Qin Zeng

Identification of the Lowest T =2, Jπ =0+ Isobaric Analog State in 52Co and Its Impact on the Understanding of β-Decay Properties of52Ni

Masses of ^{52g,52m}Co were measured for the first time with an accuracy of ∼10  keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous β-γ measurements of ^{52}Ni, the T=2, J^{π}=0^{+} isobaric analog state (IAS) in ^{52}Co was newly assigned, questioning the conventional identification of IASs from the β-delayed proton emissions. Using our energy of the IAS in ^{52}Co, the masses of the T=2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in ^{52}Co decays predominantly via γ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.

Neutronics analysis for the test blanket modules proposed for EAST and ITER

The dual-functional lithium lead-test blanket module (DFLL-TBM) system, which is designated to demonstrate the integrated technologies of both the He single coolant (SLL) blanket and the He-LiPb dual coolant (DLL) blanket, is proposed for testing in ITER to check and validate the feasibility of the Chinese LiPb blankets. Considering the conflict between the limited ITER resources for TBM testing and the requirement of various blanket concepts proposed by the parties, EAST, the superconducting tokamak being operated in China, can serve as a valuable pre-testing platform with some comparable design parameters to ITER for DFLL-TBM. In the contribution, neutronics calculations and activation of the TBMs in EAST are carried out and compared with those in the D–D and D–T phase of ITER. The results from EAST can make an analogy to ITER (to some extent).

An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors

Abstract Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.

First isochronous mass measurements with two time-of-flight detectors at CSRe

Isochronous mass spectrometry (IMS) established in heavy-ion storage rings has proven to be a powerful tool for mass measurements of short-lived nuclides. In IMS, the revolution times of stored ions should be independent of their velocity spread. However, this isochronous condition is fulfilled only in the first order and in a small range of revolution times. To correct for non-isochronicity, an additional measure of the velocity or magnetic rigidity of each stored ion is required. For this purpose two new time-of-flight (TOF) detectors were installed in one of the straight sections of the experimental cooler storage ring in Lanzhou. It is expected that the resolving power of the IMS will significantly be improved with such a double-TOF arrangement. The double-TOF system was tested in a recent experiment with the Kr-78 fragments. Some of the experimental results are presented in this contribution.

Simulations of the isochronous mass spectrometry at the HIRFL-CSR

A Monte-Carlo simulation code, named as SimCSR, has been developed for the isochronous mass spectrometry experiments in the experimental storage ring (CSRe). The revolution times of the fragments ions stored in the CSRe, which were produced in the fragmentation of Ni-58 primary beam are reproduced very well by the SimCSR, although only linear components are considered. The standard deviation of the revolution time is found to be strongly affected by the phase slip factor, the width of the relative momentum difference and the instability of magnetic field. Based on the simulations, we outline and discuss the methods to reduce the standard deviation of the revolution time.

A method to measure the transition energy γ t of the isochronously tuned storage ring

Abstract The Isochronous Mass Spectrometry (IMS) is a powerful technique developed in heavy-ion storage rings for measuring masses of very short-lived exotic nuclei. The IMS is based on the isochronous setting of the ring. One of the main parameters of this setting is the transition energy γ t . It has been a challenge to determine the γ t and especially to monitor the variation of γ t during experiments. In this paper we introduce a method to measure the γ t online during IMS experiments by using the acquired experimental data. Furthermore, since the storage ring has (in our context) a relatively large momentum acceptance, the variation of the γ t across the ring acceptance is a source of systematic uncertainty of measured masses. With the installation of two time-of-flight (TOF) detectors, the velocity of each stored ion and its revolution time are simultaneously available for the analysis. These quantities enabled us to determine the γ t as a function of orbital length in the ring. The presented method is especially important for future IMS experiments planned at the new-generation storage ring facilities FAIR in Germany and HIAF in China.

The Testing and Application of Continuous-Energy Neutron Cross Section Library HENDL-ADS/MC

A point-wise cross-section data library HENDL-ADS/MC (Hybrid Evaluated Nuclear Data Library) has been produced by FDS team to do the nuclear analysis for the ADS system. The HENDL-ADS/MC library contained 408 nuclide cross-section files including actinides, fission products and structural materials for neutron energy up to 150 MeV. The nuclear library also contained several sub-libraries with different temperatures. A series of neutron integral experiments and critical safety benchmarks have been performed to test the availability and reliability of the HENDL-ADS/MC data library. To validate and qualify the reliability of the high neutron energy cross section for HENDL-ADS/MC library further, a series of high neutron shielding experiments have been performed using MCNP. The testing results indicated the accuracy and reliability of HENDL-ADS/MC library.Copyright

Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and νp nucleosynthesis processes

Abstract Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of 82Zr and 84Nb were measured for the first time with an uncertainty of ∼10 keV, and the masses of 79Y, 81Zr, and 83Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr–Nb cycle in the rp-process unlikely. The new proton separation energy of 83Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus 84Sr relative to the neutron-deficient molybdenum isotopes in the previous νp-process simulations.

Masses of the Tz = −3/2 nuclei 27P and 29S

Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the

Application of Isochronous Mass Spectrometry for the study of angular momentum population in projectile fragmentation reactions

T_z=-3/2