Unsteady numerical simulation on helium cooldown process for the 650 MHz two-cell superconducting cavity Abstract Background Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone (4.2 K and below) in the testing and sophisticated operation process of superconducting cavity. Purpose The purpose of this paper is to study the cooling law on the helium cooldown process for the 650 MHz two-cell superconducting cavity with the unsteady numerical simulation. Method A three-dimensional coupled heat-flow model of 650 MHz two-cell superconducting cavity was established. The unsteady numerical simulation of different inlet temperatures, flow rates and pressure conditions was carried out. The equivalent convective heat transfer coefficient and temperature distribution of 650 MHz two-cell superconducting cavity during cooldown process were obtained. The effects of cooling time and entrance parameters on the cooldown process were analyzed. Results The temperature distribution of the lower intersection lines has a large drop in the initial stage of cooldown process (120 s), while the temperature near the flanges at the both ends is still higher (remaining at the initial temperature of 300 K). With the passage of time, the temperature of the upper and lower intersection lines decreases. The maximum temperature difference on the lower intersections is within 2 K in the final stage of cooldown process (3600 s). The maximum temperature difference increases by 180%, and the difference between the maximum temperature and the minimum temperature (dT) at the end of a cooldown stage increases by 130% after 1 h, respectively, when the inlet temperature drops from 290 to 270 K (under the condition of the initial temperature of 300 K). Conclusions The maximum temperature difference and the dT at the end of a cooldown stage increase with the decrease in the inlet temperature. The maximum temperature difference increases with the increase in the inlet flow rate, while the dT at the end of a cooldown stage decreases with the increase in the inlet flow rate. The effect of changing the inlet flow rate on the cooling rate is not as obvious as changing the inlet temperature. Once there is a certain flow rate, the advantage of further increasing the flow rate to reduce the temperature of the superconducting cavity is not so great.

Natural radioactivity measurements of frozen red meat samples consumed in Iraq Abstract Purpose In the present study, the activity concentrations of long-lived gamma-ray emitters (238U, 232Th and 40K) in ten different types of frozen red meat samples selected from markets in Iraq were measured. Methods The technique of gamma spectrometer equipped with scintillation detector NaI (Tl) was used. Results The annual effective dose was estimated in adults and kids. The results showed that the concentrations of 238U, 232Th and 40K were found in the range of permissible limits of 30, 32 and 400 Bq kg−1, respectively. On the other hand, the maximum values of 238U and 232Th in beef samples are higher than in lamb meat samples. The annual effective dose of adults and kids was observed to be below the limit (1.0 mSv) recommended by ICRP. Conclusion The frozen red meat samples are safe for human consumption and have gamma-ray emitter concentrations lower than the maximum permissible levels.

Design of LEAF control system Abstract Background LEAF is a complicated and integrated facility, which includes several different subsystems. In order to realize the remote control of field equipment and meet the requirements of the beam commissioning, a LEAF control system has been designed. The developed control system includes the following sub-systems: timing systems, data archiving systems, personnel safety systems, and machine protection systems. Methods The control system for LEAF is developed using the EPICS software toolset and the distributed control architecture. This is designed in a three-layer structure. At the equipment layer, the control of the low-level equipment is mainly done by various industrial controllers, including programmable logic controllers, controllers for serial devices, and motion controllers based on EtherCAT fieldbus. At the middle layer, the Ethernet switches are used to implement a Gigabit local area network. At the operation layer, high-level application software has been developed for the beam commissioning and the operation of the accelerator. Results The designed system can realize remote monitoring and control of field devices, provide synchronous timing and machine protection for key equipment, and automatically archive historical data for on-site running equipment. Conclusion The complete system has a clear structure and stable operation and has been successfully applied to beam commissioning and operation of the LEAF facility.

The offline data quality monitoring of the BESIII end cap TOF system Abstract Purpose The end cap time of flight (TOF) at Beijing spectrometer was upgraded with multi-gap resistive plate chamber technology in order to improve the particle identification capability in 2015. The offline data quality monitoring is a critical aspect of the data processing chain aiming at providing data with good quality for physics analyses. Methods An offline data quality monitoring tool for upgraded end cap TOF has been developed to provide feedback about the functioning and performance of detector hardware and data processing chain. Results Detector information and reconstructed time-of- flight characteristics of charged tracks are filled into plots using full Bhabha events reconstruction results, and then, these plots are used to assess the operational conditions of the detector and the quality of the data by the experts. Conclusion This paper is describing the design and the content of performance of the offline data quality monitoring of end cap TOF and the data quality performance achieved during last 2 years’ physical data taking.

RF design of a compact 648 MHz single spoke cavity at CSNS Abstract Purpose In order to increase CSNS beam power from 100 to 500 kW, the linac injection energy needs to be increased from 80 to 300 MeV. The combined layout of superconducting spoke cavities and elliptical cavities will be adopted to accelerate H− beam to 300 MeV. In this paper, a compact single spoke cavity with Φ50-mm beam aperture was proposed, with the RF performance of the spoke cavity optimized to Ep/Eacc < 5, Bp/Eacc < 9, as well as the good multipacting behavior. Methods CST Microwave Studio was used to optimize the RF performance (Epeak/Eacc, Bpeak/Eacc, R/Q) with cavity geometry parameters. After electromagnetic design was finished, multipacting behavior was studied with CST Particle Studio module, and cavity shape modification was made to get a reasonable <SEY> value. Results The simulation got optimum results of Epeak/Eacc = 4.97 and Bpeak/Eacc = 8.42 mT/(MV/m), and the <SEY> max is 1.52 at Eacc = 7.74 MV/m. Conclusion A 648 MHz βg = 0.4 single spoke cavity with beam aperture Φ50 mm was proposed in the paper. This compact cavity may be a very promising option for CSNS linac upgrading. In addition to the optimization of the RF parameters, the multipacting behavior of the cavity is also studied, and cavity shape is optimized to reduce <SEY> value.

Indirect cooling experiment for magnetic alloy-loaded cavity Abstract Background Indirect cooling method is an alternative scheme for magnetic alloy (MA)-loaded cavity because of the feasible structure and MA core treatment process. Stable and long-term operation is not possible without a powerful cooling system for the high-power MA cavity. Purpose The paper reports a method to evaluate the cooling efficiency of an indirect cooling structure for high-power-loss MA cavity. Methods Two types of helix metallic cooling plate were designed and checked by CFX code considering the average power loss more than 0.13 W/cc. In order to enhance the heat-transfer efficiency between the non-flatness surface of the MA core and metallic cooling plate, a filling material with high thermal conductivity is needed. Different commercial filling materials were investigated, and a high-power test bench was developed to assess the cooling efficiency. A parametric fitting method was adopted to qualify the heat-transfer coefficient according to the temperature rising curve. Conclusion The results indicate that the experimental data maintain good consistency with the CFX simulation results and the cooling structure meets the high-power-loss cooling requirement. The heat-transfer capability of the filling was influenced by the thickness of heat-transfer materials and the painting process. The heat-transfer performance of the thermal grease is better than that of the thermal gasket even though the latter has a higher thermal conductivity. The virtual thermal conductivity of the filling material was less than the product index and affirmed by the CFX transient simulation.

Study on the area ratio of Nb–Sn target for the preparation of Nb 3 Sn films Abstract Introduction Niobium is extremely important in SRF cavities because of its superconducting properties. However, there are some intrinsic limits of Nb cavities that cannot meet the requirements of future accelerators. It is therefore of utmost importance to look into materials offering SRF performances beyond niobium. Nb3Sn is the most promising material. In our work, the cathode target is cylindrical and rotatable, containing both Nb and Sn elements, which are simultaneously charged, aiming to explore the area ratios of the two elements required in the cathode target by simulation and experiments, respectively. This work will provide the basis for the subsequent Nb3Sn cathode target fabrication. Simulations and experiments In the simulation, we calculated stoichiometric ratio and sputtering yield to obtain the area ratios of Nb and Sn. In the experiment, we calculated the rotation rate of the target, deposition thickness of films on substrates and deposition rate to obtain the area ratio of Nb and Sn. Conclusion In conclusion, we compared the simulation and experimental results and found that they are in good agreement. The simulation and experimental results also showed that the area ratio of Nb to Sn in the target is close to 9:1. These results lay the foundation for the subsequent Nb3Sn cathode target fabrication and multilayer deposition of Nb3Sn thin films.

A low-cost slow control system for the PandaX-4T experiment Abstract Background The PandaX-4T experiment is a next-generation dark matter search program located in the China Jinping Underground Laboratory. To ensure the stability of the complex instrument during the planned operation, the status of the facility should be monitored continuously. Purpose The paper reports the design of the slow control system for the experiment. The system is used to monitor the facility status and generate an alarm signal while the detector is in abnormal status. Methods Low-cost hardware is employed for the distributed data collection. Python-based data collection program was developed. We also used the open source software for data storage, visualization and anomaly detection, so that the development of the system is simplified. Conclusion We finally achieved a low-cost and robust slow control system for the prototype detector in short time. It is running well currently. The system will be integrated with the PandaX-4T facility in late 2019.

The C 6 D 6 detector system on the Back-n beam line of CSNS Abstract Introduction The neutron capture cross sections are very important in the field of nuclear device design and basic physics research. Hydrogen-free liquid scintillator such as C6D6 detectors are widely used in the neutron capture cross-sectional measurements for the low neutron sensitivity and fast time response. The Back-n white neutron source at China Spallation Neutron Source is the first spallation white neutron source in China, and it is suitable for neutron capture cross-sectional measurement. Materials and methods A C6D6 detector system was built in the Back-n experimental station. The pulse height weighting technique was used to determine the system’s detection efficiency. The response to gamma rays of the C6D6 detector was measured, and the energy resolution function was determined. Monte Carlo simulation with Geant4 code was carried out to get the weighting function of this C6D6 detector system. Additionally, the systematic uncertainty of the weighting function was also determined. Conclusion According to the experimental and simulation results, this C6D6 detector system can be used to measure neutron capture cross section.

Development of new beam current transformer based on TMR Abstract Purpose and background As the magneto-resistor technology is developed, applying it to beam instrumentation for the accelerator becomes possible. In this paper, a new principle beam current sensor based on TMR linear sensor is introduced. Methods Feasibility research by simulation and calculation has been done, a study of the critical component for the whole system has been carried out, and all these are presented in this paper. Results and conclusions Laboratory test results include the nonlinear error, and resolution analysis is introduced. Specific work plan for the next step of the improvement and upgrade is also referred to.