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Air Force Institute of Technology

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Articles 961 - 990 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Modeling The Thermosphere As A Driven-Dissipative Thermodynamic System, William R. Frey, C. S. Lin, Matthew B. Garvin, Ariel O. Acebal Apr 2014

Modeling The Thermosphere As A Driven-Dissipative Thermodynamic System, William R. Frey, C. S. Lin, Matthew B. Garvin, Ariel O. Acebal

Faculty Publications

Thermospheric density impacts satellite position and lifetime through atmospheric drag. More accurate specification of thermospheric temperature, a key input to current models such as the High Accuracy Satellite Drag Model, can decrease model density errors. This paper improves the model of Burke et al. (2009) to model thermospheric temperatures using the magnetospheric convective electric field as a driver. In better alignment with Air Force satellite tracking operations, we model the arithmetic mean temperature, T 1/2, defined by the Jacchia (1977) model as the mean of the daytime maximum and nighttime minimum exospheric temperatures occurring in opposite hemispheres at a …


Development And Characterization Of A High Speed Mid-Ir Tunable Diode Laser Absorption Spectrometer For Co And Co2 Detection In Detonation Events, Stephen D. Wakefield Mar 2014

Development And Characterization Of A High Speed Mid-Ir Tunable Diode Laser Absorption Spectrometer For Co And Co2 Detection In Detonation Events, Stephen D. Wakefield

Theses and Dissertations

A tunable diode laser absorption spectroscopy system, capable of collecting data at a 10 kHz repetition rate near 4.5 microns. This system was made feasible in recent years due to the development of quantum cascade lasers active in the 4.5 microns region of the spectrum. Reaching into the mid-IR region of the electromagnetic spectrum allowed for an analysis of the fundamental absorption bands for both CO and CO2. The spectral absorption was measured for ethylene, methane, ethane, and propane across a variety of equivalence ratios, at various heights above a Hencken Burner surface. For each fuel, the concentration …


A Recommender System In The Cyber Defense Domain, Katherine B. Lyons Mar 2014

A Recommender System In The Cyber Defense Domain, Katherine B. Lyons

Theses and Dissertations

In the cyber domain, network defenders have traditionally been placed in a reactionary role. Before a defender can act they must wait for an attack to occur and identify the attack. This places the defender at a disadvantage in a cyber attack situation and it is certainly desirable that the defender out maneuver the attacker before the network has been compromised. The goal of this research is to determine the value of employing a recommender system as an attack predictor, and determine the best configuration of a recommender system for the cyber defense domain. The most important contribution of this …


Airborne Wireless Communication Modeling And Analysis With Matlab, Matthew J. Vincie Mar 2014

Airborne Wireless Communication Modeling And Analysis With Matlab, Matthew J. Vincie

Theses and Dissertations

Over the past decade, there has been a dramatic increase in the use of unmanned aerial vehicles (UAV) for military, commercial, and private applications. Critical to maintaining control and a use for these systems is the development of wireless networking systems [1]. Computer simulation has increasingly become a key player in airborne networking developments though the accuracy and credibility of network simulations has become a topic of increasing scrutiny [2-5]. Much of the inaccuracies seen in simulation are due to inaccurate modeling of the physical layer of the communication system. This research develops a physical layer model that combines antenna …


Characterization Of Construction Material Properties Through Gamma Spectroscopy, X-Ray Fluorescence, And Hyper-Spectral Imagery For Background Correction Applications In Nuclear Detection, Jared D. Casebolt Mar 2014

Characterization Of Construction Material Properties Through Gamma Spectroscopy, X-Ray Fluorescence, And Hyper-Spectral Imagery For Background Correction Applications In Nuclear Detection, Jared D. Casebolt

Theses and Dissertations

Material identification through hyper-spectral imagery provides a potentially useful data input for background radiation prediction models for gamma spectrum correction in mobile nuclear detection applications. Traditional background correction methods which rely on prior information are often impractical in mobile detection. Prediction models could combine material information with spatial data to develop a suitable substitute to actual background radiation measurements. This research investigates the relationship hyper-spectral properties and natural radioactivity of construction materials. A selection of construction materials are analyzed using three instrumentation methods: 1) gamma-spectroscopy, 2) X-ray fluorescence (XRF), and 3) hyper-spectral imagery. Gamma-spectroscopy focuses on the presence of potassium …


An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud Mar 2014

An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud

Theses and Dissertations

A lab and eld based hyperspectral chromotomographic imager has been developed at the Air Force Institute of Technology. It is a prototype used to study the requirements for a space-based system. The imager uses a high speed visible band camera behind a direct-vision prism to image both spatial dimensions and the spectral dimension at the same time. Capturing all 3 simultaneously allows for the hyperspectral imaging of transient events. The prism multiplexes the spectral and spatial information, so tomographic reconstruction algorithms must be used to separate hyperspectral channels. Experiments were conducted to compare reconstructed image quality as a function of …


Validation Of The Air Force Weather Agency Ensemble Prediction Systems, William B. Clements Mar 2014

Validation Of The Air Force Weather Agency Ensemble Prediction Systems, William B. Clements

Theses and Dissertations

Air Force Weather Agency's (AFWA) Ensemble Prediction Systems (EPS), Global Ensemble Prediction System (GEPS), 20km Mesoscale Ensemble Prediction System (MEPS20) and 4km Mesoscale Prediction System (MEPS4), were evaluated from April to October 2013 for 10 locations around the world to determine how accurately forecast probabilities for wind and precipitation thresholds and lightning occurrence match observed frequencies using Aerodrome Routine Meteorological Reports (METARs) and Aerodrome Special Meteorological Reports (SPECIs). Reliability diagrams were created for each forecast hour detailing the Brier skill score (BSS) to depict EPS performance compared to climatology for each site and score composition through reliability, resolution and uncertainty. …


Range Finding With A Plenoptic Camera, Robert A. Raynor Mar 2014

Range Finding With A Plenoptic Camera, Robert A. Raynor

Theses and Dissertations

The plenoptic camera enables simultaneous collection of imagery and depth information by sampling the 4D light field. The light field is distinguished from data sets collected by stereoscopic systems because it contains images obtained by an N by N grid of apertures, rather than just the two apertures of the stereoscopic system. By adjusting parameters of the camera construction, it is possible to alter the number of these `subaperture images,' often at the cost of spatial resolution within each. This research examines a variety of methods of estimating depth by determining correspondences between subaperture images. A major finding is that …


Direct Emissivity Measurements Of Painted Metals For Improved Temperature Estimation During Laser Damage Testing, Sean M. Baumann Mar 2014

Direct Emissivity Measurements Of Painted Metals For Improved Temperature Estimation During Laser Damage Testing, Sean M. Baumann

Theses and Dissertations

A database of spectral, temperature dependent emissivities was created for a range of painted aluminum laser damage testing targets with the purpose of improving accuracy in temperature estimates on front and back target surfaces during laser damage tests. Previous temperature estimations were made by fitting an assumed graybody radiance curve to the radiance measured from the back surface via a Telops imaging Fourier transform spectrometer. In this work, spectral emissivity measurements were made using an SOC-100 hemispherical directional reflectometer and Nicolet Fourier transform infrared spectrometer. Of particular interest was a high temperature matte black enamel paint used to coat the …


Verification And Validation Of Monte Carlo N-Particle Code 6 (Mcnp6) With Neutron Protection Factor Measurements Of An Iron Box, Andrew W. Decker Mar 2014

Verification And Validation Of Monte Carlo N-Particle Code 6 (Mcnp6) With Neutron Protection Factor Measurements Of An Iron Box, Andrew W. Decker

Theses and Dissertations

Using a 1984 benchmark experiment, MCNP6 replicated the neutron flux and neutron protection factor (NPF) measurements of an iron box, which simulated a basic military vehicle, resulting in less than 5% difference from the published results. Additionally, the neutron flux spectrum of a 239 PuBe source was characterized using a Bonner Sphere Spectrometer (BSS) and the solution unfolded using the Maximum Entropy Deconvolution (MAXED) program, producing a X2/df of 0.97. Utilizing a steel box provided by the DTRA, measurements of neutron flux from a D-D neutron accelerator were recorded via BSS inside and outside of the box. Both flux spectra …


Structural Characterization Of Atomically Thin Hexagonal Boron Nitride Via Raman Spectroscopy, James M. Bondy Mar 2014

Structural Characterization Of Atomically Thin Hexagonal Boron Nitride Via Raman Spectroscopy, James M. Bondy

Theses and Dissertations

A non-destruction evaluation of atomically thin hexagonal boron nitride (h-BN) films is critical to the U.S. Air Force and Department of Defense initiatives pursuing graphene-based electronic field effect transistors (FETs) capable of operating at terahertz frequencies. H-BN thin films an increase to the characteristic E2g 1367cm-1 h-BN peak intensity has been correlated to an increase in film thickness. Raman spectroscopy on a h-BN film with thicknesses of 7, 14, and 21 atoms (2.5nm, 5nm, 7.5nm respectively) revealed a linear relationship between peak intensity and thickness. This relationship can mathematically be described as y=0.0265x+0.8084, and fits the data with a R2 …


Model Uncertainty And Test Of A Segmented Mirror Telescope, Luke C. Dras Mar 2014

Model Uncertainty And Test Of A Segmented Mirror Telescope, Luke C. Dras

Theses and Dissertations

The future of large aperture telescopes relies heavily on the development of segmented array designs. Today's monolithic mirror technology has reached a barrier, particularly for space-based telescopes. These large diameter, dense mirrors allow stable high-resolution imaging but are incompatible with optimized space launch. Segmented mirror telescopes are designed to balance lightweight with compact stowage. The structure necessary to support the flexible mirror array often combines isogrid geometry and complex actuation hardware. High-fidelity finite element models are commonly used to economically predict how the optics will perform under different environmental conditions. The research detailed herein integrates superelement partitioning and complexity simplifying …


Iron-Doped Zinc Selenide: Spectroscopy And Laser Development, Jonathan W. Evans Mar 2014

Iron-Doped Zinc Selenide: Spectroscopy And Laser Development, Jonathan W. Evans

Theses and Dissertations

We examine the quantum mechanics of optically active ions in crystals. Insight is developed which qualitatively explains the shape of the optical absorption and emission spectra of Fe2+ ions in II-VI materials. In addition to a discussion of the relevant theory, this work explores experimental techniques for absorption spectroscopy, laser-induced fluorescence spectroscopy, and upper-state lifetime measurements in detail. The data collected from these experiments are interpreted in the context of the theories developed herein. The theory and data are used to develop a simple model of the temperature dependence of the upper-state lifetime of Fe2+ ions in ZnSe. …


Utilizing Near-Ir Tunable Laser Absorption Spectroscopy To Study Detonation And Combustion Systems, Christopher J. Mcgahan Mar 2014

Utilizing Near-Ir Tunable Laser Absorption Spectroscopy To Study Detonation And Combustion Systems, Christopher J. Mcgahan

Theses and Dissertations

A Hencken burner, RDE, and a detonation tube were studied using a TDM-TDLAS system to measure water absorption features over two spectral regions (7,435 to 7,442 cm-1 and 7,465 to 7,471 cm-1) near 1.3 micrometers. These absorption features were t with simulated spectra using data from the HITEMP database to obtain temperatures and water concentrations for the three systems. Velocity was calculated for the RDE system using the Doppler shift of the spectral lines. To perform the calculations necessary to obtain these results (temperature, concentration, and velocity) a GUI was developed with supporting code. A Hencken burner flame was studied …


Electrical Characterization Of Spherical Copper Oxide Memristive Array Sensors, James P. Orta Mar 2014

Electrical Characterization Of Spherical Copper Oxide Memristive Array Sensors, James P. Orta

Theses and Dissertations

A new System Protection (SP) technology is explored by using electrical and mechanical interference-sensing devices that are implemented with granular memristive material. The granular materials consist of oxide-coated copper spheres with radii of about 700 µm that are placed in contact to produce thin oxide junctions which exhibit memristive behavior. Processes for etching, which compared acetic acid and nitric acid etches, and thermal oxidation at 100°C are performed and compared to produce copper spheres with a copper oxide layer over the sphere surface. Oxidized copper spheres are tested as sensor arrays by loading into a capillary tube in an aligned …


Complexity, Heuristic, And Search Analysis For The Games Of Crossings And Epaminondas, David W. King Jr. Mar 2014

Complexity, Heuristic, And Search Analysis For The Games Of Crossings And Epaminondas, David W. King Jr.

Theses and Dissertations

Games provide fertile research domains for algorithmic research. Often, game research helps solve real-world problems through the testing and refinement of search algorithms in game domains. Other times, game research finds limits for certain algorithms. For example, the game of Go proved intractable for the Min-Max with Alpha-Beta pruning algorithm leading to the popularity of Monte-Carlo based search algorithms. Although effective in Go, and game domains once ruled by Alpha-Beta such as Lines of Action, Monte-Carlo methods appear to have limits too as they fall short in tactical domains such as Hex and Chess. In a continuation of this type …


Applicability Of Latent Dirichlet Allocation To Multi-Disk Search, George E. Noel, Gilbert L. Peterson Mar 2014

Applicability Of Latent Dirichlet Allocation To Multi-Disk Search, George E. Noel, Gilbert L. Peterson

Faculty Publications

Digital forensics practitioners face a continual increase in the volume of data they must analyze, which exacerbates the problem of finding relevant information in a noisy domain. Current technologies make use of keyword based search to isolate relevant documents and minimize false positives with respect to investigative goals. Unfortunately, selecting appropriate keywords is a complex and challenging task. Latent Dirichlet Allocation (LDA) offers a possible way to relax keyword selection by returning topically similar documents. This research compares regular expression search techniques and LDA using the Real Data Corpus (RDC). The RDC, a set of over 2400 disks from real …


Triplet Ground State Of The Neutral Oxygen-Vacancy Donor In Rutile Tio2, A. T. Brant, Eric M. Golden [*], Nancy C. Giles, Shan Yang, M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton Mar 2014

Triplet Ground State Of The Neutral Oxygen-Vacancy Donor In Rutile Tio2, A. T. Brant, Eric M. Golden [*], Nancy C. Giles, Shan Yang, M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) is used to investigate the triplet (S = 1) ground state of the neutral oxygen vacancy in bulk rutile TiO2 crystals. This shallow donor consists of an oxygen vacancy with two nearest-neighbor, exchange-coupled 3+ ions located along the [001] direction and equidistant from the vacancy. The spins of the two trapped electrons, one at each 3+ ion, align parallel to give the S = 1 state. These neutral oxygen vacancies are formed near 25 K in as-grown oxidized TiO2 crystals by illuminating with sub-band-gap 442 nm laser light. The angular dependence of the EPR …


Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden [*], S. M. Evans, Larry E. Halliburton, Nancy C. Giles Mar 2014

Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden [*], S. M. Evans, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR) is used to characterize the 67Zn hyperfine interactions associated with neutral nitrogen acceptors in zinc oxide. Data are obtained from an n-type bulk crystal grown by the seeded chemical vapor transport method. Singly ionized nitrogen acceptors (N) initially present in the crystal are converted to their paramagnetic neutral charge state (N0) during exposure at low temperature to 442 or 633 nm laser light. The EPR signals from these N0 acceptors are best observed near 5 K. Nitrogen substitutes for oxygen ions and has four nearest-neighbor cations. The zinc ion …


Band Gap Transition Studies Of U:Tho2 Using Cathodoluminescence, Joshua D. Reding Mar 2014

Band Gap Transition Studies Of U:Tho2 Using Cathodoluminescence, Joshua D. Reding

Theses and Dissertations

The Department of Defense has expressed interest in thorium dioxide (ThO2) and uranium dioxide (UO2) as possible candidates for use as special nuclear material in designing neutron detectors. Both materials have large neutron interaction cross sections. Uranium dioxide is particularly attractive due to its semiconducting properties and a relatively small band gap of 2 eV. Both materials fluoresce under ionizing radiation making them candidates for scintillating detectors. Three Ux:Th1-xO2 (x= 0.00, 0.01, 0.22) hydrothermally grown single crystals were examined using cathodoluminescence to interrogate the changing electronic properties of ThO2 as …


Using Software-Based Decision Procedures To Control Instruction-Level Execution, William B. Kimball Dec 2013

Using Software-Based Decision Procedures To Control Instruction-Level Execution, William B. Kimball

AFIT Patents

An apparatus, method and program product are provided for securing a computer system. A digital signature of an application is checked, which is loaded into a memory of the computer system configured to contain memory pages. In response to finding a valid digital signature, memory pages containing instructions of the application are set as executable and memory pages other than those containing instructions of the application are set as non-executable. Instructions in executable memory pages are executed. Instructions in non-executable memory pages are prevented from being executed. A page fault is generated in response to an attempt to execute an …


Timing And Spectroscopy Requirements For A Plastic Scintillating Fiber Bundle Time-Of-Flight Neutron Spectrometer, Paul A. Clement Dec 2013

Timing And Spectroscopy Requirements For A Plastic Scintillating Fiber Bundle Time-Of-Flight Neutron Spectrometer, Paul A. Clement

Theses and Dissertations

The design parameters of a Time-of-Flight (TOF) neutron spectrometer composed of BCF-12 plastic scintillating fibers were investigated. A GEANT4 transport model was developed for analyzing the interaction of 2.5 MeV neutrons with a 14 x 14 BCF-12 fiber bundle. The bundle simulation demonstrated that 0.359% of all neutrons incident on the bundle will double scatter. The timing and data collection e efficiencies of a Tektronix DPO7104 series digital oscilloscope were examined to determine the signal processing requirements for future fiber bundle measurements. The minimum detectable neutron energy was computed by taking into account the bundle scintillation e efficiency, light collection …


Situational Awareness/Triage Tool For Use In A Chemical, Biological, Radiological Nuclear Explosive (Cbrne) Environment, John N. Scarlett, Heather L. Gallup, David A. Smith Dec 2013

Situational Awareness/Triage Tool For Use In A Chemical, Biological, Radiological Nuclear Explosive (Cbrne) Environment, John N. Scarlett, Heather L. Gallup, David A. Smith

AFIT Patents

A method of managing patient care and emergency response following a Chemical, Biological, Radiological, or Nuclear Explosive (CBRNE) attack and maintaining compliance with the Health Insurance Portability and Accountability Act (HIPAA). The method including identifying each patient with a unique patient identifier, the identifier based upon the geospatial location of the patient, the geospatial location including at least the latitude and longitude of the patient when first treated, the unique patient identifier being part of patient data. Providing a collection point of patient data to form a patient data database where in the patient location data may be used to …


Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton Sep 2013

Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton

Faculty Publications

Results from electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) experiments are used to establish the model for the ground state of the singly ionized oxygen vacancy in the interior of bulk rutile TiO2 crystals. Hyperfine from 47Ti and 49Ti nuclei show that the unpaired electron in this S = 1/2 defect is localized on one titanium ion adjacent to the oxygen vacancy (i.e., the spin is not shared by two titanium ions). These defects are formed at low temperature (∼35 K) in as-grown oxidized crystals when sub-band-gap 442 nm laser light converts doubly ionized nonparamagnetic …


Construction, Analysis, And Data-Driven Augmentation Of Supersaturated Designs, Alex J. Gutman Sep 2013

Construction, Analysis, And Data-Driven Augmentation Of Supersaturated Designs, Alex J. Gutman

Theses and Dissertations

Screening designs are used in the early stages of industrial and computer experiments to find the most important input factors affecting a system's output. They provide an economical way to remove unimportant factors from further, potentially costly, experimentation. However, when an experiment has a large number of control factors and limited number of available runs, it is infeasible to run a traditional screening design. In these situations, experimenters can use supersaturated designs. A supersaturated design is a fractional factorial design that can screen a set of k factors in n runs, where k is greater than n -1. Unfortunately, they …


Directional Thermal Emission And Absorption From Surface Microstructures In Metalized Plastics, Michael D. Seal Sep 2013

Directional Thermal Emission And Absorption From Surface Microstructures In Metalized Plastics, Michael D. Seal

Theses and Dissertations

Thermal emission, exhibiting antenna-like directivity, has been generated by a wide variety of both simple and complex micro-structures. The basic demonstrations of directional emission, and specific device performance evaluations, have been conducted at elevated temperatures, typically several hundred degrees Celsius. The most common applications for these high-temperature designs are thermal photo-voltaic and spectroscopic sources. A wide range of lower temperature applications, such as spacecraft thermal management and mid- to far-infrared optical train stray light management, are precluded by the cost and complexity of the fabrication processes employed. In this work, a novel fabrication and physical surface optimization of a seminal …


Why A 15 Minute Biological Detection System?, Doug Lewis Jul 2013

Why A 15 Minute Biological Detection System?, Doug Lewis

Faculty Publications

The biological defense community needs to take a hard look at the requirements and assumptions we use to develop our biological sensors. Today the point sensors currently deployed or in development can offer at best “near real time” detection. This translates into approximately 10-20 minutes from the time an agent passes over the device until an alarm is issued. Why are we working to develop detection hardware which in reality contributes little to no advantage to an operational environment? Should the DOD resist fielding (in the near term) “near real time” detection systems, and instead field slower (but much more …


Applied Hypergame Theory For Network Defense, Alan S. Gibson Jun 2013

Applied Hypergame Theory For Network Defense, Alan S. Gibson

Theses and Dissertations

Cyber operations are the most important aspect of military conflicts in the 21st century, but unfortunately they are also among the least understood. The continual battle for network dominance between attackers and defenders is considered to be a complex game. Hypergame theory is an extension of game theory that addresses the kind of games where misperception exists, as is often the case in military engagements. Hypergame theory, like game theory, uses a game model to determine strategy selection, but goes beyond game theory by examining subgames that exist within the full game. The inclusion of misperception and misinformation in the …


The Dynamic Multi-Objective Multi-Vehicle Covering Tour Problem, Joshua S. Ziegler Jun 2013

The Dynamic Multi-Objective Multi-Vehicle Covering Tour Problem, Joshua S. Ziegler

Theses and Dissertations

This work introduces a new routing problem called the Dynamic Multi-Objective Multi-vehicle Covering Tour Problem (DMOMCTP). The DMOMCTPs is a combinatorial optimization problem that represents the problem of routing multiple vehicles to survey an area in which unpredictable target nodes may appear during execution. The formulation includes multiple objectives that include minimizing the cost of the combined tour cost, minimizing the longest tour cost, minimizing the distance to nodes to be covered and maximizing the distance to hazardous nodes. This study adapts several existing algorithms to the problem with several operator and solution encoding variations. The efficacy of this set …


Chip-Scale Magnetic Source Of Cold Atoms, Eric A. Imhof Jun 2013

Chip-Scale Magnetic Source Of Cold Atoms, Eric A. Imhof

Theses and Dissertations

Numerous disruptive technologies are being hampered by the insufficient modern methods of cooling electrically neutral atoms and molecules. Microchip-based magnetic deceleration provides a cooling mechanism to slow most neutral atoms and molecules within the cost and size requirements of a real-world device. Simulations of a novel deceleration technique show 90% removal of kinetic energy from an atomic beam. An experiment is built which creates a time-dependent, decelerating magnetic field to slow an atomic beam. An atomic beam is magnetically guided 800 microns above the surface of a microchip at pressures of 10-9 Torr. A 60 independent wire microchip is …