Installation of a high-resolution position-sensitive scintillation detector in the small and wide angle neutron scattering instrument (TAIKAN), MLF, J-PARC

Abstract

The small and wide angle neutron scattering instrument (TAIKAN) installed at the Material and Life Science Experimental Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC) can cover a Q-range from 5 × 10−3 to 17 Å−1 simultaneously, where the magnitude of the scattering vector Q is defined by Q = 4πsin(θ/2)/λ (θ and λ represent the scattering angle and the wavelength, respectively). To extend the accessible low Q-limit (Qmin) to a value in the order of 10−4 Å−1, we successfully installed an ultra-small-angle detector with a spatial resolution of approximately 0.41 mm × 0.41 mm in TAIKAN. This detector is a high-resolution position-sensitive detector (HR-PSD), comprising a cross-wired position-sensitive photomultiplier tube and a ZnS/6LiF scintillator. HR-PSDs of the same type have been installed on steady-state small-angle neutron scattering (SANS) instruments at the research reactor (JRR-3), Japan. Comparing with these previously installed the HR-PSDs, we improved most of the HR-PSD components such as the scintillator, preamplifier, and data acquisition systems to increase its maximum count rate. A maximum count rate of 46 kcps was achieved with 10% counting loss, which is 2.3 times for those installed in the steady-state SANS instruments at JRR-3. Using the ultra-small-angle detector with existing 3He detector banks, TAIKAN can simultaneously cover a Q-range from 8 × 10−4 Å−1 to 17 Å−1 (over four orders of magnitude in Q).