This paper deals with the problem of the instability regions of a free-free flexible jointed bipartite beam under the follower and transversal forces as a realistic simulation of a two-stage aerospace structure. The a...This paper deals with the problem of the instability regions of a free-free flexible jointed bipartite beam under the follower and transversal forces as a realistic simulation of a two-stage aerospace structure. The aim of this study is to analyze the effects of the characteristics of a flexible joint on the beam instability to use maximum bearable propulsion force. A parametric study is conducted to investigate the effects of the stiffness and the location of the joint on the critical follower force by the Ritz method and the Newmark method, then to research the vibrational properties of the structure. It has been shown that the nature of instability is quite unpredictable and dependent on the stiffness and the location of the joint. The increase of the follower force or the transversal force will increase the vibration of the model and consequently cause a destructive phenomenon in the control system of the aerospace structure. Furthermore, this paper introduces a new concept of the parametric approach to analyze the characteristics effects of a flexible two-stage aerospace structure joint design.展开更多
For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV....For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV. When the proton beam traverses in the RF cavity, the excited parasitic modes, like high order modes （HOMs） and same order modes （SOMs）, may drive the beam to become unstable and increase the cryogenic load, thus putting a limitation on the normal operation of the accelerator. In this paper, by using a numerical code SMD based on the ROOT environment, the effects of longitudinal parasitic modes on the beam dynamics for the ADS driving linac in China have been investigated systematically, while parasitic modes which increase cryogenic loss have not been included in this paper. Some conclusions concerning the beam energy ranging from 180 MeV to 1.5 GeV have been obtained.展开更多
The ADS （Accelerator Driven subcritical System） driver linac in China is designed to run in CW （Continuous Wave） mode with 10 mA designed beam current. In this scenario, the beam-induced parasitic modes in the ADS...The ADS （Accelerator Driven subcritical System） driver linac in China is designed to run in CW （Continuous Wave） mode with 10 mA designed beam current. In this scenario, the beam-induced parasitic modes in the ADS driver linac may make the beam unstable or deteriorate the beam performance. To evaluate the parasitic mode effect on the beam dynamics systematically, simulation studies using the ROOT-based numerical code SMD have been conducted. The longitudinal beam instability induced by the HOMs （High Order Modes） and SOMs （Same Order Modes） has little effect on the longitudinal beam performance for the current ADS driver linac design based on the 10 MeV/325 MHz injector I from previous studies. Here the transverse parasitic mode （i.e., dipole HOM） effect on the transverse beam performance at the ADS driver linac exit is investigated. To more reasonably quantify the dipole mode effect, the multi-bunch effective emittance is introduced in this paper.展开更多
In the conventional design of RF linacs, the bunched beams are not in thermal equilibrium. The space charge forces couple the particle motions between the transverse and the longitudinal directions. Furthermore it wil...In the conventional design of RF linacs, the bunched beams are not in thermal equilibrium. The space charge forces couple the particle motions between the transverse and the longitudinal directions. Furthermore it will cause the equipartitioning process which leads to emittance growth and halo formation. In the design of the China Spallation Neutron Source （CSNS） linac, three cases are investigated using the Hofmann stability charts. In this paper, we present the equipartitioning beam study of the CSNS Alvarez DTL linac.展开更多
文摘This paper deals with the problem of the instability regions of a free-free flexible jointed bipartite beam under the follower and transversal forces as a realistic simulation of a two-stage aerospace structure. The aim of this study is to analyze the effects of the characteristics of a flexible joint on the beam instability to use maximum bearable propulsion force. A parametric study is conducted to investigate the effects of the stiffness and the location of the joint on the critical follower force by the Ritz method and the Newmark method, then to research the vibrational properties of the structure. It has been shown that the nature of instability is quite unpredictable and dependent on the stiffness and the location of the joint. The increase of the follower force or the transversal force will increase the vibration of the model and consequently cause a destructive phenomenon in the control system of the aerospace structure. Furthermore, this paper introduces a new concept of the parametric approach to analyze the characteristics effects of a flexible two-stage aerospace structure joint design.
文摘For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV. When the proton beam traverses in the RF cavity, the excited parasitic modes, like high order modes （HOMs） and same order modes （SOMs）, may drive the beam to become unstable and increase the cryogenic load, thus putting a limitation on the normal operation of the accelerator. In this paper, by using a numerical code SMD based on the ROOT environment, the effects of longitudinal parasitic modes on the beam dynamics for the ADS driving linac in China have been investigated systematically, while parasitic modes which increase cryogenic loss have not been included in this paper. Some conclusions concerning the beam energy ranging from 180 MeV to 1.5 GeV have been obtained.
文摘The ADS （Accelerator Driven subcritical System） driver linac in China is designed to run in CW （Continuous Wave） mode with 10 mA designed beam current. In this scenario, the beam-induced parasitic modes in the ADS driver linac may make the beam unstable or deteriorate the beam performance. To evaluate the parasitic mode effect on the beam dynamics systematically, simulation studies using the ROOT-based numerical code SMD have been conducted. The longitudinal beam instability induced by the HOMs （High Order Modes） and SOMs （Same Order Modes） has little effect on the longitudinal beam performance for the current ADS driver linac design based on the 10 MeV/325 MHz injector I from previous studies. Here the transverse parasitic mode （i.e., dipole HOM） effect on the transverse beam performance at the ADS driver linac exit is investigated. To more reasonably quantify the dipole mode effect, the multi-bunch effective emittance is introduced in this paper.
文摘In the conventional design of RF linacs, the bunched beams are not in thermal equilibrium. The space charge forces couple the particle motions between the transverse and the longitudinal directions. Furthermore it will cause the equipartitioning process which leads to emittance growth and halo formation. In the design of the China Spallation Neutron Source （CSNS） linac, three cases are investigated using the Hofmann stability charts. In this paper, we present the equipartitioning beam study of the CSNS Alvarez DTL linac.
