Snakedance Scientific, LLC
Next-Generation Gamma Spectral Analysis with Full-Spectrum Non-Linear Least-Squares Fitting
The original inspiration for what is now known as VRF goes back to February 24, 1987, when Supernova 1987A was first observed on earth. It was the brightest supernova since the Kepler Supernova of 1604, and was a singular opportunity to answer important scientific questions about supernovae. It had been a star in our sister galaxy, the "Large Magellenic Cloud", which is 186,000 light-years distant and only 20 degrees from the celestial South Pole.
High-resolution gamma spectra from the supernova were collected with an N-type HPGe detector during an expedition to Antarctica in January 1988. The detector was flown at an altitude of 40 kilometers, carried by an 11-million cubic foot high-altitude balloon, the first of its kind flown there. Due to the severe radiation environment at that altitude near the South Magnetic Pole, the critical peaks from the supernova could not be analyzed with any of customary methods that search for individual peaks in the data. Because of the harsh radiation environment at high altitude in Antarctica, beginning early 1987 we developed a completely different method for analysis of gamma spectra using non-linear least-squares fitting. This method, which we called "robust fitting", was uniquely successful in the detection of Co-56 in our data from SN 1987A, confirming the theory that the heavy elements were created in supernovae.
Since that time we have continued development of the underlying analysis code with private resources. VRF ("Visual Robust Fitting") is a continually-improving graphical implementation of our underlying non-linear fitting techniques and is the product of more than thirty-six years' work beginning with analysis of the spectra that were obtained from the supernova of 1987. VRF is intended only for analysis of high-resolution spectra and features an extensive library of every gamma ray from 1192 radionuclides. Recent advances include improved methods of fitting continuum, detector efficiency, single and double escape peaks, and both random and cascade sum peaks. We hope you will enjoy the benefits of our work in whatever application of gamma spectral analysis you may endeavor.
Beginnings of VRF... the Supernova of1987
Supernova 1987A as first observed on February 24,1987 (left), and an image taken before the explosion (right).
Credit: David Malin / Australian Astronomical Observatory.
Left: The gondola with the detector assembly, electronics, and solar arrays ready for flight. Right: Recovery of the gondola from the polar plateau of Antarctica, after successfully collecting critical gamma spectral data from Supernova 1987A in a high-altitude balloon-borne flight.