Position and time resolution measurements with a microchannel plate image intensifier: A comparison of monolithic and pixelated CeBr3 scintillators

To perform Four Dimensional Age Momentum Correlation measurements in the near future, where one obtains the positron lifetime in coincidence with the three dimensional momentum of the electron annihilating with the positron, we have investigated the time and position resolution of two CeBr3 scintillators (monolithic and an array of pixels) using a Photek IPD340/Q/BI/RS microchannel plate image intensifier. The microchannel plate image intensifier has an active diameter of 40mm and a stack of two microchannel plates in chevron configuration. The monolithic CeBr3 scintillator was cylindrically shaped with a diameter of 40mm and a height of 5mm. The pixelated scintillator array covered the whole active area of the microchannel plate image intensifier and the shape of each pixel was 2.5·2.5·8mm3 with a pixel pitch of 3.3mm. For the monolithic setup the measured mean single time resolution was 330ps (FWHM) at a gamma energy of 511keV. No significant dependence on the position was detected. The position resolution at the center of the monolithic scintillator was about 2.5mm (FWHM) at a gamma energy of 662keV. The single time resolution of the pixelated crystal setup reached 320ps (FWHM) in the region of the center of the active area of the microchannel plate image intensifier. The position resolution was limited by the cross-section of the pixels. The gamma energy for the pixel setup measurements was 511keV.