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A: Atomphysik

Diagonstic Criterion for Beam Crystallization — •Harel Primack and Reinhold Blümel — Fakultät für Physik, Albert-Ludwigs Universität Freiburg

With the help of laser cooling, longitudinally cold heavy-ion

beams were recently obtained in various storage rings.

Theoretical computations indicate that cold beams in a storage

ring may exhibit a transition to a crystalline state.

Because of the near-relativistic velocities of the particles

in a storage ring direct imaging is currently not possible in

order to prove the presence of a crystalline beam.

Therefore, indirect diagnostic methods are called for.

We propose the following criterion for crystallization:

Absence of heating following reduction of the cooling power.

This criterion is motivated by a hysteresis effect first

observed in crystallization experiments with the Paul trap.

The criterion is based on the structure of the classical phase

space of the heavy-ion beam. The criterion is generally

applicable and does not depend on the details of the storage

ring. The validity and applicability of the criterion is

confirmed with the help of detailed numerical simulations.