Improvement of the mesitylene cold moderator at KUANS

The improvement of the neutron intensity of mesitylene cold moderator in KUANS has been conducted in two ways. One is the change of the mesitylene phase by annealing and the other is the optimization of the configuration. The change of the phase of the mesitylene was conducted by keeping the temperature of mesitylene just below its melting point for several hours. It made the cold neutron intensity about 20% larger than that of normally cooled mesitylene. For the configurational optimization, an arrangement giving highest cold neutron intensity was chosen using a Monte Carlo code. The cold neutron intensity measured with this arrangement revealed that its intensity is 3.4 times higher than that for a polyethylene moderator with room temperature.