He Xiaozhong

A simulation study of Tsinghua Thomson scattering X-ray source

Thomson scattering X-ray sources are compact and affordable facilities that produce short duration, high brightness X-ray pulses enabling new experimental capacities in ultra-fast science studies, and also medical and industrial applications. Such a facility has been built at the Accelerator Laboratory of Tsinghua University, and upgrade is in progress. In this paper, we present a proposed layout of the upgrade with design parameters by simulation, aiming at high X-ray pulses flux and brightness, and also enabling advanced dynamics studies and applications of the electron beam. Design and construction status of main subsystems are also presented.

Imaging beamline for high energy proton radiography

Proton radiography is a new tool for advanced hydrotesting. This article will discuss the basic concept of proton radiography first, especially the magnetic lens system. Then a scenario of 50 GeV imaging beamline will be described in every particular, including the matching section, Zumbro lens system and imaging system. The simulation result shows that the scenario of imaging beamline performs well, and the influence of secondary particles can be neglected.

A design study of a magnifying magnetic lens for proton radiography

Magnifying magnetic lenses can be used in high-energy proton microscopes. The −I lens suggested by Zumbro is analyzed in this paper, and a new type of magnetic lens called a lengthened lens is introduced. Theoretical analysis shows that the lengthened lens can form a magnifying lens, and at the same time the main advantages of a Zumbro lens are inherited. Using the My-BOC beam dynamics code, an example of the design is shown. The results show that the method of designing magnifying magnetic lenses is effective.

PRELIMINARY EXPERIMENT OF THE THOMSON SCATTERING X-RAY SOURCE AT TSINGHUA UNIVERSITY

The X-ray source based on Thomson scattering of ultrashort laser pulse with a relativistic electron beam is a means of generating a tunable, narrow bandwidth and ultrashort pulse of hard X-rays. Such a sub-picosecond hard X-ray source is proposed at Tsinghua University, and a preliminary experiment with a 16 MeV Backward Traveling electron linac and a 1.5 J, 6 ns Q-switched Nd:YAG laser is carried out first. A 6 ns pulse X-ray with a peak energy of 4.6 keV and an intensity of 1.7×104 per pulse is generated successfully in the experiment. The experimental setup, result and discussion are reported in this paper.

A preliminary study of a negative hydrogen PIG-type ion source for the compact cyclotron

A Penning ion gauge (PIG)-type ion source has been used for the generation of negative hydrogen ions (H−) as the internal ion source of the compact cyclotron. The discharge characteristics of the ion source are systematically studied for hydrogen operation at different discharge currents and gas flow rates on the prototype cyclotron. The preliminary study results for the low DC voltage H− extraction measurements are presented in this paper. The H− beam current is measured by the order of magnitude from several tens to hundreds of microamperes at different parameter conditions. The discussion and analysis for the experimental results are good for improving the design and working stability of the ion source.

Axial electric wake field inside the induction gap exited by the intense electron beam

While an intense electron beam passes through the accelerating gaps of a linear induction accelerator, a strong wake field will be excited. In this paper a relatively simple model is established based on the interaction between the transverse magnetic wake field and the electron beam, and the numerical calculation in succession generates a magnetic wake field distribution along the accelerator and along the beam pulse as well. The axial electric wake field is derived based on the relation between field components of a resonant mode. According to some principles in existence, the influence of this field on the high voltage properties of the induction gap is analyzed. The Dragon-I accelerator is taken as an example, and its maximum electric wake field is about 17 kV/cm, which means the effect of the wake field is noticeable.