Spatial resolution of novel liquid scintillating capillary array

Abstract

Scintillating array image plates are allowed high resolution through a thicker detector which increases quantum efficiency without degrading the imaging resolution substantially. Due to limitations imposed by process capability, scintillator fiber array with pixel diameter less than 0.2 mm is hardly manufactured to improve performance. Therefore, a liquid scintillator capillary array with 0.1 mm pixel is developed to improve the detection efficiency and spatial resolution of image plate for low intensity radiation imaging. Its performances are studied and tested by simulation and experiment, and are compared with those of scintillating fiber array. Especially in order to gain high fidelity representation of modulation transfer function of the array image plate, a method of simulating and measuring the slanted knife edge response and an iterative algorithm are introduced. For 14 MeV neutron and 1.25 MeV gamma, the slanted knife edge responses of these array image plates with pixel dimensions in a range from 0.1 mm to 0.5 mm are respectively simulated by MCNPx program and the modulation transfer function (MTF) are obtained. The simulation results show that compared with scintillating fiber array, the liquid scintillator capillaries array has an obvious merit in spatial resolution because of greater stopping power for secondary charged particle in the capillary quartz glass wall with 0.02 mm in thickness. Its ultimate resolution can reach to 1.8 lp/mm for 14 MeV neutron by simulation. At the 4000 Ci ⁶⁰Co facility, a 5-cm-thick tungsten bar, one side of which has a curvature of 0.1 radian to minimize the misalignment effect, is made a knife edge. The MTF of the scintillating fiber array with 0.3 mm and 0.5 mm pixel and newly developed liquid scintillator capillary array is measured through this tungsten knife edge. Experimental measurement results have also verified that the liquid scintillator capillary array performs well in spatial resolution and luminescent uniformity for 1.25 MeV gamma. The ultimate spatial resolution, 0.9 lp/mm is gained, and those of other scintillating fiber arrays are all less than 0.5 lp/mm. Moreover, experimental test validates the simulating method and simulated results, although the measured value is slight less than the simulated value because of the effect of dimension of ⁶⁰Co source.