The New NG-5

The SPINS cold neutron triple-axis spectrometer was one of the older instruments at NCNR, and was recently decommissioned as part of the guide upgrade project.  It will be replaced with a new cold triple-axis instrument with a state-of-the-art beam delivery system.   Modern guides for cold-neutron triple-axis instruments are optimized for a double focusing monochromator (DFM).  This means that the guide typically provides a virtual source in the horizontal plane while supplying a “parallel” beam in the vertical dimension.  The new NG-5 is such a guide, straight in the horizontal and elliptical in the vertical planes, respectively, as shown in the diagram below. 

Note the dimensions of the x and y axes are very different distorting the guide shape.  The vertical lines delineate each segment of the guide, while the color on edge refers to the guide coating.   Guide installation is complete from confinement through the wall penetration into the guide hall.  The image below shows NCNR technicians loading guide sections into the NG-5 penetration casing ahead of installation.

This guide will deliver neutrons to a 400 cm² DFM array housed in a drum with iron shot shielding, both of which are already available on-site.   With those components, the primary spectrometer should deliver a flux on sample of about 10⁸ n cm^-2-s^-1, roughly an order of magnitude better than that of SPINS.  Options for the secondary spectrometer are being evaluated, and engineering designs for the instrument backend should be ready by late 2025.   Operation of this new triple-axis spectrometer is expected no sooner than 2030.