Superconducting microwave resonators have the potential to revolutionize submillimeter and far-infrared astronomy, and with it our understanding of the universe. The field of low-temperature detector technology has reached a point where extremely sensitive devices like transition-edge sensors are now capable of detecting radiation limited by the background noise of the universe. However, the size of these detector arrays are limited to only a few thousand pixels. This is because of the cost and complexity of fabricating large-scale arrays of these detectors that can reach up to 10 lithographic levels on chip, and the complicated SQUID-based multiplexing circuitry and wiring for readout of each detector. In order to make substantial progress, next- generation ground-based telescopes such as CCAT or future space telescopes require focal planes with large-scale detector arrays of 104\u2013106 pixels. Arrays using microwave kinetic inductance detectors (MKID) are a potential solution. These arrays can be easily made with a single layer of superconducting metal film deposited on a silicon substrate and pattered using conventional optical lithography. Furthermore, MKIDs are inherently multiplexable in the frequency domain, allowing \u223c 103 detectors to be read out using a single coaxial transmission line and cryogenic amplifier, drastically reducing cost and complexity.
\r\n\r\nAn MKID uses the change in the microwave surface impedance of a superconducting thin-film microresonator to detect photons. Absorption of photons in the superconductor breaks Cooper pairs into quasiparticles, changing the complex surface impedance, which results in a perturbation of resonator frequency and quality factor. For excitation and readout, the resonator is weakly coupled to a transmission line. The complex amplitude of a microwave probe signal tuned on-resonance and transmitted on the feedline past the resonator is perturbed as photons are absorbed in the superconductor. The perturbation can be detected using a cryogenic amplifier and subsequent homodyne mixing at room temperature. In an array of MKIDs, all the resonators are coupled to a shared feedline and are tuned to slightly different frequencies. They can be read out simultaneously using a comb of frequencies generated\r\nand measured using digital techniques.
\r\n\r\nThis thesis documents an effort to demonstrate the basic operation of \u223c 256 pixel arrays of lumped-element MKIDs made from superconducting TiNx on silicon. The resonators are designed and simulated for optimum operation. Various properties of the resonators and arrays are measured and compared to theoretical expectations. A particularly exciting observation is the extremely high quality factors (\u223c 3 \u00d7 107) of our TiNx resonators which is essential for ultra-high sensitivity. The arrays are tightly packed both in space and in frequency which is desirable for larger full-size arrays. However, this can cause a serious problem in terms of microwave crosstalk between neighboring pixels. We show that by properly designing the resonator geometry, crosstalk can be eliminated; this is supported by our measurement results. We also tackle the problem of excess frequency noise in MKIDs. Intrinsic noise in the form of an excess resonance frequency jitter exists in planar superconducting resonators that are made on dielectric substrates. We conclusively show that this noise is due to fluctuations of the resonator capacitance. In turn, the capacitance fluctuations are thought to be driven by two-level system (TLS) fluctuators in a thin layer on the surface of the device. With a modified resonator design we demonstrate with measurements that this noise can be substantially reduced. An optimized version of this resonator was designed for the multiwavelength submillimeter kinetic inductance camera (MUSIC) instrument for the Caltech Submillimeter Observatory.
" }, { "name": "Sumner, Matthew Casey", "degree": "PhD", "year": "2011", "title": "Optimizing End-to-End System Performance for Millimeter and Submillimeter Spectroscopy of Protostars: Wideband Heterodyne Receivers and Sideband-Deconvolution Techniques for Rapid Molecular-Line Surveys", "advisor": "Zmuidzinas, Jonas", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302011-143941777", "creators": [ { "name": { "family": "Sumner", "given": "Matthew Casey" }, "id": "Sumner-Matthew-Casey", "display_name": "Sumner, Matthew Casey" } ], "advisors": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "advisor", "display_name": "Zmuidzinas, Jonas" } ], "committee": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "chair", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "member", "display_name": "Phillips, Thomas G." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Chen", "given": "Yanbei" }, "id": "Chen-Yanbei", "role": "member", "display_name": "Chen, Yanbei" } ], "option_major": [ "physics" ], "doi": "10.7907/HD7X-2A80", "abstract": "This thesis describes the construction, integration, and use of a new 230-GHz ultra-wideband heterodyne receiver, as well as the development and testing of a new sideband-deconvolution algorithm, both designed to enable rapid, sensitive molecular-line surveys.
\r\n\r\nThe 230-GHz receiver, known as Z-Rex, is the first of a new generation of wideband receivers to be installed at the Caltech Submillimeter Observatory (CSO). Intended as a proof-of-concept device, it boasts an ultra-wide IF output range of \\sim 6 - 18 GHz, offering as much as a twelvefold increase in the spectral coverage that can be achieved with a single LO setting. A similarly wideband IF system has been designed to couple this receiver to an array of WASP2 spectrometers, allowing the full bandwidth of the receiver to be observed at low resolution, ideal for extra-galactic redshift surveys. A separate IF system feeds a high-resolution 4-GHz AOS array frequently used for performing unbiased line surveys of galactic objects, particularly star-forming regions. The design and construction of the wideband IF system are presented, as is the work done to integrate the receiver and the high-resolution spectrometers into a working system. The receiver is currently installed at the CSO where it is available for astronomers' use.
\r\n\r\nIn addition to demonstrating wideband design principles, the receiver also serves as a testbed for a synthesizer-driven, active LO chain that is under consideration for future receiver designs. Several lessons have been learned, including the importance of driving the final amplifier of the LO chain into saturation and the absolute necessity of including a high-Q filter to remove spurious signals from the synthesizer output. The on-telescope performance of the synthesizer-driven LO chain is compared to that of the Gunn-oscillator units currently in use at the CSO. Although the frequency agility of the synthesized LO chain gives it a significant advantage for unbiased line surveys, the cleaner signal and broader tuning range of the Gunn continue to make it the preferred choice.
\r\n\r\nThe receiver and high-resolution spectrometer system were brought into a fully operational state late in 2007, when they were used to perform unbiased molecular-line surveys of several galactic sources, including the Orion KL hot core and a position in the L1157 outflow. In order to analyze these data, a new data pipeline was needed to deconvolve the double-sideband signals from the receiver and to model the molecular spectra. A highly automated sideband-deconvolution system has been created, and spectral-analysis tools are currently being developed.
\r\n\r\nThe sideband deconvolution relies on chi-square minimization to determine the optimal single-sideband spectrum in the presence of unknown sideband-gain imbalances and spectral baselines. Analytic results are presented for several different methods of approaching the problem, including direct optimization, nonlinear root finding, and a hybrid approach that utilizes a two-stage process to separate out the relatively weak nonlinearities so that the majority of the parameters can be found with a fast linear solver. Analytic derivations of the Jacobian matrices for all three cases are presented, along with a new Mathematica utility that enables the calculation of arbitrary gradients.
\r\n\r\nThe direct-optimization method has been incorporated into software, along with a spectral simulation engine that allows different deconvolution scenarios to be tested. The software has been validated through the deconvolution of simulated data sets, and initial results from L1157 and Orion are presented.
\r\n\r\nBoth surveys demonstrate the power of the wideband receivers and improved data pipeline to enable exciting scientific studies. The L1157 survey was completed in only 20 hours of telescope time and offers moderate sensitivity over a > 50-GHz range, from 220 GHz to approximately 270 or 280 GHz. The speed with which this survey was completed implies that the new systems will permit unbiased line surveys to become a standard observational tool. The Orion survey is expected to offer ~ 30 mK sensitivity over a similar frequency range, improving previous results by an order of magnitude. The new receiver's ability to cover such broad bandwidths permits very deep surveys to be completed in a reasonable time, and the sideband-deconvolution algorithm is capable of preserving these low noise levels. Combined, these tools can provide line spectra with the sensitivity required for constraining astrochemical models and investigating prebiotic molecules.
" }, { "name": "Corder, Stuartt Allan", "degree": "PhD", "year": "2009", "title": "Optimizing Image Fidelity with Arrays", "advisor": "Sargent, Anneila Isabel", "url": "https://resolver.caltech.edu/CaltechETD:etd-10172008-054754", "creators": [ { "name": { "family": "Corder", "given": "Stuartt Allan" }, "id": "Corder-Stuartt-Allan", "display_name": "Corder, Stuartt Allan" } ], "advisors": [ { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "role": "advisor", "display_name": "Sargent, Anneila Isabel" } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "role": "member", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Phinney", "given": "E. Sterl" }, "id": "Phinney-E-S", "role": "member", "display_name": "Phinney, E. Sterl" }, { "name": { "family": "Carpenter", "given": "John M." }, "id": "Carpenter-J-M", "role": "member", "display_name": "Carpenter, John M." }, { "name": { "family": "Wright", "given": "Melvyn" }, "id": "Wright-M", "role": "member", "display_name": "Wright, Melvyn" }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "astrophys" ], "doi": "10.7907/Q7H2-2P58", "abstract": "Through simulations, I have investigated the limitations imposed upon the image fidelity of interferometric observations by primary beam errors. Significant antenna surface and pointing errors lead to the greatest reduction in fidelity for most cases, but, when present, imaginary beam components dominate the degradation. Beam errors were addressed by optimizing the antenna surfaces and aligning the optics and then determining baseline based primary beams. Methods for applying these measured patterns to actual data were discussed. Pointing errors were reduced by improving the fit to the pointing model. Further reduction was achieved by integrating the use of optical pointing observations into standard radio observing. The greatest benefit was seen during daytime observations, but general reduction in pointing error was seen.
\r\n\r\nThe dense uv-coverage of the Combined Array for Research in Millimeter-wave Astronomy (CARMA) coupled with the techniques described above make it an ideal instrument for imaging extended regions with high fidelity. The NGC 7538 star-forming cloud contains dense peaks, many high-mass stars and associated accretion disks, and multiple outflows. I obtained CARMA images at the requisite fidelity, employing the above techniques. These mosaiced, spectral-line, and 3-mm band continuum observations provide a clearer picture of the bulk morphology of the region and the fine-scale structures within it than has hitherto been possible. For the first time in the region, infall signatures were found towards two sources, allowing comparison of the infall and outflow mass and verifying that significant accretion (>10\u22124M\u2299 yr\u22121) continues well into the stage where a massive protostar has formed. One of the sources, NGC 7538IRS1, shows one of the few definitive signatures of an inverse PCygni profile towards a massive protostar. Three outflows were found centered on sources that are separated by 10,000-20,000 AU in projection. The calculated energy injection rate provides constraints for models of outflow feedback. The NGC 7538 results demonstrate clearly the capability of CARMA to provide high quality images over wide-fields and the benefits of the techniques I developed. While work to improve CARMA image fidelity continues, the program described here lays the groundwork and should help guide further enhancements of image fidelity at CARMA and at other radio facilities.
\r\n" }, { "name": "Brown, Joanna Margaret", "degree": "PhD", "year": "2008", "title": "Childhood to Adolescence: Dust and Gas Clearing in Protoplanetary Disks", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12182007-120046", "creators": [ { "name": { "family": "Brown", "given": "Joanna Margaret" }, "id": "Brown-Joanna-Margaret", "display_name": "Brown, Joanna Margaret" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "co-chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "orcid": "0000-0002-4633-5098", "role": "member", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Steidel", "given": "Charles C." }, "id": "Steidel-C-C", "orcid": "0000-0002-4834-7260", "role": "member", "display_name": "Steidel, Charles C." }, { "name": { "family": "Kamionkowski", "given": "Marc P." }, "id": "Kamionkowski-M-P", "orcid": "0000-0001-7018-2055", "role": "member", "display_name": "Kamionkowski, Marc P." } ], "option_major": [ "astronomy" ], "doi": "10.7907/560K-TZ76", "abstract": "Disks are ubiquitous around young stars. Over time, disks dissipate, revealing planets that formed hidden by their natal dust. Since direct detection of young planets at small orbital radii is currently impossible, other tracers of planet formation must be found. One sign of disk evolution, potentially linked to planet formation, is the opening of a gap or inner hole in the disk. In this thesis, I have identified and characterized several cold disks with large inner gaps but retaining massive primordial outer disks. While cold disks are not common, with ~5% of disks showing signs of inner gaps, they provide proof that at least some disks evolve from the inside-out. These large gaps are equivalent to dust clearing from inside the Earth's orbit to Neptune's orbit or even the inner Kuiper belt. Unlike more evolved systems like our own, the central star is often still accreting and a large outer disk remains.
\r\n\r\nI identified four cold disks in Spitzer 5-40 \u00b5m spectra and modeled these disks using a 2-D radiative transfer code to determine the gap properties. Outer gap radii of 20-45 AU were derived. However, spectrophotometric identification is indirect and model-dependent. To validate this interpretation, I observed three disks with a submillimeter interferometer and obtained the first direct images of the central holes. The images agree well with the gap sizes derived from the spectrophotometry. One system, LkH&alpha 330, has a very steep outer gap edge which seems more consistent with gravitational perturbation rather than gradual processes, such as grain growth and settling. Roughly 70% of cold disks show CO v=1&rarr 0 gas emission from the inner 1 AU and therefore are unlikely to have evolved due to photoevaporation. The derived rotation temperatures are significantly lower for the cold disks than disks without gaps. Unresolved (sub)millimeter photometry shows that cold disks have steeper colors, indicating that they are optically thin at these wavelengths, unlike their classical T Tauri star counterparts. The gaps are cleared of most ~100 \u00b5m sized grains as well as the ~10 \u00b5m sized grains visible in the mid-infrared as silicate emission features.
\r\n" }, { "name": "Enoch, Melissa Lanae", "degree": "PhD", "year": "2008", "title": "Molecular Clouds and Star Formation: A Multiwavelength Study of Perseus, Serpens, and Ophiuchus", "advisor": "Carpenter, John M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06292007-134316", "creators": [ { "name": { "family": "Enoch", "given": "Melissa Lanae" }, "id": "Enoch-Melissa-Lanae", "display_name": "Enoch, Melissa Lanae" } ], "advisors": [ { "name": { "family": "Carpenter", "given": "John M." }, "id": "Carpenter-J-M", "role": "advisor", "display_name": "Carpenter, John M." } ], "committee": [ { "name": { "family": "Scoville", "given": "Nicholas Zabriskie" }, "id": "Scoville-N-Z", "role": "chair", "display_name": "Scoville, Nicholas Zabriskie" }, { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "role": "member", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Carpenter", "given": "John M." }, "id": "Carpenter-J-M", "role": "member", "display_name": "Carpenter, John M." }, { "name": { "family": "Sari", "given": "Re'em" }, "id": "Sari-R", "role": "member", "display_name": "Sari, Re'em" }, { "name": { "family": "Golwala", "given": "Sunil" }, "id": "Golwala-S-R", "role": "member", "display_name": "Golwala, Sunil" } ], "option_major": [ "astrophys" ], "doi": "10.7907/25QK-5K72", "abstract": "In this thesis I utilize large-scale millimeter and mid- to far-infrared surveys to address a number of outstanding questions regarding the formation of low mass stars in molecular clouds. Continuum \u03bb = 1.1 mm maps completed with Bolocam at a resolution of 31\" cover the largest areas observed to date at millimeter or submillimeter wavelengths in three molecular clouds: 7.5 deg\u00b2 in Perseus (140 pc\u00b2 at the adopted distance of d = 250 pc), 10.8 deg\u00b2 (50 pc\u00b2 at d = 125 pc) in Ophiuchus, and 1.5 deg\u00b2 (30 pc\u00b2 at d = 125 pc) in Serpens. These surveys are sensitive to dense substructures with mean density n \u2273 2 - 3 x 10\u2074 cm\u207b\u00b3. A total of 122 cores are detected in Perseus, 44 in Ophiuchus, and 35 in Serpens above mass detection limits of 0.1 - 0.2 Msun. Combining with Spitzer mid- and far-infrared maps from the c2d Legacy program provides wavelength coverage from \u03bb = 1.25-1100 \u03bcm, and enables the assembly of an unbiased, complete sample of the youngest star forming objects in three environments. This sample includes 108 prestellar cores, 43 Class 0 sources and 94 Class I sources.
\r\n\r\nThe approximately equal number of starless cores and embedded protostars in each cloud implies a starless core lifetime of 2 - 4 x 10\u2075 yr, only a few free-fall timescales. This timescale, considerably shorter than the timescale predicted by the classic scenario of magnetic field support in which core evolution is moderated by ambipolar diffusion, suggests that turbulence is the dominant process controlling the formation and evolution of dense cores. However, dense cores in all three clouds are found only at high cloud column densities, where AV\u2273 7 mag, and the fraction of cloud mass in these cores is less than 10%, indicating that magnetic fields must play some role as well. Measured angular deconvolved sizes of the majority of starless cores are consistent with relatively flattened radial density profiles, or with Bonnor-Ebert spheres. The prestellar core mass distribution (CMD) has a slope of \u03b1 = -2.5 \u00b1 0.2 for M > 0.8 Msun, remarkably similar to recent measurements of the slope of the stellar initial mass function: \u03b1 = -2.3 to -2.8. While this result does not rule out the importance of feedback or competitive accretion, it provides support for the hypothesis that stellar masses are determined during the core formation process.
\r\n\r\nThe lifetime of the Class 0 phase is estimated to be 1 - 2 x 10\u2075 yr in Perseus and Serpens, or approximately half that of the Class I phase, arguing against a very rapid early accretion phase. In Ophiuchus the fraction of Class 0 sources is much smaller, consistent with previous measurements of a short (~ 10\u2074 yr) Class 0 phase in that cloud. A large population of low luminosity Class I sources that cannot be explained by constant or monotonically decreasing accretion rates is observed in each cloud. This result strongly suggest that accretion during the Class I phase is episodic, with sources spending approximately 25% of the Class I lifetime in a quiescent state.
\r\n\r\nFinally, I investigate the environmental dependence of star formation by comparing the dense core populations of the three clouds. Cores are found at considerably higher cloud column densities in Ophiuchus than in Perseus or Serpens; more than 75% of cores occur at visual extinctions of AV\u2273 8 mag in Perseus, AV\u2273 15 mag in Serpens, and AV\u2273 20 - 23 mag in Ophiuchus. Cloud CMDs are well characterized by power-law fits above their empirically derived 50% completeness limits, resulting in slopes of \u03b1 = -2.1 \u00b1 0.1 in Perseus, \u03b1 = -2.1 \u00b1 0.3 in Ophiuchus, and \u03b1 = -1.6 \u00b1 0.2 in Serpens. Measured slopes for Perseus and Ophiuchus broadly agree with turbulent fragmentation, but the relative shapes of the observed cloud CMDs are inconsistent with detailed simulations of the dependence of CMD shape on Mach number.
" }, { "name": "Kumar, Shwetank", "degree": "PhD", "year": "2008", "title": "Submillimeter Wave Camera Using A Novel Photon Detector Technology", "advisor": "Zmuidzinas, Jonas", "url": "https://resolver.caltech.edu/CaltechETD:etd-05072008-075138", "creators": [ { "name": { "family": "Kumar", "given": "Shwetank" }, "id": "Kumar-Shwetank", "display_name": "Kumar, Shwetank" } ], "advisors": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "advisor", "display_name": "Zmuidzinas, Jonas" } ], "committee": [ { "name": { "family": "Rutledge", "given": "David B." }, "id": "Rutledge-D-B", "role": "chair", "display_name": "Rutledge, David B." }, { "name": { "family": "Scherer", "given": "Axel" }, "id": "Scherer-A", "role": "member", "display_name": "Scherer, Axel" }, { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "member", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Bockrath", "given": "Marc William" }, "id": "Bockrath-M-W", "role": "member", "display_name": "Bockrath, Marc William" } ], "option_major": [ "appliedphys" ], "doi": "10.7907/F58T-SV45", "abstract": "Cryogenic photon detectors can be used to make extremely sensitive cameras for submillimeter astronomy. Current detector technologies already have sensitivities limited by the noise due to photon arrival statistics. To further improve the sensitivity and mapping speed of experiments for a wide field survey, focal planes containing tens of thousands of pixels are required. Unfortunately, the current technologies use discrete and massive components which are not easy to integrate into large arrays. This thesis presents a 16-pixel, two-color, submillimeter-wave, prototype camera developed at Caltech and the Jet Propulsion Laboratory using a novel photon detector technology. The camera also uses new designs for other constituent elements \u2013 the antenna, transmission line feednetwork, and bandpass filters \u2013 to implement the sub-millimeter pixels. These designs allow integration of the entire camera onto a single chip and conclusively address the problem of scalability while maintaining the sensitivity and noise performance of the current technologies. This thesis explains the design of each of these components and presents the results from experiments conducted to test their performance. Results from the 'first light', obtained by mounting the prototype camera onto the Caltech Submillimeter Observatory (CSO), are also presented.
\r\n\r\nWe have also studied the temperature and power dependence of the resonance frequency, quality factor, and frequency noise of the superconducting niobium thin-film coplanar waveguide (CPW) resonators in order to understand the factors affecting the noise performance of our photon detectors. These experiments were carried out at temperatures well below the superconducting transition (Tc = 9.2 K) in an attempt to understand the source of the excess frequency noise of superconducting resonators which form the sensing element of our photon detectors. The noise decreases by nearly two orders of magnitude as the temperature is increased from 120 to 1200 mK, while the variation of the resonance frequency with temperature over this range agrees well with the standard two-level systems (TLS) model for amorphous dielectrics. These results support the hypothesis that TLS are responsible for the noise in superconducting microresonators and have important implications for resonator applications such as qubits and photon detectors.
\r\n" }, { "name": "Naylor, Bret Justin", "degree": "PhD", "year": "2008", "title": "Broadband Millimeter-Wave Spectroscopy with Z-Spec: An Unbiased Molecular-Line Survey of the Starburst Galaxy M82", "advisor": "Zmuidzinas, Jonas", "url": "https://resolver.caltech.edu/CaltechETD:etd-05282008-104041", "creators": [ { "name": { "family": "Naylor", "given": "Bret Justin" }, "id": "Naylor-Bret-Justin", "display_name": "Naylor, Bret Justin" } ], "advisors": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "advisor", "display_name": "Zmuidzinas, Jonas" } ], "committee": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "chair", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Blain", "given": "Andrew W." }, "id": "Blain-A-W", "role": "member", "display_name": "Blain, Andrew W." }, { "name": { "family": "Politzer", "given": "Hugh David" }, "id": "Politzer-H-D", "role": "member", "display_name": "Politzer, Hugh David" }, { "name": { "family": "Golwala", "given": "Sunil" }, "id": "Golwala-S-R", "role": "member", "display_name": "Golwala, Sunil" }, { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "member", "display_name": "Phillips, Thomas G." } ], "option_major": [ "physics" ], "doi": "10.7907/Y6TP-5E10", "abstract": "Z-Spec is a broadband, millimeter-wave, direct-detection spectrometer based on a novel waveguide grating architecture. It is designed to fully cover the wide one-millimeter atmospheric window with a frequency range of 186 to 307 GHz at a resolution of ~ 250. The design goal is the detection of rotational and fine structure lines from the distant population of galaxies that make up the far-infrared background. Its large instantaneous bandwidth enables detection of multiple transitions of carbon monoxide and a relatively rapid determination of redshift. The grating design is based on the Rowland architecture but is much more compact because of the use of a parallel-plate waveguide propagation medium. Z-Spec uses 160 silicon nitride micromesh bolometers and is cooled to less than 100 mK to achieve background-limited performance. Moreover, Z-Spec serves as a technology demonstration of a technique that is uniquely suited to far-infrared extragalactic spectroscopy from space.
\r\n\r\nZ-Spec's capabilities enable wide-coverage, unbiased line surveys of nearby galaxies. Searches for molecular lines outside our own galaxy have typically been targeted at specific transitions of particular molecules. The brightest sources of extra-galactic molecular lines come from galaxies with physical conditions very different from those found in the Milky Way. Unbiased searches for spectral lines can discover transitions and molecules that are unexpected. A three-pointing study of the prototypical starburst galaxy M82 was performed with Z-Spec at the Caltech Submillimeter Observatory. The survey detected eleven bright lines in the center of the Z-Spec band, of which four had not been previously detected. Two of the new detections are for molecules that had been detected at lower frequencies (HNC 3 - 2 and C2H 3 - 2) and the other two are potentially transitions of SO2, for which only upper limits on lower frequency transitions were previously available. Several detected molecules are analyzed using a large-velocity-gradient (LVG) radiative-transfer model and indicate significant regions of high-density molecular gas along the major axis of M82.
" }, { "name": "Sayers, Jack", "degree": "PhD", "year": "2008", "title": "A Search for Cosmic Microwave Background Anisotropies on Arcminute Scales", "advisor": "Golwala, Sunil", "url": "https://resolver.caltech.edu/CaltechETD:etd-12232007-013248", "creators": [ { "name": { "family": "Sayers", "given": "Jack" }, "id": "Sayers-Jack", "orcid": "0000-0002-8213-3784", "display_name": "Sayers, Jack" } ], "advisors": [ { "name": { "family": "Golwala", "given": "Sunil" }, "id": "Golwala-S-R", "role": "advisor", "display_name": "Golwala, Sunil" } ], "committee": [ { "name": { "family": "Golwala", "given": "Sunil" }, "id": "Golwala-S-R", "role": "chair", "display_name": "Golwala, Sunil" }, { "name": { "family": "Lange", "given": "Andrew E." }, "id": "Lange-A-E", "role": "member", "display_name": "Lange, Andrew E." }, { "name": { "family": "Kamionkowski", "given": "Marc P." }, "id": "Kamionkowski-M-P", "role": "member", "display_name": "Kamionkowski, Marc P." }, { "name": { "family": "Frautschi", "given": "Steven C." }, "id": "Frautschi-S-C", "role": "member", "display_name": "Frautschi, Steven C." } ], "option_major": [ "physics" ], "doi": "10.7907/2Q9Q-JA33", "abstract": "This thesis describes the results of two sets of observations made in 2003 and 2004 using Bolocam from the Caltech Submillimeter Observatory (CSO), along with a description of the design and performance of the instrument. Bolocam is a large format camera consisting of 144 bolometers with an eight arcminute field of view at the CSO, and can be operated non-simultaneously at 1.1, 1.4, or 2.1 mm. All of the data described in this thesis was collected at 2.1 mm, where the individual beams are approximately one arcminute in size. The observations were made over a total of seventy-nine nights, and consisted of surveys of two science fields, Lynx and the Subaru/XMM Deep Field (SDS1), covering a total area of approximately 1 square degree. The noise properties of the maps are extremely uniform, with RMS variations in coverage of approximately 1.5% for twenty arcsecond map pixels. The point source sensitivity of the maps is approximately 100 \u03bcKCMB per beam. Fluctuations in emission from the atmosphere limited the sensitivity of our measurements, and several algorithms designed to remove these fluctuations are described. These algorithms also removed astronomical flux, and simulations were used to determine the effect of this attenuation on a CMB power spectrum. Assuming a flat CMB band power in C\u2113, our data corresponds to an effective angular multipole of \u2113eff = 5700, with a FWHM\u2113 = 2800. At these scales the CMB power spectrum is expected to be dominated by anisotropies induced by the Sunyaev-Zel'dovich effect (SZE), and have a reasonably flat spectrum. Our data is consistent with a band power of C\u2113 = 0 \u03bcK2CMB1, and an upper limit of C\u2113 <\t755 \u03bcK2CMB at a confidence level of 90%. From this result we find that \u03c38 < 1.55 at a confidence level of 90%.\r\n" }, { "name": "Yang, Min", "degree": "PhD", "year": "2007", "title": "Submillimeter Surveys of Galaxy Samples", "advisor": "Phillips, Thomas G.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08012006-120712", "creators": [ { "name": { "family": "Yang", "given": "Min" }, "id": "Yang-Min", "display_name": "Yang, Min" } ], "advisors": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "advisor", "display_name": "Phillips, Thomas G." } ], "committee": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "chair", "display_name": "Phillips, Thomas G." }, { "name": { "family": "Blain", "given": "Andrew W." }, "id": "Blain-A-W", "role": "member", "display_name": "Blain, Andrew W." }, { "name": { "family": "Soifer", "given": "B. Thomas" }, "id": "Soifer-B-T", "role": "member", "display_name": "Soifer, B. Thomas" }, { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "member", "display_name": "Zmuidzinas, Jonas" } ], "option_major": [ "physics" ], "doi": "10.7907/ZTAY-AM05", "abstract": "This thesis aims to gain a better understanding of dusty galaxies by studying the thermal emission of interstellar dust at submillimeter (submm) wavelengths. We conduct 350\u03bcm observations of two galaxy samples selected based on entirely different criteria, using the Submillimeter High Angular Resolution Camera II (SHARC-II, Dowell et al. 2003) at the 10.4m Caltech Submillimeter Observatory (CSO).
\r\n\r\nThe first galaxy sample consists of 18 luminous infrared galaxies (LIGs) in the local Universe (0.003 \u2264 z \u2264 0.042). We estimate the global properties in this galaxy sample; dust temperature (Td = 38.6 \u00b1 7.7 K), emissivity index (\u03b2 = 1.6 \u00b1 0.3), far-infrared (FIR) luminosity (Lfir = 1011.2\u00b10.6 L\u2609}) and dust mass (Md = 107.4\u00b10.6 M\u2609). Guided by theoretical considerations and laboratory measurements, we derive a Td-\u03b2 inverse correlation for the local LIG sample; Td = [5.03 x 109]1/4.46 + \u03b2.
\r\n\r\nThe second galaxy sample consists of 36 ultraluminous infrared galaxies (ULIGs) at moderate redshifts (0.1 < z < 1.0), out of which 28 galaxies are detected. The newly acquired 350\u03bcm data, in combination with the pre-existing IRAS 60\u03bcm and 100\u03bcm data, leads to meaningful estimates of the global properties in these galaxies for the first time; Td = 40.9 \u00b1 6.9K, Lfir = 1012.2\u00b10.5 L\u2609, Md = 108.3\u00b10.3 M\u2609 and intense starburst activity (SFR = 102.5\u00b10.5 L\u2609 yr-1). There is strong circumstantial evidence that the Td-\u03b2 inverse correlation observed in the local LIG sample remains valid in ULIGs at moderate redshifts. We find that the FIR-radio correlation observed in local star-forming galaxies continues to hold for ULIGs over the redshift range of 0.1 < z < 1.0 and dust heating originates predominantly from star formation. Lfir and Td derived for dusty galaxy samples over a wide range of redshifts show significant scatter, due to differing selection biases and variations in dust mass and grain properties. We argue that the observed Td, as a large-scale SED parameter, is linked to the global star formation efficiency (SFE) and the spatial extent characteristic of dominant star formation in a galaxy.
" }, { "name": "Kov\u00e1cs, Attila", "degree": "PhD", "year": "2006", "title": "SHARC-2 350 Micron Observations of Distant Submillimeter Selected Galaxies and Techniques for the Optimal Analysis and Observing of Weak Signals", "advisor": "Phillips, Thomas G.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06022006-123747", "creators": [ { "name": { "family": "Kov\u00e1cs", "given": "Attila" }, "id": "Kov\u00e1cs-Attila", "display_name": "Kov\u00e1cs, Attila" } ], "advisors": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "advisor", "display_name": "Phillips, Thomas G." } ], "committee": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "chair", "display_name": "Phillips, Thomas G." }, { "name": { "family": "Blain", "given": "Andrew W." }, "id": "Blain-A-W", "role": "member", "display_name": "Blain, Andrew W." }, { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "member", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Kamionkowski", "given": "Marc P." }, "id": "Kamionkowski-M-P", "role": "member", "display_name": "Kamionkowski, Marc P." } ], "option_major": [ "physics" ], "doi": "10.7907/8ZM9-6671", "abstract": "New 350 micron data constrain accurately the thermal far-infrared spectral energy distributions (SEDs) for 12 distant submillimeter selected galaxies (SMGs). The results confirm that the linear radio to far-infrared correlation, established for local infrared galaxies, holds out to high redshifts z ~ 1--3. The low correlation constant q ~ 2.14 is more indicative of star formation than AGN-fueled dust heating. The sample exhibits an apparent luminosity--temperature relation (L_FIR ~ T_d^2.89), possibly owing to selection effects. As a result, photometric redshifts in the radio or far-infrared may not be viable, but expressions may relate the observed quantities for current flux and volume limited SMG samples. These suggest that SED estimation may be possible, for objects similarly selected, based on a single radio or far-infrared flux measurement.
\r\n\r\nThe detection of these faint objects (~10 mJy at 350 micron) from the ground is complicated by a bright (~1000 Jy) and highly variable (~10 Jy RMS in 10 minutes of integration) atmosphere with a 1/f^2 noise spectrum and by instrumental 1/f noise. To reach optimum sensitivities, a careful analysis of the data is required, and well-chosen observing strategies are helpful. The principal techniques that aid the extraction of weak signals from colored noise are presented. Close to optimal analysis is implemented effectively by the CRUSH software. Both the computing and storage requirement of the implementation scales linearly with the size of the data set, making this approach superior to the computationally expensive alternatives for handling the very large data volumes expected from future instruments.
" }, { "name": "Widicus Weaver, Susanna Leigh", "degree": "PhD", "year": "2005", "title": "Rotational Spectroscopy and Observational Astronomy of Prebiotic Molecules", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05162005-153745", "creators": [ { "name": { "family": "Widicus Weaver", "given": "Susanna Leigh" }, "id": "WidicusWeaver-Susanna-Leigh", "orcid": "0000-0001-6015-3429", "display_name": "Widicus Weaver, Susanna Leigh" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Beauchamp", "given": "Jesse L." }, "id": "Beauchamp-J-L", "orcid": "0000-0001-8839-4822", "role": "chair", "display_name": "Beauchamp, Jesse L." }, { "name": { "family": "Collier", "given": "C. Patrick" }, "id": "Collier-C-P", "orcid": "0000-0002-8198-793X", "role": "member", "display_name": "Collier, C. Patrick" }, { "name": { "family": "Rees", "given": "Douglas C." }, "id": "Rees-D-C", "orcid": "0000-0003-4073-1185", "role": "member", "display_name": "Rees, Douglas C." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "chemistry" ], "doi": "10.7907/CN1R-H437", "abstract": "It is now widely believed that prebiotic molecules were delivered to the early Earth by planetesimals and their associated interplanetary dust particles. Yet the formation pathways for these molecules are not clear. Amino acids and sugars have been found in carbonaceous chondrites, but only much simpler species have been detected in the interstellar medium (ISM). Prebiotic organics could have formed in the ISM and been directly incorporated into planetesimals, or simpler species could have formed in the ISM and then been incorporated into planetesimals, undergone further processing, and been delivered to Earth. Limits on interstellar chemistry must therefore be established through observational astronomy before potential prebiotic formation pathways can be assessed. These observations require laboratory spectroscopic investigation of the species of interest.
\r\n\r\nThis thesis is an interdisciplinary study involving laboratory rotational spectroscopy and astronomical observations of several key prebiotic molecules. The laboratory work has focused on obtaining the rotational spectra of the simplest three-carbon ketose sugar, 1,3-dihydroxyacetone, and its structural isomers methyl glycolate and dimethyl carbonate, as well as aminoethanol, the predicted interstellar precursor to alanine. The pure rotational spectral analysis of the low-lying torsional states of the simplest alpha-hydroxy aldehyde, glycolaldehyde, has also been completed. The original Balle-Flygare Fourier transform microwave spectrometer was used to obtain the microwave spectra, while both the Jet Propulsion Laboratory and Caltech direct absorption flow cell spectrometers were used for additional direct absorption millimeter and submillimeter studies.
\r\n\r\nThe results of these laboratory experiments were used to guide observational searches with the Caltech Submillimeter Observatory, the Owens Valley Millimeter Array, and the Green Bank Telescope toward the hot core sources Sgr B2(N-LMH), Orion Hot Core/Compact Ridge, and W51 e1/e2. Evidence has been found for the presence of dihydroxyacetone and methyl glycolate in Sgr B2(N-LMH).
\r\n\r\nThese results have important implications for interstellar grain surface chemistry, and proposed additions to grain surface chemical models are also discussed. Reactions involving surface radicals and molecules containing carbonyl groups can efficiently compete with the simple grain surface reactions included in previous models. Such aldehyde abstraction reactions should be considered as pathways to complex carbonyl-containing species on interstellar grain surfaces.
" }, { "name": "Edgington, Samantha Faye", "degree": "PhD", "year": "2004", "title": "A Galaxy Cluster Survey Using the Sunyaev Zel\u2019dovich Effect", "advisor": "Lange, Andrew E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09272003-154928", "creators": [ { "name": { "family": "Edgington", "given": "Samantha Faye" }, "id": "Edgington-Samantha-Faye", "display_name": "Edgington, Samantha Faye" } ], "advisors": [ { "name": { "family": "Lange", "given": "Andrew E." }, "id": "Lange-A-E", "role": "advisor", "display_name": "Lange, Andrew E." } ], "committee": [ { "name": { "family": "Lange", "given": "Andrew E." }, "id": "Lange-A-E", "role": "chair", "display_name": "Lange, Andrew E." }, { "name": { "family": "Harrison", "given": "Fiona A." }, "id": "Harrison-F-A", "role": "member", "display_name": "Harrison, Fiona A." }, { "name": { "family": "Kamionkowski", "given": "Marc P." }, "id": "Kamionkowski-M-P", "role": "member", "display_name": "Kamionkowski, Marc P." }, { "name": { "family": "Scoville", "given": "Nicholas Zabriskie" }, "id": "Scoville-N-Z", "role": "member", "display_name": "Scoville, Nicholas Zabriskie" } ], "option_major": [ "physics" ], "doi": "10.7907/DVS1-3590", "abstract": "This thesis describes the design and observations with the Bolocam instrument. Bolocam is a 144-element bolometer array designed to detect the Sunyaev Zel'dovich effect, used at the Caltech Submillimeter Observatory. Bolocam can be configured to observe at 1.1, 1.4, and 2.1 mm. We conducted a galaxy cluster survey at 2.1 mm, where clusters are detected as decrements against the Cosmic Microwave Background. The survey consisted of two blank fields, for a total of one square degree of coverage. We took advantage of the array configuration of the Bolocam focal plane to remove the atmospheric noise from the time stream before mapping the data. The sky noise removal left residual 1/f noise from the atmosphere in the data, and the resulting map sensitivity is limited by this noise. After filtering the maps to detect clusters with a FWHM of 2 arc minutes the RMS of the first map is 148.5 micro-Kelvin, and the second is 77.8 micro-Kelvin. The difference is due to a difference in integration time on the two maps. Bolocam detected 2 4-sigma decrements in the two filtered 1/2 x 1 degree maps. Bolocam also places an upper limit on the CMB angular power spectrum at l = 6000 of delta T < 49 micro-Kelvin.\r\n" }, { "name": "Kessler, Jacqueline Elizabeth", "degree": "PhD", "year": "2004", "title": "Gas and Dust Chemistry in Planet-Forming Disks", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10222003-092836", "creators": [ { "name": { "family": "Kessler", "given": "Jacqueline Elizabeth" }, "id": "Kessler-Jacqueline-Elizabeth", "display_name": "Kessler, Jacqueline Elizabeth" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "orcid": "0000-0001-6874-1137", "role": "chair", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Gray", "given": "Harry B." }, "id": "Gray-H-B", "orcid": "0000-0002-7937-7876", "role": "member", "display_name": "Gray, Harry B." }, { "name": { "family": "Marcus", "given": "Rudolph A." }, "id": "Marcus-R-A", "orcid": "0000-0001-6547-1469", "role": "member", "display_name": "Marcus, Rudolph A." } ], "option_major": [ "chemistry" ], "doi": "10.7907/MGC6-WR47", "abstract": "As analogs to the solar nebula, circumstellar disks offer a unique opportunity to study the conditions during the star and planet formation process. Interpretation of molecular line observations is dependent on the development of extensive models of the chemistry and radiative transfer in accretion disks. In this study, several millimeter-wave molecular lines were observed toward a sample of disks encircling T Tauri and Herbig Ae stars with the Owens Valley Millimeter Array. The intent of these studies is the quantitative examination of the chemistry of the biogenic elements (C, N, O, S) in accretion disks. Toward this goal, radiative transfer models were modified for direct comparison with the observations to aid in the interpretation of molecular line emission and comparison with the predictions of chemical models, as discussed in Chapter 2. Chapter 3 presents a survey of CN, HCN, CO and HCO+ in 7 Herbig Ae and T Tauri star disks, which was performed in order to probe the effects of UV fields on disk chemistry. In this study, CN and HCO+ are found to be sensitive to the strength of the local UV field. The first interferometric studies of deuterium in disks were performed and are discussed in Chapter 4. HDO and DCN were detected toward the T Tauri disk LkCa 15 and the Herbig Ae disk HD 163296. The deuterium enrichments are similar to that of molecular clouds, hot cores, and comets, consistent with comet formation in the outer regions of disks. The distribution of HDO in LkCa 15 was found to be similar to predictions from chemical models, which suggest a steep gradient as a function of disk radius. Chapter 5 presents Keck LWS observations of the 8-13 micron silicate emission feature toward several T Tauri and Herbig Ae stars at various stages of the star formation process indicate an evolutionary trend similar to that previously seen with ISO for disks around intermediate mass stars. However, emission from crystalline silicates was only detected toward one low mass star, Hen 3-600A, possibly indicating that crystallization processes occur less frequently, or are more difficult to observe at mid-infrared wavelengths, in these disks. Finally, in Chapter 6, a summary of protoplanetary disk chemistry is presented and the future of the field is discussed." }, { "name": "Ward, John Strawn", "degree": "PhD", "year": "2002", "title": "Observations of Carbon Monoxide in the Starburst Galaxy M82 with a 690 GHz Wide Spectral Bandwidth Receiver", "advisor": "Zmuidzinas, Jonas", "url": "https://resolver.caltech.edu/CaltechETD:etd-01112002-085240", "creators": [ { "name": { "family": "Ward", "given": "John Strawn" }, "id": "Ward-John-Strawn", "display_name": "Ward, John Strawn" } ], "advisors": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "advisor", "display_name": "Zmuidzinas, Jonas" } ], "committee": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "chair", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Kamionkowski", "given": "Marc P." }, "id": "Kamionkowski-M-P", "orcid": "0000-0001-7018-2055", "role": "member", "display_name": "Kamionkowski, Marc P." }, { "name": { "family": "Scoville", "given": "Nicholas Zabriskie" }, "id": "Scoville-N-Z", "orcid": "0000-0002-0438-3323", "role": "member", "display_name": "Scoville, Nicholas Zabriskie" }, { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "member", "display_name": "Phillips, Thomas G." } ], "option_major": [ "physics" ], "doi": "10.7907/5S4X-NV83", "abstract": "A 690 GHz wide spectral bandwidth heterodyne receiver was developed to observe the J=6-5 rotational emission line of carbon monoxide (CO) in extragalactic sources. This receiver is based on a niobium superconductor-insulator-superconductor (SIS) mixer with a twin-slot antenna in a superconducting NbTiN ground plane. A 4-8 GHz low-noise amplifier was developed to amplify the intermediate frequency (IF) signal from the mixer with a spectral bandwidth of 1,700 km/s, enough to comfortably observe the entire emission line of the broadest extragalactic submillimeter sources with a single receiver tuning. This amplifier is a quasi-monolithic microwave integrated circuit (QMMIC); three 160 micron gate InP high-electron-mobility transistors (HEMTs) were bump-bonded to a thin-film GaAs substrate containing passive tuning and DC bias circuitry. The measured amplifier gain is 32 dB and the noise is approximately 8 Kelvin from 4 to 8 GHz at a physical temperature of 4 Kelvin. The complete receiver achieves a measured uncorrected double-sideband noise temperature of 180 Kelvin.
\r\n\r\nPrior to this development effort, a versatile microwave simulation package was written to calculate and optimize the signal and noise performance of high-frequency circuits, especially those containing superconductors and superconducting tunnel junctions. Using this package, called SuperMix, C++ programs can be written to simulate and optimize circuits of arbitrary size, complexity, and topology. SuperMix was used to simulate the complete 690 GHz SIS receiver.
\r\n\r\nThe receiver was used at the Caltech Submillimeter Observatory (CSO) to map the 12CO J=6-5 emission line in the central kiloparsec of the nearby starburst galaxy M82 at a resolution of 14 arc seconds. Hot spots were found on either side of the dynamical center. A novel deconvolution technique was used to compute a 12CO J=6-5 / 12CO J=2-1 line ratio map based on high-resolution J=2-1 interferometer data. The 12CO J=6-5 map, along with observations of 12CO J=4-3, 12CO J=3-2, 13CO J=3-2, an upper limit for 13CO J=6-5, and five other measured CO lines from the literature, were analyzed in the context of a two-component large velocity gradient (LVG) excitation model. Likelihood curves were calculated for each of the model parameters as well as a variety of related physical quantities for the two hot spots based on the measured line intensities and their associated uncertainties. This approach reveals in an unbiased way how well various quantities can be constrained by the CO observations. The results of this analysis suggest that the warm gas is less dense than the cool gas, and that over half of the total molecular gas mass in these nuclear regions is warmer than 50 K.
" }, { "name": "Chattopadhyay, Goutam", "degree": "PhD", "year": "2000", "title": "Dual polarized and balanced receivers at millimeter and submillimeter wavelengths", "advisor": "Zmuidzinas, Jonas", "url": "https://resolver.caltech.edu/CaltechETD:etd-02032004-163517", "creators": [ { "name": { "family": "Chattopadhyay", "given": "Goutam" }, "id": "Chattopadhyay-Goutam", "orcid": "0000-0001-7942-5025", "display_name": "Chattopadhyay, Goutam" } ], "advisors": [ { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "advisor", "display_name": "Zmuidzinas, Jonas" } ], "committee": [ { "name": { "family": "Rutledge", "given": "David B." }, "id": "Rutledge-D-B", "role": "chair", "display_name": "Rutledge, David B." }, { "name": { "family": "Zmuidzinas", "given": "Jonas" }, "id": "Zmuidzinas-J", "role": "co-chair", "display_name": "Zmuidzinas, Jonas" }, { "name": { "family": "Hajimiri", "given": "Ali" }, "id": "Hajimiri-A", "role": "member", "display_name": "Hajimiri, Ali" }, { "name": { "family": "Carlstrom", "given": "John E." }, "id": "Carlstrom-J-E", "role": "member", "display_name": "Carlstrom, John E." }, { "name": { "family": "Weinreb", "given": "Sander" }, "id": "Weinreb-S", "role": "member", "display_name": "Weinreb, Sander" } ], "option_major": [ "eleceng" ], "doi": "10.7907/RMVX-0619", "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." }, { "name": "Benford, Dominic James", "degree": "PhD", "year": "1999", "title": "Broadband submillimeter instrumentation for the detection of distant galaxies", "advisor": "Phillips, Thomas G.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06092008-100026", "creators": [ { "name": { "family": "Benford", "given": "Dominic James" }, "id": "Benford-D-J", "display_name": "Benford, Dominic James" } ], "advisors": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "advisor", "display_name": "Phillips, Thomas G." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "astrophys" ], "doi": "10.7907/7eha-q373", "abstract": "This research details my efforts to search the universe for the faint far-infrared emission of galaxies as far away as possible. I first describe the design, construction, use, and performance evaluation of the Submillimeter High Angular Resolution Camera (SHARC), a 24-element bolometer camera for imaging at 350 microns and 450 microns from the Caltech Submillimeter Observatory (CSO). This instrument achieves background-limited performance and has been available for use by the international community since 1996.\r\n\r\nIn the following two chapters, I detail the astronomical results attained with this instrument when used to observe the thermal dust emission from a sample of nearby galaxies (chapter 3) and a sample of sources as distant as 90% of the way across the spacetime universe (chapter 4). The nearby sample is well-characterized by a single-component greybody dust emission model with a temperature of 37 +/- 4K and a spectral emissivity index of beta = 1.7 +/- 0.4. Our cosmologically distant sample provides the first systematic study of these objects at wavelengths probing near the emission peak at a rest-frame wavelength of approximately 80 microns. We find an average temperature of 53 +/- 8K and determine a median luminosity of (2 +/- 1)x10^13 L_sun and a median dust mass of (3 +/- 2)x10^8 M_sun. This makes these objects some of the most massive and luminous ever observed, with an inferred star formation rate of 2000 M_sun per year.\r\n\r\nTo balance the continuum emission results described above, I have observed both local and high-redshift galaxies with the CSO facility heterodyne receivers in an effort to detect the emission lines of CO, Cii, and Nii. We have observed a sample of 22 nearby (0.02 < z < 0.13) ultraluminous infrared galaxies in the J = 2 to 1 and J = 3 to 2 transitions of CO. Using published 1 to 0 intensities, we find that the 3 to 2 emission most likely arises from an optically thick region, implying that future observations in the higher-J lines can be used to constrain the temperature of the molecular gas in these galaxies. We find a most likely temperature in the range 20 < T < 60K and a molecular gas density of n(H2) [approx] 1500 cm^-3. At high redshifts (z > 2), however, most of our observations have resulted in nondetections, but not without merit. The emission in the Nii 205 micron line from the Cloverleaf quasar is found to be below the amount predicted for a galaxy similar to M82. For two z > 4 quasars, our upper limits to the Cii 158 micron line emission show that the ratio of the line luminosity to the total luminosity is less than 0.01%, ten times smaller than has been observed locally.\r\n\r\nFinally, I shall detail our effort to design a novel submillimeter spectrometer using a linear bolometer array as a detector element and relying on Fabry-Perot or immersed grating optics to provide the spectral dispersion. This approach promises to provide bandwidths several times larger than are available with existing heterodyne spectrometers, making the detection of cosmologically distant galaxies in their submillimeter line emission a reality." }, { "name": "Bin, Mei", "degree": "PhD", "year": "1997", "title": "Low-noise THz Niobium SIS Mixers", "advisor": "Phillips, Thomas G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07172014-124951267", "creators": [ { "name": { "family": "Bin", "given": "Mei" }, "id": "Bin-Mei", "display_name": "Bin, Mei" } ], "advisors": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "advisor", "display_name": "Phillips, Thomas G." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "physics" ], "doi": "10.7907/AZYZ-XP41", "abstract": "This thesis describes the development of low-noise heterodyne receivers at THz frequencies for submillimeter astronomy using Nb-based superconductor-insulator-superconductor (SIS) tunneling junctions. The mixers utilize a quasi-optical configuration which consists of a planar twin-slot antenna and antisymmetrically-fed two-junctions on an antireflection-coated silicon hyperhemispherical lens. On-chip integrated tuning circuits, in the form of microstrip lines, are used to obtain maximum coupling efficiency in the designed frequency band. To reduce the rf losses in the integrated tuning circuits above the superconducting Nb gap frequency (~ 700 GHz), normal-metal Al is used to replace Nb as the tuning circuits.
\r\n\r\nTo account the rf losses in the micros trip lines, we calculated the surface impedance of the AI films using the nonlocal anomalous skin effect for finite thickness films. Nb films were calculated using the Mattis-Bardeen theory in the extreme anomalous limit. Our calculations show that the losses of the Al and Nb microstrip lines are about equal at 830 GHz. For Al-wiring and Nb-wiring mixers both optimized at 1050 GHz, the RF coupling efficiency of Al-wiring mixer is higher than that of Nb-wiring one by almost 50%. We have designed both Nb-wiring and Al-wiring mixers below and above the gap frequency.
\r\n\r\nA Fourier transform spectrometer (FTS) has been constructed especially for the study of the frequency response of SIS receivers. This FTS features large aperture size (10 inch) and high frequency resolution (114 MHz). The FTS spectra, obtained using the SIS receivers as direct detectors on the FTS, agree quite well with our theoretical simulations. We have also, for the first time, measured the FTS heterodyne response of an SIS mixer at sufficiently high resolution to resolve the LO and the sidebands. Heterodyne measurements of our SIS receivers with Nb-wiring or Al-wiring have yielded results which arc among the best reported to date for broadband heterodyne receivers. The Nb-wiring mixers, covering 400 - 850 GHz band with four separate fixed-tuned mixers, have uncorrected DSB receiver noise temperature around 5hv/kb to 700 GHz, and better than 540 K at 808 GHz. An Al-wiring mixer designed for 1050 GHz band has an uncorrected DSB receiver noise temperature 840 K at 1042 GHz and 2.5 K bath temperature. Mixer performance analysis shows that Nb junctions can work well up to twice the gap frequency and the major cause of loss above the gap frequency is the rf losses in the microstrip tuning structures. Further advances in THz SIS mixers may be possible using circuits fabricated with higher-gap superconductors such as NbN. However, this will require high-quality films with low RF surface resistance at THz frequencies.
" }, { "name": "Grossman, Erich Nathan", "degree": "PhD", "year": "1988", "title": "A Far-Infrared Heterodyne Spectrometer for Airborne Astronomy", "advisor": "Phillips, Thomas G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01222013-150156111", "creators": [ { "name": { "family": "Grossman", "given": "Erich Nathan" }, "id": "Grossman-Erich-Nathan", "display_name": "Grossman, Erich Nathan" } ], "advisors": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "advisor", "display_name": "Phillips, Thomas G." } ], "committee": [ { "name": { "family": "Phillips", "given": "Thomas G." }, "id": "Phillips-T-G", "role": "chair", "display_name": "Phillips, Thomas G." }, { "name": { "family": "Cross", "given": "Michael Clifford" }, "id": "Cross-M-C", "role": "member", "display_name": "Cross, Michael Clifford" }, { "name": { "family": "Rutledge", "given": "David B." }, "id": "Rutledge-D-B", "role": "member", "display_name": "Rutledge, David B." }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "physics" ], "doi": "10.7907/79cv-bm83", "abstract": "The design and construction of a novel heterodyne spectrometer for airborne astronomy in the 50 \u00b5m - 200 \u00b5m wavelength range is described. along with laboratory measurements of its performance. A bulk, extrinsic Ge:Ga photoconductor is used as the mixer. Its low bandwidth, determined by the hole recombination rate, necessitates the use of a continuously tunable local oscillator. This is provided by a far-infrared laser sideband generator, which is based on a GaAs Schottky diode mounted at the feed of a comer-cube antenna, the latter combination acting as a reflective FIR modulator.
\r\n\r\nThe first chapter of this thesis describes the astronomical and technical context of the project - in particular, the constraints which the astronomical goals set on the instrument, and the advantages and drawbacks of each of the various broad instrumental strategies that are available for spectrometer design. The chapter's last section provides a very brief overview of our most successful laboratory results, which are described at greater length in chapters 2- 4. In chapter two we describe the performance of Ge:Ga mixers as heterodyne mixers. We report on an extensive series of measurements of bandwidth, photoconductive gain, and direct detection responsivity for a series of highly compensated, NTD detectors grown specifically for this purpose. Chapter two also describes a nunber of experiments on FIR heterodyne performance, made using the direct, attenuated laser, rather than the output of the sideband generator, as the local oscillator. These confirm the expectation that germanium photoconductors are capable of quantum-limited noise performance with quantum efficiencies of ~10%, at much lower LO powers than required for Schottky diodes. Our best achieved noise temperature is TN(DSB) = 655K at PLO = 1.6\u00b5W, a factor of > 25 lower than the best reported corresponding figure for Schottky diodes.
\r\n\r\nChapter 3 describes the operating principles and construction of our FIR laser, which formed a basic tool in nearly all our laboratory experiments. A brief discussion of the Lorenz instability in FIR lasers is also given, in connection with various observations we have made of spontaneous pulsations and excess low-frequency noise on the laser output, and which have recently been the subject of considerable study by other researchers. Chapter four describes FIR laser sideband generation using small-area Schottky diodes and comer-cube antennas. The construction and performance of our corner-cubes is outlined, including the first direct measurement of the main beam efficiency of a corner-cube antenna in the FIR, and a comparison with theory. The construction and measured performance of the rest of the sideband generator is also described. A detailed, quantitative model has been developed for the conversion efficiency obtainable from Schottky diodes in this application. We find that the low conversion efficiency (-39 db) measured in our experiments, and comparable to that found by other researchers, is inherent in the diode and well predicted by the model. For our particular experiment, the model predicts -28 db loss due to the diode, plus approximately -10 db loss due to the antenna coupling efficiency. The dependence of conversion efficiency on diode parameters is studied and guidelines for future optimization derived. Unfortunately, the severe conversion loss we measure, combined with low FIR laser power and (somewhat less significantly) poor optics transmission, leads to our presently available LO power being inadequate to obtain astronomically useful sensitivity, by a large factor.
" } ]