The successful detection and characterization of the B-modes in the Cosmic Microwave Background (CMB) would dramatically illuminate the physics of the inflationary era. The Observational Cosmology Group is iterating on bolometers in an attempt to detect this signal. The previous detector design became unstable in parts of its transition when adjusted for 220/270 GHz frequencies, limiting its use.
\n \nWe study the mechanism of instability in these transition edge sensor (TES) bolometers used for ground based observations of the Cosmic Microwave Background (CMB) at 270GHz. The instability limits the range of useful operating resistances of the TES down to ≈50% of the TES normal resistance (R_n), and due to variations in detector properties and optical loading within a column of multiplexed detectors, limits the effective on sky yield to ≈67 %.
\n\nThrough comparison of 7 new detector thermal capacity designs and measurements of the electrical impedance of the detectors, we show the instability is due to the increased bolometer leg G for higher-frequency detection inducing decoupling of the palladium-gold heat capacity from the thermistor. We demonstrate experimentally that the limiting thermal resistance is due to the small cross sectional area of the silicon nitride bolometer island, and so is easily fixed by layering palladium-gold over an oxide protected TES. The resulting detectors can be biased down to a resistance ≈10% of Rn, improving the effective on-sky yield to ≈93%.
\n\nWe also investigate a possibly related, unexpected slope in the Aluminum calibration TES transition and determine that it is not due to phase separation, even accounting for the science TES thermal instability.
\n", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10637, title ="Simulation Pipeline for Velocity Field Measurements\nusing the Kinetic Sunyaev-Zel'dovich Effect", author = "Su, Yubo", month = "January", year = "2016", doi = "10.7907/727E-BW81", url = "https://resolver.caltech.edu/CaltechTHESIS:01102018-113943698", revision_no = "19", abstract = "The kinetic Sunyaev-Zel 'dovich (kSZ) effect is of great cosmological interest for\nproviding precision measurements of peculiar velocity fields independent of systematics\npresent in other cosmological probes. The high precision kSZ measurements\non the horizon are expected to yield valuable constraints distinguishing between\ncompeting cosmological models. Instrumental to kSZ astromony is the removal of\ncontaminating point sources, primarily radio and dusty, star-forming galaxies that\nhave bright emissions in kSZ spectral bands. As the precision of measurements\nimprove, the source removal residuals may become significant contributions to the\noverall kSZ error budget. A full simulation is essential to characterizing these induced\nerrors. This study develops a procedure for contamination removal from first\nprinciples, verifying its optimality against information theoretic limits. Models for\ncontaminating sources of increasing complexity are considered, at each step characterizing\nthe optimality of the subtraction compared to theoretical bounds. The final,\ncurrently unfinished objective is to apply this subtraction procedure to a realistic\nsource distribution and understand the incurred systematics.", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10636, title ="Design Considerations to Improving Sensitivity in Superspec: an Onchip KID-Based, Mm-Wave Spectrometer", author = "Shiu, Corwin", month = "January", year = "2015", doi = "10.7907/0XPB-W756", url = "https://resolver.caltech.edu/CaltechTHESIS:01102018-113534206", revision_no = "19", abstract = "SuperSpec is an ultra-compact on-chip spectrometer for mm/submm astronomy. SuperSpec's compact size\nand wide spectral bandwidth will be uniquely powerful to perform multi-object spectroscopy for high redshift\nsurveys, and for tomographic studies of the epoch of reionization (EoR). SuperSpec employs the use of kinetic\ninductance detectors (KID) to build highly multiplexed arrays. A full instrument of~ 500 channels can be\nlithographed on a few cm2 of silicon.
\n\nIn this thesis, we explored electromagnetic designs to improve sensitivity of KIDs. We show that we can\nreliably remove up to 753 of the current design's inductor volume to obtain improvements in sensitivities\nup a factor of four. We also explored two filter designs that can deliver higher power to the detectors. Our\nhalf-wave transmission line filters can only deliver up to 503 of power to the detectors. Both ring resonators\nand backshorted detectors can deliver unity power, however we found that the large coupling length needed\nin order to properly use ring resonators would be impractical in a. filterba.nk. Lastly we explored different\nfilterbank designs. Multiple detectors read out together in a single channel has higher resolving power\nthan single detector channels. Backshorted detectors offer higher resolving power than two paired detector\nchannels, but under-performs three or more paired detector channels.
", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/9019, title ="The Atmospheric Dynamics of Pulsar Companions", author = "Jermyn, Adam Sean", month = "January", year = "2015", doi = "10.7907/Z90Z716M", url = "https://resolver.caltech.edu/CaltechTHESIS:06112015-211414622", revision_no = "29", abstract = "Pulsars emit radiation over an extremely wide frequency range, from radio through gamma. Recently, systems in which this radiation significantly alters the atmospheres of low-mass pulsar companions have been discovered. These systems, ranging from ones with highly anisotropic heating to those with transient X-ray emissions, represent an exciting opportunity to investigate pulsars through the changes they induce in their companions. In this work, we present both analytic and numerical work investigating these phenomena, with a particular focus on atmospheric heat transport, transient phenomena, and the possibility of deep heating via gamma rays. We find that certain classes of binary systems may explain decadal-timescale X-ray transient phenomena, as well as the formation of so-called redback companion systems. We also posit an explanation for the formation of high-eccentricity millisecond pulsars with white dwarf companions. In addition, we examine the temperature anisotropy induced by the Pulsar in its companion, and demonstrate that this may be used to infer properties of both the companion and the Pulsar wind. Finally, we explore the possibility of spontaneously generated banded winds in rapidly rotating convecting objects.
", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/8487, title ="How Far from Jerusalem? Tropical Customs and the Question of Race in the Book of John Mandeville", author = "Mukherjee, Eric S.", month = "January", year = "2014", doi = "10.7907/6WP5-V229", url = "https://resolver.caltech.edu/CaltechTHESIS:06052014-141341323", revision_no = "25", abstract = "The Book of John Mandeville, while ostensibly a pilgrimage guide documenting an English knight’s journey into the East, is an ideal text in which to study the developing concept of race in the European Middle Ages. The Mandeville-author’s sense of place and morality are inextricably linked to each other: Jerusalem is the center of his world, which necessarily forces Africa and Asia to occupy the spiritual periphery. Most inhabitants of Mandeville’s landscapes are not monsters in the physical sense, but at once startlingly human and irreconcilably alien in their customs. Their religious heresies, disordered sexual appetites, and monstrous acts of cannibalism label them as fallen state of the European Christian self. Mandeville’s monstrosities lie not in the fantastical, but the disturbingly familiar, coupling recognizable humans with a miscarriage of natural law. In using real people to illustrate the moral degeneracy of the tropics, Mandeville’s ethnography helps shed light on the missing link between medieval monsters and modern race theory.", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10700, title ="Measurement, Simulation, and Design of the Dispersion-Engineered Traveling-Wave Kinetic Inductance Amplifier", author = "Chaudhuri, Saptarshi", month = "January", year = "2013", doi = "10.7907/KTZD-SQ44", url = "https://resolver.caltech.edu/CaltechTHESIS:02132018-103954976", revision_no = "15", abstract = "Recently, Eom et al. [1 J proposed a new concept for a low-noise cryogenic amplifier known\nas a Dispersion-Engineered Traveling-Wave Kinetic Inductance (DTWKI) amplifier. This\ndevice exploits the nonlinear kinetic inductance of superconducting thin-film nitrides to\nachieve high gain-bandwidth, near quantum-limited noise, and excellent dynamic range. In\nthis thesis, we describe recent progress toward an experimental realization of the DTWKI; in\nparticular, we focus on improvements in the areas of gain-bandwidth and noise performance.\nWe describe a numerical model of the amplifier, and use this model to interpret experimental\nresults and provide insight into the effects of dispersion-engineering on gain processes.\nLastly, based on experimental results and model output, we propose some improvements to\nthe DTWKI device.", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10708, title ="A Ku-Band Polarimeter for the Owens Valley Radio Observatory 40-Meter Telescope", author = "Karkare, Kirit Sukrit", month = "January", year = "2011", doi = "10.7907/AX7Y-QF79", url = "https://resolver.caltech.edu/CaltechTHESIS:02132018-113613816", revision_no = "18", abstract = "Blazars are active galactic nuclei - small, extremely luminous objects at the center of galaxies powered by material accreting around a supermassive black hole - which emit relativistic jets of\nhighly energetic plasma along our line of sight. There is no accepted model for jet composition, acceleration, and confinement; observations at different wavelengths will help us understand these\nemission mechanisms. Since 2007, the 40-Meter Telescope at the Owens Valley Radio Observatory has been monitoring over 1100 blazars every two days. The variability in radio light curves is\nlikely to be correlated with gamma-rays, which we are observing with the Fermi Gamma-Ray Space Telescope.
\n\nA new Ku-band receiver for the 40-Meter Telescope is in development. It will offer increased sensitivity, MHz spectral resolution from 12-18 GHz, and calculation of Stokes I, Q, and U parameters.\nIn this thesis, I present the design, assembly, and testing of various components in the receiver chain. I evaluate the suitability of a commercial radio frequency over optical link for use in the receiver,\ndescribe the fabrication and verification of bandpass filters and sideband separating modules, and present the design and testing of a digital back end spectrometer which uses field-programmable\ngate array devices.
\n\nWhen complete in late 2011 , the new receiver will allow the continuation of the blazar monitoring program with the addition of spectral and polarization information, which will be invaluable in\nunderstanding blazar jet emission.
", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10696, title ="The Importance of Compact-Object Spin in Extreme and Intermediate-Mass Ratio Inspirals", author = "Binder, Gary Allen", month = "January", year = "2011", doi = "10.7907/J75G-J007", url = "https://resolver.caltech.edu/CaltechTHESIS:02122018-170647583", revision_no = "19", abstract = "Gravitational waves can be produced when a compact object (stellar-mass black hole, neutron star, or white dwarf) spirals towards a massive black hole. For moderate mass ratios of 10-2 - 10-4, these events are known as intermediate mass ratio inspirals (IMRis), whereas for mass ratios below 10-4 they are called extreme mass ratio inspirals (EMRis). These events will be important sources for the proposed gravitational-wave detector LISA (Laser Interferometer Space Antenna) and will provide a precise test\nof general relativity in the unexplored regime of strong gravitational fields. To detect\nthese gravitational waves and reliably measure the parameters of the binary producing\nthem, highly accurate models of gravitational waveforms are needed. The spin of the\norbiting compact object (CO) introduces forces that affect the orbit and waveform,\nbut these effects are often ignored. The goal of this thesis is to determine under what\ncircumstances compact-object spin will significantly alter the waveform as measured\nby LISA. To do this, a post-Newtonian waveform model will be used to explore CO\nspin effects. It is concluded that neglecting CO spin does not effect the detectability\nof EMRis or IMRis. Parameter measurement errors introduced by neglecting CO\nspin are typically small unless the binary system happens to be particularly close.\nConstraining the value of compact object spin is unlikely but may be possible for a\nnearby IMRI. Within the approximations used in this study, it appears CO spin is\nmarginally important, but that conclusion may change if a more realistic waveform\nmodel is used in future work. ", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10701, title ="Laser Offset Stabilization for Broadly Tunable TeraHertz (THz) Frequency Generation", author = "Cossel, Kevin", month = "January", year = "2007", doi = "10.7907/S7V2-JJ56", url = "https://resolver.caltech.edu/CaltechTHESIS:02132018-104318011", revision_no = "19", abstract = "Spectroscopy and imaging in the terahertz region promises to be useful for a wide variety of\napplications. For remote sensing, terahertz spectroscopy could help in the identification of\nexplosives and narcotics. In astronomy, terahertz imaging should provide new information about\nthe composition of the interstellar medium and about the processes by which stars and planets\nare born. In chemistry and molecular biology, terahertz spectroscopy provides new rotational or\nrovibrational spectra of molecules and is useful in the study of hydrogen-bound clusters that\nserve as model systems for the quantitative understanding of the intermolecular forces involved\nin (bio )polymers and aqueous media. However, there are currently no terahertz sources that are\neasily tunable over the full region with high precision and accuracy. Here, we discuss the\ndevelopment of a novel three-laser source that allows for accurate stabilization of the difference\nfrequency between two diode lasers to any frequency up to several terahertz, while still\nmaintaining a long-term linewidth of under 10 MHz. When coupled with new traveling-wave\nphotomixers, we will have a narrow linewidth, broadband terahertz source with high accuracy\nand capable of delivering up to tens of microwatts of power.", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10693, title ="Astrophysical Blastwaves", author = "Zukin, Phillip Gregory", month = "January", year = "2006", doi = "10.7907/j6yy-wr15", url = "https://resolver.caltech.edu/CaltechTHESIS:02122018-164440685", revision_no = "21", abstract = "Shock waves are known to significantly alter the medium through with they propagate.\nShocks in the interstellar medium have been known to affect star formation. Likewise,\nshocks in the intergalactic medium are expected to affect galaxy formation and the\nconfinement of intergalactic clouds. Because of their significant influence, it is important\nto have a sound understanding of the different solutions used to study shocks and see how\nthey differ. In this paper, I will focus on the self similar solution, thoroughly developed\nby Ostriker and McKee, and the explosion model, developed by Tegmark, Silk, and\nEvrard. \n", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10633, title ="Millimeter Wave Loss in Superconducting Striplines", author = "Luo, Chiyan", month = "January", year = "2000", url = "https://resolver.caltech.edu/CaltechTHESIS:01102018-103835202", revision_no = "19", abstract = "The temperature dependence of the wave propagation in superconducting striplines from 80 to 100 GHz is experimentally examined for the first time. The measured resonance frequency spacing and temperature shift are in good agreement with theoretical predictions. The loss measurements are limited by SNR in the setup, and an upper limit of 0.01-0.02 of dielectric loss tangent is estimated near 80 GHz from 1.6K to 4.2K.", } @misc {CaltechTHESIS_https://thesis.library.caltech.edu/id/eprint/10631, title ="On the Kinematics of Galaxies and Associated QSO Absorption Systems", author = "Kollmeier, Juna Ariele", month = "January", year = "2000", url = "https://resolver.caltech.edu/CaltechTHESIS:01102018-103039886", revision_no = "19", abstract = "The methods available for studying galaxies directly, both individually and\nas a class of objects, limit astronomers to certain regions of parameter space.\nSince most observational techniques are rooted in the collection and analysis\nof photons, there is always the danger of preferentially studying those\nobjects for which this information is more readily obtained. Such selection\neffects can dramatically alter the physical picture one deduces. For example,\ndetailed studies of galaxies at optical wavelengths becomes extremely\ndifficult for objects located at distances corresponding to z approx. 1.5-3.\nFurthermore, certain structures are too diffuse and/or faint to detect from\ntheir emission signatures alone, even at relatively low redshifts. For example,\nfor material in the outer regions of the galaxy, where only small amounts\nof star formation are occuring, it is very difficult to detect the presence of\nthe material from optical images alone despite the advent of ever bigger and\nbetter instruments and telescopes. Fortunately, several methods exist that\nallow astronomers to avoid these observational hurdles. One such method\nis the use of quasar (QSO) absorption line systems.", }