Performance of a Large Volume Liquid Scintillation Detector for the Measurement of Fast Neutrons

The KIMS collaboration is an experimental group searching for the Weakly Interacting Massive Particle (WIMP) which is one of the strongest candidates of dark matter. In a WIMP search experiment, the neutron is an important background because the nuclear recoil signal of a neutron is indistinguishable from that of a WIMP. We have constructed a 20-liter liquid scintillation detector to measure the neutron background. We present the performance of the neutron detector, as well as its structure and electronics system. We have achieved a good neutron/gamma separation and a good position measurement. A position dependent energy calibration has also been performed to correct the nonlinear response of the detector for different particle incident positions. PACS numbers: 29, 9