Experimental setup used for the angular distribution measurements. On the left is the collimator constructed by stacking 60.69 cm square slabs of polyethylene and clamping them together with threaded steel rods. The angle was adjusted using a hydraulic jack. On the right is the CAEN N472 power supply and a CAEN DT5720 digitizer connected to the laptop via USB. Not shown is the isolation transformer that was used to provide low-noise power