Phase-stabilized RF transmission system based on LLRF controller and optical delay line

Radio frequency(RF)transmission systems with high-precision phase stability are required by the next generation of particle colliders and light sources.An RF transmission system was designed to meet this requirement.In this system,RF signal generated at the sending end is modulated onto a continuous wave(CW)optical carrier,transmitted through an optical fiber,and demodulated at the receiving end.The phase drift is detected by a digital phase monitor with femtosecond-level accuracy and compensated by a motorized optical fiber delay line(ODL).The measurement results show that the long-term phase drifts can be stabilized to within 100 fs(pk-pk),500 fs(pk-pk),and 1.8 ps(pk-pk)in a 400-meter-long optical fiber over 1 h,24 h,and 10 days,respectively.

Waveguide distribution system of the HEPS linac

Purpose The High-Energy Photon Source(HEPS)is a 6 GeV storage ring-based light source under construction in Beijing,China.Its accelerator consists of a 6 GeV storage ring,a full-energy booster,an S-band normal-conducting 500 MeV linac,and three transport lines.As the beginning of HEPS,a stable linac is quite important,which needs a qualified waveguide distribution system to transmit microwave power from klystrons to accelerating structures.Methods Installation and high-power conditioning of the HEPS linac were performed from February to September 2022.The assembly and conditioning of the waveguide distribution system were completed in April and July,respectively.The design of the waveguide distribution system began in 2018 and was finalized at the end of 2020 after multiple iterations.Results Owing to careful design,fabrication,and assembly preparation,the assembly and conditioning of the system proceeded smoothly and considerable time was saved.Conclusion The entire process from the design to the ultimate realization of the system is introduced in detail in this paper.Satisfactory measurement results were obtained for some waveguide components.

Guanidinoamidized Linear Polyethyleneimine for Gene Delivery

Guanidine was introduced to low molecular weight linear polyethyleneimine （LPEI） via amide groups, to explore the effect of both guanidine degree and pendant chain length on its transfection behavior. The resulting guanidinoamidized LPEIs （GLPEIs） could dramatically reduce LPEI＇s toxicity, enhance its DNA-packaging capability, cellular uptake and therefore transfection efficiency. These polyplexes were taken up very efficiently via caveolae-mediated endocytosis and their transfection efficiencies in ovarian cancer cells were significantly improved compared to native LPEIlok polyplexes. Among these GLPEIs, LPEI-C3-G100 showed higher DNA affinity even than LPEI25k and the highest transfection efficiency, probably due to the optimization of polymer chain flexibility. Of notice, LPEI-C3-G100 polyplexes could more effectively accumulate into cytoplasm than LPEI25k, although the transfection efficiency of LPEI-C3-G100 polyplexes was not superior to that of LPEI25k polyplexes, which would be probably attributed to the more efficient release of LPEI25k polyplexes than LPEI-C3-G100 polyplexes in the cytoplasm.