Background Measurement of Gamma Rays, Muons, and Neutrons at LENA

The Laboratory for Experimental Nuclear Astrophysics (LENA) will be replacing its existing 1-MeV JN accelerator with a 2-MeV singletron whose size would be better accomodated by switching the location of the target from the east end of the lab to the west end. However, the amount of background radiation may be different at opposite ends of the lab due to the construction of the building. To determine the feasibility of relocating the target, the flux of gamma rays, muons, and neutrons were measured using a HPGe detector, a BC-408 scintillation detector, a sodium-iodide scintillation detector, and a model IV inventory sample counter (INVS) neutron detector. Background values at the current location were compared with those at the west end of the lab. Additionally, a GEANT4 simulation of the INVS counter was used to derive a cosmic ray-induced neutron flux from experimental data. Measurements indicate that the muon and neutron backgrounds at the current target location are lower than at the west end, but that the background from gamma rays is higher. Therefore, the target in LENA should remain in its current location, where the muon and neutron backgrounds are lower.