Measurements on electrons conﬁned in a Penning trap show that extreme quadrupole ﬁelds destroy particle conﬁnement. Much of the particle loss comes from the hitherto unrecognized ballistic transport of particles directly into the wall. The measurements scale to the parameter regime used by ATHENA and ATRAP to create antihydrogen, and suggest that quadrupoles cannot be used to trap antihydrogen.
J. Fajans, W. Bertsche, K. Burke, S.F. Chapman and D.P van der Werf