We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase...We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase-biased nonlinear amplifying loop mirror to extract part of intracavity laser power as a laser output, and the dependence of output couple ratio of fiber coupler on the mode-locking state is experimentally investigated. The intracavity nonlinear effect is mitigated by lowering the intracavity laser power, which is conducive to avoiding the multi-pulse formation. In the meantime, the loss-imbalance induced by fiber coupler is helpful in improving the self-starting ability. With the proposed laser structure,the multiple pulse formation can be suppressed and high power single pulse train can be obtained. The laser emits three pulse trains which is convenient for some applications. Finally, the output power values of three ports are 5.3 m W, 51.3 m W,and 13.2 m W, respectively. The total single pulse output power is 69.8 m W, which is more than 10 times the result without OC2. The total slope efficiency is about 10.1%. The repetition rate of three pulse trains is 21.17 MHz, and the pulse widths are 2.8 ps, 2.63 ps, and 6.66 ps, respectively.展开更多
A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University. After tuning, a flat field profile with a final π-mode frequency within 3 kHz...A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University. After tuning, a flat field profile with a final π-mode frequency within 3 kHz of target frequency is achieved. The field flatness is measured by a bead-pull method, and the relative electric field is calculated from the frequency shift perturbed by the bead stepping along the axis of the cavity.展开更多
Generally, the Energy Recovery Linac （ERL） needs specially designed high current superconducting RF cavities. In this paper, the threshold current of beam breakup for compact ERL facilities with 9-cell Tesla type ca...Generally, the Energy Recovery Linac （ERL） needs specially designed high current superconducting RF cavities. In this paper, the threshold current of beam breakup for compact ERL facilities with 9-cell Tesla type cavities are investigated. The results show that it is feasible to adopt the 9-cell Tesla cavity for compact ERL test facilities with just a few cavities and beam current around 10 mA.展开更多
The Superconducting Proton Linac （SPL） is the project for a superconducting, high current Haccelerator at CERN. To find dangerous higher order modes （HOMs） in the SPL superconducting cavities, simulation and analy...The Superconducting Proton Linac （SPL） is the project for a superconducting, high current Haccelerator at CERN. To find dangerous higher order modes （HOMs） in the SPL superconducting cavities, simulation and analysis for the cavity model using simulation tools are necessary. The existing TESLA 9-cell cavity geometry data have been used for the initial construction of the models in HFSS. Monopole, dipole and quadrupole modes have been obtained by applying different symmetry boundaries on various cavity models. In calculation, scripting language in HFSS was used to create scripts to automatically calculate the parameters of modes in these cavity models （these scripts are also available in other cavities with different cell numbers and geometric structures）. The results calculated automatically are then compared with the values given in the TESLA paper. The optimized cavity model with the minimum error will be taken as the base for further simulation of the SPL cavities.展开更多
In accelerator RF cavities, there exists not only the fundamental mode which is used to accelerate the beam, but also higher order modes（HOMs）. The higher order modes excited by the beam can seriously affect beam qu...In accelerator RF cavities, there exists not only the fundamental mode which is used to accelerate the beam, but also higher order modes（HOMs）. The higher order modes excited by the beam can seriously affect beam quality, especially for the higher R/Q modes. 1.3 GHz low-loss 9-cell superconducting cavity as a candidate for ILC high gradient cavity, the properties of higher order mode has not been studied carefully. IHEP based on existing low loss cavity, designed and developed a large grain size 1.3 GHz low-loss 9-cell superconducting cavity（IHEP02cavity）. The higher order mode coupler of IHEP02 used TESLA coupler＇s design. As a result of the limitation of the mechanical design, the distance between higher order mode coupler and end cell is larger than TESLA cavity.This paper reports on measured results of higher order modes in the IHEP02 1.3 GHz low-loss 9-cell superconducting cavity. Using different methods, Q e of the dangerous modes passbands have been obtained. The results are compared with TESLA cavity results. R/Q of the first three passbands have also been obtained by simulation and compared with the results of the TESLA cavity.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51905528)the Key Research Project of Bureau of Frontier Sciences and Education+1 种基金Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC008)the National Key Research and Development Project,China(Grant Nos.2019YFB2005600 and 2018YFB2003403)。
文摘We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase-biased nonlinear amplifying loop mirror to extract part of intracavity laser power as a laser output, and the dependence of output couple ratio of fiber coupler on the mode-locking state is experimentally investigated. The intracavity nonlinear effect is mitigated by lowering the intracavity laser power, which is conducive to avoiding the multi-pulse formation. In the meantime, the loss-imbalance induced by fiber coupler is helpful in improving the self-starting ability. With the proposed laser structure,the multiple pulse formation can be suppressed and high power single pulse train can be obtained. The laser emits three pulse trains which is convenient for some applications. Finally, the output power values of three ports are 5.3 m W, 51.3 m W,and 13.2 m W, respectively. The total single pulse output power is 69.8 m W, which is more than 10 times the result without OC2. The total slope efficiency is about 10.1%. The repetition rate of three pulse trains is 21.17 MHz, and the pulse widths are 2.8 ps, 2.63 ps, and 6.66 ps, respectively.
基金Supported by National Basic Research Programme of China (2002CB713600)
文摘A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University. After tuning, a flat field profile with a final π-mode frequency within 3 kHz of target frequency is achieved. The field flatness is measured by a bead-pull method, and the relative electric field is calculated from the frequency shift perturbed by the bead stepping along the axis of the cavity.
基金Supported by Major State Basic Research Development Program of China (2011CB808303, 2011CB808304)
文摘Generally, the Energy Recovery Linac （ERL） needs specially designed high current superconducting RF cavities. In this paper, the threshold current of beam breakup for compact ERL facilities with 9-cell Tesla type cavities are investigated. The results show that it is feasible to adopt the 9-cell Tesla cavity for compact ERL test facilities with just a few cavities and beam current around 10 mA.
文摘The Superconducting Proton Linac （SPL） is the project for a superconducting, high current Haccelerator at CERN. To find dangerous higher order modes （HOMs） in the SPL superconducting cavities, simulation and analysis for the cavity model using simulation tools are necessary. The existing TESLA 9-cell cavity geometry data have been used for the initial construction of the models in HFSS. Monopole, dipole and quadrupole modes have been obtained by applying different symmetry boundaries on various cavity models. In calculation, scripting language in HFSS was used to create scripts to automatically calculate the parameters of modes in these cavity models （these scripts are also available in other cavities with different cell numbers and geometric structures）. The results calculated automatically are then compared with the values given in the TESLA paper. The optimized cavity model with the minimum error will be taken as the base for further simulation of the SPL cavities.
基金Supported by Knowledge Innovation Project of The Chinese Academy of Sciences
文摘In accelerator RF cavities, there exists not only the fundamental mode which is used to accelerate the beam, but also higher order modes（HOMs）. The higher order modes excited by the beam can seriously affect beam quality, especially for the higher R/Q modes. 1.3 GHz low-loss 9-cell superconducting cavity as a candidate for ILC high gradient cavity, the properties of higher order mode has not been studied carefully. IHEP based on existing low loss cavity, designed and developed a large grain size 1.3 GHz low-loss 9-cell superconducting cavity（IHEP02cavity）. The higher order mode coupler of IHEP02 used TESLA coupler＇s design. As a result of the limitation of the mechanical design, the distance between higher order mode coupler and end cell is larger than TESLA cavity.This paper reports on measured results of higher order modes in the IHEP02 1.3 GHz low-loss 9-cell superconducting cavity. Using different methods, Q e of the dangerous modes passbands have been obtained. The results are compared with TESLA cavity results. R/Q of the first three passbands have also been obtained by simulation and compared with the results of the TESLA cavity.
