A non-baryonic matter beyond the framework of the Standard Model is required to explain a vast set of astrophysical and cosmological phenomena in our universe; it is referred to as dark matter and comprises 85% of all matter. Previously centered on particle candidates in the 1 GeV to 10 TeV mass range, dark matter model building has expanded to masses well beyond that range, with an emphasis toward low-mass particles below 1 GeV. Low-mass dark matter models have invoked new and creative mechanisms for producing the relic abundance of dark matter and in doing so have provided a variety of new laboratory-testable hypotheses about the early universe.
\r\n\r\nDirect detection experiments seek to directly measure a dark matter particle interaction from the Milky Way dark matter halo with ultra-sensitive detector technologies in low-background environments. As the paradigm has shifted toward lower-mass particle candidates, detector technologies have followed suit: single-charge-sensitive detectors and low-threshold, purely phonon-mediated detectors are among the best detector architectures for probing the most immediately accessible\r\ntheoretical models of low-mass dark matter. The Super Cryogenic Dark Matter Search (SuperCDMS) has used and developed detector technologies on both of these fronts. On the axis of single-charge-sensitive detectors, the High Voltage (HV) detector program of the SuperCDMS Collaboration has demonstrated gram-scale, single-charge sensitive detectors known as HVeV detectors. Recent advances in the collaboration\u2019s understanding of single-charge backgrounds have enabled much improved sensitivity to low-mass dark matter parameter space with even these gram-scale detectors. HVeV detectors are a prototype version of the HV kg-scale detectors to be deployed at the flagship SuperCDMS experiment in SNOLAB. HV detectors are projected to test vast regions of unconstrained parameter space for both electron- and nuclear-recoiling dark matter, as shown in Chapter 4 of this thesis among many other SuperCDMS sensitivity projections.
\r\n\r\nA potentially limiting background for SuperCDMS detectors at SNOLAB is the zero-charge low energy excess, which is characterized by an exponentially rising spectrum of background phonon events below about 100 eV to 1 keV recoil energy. Chapter 5 of this thesis presents a data-driven technique to subtract the zero-charge low energy excess (0QLEE) as observed in HVeV detectors. A search for charge-producing, nuclear-recoiling dark matter is performed with this background-subtraction technique. The resultant exposure-limited constraint on the nucleon-dark-matter cross section is nearly a factor of 10\u00d7 stronger than the background-limited constraint and is within tens of percent from unconstrained parameter space. The two dominant sources of systematic uncertainties for this search are (1) the uncertainty on the total rate and spectral shape of zero-charge low energy excess events and (2) the completely unknown behavior of the ionization yield function in silicon for nuclear recoils below 100 eV.
\r\n\r\nOn the axis of low-threshold phonon-mediated detectors, the SuperCDMS Collaboration must improve phonon energy thresholds to below 1 eV in order to attain sensitivity to sub-GeV nucleon-coupled dark matter. Presently, SuperCDMS has achieved detector phonon thresholds in the range from 10 eV to 200 eV depending on detector size. In Chapters 6, 7, and 8, we present a radically different phonon sensor architecture that may provide long-term gains in sensitivity: the kinetic inductance detector.
\r\n\r\nThere are two main quantities that constrain the capacity of kinetic inductance detectors to be effective phonon sensors: the detector readout noise and the phonon collection efficiency. Chapter 7 explores the former, detailing the variety of noise sources in kinetic inductance detectors and how they may impact a sensor\u2019s energy resolution using both theoretical calculations and experimental measurements. In general, resolution on energy absorbed in the sensor is presently limited to a range from 1 eV to 5 eV. Chapter 8 then reports on the overall detector energy performance of three different KID-based phonon-mediated (KIPM) detectors, each of which suffers from percent-scale phonon collection efficiencies. An empirical model is then built to parametrize and understand the reasons for the poor phonon collection efficiencies, thereby outlining a path forward to lowering energy thresholds in KIPM detectors.
", "doi": "10.7907/g23k-c067", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16252", "collection": "thesis", "collection_id": "16252", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11272023-225643701", "primary_object_url": { "basename": "Aralis_Caltech_Thesis.pdf", "content": "final", "filesize": 66683130, "license": "other", "mime_type": "application/pdf", "url": "/16252/1/Aralis_Caltech_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "SuperCDMS SNOLAB, HVeV Run 3, and Development of KIPM Detectors", "author": [ { "family_name": "Aralis", "given_name": "Taylor Benjamin", "orcid": "0000-0002-3501-6948", "clpid": "Aralis-Taylor-Benjamin" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hitlin", "given_name": "David G.", "orcid": "0000-0003-4028-6982", "clpid": "Hitlin-D-G" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Dark matter is the theorized source of many observed large-scale gravitational effects. It is dark in the sense that it lacks any heretofore measurable direct interaction with the electromagnetic spectrum. Being unable to rely on absorption, reflection, or emission of photons makes studying dark matter particularly challenging. Excluding neutrinos, which fail to explain the observed large-scale effects, dark matter has never been conclusively identified in a local laboratory experiment. There are many proposed models that could explain both our large-scale observations and our lack of local observations while still allowing for the possibility of local observation. Ultra-sensitive direct-detection experiments attempt to make precisely such observations. Confirmed detection of a new stable particle would provide important information for improving our understanding of both dark matter and cosmological models.
\r\n\r\nThe SuperCDMS SNOLAB experiment is a direct-detection experiment designed with an initial focus on particle masses < 10 GeV. The experiment will measure both phonon and ionization signals in kg-scale semiconductor crystals held at cryogenic temperatures. In this thesis, I describe the experiment with emphasis on the ionization readout. I also detail the characterization process I performed on the ionization amplifier's low-power high-electron-mobility transistors (HEMTs).
\r\n\r\nSuperCDMS high-voltage eV-resolution (HVeV) detectors are gram-scale detectors designed to achieve single electron-hole-pair sensitivity. The first HVeV direct-detection search produced world-leading exclusion limits for dark-matter masses down to ~1 MeV. Here, I present my work analyzing the third search using such detectors. Run 3 was the first to include multiple detectors operated simultaneously and achieved an order of magnitude greater exposure than previous runs. I report the resulting exclusion limits for electron-coupled, dark-photon, and axion-like-particle dark matter.
\r\n\r\nLastly, I discuss work performed at Caltech towards the development of kinetic-inductance phonon-mediated (KIPM) dark-matter detectors. KIPM detectors use frequency-multiplexed kinetic inductance detectors (KIDs) and have the potential for excellent event-position reconstruction and background rejection. KIPMs also present a clear path towards sub-eV resolution on event recoil energy. Such detectors could be used as part of a payload upgrade in SuperCDMS SNOLAB. KIPMs could also be used in smaller-scale experiments similar to SuperCDMS HVeV.
", "doi": "10.7907/gxjp-0863", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15199", "collection": "thesis", "collection_id": "15199", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05212023-152144355", "primary_object_url": { "basename": "Chang_YenYung_2021.pdf", "content": "final", "filesize": 97488420, "license": "other", "mime_type": "application/pdf", "url": "/15199/1/Chang_YenYung_2021.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "SuperCDMS HVeV Run 2 Low-Mass Dark Matter Search, Highly Multiplexed Phonon-Mediated Particle Detector with Kinetic Inductance Detector, and the Blackbody Radiation in Cryogenic Experiments", "author": [ { "family_name": "Chang", "given_name": "Yen-Yung", "orcid": "0000-0002-6441-980X", "clpid": "Chang-Yen-Yung" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Patterson", "given_name": "Ryan B.", "orcid": "0000-0002-5787-9517", "clpid": "Patterson-R-B" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Porter", "given_name": "Frank C.", "orcid": "0000-0003-1948-8889", "clpid": "Porter-F-C" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "There is ample evidence of dark matter (DM), a phenomenon responsible for \u2248 85% of the matter content of the Universe that cannot be explained by the Standard Model (SM). One of the most compelling hypotheses is that DM consists of beyond-SM particle(s) that are nonluminous and nonbaryonic. So far, numerous efforts have been made to search for particle DM, and yet none has yielded an unambiguous observation of DM particles.
\r\n\r\nWe present in Chapter 2 the SuperCDMS HVeV Run 2 experiment, where we search for DM in the mass ranges of 0.5--10\u2074 MeV/c\u00b2 for the electron-recoil DM and 1.2--50 eV/c\u00b2 for the dark photon and the Axion-like particle (ALP). SuperCDMS utilizes cryogenic crystals as detectors to search for DM interaction with the crystal atoms. The interaction is detected in the form of recoil energy mediated by phonons. In the HVeV project, we look for electron recoil, where we enhance the signal by the Neganov-Trofimov-Luke effect under high-voltage biases. The technique enabled us to detect quantized e\u207bh\u207a creation at a 3% ionization energy resolution. Our work is the first DM search analysis considering charge trapping and impact ionization effects for solid-state detectors. We report our results as upper limits for the assumed particle models as functions of DM mass. Our results exclude the DM-electron scattering cross section, the dark photon kinetic mixing parameter, and the ALP axioelectric coupling above 8.4 x 10\u207b\u00b3\u2074 cm\u00b2, 3.3 x 10\u207b\u00b9\u2074, and 1.0 x 10\u207b\u2079, respectively.
\r\n\r\nCurrently every SuperCDMS detector is equipped with a few phonon sensors based on the transition-edge sensor (TES) technology. In order to improve phonon-mediated particle detectors' background rejection performance, we are developing highly multiplexed detectors utilizing kinetic inductance detectors (KIDs) as phonon sensors. This work is detailed in chapter 3 and chapter 4. We have improved our previous KID and readout line designs, which enabled us to produce our first \u00f83\" detector with 80 phonon sensors. The detector yielded a frequency placement accuracy of 0.07%, indicating our capability of implementing hundreds of phonon sensors in a typical SuperCDMS-style detector. We detail our fabrication technique for simultaneously employing Al and Nb for the KID circuit. We explain our signal model that includes extracting the RF signal, calibrating the RF signal into pair-breaking energy, and then the pulse detection. We summarize our noise condition and develop models for different noise sources. We combine the signal and the noise models to be an energy resolution model for KID-based phonon-mediated detectors. From this model, we propose strategies to further improve future detectors' energy resolution and introduce our ongoing implementations.
\r\n\r\nBlackbody (BB) radiation is one of the plausible background sources responsible for the low-energy background currently preventing low-threshold DM experiments to search for lower DM mass ranges. In Chapter 5, we present our study for such background for cryogenic experiments. We have developed physical models and, based on the models, simulation tools for BB radiation propagation as photons or waves. We have also developed a theoretical model for BB photons' interaction with semiconductor impurities, which is one of the possible channels for generating the leakage current background in SuperCDMS-style detectors. We have planned for an experiment to calibrate our simulation and leakage current generation model. For the experiment, we have developed a specialized ``mesh TES'' photon detector inspired by cosmic microwave background experiments. We present its sensitivity model, the radiation source developed for the calibration, and the general plan of the experiment.
", "doi": "10.7907/jswx-ad33", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15151", "collection": "thesis", "collection_id": "15151", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05052023-033943351", "type": "thesis", "title": "Mock Observations of the Sunyaev-Zel\u2019dovich Effect in Massive Galaxy Clusters and a Six-Layer Integral Antireflective Structure for Silicon Optics", "author": [ { "family_name": "Macioce", "given_name": "Theodore Kenneth", "orcid": "0000-0002-3156-6627", "clpid": "Macioce-Theodore-Kenneth" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Zmuidzinas", "given_name": "Jonas", "orcid": "0000-0002-3330-5439", "clpid": "Zmuidzinas-J" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Part 1: Measuring the kinematic Sunyaev-Zel\u2019dovich (kSZ) effect is a promising observational tool to constrain both cosmic growth and galaxy cluster formation. As millimeter-wave telescopes gain sensitivity and angular resolution over multiple frequency bands, high signal-to-noise imaging of the kSZ effect in large samples of galaxy clusters will become increasingly feasible. However, maximizing the science reach of these upcoming data will require more sophisticated analysis methods to characterize and remove contamination from a range of unwanted signals, such as the emission from dusty star forming galaxies. Current predictions of kSZ-derived constraints do not account for these effects in sufficient detail. Moreover, they typically rely on Fisher matrix analyses, which cannot fully capture the degeneracies among the physical parameters describing the cluster. We present a mock observation and analysis pipeline to determine the science reach of kSZ galaxy cluster observations that employs more detailed noise models and more sophisticated analysis methods. From our mock observations, we derive new forecasts of the constraining power of next-generation telescopes on cluster peculiar velocities for several instrument configurations from the 10-m, 30-m, and 50-m classes. These forecasts will inform the designs of next-generation telescopes targeting kSZ observations and will indicate the optimal instrumentation for both cosmological and cluster-scale constraints. The software pipeline we develop will also be directly usable as an analysis tool once observations from such telescopes become available.
\r\n\r\nPart 2: Silicon optics can greatly benefit future millimeter and submillimeter astronomical instruments thanks to silicon\u2019s useful properties such as low loss, high refractive index, and high strength. However, silicon\u2019s high index (n = 3.4) necessitates antireflection (AR) treatment, which has proven a major challenge, especially for the multilayer treatments required for wide spectral bandwidths. We present our approach to this challenge, in which we develop a wide-bandwidth integral AR structure for silicon optics that uses a novel fabrication technique that combines deep reactive ion etching (DRIE) and wafer bonding. We have previously demonstrated a two-layer AR structure for windows over a 1.6:1 bandwidth and are currently fabricating a four-layer coating for a 4:1 bandwidth. Here, we focus on a design for a six-layer structure optimized to give -20 dB reflection between 80 and 420 GHz (5.25:1 bandwidth), which will be useful for future multicolor SZ observations.
", "doi": "10.7907/w1ds-j507", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:10838", "collection": "thesis", "collection_id": "10838", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272018-205538217", "type": "thesis", "title": "Studying the Extragalactic Background Light with the Second Cosmic Infrared Background ExpeRiment, CIBER-2", "author": [ { "family_name": "Lanz", "given_name": "Alicia Elaine", "orcid": "0000-0003-2565-1558", "clpid": "Lanz-Alicia-Elaine" } ], "thesis_advisor": [ { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Dor\u00e9", "given_name": "Olivier P.", "orcid": "0000-0001-7432-2932", "clpid": "Dor\u00e9-O" }, { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Fluctuations in the extragalactic background light trace emission from the entire history of galaxy formation, including emission from early luminous sources prior to the reionization of the universe. The formation of the first luminous objects represents an important transition in the evolution of the universe from its smooth initial state to the clumpy, highly ordered state observable today. However, these objects are faint and diffuse and not well studied; direct observations of their emission are needed to constrain current numerical simulations of the nonlinear evolution of the early universe. A number of recent near-infrared measurements show excess spatial power at large angular scales inconsistent with models of z < 5 emission from galaxies. These measurements have been interpreted as arising from either redshifted emission of early luminous objects, such as stellar and quasar emission from the epoch of reionization, or the combined intra-halo light from stars thrown out of more recent galaxies during merging activity at lower redshifts. Though astrophysically distinct, both interpretations arise from faint, low surface brightness source populations that are difficult to detect except by statistical approaches using careful observations with suitable instruments. The key to determining the source of these background anisotropies will be wide-field imaging measurements spanning multiple bands from the optical to the near-infrared.
\r\n\r\nThe Cosmic Infrared Background ExpeRiment 2 (CIBER-2) will measure spatial anisotropies in the extragalactic infrared background caused by cosmological structure using six broad spectral bands. The experiment uses three 2048 x 2048 Hawaii-2RG near-infrared arrays in three cameras coupled to a single 28.5 cm telescope housed in a reusable sounding rocket-borne payload. A small portion of each array will also be combined with a linear-variable filter to make absolute measurements of the spectrum of the extragalactic background with high spatial resolution for deep subtraction of Galactic starlight. The large field of view and multiple spectral bands make CIBER-2 unique in its sensitivity to fluctuations predicted by models of lower limits on the luminosity of the first stars and galaxies and in its ability to distinguish between primordial and foreground anisotropies. This work encompasses the scientific motivation for CIBER-2 and describes details of the instrument design and verification prior to flight.
", "doi": "10.7907/CN9Y-MB61", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:11056", "collection": "thesis", "collection_id": "11056", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082018-171453167", "type": "thesis", "title": "A Dark Matter Search Using the Final SuperCDMS Soudan Dataset and the Development of a Large-Format, Highly-Multiplexed, Athermal-Phonon-Mediated Particle Detector", "author": [ { "family_name": "Cornell", "given_name": "Brett Durcan", "clpid": "Cornell-Brett-Durcan" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Over the past eighty years, numerous complementary observations of our universe have indicated that our current description of physics is far from complete. The \"ordinary matter\", such as electrons, protons, photons and neutrons, that constitutes the bulk of all human physical experiences is actually only a minority (about 16%) of the total mass of the universe. The remaining 84% is very poorly understood, but has profound effects on the dynamics and evolution of our universe. Because it does not interact with light, and is not observable in telescopes on earth, this extra mass is usually referred to as \"dark matter\". Although the dark matter is poorly understood, Weakly Interacting Massive Particles (WIMPs) are a well-motivated candidate that can be directly detected via a non-gravitational interaction with normal matter, potentially allowing for direct terrestrial detection and characterization of this dark matter. This dissertation is focused on this direct WIMP detection and will be broken into two main parts.
\r\n\r\nThe first part focuses on the blinded analysis of roughly three years of data collected from March 2012 to November 2015 by the SuperCDMS Soudan experiment. SuperCDMS Soudan consists of an array of 15, 0.6-kg, cryogenic, Ge iZIP particle detectors situated in a decommissioned iron mine in remote northern Minnesota. This analysis is optimized to be sensitive to theoretical WIMP masses above 10 GeV/c2. This result set the strongest limits for WIMP--germanium-nucleus interactions for WIMP masses greater than 12 Gev/c2.
\r\n\r\nThe second part focuses on the development new kind of particle detector in the style of a SuperCDMS iZIP, designed to simplify fabrication and readout, improve phonon-based position reconstruction, and help to scale to larger target arrays. These detectors replace the TES-based phonon sensors of the iZIP with Microwave Kinetic Inductance Detectors (MKIDs).
", "doi": "10.7907/M297-J716", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10637", "collection": "thesis", "collection_id": "10637", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01102018-113943698", "primary_object_url": { "basename": "Su_Y_2016.pdf", "content": "final", "filesize": 15787826, "license": "other", "mime_type": "application/pdf", "url": "/10637/1/Su_Y_2016.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Simulation Pipeline for Velocity Field Measurements using the Kinetic Sunyaev-Zel'dovich Effect", "author": [ { "family_name": "Su", "given_name": "Yubo", "orcid": "0000-0001-8283-3425", "clpid": "Su-Yubo" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "None", "given_name": "None" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The kinetic Sunyaev-Zel 'dovich (kSZ) effect is of great cosmological interest for\r\nproviding precision measurements of peculiar velocity fields independent of systematics\r\npresent in other cosmological probes. The high precision kSZ measurements\r\non the horizon are expected to yield valuable constraints distinguishing between\r\ncompeting cosmological models. Instrumental to kSZ astromony is the removal of\r\ncontaminating point sources, primarily radio and dusty, star-forming galaxies that\r\nhave bright emissions in kSZ spectral bands. As the precision of measurements\r\nimprove, the source removal residuals may become significant contributions to the\r\noverall kSZ error budget. A full simulation is essential to characterizing these induced\r\nerrors. This study develops a procedure for contamination removal from first\r\nprinciples, verifying its optimality against information theoretic limits. Models for\r\ncontaminating sources of increasing complexity are considered, at each step characterizing\r\nthe optimality of the subtraction compared to theoretical bounds. The final,\r\ncurrently unfinished objective is to apply this subtraction procedure to a realistic\r\nsource distribution and understand the incurred systematics.", "doi": "10.7907/727E-BW81", "publication_date": "2016", "thesis_type": "senior_major", "thesis_year": "2016" }, { "id": "thesis:9238", "collection": "thesis", "collection_id": "9238", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10212015-211417853", "primary_object_url": { "basename": "siegel_seth_2016_thesis.pdf", "content": "final", "filesize": 29094572, "license": "other", "mime_type": "application/pdf", "url": "/9238/1/siegel_seth_2016_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "A Multiwavelength Study of the Intracluster Medium and the Characterization of the Multiwavelength Sub/millimeter Inductance Camera", "author": [ { "family_name": "Siegel", "given_name": "Seth Robert", "orcid": "0000-0003-2631-6217", "clpid": "Siegel-Seth-Robert" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "orcid": "0000-0002-3330-5439", "clpid": "Zmuidzinas-J" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Bartlett", "given_name": "James", "clpid": "Bartlett-James" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The first part of this thesis combines Bolocam observations of the thermal Sunyaev-Zel\u2019dovich (SZ) effect at 140 GHz with X-ray observations from Chandra, strong lensing data from the Hubble Space Telescope (HST), and weak lensing data from HST and Subaru to constrain parametric models for the distribution of dark and baryonic matter in a sample of six massive, dynamically relaxed galaxy clusters. For five of the six clusters, the full multiwavelength dataset is well described by a relatively simple model that assumes spherical symmetry, hydrostatic equilibrium, and entirely thermal pressure support. The multiwavelength analysis yields considerably better constraints on the total mass and concentration compared to analysis of any one dataset individually. The subsample of five galaxy clusters is used to place an upper limit on the fraction of pressure support in the intracluster medium (ICM) due to nonthermal processes, such as turbulent and bulk flow of the gas. We constrain the nonthermal pressure fraction at r500c to be less than 0.11 at 95% confidence, where r500c refers to radius at which the average enclosed density is 500 times the critical density of the Universe. This is in tension with state-of-the-art hydrodynamical simulations, which predict a nonthermal pressure fraction of approximately 0.25 at r500c for the clusters in this sample.
\r\n\r\nThe second part of this thesis focuses on the characterization of the Multiwavelength Sub/millimeter Inductance Camera (MUSIC), a photometric imaging camera that was commissioned at the Caltech Submillimeter Observatory (CSO) in 2012. MUSIC is designed to have a 14 arcminute, diffraction-limited field of view populated with 576 spatial pixels that are simultaneously sensitive to four bands at 150, 220, 290, and 350 GHz. It is well-suited for studies of dusty star forming galaxies, galaxy clusters via the SZ Effect, and galactic star formation. MUSIC employs a number of novel detector technologies: broadband phased-arrays of slot dipole antennas for beam formation, on-chip lumped element filters for band definition, and Microwave Kinetic Inductance Detectors (MKIDs) for transduction of incoming light to electric signal. MKIDs are superconducting micro-resonators coupled to a feedline. Incoming light breaks apart Cooper pairs in the superconductor, causing a change in the quality factor and frequency of the resonator. This is read out as amplitude and phase modulation of a microwave probe signal centered on the resonant frequency. By tuning each resonator to a slightly different frequency and sending out a superposition of probe signals, hundreds of detectors can be read out on a single feedline. This natural capability for large scale, frequency domain multiplexing combined with relatively simple fabrication makes MKIDs a promising low temperature detector for future kilopixel sub/millimeter instruments. There is also considerable interest in using MKIDs for optical through near-infrared spectrophotometry due to their fast microsecond response time and modest energy resolution. In order to optimize the MKID design to obtain suitable performance for any particular application, it is critical to have a well-understood physical model for the detectors and the sources of noise to which they are susceptible. MUSIC has collected many hours of on-sky data with over 1000 MKIDs. This work studies the performance of the detectors in the context of one such physical model. Chapter 2 describes the theoretical model for the responsivity and noise of MKIDs. Chapter 3 outlines the set of measurements used to calibrate this model for the MUSIC detectors. Chapter 4 presents the resulting estimates of the spectral response, optical efficiency, and on-sky loading. The measured detector response to Uranus is compared to the calibrated model prediction in order to determine how well the model describes the propagation of signal through the full instrument. Chapter 5 examines the noise present in the detector timestreams during recent science observations. Noise due to fluctuations in atmospheric emission dominate at long timescales (less than 0.5 Hz). Fluctuations in the amplitude and phase of the microwave probe signal due to the readout electronics contribute significant 1/f and drift-type noise at shorter timescales. The atmospheric noise is removed by creating a template for the fluctuations in atmospheric emission from weighted averages of the detector timestreams. The electronics noise is removed by using probe signals centered off-resonance to construct templates for the amplitude and phase fluctuations. The algorithms that perform the atmospheric and electronic noise removal are described. After removal, we find good agreement between the observed residual noise and our expectation for intrinsic detector noise over a significant fraction of the signal bandwidth.
", "doi": "10.7907/Z9Z31WJ7", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:8896", "collection": "thesis", "collection_id": "8896", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282015-121920930", "primary_object_url": { "basename": "PhDthesis_final_Chenguang Ji_05182015.pdf", "content": "final", "filesize": 3357230, "license": "other", "mime_type": "application/pdf", "url": "/8896/1/PhDthesis_final_Chenguang Ji_05182015.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Design of Antenna-Coupled Lumped-Element Titanium Nitride KIDs for LongWavelength Multi-Band Continuum Imaging", "author": [ { "family_name": "Ji", "given_name": "Chenguang", "clpid": "Ji-Chenguang" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" }, { "family_name": "Johnson", "given_name": "William L.", "clpid": "Johnson-W-L" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "clpid": "Zmuidzinas-J" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_eng" } ], "abstract": "Many applications in cosmology and astrophysics at millimeter wavelengths including CMB polarization, studies of galaxy clusters using the Sunyaev-Zeldovich effect (SZE), and studies of star formation at high redshift and in our local universe and our galaxy, require large-format arrays of millimeter-wave detectors. Feedhorn and phased-array antenna architectures for receiving mm-wave light present numerous advantages for control of systematics, for simultaneous coverage of both polarizations and/or multiple spectral bands, and for preserving the coherent nature of the incoming light. This enables the application of many traditional \"RF\" structures such as hybrids, switches,\r\nand lumped-element or microstrip band-defining filters.
\r\n\r\nSimultaneously, kinetic inductance detectors (KIDs) using high-resistivity materials like titanium nitride are an attractive sensor option for large-format arrays because they are highly multiplexable and because they can have sensitivities reaching the condition of background-limited detection. A\r\nKID is a LC resonator. Its inductance includes the geometric inductance and kinetic inductance of the inductor in the superconducting phase. A photon absorbed by the superconductor breaks a Cooper pair into normal-state electrons and perturbs its kinetic inductance, rendering it a detector\r\nof light. The responsivity of KID is given by the fractional frequency shift of the LC resonator per unit optical power.
\r\n\r\nHowever, coupling these types of optical reception elements to KIDs is a challenge because of the impedance mismatch between the microstrip transmission line exiting these architectures and the high resistivity of titanium nitride. Mitigating direct absorption of light through free space coupling to the inductor of KID is another challenge. We present a detailed titanium nitride KID\r\ndesign that addresses these challenges. The KID inductor is capacitively coupled to the microstrip in such a way as to form a lossy termination without creating an impedance mismatch. A parallel plate capacitor design mitigates direct absorption, uses hydrogenated amorphous silicon, and yields acceptable noise. We show that the optimized design can yield expected sensitivities very close to\r\nthe fundamental limit for a long wavelength imager (LWCam) that covers six spectral bands from 90 to 400 GHz for SZE studies.
\r\n\r\nExcess phase (frequency) noise has been observed in KID and is very likely caused by two-level systems (TLS) in dielectric materials. The TLS hypothesis is supported by the measured dependence of the noise on resonator internal power and temperature. However, there is still a lack of a unified microscopic theory which can quantitatively model the properties of the TLS noise. In this thesis we\r\nderive the noise power spectral density due to the coupling of TLS with phonon bath based on an existing model and compare the theoretical predictions about power and temperature dependences with experimental data. We discuss the limitation of such a model and propose the direction for future study.
", "doi": "10.7907/Z9W66HQ7", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8898", "collection": "thesis", "collection_id": "8898", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282015-141343540", "primary_object_url": { "basename": "saFN999I9qeezyfjOAIBOSbqqbgW0lXJe8VCTAf7R624ttavA87cha2LoU7i0CUv", "content": "final", "filesize": 72440132, "license": "other", "mime_type": "application/pdf", "url": "/8898/1/saFN999I9qeezyfjOAIBOSbqqbgW0lXJe8VCTAf7R624ttavA87cha2LoU7i0CUv", "version": "v4.0.0" }, "type": "thesis", "title": "Instrumentation for Kinetic-Inductance-Detector-Based Submillimeter Radio Astronomy", "author": [ { "family_name": "Duan", "given_name": "Ran", "clpid": "Duan-Ran" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "clpid": "Zmuidzinas-J" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_eng" } ], "abstract": "A substantial amount of important scientific information is contained within astronomical data at the submillimeter and far-infrared (FIR) wavelengths, including information regarding dusty galaxies, galaxy clusters, and star-forming regions; however, these wavelengths are among the least-explored\r\nfields in astronomy because of the technological difficulties involved in such research. Over the past 20 years, considerable efforts have been devoted to developing submillimeter- and millimeter-wavelength astronomical instruments and telescopes.
\r\n\r\nThe number of detectors is an important property of such instruments and is the subject of the current study. Future telescopes will require as many as hundreds of thousands of detectors to meet the necessary requirements in terms of the field of view, scan speed, and resolution. A large pixel count is one benefit of the development of multiplexable detectors that use kinetic inductance detector (KID) technology.
\r\n\r\nThis dissertation presents the development of a KID-based instrument including a portion of the millimeter-wave bandpass filters and all aspects of the readout electronics, which together enabled one of the largest detector counts achieved to date in submillimeter-/millimeter-wavelength imaging arrays: a total of 2304 detectors. The work presented in this dissertation has been implemented in the MUltiwavelength Submillimeter Inductance Camera (MUSIC), a new instrument for the Caltech Submillimeter Observatory (CSO).
", "doi": "10.7907/Z90P0WXZ", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8448", "collection": "thesis", "collection_id": "8448", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302014-170605877", "primary_object_url": { "basename": "Tucker_PhDthesis.pdf", "content": "final", "filesize": 47614875, "license": "other", "mime_type": "application/pdf", "url": "/8448/1/Tucker_PhDthesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Characterization of Detectors and Instrument Systematics for the SPIDER CMB Polarimeter", "author": [ { "family_name": "Tucker", "given_name": "Rebecca Suzanne", "clpid": "Tucker-Rebecca-Suzanne" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Martin", "given_name": "D. Christopher", "orcid": "0000-0002-8650-1644", "clpid": "Martin-D-Christopher" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We know from the CMB and observations of large-scale structure that the universe is extremely flat, homogenous, and isotropic. The current favored mechanism for generating these characteristics is inflation, a theorized period of exponential expansion of the universe that occurred shortly after the Big Bang. Most theories of inflation generically predict a background of stochastic gravitational waves. These gravitational waves should leave their unique imprint on the polarization of the CMB via Thompson scattering. Scalar perturbations of the metric will cause a pattern of polarization with no curl (E-mode). Tensor perturbations (gravitational waves) will cause a unique pattern of polarization on the CMB that includes a curl component (B-mode). A measurement of the ratio of the tensor to scalar perturbations (r) tells us the energy scale of inflation. Recent measurements by the BICEP2 team detect the B-mode spectrum with a tensor-to-scalar ratio of r = 0.2 (+0.05, \u22120.07). An independent confirmation of this result is the next step towards understanding the inflationary universe.
\r\n\r\nThis thesis describes my work on a balloon-borne polarimeter called SPIDER, which is designed to illuminate the physics of the early universe through measurements of the cosmic microwave background polarization. SPIDER consists of six single-frequency, on-axis refracting telescopes contained in a shared-vacuum liquid-helium cryostat. Its large format arrays of millimeter-wave detectors and tight control of systematics will give it unprecedented sensitivity. This thesis describes how the SPIDER detectors are characterized and calibrated for flight, as well as how the systematics requirements for the SPIDER system are simulated and measured.
", "doi": "10.7907/HNHF-HA43", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7866", "collection": "thesis", "collection_id": "7866", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072013-113004037", "type": "thesis", "title": "Testing Inflationary Cosmology with the BICEP1 and BICEP2 Experiments", "author": [ { "family_name": "Aikin", "given_name": "Randol Wallace", "clpid": "Aikin-Randol-Wallace" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Recent observations of the temperature anisotropies of the cosmic microwave background (CMB) favor an inflationary paradigm in which the scale factor of the universe inflated by many orders of magnitude at some very early time. Such a scenario would produce the observed large-scale isotropy and homogeneity of the universe, as well as the scale-invariant perturbations responsible for the observed (10 parts per million) anisotropies in the CMB. An inflationary epoch is also theorized to produce a background of gravitational waves (or tensor perturbations), the effects of which can be observed in the polarization of the CMB. The E-mode (or parity even) polarization of the CMB, which is produced by scalar perturbations, has now been measured with high significance. Con- trastingly, today the B-mode (or parity odd) polarization, which is sourced by tensor perturbations, has yet to be observed. A detection of the B-mode polarization of the CMB would provide strong evidence for an inflationary epoch early in the universe\u2019s history.
\r\n\r\nIn this work, we explore experimental techniques and analysis methods used to probe the B- mode polarization of the CMB. These experimental techniques have been used to build the Bicep2 telescope, which was deployed to the South Pole in 2009. After three years of observations, Bicep2 has acquired one of the deepest observations of the degree-scale polarization of the CMB to date. Similarly, this work describes analysis methods developed for the Bicep1 three-year data analysis, which includes the full data set acquired by Bicep1. This analysis has produced the tightest constraint on the B-mode polarization of the CMB to date, corresponding to a tensor-to-scalar ratio estimate of r = 0.04\u00b10.32, or a Bayesian 95% credible interval of r < 0.70. These analysis methods, in addition to producing this new constraint, are directly applicable to future analyses of Bicep2 data. Taken together, the experimental techniques and analysis methods described herein promise to open a new observational window into the inflationary epoch and the initial conditions of our universe.
", "doi": "10.7907/z9vx0df2", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7842", "collection": "thesis", "collection_id": "7842", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052013-104216835", "primary_object_url": { "basename": "czakon_thesis_2013.pdf", "content": "final", "filesize": 8414061, "license": "other", "mime_type": "application/pdf", "url": "/7842/1/czakon_thesis_2013.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Sunyaev-Zel\u2019dovich Observations Using Large-Format Millimeter Arrays", "author": [ { "family_name": "Czakon", "given_name": "Nicole Gisela", "clpid": "Czakon-Nicole-Gisela" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "clpid": "Zmuidzinas-J" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Galaxy clusters are the largest gravitationally bound objects in the observable universe, and they are formed from the largest perturbations of the primordial matter power spectrum. During initial cluster collapse, matter is accelerated to supersonic velocities, and the baryonic component is heated as it passes through accretion shocks. This process stabilizes when the pressure of the bound matter prevents further gravitational collapse. Galaxy clusters are useful cosmological probes, because their formation progressively freezes out at the epoch when dark energy begins to dominate the expansion and energy density of the universe. A diverse set of observables, from radio through X-ray wavelengths, are sourced from galaxy clusters, and this is useful for self-calibration. The distributions of these observables trace a cluster's dark matter halo, which represents more than 80% of the cluster's gravitational potential. One such observable is the Sunyaev-Zel'dovich effect (SZE), which results when the ionized intercluster medium blueshifts the cosmic microwave background via Compton scattering. Great technical advances in the last several decades have made regular observation of the SZE possible. Resolved SZE science, such as is explored in this analysis, has benefitted from the construction of large-format camera arrays consisting of highly sensitive millimeter-wave detectors, such as Bolocam. Bolocam is a submillimeter camera, sensitive to 140 GHz and 268 GHz radiation, located at one of the best observing sites in the world: the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. Bolocam fielded 144 of the original spider web NTD bolometers used in an entire generation of ground-based, balloon-borne, and satellite-borne millimeter wave instrumention. Over approximately six years, our group at Caltech has developed a mature galaxy cluster observational program with Bolocam. This thesis describes the construction of the instrument's full cluster catalog: BOXSZ. Using this catalog, I have scaled the Bolocam SZE measurements with X-ray mass approximations in an effort to characterize the SZE signal as a viable mass probe for cosmology. This work has confirmed the SZE to be a low-scatter tracer of cluster mass. The analysis has also revealed how sensitive the SZE-mass scaling is to small biases in the adopted mass approximation. Future Bolocam analysis efforts are set on resolving these discrepancies by approximating cluster mass jointly with different observational probes.", "doi": "10.7907/SRVP-D536", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:6534", "collection": "thesis", "collection_id": "6534", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07022011-083421311", "type": "thesis", "title": "The SPIDER CMB Polarimeter", "author": [ { "family_name": "Trangsrud", "given_name": "Amy Ruth", "clpid": "Trangsrud-Amy-Ruth" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "SPIDER is a balloon-borne millimeter-wave telescope designed to study the polarization of the Cosmic Microwave Background (CMB). SPIDER will map 10% of the full sky with degree-scale beams to search for the distinctive inflationary gravitational wave signal on angular scales between 1 degree and 10 degrees, thereby probing the energy scale of inflation. In its first flight, SPIDER will field 2,400 antenna-coupled bolometers split between two bands centered at 93 GHz and 148 GHz. Slot antenna arrays, band defining microstrip filters and superconducting bolometers are all fabricated photolithographically on a shared silicon substrate. SPIDER's detectors are split amongst six monochromatic on-axis refractors in a shared helium-cooled cryostat. This thesis reviews the design of SPIDER and its antenna-coupled bolometers, and details the currently achieved performance of SPIDER's receivers.", "doi": "10.7907/83YV-A258", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6542", "collection": "thesis", "collection_id": "6542", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07182011-183516791", "type": "thesis", "title": "A Dark-Matter Search Using the Final CDMS II Dataset and a Novel Detector of Surface Radiocontamination", "author": [ { "family_name": "Ahmed", "given_name": "Zeeshan", "clpid": "Ahmed-Zeeshan" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "clpid": "Kamionkowski-M-P" }, { "family_name": "Harrison", "given_name": "Fiona A.", "clpid": "Harrison-F-A" }, { "family_name": "Filippone", "given_name": "Bradley W.", "clpid": "Filippone-B-W" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Substantial evidence from galaxies, galaxy clusters, and cosmological scales suggests that ~85% of the matter of our universe is invisible. The missing matter, or \"dark matter\" is likely composed of non-relativistic, non-baryonic particles, which have very rare interactions with baryonic matter and with one another. Among dark matter candidates, Weakly Interacting Massive Particles (WIMPs) are particularly well motivated. In the early universe, thermally produced particles with weak-scale mass and interactions would `freeze out\u2019 at the correct density to be dark matter today. Extensions to the Standard Model of particle physics, such as Supersymmetry, which solve gauge hierarchy and coupling unification problems, naturally provide such particles.
\r\n\r\nInteractions of WIMPs with baryons are expected to be rare, but might be detectable in low-noise detectors. The Cryogenic Dark Matter Search (CDMS) experiment uses ionization- and phonon- sensitive germanium particle detectors to search for such interactions. CDMS detectors are operated at the Soudan Underground Laboratory in Minnesota, within a shielded environment to lower cosmogenic and radioactive background. The combination of phonon and ionization signatures from the detectors provides excellent residual-background rejection.
\r\n\r\nThis dissertation presents improved techniques for phonon calibration of CDMS II detectors and the analysis of the final CDMS II dataset with 612 kg-days of exposure. We set a limit of 3.8x10^(-44) cm^2 on WIMP-nucleon spin-independent scattering cross section for a WIMP mass of 70 GeV/c^2. At the time this analysis was published, these data presented the most stringent limits on WIMP scattering for WIMP masses over 42 GeV/c^2, ruling out previously unexplored parameter space.
\r\n\r\nNext-generation rare-event searches such as SuperCDMS, COUPP, and CLEAN will be limited in sensitivity, unless they achieve stringent control of the surface radioactive contamination on their detectors. Low-penetrating radiation, such as alpha and beta particles, will mimic signal in these experiments. This dissertation also presents the design and prototyping of a novel detector for surface radiocontaminants, called the BetaCage --- a neon-gas time projection chamber built from radiopure materials and operated underground with shielding similar to CDMS II. The BetaCage will enable beta screening of materials at world-best sensitivity of 10^(-5)/cm^2/keV/day, providing a valuable tool to the physics community.
", "doi": "10.7907/W7TT-1E07", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7043", "collection": "thesis", "collection_id": "7043", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05172012-142723949", "primary_object_url": { "basename": "Moore_2012_thesis.pdf", "content": "final", "filesize": 35726359, "license": "other", "mime_type": "application/pdf", "url": "/7043/1/Moore_2012_thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "A Search for Low-Mass Dark Matter with the Cryogenic Dark Matter Search and the Development of Highly Multiplexed Phonon-Mediated Particle Detectors", "author": [ { "family_name": "Moore", "given_name": "David Craig", "clpid": "Moore-David-Craig" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Hitlin", "given_name": "David G.", "clpid": "Hitlin-D-G" }, { "family_name": "Patterson", "given_name": "Ryan B.", "clpid": "Patterson-R-B" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "A wide variety of astrophysical observations indicate that approximately 85% of the matter in the universe is nonbaryonic and nonluminous. Understanding the nature of this \"dark matter\" is one of the most important outstanding questions in cosmology. Weakly Interacting Massive Particles (WIMPs) are a leading candidate for dark matter since they would be thermally produced in the early universe in the correct abundance to account for the observed relic density of dark matter. If WIMPs account for the dark matter, then rare interactions from relic WIMPs should be observable in terrestrial detectors. Recently, unexplained excess events in the DAMA/LIBRA, CoGeNT, and CRESST-II experiments have been interpreted as evidence of scattering from WIMPs with masses ~10 GeV and spin-independent scattering cross sections of 10-41-10-40 cm2.
\r\n\r\nThe Cryogenic Dark Matter Search (CDMS II) attempts to identify WIMP interactions using an array of cryogenic germanium and silicon particle detectors located at the Soudan Underground Laboratory in northern Minnesota. In this dissertation, data taken by CDMS II are reanalyzed using a 2 keV recoil energy threshold to increase the sensitivity to WIMPs with masses ~10 GeV. These data disfavor an explanation for the DAMA/LIBRA, CoGeNT, and CRESST-II results in terms of spin-independent elastic scattering of WIMPs with masses \u227212 GeV, under standard assumptions. At the time of publication, they provided the strongest constraints on spin-independent elastic scattering from 5-9 GeV, ruling out previously unexplored parameter space.
\r\n\r\nTo detect WIMPs or exclude the remaining parameter space favored by the most popular models will ultimately require detectors with target masses \u22731 ton, requiring an increase in mass by more than two orders of magnitude over CDMS II. For cryogenic detectors such as CDMS, scaling to such large target masses will require individual detector elements to be fabricated more quickly and cheaply, while maintaining the nearly background-free operation of the existing experiment. We describe the development of athermal phonon mediated particle detectors using Microwave Kinetic Inductance Detectors (MKIDs), which could provide a simpler path to extending the CDMS detector technology to the ton scale. Results from prototype devices have demonstrated energy resolutions as good as \u03c3 = 0.55 keV at 30 keV, comparable to existing CDMS II detectors. Such designs can be scaled to kg-scale detector elements, while reducing the complexity of the detector fabrication and cryogenic readout electronics relative to existing designs. Since MKIDs are naturally multiplexed in the frequency domain, MKID-based designs also allow much finer pixelization of the phonon sensor, which is expected to enhance background rejection for large detectors while simultaneously reducing the number of wires needed to read out the detectors.
", "doi": "10.7907/X8JD-4R90", "publication_date": "2012-06-15", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7094", "collection": "thesis", "collection_id": "7094", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302012-095444014", "type": "thesis", "title": "Searching for Primordial Gravitational Waves at Degree Scales from the South Pole", "author": [ { "family_name": "Brevik", "given_name": "Justus Albert", "orcid": "0000-0002-8058-5197", "clpid": "Brevik-Justus-Albert" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Bock", "given_name": "James J.", "orcid": "0000-0002-5710-5212", "clpid": "Bock-J-J" }, { "family_name": "Adhikari", "given_name": "Rana", "orcid": "0000-0002-5731-5076", "clpid": "Adhikari-R" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We report on the preliminary performance of the Bicep2 mm-wave polarimeter, deployed in 2009 to the South Pole and will observe through 2012. Bicep2 is currently imaging the polarization of the cosmic microwave background at 150 GHz using an array of 512 antenna-coupled superconducting bolometers. It has been designed for high sensitivity and low systematics in order to pursue the primordial B-mode polarization signal. The instrument and its characterization are presented in this thesis, with particular attention to the detectors and readout system. The instrument sensitivity, mapping speed are discussed along with the expected constraint on the scalar-to-tensor ratio that should be made from one year of data.", "doi": "10.7907/E6Z2-CV94", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:5130", "collection": "thesis", "collection_id": "5130", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12232007-013248", "primary_object_url": { "basename": "Sayers_thesis_20071231.pdf", "content": "final", "filesize": 8379682, "license": "other", "mime_type": "application/pdf", "url": "/5130/1/Sayers_thesis_20071231.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "A Search for Cosmic Microwave Background Anisotropies on Arcminute Scales", "author": [ { "family_name": "Sayers", "given_name": "Jack", "orcid": "0000-0002-8213-3784", "clpid": "Sayers-Jack" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "clpid": "Golwala-S-R" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "clpid": "Kamionkowski-M-P" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" } ], "local_group": [ { "literal": "Caltech Submillimeter Observatory" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "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", "doi": "10.7907/2Q9Q-JA33", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" } ]