The third instrument to be installed at LENS, the Moderator Imaging Station (MIS), saw its first neutrons in June of 2012. This very simple instrument views the moderator at an angle of 7 degrees from its normal through a horizontal boron-nitride slit positioned roughly 2.3 m from the moderator face. This instrument was designed for use in studies of the so-called convoluted moderator, in which there is a significant angular variation in the emitted intensity, and the slit allows simultaneous collection data over a roughly 3 deg. angular range. A 2mm diameter pinhole can also be used to image the intensity from various parts of a test moderator. To date, moderator experiments on MIS have been performed with a detector brought in from the SNS for each experiment.
Moderator Imaging Station (MIS)
MIS has also been used to test a variety of detectors, ranging from 2-D scintillation detectors to 3He tubes and Silicon detectors used in fundamental physics studies, since the beam provides a broad range of neutron energies and relatively low background levels.
The slit assembly, which is located just in front of the neutron shutter for the MIS instrument, and is its key optical component. This assembly has a boron-nitride-defined slit 2mm tall by 80 mm wide at its center and includes additional steel shielding to reduce the fast neutron flux at the detector.