Mingwu Fan

Terahertz radiation sources based on free electron lasers and their applications

The tunability, high power and flexible picoseconds-pulse time structure of terahertz (THz) radiation make the THz free-electron laser (FEL) a very attractive THz source of coherent radiation. This paper focuses on the development and perspectives of THz radiation sources based on the FEL. The principles of the low gain THz FEL oscillator, the SASE THz FEL amplifier and the supperradiant THz FEL are reviewed briefly, and the key technologies of THz FEL, such as injector, accelerator, undulator and optical cavity, are discussed, respectively. The current status of and future prospects for THz radiation sources based on the FEL are emphasized in this paper. Recent research and development have shown bright future in free-electron laser (FEL) THz radiation sources. The potential applications can be carried out in the field of imaging, material research, biology medicine, communication, diagnostics and many others.

Design study of compact cyclotron magnet in virtual prototyping environment

An intelligent magnet design, modelling and optimization method with the aid of beam dynamics analysis and three dimensional magnetic field calculation is introduced. The whole procedure is implemented in an integrated virtual prototyping environment built with Python language. As a case study, the main magnet design of a 16 MeV H- compact cyclotron is illustrated. Both the field isochronism and transversal focusing of the beam can be fulfilled, and the mechanical analysis is performed to validate the feasibility in mechanics.

LabVIEW AND MATLAB-based virtual control system for virtual prototyping of cyclotron

A virtual control system designed to control and monitor the process of a cyclotron virtual prototyping is presented in this paper. Based on the feature of cyclotron, a distributed control structure is proposed according to the knowledge of software engineering. LabVIEW is employed to develop human machine interface (HMI), sequential control, safety interlock, and MATLAB is used to implement analysis and simulation. Dynamic data exchange (DDE) supported by Win32 platform SDK is adopted to process data exchanging by a server/client mode. Any additional functions can be extended easily in this system in future.

Applying virtual prototyping to the innovative design of low energy accelerators

Based on the accelerator theory and virtual prototyping technique, an accelerator virtual prototyping system (AVPS) is formulated, implemented for the innovative design of low energy accelerators. The framework of AVPS takes into account the needs of manufacture, assembly/disassembly, operation, and maintenance in a virtual environment during the design phase. In order to guarantee the reliability of AVPS, Augmented Reality (AR) technique is used to integrate the virtual environment and experimental subsystem. Common Object Request Broker Architecture (CORBA) middleware for distributed, object-oriented applications is used to develop and implement the framework. The main components of AVPS include AR subsystem, distributed computing environment and data warehouse.

A framework design for a cyclotron virtual control platform based on object-oriented methodology

This paper introduces a new software solution for cyclotron control system design and validation that named Cyclotron Virtual Control Platform (CVCP) and gives implementations in framework design. This software platform has abilities to simulate the processes and conditions in normal cyclotrons such as start up and shut down, routine operations, beam current regulation with combination of built-in component models and sequential control logic. A Human Machine Interface (HMI) with Supervisory Control and Data Acquisition (SCADA) functions and 3D interaction features provides a good operation channel. And an intelligent fault diagnosis module that can both generate errors and give solutions will be integrated into the platform in further plans. We use Object-Oriented technology to build this complex system and represent it in Unified Modeling Language (UML). It is easy to extend the functions in this open system. The platform is applied to Cyclotron Virtual Prototyping technology.

A High Precision Particle-Moving Algorithm for Particle-in-Cell Simulation of Plasma

A new particle-moving algorithm for particle-in-cell simulation of plasma is developed based on the linear multistep method. The conventional and the new algorithms are investigated by numerical experiments, which are conducted in three typical fashions of the electron motions in electromagnetic fields, namely, cyclotron in homogeneous magnetic field, drift in E × B field, and motions in inhomogeneous magnetic field. The new algorithm not only improves the accuracy, but also relaxes the time step condition for the simulation, thus increasing the computation efficiency.

Fast and Accurate Magnetic Field Shimming for A Compact Cyclotron

Isochronous magnetic field shimming was performed for a 10 MeV H- cyclotron used for PET purpose. The shimming is de-composed into a sequence of separate small patches, and the isochronous field correction is approximated with the effects of a set of standard patches on the assumption that the effect of each small patch is proportional to its surface. The mapped magnetic field data is used to calibrate the B-H curve used for 3D TOSCA calculation to obtain a very precise FEM estimator with relative error less than 0.1%, thus the effect due to each standard patch is estimated precisely. Correction of the pole is found by solving a system of equations using the least square scheme. The shimming was performed and the measurement of the magnetic field was found in good agreement with the prediction, with error less than 2Gs; and the history RF phase slip within ± 4° was achieved. The method proved to be of very high accuracy and thus no need of iteration.

A Novel Design of Insulated Core Transformer High Voltage Power Supply

Insulated core transformer (ICT) high voltage power supply is an ideal model for industrial radiation accelerator at energy below 1MeV. Compared to the traditional scheme, a novel ICT high voltage power supply was put forward. Conventional silicon steel sheets were replaced with manganese zinc ferrites, raising working frequency from 50Hz to thousand hertz. Magnetic structure was changed from three-phase structure to four-phase structure. Accordingly, excitation voltage was changed from three-phase sinusoidal wave to square wave. Polyimide was chosen as insulation material instead of teflon or mica. A prototype of 400kV/50mA was designed, simulated and verified with the aid of finite element analysis software. To optimize the voltage distribution, corresponding flux compensation methods were raised to solve the problem of flux leakages.

The Study of the Optical Cavity for a Compact Terahertz Source Based on Free Electron Lasers

In this paper some key technologies of an optical cavity for a compact Terahertz(THz) Source Based on Free Electron Lasers(FEL) were studied. Firstly, the theory of THz radiation was analyzed by some calculations. The high quality electronic bunch beams with energy 5.6-9.9MeV can produce THz radiation with frequency 1-10THz. Secondly, the configuration of the optical cavity was calculated and studied, and some conditions were discussed in order to obtain a single resonance mode. Thirdly, The loss caused by the diffraction and the coupling aperture was calculated. Finally, an idea of designing an optical cavity and some important data were given.

Construction Status of Main Magnet for CYCIAE-100

A new radioactive ion beam project, Beijing Radioactive Ion-beam Facility (BRIF), has been started at CIAE since 2004 . In this project, a 100 MeV H- cyclotron, CYCIAE-100, is selected as the driving accelerator providing 75-100 MeV, 200-500 proton beam. CYCIAE-100 is consisting of the main magnet, RF system, ion source and injection system, dual beam extraction system, etc. The progress of this machine had been reported elsewhere . The main magnet is the most critical part and had been numerically simulated and delicately designed . The techniques for main magnet construction are investigated in detail . The construction of this compact style, 450 ton cyclotron magnet has been started since 2007. The imperfection control of the large scale casting steel, the deformation and fabrication tolerance, etc., have all posed a challenge to the capacity limitation of cyclotron lab at CIAE for magnet design, mapping and shimming, and of industry for steel production/machining in the world. The design highlight of the magnet will be briefly introduced and the emphasis in this paper will be given to the construction progress.