Simulation of Neutron Wall and Charged Particle Veto Wall for Heavy Ion Collision

Comparison of neutrons and protons emitted in heavy ion collisions is an observable to probe the density dependence of symmetry energy [Cou16]. The dimension of Neutron Wall (NW) at NSCL is about 2x2 m$^{\mathrm{2}}$ which is made of 25 Pyrex tubes filled with liquid Scintillator NE213 that detects recoil protons when neutron interacts with the scintillator. Although it attains excellent discrimination of $\gamma $\textit{-\textmu } and neutron using Pulse Shape Discrimination method, it fails to discriminate charged particles from neutrons. To ensure 100{\%} rejection of charged particles, we plan to build a Charged Particle Veto wall (VW), which will consist of 25 1-cm thick plastic scintillator bars placed directly in front of NW. Simulations using NPTool [Mat16] have been performed to determine the exact design of the VW. To make sure the VW completely covers the NW, overlap of alternate bars is needed. In the poster, I will show the advantage and disadvantage of the positioning plastic bars in a horizontal versus a vertical position as well as position correlation between NW and VW for signal matching. [Cou16] D. D. S. Coupland et al, Physical Review C \textbf{94}, 011601(R) (2016) [Mat16] A. Matta et al, J. Phys. G: Nucl. Part. Phys. 43 (2016) 045113