The electron cloud accumulated in the vicinity of positron beam generates longitudinal electric field during the passage of bunch. The longitudinal interaction between bunch and electron cloud can lead to the distorti...The electron cloud accumulated in the vicinity of positron beam generates longitudinal electric field during the passage of bunch. The longitudinal interaction between bunch and electron cloud can lead to the distortion of the bunch shape. We use a simple analytic formula to calculate the longitudinal electric field due to electron cloud. Based on the longitudinal wake field, the macro-particle tracking method is used to simulate the variation of bunch longitudinal profile in different electron cloud densities and the simulation also shows that the synchrotron oscillation tune is slightly shifted by the wake field. By comparing the simulation results and the analytical estimation from potential distortion theory, the longitudinal wake field from electron cloud can be seen as a potential well effect.展开更多
The robust conjugate direction search （RCDS） method has high tolerance to noise in beam experiments. It has been demonstrated that this method can be used to optimize the machine performance of a light source online...The robust conjugate direction search （RCDS） method has high tolerance to noise in beam experiments. It has been demonstrated that this method can be used to optimize the machine performance of a light source online. In our study, taking BEPCII as an example, the feasibility of online tuning of the luminosity in a circular collider is explored, through numerical simulation and preliminary online experiments. It is shown that the luminosity that is artificially decreased by a deviation of beam orbital offset from optimal trajectory can be recovered with this method.展开更多
During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one t...During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for about 4 months, and studied beam dynamics as well. In this paper, some beam dynamics studies on the storage rings and their preliminary results are given.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
基金Supported by the National Natural Science Foundation of China under Grant Nos 10605032 and 10705033.
文摘The electron cloud accumulated in the vicinity of positron beam generates longitudinal electric field during the passage of bunch. The longitudinal interaction between bunch and electron cloud can lead to the distortion of the bunch shape. We use a simple analytic formula to calculate the longitudinal electric field due to electron cloud. Based on the longitudinal wake field, the macro-particle tracking method is used to simulate the variation of bunch longitudinal profile in different electron cloud densities and the simulation also shows that the synchrotron oscillation tune is slightly shifted by the wake field. By comparing the simulation results and the analytical estimation from potential distortion theory, the longitudinal wake field from electron cloud can be seen as a potential well effect.
基金Supported by National Natural Science Foundation of China(11475202,11405187)Youth Innovation Promotion Association of Chinese Academy of Sciences(2015009)
文摘The robust conjugate direction search （RCDS） method has high tolerance to noise in beam experiments. It has been demonstrated that this method can be used to optimize the machine performance of a light source online. In our study, taking BEPCII as an example, the feasibility of online tuning of the luminosity in a circular collider is explored, through numerical simulation and preliminary online experiments. It is shown that the luminosity that is artificially decreased by a deviation of beam orbital offset from optimal trajectory can be recovered with this method.
基金Supported by National Natural Sciences Foundation of China (10725525)
文摘During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for about 4 months, and studied beam dynamics as well. In this paper, some beam dynamics studies on the storage rings and their preliminary results are given.
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.
