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The Microstrip SQUID Amplier in the Axion Dark Matter eXperiment (ADMX)
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | The Microstrip SQUID Amplier in the Axion Dark Matter eXperiment (ADMX). |
| 개인저자 | O'Kelley, Sean Robert. |
| 단체저자명 | University of California, Berkeley. Physics. |
| 발행사항 | [S.l.]: University of California, Berkeley., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 284 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-05B. Dissertation Abstract International |
| ISBN | 9781392355336 |
| 학위논문주기 | Thesis (Ph.D.)--University of California, Berkeley, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-05, Section: B.
Advisor: Clarke, John. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | We present the development and performance of low noise tunable Microstrip SQUID Amplifiers (MSAs) operating at frequencies near 1 GHz for use in ADMX. The MSA has been used in ADMX to produce published exclusions to the axion mass and density in our galactic dark matter halo. The exclusions published by ADMX and achieved with an MSA are the most stringent exclusions to date.Hypotheses on the nature of dark matter vary, so that the designs and operating principles of experimental dark matter searches vary as well. Every search is similar in that it is an endeavor to discover some very small signal--if the signal were not currently beyond perception we would not call our quarry "dark matter". In ADMX the principle of operation is to convert axions into photons in a strong magnetic field, enhance that conversion rate with a resonant cavity tuned to the photon frequency, and record the presence of those converted photons. The trick in any direct detection experiment is to increase signal and decrease noise. In ADMX, the signal is increased by using a strong magnetic field, a high-Q cavity, and as large a volume as possible. The noise is reduced by operating at a low physical temperature and using a low-noise amplifier. That amplifier is the titular MSA. The MSA operates as a DC-Superconducting QUantum Interference Device (DC-SQUID) coupled to a RF microstrip resonator such that the magnetic field component of a standing wave on the microstrip couples to the SQUID, generating an amplified voltage signal across the SQUID terminals, which is transmitted to the rest of the detection chain. The MSA has a noise temperature of 50 to 200 mK, enabling a search rate about 56 times faster than would be possible using the best available commercial microwave amplifiers.We present background motivations and theoretical underpinnings to the axion dark matter search at a level appropriate for the graduate student first entering the field. We also include a substantial discussion of practical considerations and methods intended as a "quick-start" guide for experimentalists. Our guiding principle is to provide the handbook we wish we had owned as a graduate student in physics first approaching the dark matter search, axion physics, and MSA design.We demonstrate MSAs operating at frequencies as low as 350 MHz and as high as 1,160 MHz with a typical Q of 60, typical gain of 20 dB, and typical tunability range of about about 20% of the center frequency. We use GaAs varactor diodes to tune the MSAs, and demonstrate a surprising transition in varactor capacitance between about 2 K and 200 mK, which we believe has not been reported to date and may shed light on the theory of shallow negative U centers in semiconductors. |
| 일반주제명 | Physics. Astrophysics. |
| 언어 | 영어 |
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