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

摘要

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 x 10(-3) to 17 angstrom(-1) simultaneously, where the magnitude of the scattering vector Q is defined by Q = 4 pi sin(theta/2)/lambda (theta and lambda represent the scattering angle and the wavelength, respectively). To extend the accessible low Q-limit (Q(min)) to a value in the order of 10(-4) angstrom(-1), we successfully installed an ultra-small-angle detector with a spatial resolution of approximately 0.41 mm x 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/(LiF)-Li-6 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 x 10(-4) angstrom(-1) to 17 angstrom(-1) (over four orders of magnitude in Q).