Fluoride salt-cooled high-temperature reactors(FHRs) include many attractive features, such as high temperature, large heat capacity, low pressure and strong inherent safety. Transient characteristics of FHR are particularly important for evaluating its operation performance. Thus, a specialized code OCFHR(operation and control analysis code of FHR) issued to study an experimental FHR’s operation behaviors. The geometric modeling of OCFHR is based on one-dimensional lumped parameter method, and some simplifications are taken into consideration during simulation due to the existence of complex structures such as pebble bed, intermediate heat exchanger(IHX), air radiator(AR) and multiply channels.A point neutron kinetics model is developed, and neutron physics calculation is needed to provide some key inputs including axial power density distribution, reactivity coefficients and parameters about delayed neutron precursors. For analyzing the operational performance, five disturbed transients are simulated, involving reactivity step insertion, variations of coolant mass flow rate of primary loop and intermediate loop, adjustment of air inlet temperature and mass flow rate of air cooling system.Simulation results indicate that inherent self-stability of FHR restrains severe consequences under above transients,and some dynamic features are observed, such as large negative temperature feedbacks, remarkable thermal inertia and high response delay.

A 325 MHz β=0.14 superconducting half-wave resonator prototype has been developed at the Institute of High Energy Physics,Beijing,which can be applied in the low energy section of continuous wave high current proton linear accelerators.The electromagnetic design,multipacting simulation,mechanical optimization and fabrication are introduced in detail.Test results at room temperature and 4.2 K,and a comparison between measured and simulated results,are analyzed in this paper.

In the digital low level RF (LLRF) system of a circular (particle) accelerator, the RF field signal is usually down converted to a fixed intermediate frequency (IF). The ratio of IF and sampling frequency determines the processing required, and differs in various LLRF systems. It is generally desirable to design a universally compatible architecture for different IFs with no change to the sampling frequency and algorithm. A new RF detection method based on a double heterodyne architecture for wide IF range has been developed, which achieves the high accuracy requirement of modern LLRF. In this paper, the relation of IF and phase error is systematically analyzed for the first time and verified by experiments. The effects of temperature drift for 16 h IF detection are inhibited by the amplitude and phase calibrations.

A 325 MHz low beta half wave resonator (HWR) for proton accelerator was designed. The study on the principle of designing a superconducting cavity was described. The modeling on a new HWR was performed on different parts, then the electromagnetic analysis of the HWR was implemented. In the process of cavity design, parametric modeling was used to construct the cavity shape, then curved tetrahedral mesh cells were used to fulfill the EM calculation, and parameters sweeping was used to optimize the RF parameters of HWR superconducting cavity. The HWR cavity shape was also analyzed by means of multipacting calculation using TRACK3P code. Satisfied RF parameters were achieved on the new designed 325 MHz low beta HWR cavity. The new HWR cavity will be fabricated after more analysis and it may be applied to the linac for proton accelerator in the future.

Tuning system plays a very important role when superconducting cavity works. It cooperates with other control loops, to adjust the frequency of cavity with high precision, reduce the reflection power, guarantee the stability of beam and ensure the safety of superconducting cavity. This paper focuses mainly on the tuning system working principle, the working state and problems that BEPC (Beijing Electron Positron Collider) II has encountered during operation.

The simulation and analysis for electron multipacting phenomenon in a low β spoke superconducting cavity in ADS proton accelerator are proposed. Using both CST and Track3P codes, the electron multipacting calculation for β=0.12 spoke superconducting cavity is implemented. The methods of multipacting calculation on both codes are studied and described. With the comparison between the calculation results and the cavity vertical test result, the accuracy and reliability of different codes on calculating multipacting are analyzed. Multipacting calculation can help to understand the results of vertical test and also can help to do the optimization in cavity design.

China ADS is a high intensity proton machine based on CW superconducting technology. It includes two injectors and one main linac. The Institute of High Energy Physics (IHEP) and the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), are responsible for developing the main linac together. This paper introduces the physics and mechanical design of the single spoke resonator (SSR021, beta021 cavity), which is used for first section of the main linac.

The Half-Wave Resonator (HWR) has been widely used in proton and heavy ion accelerators, for it has particular advantages of accelerating low energy charged particles. Preliminary design of a 325 MHz β=0.12 superconducting HWR cavity has been proposed at Institute of High Energy Physics (IHEP). The basic geometric parameters choices of the cavity are based upon theoretical model and numerical calculation, and then the RF performances are optimized by extensive electromagnetic simulations. In this paper, the detailed mechanical analysis, frequency control, and the considerations for fabrication of the 325 MHz HWR cavity are also presented.

The extremely low temperature in Antarctic inland area has taken a new challenge for telescope design and develop, the adaptability of components and parts in telescope for the environment close to space. The application of high accuracy encoder is the only way to improve the accuracy of tracking, however, due to the temperature requirement, there is no application of encoder under such a low temperature ever since. To realize the high accuracy of tracking and steering in telescope, high accuracy encoders must be applied in it. Based on the analysis of influence on encoder caused by temperature, an initial thermal control measure is carried out. Secondly, the thermal control measure is optimized with the method that consists of CFD simulations and experiments. Finally, an effective thermal control measure is applied on the second telescope of the 3 Antarctic Schmidt Telescopes (AST3). By the comparison of normal temperature experiment and low temperature experiment, the encoder can reach a temperature of about 25 degrees when it is under the circumstance of-80 degrees after the thermal control works, and the power consumes by the thermal control is less than 6W. The experiment result indicates that the thermal control measure can fit the requirement of temperature that ranges from-10 degrees to 80 degrees and the lowly consuming power requirement, the encoder can reliably work in low temperature with the thermal control measure works.

The tuning system plays a very important role when a superconducting cavity is in operation. It cooperates with other control loops to adjust the cavity frequency with high precision, reduce the reflection power, guarantee the stability of beam, and ensure the safety of the superconducting cavity. This paper focuses mainly on the tuning system working principle, the working state and problems that Beijing Electron Positron Collider (BEPC II) has encountered during operation.

Oxide transistor is the basic device to construct the oxide electronic circuit that is the backing to develop integrated oxide electronics with high efficiency and low power consumption. By growing the perovskite oxide integrated layers and tailoring them to lead semiconducting functions at their interfaces, the development of oxide transistors may be able to perform. We realize a kind of p-i-n type integrated layers consisting of an n-type cuprate superconductor, p-type colossal magnetoresistance manganite, and a ferroelectric barrier ( i). From this, bipolar transistors were fabricated at the back-to-back p-i-n junctions, for which the Schottky emission and p-n junction barriers, as well as the ferroelectric polarization, were integrated into the interfaces to control the transport properties; a preliminary but distinct current gain greater than 1.6 at input current of microampers order was observed. These results present a real possibility to date for developing bipolar all perovskite oxide transistors.

The horizontal test for BEPCII 500MHz spare cavity has been completed in IHEP. The max voltage of the cavity is 2.17MV, Q0 is 5.78\times108.This paper mainly reports coupler aging parameters before the horizontal test, as well as the parameters during cool-down the change of frequency, loaded Q, vacuum and the deformation of the cavity with temperature. And the test results were analyzed.

To test and verify the performance of the digital low-level radio-frequency (LLRF) and tuner system designed by the IHEP RF group, an experimental platform with a retired KEK 1.3 GHz nine-cell cavity is set up. A radio-frequency (RF) field is established successfully in the cavity and the frequency of the cavity is locked by the tuner in ±0.5° (about ±1.2 kHz) at room temperature. The digital LLRF system performs well in a five-hour experiment, and the results show that the system achieves field stability at amplitude <0.1% (peak to peak) and phase <0.1° (peak to peak). This index satisfies the requirements of the International Linear Collider (ILC), and this paper describes this closed-loop experiment of the LLRF system.

A flexible high power RF test stand has been designed and constructed at IHEP to test a variety of 500 MHz superconducting RF components for the upgrade project of the Beijing Electron Positron Collider (BEPC II), such as the input coupler, the higher order modes (HOMs) absorber and so on. A high power input coupler has been conditioned and tested with the RF power up to 250 kW in continuous wave (CW), traveling wave (TW) mode and 150 kW CW in standing wave (SW) mode. A prototype of the HOMs absorber has been tested to absorb power of 4.4 kW. An introduction of the test stand design, construction and high power tests is presented in this paper.

采用CST软件的粒子工作室模块,对spoke超导腔中可能发生的二次电子倍增效应进行了分析研究,并采用二次电子倍增效应发生后形成稳定状态时的粒子数增长率来表征其强度.模拟计算表明:该腔存在两处二次电子倍增效应,spoke柱两端的两点一阶倍增；spoke腔两端侧壁与中心圆筒交界处的单点一阶倍增；二次电子倍增在加速腔压为0.65MV时的增长率最高,而腔压大于1 MV时,增长率均为负,即无倍增发生.

Since Nov. 2006, the 500MHz SRF system of Beijing electron positron collider upgrade (BEPCII) has been running stably. But there’s a hidden danger for no spare cavity is existed. If there’s any serious trouble happened on either one of the two operating cavities and cannot be recovered in time, it will affect the operation of BEPCII facility. Spare cavities began to be investigated since 2009. Now three cavities are developed and two of them have been vertical tested at Jan and July 2011, respectively. This paper will briefly present the manufacturing, post-processing and vertical test performance of the cavity.

We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in Fe Se superconducting thin films is not observed in the superconducting FeTe thin films The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.

The RF system for the Beijing Electron Positron Collider Upgrade (BEPC II) Project had been working since Nov, 2006. It consists of 3 subsystems including the superconducting cavity, the klystron and the low level RF system. Compared with the former RF system, the operating frequency has been changed from 200MHz to 499.8MHz, and the superconducting cavity has been used to replace the normal cavity. Up to now, the RF system performance is good and achieves the designed target.

The BEPC RF system has been changed to superconducting cavities during the last four years. In the Summer of 2006, the high power test had been successfully carried. In November, the East RF was put into commissioning. The SRF system above 1.0MV voltage has been reached with the e(+)/e(-) collision beam over 100mA, and the beam current improved to 2.5GeV/250mA with 100kW beam power. The beam test shows the good matching of the RF parameters with measuring value and theoretic calculation. The commissioning and the high power test will be presented in this paper.