Authors: Malcolm Colson (University of New Hampshire)

Earth is constantly being showered with cosmic rays, most of which produce energetic neutrons that can make it to the ground. To protect equipment and crews in space, we use ground-based neutron monitors to monitor cosmic-ray activity.

One of the UNH neutron monitors is in Durham, New Hampshire, at an elevation of 20 m and a geomagnetic cutoff of 2.21 GeV. It first started taking data in 1964 and was moved to a site a mile away from the center of campus in 2006. It consists of three banks each with six BP-28 tubes in an NM64 configuration. The tubes are 190.8 cm long and roughly 15 cm in diameter. They are each surrounded by a lead producer and a polyethylene moderator. Additional polyethylene is used for absorbing local environmentally produced neutrons. The secondary neutrons from the atmosphere interact with the lead producer, which multiplies the neutron number and degrades their energy. These neutrons are moderated and some undergo a nuclear reaction with the 10B gas within the tube, producing 7Li and an 4He, which deposit their energy in the detector. The health of the tubes has been measured and documented and are producing reasonable count rates and spectra.

Despite the fact, that the monitor is operating properly, the monitor faces some problems currently, such as two less-than-healthy tubes and hourly count rate digital spikes. We are running tests on our tubes and software to address these issues. We also have neutron monitors in other locations, such as Mount Washington and Leadville CO, where we must perform similar diagnostics. In particular, the Mount Washington site has a similar geomagnetic cutoff but different atmospheric cutoff. Because both stations use the same type of electronic supporting equipment, comparing their data to each other is made simpler, because no unnecessary conversion is necessary. Because of this, when a GLE occurs, we can deduce its spectra power density by comparing the cutoff dependent rates from the two stations. The data recorded by all the monitors are stored in individual text files, thus enabling a database to make performing analysis over longer periods of time more convenient. A database, as well as the means to automatically retrieve and process data from the monitor, is currently being developed in PostgreSQL and Python. We will address these issues and upgrade our system to data to the NMDB, the worldwide neutron monitor database.