Report on the Construction, Deployment, and Measurement of the Spectra of Atmospheric Photons and Meteorological Parameters in the 0 to 1.8 MeV Regime Using a Wide-Area Array of Detectors.

Abstract:

Measuring atmospheric photons under a wide array of atmospheric conditions may provide a new way to study a wide range of atmospheric conditions, including thunderstorms (TGE's), rain storms and snow storms. We report on the construction and deployment of detector packages that measure spectra, temperature, pressure, and relative humidity. Each standalone detector is mounted at rooftop level and measures and dumps photon spectra in the 0 to ~1.8 MeV regime every 10 minutes, and meterological parameters and overall photon count rate every 30 seconds. Using the precisely known positions and GPS timing of up to 10 detectors spread over western Illinois, eastern Iowa, and southern Wisconsin, we have measured atmospheric photon events in many different conditions, (including at least one tornadic storm). Our preliminary results demonstrate that a complex and changing background is present that must be characterized and understood before clear identification of TGEs and other high-energy photon events is possible. Our preliminary studies show photon events that occur on a variety of time scales, from rapid events that occur in periods of less than 30 seconds to events that last hours and show the spectral signature of the rainout of U-238 chain daughters. We present these events along with our initial attempts to understand and characterize these events and if/how they correlate with local meteorological conditions and lightning strike data from WWLLN. Finally we present what important experimental techniques we learned, our plans for upgrades and expansion of the detector array, and plans for future modeling activities to understand these data. We present how to access our expanding dataset online. This research is supported by a grant from the NSF: AGS-1232594