Yuanji Pei

Tracking study of the new injection bump system of the HLS ring

Abstract In this paper, a summary of the existing three-kicker injection bump system of the HLS ring is presented and a new lattice-independent, four-kicker bump system which has been proposed for the second phase project of NSRL is described. Conditions for generating a bump orbit by four kickers are discussed. A theory of multiturn injection based on single-particle dynamics is introduced to analyse the conditions to achieve multiturn injection. Tracking study of the new system are carried out to verify the correctness of the scheme. Parameters such as dimension of the injected beam phase space ellipse, tolerance of the injected beam energy dispersion, timing jitter allowance of the kickers, etc., are calculated.

A proposed injection system for HLS

Abstract Hefei synchrotron radiation Light Source (HLS) presently has three kickers for electron injection. It is a lattice-dependent system, and different lattices will form different shapes of bump orbits. In the upgrading of HLS, a compact, lattice-independent injection system will be adopted. This paper looks into the possibilities of using quadrupole-magnet trim coils to produce assistant DC injection bumps and then to decrease the required amplitude of kicker bump. Some calculation results of injection schemes are discussed.

Study of beam transverse properties of a thermionic electron gun for application to a compact THz free electron laser

A novel thermionic electron gun adopted for use in a high power THz free electron laser (FEL) is proposed in this paper. By optimization of the structural and radiofrequency (RF) parameters, the physical design of the gun is performed using dynamic calculations. Velocity bunching is used to minimize the bunchs energy spread, and the dynamic calculation results indicate that high quality beams can be provided. The transverse properties of the beams generated by the gun are also analyzed. The novel RF focusing effects of the resonance cavity are investigated precisely and are used to establish emittance compensation, which enables the injector length to be reduced. In addition, the causes of the extrema of the beam radius and the normalized transverse emittance are analyzed and interpreted, respectively, and slice simulations are performed to illustrate how the RF focusing varies along the bunch length and to determine the effects of that variation on the emittance compensation. Finally, by observation of the variations of the beam properties in the drift tube behind the electron gun, prospective assembly scenarios for the complete THz-FEL injector are discussed, and a joint-debugging process for the injector is implemented.

Linear polarizing undulator and optical alignment system for a THz-FEL test facility

A Free Electron Laser oscillator with radiation wavelength 50-100 μm is under commissioning in Huazhong University of Science and Technology (HUST). Physical design of a linear polarizing undulator has been performed in HUST, with variable gap for K=1.0-1.25. The undulator was manufactured by Kyma s.r.l., by using a pure permanent magnet scheme. In December 2014, this undulator was installed in HUST and acceptance test showed main tolerances including rms phase error, field integrals corresponding variable gaps are well controlled. Design considerations related to physical and engineering issues, magnetic field performance are described. This paper introduces the development of an online field integrals measurement system for the undulator, using the stretched wire method. The design and considerations of the optical alignment system is described as well.

The Study of the Optical Cavity for a Compact Terahertz Source Based on Free Electron Lasers

In this paper some key technologies of an optical cavity for a compact Terahertz(THz) Source Based on Free Electron Lasers(FEL) were studied. Firstly, the theory of THz radiation was analyzed by some calculations. The high quality electronic bunch beams with energy 5.6-9.9MeV can produce THz radiation with frequency 1-10THz. Secondly, the configuration of the optical cavity was calculated and studied, and some conditions were discussed in order to obtain a single resonance mode. Thirdly, The loss caused by the diffraction and the coupling aperture was calculated. Finally, an idea of designing an optical cavity and some important data were given.

Possibility study of generating long SR pulse in HLS

Hefei Light Source (HLS) is a low energy Synchrotron Radiation (SR) facility. The interval of SR pulses is in the range 5/spl sim/220 ns. Some experiments need very long interval SR pulses with a strict time structure that HLS cannot provide. To meet the needs of these experiments, a scheme of local vertical bump is studied. Physical calculations and numerical simulations demonstrate the theoretical possibility, and a prototype fast kicker system has been built to demonstrate the technical possibility.

200‐MeV LINAC—injector of storage ring for HESYRL

The 200‐MeV electron linac at the Hefei National Synchrotron Radiation Laboratory (HESYRL) is described. It is not only an injector of the 800‐MeV storage ring, but an electron accelerator used for nuclear physics experiments and some other applications as well. The main design parameters and measuring results of the LINAC are given. The linac is a travelling wave structure, operating at a frequency of 2856 MHz, constant impedance, in a 2/3π mode. Its total length is about 35 m. Five klystrons are used as rf power; each klystron will provide 15 MW. In November 1987, the machine was successfully commissioned and typical operating parameters are 220 MeV, and 50 mA with an energy spread of ±0.8%.