Ming He

Measurement of the half-life of 79Se with PX-AMS

Abstract The half-life of 79Se has been re-measured with projectile X-rays detection (PXD) in accelerator mass spectrometry after a new PXD system had been set up in China Institute of Atomic Energy (CIAE). The PXD technique has been used for separation of 79Se from its isobar, 79Br. The detection efficiency of 79Se Kα X-rays is obtained from that of 80Se after energy correction. The atom number of 79Se in each sample is deduced from the measured ratios of 79Se/Se. From the measured decay rates of each sample, the half-life is deduced to be (2.80±0.36)×105 a. In order to check the reliability of the result of 79Se half-life, the 75Se half-life is also measured with PX-AMS method. The measured half-life of 75Se is in good agreement with well-known literature value.

Development of AMS measurements and applications at the CIAE

Abstract The HI-13 tandem accelerator in the China Institute of Atomic Energy (CIAE) is a multi-user facility. Only a small part of the beam time can be used for AMS. So, it is impossible to measure very many samples and to carry out wider applications by using the HI-13 tandem AMS system. Therefore, we focus our studies on the development of measurement and detection methods and several interesting applications utilizing the long-lived radionuclides 26Al, 41Ca, 36Cl and 79Se.

Measurement of and with PXAMS

Abstract A projectile X-ray accelerator mass spectrometer (PXAMS) system has been set up at the China Institute of Atomic Energy (CIAE). The first applications were the measurement of the 79 Se half-life and the analysis of a radioactive 64 Cu beam and its contaminating components. The improved detection limit for 79 Se / Se is of the order of 10−9.

Re-measurement of the half-life of 79Se

Abstract A new attempt has been made for the re-measurement of the half-life of 79 Se. We made two major improvements over our earlier 79 Se half-life determination (Nucl. Instr. and Meth. B 123 (1997) 403). Firstly, the half-life of 79 Se was measured relative to the precisely known half-life of 75 Se, rather than an absolute measurement of 79 Se/Se. Secondly, the Projectile X-ray Detection technique was used for the separation of 79 Se from its isobar, 79 Br, rather than measuring 81 Br for the deduction of 79 Br interference, and this technique was also used for separation of 75 Se and its isobar, 75 As. A detailed description of the sample preparations, experimental setup and measurements are given. The re-measured half-life of 79 Se was (2.95±0.38)×10 5 xa0a, about a factor of 3 lower than the previous value, 1.1×10 6 xa0a. The problems in the previous measurement are discussed.

A gas-filled time-of-flight detector system and a new method for particle identification

In order to increase the power of isobaric identification in accelerator mass spectrometry (AMS) measurements, we built a new gas-filled time-of-flight (GF-TOF) detector system (Jiang et al.). The principle, construction and results of first on line tests with a Cu sample are described. Based on the GF-TOF detector system, we also propose a new particle identification method called energy-loss and time-of-flight (ΔE–T) parabola. The principle of the method and the first test for the method with the 36Cl AMS measurement are described.

Coulomb excitation with radioactive nuclear beam of 64Cu

Abstract The radioactive nuclear beam of 64Cu was obtained utilizing a two-stage method at the HI-13 tandem accelerator of China Institute of Atomic Energy. The B(E2) value of the first excitation state of 64Cu has been directly measured for the first time by Coulomb excitation method, using the radioactive nuclear beam of 64Cu. An upper limit of the B(E2;21+→1gs+) value from the first excitation state to the ground state of 64Cu is determined to be 49xa0W.u., which is significantly smaller than 250±170xa0W.u., the value adopted by Nuclear Data Sheets. The reliability of the experimental method was verified by simultaneously performing the Coulomb excitation experiment of 181Ta.