Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 59, Number 11
Friday–Saturday, October 17–18, 2014; Orem, Utah
Session K7: Nuclear Physics |
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Chair: Robert J. Ridge, Utah Valley University Room: Science Building 60 |
Saturday, October 18, 2014 1:15PM - 1:27PM |
K7.00001: Unanswered Questions: Neutron Emission in the Nuclear Fission Process KaeCee Terry, John E. Ellsworth Nuclear fission has been studied for over 50 years. Yet there remain several outstanding questions regarding neutron emission: Do neutrons originate from the fission fragments or from the scission? Are scission neutrons emitted perpendicular to the fission axis or as Kornilov posits do they trail in the wake of the fission fragments? If there are scission neutrons perpendicular to the axis by what degree are they coupled? Systematic problems with fission sources and detection equipment may be at the root of the issue. At BYU we are working to improve instrumentation for this research. [Preview Abstract] |
Saturday, October 18, 2014 1:27PM - 1:39PM |
K7.00002: Calibration of a cadmium capture-gated neutron spectrometer Craig Higgins, Kent Talbert, Lawrence Rees, J. Bart Czirr, John Ellsworth The cadmium capture-gated neutron spectrometer utilizes a dual-pulse signal from incoming neutrons to differentiate between neutrons and gamma rays. We have built such a detector and performed a time-of-flight experiment at Ohio University to measure incident neutron energy. We determined the detector efficiency as a function of neutron energy for neutrons with energies 0.5 MeV - 9 MeV. The detector has a peak efficiency of 12{\%} for 2 MeV neutrons. The cadmium capture of the neutrons provides a low energy neutron detection boost that keeps the efficiency above 9{\%} for neutrons with energy less than 2 MeV. A properly calibrated cadmium-capture gated neutron detector can be used to measure low energy neutrons from fission sources. [Preview Abstract] |
Saturday, October 18, 2014 1:39PM - 1:51PM |
K7.00003: Closer look at Li$_{6}$Gd(BO$_{3}$)$_{3}$:Ce capture-gated detectors for neutron spectrometry Alec Raymond, John E. Ellsworth Lithium gadolinium borate (LGB) capture-gated neutron detectors have good neutron detection efficiency and gamma ray rejection. We study them for use in neutron spectrometry using our in-house time of flight apparatus. Described here are several recent improvements to the apparatus along with some preliminary results. [Preview Abstract] |
Saturday, October 18, 2014 1:51PM - 2:03PM |
K7.00004: Measurement of Room Return Neutrons Brian Ostler, Lawrence Rees, J. Bart Czirr It is often difficult to determine accurately the number of neutrons incident on a detector because of room return, the scattering of neutrons from nearby material into the detector. We have developed a neutron detection platform mounted on a scissor lift so that room return can be minimized in our counting experiments. I am measuring the neutron counting rate as a function of the height of the platform above a concrete slab located below the lift. I am doing this measurement with a cadmium capture-gated neutron detector with neutrons from a 252-Cf source located at a fixed position on the platform. [Preview Abstract] |
Saturday, October 18, 2014 2:03PM - 2:15PM |
K7.00005: Construction and Testing of Four Adit Photomultiplier Tubes with Scintillating Plastic for Neutron Detection Alexander Corey We have constructed a number of prototype cadmium capture-gated neutron detectors that are simple and inexpensive in design. For many applications, a large volume detector is desirable, so we built and tested a detector with a 10 in. x 10 in. x 6 in. head coupled to four Hamamatsu R1250 photomultiplier tubes. This detector has a maximum efficiency of about 12{\%} for 2.00 MeV neutrons. These tubes are excellent for timing which was important for measuring the detector efficiency as a function of neutron energy, but not optimum for light collection. To improve efficiency, we are building a similar detector using Adit B133D01S photomultiplier tubes. We will describe the construction and operation of these detectors. [Preview Abstract] |
Saturday, October 18, 2014 2:15PM - 2:27PM |
K7.00006: Design and Construction of a Snap Together-Ion Source Tyler Westover, John E. Ellsworth Ion sources are ubiquitous in the sciences and in manufacturing, giving rise to various designs each with advantages and disadvantages. At BYU we are currently constructing a new ``snap-together'' ion source for use with a small low energy particle accelerator. Some of the important features considered in this ion source are: beam spread, energy spread, longevity, ease of repair, ion species and size of the source. I will present the unique advantages and disadvantages along with the progress made on this new ion source. [Preview Abstract] |
Saturday, October 18, 2014 2:27PM - 2:39PM |
K7.00007: Transit Time Uniformity of Two Commercial 5" Photomultiplier Tubes John Peterson, Taylor W. Richards, Nirdosh Chapagain, Michael Ware, John E. Ellsworth, Justin Peatross, J. Bart Czirr, Lawrence B. Rees We investigated the uniformity of electron transit times across the full spatial extent of two 5" photomultiplier tubes, the Hamamatsu R1250 and the Adit B133D01. The Hamamatsu tube is optimized for its timing characteristics, whereas the Adit tube is optimized for light collection efficiency. The photomultiplier tubes were mounted on a scanning stage so that an attenuated laser pulse could be directed to a localized region of the photocathode. A portion of the incident beam was simultaneously measured and recorded by a fast photodiode. Constant fraction discrimination was utilized to calculate electron transit times as the difference between the start times of the photodiode and photomultiplier traces. The Hamamatsu tube provided a uniform timing response that varied by no more than 1.7 ns. The Adit tube was extremely non-uniform; transit times varied by as much as 57 ns when analyzed with both high and low attenuation levels. The symmetry of the variation in transit times of the Adit tube differed significantly when different constant fraction discrimination parameters were applied. [Preview Abstract] |
Saturday, October 18, 2014 2:39PM - 2:51PM |
K7.00008: Precision Measurements of Beta-Decay Rates Eddie Hansen, Justin Peatross, Scott Bergeson, Michael Ware We describe an apparatus for measuring beta decay rates from a variety of nuclear isotopes with a precision of one part in $10^4$ per day of measurement. We simultaneously measure decay rates from Cl-36, Sr-90, Co-60, Cs-137, Na-22, Eu-152, Eu-154, Ba-133, and Mn-54. Each sample is measured sequentially on multiple detectors, and the detectors in turn sample the various decay sources, which rotate into preset positions throughout each day. The experiment is designed to run continuously over many years to check for possible annual variations in the beta decay rates, which were recently suggested to vary with the Earth-Sun distance [J. H. Jenkins, et al., Astropart. Phys. 32, 42-46 (2009)]. Our apparatus is surrounded by pressure-controlled argon gas, and the temperature is held constant to remove possible seasonal influences of the environment. [Preview Abstract] |
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