A gas-jet system for the study of short-lived, light fission products

Abstract

For the study of short-lived fission products, a gas jet system has been set up in a beam port of the Ford Nuclear Reactor at the University of Michigan. The system consists of a target chamber joined to three polyethylene tubes which serve as gas inlet, fission product outlet and an outlet for pressure monitoring. The target chamber is housed in a 7.6 cm (ID) aluminum tube supported inside a radial beam port. This tube can be withdrawn by ∼1 m, allowing the target chamber to be positioned either close to or ∼1 m from the core. The aluminum tube is surrounded by water, which provides shielding and protects the target when not in use (at ∼1 m position). The target is ∼1 mg of235U, chemically plated on an aluminum planchett. The uranium is covered with 2.7 mg·cm−2 of aluminum. The aluminum covering stops most of the heavy fission fragments; the light fission fragments pass through the foil and are thermalized in a gaseous mixture of nitrogen and ethylene. The transport time of fission products from the target chamber to the detector position was measured to be 970 msec. Preliminary experiments indicate that the transport time can be reduced further. The gas jet system is being utilized for the development of fast, gas-phase chemistry for the separation of bromine from fission products.