Multi-physics analysis of a 325 MHz bi-periodic on-axis coupled accelerating structure

Purpose A 325-MHz bi-periodic on-axis coupled accelerating structure prototype which consists of two bi-periodic accelerating modules is under fabrication in the Institute of High Energy Physics,Beijing,dedicated to a 10-MeV/100 kW industrial linear electron accelerator.According to the beam dynamics study,the average power dissipated in the prototype cavity is about 19.1 kW.Effective cooling scheme is one of the most important issues in the high-power operation.Methods This paper mainly deals with the RF,thermal and structural coupled analyses of the accelerating structure prototype with the help of the ANSYS code.The cooling scheme is optimized to minimize the temperature rise,displacement and von Mises stresses.Results The temperature and stress distributions in the steady state are presented.The maximum von Mises stress is much lower than the yield strength limit of the corresponding material.The frequency shift caused by the thermal expansion is calculated as well,which is within the scope of the tuning range.Conclusion The coupled analyses based on the ANSYS software package are presented to design and optimize the cooling scheme of the accelerating structure.The von Mises stresses are much lower than the yield strength limit of the material.The calculation results indicate that our cooling scheme can deal with the dissipated RF power efficiently.

Visible and Infrared Band Tracking and Measuring Control System

This paper describes a new tracking and measuring control system for optical and electronic theodolite.This control system can provide automatic flying object tracking and measuring in visible and infrared band.It also can provide real-time output of the measured results.By using the multi-mode measuring methods and the on-axis tracking control technique, the stability of automatic tracking,tracking accuracy and the comprehensive tracking performance of the theodolite can be improved.At the same time the smooth switch-over among several tracking modes can be carried out.New tracking techniques have been developed to deal with angular tracking rate that exceed 60 deg/s in velocity and 90 deg/s 2 in acceleration.At the present the tracking and measuring control system has been successfully applied in the optical and electronic theodolite.

Multiple off-axis acoustic vortices generated by dual coaxial vortex beams

As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.

Simulation of Heating with the Waves of Ion Cyclotron Range of Frequencies in Experimental Advanced Superconducting Tokamak

Simulation on the heating scenarios in experimental advanced superconducting tokamak （EAST） was performed by using a full wave code TORIC. The locations of resonance layers for these heating schemes are predicted and the simulations for different schemes in ICRF experiments in EAST, for example, ion heating （both fundamental and harmonic frequency） or electron heating （by direct fast waves or by mode conversion waves）, on-axis or off-axis heating, and high- field-side （HFS） launching or low-field-side （LFS） launching, etc, were conducted. For the on-axis minority ion heating of 3He in D（3He） plasma, the impacts of both density and temperature on heating were discussed in the EAST parameter ranges.

Study on crab-cavity-based longitudinal injection scheme and prototype realization of C-band crab cavity for electron storage rings

A diffraction-limited storage ring with a multi-bend achromat lattice suffers from a small dynamic aperture for conventional off-axis injection.Thus,a longitudinal on-axis injection scheme based on a new type of crab cavity is proposed in this paper.Particle tracking simulations were performed to study the disturbance of the stored beam and the motion of the injected beam during the injection process.The possibility of multi-bunch injections was discussed.In addition,the effect of the long-range wake field induced by the stored beam was analyzed.A C-band standing-wave crab cavity was designed and produced as requested,and its field distribution was measured.The corresponding results are consistent with the simulation results.

Development of a 750-mm-long stripline kicker for HEPS

Purpose The superfast kickers are required for the HEPS storage ring on-axis injection system due to its very small dynamic aperture.A 750-mm-long stripline pair type of kicker prototype was researched and developed to demonstrate achieved performance of bandwidth,impedance,kicker strength,field uniformity and beam power loss.Methods The cross sections of the kicker main body and the end of taper part are optimized for a good impedance matching and field uniformity.3D simulation further optimizes the taper part to minimize the beam power loss and maintain a lower reflection.The high-voltage feedthrough is also designed and optimized by 3D CST.RF and high-voltage measurements are taken to verify the design of kicker assembly.Results The testing transmission odd-mode impedance is 50±0.5Ω,the even-mode impedance is 60±0.5Ω,and return loss is less than−13 dB.The peak voltage and the rise time of pulse width inserting kicker assembly just decrease 3%of 20 kV and slow down 80 ps,respectively.Conclusions RF testing results agree well with the simulation ones,which meet the design specification.The kicker assembly works well at±20 kV pulse.