Speaker
Description
Beams from ECR ion sources have 3-fold transverse
rotational symmetry induced by the ECR sextupole.
The symmetry imposes equality constraints among
transverse beam moments, which can be derived
using a theoretical framework we developed. Since
the constraints are solely a consequence of the
rotational symmetry of external fields, they hold for
arbitrary charge state distribution and space charge
intensity. These constraints provide a new tool to
analyze phase space properties of ECR beams and
their impact on low-energy transport. We prove that,
regardless of their triangulation, beams with 3-fold
rotational symmetry have the same rms emittance
and Twiss parameters along any transverse direction.
These counter-intuitive results are applied to the
FRIB Front End to demonstrate how symmetry
arguments challenge long-standing assumptions and
bring clarity to the beam dynamics.