The Varian Upper Barrel for 300 R2D2 Magnet is an electronic device designed for use with a probe to irradiate rf energy into a sample during a transmit cycle.
The magnet and the probe hold the sample in a homogeneous field for irradiation. The probe assembly for the magnet consists of two parts: a unit that extends through the top of a dewar, called the upper barrel, and a lower unit, the probe.
The sample then reradiates low-level NMR rf energy that is picked up by a coil in the probe. The upper barrel holds the sample, which spins at a controlled rate. The design of the upper barrel allows easy insertion and withdrawal of the sample from the magnet.