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Volume Bragg Gratings With Complex Phase Structures: A Three-Dimensional Foundation For Laser-Beam Engineering, Lam Mach Jan 2022

Volume Bragg Gratings With Complex Phase Structures: A Three-Dimensional Foundation For Laser-Beam Engineering, Lam Mach

Electronic Theses and Dissertations, 2020-2023

Bragg diffraction is a natural phenomenon that arises from the coherent interference of scattered waves in multilayer structures with a well-defined periodicity. In practice, the physical size of these multilayer structures varies depending on the intended application, from micrometer-thick dielectric mirrors with tens of layers to centimeter-long Bragg gratings with ten-thousands of layers. The scope of this work centers around a unique class of multilayer elements developed in bulk photo-thermo-refractive (PTR) glass – the volume Bragg grating (VBG). The content of this thesis places an emphasis on the volume nature of these Bragg devices, implying a three-dimensional structure whereupon arbitrary …

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Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor, Ruqayyah Shouk Jan 2022

Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor, Ruqayyah Shouk

Electronic Theses and Dissertations, 2020-2023

By applying a dc voltage V across the stack of intrinsic Josephson junctions naturally present in the high-temperature superconductor consisting of two parts bismuth, two parts strontium, one part calcium, two parts copper, and a bit more than eight parts oxygen, several groups have been able to obtain coherent THz emission at output powers in the µW range. In order to enhance the output power well into the mW range suitable for many applications, we have studied a compact design of a stand-alone mesa array with gold layers on the top and bottom of the superconductor. In this design, an …

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Terahertz Spintronics With Antiferromagnetic Insulators, Gyan Khatri Jan 2022

Terahertz Spintronics With Antiferromagnetic Insulators, Gyan Khatri

Electronic Theses and Dissertations, 2020-2023

The existence of the THz gap in the electromagnetic spectrum is not only preventing the advancement of several technologies but also hindering research and developmental activities due to a lack of research facilities operating in the gap region. There is a plethora of materials with dynamics lying in the THz gap region whose study could potentially lead to the development of new technologies for the generation, detection, and processing of THz signals. Antiferromagnets are gaining recent interest due to their high frequency dynamics lying in the THz region, and their potential uses as active elements in THz spintronics devices have …

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Raman Excitation Laser Effects On Peak Parameters And Peak Metamorphic Temperatures Of Primitive Carbonaceous Chondrites, Amy Lebleu-Debartola Jan 2022

Raman Excitation Laser Effects On Peak Parameters And Peak Metamorphic Temperatures Of Primitive Carbonaceous Chondrites, Amy Lebleu-Debartola

Electronic Theses and Dissertations, 2020-2023

MicroRaman (µRaman) spectroscopy is often regarded as a non-destructive technique, utilized to analyze limited materials, both terrestrial and extraterrestrial. Carbonaceous chondrite meteorites are of particular interest but they are dark (low albedo) materials, and thus absorb the majority of incident visible light. Raman excitation lasers can induce considerable localized heating, even when low laser powers are used. It has been previously suggested to utilize low power lasers of =0.4 mW to minimize damaging carbonaceous samples in several fields, including Meteoritics, Geology, Chemistry, and Paleontology. Peak Metamorphic Temperatures (PMT) experienced by the meteorite can be estimated from Raman fitting parameters related …

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Cryogenic Magnetic Field Monitoring System In The Sns Neutron Edm Experiment, Umit Hasan Coskun Jan 2022

Cryogenic Magnetic Field Monitoring System In The Sns Neutron Edm Experiment, Umit Hasan Coskun

Theses and Dissertations--Physics and Astronomy

A permanent neutron electric dipole moment (nEDM), dn, would violate charge-conjugation and parity (CP) symmetry. The neutron electric dipole moment currently has a global limit of dn < 1.8 x 10-26 e cm (90% CL). This limit is intended to be improved by two orders of magnitude by the nEDM experiment at the Spallation Neutron Source (SNS nEDM), dn ~ 10-28 e cm. The magnetic field non-uniformities within the experimental region must be precisely monitored and managed in order to suppress systematic effects in the experiment caused by magnetic field gradients. The estimation of magnetic field components within …

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Jet Substructure Measurements In Proton-Proton And Proton-Gold Collisions, Isaac Arthur Mooney Jan 2022

Jet Substructure Measurements In Proton-Proton And Proton-Gold Collisions, Isaac Arthur Mooney

Wayne State University Dissertations

Observing a modification of high-energy probes in the hot nuclear environment created by ultrarelativistic heavy-ion collisions is critical for understanding the microscopic structure of the QCD medium. However, before a modification can be observed, the probes must be calibrated. For this reason, measurements of jet observables in vacuum (pp collisions) and in the presence of cold nuclear matter (pAu collisions) are presented, which will allow for future comparison of jet substructure measurements in AuAu to these baseline measurements. \parData from the STAR detector on the Relativistic Heavy Ion Collider at Brookhaven National Laboratory are used for both analyses. The pp …

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Imaging Based Beam Steering For Optical Communication And Lidar Applications, Sajad Saghaye Polkoo Jan 2022

Imaging Based Beam Steering For Optical Communication And Lidar Applications, Sajad Saghaye Polkoo

Electronic Theses and Dissertations, 2020-2023

Optical beam steering is a key component in any application that requires dynamic (i.e. realtime control) of beam propagation through free-space. Example applications include remote sensing, spectroscopy, laser machining, targeting, Lidar, optical wireless communications (OWC) and more. The pointing control requirements for many of these applications can be met by traditional mechanical steering techniques; however, these solutions tend to be bulky, slow, expensive, power hungry and prone to mechanical failures leading to short component lifetimes. Two emerging applications, Lidar imaging and OWC, truly need improved beam-steering capabilities to flourish and support the advancement of self-driving cars or relieve the congestion …

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Measurement Of (Alpha, Neutron) Reactions And Development Of Analysis Tools With The Majorana Demonstrator, Tupendra Kumar Oli Jan 2022

Measurement Of (Alpha, Neutron) Reactions And Development Of Analysis Tools With The Majorana Demonstrator, Tupendra Kumar Oli

Dissertations and Theses

Neutrinoless double-beta decay (0νββ) is a hypothetical nuclear transition which, if observed, would prove that neutrinos are Majorana particles. In addition, the decay rate could provide an effective neutrino mass scale. The decay violates lepton number conservation and could offer a potential path to explain the matter-antimatter asymmetry in the universe via leptogenesis. However, the experimental observation of this decay is very challenging and would require excellent energy resolution of detectors, low background levels, and high exposure. The MAJORANA DEMONSTRATOR experiment searches for this decay in 76Ge using P-type Point Contact (PPC) High Purity Germanium (HPGe) detectors. In addition, the …

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Development And Characterization Of Germanium Detectors For Searching Rare-Event Physics, Rajendra Panth Jan 2022

Development And Characterization Of Germanium Detectors For Searching Rare-Event Physics, Rajendra Panth

Dissertations and Theses

High-purity germanium (HPGe) detector has an excellent energy resolution and low-energy detection threshold ideal for searching rare-event physics such as dark matter and neutrinoless double beta decay searches. Understanding the electrical contact properties and the Ge detector properties is key to enhancing the use of Ge detectors for a wide range of applications. Amorphous Ge (a-Ge) is one of the passivation materials used to passivate Ge detectors, which also provides the barrier height to the charge injection. Several a-Ge contact Ge detectors were fabricated and tested at the University of South Dakota (USD) and Max-Planck-Institut (MPI) für Physik in Munich …

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Cosmogenically-Induced Backgrounds In Legend, Clay Douglas Barton Jan 2022

Cosmogenically-Induced Backgrounds In Legend, Clay Douglas Barton

Dissertations and Theses

Neutrinoless double-beta decay (0νββ) is a hypothetical nuclear decay mode. 0νββ searches are a high priority in nuclear physics. Discovery would ascertain the nature of the neutrino as the first known fundamental Majorana particle, and have far-reaching implications for physics beyond the Standard Model, including a lower bound on the effective neutrino mass scale, first direct evidence of a lepton number violating process, and insight into the matter-antimatter asymmetry in the universe. The next-generation LEGEND (Large Enriched Germanium Experiment for Neutrinoless ββ Decay) project will search for neutrinoless double-beta decay of 76Ge. LEGEND builds on infrastructure and technical expertise of …

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Evaluation Of The Potential Of Nanofluids Containing Different Ag Nanoparticle Size Distributions For Enhanced Solar Energy Conversion In Hybrid Photovoltaic-Thermal (Pvt) Applications, James Walshe, John Doran, George Amarandei Jan 2022

Evaluation Of The Potential Of Nanofluids Containing Different Ag Nanoparticle Size Distributions For Enhanced Solar Energy Conversion In Hybrid Photovoltaic-Thermal (Pvt) Applications, James Walshe, John Doran, George Amarandei

Articles

Hybridising photovoltaic and photothermal technologies into a single system that can simultaneously deliver heat and power represents one of the leading strategies for generating clean energy at more affordable prices. In a hybrid photovoltaic-thermal (PVT) system, the capability to modulate the thermal and electrical power output is significantly influenced by the spectral properties of the heat transfer fluid utilised. In this study, we report on one of the first experimental evaluations of the capability of a multimodal silver nanofluid containing various particle shapes and particle sizes to selectively modulate the solar energy for PVT applications. The diverse set of particle …

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Vortices And Dust Devils As Observed By The Mars Environmental Dynamics Analyzer Instruments On Board The Mars 2020 Perseverance Rover, Brian Jackson Jan 2022

Vortices And Dust Devils As Observed By The Mars Environmental Dynamics Analyzer Instruments On Board The Mars 2020 Perseverance Rover, Brian Jackson

Physics Faculty Publications and Presentations

An important and perhaps dominant source of dust in the Martian atmosphere, dust devils play a key role in Mars' climate. Data sets from previous landed missions have revealed dust devil activity, constrained their structures, and elucidated their dust-lifting capacities. However, each landing site and observational season exhibits unique meteorological properties that shape dust devil activity and illuminate their dependence on ambient conditions. The recent release of data from the Mars Environmental Dynamics Analyzer (MEDA) instrument suite on board the Mars 2020 Perseverance rover promises a new treasure trove for dust devil studies. In this study, we sift the time …

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Collision-System And Beam-Energy Dependence Of Anisotropic Flow Fluctuations, Star Collaboration Jan 2022

Collision-System And Beam-Energy Dependence Of Anisotropic Flow Fluctuations, Star Collaboration

Physics and Astronomy Faculty Publications

Elliptic flow measurements from two-, four-, and six-particle correlations are used to investigate flow fluctuations in collisions of U+U at √𝑠NN=193  GeV, Cu+Au at √𝑠NN=200  GeV and Au+Au spanning the range √𝑠NN=11.5–200  GeV. The measurements show a strong dependence of the flow fluctuations on collision centrality, a modest dependence on system size, and very little if any, dependence on particle species and beam energy. The results, when compared to similar LHC measurements, viscous hydrodynamic calculations, and trento model eccentricities, indicate that initial-state-driven fluctuations predominate the flow fluctuations generated in the collisions studied.

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Differential Measurements Of Jet Substructure And Partonic Energy Loss In Au + Au Collisions At √𝑠𝑁⁢𝑁=200 Gev, Star Collaboration Jan 2022

Differential Measurements Of Jet Substructure And Partonic Energy Loss In Au + Au Collisions At √𝑠𝑁⁢𝑁=200 Gev, Star Collaboration

Physics and Astronomy Faculty Publications

The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in 𝑝+𝑝 and Au+Au collisions at √𝑠𝑁⁢𝑁 =200GeV. The substructure observables include SoftDrop groomed momentum fraction (𝑧𝑔), groomed jet radius (𝑅𝑔), and subjet momentum fraction (𝑧SJ) and opening angle (𝜃SJ). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for 𝑝+𝑝 collisions and are compared to leading-order Monte Carlo models. The subjet 𝜃SJ distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in Au+Au …

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Disappearance Of Partonic Collectivity In √Snn = 3 Gev Au+Au Collisions At Rhic, Star Collaboration Jan 2022

Disappearance Of Partonic Collectivity In √Snn = 3 Gev Au+Au Collisions At Rhic, Star Collaboration

Physics and Astronomy Faculty Publications

We report on the measurements of directed flow v1 and elliptic flow v2 for hadrons (π±, K ±, K 0 S , p, φ, Λ and Ξ−) from Au+Au collisions at √sNN = 3 GeV and v2 for (π±, K ±, p and p) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the number-of-constituent-quark (NCQ) scaling holds, at 3 GeV the v2 at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the v1 slopes at midrapidity for almost all observed hadrons are found to be …

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Observation Of Quantum Oscillations In The Low Temperature Specific Heat Of Smb6, Patrick Labarre, A. Rydh, Joyce E. Palmer-Fortune, J. A. Frothingham, Scott T. Hannahs, Arthur P. Ramirez, Nathanael Fortune Jan 2022

Observation Of Quantum Oscillations In The Low Temperature Specific Heat Of Smb6, Patrick Labarre, A. Rydh, Joyce E. Palmer-Fortune, J. A. Frothingham, Scott T. Hannahs, Arthur P. Ramirez, Nathanael Fortune

Physics: Faculty Publications

We report measurements of the low-temperature specific heat of Al-flux-grown samples of SmB6 in magnetic fields up to 32 T. Quantum oscillations periodic in 1/H are observed between 8 and 32 T at selected angles between [001] and [111]. The observed frequencies and their angular dependence are consistent with previous magnetic torque measurements of SmB6 but the effective masses inferred from Lifshitz-Kosevich theory are significantly larger and closer to those inferred from zero-field specific heat. Our results are thus consistent with a bulk density of states origin for the oscillations.

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The Role Of Action Potential Changes In Depolarization-Induced Failure Of Excitation Contraction Coupling In Mouse Skeletal Muscle, Xueyong Wang, Murad Nawaz, Chris Dupont, Jessica H. Myers, Steve R.A. Burke, Roger A. Bannister, Brent D. Foy, Andrew A. Voss, Mark M. Rich Jan 2022

The Role Of Action Potential Changes In Depolarization-Induced Failure Of Excitation Contraction Coupling In Mouse Skeletal Muscle, Xueyong Wang, Murad Nawaz, Chris Dupont, Jessica H. Myers, Steve R.A. Burke, Roger A. Bannister, Brent D. Foy, Andrew A. Voss, Mark M. Rich

Physics Faculty Publications

Excitation-contraction coupling (ECC) is the process by which electrical excitation of muscle is converted into force generation. Depolarization of skeletal muscle resting potential contributes to failure of ECC in diseases such as periodic paralysis, intensive care unit acquired weakness and possibly fatigue of muscle during vigorous exercise. When extracellular K+ is raised to depolarize the resting potential, failure of ECC occurs suddenly, over a narrow range of resting potentials. Simultaneous imaging of Ca2+ transients and recording of action potentials (APs) demonstrated failure to generate Ca2+ transients when APs peaked at potentials more negative than –30mV. An AP property that closely …

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Investigation Of Thz Absorptive Signatures In Opioids, Weidong Zhang, Alexei Bykhovski, Elliott R. Brown Jan 2022

Investigation Of Thz Absorptive Signatures In Opioids, Weidong Zhang, Alexei Bykhovski, Elliott R. Brown

Physics Faculty Publications

We investigate the possibility of sensing opioid drugs, such as fentanyl, by their THz electromagnetic signatures. The methods include both computer modeling and experiments. Molecular dynamics simulations predict that fentanyl should display THz resonances, with several of them occurring below 1.0 THz; the lowest one is at around 0.337 THz (337 GHz). Spectroscopy measurements were conducted on oxycodone, which was used as a surrogate for fentanyl. They display vibrational absorption resonances between ∼1.4 and 1.6 THz.

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A Progressive Learning Strategy For Large-Scale Glacier Mapping, Zhiyuan Xie, Umesh K. Haritashya, Vijayan K. Asari Jan 2022

A Progressive Learning Strategy For Large-Scale Glacier Mapping, Zhiyuan Xie, Umesh K. Haritashya, Vijayan K. Asari

Electrical and Computer Engineering Faculty Publications

In recent years, the worldwide temperature increase has resulted in rapid deglaciation and a higher risk of glacier-related natural hazards such as flooding and debris flow. Due to the severity of these hazards, continuous observation and detailed analysis of glacier fluctuations are crucial. Many such analyses require an accurately delineated glacier boundary. However, the complexity and heterogeneity of glaciers, particularly debris-covered glaciers (DCGs), poses a challenge for glacier mapping when using conventional remote sensing or machine-learning techniques. Some examples exist about small-scale automated glacier mapping, but large or regional-scale mapping is challenging. Previously, a deep-learning-based approach named GlacierNet2 had been …

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Enhanced Study Of Complex Systems By Unveiling Hidden Symmetries With Dynamical Visibility, Nhat Vu Minh Nguyen Jan 2022

Enhanced Study Of Complex Systems By Unveiling Hidden Symmetries With Dynamical Visibility, Nhat Vu Minh Nguyen

2022 Symposium

One of the great challenges in complex and chaotic dynamics is to reveal its deterministic structures. These temporal dynamical structures are sometimes a consequence of hidden symmetries. Detecting and understanding them can allow the study of complex systems even without knowing the full underlying mathematical description of the system. Here we introduce a new technique, called Dynamical Visibility, that quantifies temporal correlations of the dynamics based upon some symmetry conditions. This visibility measures the departure of the dynamics from internal symmetries. We apply this technique to well-known chaotic systems, such as the logistic map and the circle map, as well …

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Uncooled Microbolometer Imaging Systems For Machine Vision, Robert Grimming Jan 2022

Uncooled Microbolometer Imaging Systems For Machine Vision, Robert Grimming

Electronic Theses and Dissertations, 2020-2023

Over the last 20 years, the cost of uncooled microbolometer-based imaging systems has drastically decreased while performance has increased. In the simplest terms, the figure of merit for these types of thermal detectors is given in terms of the τ-NETD product, the combination of the thermal time constant and the noise equivalent temperature difference. Considering these factors, optimal system design parameters are investigated to maximize visual information content. This dissertation focuses on improving scene information in the longwave infrared (LWIR) spectrum that has had its validity and quality degraded by noise, blur, and reflected radiance. Taken together, noise and blur …

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A Modulated Structure Derived From The Xa-Type Mn2Rusn Heusler Compound, Xingzhong Li, Wen-Yong Zhang, Ralph Skomski, David J. Sellmyer Jan 2022

A Modulated Structure Derived From The Xa-Type Mn2Rusn Heusler Compound, Xingzhong Li, Wen-Yong Zhang, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

A modulated structure derived from the inverse Heusler phase (the XA-type and the disordered variant L21B-type) has been observed in rapidly quenched Mn2RuSn ribbons. The powder X-ray diffraction pattern of the quenched ribbons can be indexed as an L21B-type structure. Electron diffraction patterns of the new structure mostly resemble those of the XA-type (and the disordered variant L21B-type) structure and additional reflections with denser spacing indicate a long periodicity. Orthogonal domains of the modulated structure were revealed by a selected-area electron diffraction pattern and the corresponding dark-field transmission electron microscopy images. The structure was …

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Localization Effects And Anomalous Hall Conductivity In A Disordered 3d Ferromagnet, Paul M. Shand, Y. Moua, G. Baker, Shah R. Valloppilly, Pavel V. Lukashev, Parashu Kharel Jan 2022

Localization Effects And Anomalous Hall Conductivity In A Disordered 3d Ferromagnet, Paul M. Shand, Y. Moua, G. Baker, Shah R. Valloppilly, Pavel V. Lukashev, Parashu Kharel

Nebraska Center for Materials and Nanoscience: Faculty Publications

We have prepared the Heusler alloy CoFeV0.5Mn0.5Si in bulk form via arc melting. CoFeV0.5Mn0.5Si is ferromagnetic with a Curie temperature of 657 K. The longitudinal resistivity exhibits a minimum at 150 K, which is attributable to competition between quantum interference corrections at low temperatures and inelastic scattering at higher temperatures. The magnetoresistance (MR) is positive and nearly linear at low temperatures and becomes negative at temperatures close to room temperature. The positive MR in the quantum correction regime is evidence of the presence of the enhanced electron interaction as a contributor to …

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Patterned Liquid Crystal Devices For Near-Eye Displays, Kun Yin Jan 2022

Patterned Liquid Crystal Devices For Near-Eye Displays, Kun Yin

Electronic Theses and Dissertations, 2020-2023

As a promising next-generation display, augmented reality (AR) and virtual reality (VR) have shown attractive features and attracted broad interests from both academia and industry. Currently, these near-eye displays (NEDs) have enabled numerous applications, ranging from education, medical, entertainment, to engineering, with the help of compact and functional patterned liquid crystal (LC) devices. The interplay between LC patterns and NEDs stimulates the development of novel LC devices with unique surface alignments and volume structures, which in turn feedback to achieve more compact and versatile NEDs. This dissertation will focus on the patterned LC with applications in NEDs. Firstly, we propose …

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Physics And Applications Of Space-Time Wave Packets, Murat Yessenov Jan 2022

Physics And Applications Of Space-Time Wave Packets, Murat Yessenov

Electronic Theses and Dissertations, 2020-2023

Space-time wave packets (STWP) constitute a broad class of pulsed optical fields that are rigidly transported in linear media without diffraction or dispersion, and are therefore propagation-invariant in absence of optical nonlinearities or waveguiding structures. Such wave packets exhibit unique characteristics, such as controllable group velocities in free space and exotic refractive phenomena. At the root of these behaviors is a fundamental feature underpinning STWP: their spectra are not separable with respect to the spatial and temporal degrees of freedom. Indeed, the spatio-temporal structure is endowed with angular dispersion, in which each spatial frequency is associated with a single prescribed …

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Diffractive Liquid Crystal Optical Elements For Near-Eye Displays, Jianghao Xiong Jan 2022

Diffractive Liquid Crystal Optical Elements For Near-Eye Displays, Jianghao Xiong

Electronic Theses and Dissertations, 2020-2023

Liquid crystal planar optics (LCPO) with versatile functionalities is emerging as a promising candidate for overcoming various challenges in near-eye displays, like augmented reality (AR) and virtual reality (VR), while maintaining a small form factor. This type of novel optical element exhibits unique properties, such as high efficiency, large angular/spectral bandwidths, polarization selectivity, and dynamic modulation. The basic molecular configuration of these novel reflective LCPO is analyzed, based on the simulation of molecular dynamics. In contrast to previously assumed planar-twist structure, our analysis predicts a slanted helix structure, which agrees with the measured results. The optical simulation model is established …

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Development Of Holographic Phase Masks For Wavefront Shaping, Nafiseh Mohammadian Jan 2022

Development Of Holographic Phase Masks For Wavefront Shaping, Nafiseh Mohammadian

Electronic Theses and Dissertations, 2020-2023

This dissertation explores a new method for creating holographic phase masks (HPMs), which are phase transforming optical elements holographically recorded in photosensitive glass. This novel hologram recording method allows for the fast production of HPMs of any complexity, as opposed to the traditional multistep process, which includes the design and fabrication of a master phase mask operating in the UV region before the holographic recording step. We holographically recorded transmissive HPMs that are physically robust (they are recorded in a silicate glass volume), can handle tens of kilowatts of continuous wave (CW) laser power, are un-erasable, user defined, require no …

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Characterizing The Particle Size Distribution In Saturn's Rings Using Cassini Uvis Stellar Occultation Data, Stephanie Eckert Jan 2022

Characterizing The Particle Size Distribution In Saturn's Rings Using Cassini Uvis Stellar Occultation Data, Stephanie Eckert

Electronic Theses and Dissertations, 2020-2023

NASA's Cassini mission to Saturn revolutionized modern understanding of the planet's vast and intricate ring system. We use stellar occultation data from Cassini's UVIS High Speed Photometer (HSP) to characterize the particle size distribution in the rings with two methods. First, we discern the sizes of the smallest particles at ring edges by forward-modeling observed diffraction signatures which appear as spikes in the signal, the shape and amplitude of which depends on the size and abundance of the smallest particles. We then probe the upper end of the size distribution using occultation statistics. Although the distribution of photon counts in …

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Control Of Coherence In Attosecond Atomic Ionization, Saad Mehmood Jan 2022

Control Of Coherence In Attosecond Atomic Ionization, Saad Mehmood

Electronic Theses and Dissertations, 2020-2023

The motion of electrons in atoms, molecules, and in condensed matter unfolds on a time scale from the attosecond (1 as = 10-18 s) to several femtoseconds (1 fs= 10-15 s). The advent of attosecond light pulses has opened the way to the time-resolved study of electronic motion and of ionization processes using pump-probe spectroscopy. In this thesis, we examine three aspects of the ionization dynamics in poly-electronic atoms: i) the coherence of the emerging charged fragments, ii) two-photon ionization pathways, and iii) the reconstruction of photoionization amplitudes from experimental observable. We focus on the role of autoionizing states and …

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Apparatus Improvement And Characterisation For Experiments On Ultra-Cold Plasmas., Jakub Bystrický Jan 2022

Apparatus Improvement And Characterisation For Experiments On Ultra-Cold Plasmas., Jakub Bystrický

Honors Theses

Apparatus for creating ultra-cold neutral plasmas (UNPs) was improved and data on plasma expansion was collected. We increase the trapping efficiency of a quadrupole magneto-optical trap (MOT) by installing a tapered amplifier to increase the power of the cooling laser used to trap atoms. We achieve an improvement in density of trapped atoms from 1 x 1010 cm-3 to 2.5 - 4.5 x 1010 cm-3. In addition, to improve precision and decrease systematic error, the magnetic field induced by inductive current in the MOT's anti-helmholtz coils was suppressed. This was achieved by installing a KEPCO …

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