Building on the legacies of Planck and the Atacama Cosmology Telescope, among others, future cosmic microwave background (CMB) observatories are poised to revolutionize our understanding of the cosmos by implementing proven detector systems at scales previously incomprehensible. Leading the charge is Simons Observatory (SO), a suite of four telescopes located at 5,200 meters elevation in the Atacama Desert of Chile. With more than 60,000 transition-edge sensor (TES) detectors deployed in six frequency bands across three half-meter telescopes and one 6-meter telescope, SO will observe CMB temperature and polarization at small and large scales with greater sensitivity and control over systematics than has yet been achieved. In deploying more detectors than all other previous CMB experiments combined, SO must also chart new territory in the realm of TES readout. Breakthroughs in microwave multiplexing (μ-mux) readout technology now allow the simultaneous readout of approximately 1,000 detectors on a single set of cables, far surpassing the capabilities of previous systems. For the Large Aperture Telescope’s >30,000 detectors, this translates to a total of just 45 input/output lines. A crucial piece of the SO readout architecture is the Universal Readout Harness (URH), a "plug-and-play" assembly that contains the 300K-4K elements. Configurable to support the readout requirements of each receiver, each URH can support up to 24 readout lines. In addition to the radiofrequency (RF) components, the URH can also support up to 12x50-wire DC cable looms, which provide detector and amplifier power. This dissertation describes the construction and testing of the 6 URHs required for nominal SO operations, as well as the on-site integration of the first Small Aperture Telescope. Separately, an optical stacking analysis of quiescent galaxies at z~1 using images from the Dark Energy Survey is presented. Motivated by a desire to better understand the evolution of massive elliptical galaxies, high signal-to-noise images generated from averaging ~100,000 individual galaxy cutouts are used to calculate surface brightness profiles in the grizY bands. Additionally, the extragalactic background light is derived from these stacks and is found to be in good agreement with previous measurements.

The Balloon-borne Large Aperture Submillimeter Telescope - The Next Generation (BLAST-TNG) was designed to map the polarized emission from dust in star forming regions of our galaxy. The dust is thought to trace magnetic fields and thus inform us of the role that it plays in star formation. BLAST-TNG improves upon the previous generation of balloon-borne sub-mm polarimeters by increasing the number of detectors by over an order of magnitude. A novel detector technology which is naturally multiplexed, Kinetic Inductance Detectors have been developed as an elegant solution to the challenge of packing cryogenic focal plane arrays with detectors. To readout the multiplexed arrays, custom firmware and control software was developed for the ROACH2 FPGA based system. On January 6th 2020 the telescope was launched on a high-altitude balloon from Antarctica and flew for approximately 15 hours in the mid-stratosphere. During this time various calibration tasks occurred such as atmospheric skydips, the mapping of a sub-mm source, and the flashing of an internal calibration lamp. A mechanical failure shortened the flight so that only calibration scans were performed. In this dissertation I will present my analysis of the in-flight calibration data leading to measures of the overall telescope sensitivity and detector performance. The results of which prove kinetic inductance detectors as a viable candidate for future space based sub-mm telescopes. In parallel the fields of digital communications and radar signal processing have spawned the development of the Radio Frequency System On a Chip (RFSoC). This product by Xilinx incorporates a fabric of reconfigurable logic, ARM microprocessors, and high speed digitizers all into one chip. The system specs provide an improvement in every category of size, weight, power, and bandwidth.This is naturally the desired platform for the next generation of far-infrared telescopes which are pushing the limits of detector counts. I present the development of one of the first frequency multiplexed detector readouts on the RFSoC platform. Alternative firmware designs implemented on the RFSoC are also discussed. The firmware work presented will be used in part or in full for multiple current and upcoming far-infrared telescopes.

Isotope ratios of some trace metals have proven useful for tracking Earth’s ocean oxygenation history. As the limitations of some of these isotope systems are realized, it becomes increasingly important to develop new and complementary systems. This dissertation examines the utility of molybdenum (98Mo) and thallium (205Tl) isotope compositions preserved in ancient marine shales to track past ocean oxygenation. My approach is as follows: (1) as an initial exercise, apply the well-established Mo isotope system to a set of ancient shales; (2) validate the use of the newly developed Tl isotope system; and finally (3) examine the potential of applying Mo and Tl isotopes in tandem.

Increasingly heavier 98Mo are found in shales deposited during the Neoarchean (2,800 to 2,500 million years ago, or Ma), which would be a predicted consequence of progressive ocean oxygenation across this timeframe. Increasingly heavier 205Tl across a well-documented Mesozoic Oceanic Anoxic Event (~94 Ma), on the other hand, would be a predicted consequence of progressive ocean de-oxygenation. An anti-correlation in the first combined application of Mo and Tl isotopes in ancient shales provides a strong fingerprint for previously unrecognized levels of ocean oxygenation at ~2,500 Ma. Lastly, neither 98Mo or 205Tl behave as predicted in shales deposited during three Ediacaran Ocean Oxygenation Events (~635 Ma, ~580 Ma, and ~560 Ma). These unexpected trends are due, at least in part, to local-scale overprints that must be taken into consideration when pairing together Mo and Tl isotopes in shales.

The ability of the Mo and Tl isotope systems to track changes in past ocean oxygenation is confirmed in this dissertation. Both isotope systems have the potential to track these changes independently, but their combined utility is particularly powerful. Under ideal conditions, their combined application can provide an even more robust fingerprint for changes in past ocean oxygenation. Even under non-ideal conditions, their combined application makes it possible to decipher local-scale overprints from signals of past ocean oxygenation. It is therefore ideal, whenever possible, to measure both 98Mo and 205Tl in the same shale samples to assess past changes in ocean oxygenation.

The inductance of a conductor expresses its tendency to oppose a change in current flowing through it. For superconductors, in addition to the familiar magnetic inductance due to energy stored in the magnetic field generated by this current, kinetic inductance due to inertia of charge carriers is a significant and often dominant contribution to total inductance. Devices based on modifying the kinetic inductance of thin film superconductors have widespread application to millimeter-wave astronomy. Lithographically patterning such a film into a high quality factor resonator produces a high sensitivity photodetector known as a kinetic inductance detector (KID), which is sensitive to frequencies above the superconducting energy gap of the chosen material. Inherently multiplexable in the frequency domain and relatively simple to fabricate, KIDs pave the way to the large format focal plane array instruments necessary to conduct the next generation of cosmic microwave background (CMB), star formation, and galaxy evolution studies. In addition, non-linear kinetic inductance can be exploited to develop traveling wave kinetic inductance parametric amplifiers (TKIPs) based on superconducting delay lines to read out these instruments.

I present my contributions to both large and small scale collaborative efforts to develop KID arrays, spectrometers integrated with KIDs, and TKIPs. I optimize a dual polarization TiN KID absorber for the next generation Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry, which is designed to investigate the role magnetic fields play in star formation. As part of an effort to demonstrate aluminum KIDs on sky for CMB polarimetry, I fabricate devices for three design variants. SuperSpec and WSpec are respectively the on-chip and waveguide implementations of a filter bank spectrometer concept designed for survey spectroscopy of high redshift galaxies. I provide a robust tool for characterizing the performance of all SuperSpec devices and demonstrate basic functionality of the first WSpec prototype. As part of an effort to develop the first W-Band (75-110 GHz) TKIP, I construct a cryogenic waveguide feedthrough, which enhances the Astronomical Instrumentation Laboratory’s capability to test W-Band devices in general. These efforts contribute to the continued maturation of these kinetic inductance technologies, which will usher in a new era of millimeter-wave astronomy.

Cosmology, carrying imprints from the entire history of the universe, has emerged as a precise observational science over the past 30 years. It can probe physics beyond the Standard Model at energy scales much higher than the weak scale. This thesis reports on some important probes of beyond standard model physics derived in a cosmological setting - (I) It is shown that primordial gravitational waves left over from inflation carry unique detectable CMB signatures for neutrino masses, axions and any other relativistic species that may have been present. (II) Higgs Inflation, the most popular and compelling inflation model with a higgs boson is studied next and it is shown that quantum effects have so far been incorrectly incorporated. A spurious gauge ambiguity arising from quantum effects enters the canonical prediction for observables in Higgs Inflation that must be addressed. (III) A new novel mechanism for generating the observed baryon asymmetry of the universe via decaying gravitinos is proposed. If the Supersymmetry (SUSY) breaking scale is high, then in the presence of R-parity violation, gravitinos can successfully reproduce the baryon asymmetry and evade all low energy constraints. (IV) The final chapter reports on a new completely general analysis of simplified models used in direct detection of dark matter. This is useful to explore what high energy physics constraints can be obtained from direct detection experiments.