The stability and reliability of an ion source and its beam availability are extremely significant for any accelerator,especially for those high current long term CW operation ones like ADS. Although the first high qu...The stability and reliability of an ion source and its beam availability are extremely significant for any accelerator,especially for those high current long term CW operation ones like ADS. Although the first high quality 306-hours continuous wave(CW) operating curve at 50 m A@35 ke V has been successfully obtained with a standard compact 2.45 GHz ECR ion source at Peking University(PKU), but the uncertainties that caused beam trips before are unacceptable during an accelerator real operation and should be eliminated. Meanwhile, no permission will be given when the beam power is upgraded from 50 m A@35 ke V to 50 m A@50 ke V. To improve the PKU CW proton source quality, several upgrades were done recently. After those improvements, a new long term CW proton beam experiment at 50 m A@50 ke V was carried out in June 2016. The total running time is 300.5 hours, including near 6 hours ion source preparation and 294 hours non-disturb continuous operation. Within the continuous 13 days operation, no beam-off happened, no spark was observed,no beam drop appeared, no interrupting action was needed, and only a few beam fluctuations caused by the air conditional failure occurred. Beam availability and reliability within the 294 hours is 100%. The root-mean-square(RMS) emittance of this 50 m A@50 ke V CW proton beam is about 0.186 π.mm.mrad. A careful inspection of the ion source was done after this long term operation and no obvious damage was found. The restart experimental results obtained after the ion source inspection prove the high repeatability of PKU PMECRIS. In addition, a 130-m A H+beam was obtained at 50 k V with duty factor of 10%(100 Hz/1 ms) with this source. Details will be presented in this paper.展开更多
In this study, seven pinned double-rectangular tube assembled buckling-restrained brace (DRT-ABRB) specimens were experimentally charaeterised by means of an axial cyclic test. The core member of the specimens was a...In this study, seven pinned double-rectangular tube assembled buckling-restrained brace (DRT-ABRB) specimens were experimentally charaeterised by means of an axial cyclic test. The core member of the specimens was a single flat-plate. Two rectangular tubes were assembled using high strength bolts to form an external restraining member. Each rectangular tube was composed of an external steel channel and a cover plate. A gap or thin rubber filler was set between the core and the external restraining member to form an unbonded layer. The influence of several design parameters on the failure mode and energy dissipation capacity of the ABRB was investigated, including the height of the core wing plate, thickness of the external cover plate, and height of the external channel flange. This experimental study demonstrated that a local pressure-bearing failure at the end of the external member arises when the external cover plate is too thin or if the end construction detail is unreasonable. When the end rotations of the DRT-ABRB were restricted, the hysteretic performance was shown to be superior to that of a pure pinned DRT-ABRB. Finally, all the tested DRT-ABRBs exhibited excellent energy dissipation performance which amply satisfied existing regulation requirements.展开更多
The unobserved J^P= 0^-radial excitation Ds(2^1S0) is anticipated to have mass 2650 Me V(denoted as Ds(2650)). Study of hadronic production is an important way to identify highly excited states. We study hadroni...The unobserved J^P= 0^-radial excitation Ds(2^1S0) is anticipated to have mass 2650 Me V(denoted as Ds(2650)). Study of hadronic production is an important way to identify highly excited states. We study hadronic production of Ds(2650) from higher excited resonances in a3P0 model. Relevant hadronic partial decay widths are found to be very small, which implies it is difficult to observe Ds(2650) in hadronic decays of higher excited resonances. Hadronic decay widths of radially excited Ds(3P) have also been estimated. The total decay widths of four Ds(3P) are large, but the branching ratios in the Ds(2650)η channel are very small, which implies that it seems impossible to observe Ds(2650) in hadronic decays of Ds(3P). The dominant decay channels of the four Ds(3P) have been pointed out, and D1(2420), D1(2430), D*2(2460), D(2550), D(2600),(1-1D2)D(2750) and D3^(2760) are possible to observe in hadronic production from Ds(3P).展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2014CB845502)the National Natural Science Foundation of China(Grant No.11575013)
文摘The stability and reliability of an ion source and its beam availability are extremely significant for any accelerator,especially for those high current long term CW operation ones like ADS. Although the first high quality 306-hours continuous wave(CW) operating curve at 50 m A@35 ke V has been successfully obtained with a standard compact 2.45 GHz ECR ion source at Peking University(PKU), but the uncertainties that caused beam trips before are unacceptable during an accelerator real operation and should be eliminated. Meanwhile, no permission will be given when the beam power is upgraded from 50 m A@35 ke V to 50 m A@50 ke V. To improve the PKU CW proton source quality, several upgrades were done recently. After those improvements, a new long term CW proton beam experiment at 50 m A@50 ke V was carried out in June 2016. The total running time is 300.5 hours, including near 6 hours ion source preparation and 294 hours non-disturb continuous operation. Within the continuous 13 days operation, no beam-off happened, no spark was observed,no beam drop appeared, no interrupting action was needed, and only a few beam fluctuations caused by the air conditional failure occurred. Beam availability and reliability within the 294 hours is 100%. The root-mean-square(RMS) emittance of this 50 m A@50 ke V CW proton beam is about 0.186 π.mm.mrad. A careful inspection of the ion source was done after this long term operation and no obvious damage was found. The restart experimental results obtained after the ion source inspection prove the high repeatability of PKU PMECRIS. In addition, a 130-m A H+beam was obtained at 50 k V with duty factor of 10%(100 Hz/1 ms) with this source. Details will be presented in this paper.
基金Project supported by the National Natural Science Foundation of China(No.51608014)the Beijing Natural Science Foundation(Nos.8174060 and 8131002)the China Postdoctoral Science Foundation(No.2017T100020)
基金supported by the National Key Basic Research and Development Program of China(No.2016YFC0701504)the National Natural Science Foundation of China(No.51608014)+1 种基金the Natural Science Foundation of Beijing,China(No.8174060)the China Postdoctoral Science Foundation(No.2017T100020)
基金Project supported by the National Natural Science Foundation of China (Nos. 51178243 and 51608014), the China Postdoctoral Science Foundation (No. 2015M580030), and the Natural Science Foundation of Beijing, China (No. 8131002)
文摘In this study, seven pinned double-rectangular tube assembled buckling-restrained brace (DRT-ABRB) specimens were experimentally charaeterised by means of an axial cyclic test. The core member of the specimens was a single flat-plate. Two rectangular tubes were assembled using high strength bolts to form an external restraining member. Each rectangular tube was composed of an external steel channel and a cover plate. A gap or thin rubber filler was set between the core and the external restraining member to form an unbonded layer. The influence of several design parameters on the failure mode and energy dissipation capacity of the ABRB was investigated, including the height of the core wing plate, thickness of the external cover plate, and height of the external channel flange. This experimental study demonstrated that a local pressure-bearing failure at the end of the external member arises when the external cover plate is too thin or if the end construction detail is unreasonable. When the end rotations of the DRT-ABRB were restricted, the hysteretic performance was shown to be superior to that of a pure pinned DRT-ABRB. Finally, all the tested DRT-ABRBs exhibited excellent energy dissipation performance which amply satisfied existing regulation requirements.
基金Supported by National Natural Science Foundation of China(11475111)
文摘The unobserved J^P= 0^-radial excitation Ds(2^1S0) is anticipated to have mass 2650 Me V(denoted as Ds(2650)). Study of hadronic production is an important way to identify highly excited states. We study hadronic production of Ds(2650) from higher excited resonances in a3P0 model. Relevant hadronic partial decay widths are found to be very small, which implies it is difficult to observe Ds(2650) in hadronic decays of higher excited resonances. Hadronic decay widths of radially excited Ds(3P) have also been estimated. The total decay widths of four Ds(3P) are large, but the branching ratios in the Ds(2650)η channel are very small, which implies that it seems impossible to observe Ds(2650) in hadronic decays of Ds(3P). The dominant decay channels of the four Ds(3P) have been pointed out, and D1(2420), D1(2430), D*2(2460), D(2550), D(2600),(1-1D2)D(2750) and D3^(2760) are possible to observe in hadronic production from Ds(3P).