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Free keywords:
Physics, Atomic Physics, physics.atom-ph, Physics, Accelerator Physics, physics.acc-ph, Physics, Atomic and Molecular Clusters, physics.atm-clus, Physics, Chemical Physics, physics.chem-ph
MPINP:
Speichertechnik - Abteilung Blaum
MPINP:
Expt. CSR - Abteilung Blaum
Abstract:
An electrostatic cryogenic storage ring, CSR, for beams of anions and cations<br>with up to 300 keV kinetic energy per unit charge has been designed,<br>constructed and put into operation. With a circumference of 35 m, the ion-beam<br>vacuum chambers and all beam optics are in a cryostat and cooled by a<br>closed-cycle liquid helium system. At temperatures as low as (5.5 +/- 1) K<br>inside the ring, storage time constants of several minutes up to almost an hour<br>were observed for atomic and molecular, anion and cation beams at an energy of<br>60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts<br>(dispersion) and the focusing properties of the machine were studied by a<br>system of capacitive pickups. The Schottky-noise spectrum of the stored ions<br>revealed a broadening of the momentum distribution on a time scale of 1000 s.<br>Photodetachment of stored anions was used in the beam lifetime measurements.<br>The detachment rate by anion collisions with residual-gas molecules was found<br>to be extremely low. A residual-gas density below 140 cm<supp>-3</sup> is derived,<br>equivalent to a room-temperature pressure below 10<sup>-14</sup> mbar. Fast atomic,<br>molecular and cluster ion beams stored for long periods of time in a cryogenic<br>environment will allow experiments on collision- and radiation-induced<br>fragmentation processes of ions in known internal quantum states with merged<br>and crossed photon and particle beams.<br>
