When the beam in BEPCII storage ring aborts suddenly, the measured pressure of cold cathode gauges and ion pumps will drop suddenly and decrease to the base pressure gradually. This shows that there is a beam induced ...When the beam in BEPCII storage ring aborts suddenly, the measured pressure of cold cathode gauges and ion pumps will drop suddenly and decrease to the base pressure gradually. This shows that there is a beam induced positive error in the pressure measurement during beam operation. The error is the difference between measured and real pressures. Right after the beam aborts, the error will disappear immediately and the measured pressure will then be equal to real pressure. For one gauge, we can fit a non-linear pressure-time curve with its measured pressure data 20 seconds after a sudden beam abortion. From this negative exponential decay pumping-down curve, real pressure at the time when the beam starts aborting is extrapolated. With the data of several sudden beam abortions we have got the errors of that gauge in different beam currents and found that the error is directly proportional to the beam current, as expected. And a linear data-fitting gives the proportion coefficient of the equation, which we derived to evaluate the real pressure all the time when the beam with varied currents is on.展开更多
The existing linear coupling theory and representation method are introduced briefly. The socalled local and global coupling is discussed in more detail. The vertical orbit distortion excited by a horizontal corrector...The existing linear coupling theory and representation method are introduced briefly. The socalled local and global coupling is discussed in more detail. The vertical orbit distortion excited by a horizontal corrector is represented with the coupling parameters at the corrector and the observation point. The formula is used to measure the coupling in BEPC II. In order to correct the coupling, vertical correctors are used to change the vertical orbit through sextupoles by a least square method. We also introduce and review other frequently used coupling measurement/tuning methods used in our machine.展开更多
Background BEPCⅡis an electron-positron collider with a beam energy of 1.89 GeV and luminosity of 1×10^(33)cm^(-2)s^(-1).Being a complex accelerator,fault diagnostics both in an accurate manner and in time are o...Background BEPCⅡis an electron-positron collider with a beam energy of 1.89 GeV and luminosity of 1×10^(33)cm^(-2)s^(-1).Being a complex accelerator,fault diagnostics both in an accurate manner and in time are often challenging during its operation.Purpose The fault diagnosis research platform is capable of locating and resolving faults on time,thus can largely improve the operation of BEPCⅡby reducing downtime due to machine fault and consequently satisfying the demand for fault diagnosis of a complex system.Methods Making full use of the existing large-scale hardware foundation,abundant data resources and previous experiences,a fault diagnosis research platform was built by applying data mining,machine learning and other related algorithms to carry out specific fault analysis on the entire system.Conclusion The fault diagnosis research platform has been developed with implemented functions of data query,statistics and analysis.Partial fault diagnoses of the three subsystems have been realized.The 4W1 power supply fault has been successfully discovered,and effective solutions have been subsequently provided.展开更多
In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonli...In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations.展开更多
基金supported by the Beijing Electron Positron Collider Upgrade Project Funding Issues
文摘When the beam in BEPCII storage ring aborts suddenly, the measured pressure of cold cathode gauges and ion pumps will drop suddenly and decrease to the base pressure gradually. This shows that there is a beam induced positive error in the pressure measurement during beam operation. The error is the difference between measured and real pressures. Right after the beam aborts, the error will disappear immediately and the measured pressure will then be equal to real pressure. For one gauge, we can fit a non-linear pressure-time curve with its measured pressure data 20 seconds after a sudden beam abortion. From this negative exponential decay pumping-down curve, real pressure at the time when the beam starts aborting is extrapolated. With the data of several sudden beam abortions we have got the errors of that gauge in different beam currents and found that the error is directly proportional to the beam current, as expected. And a linear data-fitting gives the proportion coefficient of the equation, which we derived to evaluate the real pressure all the time when the beam with varied currents is on.
基金Supported by National Natural Science Foundation of China(10805051,10725525)
文摘The existing linear coupling theory and representation method are introduced briefly. The socalled local and global coupling is discussed in more detail. The vertical orbit distortion excited by a horizontal corrector is represented with the coupling parameters at the corrector and the observation point. The formula is used to measure the coupling in BEPC II. In order to correct the coupling, vertical correctors are used to change the vertical orbit through sextupoles by a least square method. We also introduce and review other frequently used coupling measurement/tuning methods used in our machine.
基金provided by Youth Innovation Promotion Asso-ciation of the Chinese Academy of Sciences(Grant No.2016011)
文摘Background BEPCⅡis an electron-positron collider with a beam energy of 1.89 GeV and luminosity of 1×10^(33)cm^(-2)s^(-1).Being a complex accelerator,fault diagnostics both in an accurate manner and in time are often challenging during its operation.Purpose The fault diagnosis research platform is capable of locating and resolving faults on time,thus can largely improve the operation of BEPCⅡby reducing downtime due to machine fault and consequently satisfying the demand for fault diagnosis of a complex system.Methods Making full use of the existing large-scale hardware foundation,abundant data resources and previous experiences,a fault diagnosis research platform was built by applying data mining,machine learning and other related algorithms to carry out specific fault analysis on the entire system.Conclusion The fault diagnosis research platform has been developed with implemented functions of data query,statistics and analysis.Partial fault diagnoses of the three subsystems have been realized.The 4W1 power supply fault has been successfully discovered,and effective solutions have been subsequently provided.
文摘In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations.
