In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiat...In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.展开更多
A gsnl4 mutant characterized by small grain size,narrow leaf and low seed-setting rate was obtained by ethyl methane sulfonate(EMS)mutagenesis of a japonica rice variety Wuyunjing 21.Genetic analysis showed that gsnl4...A gsnl4 mutant characterized by small grain size,narrow leaf and low seed-setting rate was obtained by ethyl methane sulfonate(EMS)mutagenesis of a japonica rice variety Wuyunjing 21.Genetic analysis showed that gsnl4 is a loss-of-function mutant.A single-base mutation in gsnl4 resulted in the substitution of Ser to Asn in the Piwi domain of OsAGOlb protein.CRISPR/Cas9-mediated editing of OsAGOlb yielded a mutant phenotypically resembling gsnl4.Furthermore,miRNA-Seq analysis showed that the transcript expression levels of miRNAs in the signal transduction pathways related to pollen development,leaf morphology and honnone activation were significantly different between the gsnl4 mutant and the wild type(WT)plants.Several miRNAs were downregulated,and their target genes were upregulated in gsnl4 mutants.The auxin content in the root tips of the gsnl4 mutant decreased,and the expression of most auxin-related genes was altered.In summary,GSNL4 not only regulates organ development by controlling cell division and expansion,but also plays an important role in regulating auxin transport in rice.展开更多
The HIAF High Intensity heavy Ion Accelerator Facility is under construction in Huizhou City,Guangdong,China^([1]).To fulfill the demand of frontier research in nuclear physics,astrophysics,atomic physics,and high ene...The HIAF High Intensity heavy Ion Accelerator Facility is under construction in Huizhou City,Guangdong,China^([1]).To fulfill the demand of frontier research in nuclear physics,astrophysics,atomic physics,and high energy density physics,HIAF aims to provide the ambitious beam intensity of pulsed heavy ions with the energy range of several hundred MeV/u up to GeV.展开更多
Purpose To protect accelerator devices from being damaged by high-power beam,a new beam dump system is under design for HIAF-BRing.Method Based on the optical characteristics,unwanted particles are safely deflected to ...Purpose To protect accelerator devices from being damaged by high-power beam,a new beam dump system is under design for HIAF-BRing.Method Based on the optical characteristics,unwanted particles are safely deflected to a specific internal absorber through a local bump orbit generated by active-discharging magnets,which is achieved by paralleling a bleeder resistor of 600 m�to two of dipole magnet power supplies.Results Taking alignment and multipolefield errors into account,discarded beam can be dumped within 5 ms with an efficiency of more than 99.8%at any operation stage.Conclusion The proposed beam dump solution satisfies the machine protection requirements for BRing and can provide a new idea for similar facilities.展开更多
基金Supported by National Key R&D Program of China(2019YFA0405400)。
文摘In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.
基金supported by the National Natural Science Foundation of China(Grant Nos.31771887,31671761 and 32001491)supported by the National Natural Science Foundation of China(Grant Nos.31771887,31671761 and 32001491).
文摘A gsnl4 mutant characterized by small grain size,narrow leaf and low seed-setting rate was obtained by ethyl methane sulfonate(EMS)mutagenesis of a japonica rice variety Wuyunjing 21.Genetic analysis showed that gsnl4 is a loss-of-function mutant.A single-base mutation in gsnl4 resulted in the substitution of Ser to Asn in the Piwi domain of OsAGOlb protein.CRISPR/Cas9-mediated editing of OsAGOlb yielded a mutant phenotypically resembling gsnl4.Furthermore,miRNA-Seq analysis showed that the transcript expression levels of miRNAs in the signal transduction pathways related to pollen development,leaf morphology and honnone activation were significantly different between the gsnl4 mutant and the wild type(WT)plants.Several miRNAs were downregulated,and their target genes were upregulated in gsnl4 mutants.The auxin content in the root tips of the gsnl4 mutant decreased,and the expression of most auxin-related genes was altered.In summary,GSNL4 not only regulates organ development by controlling cell division and expansion,but also plays an important role in regulating auxin transport in rice.
文摘The HIAF High Intensity heavy Ion Accelerator Facility is under construction in Huizhou City,Guangdong,China^([1]).To fulfill the demand of frontier research in nuclear physics,astrophysics,atomic physics,and high energy density physics,HIAF aims to provide the ambitious beam intensity of pulsed heavy ions with the energy range of several hundred MeV/u up to GeV.
基金support from The National Key R&D Program of China(Grant No.2019YFA0405400)China National Funds for Distinguished Young Scientists(No.11825505)Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06G373).
文摘Purpose To protect accelerator devices from being damaged by high-power beam,a new beam dump system is under design for HIAF-BRing.Method Based on the optical characteristics,unwanted particles are safely deflected to a specific internal absorber through a local bump orbit generated by active-discharging magnets,which is achieved by paralleling a bleeder resistor of 600 m�to two of dipole magnet power supplies.Results Taking alignment and multipolefield errors into account,discarded beam can be dumped within 5 ms with an efficiency of more than 99.8%at any operation stage.Conclusion The proposed beam dump solution satisfies the machine protection requirements for BRing and can provide a new idea for similar facilities.
