Precision measurement of the transition energy γt versus magnetic rigidity for storage-ring isochronous mass spectrometry

The transition energy, γt, of a heavy-ion storage ring is an important machine parameter. The variation of γt versus the magnetic rigidity, Bρ, over the acceptance of the ring directly affects the mass resolving power achievable in the high-precision isochronous mass spectrometry (IMS). With two time-of-flight (TOF) detectors installed in a straight section of the ring, revolution frequency (revolution time) and velocity of each stored ion can simultaneously be measured. By using these quantities, a method for fast and precise γt determinations has been developed. The dependence of γt on the orbit length (or Bρ) has been obtained. The newly developed method does not require particle identification and is thus suitable for real-time monitoring of the ion optical setting during experiment.