An inexpensive triple-axis neutron spectrometer

A simple design is suggested for a triple-axis neutron spectrometer. Although the instrument does not have the flexibility of sophisticated machines, it is capable of the measurements required by most phonon problems. As it has only one working configuration it should be very simple to use. The basic design problem of these instruments is the control of a heavily shielded counter at the extremity of three variable arms. In the suggested instrument the counter is free only to rotate about the vertical. Support and control of the heavy shielding is, therefore, much simplified. The geometry is altered by varying the lengths of two of the arms, which is possible to high accuracy.