Amplitude and phase stability studies in a DC superconducting injector

The DC superconducting injector will be used in the PKU-THz facility which consists of a DC-gun and a 3+1/2-cell superconducting cavity. The cavity must accelerate the electron beam to 5.82 MeV which is susceptible to perturbations because of its narrow bandwidth. In this paper, the sources and influences of the perturbations in the 3+1/2-cell cavity are discussed. It is shown that the control system is essential for the cavity. The design of a feedback based digital RF low level control system for the 3+1/2-cell cavity is accomplished.     

The cryogenic control system of BEPCⅡ

A superconducting cryogenic system has been designed and deployed in the Beijing Electron-Positron Collider Upgrade Project (BEPCⅡ). The system consists of a Siemens PLC (S7-PLC, Programmable Logic Controller) for the compressor control, an Allen Bradley (AB) PLC for the cryogenic equipments, and the Experimental Physics and Industrial Control System (EPICS) that integrates the PLCs. The system fully automates the superconducting cryogenic control with process control, PID (Proportional-Integral-Differential) control loops, real-time data access and data storage, alarm handler and human machine interface. It is capable of automatic recovery as well. This paper describes the BEPCⅡ cryogenic control system, data communication between S7-PLC and EPICS Input/Output Controllers (IOCs), and the integration of the flow control, the low level interlock, the AB-PLC, and EPICS.     

Upgrade of Control System for the BEPCII

The BEPC will increase its luminosity ten times with upgrade of both the machine and detector,which is the project BEPCII,The project will be started at beginning chine and detector,which is the project BEPCII.The project will be started at beginning of 2002 and finished within 3-4 years.In order to reach the goal of the BEPCII,a number of new equipment will be added in the system,such as the superconducting RF cavities,new magnet power supplies and beam feedback system,and the BEPC control system has to be upgraded.The BEPC control system was built in 1987 and was upgraded in 1994.It is an Open VMS and CAMAC based-system,some equipment is controlled by PCs.We are going to upgrade the existing system by EPICS.Several VME IOCs will be added in the system with feildbus,PLCs for the new equipment control.And we will keep the existing system in use,such as CAMAC hardware ,PC based sub-control and application programs,which will be merged into the EPICS system.Recently the development of the EPICS prototype has been started.Regard some slow control,commercial SCADA product can be chosen as the development tool.We have just finished a prototype with the SCADA product Wizcon.This paper will describe the system design and development issues.     

A tuning system for BEPCⅡ

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 ) has encountered during operation.     

Programming for a Vacuum Remote-control System Based on MSP430F149

A vacuum remote-control system transmits the information of the vacuum equipment‘s controlling and state by use of RS-485 series bus of intranet. The control system module VAC400 adapts MSPF149 of mixture signal process chip produced by TI, which has advantages of ultra-low-power and high-integration. This control net has the characteristics of strong function, simple structure, high reliability, strong resistance of noise, no peripheral chip, etc. The control architecture diagram is shown in Fig.1.     

Control application of a superconducting magnet power supply based on EPICS

The superconducting quadrupole magnets （SCQs） are powered by 16 power supplies in the inter- action region of the BEPC Ⅱ. The control application of these power supplies must be interlocked with the quench protection system to protect the superconducting magnet and relevant devices. This paper describes the development procedures of this control application using EPICS and the operating result with the quench protection system on-site.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

HIRFL-NB1控制系统的设计

通过对新B1聚束器的介绍 ,比较详细地分析了NB1腔体内部组件对谐振频率的影响 ,并以此为依据,阐述了NB1控制系统的设计应如何结合其物理特性 ,最终设计出了一套实时控制系统 .该系统包含RF发射机控制系统和拖动控制系统 ,均可手动和计算机对RF发射机和 5个步进电机实时控制. With the introduction of New Buncher 1 system, the article analyzes the influence that these inner components of the NB1 cavity upon it’s working frequency in detail, and according to the physical characteristics of the NB1 cavity, a set of real time control system will be carried out. The NB1 control system includes RF emitter control and moving system control, which both have local control and computer control on RF emitter and five stepping motors.     

RF system design and measurement of HIRF-CSRe

An RF system for the CSRe （cooling storage experimental ring） is designed and manufactured domestically. The present paper mainly describes the RF system design in five main sections： ferrite ring, RF cavity, RF generator, low level system and cavity cooling. The cavity is based on a type of coaxial resonator which is shorted at the end with one gap and loaded with domestic ferrite rings. The RF generator is designed in the push-pull mode and the low level control system is based on a DSP＋FGPA＋DDS＋USB interface and has three feedback loops. Finally we give the results of the measurement on our system.     

Control system for the CSNS ion source test stand

A penning plasma surface H- ion source test stand for the CSNS has just been constructed at the IHEP. In order to achieve a safe and reliable system, nearly all devices of the ion source are designed to have the capability of both local and remote operation function. The control system consists of PLCs and EPICS real-time software tools separately serving device control and monitoring, PLC integration and OPI support. This paper summarizes the hardware and software implementation satisfying the requirements of the ion source control system.     

新型低beta超导腔调谐算法分析与测试

为了使腔体在复杂电磁环境下处于谐振状态,保持超导腔加速电压的幅度相位稳定,研发了一种应用于自激锁相模式的腔体新型调谐算法。利用正交电压Q值控制调谐器调谐,从而消除了输入和输出间的相位误差,给出了理论推导过程与该算法的可靠性分析。该算法已应用于中国科学院近代物理研究所ADS项目超导加速器中,简化了传统控制模式中的信号采样数量,提高了系统控制精度与抗干扰能力,使腔体克服了在调谐过程中由于功率上冲引起的氦压波动。保证了超导腔在工作状态下,频率稳定在162.5 MHz,频率误差小于17 Hz。For the purposes of keeping the resonant cavity steady in a complex electromagnetic environment and maintaining stable amplitude and phase, a new tuning algorithm for superconducting RF cavity operated in self-excited phase-locked mode has been developed. The quadrature voltage was employed to control the tuner under the phase-locked condition, so as to eliminate phase measurement between the input and the output. This paper demonstrates the principle of this "Minimum Q" tuning algorithm and presents an analysis of the stability of the system. The algorithm is applied to the superconducting accelerator of the Institute of Modern Physics' ADS project. The "Minimum Q" tuning algorithmnot only simplifies the number of signal sampling but also improves the control accuracy and anti-interference ability of the system, while enables the cavity to overcome the helium pressure fluctuation which caused by power overshoot. It ensures that the frequency of the superconducting cavity is stable at 162.5 MHz, and the frequency error is less than 17 Hz.     

Resonant interaction scheme for GHZ state preparation and quantum phase gate with superconducting qubits in a cavity

A scheme is proposed to generate GHZ state and realize quantum phase gate for superconducting qubits placed in a microwave cavity. This scheme uses resonant interaction between the qubits and the cavity mode, so that the interaction time is short, which is important in view of decoherence. In particular, the phase gate can be realized simply with a single interaction between the qubits and the cavity mode. With cavity decay being considered, the fidelity and success probability are both very close to unity.     

Study on the HOMs coupler design of spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of high power proton linac for an Accelerator Driven Sub-critical System (ADS). Considering that the High Order Modes (HOMs) in the superconducting cavity have far reaching influence on power dissipation and beam stability, the analysis of HOMs of the spoke cavity is needed. In this paper, we put emphasis on the analysis of HOMs of the spoke cavity and the HOMs coupler design.     

Design of BEPCⅡ bunch current monitor system

BEPCⅡ is an electron-positron collider designed to run under multi-bunches and high beam current condition. The accelerator consists of an electron ring, a positron ring and a linear injector. In order to achieve the target luminosity and implement the equal bunch charge injection, the Bunch Current Monitor (BCM) system is built on BEPCⅡ. The BCM system consists of three parts: the front-end circuit, the bunch current acquisition system and the bucket selection system. The control software of BCM is based on VxWorks and EPICS. With the help of BCM system, the bunch current in each bucket can be monitored in the Central Control Room. The BEPCⅡ timing system can also use the bunch current database to decide which bucket needs to refill to implement ``top-off' njection.     

An ADS 650 MHz medium beta cavity study and design

The Accelerator Driven Sub-critical System (ADS) is under development and aims at the safe disposal of nuclear waste and providing electric power in China. The main accelerator of the ADS is composed of two injector sections and one main linear acceleration section. The 650 MHz β=0.82 superconducting cavities will be adopted to accelerate the proton bunches from 360 MeV to 1.5 GeV in the medium energy section. This paper presents the study and design results of this kind of superconducting cavity.     

Efficient Scheme for Entanglement and Quantum Information Processing with Two Superconducting Quantum-Interference Devices in Cavity QED

In this paper, a scheme is proposed to create the entanglement of two superconducting quantum-interference devices （SQUIDs） and implement a two-quhit quantum phase gate between two SQUIDs in cavity. The scheme only requires resonant interactions. Thus the scheme is very simple and the quantum dynamics operation can he realized at a high speed, which is important in view of decoherence.     

Cavity-induced ATS effect on a superconducting Xmon qubit

We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler–Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.     

Low beta spoke cavity multipacting analysis

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.     

ADS 650 MHz medium beta cavity study and design

The Accelerator Driven Sub-critical System (ADS) is under development aiming at safe disposal of nuclear waste and providing electric power in China. The main accelerator of ADS is composed of two injector sections and one main linear acceleration section. The 650 MHz β=0.82 superconducting cavities will be adopted to accelerate the proton bunches from 360 MeV to 1.5 GeV in the medium energy section. This paper presents the study and design results of this kind of superconducting cavity.