Speaker
Prof.
Yuhu Zhang
(Institute of Modern Physics, Chinese Academy of Sciences)
Description
The Isochronous Mass Spectrometry (IMS) is a storage-ring-based technique suitable for precision mass measurement of short-lived exotic nuclei produced by relativistic beam fragmentation. Several experiments employing the IMS with one time-of-flight (TOF) detector have been successfully conducted at the experimental storage ring CSRe in Lanzhou, China [1]. In these experiments, the typical magnetic rigidity (Bρ) acceptance of the CSRe is around ±2×10-3 and the momentum compaction factor is about 0.51. The experimental results show that the spectral resolving power of the revolution-time spectrum of the stored ions are not constant over the whole spectrum, and only a part of the whole spectrum corresponding to ΔT/T<0.8 ×10-5 are used for further mass determination.
In order to improve the mass resolving power of the current IMS technique so as to make use of the whole measured revolution-time spectrum, one approach is to limit the momentum spread of the ions to the level of Δp/p=5×10-5 before the injection into the ring [2]. The drawback of this method is that the transmission efficiency of the secondary beam is greatly reduced due to smaller transmission acceptance through the fragment separator [2].
In order to bypass this shortage, an additional velocity measurement of the stored ions in the ring was proposed [3]. In this paper we report the realization of this novel idea in CSRe, namely an upgraded isochronous mass spectrometry with two TOF detectors installed in the straight section of the CSRe. A series of simulated data generated from a dedicated program [4] were analysed using the new method. The velocity precision of the two TOF detector system was assumed to be dv/v≈1.6×10−4 in the simulation. With the additional information of velocity, the revolution-time of all injected ions were corrected to the corresponding revolution-time on the reference orbit. The resulting mass resolving power was greatly improved, especially for nuclides with Lorentz factor far away from the transition point of the CSRe.
[1]H. S. Xu, et al., Int. J. Mass Spectrom. 349–350, 162 (2013).
[2]H. Geissel, et al., Hyperfine Interact. 173, 49 (2006).
[3]P.M. Walker, et al., Technical Proposal for ILIMA, GSI (2005).
[4]R. J. Chen, et al., Phys. Scr. to be published (2014)
Primary authors
Dr
Ruijiu Chen
(Institute of Morden Physics, Chinese Academy of Science)
Mr
Xing XU
(Institute of Modern Physics, Chinese Academy of Sciences)
Co-authors
Prof.
Meng Wang
(Institute of Modern Physics, Chinese Academy of Sciences)
Mr
Peng Shuai
(Institute of Modern Physics, Chinese Academy of Sciences)
Dr
Xinliang Yan
(Institute of Modern Physics, Chinese Academy of Sciences)
Prof.
Yuhu Zhang
(Institute of Modern Physics, Chinese Academy of Sciences)
Prof.
youjing Yuan
(Institute of Modern Physics, Chinese Academy of Sciences)