Half-life Measurement Experiment Of Fully Stripped ^94mRu At The HIRFL-CSR

Decay of highly charged ions has attracted much attention in recent years. An obvi-ous motivation for this research is that stellar nucleosynthesis proceeds at high temper-atures where the involved atoms are highly ionized, whose half-lives could be largely modified with respect to neutral atoms. The studies of highly charged ions can be per-formed solely at ion storage rings and ion traps, because there high atomic charge states can be preserved for extended periods of time.HIRFL-CSR system is one of the few facilities which can be used to study exotic nuclei. HIRFL-CSR system consists of a main cooler storage ring (CSRm) and an ex-perimental cooler storage ring (CSRe) coupled by a radioactive beam line (RIBLL2).CSRe is not only a cooler storage ring, but also a high precision mass spectrometer.The precision mass measurements of short-lived nuclides have been performed by us-ing isochronous mass spectrometry (IMS) at CSRe in recent years. In this thesis, we report on a novel technique of half-life measurement for fully stripped ion 94,mRu44+by using isochronous mass spectrometry at the CSRe?In the experiment, the ions of insterest were produced in projectile fragmenta-tion of a 376.42 A·MeV 112Sn35+ primary beam on a ?10 mm thick beryllium target.Fragmentation products in the region of interest were selected and passed through the radioactive ion beam line (RIBLL2) and subsequently injected into the CSRe, which was set in the isochronous mode. The passing time of the stored ions were measured by a time-of-flight (TOF) detector installed in the CSRe. The mass value of interested nuclides were extracted from the information of the passing time. Pulse high voltage power supply was used in this experiments for the first time to eliminate the saturation effect of the detector. Pulse high-voltage power supply was set the delay time for 33 seconds. In each injection, we record a total of 200p.s of data for offline analysing.We present various methods for extracting the half-life under different experimen-tal conditions. In addition to the traditional methods, methods applied in conditions when the observation window is narrow and the statistic is poor have been also intro-duced. At the same time, we give each method the specific condition for application.In the data processing, the mass of the target ion has been extracted by using the traditional data analysis method. In the experiment, the mass excess value of 94Ru and 94mRu were determined to be -82531(72) keV and -79905(132) keV, respectively. The excitation energy of the 94 Ru is 2626 (150) keV.The half-life of 4494mRu44+ was measured for the first time. We identified the decay events of 4494mRu44+ by observing the change in the revolution time during the storage and extracted the corresponding decay times. The sensitive window for detection of the decay events is determined to be (20?s, 180?s), and the uncertainty of the decay time is 1 ?s by analysing the simulated data. 49 decay events were identified within the sensitive observation window. After correcting for the fluctuations of the revolution times due to the instability of the magnetic fields, 29 4499mRu44+ ions that did not decay within the recording time were identified, while only 37 decay events remained due to the filter of the correction procedure. A novel calculation method needed to be devel-oped to get the half-life of fully-stripped ions 44mRu44+ to overcome the few statics and narrow observation time. The half-life of 4494mRu44+ was determined to be 97(16)?s in the experiment. Combined with the half-life of neutral atom which value is 71(4)?s,the internal conversion coefficient of neutral atom 94mRu was obtained. At the same time, we tested the systematicness of the mass and half-life of the same neutron number sequence nucleus with our results, and verified that the stripped ion 4494mRu44+was a good spherical nucleus by the deformation parameter B(E2).In this thesis, the mass and half-life of fully stripped 94mRu ion, whose life-time is in the scale of hundreds of microsecond, were measured simultaneously for the first time by using isochronous mass spectrometry. The experiment is conducive to improve the experimental technology of isochronous mass spectrometry in HIRPL-CSR. At the same time, it also provides technical accumulation and experimental experience for future half-life and mass measurement experiments of highly charged ions, whose half-lifes are from hundreds of microsecond to milliseconds.