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
In order to meet the requirements of the Circular Electron Positron Collider(CEPC),a 650-MHz 2-cell superconducting cavity was proposed and designed.In this study,we show the progress in the cavity design for the CEPC...In order to meet the requirements of the Circular Electron Positron Collider(CEPC),a 650-MHz 2-cell superconducting cavity was proposed and designed.In this study,we show the progress in the cavity design for the CEPC.The radio frequency and mechanical designs are ready for the first design version,called CEPC-V1.A cryomodule,which consists of two 650-MHz 2-cell cavities,was scheduled the last year.Therefore,prototypes of the 2-cell cavity based on this design were fabricated and tested the following year.The vertical test results show that multipacting(MP)exists from 10 to 19 MV/m.This will increase the operational risk of the CEPC,while the continuous-wave operation for the 650-MHz cavity is 19.7 MV/m.Two trapped modes were also found,which exist because of the identical half-cell design.Therefore,a few improvements regarding MP and more efficient extraction of higher-order mode power are discussed.A new type of cavity design,called CEPC-V2,is also discussed in this paper.展开更多
Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor...Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.展开更多
The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conduct...The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.展开更多
The nitrogen doping/infusion of 650 MHz cavities for the circular electron positron collider(CEPC)is investigated in this study.Two 650 MHz 1-cell cavities are first treated via buffered chemical polishing(BCP),follow...The nitrogen doping/infusion of 650 MHz cavities for the circular electron positron collider(CEPC)is investigated in this study.Two 650 MHz 1-cell cavities are first treated via buffered chemical polishing(BCP),followed by nitrogen doping.A"2/6"condition is adopted,similar to that for 1.3 GHz cavities of Linear Coherent Light Source II.The quality factor of both cavities improved to 7×10^(10)in low fields,i.e.,higher than that obtained from the baseline test.One 650 MHz two-cell cavity is nitrogen infused at 165℃for 48 h with a BCP surface base.The intrinsic quality factor(Q0)reached6×10^(10)at 22 MV/m in the vertical test,and the maximum gradient is 25 MV/m,which exceeds the specification of the CEPC(4×10^(10)at 22 MV/m).展开更多
Background A reliable and repeatable post-processing technology of improving the performance of 1.3 GHz superconducting radio frequency(SRF)cavities is one of the critical technologies for the ILC and XFEL and ERL pro...Background A reliable and repeatable post-processing technology of improving the performance of 1.3 GHz superconducting radio frequency(SRF)cavities is one of the critical technologies for the ILC and XFEL and ERL projects.Methods Three 1.3 GHz single-cell cavities were fabricated and received a baking in temperature 330℃,while the interior of the cavity stayed in ultra-high vacuum(UHV).The cavities were also vertical-tested after electropolishing(EP)with 120℃48-h baking and with nitrogen doping separately for a comparison.Results The Q_(0) of 1.3 GHz single cavity after medium-temperature baking can be 2-3×10^(10) in the accelerating gradient range of 2-35 MV/m in the 2 K vertical test in IHEP.Meanwhile,the outer surface oxidation of niobium cavity caused by baking will decrease the performance of the SRF cavity.Conclusions Medium-temperature(250-400℃)baking on the 1.3 GHz single-cell cavity will improve its Q_(0) in 2 K vertical test compared with EP followed by 120℃48-h baking baseline and reach a similar level of nitrogen doping,and the quench field will lower to a typical range of 20-30 MV/m.Meanwhile,the cavity performance is sensitive to the baking time and temperature,which indicates that a tremendous improvement can be made on the current treatment.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 National Key Programme for S&T Research and Development(No.2016YFA0400400)
文摘In order to meet the requirements of the Circular Electron Positron Collider(CEPC),a 650-MHz 2-cell superconducting cavity was proposed and designed.In this study,we show the progress in the cavity design for the CEPC.The radio frequency and mechanical designs are ready for the first design version,called CEPC-V1.A cryomodule,which consists of two 650-MHz 2-cell cavities,was scheduled the last year.Therefore,prototypes of the 2-cell cavity based on this design were fabricated and tested the following year.The vertical test results show that multipacting(MP)exists from 10 to 19 MV/m.This will increase the operational risk of the CEPC,while the continuous-wave operation for the 650-MHz cavity is 19.7 MV/m.Two trapped modes were also found,which exist because of the identical half-cell design.Therefore,a few improvements regarding MP and more efficient extraction of higher-order mode power are discussed.A new type of cavity design,called CEPC-V2,is also discussed in this paper.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB25000000)the National Natural Science Foundation of China(No.12075270)the Platform of Advanced Photon Source Technology R&D。
文摘Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.
基金This work was supported by Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA03030201)the Key Laboratory of Particle Acceleration Physics and Technology Autonomous Foundation of CAS China(No.JSQ2017ZZ01).
文摘The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.
基金supported by the National Key Program for S&T Research and Development(No.2016YFA0400400)the Platform of Advanced Photon Source Technology R&D,National Natural Science Foundation of China(No.11505197).
文摘The nitrogen doping/infusion of 650 MHz cavities for the circular electron positron collider(CEPC)is investigated in this study.Two 650 MHz 1-cell cavities are first treated via buffered chemical polishing(BCP),followed by nitrogen doping.A"2/6"condition is adopted,similar to that for 1.3 GHz cavities of Linear Coherent Light Source II.The quality factor of both cavities improved to 7×10^(10)in low fields,i.e.,higher than that obtained from the baseline test.One 650 MHz two-cell cavity is nitrogen infused at 165℃for 48 h with a BCP surface base.The intrinsic quality factor(Q0)reached6×10^(10)at 22 MV/m in the vertical test,and the maximum gradient is 25 MV/m,which exceeds the specification of the CEPC(4×10^(10)at 22 MV/m).
基金supported by the Platform of Advanced Photon Source Technology R&D
文摘Background A reliable and repeatable post-processing technology of improving the performance of 1.3 GHz superconducting radio frequency(SRF)cavities is one of the critical technologies for the ILC and XFEL and ERL projects.Methods Three 1.3 GHz single-cell cavities were fabricated and received a baking in temperature 330℃,while the interior of the cavity stayed in ultra-high vacuum(UHV).The cavities were also vertical-tested after electropolishing(EP)with 120℃48-h baking and with nitrogen doping separately for a comparison.Results The Q_(0) of 1.3 GHz single cavity after medium-temperature baking can be 2-3×10^(10) in the accelerating gradient range of 2-35 MV/m in the 2 K vertical test in IHEP.Meanwhile,the outer surface oxidation of niobium cavity caused by baking will decrease the performance of the SRF cavity.Conclusions Medium-temperature(250-400℃)baking on the 1.3 GHz single-cell cavity will improve its Q_(0) in 2 K vertical test compared with EP followed by 120℃48-h baking baseline and reach a similar level of nitrogen doping,and the quench field will lower to a typical range of 20-30 MV/m.Meanwhile,the cavity performance is sensitive to the baking time and temperature,which indicates that a tremendous improvement can be made on the current treatment.
