Mountain Scholar :: Browsing by Author "Menoni, Carmen S., committee member"

Browsing by Author "Menoni, Carmen S., committee member"

Now showing 1 - 20 of 21

Open Access
Beam-driven co-linear X-band energy booster (CXEB) for a compact FEL
(Colorado State University. Libraries, 2017) Sipahi, Taylan, author; Milton, Stephen V., advisor; Biedron, Sandra G., advisor; Menoni, Carmen S., committee member; Brandl, Alexander, committee member
Achieving compact, efficient and cost-effective particle accelerators is overall major goal of the community to help propel future projects forward. In the realm of particle accelerators that enable both the high-energy physics and light-source communities, achieving the highest energy with the brightest beams in the shortest distance is most important and it is here where a paradigm shift is needed. Achieving high energies in a shorter distance (higher gradients) than presently achievable is important for even small laboratory settings, i.e. universities or industries desiring light sources, as it would permit an affordable cost. While there are several methods being considered for compact, efficient particle accelerators, it was chosen to pursue a unique application of X-band (11.7 GHz) RF cavities as they are capable, due to their intrinsic high shunt impedance, of generating high gradients with relatively low input power. A novel idea that can push the Colorado State University's (CSU) Advanced Beam Laboratory's beam energy up from the present 6 MeV to over 32.6 MeV, without the need of additional, expensive X-band power sources was conceived. The concept is called the co-linear X-band energy booster (CXEB) and it relies on the use of X-band structures powered by the beam that is already available from the facility's existing L-band (1.3 GHz) linear accelerator system. Also, this proposed system can provide electron beam to a compact free-electron laser (FEL) at CSU. The overall FEL system is quite compact and comparatively cost-effective given the fact that the existing L-band infrastructure already exists.
Open Access
Changing dogma regarding the conformation of electron transferring menaquinone (MK)
(Colorado State University. Libraries, 2017) Magallanes, Estela Serrano, author; Crans, Debbie C., advisor; Menoni, Carmen S., committee member; Tsunoda, Susan, committee member
Menaquinone-9 (MK-9) is the natural substrate containing a naphthoquinone and an isoprenyl side-chain with nine isoprene units that carry out the electron transfer for the Mycobacterium tuberculosis. We present studies aiming to understand the chemical and biochemical properties of hydrophobic MK molecules. Specifically, we are investigating the MK derivative with two isoprene units, MK-2, because it provides us with the base structure containing the naphthoquinone unit and the isoprene side-chain. Its synthesis is relatively simple because the precursors are commercially available, which allows for large scale preparation and detailed characterization of the molecular structure under different conditions. Using 1D and 2D 1H NMR studies we are establishing that MKs have different conformations depending on the specific environmental conditions. Similarly, we show using 1H-1H 2D NOESY NMR studies that the association of MK with the surfactant- water interface of reverse micelles, which is a model membrane system, modify the conformation of the menaquinone derivative. Finally, the redox potentials of MK-2 was measured in the three different solvents (DMSO, CH3CN and pyridine). We hypothesize that the redox potential is correlated to the conformational of the MK. We observed that the redox potentials varied with solvent. The observed folded structures of MK derivatives stand in contrast to the linear conformation shown in life science text books.
Open Access
Characterization of laser-produced plasmas as light sources for extreme ultraviolet lithography and beyond
(Colorado State University. Libraries, 2019) Yin, Liang, author; Rocca, Jorge J., advisor; Menoni, Carmen S., committee member; Marconi, Mario C., committee member; Yalin, Azer, committee member
Lithography is a critical process in the fabrication of integrated circuits. The continuous increase in computing power for more than half a century has depended in the ability to print smaller and smaller features, which has required the use of light sources operating at increasingly shorter wavelengths. There is keen interest in the development of high-power light sources for extreme ultraviolet (EUV) lithography at λ=13.5 nm and future beyond extreme ultraviolet (BEUV) lithography near λ=6.7 nm. The work conducted in this dissertation has characterized aspects of laser-produced plasmas (LPPs) that serve as light sources for EUV / BEUV lithography. The laser pulse shape dependence of the conversion efficiency of λ=1.03 μm laser into in-band 13.5 nm EUV emission in a Sn LPP was studied as a function of laser pulse shape and durations. Laser pulses of arbitrary temporal shape with variable energy and pulse widths were generated using a programmable pulse synthesizer based on a diode-pumped chirped pulse amplification Yb: YAG laser. The pulse synthesizer is based on wave front splitting and pulse stacking for the generation of arbitrary shape laser pulses of Joule-level energy. Pulses ranging from hundreds of ps to several ns were generated with a single laser. The measurements showed the CE favors the use of nearly square pulses of duration longer than 2 ns, in agreement with hydrodynamic/atomic physics simulations. A significant increase in CE was observed when Q-switched pulses were substituted by square pulses of similar duration. Conditions were observed at which the EUV pulse duration significantly outlasts the laser pulse in the direction normal to the target surface, in contrast at grazing angles the measured EUV pulse duration is shorter and similar to the laser pulse duration. The physics leading to this angular anisotropy is discussed, along with the spectroscopic characterization of EUV emission and at-wavelength images that characterize the source size. Another aspect of this dissertation includes a comprehensive study of the emission from Gd and Tb LPPs in the λ=6.5 - 6.7 nm region. BEUV emission spectra were measured as a function of laser pulse duration (120 ps - 4 ns), emission angle, and spatial location within the plasma. At-wavelength images of the BEUV emitting plasma region were obtained as a function of irradiation parameters. The peak of the emission spectrum was observed to broaden and to shift to longer wavelengths as the laser pulses are shortened from ns to hundreds of ps. Transient self-consistent hydrodynamic/atomic physics simulations show that the picosecond irradiation creates significantly hotter plasmas in which the dominant emission originates from more highly ionized species. Gd LPP emission driven by nanosecond laser pulses best matched the reflectivity band of our La/B4C mirrors. Spatially resolved spectra of the Gd LPP were acquired for different laser parameters and were compared to simulations. The CE into in-band BEUV emission was determined by integrating angularly resolved measurements obtained using an array of calibrated energy monitors. A maximum CE of 0.47% / 0.45% for the Gd / Tb LPPs was obtained within a 0.6% bandwidth. The results are of potential interest BEUV lithography.
Open Access
Coherent EUV lithography with table-top laser
(Colorado State University. Libraries, 2012) Urbanski, Lukasz, author; Marconi, Mario C., advisor; Bartels, Randy A., committee member; Menoni, Carmen S., committee member; Putkaradze, Vakhtang, committee member
This dissertation describes alternative techniques of optical lithography in the extreme ultraviolet (EUV) region of the electromagnetic spectrum. The pursuit of the Moore's law forces the semiconductor industry to transfer to shorter wavelengths of illumination in projection lithography. The EUV light is perhaps the most viable candidate for the next generation integrated circuits printing. However, the EUV lithography encounters many challenges associated with the very nature of the light it is using. Many novel techniques and materials are being applied at the same time in the lithography process. As such the process itself is far from being reliable. Thus the solutions are being sought among the alternative methods of printing in the nano-scale that would aid to temporarily overpass the resolution gap. This thesis contains a description of several alternative techniques of nanofabrication with the EUV light. For each method the analytical description is provided that is further corroborated with numerical model simulations. Furthermore every technique presented here is verified experimentally. The proposed techniques are discussed in terms of their applicability as a self consistent nanofabrication process. The illumination source for all the techniques presented is the capillary discharge laser (CDL) that was engineered at Colorado State University; it is characterized in the chapter 2 of this dissertation. The CDL is an unbeatable table-top source of high average power illumination with the degree of coherence that is sufficient for coherent nano-scale printing. A separate chapter is dedicated to the description of the fabrication protocol of a diffractive optical element (the mask) used in the EUV nanopatterning techniques. This particular chapter is intended to serve as a potential reference manual for the EUV masks fabrication. The coherent EUV nanofabrication techniques described in the chapters 4-6 are: the holographic projection lithography, generalized Talbot imaging (GTI), and de-magnified generalized Talbot imaging. A separate chapter is devoted to the defect tolerance property of the GTI technique.
Open Access
Continuous-wave cavity ring down spectroscopy sensor for Hall thruster erosion measurement
(Colorado State University. Libraries, 2011) Tao, Lei, author; Yalin, Azer P., advisor; Marchese, Anthony J., committee member; Menoni, Carmen S., committee member; Williams, John D., committee member
Hall thruster and other Electric propulsion (EP) devices have become appealing alternatives to traditional chemical propulsion thrusters for space applications due to this high specific impulse (Isp), which allows high fuel efficiency. However, the uncertainty of the lifetime for Hall thruster hinders its development in future applications requiring a long operational time (several thousands of hours). Sputter erosion of boron nitride (BN) acceleration channel wall is principal lifetime limitation for Hall thrusters. The sputtered particles can redeposit causing a critical contamination effect. There is an urgent need for improved experimental tools to understand the BN sputter erosion process and lifetime assessment for Hall thrusters. The present research applies continuous wave cavity ring down Spectroscopy (CW-CRDS) as a diagnostic tools to study the sputter erosion process for Hall thrusters. Two CW-CRDS erosion sensors have been developed for in situ monitoring of sputtered manganese (Mn) and BN. As a stepping stone towards BN detection, a Mn erosion sensor was first developed. This sensor is based upon detection of Mn atoms via an absorption line from ground state at a wavelength of 403.076 nm. Measurements of sputtered Mn atom number density and its hyperfine structure are presented. Additionally, end-point detection has been done for a multilayer target, which can be potentially applied to the industrial sputtering systems. The same system has also been applied for detecting eroded atoms from the acceleration channel wall in an anode layer type Hall thruster. The results show the validity of the CW-CRDS erosion sensor for Hall thruster lifetime estimation. A BN erosion sensor has also been developed for the detection of sputtered boron atoms from Hall thrusters by probing atomic absorption lines of boron (250 nm) with CW-CRDS. A photonic crystal fiber was used to couple the ultraviolet laser light to the cavity within the vacuum chamber. The experimental detection limits and signal-to-noise values show potential for Hall thruster BN erosion studies. Finally, the velocity distributions of sputtered boron atoms at different ion energies were measured with laser induced fluorescence (LIF). These velocity distribution are necessary for interpretation of signals from the BN erosion sensor.
Open Access
Development of a Hall thruster test facility
(Colorado State University. Libraries, 2012) Leach, Randolph W., author; Yalin, Azer P., advisor; Williams, John D., committee member; Menoni, Carmen S., committee member
The present thesis details the development of a Hall thruster test facility for low power (<600 W) thrusters. The facility is based on a vacuum chamber, two standard cryogenic pumps and one modified cryogenic pump. The modified cryogenic pump is outfitted with custom built internal components, which are referred to as a cryosail. Estimation as well as measurement of pumping speeds of the two cryogenic pumps and cryosail were conducted resulting in an overall measured pumping speed of 10,500 L/s for Xenon. The ultimate base pressure of the system was 4x10-8 Torr. A SPT-70 Hall thruster was operated at various conditions and set points to include fine tuning the current to the magnets to find efficient thruster operation. Ion current densities at points downstream of the thruster's exit plane were examined by a Faraday probe. Although operation at nominal thruster operating conditions was not achieved, likely due to a problem with magnetic coils, the thruster operation did allow preliminary measurements by Cavity Ring-Down Spectroscopy of sputtered Boron originating from the thruster channel wall.
Open Access
Development of a high energy TI:Sapphire laser for the excitation of extreme ultraviolet lasers
(Colorado State University. Libraries, 2011) Martz, Dale Herman, author; Rocca, Jorge J., advisor; Lee, Siu Au, committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee member
This dissertation describes the design, construction and characterization of a high energy chirped-pulse amplification Titanium-Sapphire laser system for the excitation of Extreme Ultraviolet (EUV) lasers. Compact EUV lasers have made possible nano-scale imaging, dense plasma diagnostics and photo-chemistry and photo-physics studies. They also have the potential to make possible a variety of new studies of surfaces and materials and enable the development of unique metrology and processing tools for industry. The components developed to realize high energy operation of the Titanium-Sapphire laser include the development of a Nd:Glass zig-zag slab pump laser and novel 800 nm multi-layer dielectric diffraction gratings for picosecond compression. The Titanium-Sapphire laser was used to pump several table-top EUV lasers. Increased average power operation of a 13.9 nm nickel-like silver laser generating 20 uW was demonstrated. This is the highest average power obtained from a compact EUV laser to date. Injection seeding of the 13.9 nm EUV amplifier produced laser beams with greatly improved beam characteristics which includes a large reduction in beam divergence and a near Gaussian far-field profile. The laser was also used to pump a gain-saturated table-top laser at 10.9 nm in nickel-like tellurium.
Open Access
Development of a high-voltage laser triggered switch facility including initial optical and electrical diagnostics
(Colorado State University. Libraries, 2019) Rose, Charles E., author; Yalin, Azer P., advisor; Menoni, Carmen S., committee member; Yourdkhani, Mostafa, committee member
Pulsed power programs have been part of the United States strategic plan to address the nation's energy and defense needs since the 1960s. With escalating energy demand, one of the greatest challenges of our time is to develop clean and reliable energy sources with controlled fusion being an exciting and favorable candidate. Developing this technology has been an arduous and taxing effort with a breakthrough (supposedly) coming just around the corner for decades. Arguably, one of the leading testbeds for fusion research is Sandia National Laboratories (SNL) Z machine which is part of SNL's pulsed power program. The Z machine can create fusion-like conditions and allows the global research community to investigate pathways forward to a viable fusion reactor. Integral to developing future pulsed power technology and the next Z-pinch style machines, high voltage spark gap switches are an active research area and the focus of this thesis.
Open Access
Fast electronic driver for optical switches
(Colorado State University. Libraries, 2012) Woolston, Mark R., author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Menoni, Carmen S., committee member; Yalin, Azer P., committee member
Electronically controlled optical switches are critical components in many optical systems, including pulsed lasers. Solid-state optical switches based upon the Pockels effect are widely utilized in research and industry, however Pockels cells require electronic drivers capable of switching several kilovolts quickly and cleanly. This thesis reviews Pockels cell designs and their typical applications in laser systems, discusses common drive circuit topologies found in literature, and describes the development of a fast, stable electronic driver for half-wave congured Pockels cell optical switches. In a crowded optical environment, it is frequently desirable to locate the Pockels cell at some distance from the driver electronics. The driver was developed to be capable of 1.4 ns optical transition times when connected to a 6 pF Pockels cell via 1.2 meters of 50 ohm coaxial cable. The driver is designed to operate in colliding-pulse mode at 6-8 kV, with 80 ampere typical switch currents. Total switch propagation delay is less than 100 ns, and thermal drift has been measured at less than 50ps/C°. These pulsers are currently used to drive Pockels cells in colliding pulse mode in pulse picking and slicing applications where optical rise times of < 2 ns and low drift are needed. Novel non-invasive diagnostic techniques for measuring and graphing pulse propagation in a repeatable manner along collapsing avalanche transistor chains are presented.
Open Access
Gain-saturated repetetive soft X-ray lasers with wavelengths spanning 9-30 nm and lasing down to 7.4 nm
(Colorado State University. Libraries, 2011) Alessi, David Alan, author; Rocca, Jorge J., advisor; Lee, Siu Au, committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee member
This dissertation describes the development of table-top soft X-ray lasers with wavelengths ranging from 30 nm to 7.4 nm. The laser transisitons occur within collisionally excited states of nickel-like and neon-like ions which are created from laser ablation of solid targets. A Nd:glass slab laser system was developed to provide 20J (and then upgraded to 40J) of laser light at 527 nm for pumping a table-top chirped pulse amplification Ti:sapphire laser. With this increase in pump energy, the Ti:sapphire system is capable of producing 12J uncompressed laser pulses at a 1Hz repetition rate. Stretched and compressed pulses from this Ti:sapphire laser system operating near 800 nm are used to both ionize the material to a high degree and heat the free electrons in these plasmas to temperatures required for high gain. Simulations from a 1.5D hydrodynamic/atomic model indicate a peak gain of 90 cm-1 for the 8.8 nm laser transition in nickel-like lanthanum is reached with an electron temperature of ~850 eV and a density of 6×1020 cm-3. By using the grazing incidence pumping geometry, gain saturated operation was demonstrated in the 2p53p 1S0 →2p5 3s 1P1 transition of neon-like titanium (λ = 32.6 nm) and vanadium (λ = 30.4 nm), as well as in the 3d94d1S0→3d9 4p1P1 transition in nickel-like tellurium (λ = 10.9 nm) and lanthanum (λ = 8.8 nm). Strong lasing was also demonstrated in the same neon-like transition in chromium (λ = 28.6 nm), as well as the same nickel-like transition in cerium (λ = 8.5 nm), praseodymium (λ = 8.2 nm), neodymium (λ = 7.9 nm) and samarium (λ = 7.4 nm). This is the first demonstration of the generation of bright gain-saturated sub-9-nm wavelengths with a table-top laser operating at 1-Hz repetition rate. The short wavelength, microjoule pulse energy, picosecond pulse duration and repetitive operation of these lasers will enable new applications such as sequential imaging of ultrafast nano-scale dynamic phenomena to be realized on a table top.
Open Access
Improved resolution and speed in nonlinear microscopy
(Colorado State University. Libraries, 2010) Masihzadeh, Omid, author; Bartels, Randy A., advisor; Roberts, Jacob Lyman, committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee member
Optical microscopy is an important tool for biomedical research. New techniques for microscopy enable new capabilities for studying biological systems. Moreover, in optical microscopy, the polarization state of the focal field strongly influences the images formed due to the impact of focal spot size, adjusting the relative strength and phase of both transverse and longitudinal field components, and manipulating inter- action with the sample under study. In particular, coherent nonlinear microscopies, such as third harmonic generation (THG), and second harmonic generation (SHG), offer rich possibilities for new control over the imaging process. In the first part of this dissertation, I demonstrate that control over the spatial polarization state of the focal field can be used to improve the spatial resolution in a laser-scanning THG microscopy. First, we show a detailed design of our nonlinear scanning microscope, then we introduce a non-iterative algorithm for measurement of spatially inhomogeneous polarization distributions in third-harmonic generation microscopy. We also, show control of spatial polarization state of the focal field through imaging of a spatial light modulator to the focus of a microscope objective. Then, we introduced a novel technique for enhancing resolution in THG microscopy, through spatial polarization shaping at the focal field. In the second part of this dissertation, we show an alternative method to laser- scanning nonlinear microscopy in biological tissue, namely, nonlinear holographic microscopy. First, we introduce the foundation of nonlinear holographic microscopy by reviewing linear off-axis holography. We start by introducing digital recording in off- axis holography, its limitations, and show how through holography we can obtain 3-D images from 2-D data. We then explore numerical reconstruction of the object field from the recorded holograms. Finally, we expand this technique to SHG nonlinear holographic microscopy to construct 3-dimensional images of biological tissues.
Open Access
Improvement in dye sensitized solar cell efficiency through functionalization of redox mediators and passivation of the photoanode using a home-built atomic layer deposition system
(Colorado State University. Libraries, 2017) Thomas, Joshua D., author; Prieto, Amy L., advisor; Fisher, Ellen R., committee member; Menoni, Carmen S., committee member; Sampath, Walajabad S., committee member
The efficiency of dye sensitized solar cells (DSSCs) is driven based on the contributions of a vast array of kinetic and thermodynamic processes which must all function in sync with one another. The redox mediator factors into a majority of these processes and thus its proper function is vital to adequate function of the DSSC as a whole. The function of the redox mediator can be altered in two ways: changing the identity of the redox couple used and modifying one of the components which the redox couple is interacting with. Herein, both methods have been performed to optimize the properties and processes involved in efficient DSSC function. Several cobalt bipyridine coordination complex type mediators have been synthesized and differentiated through the modification of the ligand structure. The purpose of the modification was to generate complexes with more positive redox potentials to increase the open circuit voltage of the cells. Subsequently, attempts were made to further modify the ethyl ester substituted ligands which yielded the highest redox potential in order to provide higher stability for the resulting mediator. While the outcome of the synthesis was unsuccessful at this point, promising results have been shown. Further, an apparatus was constructed in order to cheaply perform atomic layer deposition of aluminum oxide on the surface of the mesoporous titanium dioxide photoanodes for DSSCs. Atomic layer deposition has been shown to reduce the rate of recombination with the oxidized mediator. In this case, improvement in the open circuit voltage of the cell was shown. However, the overall improved performance of the DSSCs shown in the literature could not be replicated. It is hoped that more high resolution analytical techniques could be used to elucidate the deficiencies still present in the use of this technique.
Open Access
Local structure studies in functional materials and self-regulated learning interventions in general chemistry courses
(Colorado State University. Libraries, 2020) Paecklar, Arnold A., author; Neilson, James R., advisor; Reynolds, Melissa M., advisor; Rhodes, Matthew G., committee member; Finke, Richard G., committee member; Menoni, Carmen S., committee member
The first part of this dissertation is dedicated to understanding how the origin of the chemical and physical properties of functional materials is correlated to their structure. The standard approach to determining the structure of a crystalline material is to measure the average structure of regular, repeating units. However, this approach is not sufficient for more complex compounds including disorder. Hence, to fully understand the structure-property relationships of these advanced materials, identifying the local structure is crucial. This work focuses on designing approaches for optimizing the measurement of local structure data based on X-ray and neutron total scattering techniques as well as computational approaches for analyzing and understanding these data sets. The main focus lies in designing a novel system for collecting neutron total scattering data involving the controlled exposure of gasses to solid samples. Combining this setup with a Steady-State Isotopic Transient Kinetic Analysis system further enables the collection of kinetics data simultaneously with the structural data. This system was successfully used for studying and identifying the adsorption and reaction sites in porous materials such as zeolites and metal-organic frameworks. The disorder in these systems is based on the adsorbate which is a major contributor to the structure. However, there are also materials in which a single solid phase itself contains all the disorder. Some examples for disordered materials, covered in this work, are semiconducting perovskite materials with the general formula A2BX6. Computational approaches ranging from single to high-throughput Reverse Monte Carlo modeling were developed to gain more insight into anharmonicity and the interplay of the local structural features. Understanding how these specific local structural features influence desired physical properties will help guide the design of new materials covering a wide range of applications ranging from photovoltaics to biomedical devices. While the creation of such new knowledge in material science is important, we must also ensure that this knowledge is understood and transferred effectively. This effort does not only contain educating the general public but also fostering their curiosity and providing them the tools needed to learn that content knowledge. Succeeding in these endeavors is especially important during the first exposure to science courses. The second part of this dissertation focuses on the aspect of learning by looking at educational interventions in two different introductory general chemistry courses. The effectiveness of these interventions was evaluated based on data collected with paper-based, in-class surveys over the course of the semester. A multitude of self-regulated learning (SRL) measures were assessed and range from extrinsic motivation over self-efficacy to help seeking. Statistical analyses were used to identify differences between entire courses and individual sections exposed to the interventions. Additionally, the students' combined grades were also compared. Identifying the effective tools for helping students in chemistry courses is expected to have a major impact on changing the rate of failing students in such courses. This is the step needed for students to decide to become the next researchers contributing to the field with new scientific discoveries themselves.
Open Access
Modeling of laser-created plasmas and soft x-ray lasers
(Colorado State University. Libraries, 2010) Berrill, Mark Allen, author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Menoni, Carmen S., committee member; Lee, Siu Au, committee member
This dissertation describes the development of computer models to simulate laser created plasmas used to generate soft x-ray lasers. These compact short wavelength lasers have substantial average powers and very high peak brightness, that make them of significant interest for many applications. A better understanding of the plasmas is necessary to advance the development of these lasers into more compact, efficient, and higher power sources of coherent soft x-ray light. The plasma phenomena involved are complex, and require a detailed computer model of the coupled magneto-hydrodynamic and atomic physics processes to simulate their behavior. The computer models developed as part of this work consist of hydrodynamic equations, coupled with an atomic model, radiation transport, and a ray propagation equation. The models solve the equations in a 1.5D or 2D approximation, and predict the spatio-temporal plasma variation of the parameter s, including the electron density and temperature, and the ion populations, which are then used to compute the population inversion and the resulting laser gain. A 3D post processor ray trace code was developed to simulate the amplification of stimulated emission along the plasma column length including saturation effects. This allows for the direct calculation of the soft x-ray laser output and its characteristics. Simulation results were compared with experiments conducted at Colorado State University. The general behavior of the plasma and the soft x-ray laser are well described by the model. A specific comparison of the model results with experimental measurements is presented for the case of a collisionally excited 13.2 nm wavelength Ni-like cadmium laser. The model predicts that an optical laser pulse of 1 J energy and 8 ps duration impinging at 23 degrees grazing incidence into a pre-created laser plasma can rapidly heat it to temperatures above 600 eV at a density of 2 x 1020 electrons/cm3. This results in a computed peak small signal gain coefficient of 150 cm-1 in the 4d 1S0 to 4p 1P1 transition of Ni-like Cd at 13.2 nm. The model indicates that the amplified beam reaches the gain-saturated regime after 2.5 mm of propagation in the plasma, in agreement with the experimental observation of saturated behavior for propagation lengths of 2.5-3.0 mm. The computed soft x-ray laser pulse width of 5-9 ps moderately exceeds the experimental value of 5 ps and is the result of a stronger saturation broadening in the simulation. The simulated laser output energy of the order of 1 μJ is also in agreement with experiments. Simulations of injection-seeded Ne-like Ti and Ni-like Ag amplifiers that show very good agreement with the experimental results are presented. A direct comparison of the pulsewidth and the near and far-field beam profiles is made. Finally, the results of a simulation of a plasma created by irradiation of solid targets with a 46.9 nm soft x-ray laser, in which single photon photoionization is the dominant energy absorption mechanism are presented. Low absorption (silicon, Z=14) and high absorption (chromium, Z=24) targets were heated by ~1 ns duration soft x-ray laser pulses. The experimental spectra agree with 1 ½ D simulations in showing that the Si plasmas are significantly colder and less ionized than the Cr plasma, confirming that in contrast to plasmas created by visible wavelength lasers the plasma properties are largely determined by the absorption coefficient of the target material.
Open Access
Nonlinear spin wave instability processes in manganese substituted zinc y-type hexagonal ferrites
(Colorado State University. Libraries, 2010) Cox, Richard Garner, author; Patton, Carl E., advisor; Eykholt, Richard Eric, 1956-, committee member; Kabos, Pavel, committee member; Leisure, Robert Glenn, 1938-, committee member; Menoni, Carmen S., committee member; Robinson, Raymond S., committee member
The large magnetocrystalline anisotropy observed in hexagonal ferrites makes these materials ideally suited for high frequency millimeter-wave applications. However, the large microwave losses observed at low-power levels and the high-power handling capabilities of hexagonal ferrites need to be addressed prior to their wide acceptance in real devices. In order to address the above issues, measurements and analyses of the microwave field amplitude (hcrit) required to parametrically excite nonlinear spin wave amplitude growth were performed on single crystal easy plane disks of Mn substituted Zn Y-type hexagonal ferrites at 9 GHz and room temperatures. Plots of the hcrit dependence on the static magnetic field, termed "butterfly curves," were obtained and analyzed for the resonance saturation (RA), subsidiary absorption (SA), and parallel pumping (PP) configurations. In order to obtain the butterfly curve data and perform the analyses: (1) a state-of-the-art computer-controlled high-power microwave spectrometer was constructed, (2) the classical spin wave instability theory, originally developed by Suhl and Schloemann, was extended, and (3) instability measurements were performed on multiple Zn Y-type hexagonal ferrites samples for several pumping configurations and static field settings. The measurements and analyses performed here constitute the first time RS, SA, and PP spin wave instability butterfly curve analysis have all been performed in planar hexagonal ferrite samples. This work also corresponds to the first time that resonance saturation measurements and analyses were performed for static magnetic fields both at and in the vicinity of the ferromagnetic resonant field in a hexagonal ferrite. The data obtained as part of this work show that the microwave field amplitude required to parametrically excite nonlinear spin wave amplitude growth in hexagonal ferrites is similar to polycrystalline cubic ferrites, which are currently in use in microwave devices. Follow-up measurements, motivated by this work, revealed that hcrit can be varied by manipulating the sample dimensions. The analyses performed here indicate that two-magnon scattering is likely not the dominant source of the large low-power microwave losses observed in these hexagonal ferrites; rather that these losses may be an intrinsic property of the material. The theoretical work performed here identified a sign problem with the anti-Larmor uniform mode complex damping terms in several past publications and provides an improved methodology of treating the uniform mode anti-Larmor complex frequency damping.
Open Access
Organic fluxes as a tool for solid-state synthesis
(Colorado State University. Libraries, 2022) Fallon, M. Jewels, author; Neilson, James R., advisor; Finke, Richard G., committee member; Menoni, Carmen S., committee member; Buchanan, Kristen S., committee member
Solid-state materials allow us to charge our phones, store information on a computer, and harvest energy from the sun, among many other applications. They are the backbone of many modern technologies. However, making solid-state materials remains challenging. Traditional solid-state synthesis involves heating materials up to high temperatures to promote reactivity. These high temperatures make controlling the reactions and directing product formation difficult, as they generally form products that are stable at those high temperatures. There are limited techniques to make solid-materials, especially those that are not stable at high temperatures. In order to advance modern technologies based on solid-state materials, more well-understood, controllable synthetic techniques are necessary. This thesis describes a new technique for making solid-state materials. This technique is based on using molten organic materials, called organic fluxes, to enable selective reactivity between solids at lower temperatures. Owing to the lower reaction temperatures, this synthesis can form materials that are traditionally more difficult to make. The concept of an organic flux is introduced through a case study where triphenylphosphine, the organic flux, is used to make the low-temperature phase of iron selenide. This study demonstrates the efficacy of organic fluxes and provides insight to their mechanism of reactivity. Then, triphenylphosphine fluxes are further explored through reactions involving other metal chalcogenide binaries. By analyzing a variety of systems, the guiding principles behind the reactivity of triphenylphosphine fluxes are determined. Next, the ability of organic fluxes to aid materials discovery is shown through the formation of a new cobalt-selenium-triphenylphosphine complex. Finally, preliminary work exploring other organic fluxes and the future prospects for this synthetic scheme are discussed. This research introduces a new technique to target low-temperature materials. The tunability of organic fluxes enables the design of synthesis for selective reactivity in the solid-state. Adding to the library of synthetic tools available to solid-state chemists is a step towards materials discovery and the advancement of technologies based on solid-state materials.
Open Access
Part I: Development of plasma surface modification and characterization strategies for three-dimensional polymer constructs used in biological applications and Part II: Exploring general chemistry students' metacognitive monitoring on examinations
(Colorado State University. Libraries, 2016) Hawker, Morgan Johanna, author; Fisher, Ellen R., advisor; Rickey, Dawn, committee member; Menoni, Carmen S., committee member; Barisas, George, committee member; Rhodes, Matthew G., committee member
To view the abstract, please see the full text of the document.
Open Access
Periodic metallic nanostructures fabricated by coherent Talbot lithography in a table top system
(Colorado State University. Libraries, 2013) Li, Wei, author; Marconi, Mario C., advisor; Menoni, Carmen S., committee member; Wu, Mingzhong, committee member
This thesis describes a novel technique of extreme ultraviolet (EUV) lithography. A compact nanofabrication system that combines Talbot lithography and a table top extreme ultraviolet laser illumination is presented. The lithographic method based on the Talbot effect provides a robust and simple experimental setup that is capable to print arbitrary periodic structures over millimeter square areas free of defects. Test structures were printed and metalized by ion beam etching system which was rebuilt and calibrated as part of this work. The results demonstrate that a complete coherent extreme ultraviolet lithographic process based on a table top system has the capability to fabricate functional periodic metallic nanostructures. Preliminary results and prospects for future work are also presented at the end of this thesis.
Open Access
Plasma modification of metal oxides and textiles: tailoring surface properties for improved gas sensor and protective clothing applications
(Colorado State University. Libraries, 2021) Hiyoto, Kimberly A. M., author; Fisher, Ellen R., advisor; Menoni, Carmen S., committee member; Rappe, Anthony K., committee member; von Fischer, Joseph C., committee member
This dissertation focuses on utilizing inductively coupled plasma processing to modify various materials for applications in gas sensing and protective clothing. By relating changes in the plasma gas-phase during treatment, resulting material characteristics, and application-based performance, insights into how these materials work can be gained. Ultimately, this knowledge allows for a targeted approach to optimizing the material's surface properties for a specific behavior. The first part of this work concentrates on the plasma modification of semiconducting metal oxides (SMO) to create gas sensors that are more responsive to a target gas at lower operating temperatures. First, SnO2 nanoparticles (NP) supported by a traditional substrate (ZrO2 wafer) were treated with a CO or CO2 plasma as a function of applied plasma power (P). X-ray photoelectron spectroscopy (XPS) analysis of the NP after plasma exposure demonstrates that the CO plasma deposits an amorphous carbon film, whereas the CO2 plasma results in the etching of the SnO2 lattice. Optical emission spectroscopy (OES) studies were used to identify key excited-state species in the plasma gas-phase to explain the depositing and etching nature of these two systems. Gas sensing performance studies demonstrate that the deposition of a film on the SnO2 blocked analyte-sensor interactions, resulting in a negative effect on the response of the sensor. The CO2 plasma treated sensors, however, displayed an increased response to benzene and CO at lower operating temperatures when compared to the untreated (UT) material. The adaptation of the SnO2 sensor and plasma treatments to be compatible with a paper-based sensor (PGS) provided positive indicators for future studies. Indeed, an Ar/O2 plasma was used to treat SnO2 NP PGS at P = 15 – 60 W. Similar to the CO2 plasma, this system has also been shown to etch the SnO2 lattice resulting in improved device performance. The PGS treated at 15 and 60 W showed an increased response to ethanol and CO at operating temperatures ≤50 °C. These studies indicate that the selectivity of the sensor can be tuned with plasma P. Additionally, these sensors showed some response and recovery behavior to ethanol, indicating that these devices are robust enough to be used multiple times. Preliminary work expanding the SMO used to make these PGS is also included to demonstrate the applicability of this device fabrication and plasma modification methods for other materials and SMO morphologies. These gas sensor studies highlight the importance of understanding the relationship between surface properties and device performance. By obtaining a better understanding of the gas detection process, a targeted approach to fabricating improved gas sensors can be established. The final section of this work examines the effect of fabric hydrophobicity on NP attachment and resuspension. These studies employed C3F8 and H2O(v) plasmas to treat four common lab coat materials. XPS and water contact angle goniometry confirm that the C3F8 plasma treatment increases the hydrophobicity of the fabrics and the H2O(v) plasma increases the wettability of most materials. Hydrophobic recovery studies of the H2O(v) treated samples suggest that there are minimal aging effects on the Tyvek® and 100% cotton fabrics, but further work is needed to optimize the plasma parameters for the 80/20 polyester/cotton and 100% polypropylene samples. The attachment and release behavior of Al2O3 NP, carbon black, and carbon nanotubes with the UT and treated materials are also discussed. Ideally, personal protective clothing should either repel (preventing initial NP attachment and fabric contamination) or hold on to (limiting the potential for secondary exposure from contaminated clothes) NP. In general, it is thought that the tightness of the fabric weave is the only factor that influences NP attachment and resuspension. Scanning electron microscopy images of the contaminated and shaken fabrics reveal that the surface chemistry of the material cannot be excluded as the attachment and release of the nanomaterials differed between the C3F8, H2O(v), and UT fabrics. Through these studies, fabric characteristics that influence the interaction with nanomaterials are explored and can be used to inform better safety recommendations when working with these materials.
Open Access
Relativistic plasma nano-photonics for ultra-high energy density physics
(Colorado State University. Libraries, 2014) Purvis, Michael Anthony, author; Rocca, Jorge J., advisor; Yalin, Azer P., committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee member
The trapping of femtosecond laser pulses of relativistic intensity deep within ordered nanowire arrays is shown to volumetrically heat near solid density matter transforming it into ultra-hot highly ionized plasmas. The plasmas were generated by focusing intense ~ 60 femtosecond duration ultra-high-contrast laser pulses onto targets consisting of arrays of densely packed vertically aligned nanowires 35-80 nm diameter. X-ray spectra are presented showing that irradiation of Ni and Au nanowire arrays heats a plasma volume several µm in depth to reach extraordinarily high degrees of ionization (i.e. 26 times ionized Ni , 52 times ionized Au), in the process generating gigabar level pressures. Electron densities nearly 100 times greater than the typical critical density and multi-keV temperatures are achieved using laser pulses of only 0.5 J energy. The large plasma volume and high electron density lead to an increased hydrodynamic-to-radiative lifetime ratio that results in a significant increase in X-ray yield. Measurements from a filtered photodiode array reveal a 100X increase in emission with respect to polished flat targets for photons with energies greater than 9keV. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun.