. The injection into the AGS is modeled after the SNS [2]. However, the The AGS injection parameters are summarized in Table 2.…”