arXiv subjects

Yi Jiao

Publications and source records attributed to Yi Jiao.

22 records · Page 2Linked to original sources

arXiv2014

Suppression of the emittance growth induced by coherent synchrotron radiation in triple-bend achromats

The coherent synchrotron radiation (CSR) effect in a bending path plays an important role in transverse emittance dilution in high-brightness light sources and linear colliders, where the electron beams are of short bunch length and high peak current. Suppression of the emittance growth induced by CSR is critical to preserve the beam quality and help improve the machine performance. It has been shown that the CSR effect in a double-bend achromat (DBA) can be analyzed with the two-dimensional point-kick analysis method. In this paper, this method is applied to analyze the CSR effect in a triple-bend achromat (TBA) with symmetric layout, which is commonly used in the optics designs of energy recovery linacs (ERLs). A condition of cancelling the CSR linear effect in such a TBA is obtained, and is verified through numerical simulations. It is demonstrated that emittance preservation can be achieved with this condition, and to a large extent, has a high tolerance to the fluctuation of the initial transverse phase space distribution of the beam.

physics.acc-ph↗

arXiv2014

PEPX-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light source, called diffraction-limited storage ring (DLSR), with the emittance approaching the diffraction limit for multi-keV photons by using the multi-bend achromat lattice, has attracted worldwide and extensive studies of several laboratories, and been seriously considered as a goal of upgrading the existing facilities in the imminent future. Among various DLSR proposals, the PEPX design based on the third-order achromat concept and with the special design of a high-beta injection straight section demonstrated that, it is feasible to achieve sufficient ring acceptance for off-axis injection in a DLSR. For the High Energy Photon Source planned to be built in Beijing, PEPX-type lattice has been designed and continuously improved. In this paper, we report the evolution of the PEPX-type design, and discuss the main issues relevant to the linear optics design and nonlinear optimization.

physics.acc-ph↗

arXiv2013

BBU effect in an ERL-FEL two-purpose test facility

Both the Energy Recovery Linac (ERL) and Free Electron laser (FEL) are considered to be candidates of the fourth generation light source. It is proposed to combine FEL into an ERL facility to integrate the advantages of both ERL and FEL, and to realize a compact two-purpose light source. A test facility to verify this principle is being designed at the Institute of High Energy Physics, Beijing. One main concern is the beam breakup (BBU) instability which limits the available beam current. To this end, we developed a numerical simulation code to calculate the BBU threshold, which is found to have only a small reduction even in a high-FEL-bunch-charge operation mode, compared with that in the case with ERL bunches only. However, even with ERL beam current far below BBU threshold, we observed a fluctuation of the central orbit of the ERL bunches in the presence of FEL beam. We then present a physical model of BBU and understand the mechanism of the orbit-fluctuation in an ERL-FEL two-purpose machine. We found that by choosing an appropriate FEL bunch repetition rate, the central orbit fluctuation amplitude can be well controlled.

physics.acc-ph↗

arXiv2013

Pulsed sextupole injection for Beijing Advanced Photon Source with ultralow emittance

In this paper we present the physical design of the pulsed sextupole injection system for Beijing Advanced Photon Source (BAPS) with an ultralow emittance. The BAPS ring lattice is designed in such a way that two options of pulsed sextupole injection are allowed, i.e., with septum and pulsed sextupole in different drift spaces or in the same drift space. We give the magnetic parameters of the injection system and the optimal condition of the optical functions for both options. In addition, we find that the pulsed sextupole induces position-dependent dispersive effect and causes non-ignorable effect on the injection efficiency in a storage ring with a relatively small acceptance, which should be well considered.

physics.acc-ph↗