Physics: Posters
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- ItemA Temperature Control Stage for the Deposition of Thin Metal Films(Houghton University, 2024-04-20) Fall, Owen; Yelle, Luke; Hoffman, BrandonA thermal substrate stage was developed for physical vapor deposition of thin metal films. The stage can maintain a uniform, constant temperature across a 4 cm diameter substrate throughout the deposition process, even while it is being radiatively heated at ~5 W for 10 min by the evaporate metal. The substrate is adhered to an 11 cm diameter, 6.4 cm long aluminum heat sink. Previous experiments concluded that Ag paste produced the best thermal contact between the substrate and heat sink. To balance the most surface area possible for thermal contact and removability of the paste, grooves were made in the heat sink. The control stage features ceramic standoffs, holding the aluminum heat sink to the inside of the deposition chamber, and a heater wire pasted to the heat sink to initialize and stabilize the desired temperature.XLII Annual Rochester Symposium for Physics Students, University of Rochester, April 20, 2024
- ItemA TNSA Technique to Measure Light-Ion Cross Sections Using the MTW Laser(Houghton University, 2023-11-03) Lei, Chunsun; Harley, Noah; Hotchkiss, Andrew; Martin, Andrew; Yuly, Mark; Padalino, Stephen J.; Forrest, Chad J.; Sangster, Thomas C.; Regan, Sean P.An experiment was performed using the Multi-Terawatt Laser (MTW) 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. Laser pulses (∼22 J, 7 ps) struck a 0.25 mm2 deuterated polyethylene (CD2) target, ejecting TNSA deuterons that hit a thin natural Li target film on a 25 μm thick stainless-steel substrate, causing the 7Li(d,p)8Li reaction. The phoswich scintillator, light guide, and photomultiplier tube of the Short-Lived Isotope Counting System (SLICS) were placed immediately behind the Li target, and a CAEN Digitizer was used to count the 840 ms half-life beta decay of 8Li, beginning 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. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics, and by SUNY Geneseo and Houghton University.65th Annual Meeting of the APS Division of Plasma Physics, Denver, CO, October 30 – November 3, 2023.
- ItemCoated Li Film Targets for TNSA Light-Ion Reaction Experiments with the MTW Laser(Houghton University, 2023-11-03) Lei, Chunsun; Harley, Noah; Hotchkiss, Andrew; Martin, Andrew; Yuly, Mark; Padalino, Stephen J.; Forrest, Chad J.; Sangster, Thomas C.; Regan, Sean P.A system for creating Sn or Ag coated Li targets was developed for a Multi-Terra Watt (MTW) laser Target Normal Sheath Acceleration (TNSA) experiment to study the 7Li(d, p)8Li reaction. The Li targets were designed to have a ~50 nm thick coating to prevent Li from interacting with air and water vapor and be ~2 μm thick to reduce energy loss. The films were produced in a ~10−5 Torr evacuated deposition chamber in which about 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℃, evaporating the Li onto a 25 μm thick stainless-steel substrate. A current of up to 60 amps 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 thicknesses were measured using a micrometer, magnetic adhesion, a home-made mechanical profilometer, and Rutherford backscattering. To allow Li metal to be weighed and inserted into the boat, an Air-filled glove box was constructed around the deposition chamber. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics, and by SUNY Geneseo and Houghton University.65th Annual Meeting of the APS Division of Plasma Physics, Denver, CO, October 30 – November 3, 2023.
- ItemA Temperature Control Stage for Deposition of Thin Metal Films(Houghton University, 2023-04-15) Fall, Owen; Yelle, Luke; Hoffman, BrandonBecause the properties of the films are significantly affected by a deposition temperature change of only several degrees Celsius, it is vital that the substrate temperature be uniform across the entire substrate and constant throughout the deposition process, even while it is being radiatively heated by the evaporant metal. A temperature control substrate stage is being developed at Houghton University for thin metal films produced on 10 cm Si substrates via physical vapor deposition, with a base pressure of 10-6 Torr. To test possible substrate-stage adhesion materials, a test chamber was set up containing a substrate fixed to a 10 cm diameter aluminum heat sink. Resistive wire was epoxied to the substrate surface to simulate the ~6.5 W of radiative heating that would occur during deposition. Using double-sided copper tape, the minimum temperature change was 18°C in 10 minutes. Adding clamps decreased this to 13°C in 10 minutes. Using Ag paste as an adhesive resulted in a temperature change of only 3°C in 10 minutes.XLI Annual Rochester Symposium for Physics Students, University of Rochester (Rochester, NY), April 15, 2023.
- ItemSimulating Decay Energy Spectra Using Geant4(Houghton University, 2023-04-15) Ockri, Timothy R.; Koehler, Katrina E.; Fitzgerald, Ryan P.Decay Energy Spectroscopy (DES) uses high energy resolution (~1 keV FWHM at 5 MeV [1]) microcalorimeters to measure the total energy of each decay from an embedded radioactive source. A histogram of these energies enables the determination of radionuclide composition, useful for both nuclear safeguards and metrology. In some fraction of decays, some of the decay energy is not thermalized when a particle such as a gamma ray, X-ray, or electron escapes the detector. The probability of this happening depends on the location of the parent nucleus in the absorber, the types and energies of particles released in the decay, and the material,size, and shape of the absorber. A library of possible spectra is created by simulating different shapes and sizes of detector absorbers and compositions, locations, and distributions of sources using the Monte-Carlo particle simulation software Geant4. With Decay Energy Spectroscopy SIMulation for Absolute Total Efficiency (DESSIMATE), a python graphical user interface for visualization, an experimental spectrum can be expressed as a linear combination of these simulated spectra. This will allow the total activity of each radionuclide in a measured sample to be determined. This method can potentially be used in the certification of Standard Reference Materials (SRMs) with precisely known massic activities (defined as unit activity per unit mass).XLI Annual Rochester Symposium for Physics Students, University of Rochester (Rochester, NY), April 15, 2023.