The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has...The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has an innovative design that leads to the highest sensitivity of any single dish radio telescope in the world. FAST's potential for OH megamaser research is discussed, including the sky density of masers detectable in surveys. The scientific impact expected from FAST maser studies is also discussed.展开更多
SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser ...SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser spots decrease with increasing the distance from the central star. In addition, the similarity between the v = 1,2(J =1–0) spectrums increases with epochs, consistent with the full width at half maximum(FWHM), while the total fluxes increase. The results may be related to the changeable pumping mechanisms.展开更多
To promote the understanding of massive star formation processes, we have studied the 6.6 GHz methanol (CH3OH) masers and their environments-- the dense cores and the outer regions of the molecular cloud. The physics ...To promote the understanding of massive star formation processes, we have studied the 6.6 GHz methanol (CH3OH) masers and their environments-- the dense cores and the outer regions of the molecular cloud. The physics of the CH3OH maser or the thermal emission formation region is studied by fitting the observational data of the 6.6 GHz 51-60 A+ and the 107 GHz 31-40 A+ CH3OH maser emission, using the radiative transfer calculations. The type II characteristics of the 6.6 GHz CH3OH maser are confirmed by the calculation results. A greater intensity of the radiation field leads to an increase in the peak intensity of the maser; however, high densities tend to turn off the maser. The calculation results show that to be a maser the 6.6 GHz CH3OH emission needs a radiation field of 150-300 K and a density not higher than 107cm-3, while the 107 GHz emission requires a radiation field of 210-300 K and a density not higher than 3×106 cm-3. The 6.6 GHz line is maser towards all six studied sources, while the 107 GHz line is maser towards Cep A only. Moreover, the former's intensity is much stronger than the latter. The radiative transfer calculations also indicate that the 6.6 GHz maser emission is so strong that the requirements of its formation (e.g. The radiation field, the density and the kinetic parameters) can only be satisfied at a certain stage of the processes of the massive star formation. Therefore it is often used as one of the most prominent tracers for the massive star formation regions. The calculation results of the simultaneous observations of (1,1) through (4,4) inversion lines of the ammonia (NH3) indicate that both the temperature and the density in the 6.6 GHz CH3OH maser formation regions are higher than that of the NH3 line formation regions. Furthermore, the common fact of |Vlsr(CO)| ＞ |Vlsr(NH3)| ＞ |Vlsr(CH3OH 6.6GHz maser)| in all six sources implies the ongoing developing trends of those gas flows driven by the masers.展开更多
A new method is proposed to enhance the efficiency of free-electron maser （EM）. Aradial electrostatic field is introduced to assist the axial magnetic field to focus a large-orbitclectron beam. A new kind of azimuth...A new method is proposed to enhance the efficiency of free-electron maser （EM）. Aradial electrostatic field is introduced to assist the axial magnetic field to focus a large-orbitclectron beam. A new kind of azimuthal bunching mechanism. caused by the angular-momentum effect, is demonstrated. Nonlinear simulation of the interaction between a rela-tivistic electron beam and TE<sub>5,1,1</sub> mode or TE<sub>10,1,1</sub> mode shows that, as long as the initialparameters are properly chosen, the method is valid.展开更多
The instabilities of gyrotron, gyro-peniotron and cyclotron auto-resonance masers(CARM) and their relationship are analysed in detail. By introducing gyrokinetic variablesin the Vlasov equation, a unified description,...The instabilities of gyrotron, gyro-peniotron and cyclotron auto-resonance masers(CARM) and their relationship are analysed in detail. By introducing gyrokinetic variablesin the Vlasov equation, a unified description, i.e. the gyrokinetics, of these free-electronmasersisgiven.展开更多
This paper reports on SiO 86GHz observations of 33 IRAS evolved stars with H 2O or OH maser, drawn from Priscilla’s “ A catalog of observations for stellar masers ”. SiO maser emission was detected in five sources ...This paper reports on SiO 86GHz observations of 33 IRAS evolved stars with H 2O or OH maser, drawn from Priscilla’s “ A catalog of observations for stellar masers ”. SiO maser emission was detected in five sources all without previously known SiO detections. A tentative SiO emission was detected from the source IRAS18585+0900. The oxygen/carbonrichness of the circumstellar of IRAS18585+0900 is discussed with reference to its IRAS low resolution spectral (LRS) class 41. The low detection rate is discussed.展开更多
As the recent publication by Breen et al. (2013) found, Class II methanol masers are exclusively associated with high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UC...As the recent publication by Breen et al. (2013) found, Class II methanol masers are exclusively associated with high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UC H II regions and 4.5 μm infrared sources, and the center velocities (vLSR) of the Class I methanol and H2O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H2O masers trace the linear extent of the outflow. In our second model, the H2O masers are located in a circumstellar disk. In our third model, the H2O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.展开更多
Based on the theory of the passive hydrogen maser,along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive h...Based on the theory of the passive hydrogen maser,along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated.Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation.The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.展开更多
The transmission probability of an ultracold cascade three-level atom through a micromaser cavity is calculated and analyzed. It is shown that the micromaser cavity can be used as a velocity selector for ultracold thr...The transmission probability of an ultracold cascade three-level atom through a micromaser cavity is calculated and analyzed. It is shown that the micromaser cavity can be used as a velocity selector for ultracold three-level atoms, and the velocity selectivity is better for three-level atoms than for two-level atoms.展开更多
Based on the operating principle and the electric property design of the passive hydrogen maser, the technology and test results of its space adaptability are carried out under the special launch conditions and space ...Based on the operating principle and the electric property design of the passive hydrogen maser, the technology and test results of its space adaptability are carried out under the special launch conditions and space environment. The various perturbations affecting the output frequency of such a standard used for the navigation satellite system are specified, such as magnetic field change, vibration, thermal vacuum and radiation. Through the adaptability technology in the aspects above, the security and reliability of the space passive hydrogen maser sufficiently fulfill the requirements of space operation. At present, the space passive hydrogen maser is working normally on board, indicating that the space adaptability satisfies the design requirement.展开更多
The size reduction of atomic clocks is a long-standing research issue.Many atomic clocks such as passive hydrogen masers(PHMs)and compact rubidium masers(CRMs)use iris-loaded resonance cavities(IRCs)as their microwave...The size reduction of atomic clocks is a long-standing research issue.Many atomic clocks such as passive hydrogen masers(PHMs)and compact rubidium masers(CRMs)use iris-loaded resonance cavities(IRCs)as their microwave cavities because they can dramatically reduce the radical sizes of the atomic clocks.In this paper,the electromagnetic characteristic of the IRC is investigated by a theoretical model based on electromagnetic field theory.The formulas to calculate the resonance frequency,quality factor,and magnetic energy filling factor are presented.The relationship between the IRC structure and its electromagnetic characteristic is clarified.The theoretical calculation results accord well with the electromagnetic software simulations and experimental results.The results in this paper should be helpful in understanding the physical mechanism of the IRC and designing the atomic clocks.展开更多
Based on the principle of electron cyclotron maser(ECM),gyrotrons are among the most promising devices to generate powerful coherent terahertz(THz)radiation and play a vital role in numerous advanced THz applications....Based on the principle of electron cyclotron maser(ECM),gyrotrons are among the most promising devices to generate powerful coherent terahertz(THz)radiation and play a vital role in numerous advanced THz applications.Unfortunately,THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses,and,accordingly,the wave output efficiency was significantly reduced.A scheme to alleviate such a challenging problem is systematically investigated in this paper.The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator,which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation,simultaneously.A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction,and a down-tapered magnetic field is employed to further amplify the forward-wave(FW)component.The results demonstrate that the proportion of ohmic losses is nearly halved,and output efficiency is nearly doubled,which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.展开更多
From relativistic linear Vlasov-Maxwell equations,the expressions of the startingcurrent and frequency deviation of a electrostatic gyromonotron with a field distribution sin k‖zare derived and the numerical calculat...From relativistic linear Vlasov-Maxwell equations,the expressions of the startingcurrent and frequency deviation of a electrostatic gyromonotron with a field distribution sin k‖zare derived and the numerical calculation is carried out.展开更多
基金supported by the China Ministry of Science and Technology under the National Basic Research Program of China (973 program, 2012CB821800)the National Natural Science Foundation of China (Nos. 11473007, 11373038 and 11590782)supported by the Strategic Priority Research Program (No. XDB09000000) from the Chinese Academy of Sciences
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has an innovative design that leads to the highest sensitivity of any single dish radio telescope in the world. FAST's potential for OH megamaser research is discussed, including the sky density of masers detectable in surveys. The scientific impact expected from FAST maser studies is also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1431125 and U1631106)the Science and Technology Innovation Program of Shanxi Province(2019L0876)Yuncheng University(YQ-2019016)。
文摘SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser spots decrease with increasing the distance from the central star. In addition, the similarity between the v = 1,2(J =1–0) spectrums increases with epochs, consistent with the full width at half maximum(FWHM), while the total fluxes increase. The results may be related to the changeable pumping mechanisms.
基金the National Natural Science Foundation of China(Grant Nos.19973017 and 10133020).
文摘To promote the understanding of massive star formation processes, we have studied the 6.6 GHz methanol (CH3OH) masers and their environments-- the dense cores and the outer regions of the molecular cloud. The physics of the CH3OH maser or the thermal emission formation region is studied by fitting the observational data of the 6.6 GHz 51-60 A+ and the 107 GHz 31-40 A+ CH3OH maser emission, using the radiative transfer calculations. The type II characteristics of the 6.6 GHz CH3OH maser are confirmed by the calculation results. A greater intensity of the radiation field leads to an increase in the peak intensity of the maser; however, high densities tend to turn off the maser. The calculation results show that to be a maser the 6.6 GHz CH3OH emission needs a radiation field of 150-300 K and a density not higher than 107cm-3, while the 107 GHz emission requires a radiation field of 210-300 K and a density not higher than 3×106 cm-3. The 6.6 GHz line is maser towards all six studied sources, while the 107 GHz line is maser towards Cep A only. Moreover, the former's intensity is much stronger than the latter. The radiative transfer calculations also indicate that the 6.6 GHz maser emission is so strong that the requirements of its formation (e.g. The radiation field, the density and the kinetic parameters) can only be satisfied at a certain stage of the processes of the massive star formation. Therefore it is often used as one of the most prominent tracers for the massive star formation regions. The calculation results of the simultaneous observations of (1,1) through (4,4) inversion lines of the ammonia (NH3) indicate that both the temperature and the density in the 6.6 GHz CH3OH maser formation regions are higher than that of the NH3 line formation regions. Furthermore, the common fact of |Vlsr(CO)| ＞ |Vlsr(NH3)| ＞ |Vlsr(CH3OH 6.6GHz maser)| in all six sources implies the ongoing developing trends of those gas flows driven by the masers.
文摘A new method is proposed to enhance the efficiency of free-electron maser （EM）. Aradial electrostatic field is introduced to assist the axial magnetic field to focus a large-orbitclectron beam. A new kind of azimuthal bunching mechanism. caused by the angular-momentum effect, is demonstrated. Nonlinear simulation of the interaction between a rela-tivistic electron beam and TE<sub>5,1,1</sub> mode or TE<sub>10,1,1</sub> mode shows that, as long as the initialparameters are properly chosen, the method is valid.
文摘The instabilities of gyrotron, gyro-peniotron and cyclotron auto-resonance masers(CARM) and their relationship are analysed in detail. By introducing gyrokinetic variablesin the Vlasov equation, a unified description, i.e. the gyrokinetics, of these free-electronmasersisgiven.
文摘This paper reports on SiO 86GHz observations of 33 IRAS evolved stars with H 2O or OH maser, drawn from Priscilla’s “ A catalog of observations for stellar masers ”. SiO maser emission was detected in five sources all without previously known SiO detections. A tentative SiO emission was detected from the source IRAS18585+0900. The oxygen/carbonrichness of the circumstellar of IRAS18585+0900 is discussed with reference to its IRAS low resolution spectral (LRS) class 41. The low detection rate is discussed.
文摘As the recent publication by Breen et al. (2013) found, Class II methanol masers are exclusively associated with high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UC H II regions and 4.5 μm infrared sources, and the center velocities (vLSR) of the Class I methanol and H2O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H2O masers trace the linear extent of the outflow. In our second model, the H2O masers are located in a circumstellar disk. In our third model, the H2O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.
基金supported by the Next Generation of Beidou Navigation Satellite(GFZX0301020104)
文摘Based on the theory of the passive hydrogen maser,along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated.Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation.The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.
基金the Senior Visiting Scholor Project of Chinese Academy of Sciences。
文摘The transmission probability of an ultracold cascade three-level atom through a micromaser cavity is calculated and analyzed. It is shown that the micromaser cavity can be used as a velocity selector for ultracold three-level atoms, and the velocity selectivity is better for three-level atoms than for two-level atoms.
基金supported by the Next Generation of Beidou Navigation Satellite(the Space Passive Hydrogen Maser Technology,GFZX0301020104)
文摘Based on the operating principle and the electric property design of the passive hydrogen maser, the technology and test results of its space adaptability are carried out under the special launch conditions and space environment. The various perturbations affecting the output frequency of such a standard used for the navigation satellite system are specified, such as magnetic field change, vibration, thermal vacuum and radiation. Through the adaptability technology in the aspects above, the security and reliability of the space passive hydrogen maser sufficiently fulfill the requirements of space operation. At present, the space passive hydrogen maser is working normally on board, indicating that the space adaptability satisfies the design requirement.
基金Project supported by the National Natural Science Foundation of China(Grant No.61371052).
文摘The size reduction of atomic clocks is a long-standing research issue.Many atomic clocks such as passive hydrogen masers(PHMs)and compact rubidium masers(CRMs)use iris-loaded resonance cavities(IRCs)as their microwave cavities because they can dramatically reduce the radical sizes of the atomic clocks.In this paper,the electromagnetic characteristic of the IRC is investigated by a theoretical model based on electromagnetic field theory.The formulas to calculate the resonance frequency,quality factor,and magnetic energy filling factor are presented.The relationship between the IRC structure and its electromagnetic characteristic is clarified.The theoretical calculation results accord well with the electromagnetic software simulations and experimental results.The results in this paper should be helpful in understanding the physical mechanism of the IRC and designing the atomic clocks.
基金supported in part by Beijing Science Foundation for Distinguished Young Scholars(Grant No.JQ21011)the National Natural Science Foundation of China(Grant Nos.U1830201 and 61531002)Newton Advanced Fellowship from Royal Society in the United Kingdom(Grant No.NAF/R1/180121)
文摘Based on the principle of electron cyclotron maser(ECM),gyrotrons are among the most promising devices to generate powerful coherent terahertz(THz)radiation and play a vital role in numerous advanced THz applications.Unfortunately,THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses,and,accordingly,the wave output efficiency was significantly reduced.A scheme to alleviate such a challenging problem is systematically investigated in this paper.The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator,which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation,simultaneously.A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction,and a down-tapered magnetic field is employed to further amplify the forward-wave(FW)component.The results demonstrate that the proportion of ohmic losses is nearly halved,and output efficiency is nearly doubled,which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.
文摘From relativistic linear Vlasov-Maxwell equations,the expressions of the startingcurrent and frequency deviation of a electrostatic gyromonotron with a field distribution sin k‖zare derived and the numerical calculation is carried out.
