The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSN...The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSNS-II)commenced in 2024.The CSNS-II linac design primarily involves the addition of a radio-frequency ion source and a section of a superconducting linear accelerator composed of two types of superconducting cavities,namely double-spoke and six-cell elliptical cavities,after the drift tube linac(DTL).The development of the double-spoke superconducting cavity began in early 2021,and by January 2023,the welding,post-processing,and vertical tests of two 324 MHz double-spoke cavity prototypes were completed,with vertical test gradients of 11.6 and 15 MV/m,and Q_(0)≥3×10^(10)@E_(acc)≤10 MV/m.The R&D of the cryomodule began in January 2022.In October 2023,the clean assembly of the double-spoke cavity string and cold mass installation of the cryomodule commenced,with the installation of the cryomodule and valve box completing in two months.In January 2024,a horizontal test of the cryomodule was completed,making it the first double-spoke cavity cryomodule in China.The test results showed that the maximum gradients of the two superconducting cavities at a pulse width of 4 ms and repetition frequency of 25 Hz were 12.8 and 15.2 MV/m,respectively.This article provides a detailed introduction to the double-spoke superconducting cavity,tuner,coupler,and cryomodule,elaborates on the clean assembly of the cavity string and cold mass installation of the cryomodule,and provides a detailed analysis of the horizontal test results.展开更多
The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,E...The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.展开更多
The horizontal test for the BEPC 500 MHz spare cavity has been completed at IHEP. The maximum voltage of the cavity reached 2.17 MV, while Q 0 was 5.78 × 10^8 . The process and results of the high power horizonta...The horizontal test for the BEPC 500 MHz spare cavity has been completed at IHEP. The maximum voltage of the cavity reached 2.17 MV, while Q 0 was 5.78 × 10^8 . The process and results of the high power horizontal test are presented and discussed in this paper.展开更多
The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input...The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input power up to approximately 7 kW.The first batch of 20 sets of 1.3 GHz coupler prototypes was fabricated from three domestic manufacturers for the SHINE project.To better characterize the radio frequency conditioning phenomena for validating the performance of power couplers,a room temperature test stand was designed,constructed,and commissioned for the SHINE 1.3 GHz power couplers.In addition,a horizontal test cryostat was built to test the 1.3 GHz superconducting cavities,fundamental power couplers,tuners,and other components as a set.The results of these tests indicate that the 1.3 GHz couplers are capable of handling up to 14 kW continuous waves.Herein,the main aspects of the radio frequency design and construction of the test stand,along with the test results of the high-power conditioning of the 1.3 GHz couplers,are described.展开更多
Title:Seismic fragility of unreinforced masonry buildings with bonded scrap tire rubber isolators under far-field and near-field earthquakes Authors:WANG Mingyang;GAO Wenjun;LU Xilin;SHI Weixing A bstract:To improve t...Title:Seismic fragility of unreinforced masonry buildings with bonded scrap tire rubber isolators under far-field and near-field earthquakes Authors:WANG Mingyang;GAO Wenjun;LU Xilin;SHI Weixing A bstract:To improve the seismic performance of unreinforced masonry(URM)buildings in the Himalayan regions,including Western China,India,Nepal,and Pakistan,a low-cost bonded scrap tire rubber isolator(BSTRI)is proposed,and a series of vertical compression and horizontal shear tests are conducted.Incremental dynamic analyses are conducted for five types of BSTRI-supported URM buildings subjected to 22 far-field and 28 near-field earthquake ground motions.The resulting fragility curves and probability of damage curves are presented and utilized to evaluate the damage states of these buildings.The results show that in the base-isolated(BI)URM buildings under seismic ground motion at a peak ground acceleration(PGA)of 1.102 g,the probability of exceeding the collapse prevention threshold is less than 25%under far-field earthquake ground motions and 31%under near-field earthquake ground motions.Furthermore,the maximum average vulnerability index for the BI-URM buildings,which are designed to withstand rare earthquakes with 9°(PGA=0.632 g),is 40.87%for far-field earthquake ground motions and 41.83%for near-field earthquake ground motions.Therefore,the adoption of BSTRIs can significantly reduce the collapse probability of URM buildings.展开更多
The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered...The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.展开更多
文摘The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSNS-II)commenced in 2024.The CSNS-II linac design primarily involves the addition of a radio-frequency ion source and a section of a superconducting linear accelerator composed of two types of superconducting cavities,namely double-spoke and six-cell elliptical cavities,after the drift tube linac(DTL).The development of the double-spoke superconducting cavity began in early 2021,and by January 2023,the welding,post-processing,and vertical tests of two 324 MHz double-spoke cavity prototypes were completed,with vertical test gradients of 11.6 and 15 MV/m,and Q_(0)≥3×10^(10)@E_(acc)≤10 MV/m.The R&D of the cryomodule began in January 2022.In October 2023,the clean assembly of the double-spoke cavity string and cold mass installation of the cryomodule commenced,with the installation of the cryomodule and valve box completing in two months.In January 2024,a horizontal test of the cryomodule was completed,making it the first double-spoke cavity cryomodule in China.The test results showed that the maximum gradients of the two superconducting cavities at a pulse width of 4 ms and repetition frequency of 25 Hz were 12.8 and 15.2 MV/m,respectively.This article provides a detailed introduction to the double-spoke superconducting cavity,tuner,coupler,and cryomodule,elaborates on the clean assembly of the cavity string and cold mass installation of the cryomodule,and provides a detailed analysis of the horizontal test results.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23090402)the National Natural Science Foundation of China(Nos.41790442,41825018)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)。
文摘The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.
基金Supported by Facility Repair Project of CAS (K71G710Y21)
文摘The horizontal test for the BEPC 500 MHz spare cavity has been completed at IHEP. The maximum voltage of the cavity reached 2.17 MV, while Q 0 was 5.78 × 10^8 . The process and results of the high power horizontal test are presented and discussed in this paper.
基金supported by Shanghai Municipal Science and Technology Major Project(No.2017SHZDZX02)。
文摘The Shanghai High Repetition Rate XFEL and Extreme Light Facility(SHINE)project will use 6001.3 GHz fundamental power couplers,which are modified based on TTF-Ⅲ power couplers,for continuous-wave operation with input power up to approximately 7 kW.The first batch of 20 sets of 1.3 GHz coupler prototypes was fabricated from three domestic manufacturers for the SHINE project.To better characterize the radio frequency conditioning phenomena for validating the performance of power couplers,a room temperature test stand was designed,constructed,and commissioned for the SHINE 1.3 GHz power couplers.In addition,a horizontal test cryostat was built to test the 1.3 GHz superconducting cavities,fundamental power couplers,tuners,and other components as a set.The results of these tests indicate that the 1.3 GHz couplers are capable of handling up to 14 kW continuous waves.Herein,the main aspects of the radio frequency design and construction of the test stand,along with the test results of the high-power conditioning of the 1.3 GHz couplers,are described.
文摘Title:Seismic fragility of unreinforced masonry buildings with bonded scrap tire rubber isolators under far-field and near-field earthquakes Authors:WANG Mingyang;GAO Wenjun;LU Xilin;SHI Weixing A bstract:To improve the seismic performance of unreinforced masonry(URM)buildings in the Himalayan regions,including Western China,India,Nepal,and Pakistan,a low-cost bonded scrap tire rubber isolator(BSTRI)is proposed,and a series of vertical compression and horizontal shear tests are conducted.Incremental dynamic analyses are conducted for five types of BSTRI-supported URM buildings subjected to 22 far-field and 28 near-field earthquake ground motions.The resulting fragility curves and probability of damage curves are presented and utilized to evaluate the damage states of these buildings.The results show that in the base-isolated(BI)URM buildings under seismic ground motion at a peak ground acceleration(PGA)of 1.102 g,the probability of exceeding the collapse prevention threshold is less than 25%under far-field earthquake ground motions and 31%under near-field earthquake ground motions.Furthermore,the maximum average vulnerability index for the BI-URM buildings,which are designed to withstand rare earthquakes with 9°(PGA=0.632 g),is 40.87%for far-field earthquake ground motions and 41.83%for near-field earthquake ground motions.Therefore,the adoption of BSTRIs can significantly reduce the collapse probability of URM buildings.
基金supported by the Key Program of National Natural Science Foundation of China(No.U23A202579)the National Natural Science Foundation of China(No.42277187,42007276,41972297)the Natural Science Foundation of Hebei Province(No.D2021202002)。
文摘The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.
