Conditioning the γ spectrometer for activity measurement at very high background

The application of a high purity Germanium (HPGe) γ spectrometer in determining the fuel element burnup in a future reactor is studied. The HPGe detector is exposed by a ⁶⁰Co source with varying irradiation rate from 10× 10³m s^-1 to 150× 10³m s^-1 to simulate the input counting rate in real reactor environment. A ¹³⁷Cs and a ¹⁵²Eu source are positioned at given distances to generate a certain event rate in the detector with the former being proposed as a labeling nuclide to measure the burnup of a fuel element. It is shown that both the energy resolution slightly increasing with the irradiation rate and the passthrough rate at high irradiation level match the requirement of the real application. The influence of the background is studied in the different parameter sets used in the specially developed procedure of background subtraction. It is demonstrated that with the typical input irradiation rate and ¹³⁷Cs intensity relevant to a deep burnup situation, the precision of the ¹³⁷Cs counting rate in the current experiment is consistently below 2.8%, indicating a promising feasibility of utilizing an HPGe detector in the burnup measurement in future bed-like reactors.     

Working principles of the energy measurement system at BEPCⅡ

The proposed beam energy measurement system at BEPCⅡ is composed     

A scenario for high accuracy τ mass measurement at BEPC-Ⅱ

Scenarios for the τ mass measurement at the upgraded Beijing Electron-Positron Collider (BEPC-Ⅱ) are studied. A nested minimization procedure is used to optimize the data taking plan. It is found that by using five energy points with the total integrated luminosity of 100 pb^-1, the τ mass can be determined with a statistical error of 50 keV.     

Study of radiation background at the north crossing point of the BEPCⅡ in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis.     

Study of the data taking strategy for a high precision τ mass measurement

To achieve a high precision τ mass measurement at the high luminosity experiment BESIII,Monte Carlo simulation and sampling technique are utilized to simulate various data taking cases for single and multiparameter fits by virtue of which the optimal scheme is determined. The optimized proportion of luminosity distributed at selected points and the relation between precision and luminosity are obtained. In addition,the optimization of the fit scheme is confirmed by scrutinizing a variety of fit possibilities.