MEMS for Accelerators and Plasmas

Scott Kovaleski
Department of Electrical and Computer Engineering, University of Missouri—Columbia

Accelerators and plasma sources are generally thought of as large, power hungry systems. Linear accelerators are from a few meters to kilometers long, fusion plasmas require mega-amperes of current, and plasma etching requires kilowatts of radio-frequency power, for example. Microelectromechanical systems (MEMS) can be used to develop charged particle accelerators and plasma sources that are simple, compact, and low power. In most cases, the devices we are developing at the University of Missouri are based on lithium niobate piezoelectric transformers. These simple devices take a low voltage radio-frequency input signal to excite an orthogonal vibration mode via the inverse piezoelectric effect. This vibration can then produce a high voltage via the piezoelectric effect. These compact MEMS devices have been used to produce plasma ion sources for high specific impulse micro-spacecraft propulsion. We have also developed simple electrostatic accelerators that have yielded bremsstrahlung x-ray emission to energies >100 keV. These same high voltage accelerators are being developed to produce neutrons for active interrogation, radioactive source replacement, and other nuclear safeguards applications. This talk will focus on the theory of operation and design of piezoelectric transformers with lithium niobate, and will present some applications of and results from these sources.

Level: Advanced

Magnetic Patterns in Superconductors and Ferromagnets

Ruslan Prozorov
The Ames Laboratory and Department of Physics & Astronomy, Iowa State University

Conventional thermodynamics fails when dealing with finite samples that develop patterns, such as ferromagnetic domains or the intermediate state in type-I superconductors. The notion of the ground state has to be replaced by a more vague minimum energy state when the latter has to be calculated in the entire space taking into account stray fields and energy of the domain walls. However, macroscopic measurements are always conducted on the finite samples and yield integrals of the quantities of interest, so the interpretation of the results requires knowledge of the pattern structure. It turns out that these patterns can be highly unusual and their prediction requires non-standard approaches. Various nontrivial phenomena, such as topological hysteresis [1], suprafroth [2] and topological time-reversal symmetry breaking may be observed. I will present direct time-resolved magneto-optical imaging of magnetic patterns in ferromagnets and superconductors and show that some well-established theories, such as Landau’s theory of the intermediate state, have to be revisited. On the other hand, magnetic patterns may be used as model systems to study, for example, the physics of froths [2]. I will conclude with a proposition for the theorists to predict the “minimum energy pattern” using the “generators,” such as iterative function systems or the wavelets.

[1] R. Prozorov, “Equilibrium topology of the intermediate state in type-I superconductors of different shapes”, Phys. Rev. Lett. 98, 257001 (2007).

[2] R. Prozorov, A. F. Fidler, J. Hoberg, P. C. Canfield, “Suprafroth in type-I superconductors”, Nature Physics 4, 327 (2008)

Level: Intermediate

Perspective on the Japanese Fukushima Nuclear Power Plant Disaster

William H. Miller
Nuclear Science and Engineering Institute, University of Missouri – Columbia

On March 11, 2011, at 14:46 (JST), a severe earthquake measuring 9.0 on the Richter Scale occurred 112 miles (180 km) off the coast of the Fukushima Daiichi Nuclear Power Station – the largest Japan has ever experienced. It caused all of the operating units (units 1, 2, and 3) to automatically scram on seismic reactor protection system trips. The earthquake caused a loss of all off-site electrical power sources to the site. The emergency diesel generators automatically started and provided AC power to emergency systems. Forty-one minutes after the earthquake, at 15:27, the first of a series of seven tsunamis arrived at the site. The maximum tsunami height impacting the site was estimated to be 46 to 49 feet (14 to 15 meters). This exceeded the design basis tsunami height of 18.7 feet (5.7 meters) and was above the site grade levels of 32.8 feet (10 meters) at units. All AC power was lost to units 1-4 by 15:41 when a tsunami overwhelmed the site and flooded some of the emergency diesel generators and switchgear rooms. This presentation will discuss what happened at Fukushima and its current status, and will review the media response to the radiological consequences.

Level: Introductory

Investigating the Earliest Phases of Massive Star Formation

Esteban D. Araya
Department of Physics, Western Illinois University

Massive stars – stars with more than eight times the mass of the Sun – are responsible for the enrichment of the interstellar medium with heavy elements and the existence of extraordinary physical objects such as neutron stars and black holes. In this talk I will review some of our current work on the study of massive star formation. In particular, the formation of massive stars within molecular filaments and the discovery of periodic maser flares of several molecular species, which possibly trace periodic accretion events onto young massive binaries.

Level: Intermediate

Mutation, Speciation and Phase Transitions on a Neutral Landscape

Sonya Bahar
Department of Physics and Astronomy, University of Missouri—St Louis

I will discuss how clustering can occur in a neutral fitness landscape in a computational evolutionary model. This clustering simulates sympatric speciation: the organisms cluster phenotypically, but are not spatially separated. Moreover, clustering occurs not only in the case of assortative mating, but also in the case of bacteria-like splitting. Clustering is not observed in a control case where organisms can mate randomly. The population size and the number of clusters undergo phase-transition-like behavior as the maximum mutation size is varied. These results bear comparison with more mathematical studies of clustering on neutral landscapes in the context of branching and annihilating random walks, and have implications for the current debate over the value of “neutral” models in ecology and evolution.

Level: Intermediate

Single and Double Ionization of Atoms and Molecules by Short-Pulse Intense Laser Fields and Charged-Particle Impact

Klaus Bartschat
Department of Physics and Astronomy, Drake University

The yield and the angular distribution of ejected electrons in strong-field ionization can be strongly dependent on the intensity, length, and carrier envelope of the incident laser radiation. We investigate these effects by solving the time-dependent Schrödinger equation directly on a numerical space-time grid. Many methods have been suggested to achieve this goal. We discuss how their effectiveness and appropriateness usually depend on the details of the problem at hand. Results will be presented for single ionization of hydrogen, helium, and heavy noble gases, as well as for double ionization of helium and molecular hydrogen. We also illustrate how the use of two pulses with a fixed delay can yield additional information in so-called “pump-probe” setups. Finally, the connection to the treatment of heavy-particle impact in a time-dependent framework will be discussed.

Level: Advanced

Operations Research: Science of Decision-Making

Esra Şişikoğlu
Industrial and Manufacturing Systems Engineering, University of Missouri – Columbia

Operations Research (OR), a subfield of industrial engineering, is the discipline of applying advanced analytical methods to help make better decisions. Since it is the “science of decision-making,” it can be applied to many real-world problems that we encounter in our daily lives.

In my talk, I will introduce and explain well-known OR problems, and talk about my current research projects including Wireless Sensor and Actor Relocation, Battlefield Routing and Network Inspection Scheduling.

Level: Introductory

Getting the Hot Structures: Containerless Studies of High Temperature Liquids

Kenneth F. Kelton
Department of Physics, Washington University, St. Louis

Liquids, and their solid counterparts glasses, are often thought to lack well-defined atomic order. This is not the case, however. Short-range order among nearest neighbor atoms is often strong in liquids, particularly when they are supercooled below their equilibrium melting temperatures. Some liquids show ordering on even greater length scales, reaching beyond nearest neighbors. Combing a new technique of containerless processing, in which liquids are electrostatically levitated in high vacuum, with high-energy synchrotron X-rays, we have demonstrated a tendency for many metallic liquids to develop short-range order that has the symmetry of an icosahedron (like that of a Dungeon and Dragons 20 sided die). This ordering can act as a template for the nucleation of the crystal phase and underlies metallic glass formation in some cases. These and other points related to the structure and properties of high-temperature metallic liquids will be discussed and upcoming experiments on the International Space Station to investigate this further will be mentioned.

Level: Intermediate

The academic year’s first Women In Physics meeting is this Tuesday in MG 3000 at 8:30pm. Everyone is welcome.

Neutron Imaging of Oscillating Heat Pipes

Robert Andrew Winholtz
Mechanical and Aerospace Engineering Department, University of Missouri—Columbia

Oscillating heat pipes are a promising technology for cooling electronics. Neutron imaging provides a unique method of visualizing the two-phase fluid flow within an oscillating heat pipe. Neutron imaging of oscillating heat pipes containing water and acetone as the working fluid reveal differences in fluid motions in the two heat pipes which explain the performance differences at low heat input. The results show that the volume fraction of liquid phase is highly nonuniform once the thermally excited fluid motion starts. The neutron imaging also reveals a notable synchronization between the movement of liquid into the evaporator portion of the heat pipe and temperature oscillations throughout the heat pipe.

Level: Intermediate