[
{
"id": "thesis:6367",
"collection": "thesis",
"collection_id": "6367",
"cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022011-085219561",
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"basename": "Halverson_nw_2002.pdf",
"content": "final",
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"url": "/6367/1/Halverson_nw_2002.pdf",
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"type": "thesis",
"title": "A Measurement of the Cosmic Microwave Background Angular Power Spectrum with DASI",
"author": [
{
"family_name": "Halverson",
"given_name": "Nils William",
"clpid": "Halverson-Nils-William"
}
],
"thesis_advisor": [
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
}
],
"thesis_committee": [
{
"family_name": "Vahala",
"given_name": "Kerry J.",
"orcid": "0000-0003-1783-1380",
"clpid": "Vahala-K-J"
},
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
},
{
"family_name": "Johnson",
"given_name": "William Lewis",
"clpid": "Johnson-W-L"
},
{
"family_name": "Lange",
"given_name": "Andrew E.",
"clpid": "Lange-A-E"
},
{
"family_name": "Phillips",
"given_name": "Thomas G.",
"clpid": "Phillips-T-G"
},
{
"family_name": "Readhead",
"given_name": "Anthony C. S.",
"orcid": "0000-0001-9152-961X",
"clpid": "Readhead-A-C-S"
}
],
"local_group": [
{
"literal": "div_eng"
}
],
"abstract": "The Cosmic Microwave Background (CMB) has long been recognized as an astounding source of information about the early Universe. In this thesis we describe the design,\r\nimplementation, and first-year results of the Degree Angular Scale Interferometer (DASI), a compact interferometer designed to measure the angular power spectrum of the CMB. We discuss details of the optics, receivers, and power spectrum analysis, including the use of constraint matrices to project out contaminants and test for correlations with diffuse foreground templates.\r\n\r\nWe present a measurement of the CMB angular power spectrum in the multipole range l \u2248 100- 900 in nine bands. The measured fluctuations have a temperature spectral index of \u03b2 = -0.1 \u00b1 0.2 (1\u03c3) consistent with CMB. We find no evidence of foregrounds other than point sources in the data. We detect a first peak in the power spectrum at l ~ 200, a second peak in the power spectrum at l ~ 550, and a rise in the power spectrum at l ~ 800 which is indicative of a third, consistent with inflationary theories. \r\n\r\nUsing the DASI measurement along with COBE DMR data, and adopting conservative priors on the Hubble parameter h > 0.45 and an optical depth due to reionization 0.0 \u2264 \u03c4_c \u2264 0.4, we constrain the total density of the Universe \u03a9_(tot) = 1.04 \u00b1 0.06, the spectral index of the primordial density fluctuations n_s = 1.01^(+0.08)_(-0.06), and the physical baryon density \u03a9_bh^2 = 0.022^(+0.004)_(-0.003) among others (all 68% confidence limits). These constraints are consistent with inflation and estimates of \u03a9_bh^2 from Big Bang Nucleosynthesis. With prior h = 0.72 \u00b1 0.08, we constrain the matter density \u03a9_m = 0.40 \u00b1 0.15, and the vacuum energy density \u03a9_\u039b = 0.60 \u00b1 0.15, indicating from CMB data the presence of dark matter and dark energy in the Universe.",
"doi": "10.7907/BEJN-HQ49",
"publication_date": "2002",
"thesis_type": "phd",
"thesis_year": "2002"
},
{
"id": "thesis:480",
"collection": "thesis",
"collection_id": "480",
"cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02032004-163517",
"primary_object_url": {
"basename": "thesis.pdf",
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"license": "other",
"mime_type": "application/pdf",
"url": "/480/1/thesis.pdf",
"version": "v2.0.0"
},
"type": "thesis",
"title": "Dual polarized and balanced receivers at millimeter and submillimeter wavelengths",
"author": [
{
"family_name": "Chattopadhyay",
"given_name": "Goutam",
"orcid": "0000-0001-7942-5025",
"clpid": "Chattopadhyay-Goutam"
}
],
"thesis_advisor": [
{
"family_name": "Zmuidzinas",
"given_name": "Jonas",
"clpid": "Zmuidzinas-J"
}
],
"thesis_committee": [
{
"family_name": "Rutledge",
"given_name": "David B.",
"clpid": "Rutledge-D-B"
},
{
"family_name": "Zmuidzinas",
"given_name": "Jonas",
"clpid": "Zmuidzinas-J"
},
{
"family_name": "Hajimiri",
"given_name": "Ali",
"clpid": "Hajimiri-A"
},
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
},
{
"family_name": "Weinreb",
"given_name": "Sander",
"clpid": "Weinreb-S"
}
],
"local_group": [
{
"literal": "Caltech Submillimeter Observatory"
},
{
"literal": "Astronomy Department"
},
{
"literal": "div_eng"
}
],
"abstract": "Dramatic advances in millimeter and submillimeter wave receivers in recent years have resulted from the development of superconductor insulator superconductor (SIS) mixers, which now offer unsurpassed performance from 70 GHz to 1 THz. To increase the sensitivity of the receivers further at these frequencies, one needs to use dual-polarized and balanced receivers. When both the polarizations are received simultaneously, there is a square root of two improvement in the signal to noise ratio (SNR). Balanced mixers improve the sensitivity of receivers by suppressing local oscillator (LO) amplitude modulation (AM) noise and rejecting LO thermal noise. This thesis describes the design, fabrication and performance of mixers and components for low noise dual-polarized and balanced receivers at millimeter and submillimeter wavelengths both in quasi-optical and waveguide configurations. The quasi-optical receiver utilizes a novel cross-slot antenna on a silicon hyperhemispherical lens, two junction tuning circuits, niobium trilayer junctions, and an IF circuit containing a lumped element 180 degree hybrid. The antenna has four feed points, two for each polarization; and each feed point is coupled to a two-junction SIS mixer. For dual polarization operation, the mixer is mounted in such a way that a single LO can pump the junctions for both the polarizations. For the balanced receiver, the LO and the RF signals are coupled to the mixer in orthogonal polarizations using a wire-grid polarizer. For waveguide dual polarization receivers, a moderately broadband septum ortho-mode transducer (OMT) is designed and experimental results are presented at millimeter wavelengths. Broadband finline OMTs are investigated for possible use at millimeter wavelengths, and experimental results of a finline OMT is presented at X-band.",
"doi": "10.7907/RMVX-0619",
"publication_date": "2000",
"thesis_type": "phd",
"thesis_year": "2000"
},
{
"id": "thesis:1059",
"collection": "thesis",
"collection_id": "1059",
"cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03222006-103422",
"primary_object_url": {
"basename": "Groesbeck_td_1995.pdf",
"content": "final",
"filesize": 12358555,
"license": "other",
"mime_type": "application/pdf",
"url": "/1059/1/Groesbeck_td_1995.pdf",
"version": "v3.0.0"
},
"type": "thesis",
"title": "The Contribution of Molecular Line Emission to Broadband Flux Measurements at Millimeter and Submillimeter Wavelengths",
"author": [
{
"family_name": "Groesbeck",
"given_name": "Todd Dickson",
"clpid": "Groesbeck-Todd Dickson"
}
],
"thesis_advisor": [
{
"family_name": "Phillips",
"given_name": "Thomas G.",
"clpid": "Phillips-T-G"
}
],
"thesis_committee": [
{
"family_name": "Phillips",
"given_name": "Thomas G.",
"clpid": "Phillips-T-G"
},
{
"family_name": "Blake",
"given_name": "Geoffrey A.",
"orcid": "0000-0003-0787-1610",
"clpid": "Blake-G-A"
},
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
},
{
"family_name": "Kavanagh",
"given_name": "Ralph William",
"clpid": "Kavanagh-R-W"
}
],
"local_group": [
{
"literal": "Astronomy Department"
},
{
"literal": "div_pma"
}
],
"abstract": "We present measurements of the ratio of flux carried by molecular emission lines to the total flux observed from six astronomical sources in the 330-360 GHz frequency range, demonstrating that the integrated line emission can represent a significant fraction, and in some cases even the majority, of the total flux observed. Given the narrow widths of these emission lines for most sources in the interstellar medium, it has generally been assumed that the contribution of the integrated lines would be negligible when compared to the continuum flux measured by a very broadband instrument. We extend the previous work by Sutton et al. (1984), which demonstrated that line emission was responsible for a large part of the total flux observed from Orion-KL, by presenting observations at higher frequencies of Orion-KL and several additional sources. These observations provide the most comprehensive determination of the ratio of line flux to continuum flux yet made at submillimeter wavelengths.
\r\n\r\nWe have performed spectral line surveys of the star-forming regions Orion-KL, Orion-S, and IRAS 16293-2422, and the evolved stars IRC +10216, VY Canis Majoris, and OH 231.8+4.2. Observations for Orion-KL and IRC +10216 give continuous frequency coverage over approximately the 330-360 GHz band; for the other sources the coverage ranges between 30 and 60% of the same frequency band. Comparisons of the line survey data with total flux measurements demonstrates that the contribution of the integrated line emission to the total flux at these frequencies ranges from as low as ~10% for Orion-S and IRAS 16293-2422 to at least ~60% for Orion-KL and IRC +10216. We also estimate the amount of flux carried in weak lines below our sensitivity limits \r\nbased on the observed distributions of line intensities.
\r\n\r\nAn improved deconvolution method has been used to obtain a single sideband spectrum from the double sideband observations. We have also developed computer versions of line catalogs which allow immediate line identification and analysis, assuming conditions of local thermodynamic equilibrium (LTE) prevail. The same catalog programs also permit simulation of emission line spectra for arbitrary molecular abundances and excitation temperatures, again assuming LIE. For each of the observed sources, we present simulations of the spectrum from 0 to 1000 GHz, using molecular parameters derived from our data and additional published observations. In all cases, the simulations indicate that the relative importance of the line emission decreases at higher frequencies (~ > 700 GHz). We discuss the significance of these findings regarding the determination of dust parameters from broadband flux measurements, concluding that such measurements must be corrected for possible line flux contributions before they can be reliably used.
",
"doi": "10.7907/rbaq-gb42",
"publication_date": "1995",
"thesis_type": "phd",
"thesis_year": "1995"
}
]