Plasmonic Dephase Time of Au Nanoparticles

Joya Anthony, Jackson State University, Jackson, MS

Mentor: Jaetae Seo

The ultra-fast dephasing of plasmonic Au nanoparticles occurs on a time scale of only a few femtoseconds, which is not easily accessed with modern spectroscopy technology. This experiment shows theoretical studies for the dephasing time of plasmonic Au nanoparticles. Plasmonic dephase is the lifetime of coherent polarization of plasmon oscillations. The plasmonic dephasing time may be analyzed with absorption spectroscopic parameter of intraband transition of Au nanoparticle. After running the nanoparticles through the UV-Vis Spectrophotometer, it showed that the absorption spectra near UV was attributable to interband transitions. The absorption peaks around ~525 nm, for Au nanoparticles with radius between ~2.08 nm and ~31.70 nm, which is attributable to the localized Surface Plasmon Resonance (SPR) or intraband transitions. The absorption bandwidth and dephasing time were found using the relationship between wavelength and energy. Then, the dephasing time was calculated by the formula for T2. The dephasing time was shown in a graph as a function of radius of Au nanoparticles with different population relaxation time. Plasmonic dephasing time was successfully analyzed with optical absorption spectroscopy. Dephasing time for the Au Nanoparticles with radius from ~2 to ~31 nm was estimated to be ~2 - ~4 fs. Population relaxation time was estimated to be around ~2.5 - ~10 fs.

Development of GEM Detectors for OLYMPUS and Analysis of BLAST Experimental Results

Matthew Anthony, University of Notre Dame, Notre Dame, IN

Mentor: Michael Kohl

OLYMPUS is a precision experiment that investigates the two-photon contribution to elastic lepton scattering. It is based on the existing BLAST detector to precisely determine the trajectories of charged particles. This apparatus does not cover the forward angle regions where elastic scattering will be used to monitor the luminosities. Therefore, precise tracking detectors will be placed in these positions. GEM (Gas Electron Multiplier) detectors incorporate Cu layer-sandwiched Kapton foils with a chemically etched micro-hole pattern for gas amplification. A test chamber for GEM detectors was produced to test performance of GEM foils and the readout.

A ROOT data analysis project was carried out in preparation for a publication of BLAST experimental data. Graphs were produced for the new measurements of the deuteron tensor analyzing powers T20 and T21 and the separated charge (GC) and quadrupole (GQ) form factors as a function of four-momentum transfer in comparison with existing data and various theoretical descriptions.

In-Vivo Proton Therapy Dosimetry Using Scintillating Fiber Technology

Ashley Cetnar, Grove City College, Grove City, PA

Mentor: Paul Gueye

Proton therapy is a cancer treatment modality that uses high-energy proton beams to irradiate cancerous cells while minimizing the radiation to healthy tissue.  Because of its Bragg peak distribution, a proton is more efficient in localizing doses than conventional x-ray therapy. While proton therapy has been proven to be a reliable treatment, it is important to characterize the effects of the radiation. When the protons interact within the body, there are many reactions that induce secondary radiation beams. To date, there is still no accurate device available that is capable of measuring the beam profile and effective dose delivery during the treatment (i.e., in-vivo). The research conducted during the 8-week NSF/REU Undergraduate Institute of PHYsics program at Hampton University focused on the use scintillating fibers technology to measure the secondary emitted radiation exiting a water phantom tank and the delivery system (nozzle) bombarded by proton beams. Scintillating fibers are ideal for detection in a clinical setting because of their linear response to ionizing energy, small size, and water equivalent composition. A realistic Geant4 Monte Carlo simulation was also developed to provide additional information to further optimize our prototype. This paper presents the results obtained from preliminary scintillating fibers.

Electron Ion Collider (EIC) Detector: Tracking Chamber

The goal of this project is to design a particle detector to be used in an Electron Ion Detector (EIC) at Jefferson laboratory. I developed the tracking chamber planned for the EIC detector. The EIC will be used to collide various elementary particles in hopes to obtain a better understanding of the gluon fields in the nuclei as well as complete the image of the sea of quarks and gluons within the nucleon. Each detector within the detector system is used to obtain data from specific particle decays. The tracking chamber is used to calculate the velocity and trajectory of incoming particles. The GEANT4-Monte Carlo model is used to test the potential detector's ability to identify specific planned interactions as decays.

Development of GEM Detectors for OLYMPUS and Analysis of BLAST Experimental Results

Mentor: Michael Kohl

OLYMPUS is a precision experiment that investigates the two-photon contribution to elastic lepton scattering. It is based on the existing BLAST detector to precisely determine the trajectories of charged particles. This apparatus does not cover the forward angle regions where elastic scattering will be used to monitor the luminosities. Therefore, precise tracking detectors will be placed in these positions. GEM (Gas Electron Multiplier) detectors incorporate Cu layer-sandwiched Kapton foils with a chemically etched micro-hole pattern for gas amplification. A test chamber for GEM detectors was produced to test performance of GEM foils and the readout. A ROOT data analysis project was carried out in preparation for a publication of BLAST experimental data. Graphs were produced for the new measurements of the deuteron tensor analyzing powers T20 and T21 and the separated charge (GC) and quadrupole (GQ) form factors as a function of four-momentum transfer in comparison with existing data and various theoretical descriptions.

Fabrication of a Cosmic Ray Test Stand for use Testing Drift Chambers for the Thomas Jefferson National Accelerator Facility - Hall C - 12 GeV Upgrade

Mentor: Eric Christy

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is upgrading its Continuous Electron Beam Accelerator Facility (CEBAF) to run at 12 gigaelectron volts, an upgrade that allows them to add an additional Hall (D), and improve the existing Halls. This includes a new spectrometer for Hall C, the Super High Momentum Spectrometer (SHMS), which is used in conjunction with the existing High Momentum Spectrometer to measure particles scattered at the new full beam momentum. Two drift chambers within the SHMS are used to measure production angle and particle momentum. To test these drift chambers, two cosmic ray test stands have been fabricated. Three scintillation detectors were built and used to plateau each other using an efficiency method. Two of these scintillation detectors were then attached to a stand that allows them to scan the width of the drift chambers. This cosmic ray test stand can now be used to test the drift chambers' channels, as well as other detectors and equipment. The second test stand began being created from a 64 channel photomultiplier tube (PMT), and two of the prototype planes from the MINERvA detector. This test stand will, when completed, be able to more accurately and speedily test the drift chambers, covering more area and providing one dimensional particle tracking.

Cerenkov Detection in the Barrel Region of an Electron Ion Collider Detector

Mentor: Rolf Ent

The preliminary design for Cerenkov detection in a detector of the Electron Ion Collider is proposed. Examination of the kinematics for the exclusive reactions reveals necessary detection for kaons and pions in the barrel region of the detector best separated by Cerenkov detection. By researching the specifications of existing detectors, the size and materials for the Cerenkov detectors were chosen. The designs of a DIRC detector and a RICH detector were created and modeled for future Monte Carlo simulations. Based on the simulations, the detectors can be adjusted for optimum performance, laying the groundwork for future efforts to expand on.

Testing and preparation of GEM detectors for the OLYMPUS experiment at DESY

Mentor: Michael Kohl

The OLYMPUS experiment at DESY (Deutsches Elektronen Synchrotron, "German Electron Synchrotron") seeks to investigate the effect of two-photon exchange on elastic electron-proton and positronproton scattering. Gas-Electron Multiplier (GEM) detectors are a type of gaseous particle detectors that are used in OLYMPUS to accurately measure the luminosities based on forward-angle elastic scattering. They are comprised of insulated pairs of thin sheets of metal called GEM foils, which contain multiple chemically etched holes. This paper details the various tests used to assure the quality of each GEM foil, such as charged-coupled device (CCD) scanning and high voltage testing. This paper also compares the performance of numerous GEM foils produced by the manufacturing company Tech-Etch. Performance is reported in terms of uniformity of hole-size and the amount of leakage current during high voltage testing.

Modeling of Polarized Electron-Proton Elastic Scattering in the Collider Kinematics

Mentor: T. W. Donnelly

The Electron-Ion Collider (EIC) is a proposed new facility designed to collide high-energy electrons with nuclei and polarized protons. The EIC is an essential step towards the next frontier in understanding the fundamental quark-gluon structure of matter. The electron-proton (e-p) program aims at precisely imaging the sea quarks and gluons in the nuclei. The goal of this project is to model the e-p cross section and polarization asymmetry, at the conditions of relevance for the EIC. The concept of cross section is used to express the likelihood of interaction between particles; therefore, it provides important information about the nature of quarks and gluons. The development of the formalism for this reaction makes it necessary to reframe the electron scattering kinematics into the conditions of the EIC. Ultimately, documentation and computer codes regarding the modeling will be made available for future use by the EIC community.

Electromagnetic Calorimeter Design for an Electron Ion Collider at Jefferson Lab

Mentor: Rolf Ent

Plans to build an Electron Ion Collider at the Jefferson Lab are being discussed. The collider would be used to study the Deep Inelastic Scattering that can take place when a beam of protons collides with a beam of electrons. The research goals of the project are to understand the gluon fields in nuclei, and create an image of the sea quarks in the nucleon. The following paper presents the specifications needed by the calorimeter device, to be used in the Electron Ion Collider's particle detector, that will achieve these goals. Research is concluded with a Monte Carlo simulation indicating the ability of the design to identify certain particles, specific to the interactions that will be taking place in an Electron Ion Collider.

Optimizing Brachytherapy Treatments with Polarized Beams

Mentor: Paul Gueye

Electromagnetism is one of the four fundamental interactions of nature, alongside strong interactions, weak interactions, and gravitation. This force governs the interaction between electrically charged particles. Polarization is a property of electromagnetic waves that describes the orientation of their oscillations. The polarization of light beams or particulate radiation can be described by specifying the orientation of the wave's electric field at a point in space over one period of the oscillation. Over fifty percent of cancer patients undergo some form of radiation treatments. This research will study the difference of polarization states between healthy and cancerous cells lines. If such difference is found, than it may open the doorway to use polarized radiation beam to optimize cancer cell killing.

Preliminary Magnetic Field Designs for an EIC Detector

Mentor: Rolf Ent

Deep inelastic scattering experiments at the proposed Electron-Ion Collider (EIC) will help provide important insights into the nucleon's structure. A detector for the collider is currently being designed with the emphasis of this paper being the magnetic field which is used to measure particle momentum. Different magnetic field configurations were considered to achieve necessary momentum resolution. A moderate increase in solenoid radius over what was initially predicted along with a dipole field in the forward region was found to allow for a weaker field and improved resolution.