Design and experimental results of a 28 GHz,400 kW gyrotron for electron cyclotron resonance heating

A high-power 28 GHz gyrotron has been successfully developed at the Institute of Applied Electronics,China Academy of Engineering Physics.This gyrotron was designed for electron cyclotron resonance heating(ECRH)in the spherical tokamak XL-50.A diode magnetron injection gun was designed to produce the required gyrating electron beam.The gyrotron operates in the TE8,3mode in a cylindrical open cavity.An internal quasi-optical mode converter was designed to convert the operating mode into a fundamental Gaussian wave beam and separate the spent electron beam from the outgoing microwave power.A tube has been built and successfully tested.The operational frequency of the tube is 28.1 GHz.For beam parameters at an accelerating voltage of 71 kV and beam current of 16 A,the gyrotron has delivered an output power of 400 kW,with a pulse length of 5 s.The output efficiency is about 50%with a singlestage depressed collector.The gyrotron has been installed on the XL-50 and has played an important role in the ECRH experiments.

Design and preliminary test of a 105/140 GHz dual-frequency MW-level gyrotron

A dual-frequency(105/140 GHz)MW-level continuous-wave gyrotron was developed for fusion application at Institute of Applied Electronics,China Academy of Engineering Physics.This gyrotron employs a cylindrical cavity working in the TE18,7 mode at 105 GHz and the TE24,9 mode at 140 GHz.A triode magnetron injection gun and a built-in quasi-optical mode converter were designed to operate at these two frequencies.For the proof-test phase,the gyrotron was equipped with a single-disk boron nitride window to achieve radio frequency output with a power of~500 k W for a short-pulse duration.In the preliminary short-pulse proof-test in the first quarter of2021,the dual-frequency gyrotron achieved output powers of 300 k W at 105 GHz and 540 k W at140 GHz,respectively,under 5 Hz 1 ms continuous pulse-burst operations.Power upgrade and pulse-width extension were hampered by the limitation of the high-voltage power supply and output window.This gyrotron design was preliminarily validated.

Hierarchically electrospraying a PLGA@chitosan sphere-in-sphere composite microsphere for multi-drug-controlled release

Sequential administration and controlled release of different drugs are of vital importance for regulating cellular behaviors and tissue regeneration,which usually demands appropriate carriers like microspheres(MS)to control drugs releases.Electrospray has been proven an effective technique to prepare MS with uniform particle size and high drug-loading rate.In this study,we applied electrospray to simply and hierarchically fabricate sphere-in-sphere composite microspheres,with smaller poly(lactic-co-glycolic acid)MS(~8-10 lm in diameter)embedded in a larger chitosan MS(~250-300 lm in diameter).The scanning electron microscopy images revealed highly uniform MS that can be accurately controlled by adjusting the nozzle diameter or voltage.Two kinds of model drugs,bovine serum albumin and chlorhexidine acetate,were encapsulated in the microspheres.The fluorescence-labeled rhodamine-fluoresceine isothiocyanate(Rho-FITC)and ultraviolet(UV)spectrophotometry results suggested that loaded drugs got excellent distribution in microspheres,as well as sustained,slow release in vitro.In addition,far-UV circular dichroism and matrixassisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS)results indicated original secondary structure and molecular weight of drugs after electrospraying.Generally speaking,our research proposed a modified hierarchically electrospraying technique to prepare sphere-in-sphere composite MS with two different drugs loaded,which could be applied in sequential,multi-modality therapy.

Development of an antimicrobial peptide-loaded mineralized collagen bone scaffold for infective bone defect repair

The repair of infective bone defects is a great challenge in clinical work.It is of vital importance to develop a kind of bone scaffold with good osteogenic properties and long-term antibacterial activity for local anti-infection and bone regeneration.A porous mineralized collagen(MC)scaffold containing poly(D,L-lactide-co-glycolic acid)(PLGA)microspheres loaded with two antibacterial synthetic peptides,Pac-525 or KSL-W was developed and characterized via scanning electron microscopy(SEM),porosity measurement,swelling and mechanical tests.The results showed that the MC scaffold embedded with smooth and compact PLGA microspheres had a positive effect on cell growth and also had antibacterial properties.Through toxicity analysis,cell morphology and proliferation analysis and alkaline phosphatase evaluation,the antibacterial scaffolds showed excellent biocompatibility and osteogenic activity.The antibacterial property evaluated with Staphylococcus aureus and Escherichia coli suggested that the sustained release of Pac-525 or KSL-W from the scaffolds could inhibit the bacterial growth aforementioned in the long term.Our results suggest that the antimicrobial peptides-loaded MC bone scaffold has good antibacterial and osteogenic activities,thus providing a great promise for the treatment of infective bone defects.