Eye Action

In lieu of an abstract, below is the essay\u27s first paragraph. \u27Give her a little eye action.\u27 \u27What?\u27 \u27The girl over there. She just looked over at you. Give her a little eye action.\u2

Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems

NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device\u27s parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects

Barrier Island Evolution, Delta Plain Development, and Chenier Plain Formation in Louisiana.

Coastal Louisiana has long served as a laboratory for delta and chenier plain research due to the presence of North America\u27s largest river, the Mississippi. The development and preservation of transgressive depositional systems in abandoned delta complexes follows the process of transgressive submergence in which the horizontal component of reworking occurs during shoreface retreat, combined with a vertical component of submergence acting to preserve the sequence. The evolution of transgressive depositional systems in each of the abandoned Holocene Mississippi River delta complexes can be summarized in a three-stage model beginning with stage 1, an erosional headland and flanking barriers; stage 2, a transgressive barrier island arc; and stage 3, an inner shelf shoal. The current Mississippi River delta model depicts a single Holocene delta plain consisting of six delta complexes sequentially deposited over the last 7000 years by the delta switching process. The delta plain is now viewed as consisting of two separate delta plains deposited at different sea level positions. Termed the Modern and Late Holocene, these two delta plains are separated by a regional ravinement surface several hundred kilometers along strike in extent and bounded updip by a relict shoreline of maximum transgression, the Teche shoreline. The Late Holocene delta plain consists of a set of delta complexes deposited during a sea level stillstand some 6 m below the present, 7000-4000 yBP. A relative sea level rise between 4000-3000 yBP to about present sea level led to the transgressive submergence of the Late Holocene delta plain, generating Trinity Shoal, Ship Shoal, and the Teche shoreline. The Modern delta plain began building seaward of the Teche shoreline about 3000 yBP. The St. Bernard and Lafourche delta complexes and associated transgressive shorelines represent the abandoned portions of the Modern delta plain, separated from the underlying Late Holocene delta plain by the regional Teche ravinement surface

The Effects of Fabry-Perot Fringing on the Sensitivity of a Wavelength Modulation Experiment

Parasitic Fabry-Perot etaloning plagues many experiments which use wavelength modulation spectroscopy. This fringing, which is an artifact that almost always appears in such experiments, arises from multiple reflections in the optical elements in the experimental apparatus. The etaloning plays a detrimental role and limits the ultimate sensitivity of wavelength modulation spectroscopy experiments. The research described in this thesis investigates this phenomenon. Experimental results are presented which show that when the Q-factor of the parasitic etalon is smaller that that of the absorption line being measured, significant improvement in the Signal to Fringe Noise Ratio can be obtained through the use of higher harmonic detection. A model is developed and experimental results are compared with theoretical predictions. The extremely good agreement obtained enables us to extract accurate values for the modeling parameters. Line centers, line widths, and optical absorption cross-sections of several lines in the oxygen A-band are measured with high accuracy using the etalon as a reference

The two-body problem of ultra-cold atoms in a harmonic trap

We consider two bosonic atoms interacting with a short-range potential and trapped in a spherically symmetric harmonic oscillator. The problem is exactly solvable and is relevant for the study of ultra-cold atoms. We show that the energy spectrum is universal, irrespective of the shape of the interaction potential, provided its range is much smaller than the oscillator length.Comment: Final version accepted for publication in Am. Journ. Phy

Lateral Power Mosfets Hardened Against Single Event Radiation Effects

The underlying physical mechanisms of destructive single event effects (SEE) from heavy ion radiation have been widely studied in traditional vertical double-diffused power MOSFETs (VDMOS). Recently lateral double-diffused power MOSFETs (LDMOS), which inherently provide lower gate charge than VDMOS, have become an attractive option for MHz-frequency DC-DC converters in terrestrial power electronics applications [1]. There are growing interests in extending the LDMOS concept into radiation-hard space applications. Since the LDMOS has a device structure considerably different from VDMOS, the well studied single event burn-out (SEB) or single event gate rapture (SEGR) response of VDMOS cannot be simply assumed for LDMOS devices without further investigation. A few recent studies have begun to investigate ionizing radiation effects in LDMOS devices, however, these studies were mainly focused on displacement damage and total ionizing dose (TID) effects, with very limited data reported on the heavy ion SEE response of these devices [2]-[5]. Furthermore, the breakdown voltage of the LDMOS devices in these studies was limited to less than 80 volts (mostly in the range of 20-30 volts), considerably below the voltage requirement for some space power applications. In this work, we numerically and experimentally investigate the physical insights of SEE in two different fabricated LDMOS devices designed by the author and intended for use in radiation hard applications. The first device is a 24 V Resurf LDMOS fabricated on P-type epitaxial silicon on a P+ silicon substrate. The second device is a iv much different 150 V SOI Resurf LDMOS fabricated on a 1.0 micron thick N-type silicon-on-insulator substrate with a 1.0 micron thick buried silicon dioxide layer on an N-type silicon handle wafer. Each device contains internal features, layout techniques, and process methods designed to improve single event and total ionizing dose radiation hardness. Technology computer aided design (TCAD) software was used to develop the transistor design and fabrication process of each device and also to simulate the device response to heavy ion radiation. Using these simulations in conjunction with experimentally gathered heavy ion radiation test data, we explain and illustrate the fundamental physical mechanisms by which destructive single event effects occur in these LDMOS devices. We also explore the design tradeoffs for making an LDMOS device resistant to destructive single event effects, both in terms of electrical performance and impact on other radiation hardness metric