Short-bunch extraction in a rapid cycling synchrotron

Abstract

Short bunch beams of high intensity are required by many applications, and they are usually obtained by using bunch compression before the extraction in relatively slow cycling synchrotrons or accumulator rings. In this article, short bunch extraction by the bunch compression method is proposed to apply to a rapid cycling synchrotron (RCS) where the time duration is very limited to exploit the bunch compression process. The method is practically applied in the RCS of the China Spallation Neutron Source (CSNS) to obtain short-bunch beams for white neutron applications. Different short-bunch extraction scenarios have been studied, from keeping full beam power to reduced beam powers. A special desynchronization method is designed to solve the problem of slow acceleration during the bunch rotation process when the magnetic field is still ramping up. The space charge effect and beam loading effect during the bunch compression have also been taken into account in this high-intensity RCS. Multiparticle simulations have been carried out to show the effectiveness of the method with the input of the CSNS RCS. With a sacrifice of about twothirds of the beam power, the rms bunch length of the extracted beam can be reduced to about one-ninth of the one in the nominal operation mode.

Back-n white neutron facility at CSNS and first-year nuclear data measurements

“…This poses special difficulties for the measurements concerning the neutrons with energy higher than a few keV. To solve this problem, two measures have been taken: one is to develop different dedicated operation modes for the CSNS accelerators to obtain short-bunch or single bunch proton beams [20]; the other is to develop the unfolding method to deconvolute the two bunches in one pulse. Both the single bunch mode and the unfolding method have been successfully applied to the experiment of the neutron energy spectrum measurement [21].…”

Back-n white neutron facility for nuclear data measurements at CSNS

“…However, for nuclear data measurements with a wide energy range from 1 eV to 30 MeV and time resolution of usually less than 1% or even 0.1%, it is very important to control the pulse length of the proton beam, especially for the measurements with fast neutrons in the MeV range. Therefore, different CSNS accelerator operation modes have been studied to provide short proton pulses [15]. As we should try to keep the maximum available beam power for all applications, those modes with the sacrifice of beam power will be applied in very limited time in an average year, and need special arrangement from the user committee.…”

Neutron beam line design of a white neutron source at CSNS

“…The production, moderation, and transport of neutrons in the target have been simulated using FLUKA [6]. A proton beam window Different operation modes have been developed for the CSNS accelerator to provide neutron beams for different nuclear data measurements [7]. The smallest bunch width is 1.5 ns (rms).…”