Edward Tong, C. - Y., Loudkov, D. N., Paine, S. N., Marrone, D. P., & Blundell, R. (2005). Vector measurement of the beam pattern of a 1.5 THz superconducting HEB receiver. In Proc. 16th Int. Symp. Space Terahertz Technol. (pp. 453–456).
Abstract: Near-field vector beam pattern of the 1.5 THz superconducting Hot Electron Bolometer (HEB) receiver currently in operation in Northern Chile has been performed in our laboratory. Using an open waveguide probe, we have mapped both the amplitude and phase of the beam emerging from our 1.5 THz HEB receiver package, across a number of planes along the line of propagation of the radio-beam. With an integration time of about 100 ms per point, a signal-to-noise ratio of about 25 dB was achieved for a beam waist of 3.5 mm. These measurements have proved to be invaluable in achieving good alignment between the cryostat housing the HEB mixer and the remainder of the receiver and telescope optics. The accuracy of our beam measurement is estimated to be ±0.2 mm in position and ±5 arc minutes in angular displacement.
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Semenov, A., Il'yin, K., Siegel, M., Smirnov, A., Pavlov, S., Richter, H., et al. (2006). Intermediate frequency bandwidth of a hot-electron mixer: Comparision with bolometric models. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 73–76). Paris, France.
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Jiang, L., Miao, W., Zhang, W., Li, N., Lin, Z. H., Yao, Q. J., et al. (2006). Characterization of quasi-optical NbN phonon-cooled superconducting HEB mixers. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 55–58).
Abstract: In this paper, we thoroughly investigate the performance of quasi-optical NbN phonon-cooled superconducting hot-electron bolometer (HEB) mixers, cryogenically cooled by a close-cycled 4-K refrigerator at 500 GI-1z and 850 GHz. The uncorrected lowest receiver noise Abstract---In temperatures measured are 800 K at 500 CHz without anti-reflection coating, and 1000 K @ 850 GHz with a 50 11M thick Mylar anti-reflection coating. The dependence of receiver noise temperature on the critical current and bath temperature of HEB mixer is also investigated here. Lifetime of quasi-optical superconducting NbN HEB mixers of different volumes, room temperature resistances, and critical temperatures are thoroughly studied. Increased room temperature resistance with time over the initial resistance changes between 1 and 1.2, and the reduced critical current with time over the initial value fluctuates slightly around 0.7 for most HEB mixers even of different volumes, room temperature resistances, and critical temperatures. The critical current degrades sharply vvhile room temperature resistance varies over 1.25.
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Cherednichenko, S., Drakinskiy, V., Baubert, J., Lecomte, B., Dauplay, F., Krieg, J. - M., et al. (2007). 2.5 THz multipixel heterodyne receiver based on NbN HEB mixers. In Proc. 18th Int. Symp. Space Terahertz Technol. (112).
Abstract: A 16 pixel heterodyne receiver for 2.5 THz has been developed based on NbN superconducting hot-electron bolometer (HEB) mixers. The receiver uses a quasioptical RF coupling approach where HEB mixers are integrated into double dipole antennas on 1.5μm thick Si3N4 / SiO2 membranes. Spherical mirrors (one per pixel) and backshort distance from the antenna have been used to design the output mixer beam profile. The camera design allows all 16 pixel IF readout in parallel. Measurements of the mixers sensitivity and the input RF band are presented, and compared against calculations.
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Semenov, A., Richter, H., Smirnov, A., Günther, B., Hübers, H. - W., Il’in, K., et al. (2007). Development of HEB mixers for GREAT and for security screening. In Proc. 18th Int. Symp. Space Terahertz Technol. (184).
Abstract: We report the study on the quasioptical coupling efficiency and the gain bandwidth of NbN hot-electron bolometer mixers developed for the 4.7 THz channel of the German receiver for Astronomy at THz-frequencies (GREAT) and for security screening at subterahertz frequencies. Radiation coupling efficiency and directive properties of integrated lens antennas with log-spiral, log-periodic and double-slot planar feeds coupled to a hot-electron bolometer were experimentally studied at frequencies from 1 THz to 6 THz and compared with simulations based on the method of moments and the physical-optics ray tracing. For all studied antennas the modeled spectral dependence of the coupling efficiency fits to the experimental data obtained with both Fourier transform spectroscopy and noise temperature measurements only if the complex impedance of the bolometer is explicitly taken into account. Our experimental data did not indicate any noticeable contribution of the quantum noise to the system noise temperature. The experimentally observed deviation of the beam pattern from the model prediction increases with frequency and is most likely due to a non- ideality of the presently used lenses. Study of the intermediate frequency mixer gain at local oscillator (LO) frequencies between 2.5 THz and 0.3 THz showed an increase of the gain bandwidth at low LO frequencies that was understood as the contribution of the direct interaction of magnetic vortices with the radiation field. We have found that the non- homogeneous hot-spot model more adequately describes variation of the intermediate frequency bandwidth with the applied local oscillator power than any of uniform mixer models. The state-of-the-day performance of the GREAT 4.7-THz channel and the 0.8-THz security scanner will be presented.
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Ryabchun, S., Tong, C. -yu E., Blundell, R., Kimberk, R., & Gol’tsman, G. (2007). Stabilisation of a terahertz hot-electron bolometer mixer with microwave feedback control. In Proc. 18th Int. Symp. Space Terahertz Technol. (pp. 193–198).
Abstract: We report on implementation of microwave feedback control loop to stabilise the performance of an HEB mixer receiver. It is shown that the receiver sensitivity increases by a factor of 4 over a 16-minute scan, and the corresponding Allan time increases up to 10 seconds, as opposed to an open loop value of 1 second. Our experiments also demonstrate that the receiver sensitivity is limited by the intermediate frequency chain.
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Shitov, S. V., Inatani, J., Shan, W. - L., Takeda, M., Wang, Z., Uvarov, A. V., et al. (2008). Measurement of emissivity of the ALMA antenna panel at 840 GHz using NbN-based heterodyne SIS receiver. In Proc. 19th Int. Symp. Space Terahertz Technol. (pp. 263–266).
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de Lange, G., Krieg, J. - M., Honingh, N., Karpov, A., & Cherednichenko, S. (2008). Performance of the HIFI flight mixers. In Proc. 19th Int. Symp. Space Terahertz Technol. (pp. 98–105).
Abstract: We summarize the technology and final results of the superconducting heterodyne SIS and HEB mixers that are developed for the HIFI instrument. Within HIFI 7 frequency bands cover the frequency range from 480 GHz to 1910 GHz. We describe the different device technologies and optical coupling schemes that are used to cover the frequency bands. The efforts of the different mixer teams that participate in HIFI have contributed to an instrument that will have unprecedented sensitivity and frequency coverage.
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Cherednichenko, S., Drakinskiy, V., Lecomte, B., Dauplay, F., Krieg, J. - M., Delorme, Y., et al. (2008). Terahertz heterodyne array based on NbN HEB mixers. In Proc. 19th Int. Symp. Space Terahertz Technol. (43).
Abstract: A 16 pixel heterodyne receiver for 2.5 THz is been developed based on NbN superconducting hot-electron bolometer (HEB) mixers. The receiver uses a quasioptical RF coupling approach where HEB mixers are integrated into double dipole antennas on 1.5μm thick Si3N4 / SiO2 membranes. Miniature mirrors (one per pixel) and back short for the antenna were used to design the output mixer beam profile. The camera design allows all 16 pixel IF readout in parallel. The gain bandwidth of the HEB mixers on Si3N4 / SiO 2 membranes was found to be about 3 GHz, when an MgO buffer layers is applied on the membrane. We will also present the progress in the camera heterodyne tests.
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Uzawa, Y., Kojima, T., Kroug, M., Takeda, M., Candotti, M., Fujii, Y., et al. (2009). Development of the 787-950 GHz ALMA band 10 cartridge. In Proc. 20th Int. Symp. Space Terahertz Technol. (p. 12).
Abstract: We are developing the Atacama Large Millimeter/Submillimeter Array (ALMA) Band 10 (787-950 GHz) receiver cartridge. The incoming beam from the 12-m antenna is reflected by a pair of two ellipsoidal mirrors placed in the cartridge, and then split into two orthogonal polarizations by a free-standing wire-grid. Each beam enters a corrugated feed horn attached to a double-side-band (DSB) mixer block. The mixer uses a full-height waveguide and an NbTiN- or NbN-based superconductor-insulator-superconductor (SIS) mixer chip. We are testing the following three types of mixer chips: 1) Nb SIS junctions + NbTiN/SiO2/Al tuning circuits on a quartz substrate, 2) Nb SIS junctions + NbN/SiO2/Al tuning circuits on an MgO substrate, and 3) NbN SIS junctions + NbN or NbTiN tuning circuits on an MgO substrate. The IF system uses a 4-12-GHz cooled low-noise InP-based MMIC amplifier developed by Caltech. So far, the type 1) has shown the best performance. At LO frequencies from 800 to 940 GHz, the mixer noise temperatures measured by using the standard Y-factor method were below 240 K at an operating physical temperature of 4 K. The lowest noise temperature, 169 K, was obtained at the center frequency of the band 10, as designed. These well-developed technologies will be implemented in the band 10 cartridge to achieve the ALMA specifications.
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