The Liquids Reflectometer at the SNS*

We have designed and constructed a horizontal-surface reflectometer as one of the first instruments at the Spallation Neutron Source. This instrument is designed to view liquid and solid surfaces in specular, off specular, near-surface small angle scattering, and crystalline diffraction geometries. The guide system supplies 2 {\AA} $<$ \textit{$\lambda$} $<$ 16.5 {\AA} neutrons at vertical incident angles ranging from 0$^{\circ}$ $<$ \textit{$\alpha$}$_{i} <$ 5.5$^{\circ}$ for free liquid surfaces and up to 45$^{\circ}$ for solid surfaces. Three bandwidth choppers, synchronized with the spallation source and operating at 15-60 Hz, provide neutrons in bandwidths ranging from 3.5-14 {\AA} at a fixed \textit{$\alpha$}$_{i}$ onto a sample. The sample stage enables all of the motions necessary for positioning liquid and solid surfaces, while the detector arm allows position-sensitive or pencil $^{3}$He detectors to view the sample at specular or off specular angles up to 90$^{\circ}$ and can scan out of the specular plane by up to 30$^{\circ}$. We will report on our progress commissioning the liquids reflectometer, which essentially involves making the vast parameter space accessible to the instrument accessible to expert and novice users in a coherent and reliable fashion. We have already served our first users and will present examples of data collected, demonstrate our data acquisition and analysis packages, and discuss instrument status.