Relaxation in a strongly coupled particle beam

Transverse Laser Cooling of a Fast Stored Ion Beam through Dispersive Coupling

“…At high phase-space densities relaxation due to intrabeam Coulomb collisions leads to efficient indirect cooling of the transverse motion [5]. As the beam approaches an ordered state, however, heat exchange due to Coulomb interaction becomes insufficient to reach crystallization [6,7]. Different schemes have been proposed to provide a transverse damping force independent of the mutual particle interaction [8][9][10], but none of them was realized so far.…”

Crystalline ion beams in the RF quadrupole storage ring PALLAS

“…The accented tubes are used to localize ions in the laser cooling section, to locally shift the velocity distribution for monitoring purposes, or to bunch an ion beam. To load the ring, a weak beam of 24 Mg-atoms is ionized inside the trapping volume by a focused electron beam and simultaneously laser-cooled to zero velocity.…”

“…Sketched in fig. 2, it can be considered as a ringshaped quadrupole ion guide [15, 29, 24 Mg+ ion [31]. The corresponding single-particle secular frequency amounts to O(sec = q,/Ir8 = 27t.…”

“…With refined laser cooling methods [11,12], an ambiguous reduction of intra-beam heating [13] was reported for 9 Be+ ion beams. Space-charge limited densities were reached for laser cooled 24 Mg+ ion beams [14], but no clear evidence for beam crystallization has been found in high-energy storage rings so far.…”

“…Cooling now increases the phase space density of the beam, and further amplifies the scattering rate [21,22]. For a given cooling rate, this vicious circle could only be overcome by increasing the number of focusing sections in the storage ring [23,24] to achieve a more continuous focusing, or by choosing a sufficiently low ion density [13]. Once having attained the ordered state with sufficient cooling, this heating mechanism should vanish and the beam should collapse to the crystalline state.…”