$^3$He multi-wire proportional counters for the FNPB at the SNS

We have constructed a set of beam monitors for the Fundamental Neutron Physics Beam Line (FNPB), at the Spallation Neutron Source, Oak Ridge National Laboratory. The beam monitors are $^3$He multi-wire proportional counters. A $^3$He nucleus that captures a neutron will break up by the reaction $n+^3He\rightarrow p+T+765keV$. The 765keV is released as kinetic energy of the proton and triton which will ionize the chamber gas, giving a consistent signal from each capture. The chamber gas is a mix of $N_2$ and $^3He$ at 750 Torr. The $^3He$ fraction used determines the fraction of the beam that is captured. The $^3$He chambers are used to monitor the neutron flux along the neutron beam, and are currently used for the NPDGamma experiment, but will also be used for beam line diagnostics in future experiments. I will report on the monitor design, construction, and beam data obtained during the commissioning of the NPDGamma experiment. I will also report on the design, and simulation of a $^3$He wire chamber to be used in the n$^3$He experiment, which runs after the NPDGamma experiment. It uses the same neutron detection process as described above, but will be black to neutrons (high $^3He$ content) with a small amount of ionization gas, to allow the protons to range out over as long a distance as possible to measure the parity violating longitudinal asymmetry in the number of protons emitted in the capture reaction.