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RISS 인기검색어
- 검색키워드
- 저자 : Kinion, D. (검색결과 2 건)
- 무료
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- 유료
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An Ultra Low-noise Radio Frequency Amplifier Based on a DC SQUID
Muck, Michael,Ande, Marc-Olivier,Kinion, Darin,Clarke, John The Korean Superconductivity Society 2000 Progress in superconductivity Vol.2 No.1
We have developed an extremely sensitive radio frequency amplifier based on the dc superconducting quantum interference device (dc SQUID). Unlike a conventional semiconductor amplifier, a SQUID can be cooled to ultra-low temperatures (100 mK or less) and thus potentially achieve a much lower noise temperature. In a conventional SQUID amplifier, where the integrated input coil is operated as a lumped element, parasitic capacitance between the coil and the SQUID washer limits the frequency up to which a substantial gain can be achieved to a few hundred MHz. This problem can be circumvented. by operating the input coil of the SQUID as a microstrip resonator: instead of connecting the input signal between the two ends of the coil, it is connected between the SQUID washer and one end of the coil; the other end is left open. Such amplifiers have gains of 15 dB or more at frequencies up to 3 GHz. If required, the resonant frequency of the microstrip can be tuned by means of a varactor diode connected across the otherwise open end of the resonator. The noise temperature of microstrip SQUID amplifiers was measured to be between 0.5 K $\pm$ 0.3 K at a frequency of 80 MHz and 1.5 K $\pm$: 1.2 K at 1.7 GHz, when the SQUID was cooled to 4.2 K. An even lower noise temperature can be achieved by cooling the SQUID to about 0.4 K. In this case, a noise temperature of 100 mK $\pm$ 20 mK was achieved at 90 MHz, and of about 120 $\pm$ 100 mK at 440 MHz.
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SQUID-Based Microwave Cavity Search for Dark-Matter Axions
Asztalos, S. J.,Carosi, G.,Hagmann, C.,Kinion, D.,van Bibber, K.,Hotz, M.,Rosenberg, L. J,Rybka, G.,Hoskins, J.,Hwang, J.,Sikivie, P.,Tanner, D. B.,Bradley, R.,Clarke, J. American Physical Society 2010 Physical Review Letters Vol.104 No.4
<P>Axions in the microeV mass range are a plausible cold dark-matter candidate and may be detected by their conversion into microwave photons in a resonant cavity immersed in a static magnetic field. We report the first result from such an axion search using a superconducting first-stage amplifier (SQUID) replacing a conventional GaAs field-effect transistor amplifier. This experiment excludes KSVZ dark-matter axions with masses between 3.3 microeV and 3.53 microeV and sets the stage for a definitive axion search utilizing near quantum-limited SQUID amplifiers.</P>
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