The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, on-momentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm · rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.
A higher-harmonic cavity will be used to increase the beam lifetime and suppress coupled-bunch instabilities for Hefei Light Source-II. In this paper, the simulated results confirm that tuning in the harmonic cavity may suppress the parasitic coupled-bunch instabilities. The higher-harmonic cavity has been designed and the calculated factor of lifetime improvement is larger than 2.5.
The preliminary research work of Hefei Advanced Light
Facility (HALF), a fourth generation diffraction limit storage ring,
is in progress. Two 499.8 MHz superconducting cavities may be used
in the HALF RF system. RF power will be feed into each cavity
through a coaxial fundamental power coupler (FPC). Thermal design of
the coupler is very important because of the large power losses on
the coupler will cause overheating. Accurate and fast thermal
analysis is a challenge in the thermal design. In this paper, two
thermal analysis methods for evaluating the cooling effect of the
coupler were compared. Computational Fluid Dynamics (CFD) code is
used to perform thermal-fluid coupled analysis for the coupler in
the first method, which is quite accurate but time-consuming. In the
second method, average convective heat transfer coefficient
calculated by correlation equations based on experimental results is
used to evaluate the heat transfer between the fluid and the cooling
pipe wall. The calculation time of the first method is about four
times that of the second method. The simulation results of the two
methods are consistent well at high flow rate, especially for
turbulent flow. Therefore, the second method was used to perform
thermal simulation under different cooling conditions and RF power
levels. The influence of thermal radiation on the heat load to the
cryogenic environment was also given in this paper. Simulation
results show that thermal radiation has a slight impact on the heat
load. When the copper emissivity equal to 0.02, the total static and
dynamic heat load to 4.5 K are 0.833 W and 2.614 W at the power
level of 200 kW, and the heat load to 4.5 K cryogenic environment
caused by thermal radiation is 0.065 W.
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