Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076205
D. Wagner, M. Thumm, A. Arnold
To verify the performance of broadband quasioptical mode converters of step-tunable gyrotrons in cold-test experiments, several high order cavity modes at different frequencies have to be excited at low power levels. In order to avoid the huge effort of building a mode generator for each single mode, a broadband quasioptical method was chosen. Here, a Gaussian beam is focused onto a mode specific caustic in a coaxial cavity through a translucent cavity wall. The mode generator can be tuned to different resonances by eventually exchanging the inner conductor of the cavity and by slightly adjusting the position of its quasi-optical components.
{"title":"Mode generator for the cold test of step-tunable gyrotrons","authors":"D. Wagner, M. Thumm, A. Arnold","doi":"10.1109/ICIMW.2002.1076205","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076205","url":null,"abstract":"To verify the performance of broadband quasioptical mode converters of step-tunable gyrotrons in cold-test experiments, several high order cavity modes at different frequencies have to be excited at low power levels. In order to avoid the huge effort of building a mode generator for each single mode, a broadband quasioptical method was chosen. Here, a Gaussian beam is focused onto a mode specific caustic in a coaxial cavity through a translucent cavity wall. The mode generator can be tuned to different resonances by eventually exchanging the inner conductor of the cavity and by slightly adjusting the position of its quasi-optical components.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85316543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076140
G.S. Wang, Z. Hu, Z.M. Huang, X. Wang, T. Lin, J. Chen, X. Meng, J. Chu
The infrared optical constants of lanthanum strontium cobalt oxide (LSCO) thin films are obtained by infrared spectroscopic ellipsometry in the wavelength range of 2.5/spl sim/12.5 /spl mu/m. The absorption coefficient is greater than 10000 cm/sup -1/. The infrared reflection and transmittance measurements showed the LSCO thin films with a thickness of 300 nm absorb significant infrared light. La/sub 0.5/Sr/sub 0.5/CoO/sub 3/ can absorb much more infrared light than La/sub 0.7/Sr/sub 0.3/CoO/sub 3/ with the same thickness. The LSCO thin films are suitable for infrared sensor applications as electrode and blacking layer.
{"title":"Infrared optical properties of lanthanum strontium cobalt thin films","authors":"G.S. Wang, Z. Hu, Z.M. Huang, X. Wang, T. Lin, J. Chen, X. Meng, J. Chu","doi":"10.1109/ICIMW.2002.1076140","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076140","url":null,"abstract":"The infrared optical constants of lanthanum strontium cobalt oxide (LSCO) thin films are obtained by infrared spectroscopic ellipsometry in the wavelength range of 2.5/spl sim/12.5 /spl mu/m. The absorption coefficient is greater than 10000 cm/sup -1/. The infrared reflection and transmittance measurements showed the LSCO thin films with a thickness of 300 nm absorb significant infrared light. La/sub 0.5/Sr/sub 0.5/CoO/sub 3/ can absorb much more infrared light than La/sub 0.7/Sr/sub 0.3/CoO/sub 3/ with the same thickness. The LSCO thin films are suitable for infrared sensor applications as electrode and blacking layer.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76842726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076051
M. Motokawa, M. Yoshida, K. Koyama
The cyclotron resonance is the best way to determine the effective masses of conductors and it is interesting to compare them with other effective masses determined by the de Haas oscillations. According to Kohn's theorem, they are not necessarily coincident with each other because an electron-electron correlation in the strongly correlated electron systems contributes to only the case of the de Haas oscillations. This argument has been studied in the case of organic conductors. On the other hand, it has been difficult to observe the cyclotron resonance absorption in rare-earth semimetals due to necessity of high frequency equipment, high magnetic field, very low temperature and high quality specimen. We have succeeded in observing cyclotron resonance in some rare-earth monopnictide compounds RX (R=rare earth atom, X=pnictgen atom) with NaCl type crystal structure and discussed the relationship between two kinds of masses of these materials. As reference materials, nonmagnetic LaSb and PrSb were also studied. In these cases, we have found new nonlinear resonance lines in addition to the normal cyclotron resonance whose resonance frequencies are linear with respect to magnetic field intensity. We ascribe this effect to the Doppler shift caused by coupling of cyclotron motion of carriers with the Alfven wave propagating in the material.
{"title":"Nonlinear cyclotron resonance of rare-earth semimetals","authors":"M. Motokawa, M. Yoshida, K. Koyama","doi":"10.1109/ICIMW.2002.1076051","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076051","url":null,"abstract":"The cyclotron resonance is the best way to determine the effective masses of conductors and it is interesting to compare them with other effective masses determined by the de Haas oscillations. According to Kohn's theorem, they are not necessarily coincident with each other because an electron-electron correlation in the strongly correlated electron systems contributes to only the case of the de Haas oscillations. This argument has been studied in the case of organic conductors. On the other hand, it has been difficult to observe the cyclotron resonance absorption in rare-earth semimetals due to necessity of high frequency equipment, high magnetic field, very low temperature and high quality specimen. We have succeeded in observing cyclotron resonance in some rare-earth monopnictide compounds RX (R=rare earth atom, X=pnictgen atom) with NaCl type crystal structure and discussed the relationship between two kinds of masses of these materials. As reference materials, nonmagnetic LaSb and PrSb were also studied. In these cases, we have found new nonlinear resonance lines in addition to the normal cyclotron resonance whose resonance frequencies are linear with respect to magnetic field intensity. We ascribe this effect to the Doppler shift caused by coupling of cyclotron motion of carriers with the Alfven wave propagating in the material.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78355233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076102
C. Domier, B. Deng, J. Wang, Z. Xia, N. Luhmann, E. Mazzucato, T. Munsat, H. Park, A. Donne, M. J. van de Pol
A system capable of simultaneous 2-D imaging of electron density and temperature turbulence on TEXTOR is presently under development. Concept design details are presented. The system combines both electron temperature and density diagnostic techniques into a single instrument capable of the simultaneous measurement of both fluctuations (both turbulent and coherent) on the TEXTOR tokamak.
{"title":"2-D fluctuation imaging diagnostic for TEXTOR","authors":"C. Domier, B. Deng, J. Wang, Z. Xia, N. Luhmann, E. Mazzucato, T. Munsat, H. Park, A. Donne, M. J. van de Pol","doi":"10.1109/ICIMW.2002.1076102","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076102","url":null,"abstract":"A system capable of simultaneous 2-D imaging of electron density and temperature turbulence on TEXTOR is presently under development. Concept design details are presented. The system combines both electron temperature and density diagnostic techniques into a single instrument capable of the simultaneous measurement of both fluctuations (both turbulent and coherent) on the TEXTOR tokamak.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78532243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076198
A. Arnold, G. Dammertz, D. Wagner, M. Thumm
This paper shows recent measurements on a newly designed mode generator for cold tests of the quasi-optical mode converter system of step-tunable gyrotrons at FZK. This mode generator was designed to excite more than one mode by choosing a broadband quasi-optical method. 4 modes at different frequencies have been found and assigned to their mode numbers. The used measurement setup and the measured mode pattern are shown.
{"title":"Measurements on a mode generator for cold tests of step-tunable gyrotrons","authors":"A. Arnold, G. Dammertz, D. Wagner, M. Thumm","doi":"10.1109/ICIMW.2002.1076198","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076198","url":null,"abstract":"This paper shows recent measurements on a newly designed mode generator for cold tests of the quasi-optical mode converter system of step-tunable gyrotrons at FZK. This mode generator was designed to excite more than one mode by choosing a broadband quasi-optical method. 4 modes at different frequencies have been found and assigned to their mode numbers. The used measurement setup and the measured mode pattern are shown.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78019860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076197
J. Jin, Shi-Chang Zhang, Xiaoping Liang, C. Qiu
In this paper the beam transmission of a millimeter wave free-electron laser (FEL) experiment is investigated. The simulation results show a total loss of 34% of the electron beam current in the Group-I orbits regime, which is far smaller than the previous simulations, but no loss of the e-beam current is found in the Group-II orbits regime and the reversed guide magnetic field regime. The influence of the initial transverse velocity of the electron beam on the output power for the reversed guide magnetic field regime is also investigated.
{"title":"Parameter optimum in a free-electron laser","authors":"J. Jin, Shi-Chang Zhang, Xiaoping Liang, C. Qiu","doi":"10.1109/ICIMW.2002.1076197","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076197","url":null,"abstract":"In this paper the beam transmission of a millimeter wave free-electron laser (FEL) experiment is investigated. The simulation results show a total loss of 34% of the electron beam current in the Group-I orbits regime, which is far smaller than the previous simulations, but no loss of the e-beam current is found in the Group-II orbits regime and the reversed guide magnetic field regime. The influence of the initial transverse velocity of the electron beam on the output power for the reversed guide magnetic field regime is also investigated.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79380318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076148
A. Grudiev, K. Schunemann
The presented numerical results reveal important details of the injection-locked operation of the gyro-BWO and its dependence on the external magnetic field. Increasing the magnetic field leads to an operating frequency jump due to the excitation of the undesired taper mode which reduces the magnetic tuning bandwidth. Moreover, significant modifications of the locking bandwidth curve have been observed when the magnetic field is tuned.
{"title":"Numerical study of an injection-locked gyro-BWO","authors":"A. Grudiev, K. Schunemann","doi":"10.1109/ICIMW.2002.1076148","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076148","url":null,"abstract":"The presented numerical results reveal important details of the injection-locked operation of the gyro-BWO and its dependence on the external magnetic field. Increasing the magnetic field leads to an operating frequency jump due to the excitation of the undesired taper mode which reduces the magnetic tuning bandwidth. Moreover, significant modifications of the locking bandwidth curve have been observed when the magnetic field is tuned.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81750192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076065
R. Kadlec, H. Němec, P. Kužel
Describes the increasing effort to develop optical pump-terahertz probe (OPTP) experiments as a tool for studying transient processes following excitation by an optical pulse, e.g. in semiconductors, superconductors and solvated chromophores. If the timescale of the investigated process is much longer (hundreds of ps) than the duration of the THz probing pulse, the experimental data can be evaluated using the formalism for steady-state cases: the measured THz waveforms provide complex spectra as a function of the pump-probe delay. However, if the relaxation occurs within picoseconds or faster, this approach will fail, since different parts of one temporal waveform correspond to different states of the sample, resulting in a frequency mixing. Thus, a method is necessary to find the unknown non-equilibrium part of the response function. We have developed a general frequency domain theory which can serve as a guide for performing the experiment.
{"title":"Frequency-domain approach to evaluation of data obtained in optical pump-terahertz probe experiments","authors":"R. Kadlec, H. Němec, P. Kužel","doi":"10.1109/ICIMW.2002.1076065","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076065","url":null,"abstract":"Describes the increasing effort to develop optical pump-terahertz probe (OPTP) experiments as a tool for studying transient processes following excitation by an optical pulse, e.g. in semiconductors, superconductors and solvated chromophores. If the timescale of the investigated process is much longer (hundreds of ps) than the duration of the THz probing pulse, the experimental data can be evaluated using the formalism for steady-state cases: the measured THz waveforms provide complex spectra as a function of the pump-probe delay. However, if the relaxation occurs within picoseconds or faster, this approach will fail, since different parts of one temporal waveform correspond to different states of the sample, resulting in a frequency mixing. Thus, a method is necessary to find the unknown non-equilibrium part of the response function. We have developed a general frequency domain theory which can serve as a guide for performing the experiment.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82218941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076194
D. Goryushko, A. Shmat’ko
Research of the peculiarities of wave beam scattering by a structure with gyrotropy in the presence of magnetic losses is carried out. In this work the solution of the two-dimensional problem of scattering of a Gaussian wave beam incident on a ferrite layer with a magneto-dielectric sub-layer is considered. It is shown that there is the capability of controlling the spatial distribution of the scattered field over a wide range for various thicknesses of the gyrotropic layer by changing the constant magnetic field.
{"title":"Scattering of the Gaussian beams on two-layer structure with gyrotropy","authors":"D. Goryushko, A. Shmat’ko","doi":"10.1109/ICIMW.2002.1076194","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076194","url":null,"abstract":"Research of the peculiarities of wave beam scattering by a structure with gyrotropy in the presence of magnetic losses is carried out. In this work the solution of the two-dimensional problem of scattering of a Gaussian wave beam incident on a ferrite layer with a magneto-dielectric sub-layer is considered. It is shown that there is the capability of controlling the spatial distribution of the scattered field over a wide range for various thicknesses of the gyrotropic layer by changing the constant magnetic field.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82235723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-16DOI: 10.1109/ICIMW.2002.1076123
L. Dressman, D. Mcdermott, Y. Hirata, N. Luhmann, D. Gallagher, T. Spencer
While high conversion efficiency has been demonstrated in peniotrons, practical application of the device requires that power be efficiently extracted from the cavity. The UCD peniotron is designed to achieve high overall device efficiency and power output (130 kW peak) by employing an over-coupled cavity driven by a Northrop Grumman Cusp gun. Stability is insured through the use of a fundamental-mode interaction with the second cyclotron harmonic of the axis-encircling electron beam.
{"title":"Highly efficient 34 GHz peniotron","authors":"L. Dressman, D. Mcdermott, Y. Hirata, N. Luhmann, D. Gallagher, T. Spencer","doi":"10.1109/ICIMW.2002.1076123","DOIUrl":"https://doi.org/10.1109/ICIMW.2002.1076123","url":null,"abstract":"While high conversion efficiency has been demonstrated in peniotrons, practical application of the device requires that power be efficiently extracted from the cavity. The UCD peniotron is designed to achieve high overall device efficiency and power output (130 kW peak) by employing an over-coupled cavity driven by a Northrop Grumman Cusp gun. Stability is insured through the use of a fundamental-mode interaction with the second cyclotron harmonic of the axis-encircling electron beam.","PeriodicalId":23431,"journal":{"name":"Twenty Seventh International Conference on Infrared and Millimeter Waves","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90100558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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