Physics: Research Talks
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- ItemThe Effects of Radiation Escape on Accuracy and Precision in Isotopic Composition Determination of Uranium and Plutonium Samples with Decay Energy Spectroscopy(2024-04-20) Ockrin, Timothy; Koehler, KatrinaDecay Energy Spectroscopy (DES) results in high energy resolution (1-5 keV @ 5 MeV) spectra of decay energies where the energy of each decay is measured as a single event as opposed to individual measurements of each decay particle. In order to accomplish this, the measured source is not external to the absorber, but embedded within it. DES can be used for nuclear safeguards, metrology, and medical isotope development, but measurements are affected by incomplete energy capture occurring when decay particles escape the absorber. In order to reduce escape likelihood, absorbers can be capped with a layer of gold. Geant4, a Monte-Carlo simulation software capable of handling energy transport between particles, is used to simulate DES measurements with varying thicknesses of absorber cap. Analysis of these spectra shows that the biggest benefit of capping can be realized by adding 5 μm of gold to all dimensions, reducing the escape of most alpha-decaying uranium and plutonium radionuclides by an order of magnitude.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024
- ItemTarget Normal Sheath Acceleration as a Technique for Measuring Nuclear Cross-Sections(Houghton University, 2024-04-20) Martin, Andrew; Yuly, MarkA Multi-Terawatt Laser (MTW) experiment was performed at the Laboratory for Laser Energetics (LLE) to test the feasibility of using Target Normal Sheath Acceleration (TNSA) to measure 0.1-10 MeV light-ion cross sections, especially those involving tritium. In this initial experiment using deuterium, laser pulses (∼22 J, 7 ps) struck a 0.25 mm2 deuterated polyethylene (CD2) target, ejecting TNSA deuterons that hit a ~2 μm thick natural Li target film on a 25 µm thick stainless-steel substrate, causing the 7Li(d,p)8Li reaction. The Short-Lived Isotope Counting System (SLICS), consisting of the phoswich scintillator, light guide, and photomultiplier, was placed immediately behind the Li target, and a high-speed CAEN Digitizer was used to count the 840 ms half-life beta decay of 8Li, starting a few milliseconds after the laser shot. The phoswich detector consisted of a fast thin and slow thick scintillator sandwiched together to allow incident particles to be identified by their different rates of energy loss. Incident deuteron energy spectra were measured using time-of-flight (TOF) to a small scintillator in front of the Li target and, for comparison, with a Thompson parabola spectrometer.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024
- ItemA Parity Violation Transmission Experiment for Undergraduate Laboratories(Houghton University, 2024-04-20) Kennel, Levi; Yuly, MarkBecause there are currently no published weak interaction parity violation experiments specifically for undergraduate laboratories, a simple parity violation experiment is being developed using circularly polarized gamma rays. A 60Co source will be placed on one side of an electromagnet, so that the circularly polarized gamma rays emitted opposite the beta particles will pass through the electromagnet core. A NaI detector detects the number of gamma rays that pass through the electromagnet, and a silicon detector detects beta particles opposite the gamma rays. The number of coincidence events will be measured when the electromagnet is polarized both parallel and antiparallel to the gamma rays – an asymmetry between the number of coincidence events for each orientation would show that parity is violated.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024
- ItemDeposition System for Thin Lithium Nuclear Targets(Houghton University, 2024-04-20) Lei, Chunsun; Yuly, MarkA system was developed to create Sn or Ag coated Li nuclear targets for ICF simulation and Target Normal Sheath Acceleration (TNSA) experiments. The purpose of these experiments is to develop ways to measure low energy light-ion cross section using high-power, ultra-fast lasers. The Li targets were designed to have a ~50 nm thick coating to over a 2 m thick Li film to prevent the Li from reacting with air and water vapor. The films were produced in a ~10−5 Torr evacuated deposition chamber. Approximate 15 A flowing one way through a diode circuit heated a stainless-steel boat holding a Li pellet to a thermocouple-measured temperature of nearly 400 °C, evaporating the Li onto a 25 μm thick stainless-steel substrate. A current of up to 60 A flowing the opposite direction through another diode heated a molybdenum boat holding a Sn or Ag pellet, evaporating the metal and forming the thin coating over the Li. The film thicknesses were measured using Rutherford backscattering, a magnetic adhesion tester, and a home-made profilometer. To allow Li metal to be weighed and inserted onto the boat without oxidization, an Air-filled glove box was constructed around the deposition chamber.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024
- ItemDesign and Simulation of Strong-focusing Pole Tips for the Houghton University Cyclotron(Houghton University, 2024-04-20) Hotchkiss, Andrew; Yuly, MarkThe Houghton University cyclotron accelerates ions inside of a 17 cm inner diameter evacuated aluminum chamber placed between the poles of a 1.2 T electromagnet. Two hollow “dee” electrodes, one grounded and one oscillating between a positive and negative potential, apply an electric force that with the magnetic field, accelerates the ions. Previously, weak magnetic focusing, which requires the magnetic field to decrease with larger radius, was used to force the ions back toward the central plane between dees. For large numbers of orbits, however, this made the ions get out of phase with the oscillating electric field. Strong focusing can fix this problem by creating a restoring force while keeping the cyclotron frequency the same. Mathematica and Radia, a 3D magnetic field modeling software package, were used to model the magnetic field of a strong-focusing sector pole tip, then calculate resulting ion orbits. In simulations, the original weak focusing pole tips allowed an ion orbit radius of 3.7 cm to be reached. Using newly designed strong focusing pole tips a radius of 4.9 cm corresponding to 165 keV for protons was achieved. The maximum radius theoretically achievable is 7.2 cm resulting in 360 keV of proton energy.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024