Understanding the results of the experiments performed by DRAGON requires a good knowledge of the beam current incident on the gas target. Currently, it is only possible to measure this current by the insertion of a Faraday cup, a process which interupts the beam and thus, data collection.
The DRAGON beta monitor is located in the mass slit box upstream of the
slits. It detects beta particles from the decay of unstable beam after it
has been stopped by the mass separator. The elastic monitor is
located in the gas target, with solid state Si detectors positioned at
30
and 57 to monitor scattering events. The scaler
rate from both monitors is available during the entire course of a
data acquisition run, unlike a Faraday cup. If a relation could be
found between the beta and/or the elastic monitor rate and some value
directly related to the beam current (such as a Faraday cup reading),
it is hoped that one or both of these monitors could be used as a
continuous monitor of the beam current throughout a run.
Preliminary analysis indicates that a constant relationship between the elastic monitor and the FC4 reading shows large error. A similar conclusion was made for the beta monitor. The ratio between the elastic monitor counts and the beta monitor counts showed the lowest scatter, giving us confidence that both monitors measure the same beam property. It remains only to find a way to relate these values to the beam current.