Matching Items (11)

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Development of Software to Control and Analyze a Tabletop Nuclear Physics System

Description

Different tools have been developed by physicists to detect particle interactions, including one tool called a cloud chamber. A cloud chamber is a device that uses a supersaturated alcohol vapor

Different tools have been developed by physicists to detect particle interactions, including one tool called a cloud chamber. A cloud chamber is a device that uses a supersaturated alcohol vapor to outline the paths of subatomic particles. It requires an adequate source of radiation, either background radiation or a radioactive element, that is placed inside the chamber and allowed to decay. The particles emitted from the decaying element form tracks, as a result of the condensation of the supersaturated alcohol. This condensation ionizes the particles as they are being emitted, which creates the visible track. In order to produce curved tracks, which are necessary for data analysis, a suitable magnetic field must also be applied to the moving particles. As these particles come into contact with the magnetic field, their tracks curve, allowing for measurements of the radius of curvature for each track to be deduced. The radius of curvature can then be used to determine the identity of the atomic nucleus that the emitted particle came from. Computer programming can be applied to this process to make it faster and more efficient. This thesis project involved the composition of a software that could control a cloud chamber apparatus set up to view the beta decay of Pb-210 and analyze the tracks produced by emitted electrons to determine their radius of curvature. By the completion of this project, a software was developed that could accurately detect tracks from test images and control several parts of a cloud chamber.

Contributors

Created

Date Created
  • 2020-05

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Analysis of the Polarization Observables H & P for gamma p -> pi^+ n

Description

A search is underway to find baryon resonances that have been predicted, but yet remain unobserved. Nucleon resonances, due to their broad energy widths, overlap and must be disentangled in

A search is underway to find baryon resonances that have been predicted, but yet remain unobserved. Nucleon resonances, due to their broad energy widths, overlap and must be disentangled in order to be identified. Meson photoproduction observables related to the orientation of the spin of the incoming photon and the spin of the target proton are useful tools to deconvolve the nucleon resonance spectrum. These observables are particularly sensitive to interference between phases of the complex amplitudes. A set of these observables has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab with linearly-polarized photons having energies from 725 to 1575 MeV with polar angle values of cos(theta) between -0.8 and 0.9 and transversely-polarized protons in the Jefferson Lab FRozen Spin Target (FROST). By fitting neutron yields from gamma p -> pi^+ n over azimuthal scattering angle, the observables \H and P have been extracted. These observables manifest as azimuthal modulations in the yields for the double-polarization experiment. Preliminary results for these observables will be presented and compared with predictions provided by the SAID Partial-Wave Analysis Facility.

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Agent

Created

Date Created
  • 2018-05

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Betavoltaic Powered Implantable Pacemakers

Description

Pacemakers in the early 1970s were powered by betavoltaic devices which provided long lasting battery life. The betavoltaic devices also emitted gamma radiation due to inadvertent radioisotope contamination, which could

Pacemakers in the early 1970s were powered by betavoltaic devices which provided long lasting battery life. The betavoltaic devices also emitted gamma radiation due to inadvertent radioisotope contamination, which could not be completely shielded. The betavoltaic devices were quickly replaced by lithium batteries after their invention, and betavoltaics were abandoned. Modern technological advancements made it possible to isolate beta emitting radioisotopes properly and achieve better energy conversion efficiencies which revived the topic of betavoltaics. This research project has studied state-of-the-art pacemakers and modern radioactive power sources in order to determine if modern pacemakers can be safely nuclear powered and if that is a reasonable combination.

Contributors

Agent

Created

Date Created
  • 2014-12

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Radiation transport analysis in chalcogenide-based devices and a neutron howitzer using MCNP

Description

As photons, electrons, and neutrons traverse a medium, they impart their energy in ways that are analytically difficult to describe. Monte Carlo methods provide valuable insight into understanding this behavior,

As photons, electrons, and neutrons traverse a medium, they impart their energy in ways that are analytically difficult to describe. Monte Carlo methods provide valuable insight into understanding this behavior, especially when the radiation source or environment is too complex to simplify. This research investigates simulating various radiation sources using the Monte Carlo N-Particle (MCNP) transport code, characterizing their impact on various materials, and comparing the simulation results to general theory and measurements.

A total of five sources were of interest: two photon sources of different incident particle energies (3.83 eV and 1.25 MeV), two electron sources also of different energies (30 keV and 100 keV), and a californium-252 (Cf-252) spontaneous fission neutron source. Lateral and vertical programmable metallization cells (PMCs) were developed by other researchers for exposure to these photon and electron sources, so simplified PMC models were implemented in MCNP to estimate the doses and fluences. Dose rates measured around the neutron source and the predicted maximum activity of activation foils exposed to the neutrons were determined using MCNP and compared to experimental results obtained from gamma-ray spectroscopy.

The analytical fluence calculations for the photon and electron cases agreed with MCNP results, and differences are due to MCNP considering particle movements that hand calculations do not. Doses for the photon cases agreed between the analytical and simulated results, while the electron cases differed by a factor of up to 4.8. Physical dose rate measurements taken from the neutron source agreed with MCNP within the 10% tolerance of the measurement device. The activity results had a percent error of up to 50%, which suggests a need to further evaluate the spectroscopy setup.

Contributors

Agent

Created

Date Created
  • 2014

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Improved trial wave functions for quantum Monte Carlo calculations of nuclear systems and their applications

Description

Quantum Monte Carlo is one of the most accurate ab initio methods used to study nuclear physics. The accuracy and efficiency depend heavily on the trial wave function, especially in

Quantum Monte Carlo is one of the most accurate ab initio methods used to study nuclear physics. The accuracy and efficiency depend heavily on the trial wave function, especially in Auxiliary Field Diffusion Monte Carlo (AFDMC), where a simplified wave function is often used to allow calculations of larger systems. The simple wave functions used with AFDMC contain short range correlations that come from an expansion of the full correlations truncated to linear order. I have extended that expansion to quadratic order in the pair correlations. I have investigated this expansion by keeping the full set of quadratic correlations as well an expansion that keeps only independent pair quadratic correlations. To test these new wave functions I have calculated ground state energies of 4He, 16O, 40Ca and symmetric nuclear matter at saturation density ρ = 0.16 fm−3 with 28 particles in a periodic box. The ground state energies calculated with both wave functions decrease with respect to the simpler wave function with linear correlations only for all systems except 4He for both variational and AFDMC calculations. It was not expected that the ground state energy of 4He would decrease due to the simplicity of the alpha particle wave function. These correlations have also been applied to study alpha particle formation in neutron rich matter, with applications to neutron star crusts and neutron rich nuclei. I have been able to show that this method can be used to study small clusters as well as the effect of external nucleons on these clusters.

Contributors

Agent

Created

Date Created
  • 2019

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TFT-based active pixel sensors for large area thermal neutron detection

Description

Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection.

Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection. A large area flexible array, utilizing semiconductors for both charged particle detection and pixel readout, ensures a large detection surface area in a light weight rugged form. Such a neutron detector could be suitable for deployment at ports of entry. The specific approach used in this research, uses a neutron converter layer which captures incident thermal neutrons, and then emits ionizing charged particles. These ionizing particles cause electron-hole pair generation within a single pixel's integrated sensing diode. The resulting charge is then amplified via a low-noise amplifier. This document begins by discussing the current state of the art in neutron detection and the associated challenges. Then, for the purpose of resolving some of these issues, recent design and modeling efforts towards developing an improved neutron detection system are described. Also presented is a low-noise active pixel sensor (APS) design capable of being implemented in low temperature indium gallium zinc oxide (InGaZnO) or amorphous silicon (a-Si:H) thin film transistor process compatible with plastic substrates. The low gain and limited scalability of this design are improved upon by implementing a new multi-stage self-resetting APS. For each APS design, successful radiation measurements are also presented using PiN diodes for charged particle detection. Next, detection array readout methodologies are modeled and analyzed, and use of a matched filter readout circuit is described as well. Finally, this document discusses detection diode integration with the designed TFT-based APSs.

Contributors

Agent

Created

Date Created
  • 2014

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Spin observables in [eta] meson photoproduction on the proton

Description

A series of experiments using a polarized beam incident on a polarized frozen spin target

(FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken

during the second running

A series of experiments using a polarized beam incident on a polarized frozen spin target

(FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken

during the second running period with the FROST target using the CEBAF Large Acceptance

Spectrometer (CLAS) detector at Jefferson Lab, which used transversely-polarized

protons in a butanol target and a circularly-polarized incident tagged photon beam with

energies between 0.62 and 2.93 GeV. Data are presented for the F and T polarization observables

for h meson photoproduction on the proton from W = 1.55 GeV to 1.80 GeV.

The data presented here will improve the world database and refine theoretical approaches

of nucleon structure.

Contributors

Agent

Created

Date Created
  • 2016

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Quantum Monte Carlo calculations of light nuclei with non-local potentials

Description

Monte Carlo methods often used in nuclear physics, such as auxiliary field diffusion Monte Carlo and Green's function Monte Carlo, have typically relied on phenomenological local real-space potentials containing as

Monte Carlo methods often used in nuclear physics, such as auxiliary field diffusion Monte Carlo and Green's function Monte Carlo, have typically relied on phenomenological local real-space potentials containing as few derivatives as possible, such as the Argonne-Urbana family of interactions, to make sampling simple and efficient. Basis set methods such as no-core shell model or coupled-cluster techniques typically use softer non-local potentials because of their more rapid convergence with basis set size. These non-local potentials are typically defined in momentum space and are often based on effective field theory. Comparisons of the results of the two types of methods are complicated by the use of different potentials. This thesis discusses progress made in using such non-local potentials in quantum Monte Carlo calculations of light nuclei. In particular, it shows methods for evaluating the real-space, imaginary-time propagators needed to perform quantum Monte Carlo calculations using non-local potentials and universality properties of these propagators, how to formulate a good trial wave function for non-local potentials, and how to perform a "one-step" Green's function Monte Carlo calculation for non-local potentials.

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Agent

Created

Date Created
  • 2013

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Parity violation in the hadronic weak interaction

Description

This thesis deals with the first measurements done with a cold neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The experimental technique consisted of capturing polarized

This thesis deals with the first measurements done with a cold neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The experimental technique consisted of capturing polarized cold neutrons by nuclei to measure parity-violation in the angular distribution of the gamma rays following neutron capture. The measurements presented here for the nuclei Chlorine ( 35Cl) and Aluminum ( 27Al ) are part of a program with the ultimate goal of measuring the asymmetry in the angular distribution of gamma rays emitted in the capture of neutrons on protons, with a precision better than 10-8, in order to extract the weak hadronic coupling constant due to pion exchange interaction with isospin change equal with one ( hπ 1). Based on theoretical calculations asymmetry in the angular distribution of the gamma rays from neutron capture on protons has an estimated size of 5·10-8. This implies that the Al parity violation asymmetry and its uncertainty have to be known with a precision smaller than 4·10-8. The proton target is liquid Hydrogen (H2) contained in an Aluminum vessel. Results are presented for parity violation and parity-conserving asymmetries in Chlorine and Aluminum. The systematic and statistical uncertainties in the calculation of the parity-violating and parity-conserving asymmetries are discussed.

Contributors

Agent

Created

Date Created
  • 2012

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Relativistic matter under extreme conditions

Description

In this thesis, we present the study of several physical properties of relativistic mat- ters under extreme conditions. We start by deriving the rate of the nonleptonic weak processes and

In this thesis, we present the study of several physical properties of relativistic mat- ters under extreme conditions. We start by deriving the rate of the nonleptonic weak processes and the bulk viscosity in several spin-one color superconducting phases of quark matter. We also calculate the bulk viscosity in the nonlinear and anharmonic regime in the normal phase of strange quark matter. We point out several qualitative effects due to the anharmonicity, although quantitatively they appear to be relatively small. In the corresponding study, we take into account the interplay between the non- leptonic and semileptonic weak processes. The results can be important in order to relate accessible observables of compact stars to their internal composition. We also use quantum field theoretical methods to study the transport properties in monolayer graphene in a strong magnetic field. The corresponding quasi-relativistic system re- veals an anomalous quantum Hall effect, whose features are directly connected with the spontaneous flavor symmetry breaking. We study the microscopic origin of Fara- day rotation and magneto-optical transmission in graphene and show that their main features are in agreement with the experimental data.

Contributors

Agent

Created

Date Created
  • 2013