[by] R.D. Maurer [and] Melvin A. Herlin. / Bibliography: p. 6. / Army Signal Corps Contract No. W-36-039 sc-32037, Project no. 102B. Dept. of the Army Project No. 3-99-10-022.

Knowledge of the provenance of crustal volatiles and the processes by which they are released is extremely important for the dynamics of magmatic systems. Presented here are the results of multiple investigations, which aim to understand magmatic volatile contamination from contrasting but complementary perspectives. The main methodologies used include He and C isotope values and CO2/3He ratios of volcanic gases and fluids; simulation of magma-carbonate interaction using high-pressure high-temperature experimental petrology; X-ray microtomography of vesiculated xenoliths and computer modeling. Findings show that the contribution from upper crustal volatiles can be substantial, and is dependant on the upper crustal lithology on which a volcano lies, as well as the composition of the magma supplied. Carbonate dissolution in particular is strongly controlled by the viscosity of the host magma. The details of the breakdown of vesiculated xenoliths is complex but has wide reaching implications, ranging from the dissemination of crustally derived materials through a magma body to highlighting that crustal volatiles are largely unaccounted for in both individual volcano and global volatile budgets. In synthesizing the conclusions from each of the individual perspectives presented, I propose the contribution of volatiles from crustal sources to play a significant role in many geological systems. This volatile component should be taken into consideration in future research efforts.

The subject of this thesis is experimental studies of electron-transfer processes in ion-atom collisions at velocities significantly higher than typical orbital velocities of electrons in bound states of atoms or molecules. The experimental technique applied combines the high beam intensity of heavy-ion storage rings with a supersonic gas-jet target equipped with a recoil-ion-momentum spectrometer. In singleelectron capture to fast protons from helium atoms, we have for the first time achieved a complete separation of the kinematic and Thomas transfer mechanisms and are able to perform a quantitative comparison with the many theoretical results on a much more detailed level than what was previously possible. For the process of transfer ionization in proton-helium collisions we have determined the velocity dependence of the Thomas transfer ionization cross section to be the expected vp-11 when the projectile velocity, vp, is sufficiently high. Further, we have determined the velocity-dependent probability for shake-off of the second electron from helium provided that the first one is transferred in a kinematic capture process. Finally, we have considered collisions between protons and hydrogen molecules. Here we have found a strong variation in the cross section for transfer and excitation processes when the angle between the direction of the incoming projectile and the internuclear axis of the target molecule is varied. The variation can be explained as a result of quantum mechanical interference related to the two indistinguishable atomic centers of the molecule.

The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used. There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon. For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used. When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is. For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.

The Large Hadron Collider (LHC) is the next large particle accelerator developed at CERN, constructed to enable studies of particles. The acceleration of the particles is carried out using magnets operating at about 1.9 K, a temperature achieved by regulating flow of superfluid helium. For economical reasons, control of the helium flow is based on feedback of virtual flow meter (VFT) estimates instead of real instrumentation. The main purpose of this work is to develop a virtual flow meter with the possibility to estimate the flow by means of two different flow estimation methods; the Samson method that has previously been tested for the LHC, and the Sereg- Schlumberger method that has never before been implemented in this environment. The virtual flow meters are implemented on PLCs using temperature and pressure measurements as input data, and a tool for generating the virtual flow meters and connect them to the appropriate physical instrumentation has also been developed. The flow through a valve depends, among others, on some pressure and temperature dependent physical properties that are to be estimated with high accuracy. In this project, this is done by bilinear interpolation in twodimensional tables containing physical data, an approach that turned out to be more accurate than the previously used method with polynomial interpolation. The flow measurement methods have been compared. Since they both derive from empirical studies rather than physical relations it is quite futile to find theoretical correspondencies, but the simulations of the mass flows can be compared. For low pressures, the results are fairly equal but they differ more for higher pressures. The methods have not been validated against true flow rates since there were no real measurements available before the end of this project. / Le Grand Collisionneur de Hadrons (Large Hadron Collider, LHC) est le prochain grand accélérateur de particules du CERN, construit pour permettre l’étude des particules. L’accélération des particules sera réalisée en utilisant des aimants supraconducteurs qui fonctionneront à 1.9 K et la température sera régulée en contrôlant le débit d’hélium superfluide. Pour des raisons économiques, la régulation du débit d’hélium sera basée sur les réponses des estimations des débitmètres virtuels (Virtual flow meters, VFT) au lieu d’instrumentation réelle. Le but principal de ce projet est de développer un débitmètre virtuel qui estimera le débit avec deux méthodes différentes ; la méthode Samson qui a déjà été mise en oeuvre pour le LHC, et la méthode Sereg-Schlumberger qui n’a pas encore été implémentée dans cet environnement. Les débitmètres virtuels seront implémentés sur des PLCs avec des mesures de température et de pression comme données d’entrée. De plus, un outil pour générer les débitmètres et les relier avec l’instrumentation physique adéquat a été développé. Le débit à travers d’une vanne dépend entre autres des propriétés physiques qui dépendent à leur tour de la température et de la pression. Ces propriétés devront être estimées avec une grande précision. Dans ce projet, cela est fait en appliquant une interpolation bilinéaire dans des tableaux de deux dimensions. Cette méthode s’est montrée plus précise qu’avec une méthode d’interpolation polynomiale. Les deux méthodes de mesures de débit ont été comparées. Elles dérivent toutes les deux des études empiriques et non physiques, alors les similarités théoriques sont donc peu pertinentes, mais les résultats des simulations des débits peuvent être comparés. Pour des pressions basses, les méthodes sont quasiment équivalentes, mais les différences sont plus importantes pour les pressions plus hautes. Étant donné qu’il n’y avait pas de mesures disponibles avant la fin de ce projet, les méthodes n’ont pas été validées avec des débits réels.

This thesis presents an implementation of path integral molecular dynamics (PIMD) for sampling equilibrium and dynamical properties within the molecular modelling toolkit (MMTK) [J. Comp. Chem. 21, 79 (2000)], an open source Python package. Rigorous simulation using this code serves to benchmark this implementation as well as the robust- ness of the path integral Langevin equation as a thermostat [J. Chem. Phys. 133, 124104 (2010)]. PIMD is used to calculate equilibrium properties for clusters of HeN-CO2 at low- temperatures, with comparison to experimental and exact results. We characterize the convergence of structural and energetic properties as a function of path-integral discretiza- tion error. The radial and angular distribution of these clusters is studied as a function of size in the absence of rotation and bosonic exchange. These distributions are subsequently used to calculate vibrational shifts of CO2. This result is compared to high-accuracy path integral Monte Carlo simulations which include rotational and exchange effects. These sim- ulations indicate that the neglect of rotational degrees of freedom leads to an unphysical localization of helium atoms and incorrect vibrational shifts when compared to experiment. Approximate real-time quantum dynamics is presented for doped helium clusters using the ring-polymer molecular dynamics (RPMD) method. The accuracy of RPMD is tested iii for low-temperature simulations and compared to exact results. Preliminary calculation of the dynamics of the helium solvated CO2 dopant with respect to the center of mass of the cluster is presented. The effect of a cartesian integrator versus a normal-mode integrator for quantum dynamics is addressed. The path integral ground-state method is applied in order to calculate T = 0 properties. A convergence study of the ground-state energy of the quantum harmonic oscillator with respect to sampling time and path discretization is shown. As a final application of this implementation, a sugar in a periodic water box is simulated at T = 300K. The calculation of rotamer populations and a dipole autocorrelation indicate negligible change with the inclusion of quantum effects. This work offers a comprehensive foundation from which to base future PIMD centered research.

<p>Measurements of the three-body photodisintegration of <super>3</super>He were performed at the High Intensity &gamma-ray Source (HI&gammaS). Neutrons emitted in this reaction inside a <super>3</super>He gas target were detected with seven 12.7 cm diameter liquid scintillator detectors. Time-of-flight (TOF) and pulse-shape discrimination (PSD) techniques were used to identify neutron events. The absolute differential cross sections for the <super>3</super>He(&gamma, n)pp reaction as a function of outgoing neutron scattering angle and energy were determined from the measurements at the incident &gamma-ray energies of 11.4, 12.8, 13.5, and 14.7 MeV to within a precision better than +/- 6 %.</p><p>The absolute cross sections at each incident energy are compared to the results of Gorbunov [Gor74], phase space calculations, and state-of-the-art three-body calculations. The inclusion of the Coulomb interaction in the three-body problem has been a long-standing challenge in theoretical nuclear physics. The present experimental data were found to be in good agreement with the state-of-the-art theory, which includes a full treatment of the Coulomb interaction between</p><p>the protons in the final state [Del05].</p> / Dissertation

<p>An experiment measuring the analyzing power A_y(&theta;) for neutron&ndash;helium-3 (<italic>n</italic>-<super>3</super>He) elastic scattering over broad angular distributions for a range of incident neutron energies from 1.60 to 5.54 MeV has been conducted at the Triangle Universities Nuclear Laboratory. These measurements represent an effort to resolve the long-standing discrepancy between experiment and theory in low-energy three-nucleon analyzing powers, through the evaluation of analyzing powers in the four-nucleon systems, which are expected to exhibit sensitivities not accessible with fewer nucleons. The present work is described in terms of the experimental setup and data reduction techniques; a comparison of the results with rigorous calculations using both nucleon-nucleon and, as recently has become available, three-nucleon potential models is presented. While a discrepancy between calculation and measurement was observed, at low energies substantially better agreement was achieved than in related measurements of the proton&ndash;helium-3 (<italic>p</italic>-<super>3</super>He) analyzing power, suggesting a sizeable dependence on isospin in the four-nucleon systems.</p> / Dissertation

Qualitative and quantitative analysis of trace substances determined by Mass spectrometry has unique advantages which can¡¦t be replaced. For example, the detection limit of common gas sensors are difficult to lower than 1 ppm, and the sensitivity, selectivity, period of use and stability are not ideal. The detection limit of mass spectrometer is general low to 0.01 ppm. Furthermore, all substances in the sample can be simultaneous analysis by mass spectrometer, but single gas sensor measurements cannot. In this study, dielectric barrier discharge plasma is used in environmental mass spectrometry analysis. This study develops an innovative balanced T-shaped dielectric barrier discharge (DBD) plasma generator for generating atmospheric plasma to replace the linear type plasma generator. Through the change of the geometric configuration and the drive phase develop T-shaped dielectric barrier discharge plasma, the balanced design can fully cancel the high potential and noise. The main objective of this study for the more traditional linear electrodes of the study's original novel T-shaped electrodes of different, including mass spectrometry, spectroscopy, and some basic electrical measurements, and by changing the electrode design, voltage, temperature, gas flow, gas flow rate, diameter and other parameters of the dielectric, and compare their differences and to explore the most suitable parameters. The results showed that T-shaped design of the research and development of innovation through the elimination of the exit pressure put EFI flame can indeed significantly reduce sample oxidation and generate fragments of the situation, and thus improve the mass spectrum of readability and debris interference, thus improving the detection limit , especially for some with a benzene ring and long-chain carbon samples. The experimental results confirm that the development of the Institute of Atmospheric Pressure Plasma free system can be prolonged to produce high concentrations of plasma gas as a free source of the mass spectrometry system, and provides more than 107 cm-3 ion concentration. MS-free analysis of the system can be directly on the gas, liquid and solid samples, the test do not need complicated traditional mass spectrometry analysis of the required sample pre-treatment steps, you can get a clear identification of high mass spectrometry signal. In addition to introducing the basic principles and structure of the atmospheric pressure plasma discharge device, and take advantage of many samples test for the different plasma mass spectrometry free system performance verification.

<p>This thesis is a study of the heat transfer correlations between a wire and liquid helium cooled to either 1.9 or 4.3 K. The wire resembles a part of a superconducting magnet used in the Large Hadron Collider (LHC) particle accelerator currently being built at CERN. The magnets are cooled to 1.9 K and using helium as a coolant is very efficient, especially at extremely low temperatures since it then becomes a superfluid with an apparent infinite thermal conductivity. The cooling of the magnet is very important, since the superconducting wires need to be thermally stable.</p><p>Thermal stability means that a superconductive magnet can remain superconducting, even if a part of the magnet becomes normal conductive due to a temperature increase. This means that if heat is generated in a wire, it must be transferred to the helium by some sort of heat transfer mechanism, or along the wire or to the neighbouring wires by conduction. Since the magnets need to be superconductive for the operation of the particle accelerator, it is crucial to keep the wires cold. Therefore, it is necessary to understand the heat transfer mechanisms from the wires to the liquid helium.</p><p>The scope of this thesis was to describe the heat transfer mechanisms from a heater immersed in liquid and superfluid helium. By performing both experiments and simulations, it was possible to determine properties like heat transfer correlations, critical heat flux limits, and the differences between transient and steady-state heat flow. The measured values were in good agreement with values found in literature with a few exceptions. These differences could be due to measurement errors. A numerical program was written in Matlab and it was able to simulate the experimental temperature and heat flux response with good accuracy for a given heat generation.</p>