Jack FitzGerald

The Rotating Scatter Mask (RSM) system is an inexpensive retrofit that provides imaging capabilities to scintillating detectors. Unlike traditional collimator systems that primarily absorb photons in order to form an image, this system primarily scatters the photons. Over a single rotation, there is a unique, smooth response curve for each defined source position. Testing was conducted using MCNPX simulations. Image reconstruction was performed using a chi-squared reconstruction technique. A… Show more

The Rotating Scatter Mask (RSM) system is an inexpensive retrofit that provides imaging capabilities to scintillating detectors. Unlike traditional collimator systems that primarily absorb photons in order to form an image, this system primarily scatters the photons. Over a single rotation, there is a unique, smooth response curve for each defined source position. Testing was conducted using MCNPX simulations. Image reconstruction was performed using a chi-squared reconstruction technique. A simulated 100 uCi, Cs-137 source at 10 meters was detected after a single, 50-second rotation when a uniform terrestrial background was present. A Cs-137 extended source was also tested. The RSM field-of-view is 360 degrees azimuthally as well as 54 degrees above and 54 degrees below the horizontal plane. Since the RSM is built from polyethylene, the overall cost and weight of the system is low. The system was designed to search for lost or stolen radioactive material, also known as the orphan source problem. Show less

A novel, fully reconfigurable liquid collimator device for γ-ray and X-ray imaging was built and tested as a coded aperture. The device contained a 10 × 10 grid of 5 × 5 mm2 chambers, each 5 cm long. The chambers were either grilled with an attenuating liquid, absorbing photons, or evacuated of the liquid, allowing the photons to pass. As the pattern of “on” and “off” chambers was manipulated, different, semi-independent views of the γ-ray source were found. A random mask sequence outperformed… Show more

A novel, fully reconfigurable liquid collimator device for γ-ray and X-ray imaging was built and tested as a coded aperture. The device contained a 10 × 10 grid of 5 × 5 mm2 chambers, each 5 cm long. The chambers were either grilled with an attenuating liquid, absorbing photons, or evacuated of the liquid, allowing the photons to pass. As the pattern of “on” and “off” chambers was manipulated, different, semi-independent views of the γ-ray source were found. A random mask sequence outperformed a uniformly redundant array when maximum-likelihood expectation maximization was used. Noise and reconstruction artifacts decreased as the number of masks increased. With ten mask patterns, the signal-to-noise ratio in images of point sources increased by a factor of 2. Images of a segmented, extended source are presented to demonstrate, qualitatively, that image quality increased when more masks were used. Additionally, the system crudely imaged a source using only the photons that Compton scattered within the mask. Show less

The Canary instrument is a miniature electrostatic analyzer designed to detect positively charged ions in the energy range 0-1500 eV. The Canary concept began with the development of a Micro-Electro-Mechanical (MEMS) Flat Plasma Spectrometer (FlaPS), which, integrated with electronics onto FalconSAT-3, reduced the size and mass of an ion plasma spectrometer to about 10x10x10 cm3 and 250 g. The successor to FlaPS was the Wafer Integrated Spectrometer (WISPERS), expanding the same instrument to… Show more

The Canary instrument is a miniature electrostatic analyzer designed to detect positively charged ions in the energy range 0-1500 eV. The Canary concept began with the development of a Micro-Electro-Mechanical (MEMS) Flat Plasma Spectrometer (FlaPS), which, integrated with electronics onto FalconSAT-3, reduced the size and mass of an ion plasma spectrometer to about 10x10x10 cm3 and 250 g. The successor to FlaPS was the Wafer Integrated Spectrometer (WISPERS), expanding the same instrument to seven sensors all with uniquely optimized energy ranges and azimuth/elevation look angles. WISPERS is due to fly on the USAF Academy's FalconSAT-5 satellite scheduled for launch in Spring 2010. FlaPS and WISPERS created a paradigm shift in the use of such instruments in a highly capable but small, low power package. The third generation, Canary (named after the "canary in the coal mine" - an earlier technology used to provide low-cost, effective warning of danger to operators), will be flown on the International Space Station (ISS) and used to investigate the interaction of approaching spacecraft with the background plasma environment around the ISS. Show less