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The Isochronous Mass Spectrometry (IMS) is a powerful tool for mass measurements of exotic nuclei with half-lives as short as several tens of micro-seconds in storage rings. In order to improve the mass resolving power while preserving the acceptance of the storage ring, the IMS with two Time-Of-Flight (TOF) detectors has been implemented at the storage ring CSRe in Lanzhou, China. Additional velocity information beside the revolution time in the ring can be obtained for each of the stored ions by using the double TOF detector system. In this paper, we introduced a new method of using a 658 nm laser range finder and a short-pulsed ultra-violet laser to directly measure the distance and time delay difference between the two TOF detectors which were installed inside the 1 0 − 11 mbar vacuum chambers. The results showed that the distance between the two ultra-thin carbon foils of the two TOF detectors was ranging from 18032.5 mm to 18035.0 mm over a measurable area of 20 × 20 mm 2. Given the measured distance, the time delay difference which comes with signal cable length difference between the two TOF detectors was measured to be Δ t d e l a y 1 − 2 = 99 (26) ps. The new method has enabled us to use the speed of light in vacuum to calibrate the velocity of stored ions in the ring. The velocity resolution of the current double TOF detector system at CSRe was deduced to be σ (v) ∕ v = 4. 4 × 1 0 − 4 for laser light, mainly limited by the time resolution of the TOF detectors. [ABSTRACT FROM AUTHOR]

A significant deceleration effect on a stored coasting ion beam by a continuous-wave laser light was observed in the Schottky-noise spectrum during the laser experiments with lithium-like oxygen ion beams stored at a relativistic energy of 275.7 MeV/u at the heavy-ion storage ring CSRe in Lanzhou, China. The observed deceleration range of the laser (Δ p / p ≈ 5. 7 × 1 0 − 6 ) is much broader than the expected capture range (Δ p / p ≈ 3. 6 × 1 0 − 8 ), as calculated from the natural linewidth of the O 5 + ion's electronic transition (2 S 1 / 2 − 2 P 1 / 2). In order to explain this huge deviation, a phase space tracking code has been developed to investigate the interaction between the stored coasting ion beam and the laser light. Simulations reveal that the deceleration range of the typically narrow CW laser force is highly enlarged by taking into account the transverse betatron oscillation of the ions with larger emittance and the angular misalignment of the laser light direction. The experimental observation is well described by the systematic simulations. The present work is crucial for forthcoming laser cooling and precision laser spectroscopy experiments and simulations on heavy highly charged ions at the CSRe and the future facility HIAF. [ABSTRACT FROM AUTHOR]