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Shitov, S. V., Levitchev, M., Veretennikov, A. V., Koshelets, V. P., Prokopenko, G. V., Filippenko, L. V., et al. (2001). Superconducting integrated receiver as 400-600 GHz tester for coolable devices. IEEE Trans. Appl. Supercond., 11(1), 832–835.
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Gol’tsman, G., Okunev, O., Chulkova, G., Lipatov, A., Dzardanov, A., Smirnov, K., et al. (2001). Fabrication and properties of an ultrafast NbN hot-electron single-photon detector. IEEE Trans. Appl. Supercond., 11(1), 574–577.
Abstract: A new type of ultra-high-speed single-photon counter for visible and near-infrared wavebands based on an ultrathin NbN hot-electron photodetector (HEP) has been developed. The detector consists of a very narrow superconducting stripe, biased close to its critical current. An incoming photon absorbed by the stripe produces a resistive hotspot and causes an increase in the film’s supercurrent density above the critical value, leading to temporary formation of a resistive barrier across the device and an easily measurable voltage pulse. Our NbN HEP is an ultrafast (estimated response time is 30 ps; registered time, due to apparatus limitations, is 150 ps), frequency unselective device with very large intrinsic gain and negligible dark counts. We have observed sequences of output pulses, interpreted as single-photon events for very weak laser beams with wavelengths ranging from 0.5 /spl mu/m to 2.1 /spl mu/m and the signal-to-noise ratio of about 30 dB.
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Skalare, A., McGrath, W. R., Echternach, P. M., Leduc, H. G., Siddiqi, I., Verevkin, A., et al. (2001). Aluminum hot-electron bolometer mixers at submillimeter wavelengths. IEEE Trans. Appl. Supercond., 11(1), 641–644.
Abstract: Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 Ω down to about 9 Ω per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 μm long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies.
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Kawamura, J., Tong, C. - Y. E., Blundell, R., Papa, D. C., Hunter, T. R., Patt, F., et al. (2001). Terahertz-frequency waveguide NbN hot-electron bolometer mixer. IEEE Trans. Appl. Supercond., 11(1), 952–954.
Abstract: We have developed a low-noise waveguide heterodyne receiver for operation near 1 THz using phonon-cooled NbN hot-electron bolometers. The mixer elements are submicron-sized microbridges of 4 nm-thick NbN film fabricated on a quartz substrate. Operating at a bath temperature of 4.2 K, the double-sideband receiver noise temperature is 760 K at 1.02 THz and 1100 K at 1.26 THz. The local oscillator is provided by solid-state sources, and power measured at the source is less than 1 /spl mu/W. The intermediate frequency bandwidth exceeds 2 GHz. The receiver was used to make the first ground-based heterodyne detection of a celestial spectroscopic line above 1 THz.
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Antipov, S. V., Svechnikov, S. I., Smirnov, K. V., Vakhtomin, Y. B., Finkel, M. I., Goltsman, G. N., et al. (2001). Noise temperature of quasioptical NbN hot electron bolometer mixers at 900 GHz. Physics of Vibrations, 9(4), 242–245.
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Svechnikov, S. I., Antipov, S. V., Vakhtomin, Y. B., Goltsman, G. N., Gershenzon, E. M., Cherednichenko, S. I., et al. (2001). Conversion and noise bandwidths of terahertz NbN hot-electron bolometer mixers. Physics of Vibrations, 9(3), 205–210.
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Hsiao, F. Z., Lin, M. C., Wang, C., Lee, D. S., Chen, J. R., Hilbert, B., et al. (2001). The liquid helium cryogenic system for the superconducting cavity in SRRC. In Proc. Particle Accelerator Conference (Vol. 2, pp. 1604–1606).
Abstract: A 500 MHz superconducting cavity will replace the current copper cavity and begin to operate in the beginning of the year 2003. A liquid helium cryogenic system provides the cavity at 4.5 K a cooling capacity of 255 W without LN2 pre-cooling and a liquefaction rate of 110 liter/hour with LN2 pre-cooling. A safety factor of 1.5 is used to estimate the heat load from the superconducting cavity and the heat loss from the transfer lines. With the LN2 pre-cooling, this cooling system provides a cooling capacity of up to 450 W to cool down the additional superconducting Landau cavity. The capacity of the system can be tuned using a frequency driver installed at the compressor station. The pressure fluctuations of the dewar and of the suction line are kept to the same stability requirement that of the cavity cryostat to minimize the influence in cavity operation. A shutdown period for maintenance of more than 8000 hours for the cryogenic system is expected without interfering with the continuous operation of the superconducting cavity.
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Kroug, M. (2001). Hot electron bolometric mixers for a quasi-optical terahertz receiver. Ph.D. thesis, , Chalmers University of Technology, Gothenburg, Sweden.
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Karpov, A., Miller, D., Rice, F., Zmuidzinas, J., Stern, J. A., Bumble, B., et al. (2001). Low noise 1.2 THz SIS receiver. In C. Iit.u.t.e of T. Jet Propulsion Laboratory (Ed.), Proc. 12th Int. Symp. Space Terahertz Technol. (pp. 21–22). San Diego, CA, USA.
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Shi, S. C., Chin, C. C., Wang, M. J., Shan, W. L., Zhang, W., & Noguchi, T. (2001). Development of a 600–720 GHz SIS Mixer for the SMART. In C. Iit.u.t.e of T. Jet Propulsion Laboratory (Ed.), Proc. 12th Int. Symp. Space Terahertz Technol. (215). San Diego, CA, USA.
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