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Biological Imaging using Neutron Radiography
Collaborators: Nicholas Borges, Justine Dupere, Shaun Marshall, Alex Hamm, Mikaylin Jones, Samantha Crepeau, Matt Jalbert, David Medich
Thermal neutrons are a biologically compatible alternative radiation to image mammalian organs for diagnosis of malignant tissue. Due to the large neutron absorption cross-section of Hydrogen, imaging biological media can often result in scattered neutrons, which creates radiographic noise in the imaging media. To address this, a neutron-opaque collimator is used in conjunction with an anti-scatter grid to enhance the output of neutron imaging.
A prior simulation study using MCNP5 demonstrated an iteratively greater signal-to-noise ratio with increasing collimator length, though required increasing neutron flux to maintain image quality. This study provides a pilot calibration of a neutron radiography collimator using in-house neutron camera; a black box which internally captures reflected optical light from a scintillator incident with neutrons.
Radioactive Particulate Resuspension Kinetics
Collaborators: Shaun Marshall, Paula Silvestre, Charles Potter*, David Medich
*Sandia National Laboratories
Resuspension chamber used for sampling airborne particulates which have resuspended from a settled state.
The health risks associated with inhalation of a concentration of radiological or other toxic particulates can be quantified with internal dosimetry. The changing air concentration following a release event depends upon a number of mechanisms, some of which factor into an observed resuspension rate for particulates. This motivated the semi-empirical kinetic model for predicting atmospheric concentrations, but recent observations have failed to match with these predictions.
The goal of this research is to isolate the resuspending particulate system in order to quantify the indoor background resuspension kinetic rate constant. A few grams of particulates are gently deposited atop concrete slabs inside acrylic chambers, and the air above is sampled in hourly or daily intervals. Air filter samples are then irradiated with thermal neutrons and analyzed using gamma spectroscopy to quantify sampled particulate mass and the resulting resuspension factor. Preliminary results of resuspension factors are found to be orders of magnitude below prediction by the current resuspension model. Additionally, the collection of airborne particulates in the sampling volume is found to be sensitive to the sampling height. The study indicates additional capacity to calculate other isolated kinetic rate constants based on specific mechanisms or thermodynamic variables.
Modulated Brachytherapy Treatment Procedure
Collaborators: Justine Dupere, Nicholas Borges, David Medich
(Project information pending)
Automated Fluoroscopic Skin Dose Computation
Collaborators: Norbert Hugger, Andrew Daudelin, Christopher Martel, David Medich
(Project information pending)
Programmatic Neutron Generator Flux Calibration
Collaborators: Shaun Marshall, Adam Ramram, David Medich
Screen capture of LabView interface to Adelphi Technology DD110M neutron generator, with characteristic HV current disruptions.
Neutron activation analysis is a superior technique for quantifying trace nuclides when combined with gamma spectroscopy. The mass of an irradiated sample can be determined through a kinetic model of combined production and radioactive decay. The production depends on the incident neutron flux (quantity per incident surface area) provided by the neutron source. In the case of the generator sources this neutron flux varies by the second of operation. Therefore, the average flux is calibrated using a control placed in the same beamline as the sample, such as a gold foil of known mass.
The Adelphi Technology DD110M Neutron Generator provides feedback of the voltage and current of the high voltage power supply in the target chamber, which indicates relative beam quality in one-second intervals. During standard operation of the generator, different events can be observed in which the electrical circuit “arcs” or “rails”, in either case temporarily halting the beam. To increase the accuracy of expected activity from irradiation and strengthen the predictive power of trace quantity analysis, a MATLAB code is being developed to interpret DD110M operation log files to automatically correct the activation calculation for these “pure decay” events. Secondarily, the neutron flux as a function of the current will be modeled to enable prediction of activation without the need for the control foil.
Monte Carlo Simulation of Cosmic Tau Neutrino Interactions in Ice
Collaborators: Mikaylin Jones, Shaun Marshall, David Medich
A 1.98 GeV proton produces Cerenkov photons in a cone (Jones, 2017). A faint outline of the spherical detector can be seen in the center of the blue region which behaves as ice.
(Project information pending)
Monte Carlo Simulation of TG-43 Analysis
Collaborators: Kenneth Fong, David Medich
(Project information pending)