A recent and significant addition to the Nuclear Structure
Laboratory facilities is the Radioactive Nuclear Beam
facility, designed for the study of nuclear reactions
using radioactive beams. The facility is the result of
a collaborative effort between the University of Notre
Dame and the University of Michigan, and it consists of
a pair of in-line superconducting solenoid magnets, with
each solenoid comprised of thousands of meters of Niobium-Titanium
wire wound into a cylindrical coil. Each coil is housed
in a thermally insulating vessel, known as a cryostat,
and when in operation, each superconducting coil is surrounded
by liquid helium (boiling temperature -268o
C). Each of the superconducting solenoids produces a maximum
magnetic field of about 6 Tesla (by comparison, the earth's
magnetic field is about 0.00005 Tesla).
 In a standard configuraton, the use of
radioactive nuclear beams for experimentation is very difficult,
since by definition the ions in the beam are unstable and
therefore decay into more stable forms. The lifetime of
a radioactive nuclear beam varies depending upon the ion
involved, but is often so short that traditional methods
of beam production cannot be used, as the ions in the beam
decay in flight on their way to the target. It is often
simply not possible to produce a radioactive ion beam with
a traditional ion source, accelerate it to the energy needed
for experimentation, and deliver it to the target in the
extremely short lifetime of the radioactive ion.
Our RNB facility circumvents these problems
by producing the radioactive ion beam at the target station.
A stable ion beam, such as 7Li, is produced using
the SNICS II Sputter Ion Source, and accelerated to the appropriate energy by
the FN Tandem Van de Graaff accelerator. This primary beam is focussed and steered
into the RNB beamline, where it impinges upon a target located
just upstream of the first superconducting solenoid
magnet. The nuclear reactions that take place when the energetic
primary beam strikes the target produce a wide variety of
particles exiting the target region, many of which are quite
exotic and very short lived. By proper choice of the target
material, primary beam, and the primary beam energy, the
production of a particular radioactive ion, such as 6He, can be maximized.
The superconducting solenoid magnets are used to selectively
collect and focus the appropriate radioactive ions emerging
from the primary target area, producing a secondary radioactive
nuclear beam which can then be used for experimentation
by transporting this beam to a secondary target within the
RNB facility. To date, several experiments have been performed,
producing and studying radioactive nuclear beams such as
3H, 6He, 7Be, 8Li, 8B, 11C, 12N, and 18Ne with a typical beam intensity of 5 x 10 5
per microA of primary beam.
Also, please visit the site maintained by the University
of Michigan about this collaborative dual solenoid project.
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