Thermal Conductivity of Nanowires, Nanotubes and Polymer-Nanotube Composites

Ever rising power densities and smaller transistor dimensions are increasing the challenge of thermal management within integrated-circuit chips and their surrounding packaging. In addition, the need for sustainable energy has placed urgent emphasis on energy conversion. Thermoelectric phenomena, involving the conversion of heat to electrical current, provide a central focus for both needs. Specifically, there is a need to engineer materials or composites with low thermal conductivity and high electrical conductivity for energy conversion and the opposite for heat management. In this presentation, experimental results will be presented of the specific heat and thermal conductivity of cobalt nanowires (CoNW), carbon nanotubes (CNT) and polymer-carbon nanotubes, in various composite arrangements with our high precession Calorimetric technique. Due to the nature of these samples, boundary and defect scattering of phonons in nanomaterials can dominate. This scattering phenomena shows decreasing thermal conductivity in metal nanowires, turns to be good for thermoelectric application. For the CNT, and possibly due to the high volume per atom leading to ballistic phonon propagation, the observed thermal conductivity along the nanotube direction, which leads to manage the heat dissipation problem in integrated circuits (ICs) and microprocessors. The thermal conductivity of a single Single-Wall Carbon Nanotube (SWCNT) was found to be 6600 W/mK, theoretically, twice that of diamond. When such high thermal conductivity materials are dispersed in a low thermal conducting polymer (PMMA), the effective thermal conductivity and thermal stability of the composite can change dramatically. The experimental results show good agreement with theoretical model proposed by Nelsen, Hamilton, Crosse, Geometric, and Xue. The thermal relaxation phenomena such as glass transition temperature (Tg) and dynamics of the molecules in the polymer-nanotubes composites, changes significantly different than the pure polymers during thermal treatment and is one of the focusing point of this presentation. Liquid crystalline materials confined to restrictive nano-channels are of great interest in many potential applications of electro-optics and display technology. This part of the presentation investigates the unexplored phenomenon of the coating and filling of 8CB and 10CB liquid crystals inside ~200nm diameter Multi-Wall Carbon nanopipes. The phase transition characteristics of the confined liquid crystal films were studied using MDSC technique and will be the last part of this presentation

Determination of absorbed dose to water in a clinical carbon ion beam by means of fluorescent nuclear track detectors, ionization chambers, and water calorimetry

Until now, dosimetry of carbon ions with ionization chambers has not reached the same level of accuracy as of high-energy photons. This is mainly caused by the threefold higher uncertainty of the kQ,Q0 -factor of ionization chambers, which is derived by calculations due to a lack of experimental data. The current thesis comprises two major aims with respect to the dosimetry of carbon ion beams: first, the investigation of the potential of fluorescent nuclear track detectors for fluence-based dosimetry and second, the experimental determination of the kQ,Q0 -factor. The direct comparison of fluence- and ionization-based measurements has shown a significant discrepancy of 4.5 %, which re-opened the discussion on the accuracy of calculated kQ,Q0 -factors. Therefore, absorbed dose to water measurements by means of water calorimetry have been performed allowing for the direct calibration of ionization chambers and thus for the experimental determination of kQ,Q0. For the first time it could be shown that the experimental determination of kQ,Q0 for carbon ion beams is achievable with a standard measurement uncertainty of 0.8 %. This corresponds to a threefold reduction of the uncertainty compared to calculated values and therefore enables to significantly decrease the overall uncertainty related to ionization-based dosimetry of clinical carbon ion beams

A Proposal for a Three Detector Short-Baseline Neutrino Oscillation Program in the Fermilab Booster Neutrino Beam

A Short-Baseline Neutrino (SBN) physics program of three LAr-TPC detectors located along the Booster Neutrino Beam (BNB) at Fermilab is presented. This new SBN Program will deliver a rich and compelling physics opportunity, including the ability to resolve a class of experimental anomalies in neutrino physics and to perform the most sensitive search to date for sterile neutrinos at the eV mass-scale through both appearance and disappearance oscillation channels. Using data sets of 6.6e20 protons on target (P.O.T.) in the LAr1-ND and ICARUS T600 detectors plus 13.2e20 P.O.T. in the MicroBooNE detector, we estimate that a search for muon neutrino to electron neutrino appearance can be performed with ~5 sigma sensitivity for the LSND allowed (99% C.L.) parameter region. In this proposal for the SBN Program, we describe the physics analysis, the conceptual design of the LAr1-ND detector, the design and refurbishment of the T600 detector, the necessary infrastructure required to execute the program, and a possible reconfiguration of the BNB target and horn system to improve its performance for oscillation searches.Comment: 209 pages, 129 figure

The rapid atmospheric monitoring system of the Pierre Auger Observatory

The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10^17 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or "rapid") monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction

The rapid atmospheric monitoring system of the Pierre Auger Observatory

The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10(17) eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or 'rapid') monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction