基于I/Q解调原理的校准方法及实验

同相/正交(In-phase/Quadrature,I/Q)解调技术广泛应用于射频信号相位控制系统。I/Q器件存在固有误差,如直流偏置、幅度不平衡、相位不平衡和电路长度不等。这些误差会导致输出的I/Q轨迹呈椭圆,相位为非线性,影响相位鉴别的精度。为减小误差带来的影响,提出一种基于I/Q解调技术的软件校准方法,并将此方法在自制基于贴片式芯片集成的I/Q解调印刷电路板上验证。测试表明,输出的I/Q信号经校准后相位误差≤±0.15°,幅度稳定度≤±1%,通道延时≤10 ns。此板卡设计和校准方法已在新升级的上海光源储存环高频束流丢失分析系统中的射频信号前端预处理中使用,各项指标均满足束流丢失分析系统中射频信号监测的要求。     

一种基于三项误差模型的I／Q解调器校准方法

I/Q解调器的误差决定了PAD的相位测量精度.本文在I/Q解调器以往的两项误差模型基础上引入三项误差模型,并给出了相应的误差校准方法.实验结果表明,这种校准方法是合理有效的.在BEPCⅡ工作频率2856 MHz上,经校准的I/Q解调器的误差范围减小为-1.8 °～O.5 °,且360 °范围内任意相位值的测量误差均得到了抑制.     

高精度中频数字鉴相器在FPGA上的实现

介绍了一种高精度中频数字鉴相器的鉴相原理,以及在设计过程中以数字滤波器为主的参数选择方法,并且将其在FPGA上硬件实现。该鉴相器采用数字I/Q技术,鉴相精度达到0.029°,利用该高精度中频数字鉴相器对3.71875 MHz中频信号进行鉴相,实际鉴相结果为:绝对相位鉴相结果好于0.05°,均方根值为0.0076°;相对相位鉴相结果好于0.1°,均方根值为0.0287°。     

γ射线旋转调制器成像系统的研制

可对硬X射线、γ射线等成像的旋转调制器(Rotating Modulator,RM)成像技术是一种探测效率高、能量范围宽、能量分辨能力高的技术,可满足核辐射监测中对高性能γ射线成像系统的需求。为此,研制了一台基于RM技术的γ射线成像系统样机。该样机主要包括一个由8条铅条组成的旋转准直器、7个NaI(Tl)探测器、步进电机和相应的读出及控制电路。样机视场角±14.6°,角度分辨率2°,在662 keV处能量分辨率为7%,对662 keVγ射线的探测效率达到22.2%。     

ADS注入器Ⅰ束流相位及能量测量系统设计

针对加速器驱动次临界系统(Accelerator Driven Sub-critical System,ADS)注入器Ⅰ束流调试要求,需要精确测量束流的相位和能量。本文研究束流的相位和能量高精度测量方法,设计了基于快速电流变压器(Fast Current Transformer,FCT)信号的相位及能量测量系统。该系统包括FCT探头、前端电子学、数据采集和处理三个部分,通过正交采样的方式实现束流的相位测量,然后利用飞行时间法实现束流能量的测量。测试结果表明,该系统在实验室测试相位分辨率为±0.8°,在线测试相位分辨率为±2°,满足直线加速器的设计要求。     

基于FPGA的CSR高频控制系统相位求解模块设计

CSR高频控制系统需要对高频正弦波激励信号的幅度、相位、频率进行稳定控制。相位arctan(Q/I)求解是必不可少的模块。论述了一种新的基于FPGA平台和对称查找表法(SBTM)的求解相位arctan(Q/I)的方法,做了详细的理论分析,给出了具体实现的代码和结果。该模块精度高,消耗资源少,可直接应用于CSR高频控制系统。     

SSRF定时系统的温漂补偿系统设计

上海同步辐射装置(SSRF)的定时信号通过光纤由事件发生器EVG发送到事件接收器EVR,为各个分系统和设备提供精确时序信号,但光纤因SSRF复杂的局部环境而产生温度变化,从而引起EVR的输出信号与高频信号的相位漂移.因此需设计-套温漂补偿系统来补偿这种因光纤的温度变化而产生的相位漂移,本文详细阐述了温漂补偿系统的硬件架构及相位测量算法,最后给出了温漂补偿系统的测试结果.     

BEPCⅡ电子环损失参数检测系统设计

采用数字化相位检测技术,设计了一套高精度相位检测系统,将其应用于BEPCⅡ电子环束流相位和腔相位的检测,测量了BEPCⅡ电子环损失参数。测试结果表明:该系统的分辨率为±0.001°。该系统实现了实验数据的快速存储和检索,获取、处理相关数据更加高效、快捷。     

数字I/Q射频鉴相器的研制

详细介绍了一种用于直线加速器的数字化I/Q射频鉴相器.该鉴相器使用双平衡混频器作为相位探测器,由于采用了商业化的PXI模块,控制和数据获取系统都是基于PXI总线;软件采用曲线拟合算法.实验室的测试表明该系统具有分辨率高,重复性好,可靠性强等特点.     

CR-39测量中子能谱响应函数的计算

计算了在一定的化学和电化学蚀刻条件下,由聚乙稀、铅(金)和CR-39组成的叠层探测器的响应函数(1～20 MeV)。计算结果表明,叠层探测器的响应函数分布近似为高斯分布,由铅组成的探测器的响应函数的半高宽比由金组成的探测器的响应函数的半高宽窄,由前者组成的探测器测量中子能谱分辨率高于后者。     

The spectrum analysis of RMP coils with multiple connection modes and the design of high field side coils on J-TEXT

The phase difference Δξ between locked islands (2/1 and 3/1) has been found to influence the heat transport on the thermal quench during disruptions by numerical modeling [Hu Q et al 2019 Nucl. Fusion 59, 016005]. To verify this experimentally, a set of resonant magnetic perturbation (RMP) coils is required to excite coupled magnetic islands with different Δξ. The spectrum analysis shows that the current RMP coils on J-TEXT can only produce sufficient 2/1 and 3/1 RMP fields with a limited phase difference of Δξ∈[−75°, 75°]. In order to broaden the adjustable range of Δξ, a set of coils on the high field side (HFS) is proposed to generate 2/1 and 3/1 RMP fields with Δξ = 180°. As a result, RMPs with adjustable Δξ∈[−180°, 180°] and sufficient amplitudes could be achieved by applying the HFS coils and the low field side (LFS) coils. This work provides a feasible solution for flexible adjustment of the phase difference between m and m + 1 RMP, which might facilitate the study of major disruptions and their control.     

用于回旋加速器射频低电平系统的通用DSP固件程序设计

针对回旋加速器射频系统幅度、相位、启动逻辑、联锁保护、在线参数修改等控制需求,编写了一种基于有限状态机的通用DSP固件程序。该固件程序将射频系统启动过程划分为5个状态:封锁RF信号、搜索腔体谐振点、提升射频功率、匹配相位、幅相闭环控制。该固件程序通过串口与本地上位机和远程控制机进行实时通信,支持在线修改射频系统启动参数;采用异步事件驱动方式,实现对打火和反射功率过大等异常情况快速响应。该固件程序成功应用于CYCIAE-100回旋加速器射频低电平系统中,在CYCIAE-100回旋加速器调束过程中,完成了射频系统的启动控制和设备保护,满足加速器控制系统的需求。     

SHINE腔式BPM系统射频信号调理前端研制

基于低温超导直线加速器的上海硬X射线自由电子激光装置（SHINE）需1个分辨率可达200 nm的束流位置测量系统,以实现电子束与光子束在波荡器中的紧密相互作用和能量交换。现已研制的束流位置测量系统不能完全满足上述要求,为此,基于对关键技术指标的分配,设计研制了一个由C波段腔式探头、低噪声系数的单路下变频至低中频的射频信号调理前端以及专用数字信号束流位置处理器构成的CBPM系统样机。而作为连接腔式探头和数字信号采集电子学之间的桥梁,射频信号调理前端（radio frequency front end, RF前端）的结构和性能也直接决定了CBPM系统的性能。本文从SHINE对CBPM系统的整体需求为出发点,分析了系统对射频信号调理前端的指标分配,提出了一种放大器开关切换型RF前端的方案设计,并成功搭建了1套可模拟束流条件的离线全锁相采样测试平台。此外,在上海软X射线自由电子激光装置（SXFEL）中搭建了测试平台并完成了射频信号调理前端的带束性能评估,束流实验结果表明,在束团电荷量为100 pC、系统动态范围在±100 μm的条件下,采用腔式探头射频信号一分二的评估方法,位置分辨率可达71 nm,优于设计指标需求。     

Commissioning of 3.7 GHz LHCD system on ADITYA tokamak and some initial results

To drive plasma current non-inductively, a lower hybrid current drive (LHCD) system has been designed, fabricated and successfully installed on ADITYA tokamak. The system is designed to launch 120 kW of RF power, at a frequency of 3.7 GHz. The system mainly consists of a high power CW klystron source, a long waveguide transmission line of about 100 m length, a UHV compatible modular waveguide line of about 2.65 m, and a conventional grill type antenna. Independent phase shifters, one each in the eight lines, are used to adjust the antenna phasing and also provides the flexibility to launch a composite spectrum. The antenna is designed to launch lower hybrid waves (LHW) with parallel refractive index (N_||), in the range, 1 < N_|| < 4.5, by appropriately phasing the antenna. Antenna is positioned in the shadow of the poloidal limiter and is provided with 100 mm radial movement to achieve optimum coupling conditions.The complete system development includes design, fabrication and testing of number of waveguide components, modular waveguide lines and their integration. Different cost effective fabrication techniques are adopted to achieve good RF performance. Special attention is paid on the flanged joint seals in the long transmission line to minimize the RF losses. The entire LHCD system is calibrated, especially, in terms of phase, insertion loss and return loss measurements.After the successful integration of the system on ADITYA tokamak, some initial experiments have been carried out to assess the system commissioning and its performance. The experiments were done with a plasma (hydrogen) density of 2-5 × 10¹² cm⁻³ at a toroidal magnetic field of 0.8 T with 10-25 kA of plasma current. Initial results indicate that, good coupling is achieved in the presence of proper edge density. Measurements obtained from second harmonic electron cyclotron emission (ECE) and hard X-ray diagnostics suggest generation of suprathermal electrons in the presence of LH pulse. Plasma current pulse elongation with LH power is observed but needs further investigation to derive conclusions.This paper presents the design, fabrication, testing and integration of the waveguide lines, waveguide components and UHV compatible modular transmission lines of the LHCD system on ADITYA tokamak and discusses some of the initial results.     

EAST ion cyclotron resonance heating system for long pulse operation

Radio frequency (RF) power in the ion cyclotron range of frequencies (ICRF) is one of the primary auxiliary heating techniques for Experimental Advanced Superconducting Tokamak (EAST). The ICRF system for EAST has been developed to support long-pulse high-β advanced tokamak fusion physics experiments. The ICRF system is capable of delivering 12 MW 1000-s RF power to the plasma through two antennas. The phasing between current straps of the antennas can be adjusted to optimize the RF power spectrum. The main technical features of the ICRF system are described. Each of the 8 ICRF transmitters has been successfully tested to 1.5 MW for a wide range of frequency (25–70 MHz) on a dummy load. Part of the ICRF system was in operation during the EAST 2012 spring experimental campaign and a maximum power of 800 kW (at 27 MHz) lasting for 30 s has been coupled for long pulse H mode operation.     

Design and implementation of power and phase feedback control system for ICRH on EAST

Ion cyclotron wave resonance heating(ICRH) is one of the most important auxiliary methods to heat plasma in the Experimental Advanced Superconducting Tokamak(EAST). Several megawatts of power is transmitted through separate coaxial lines and coupled with the plasma through arrays of loop antennas. The parameters of the ICRH system, including the injected power and phasing between antenna straps, are critical to the coupling efficiency of the power as well as the resulting impact on the heating efficiency. In this paper, we present a system for feedback control of the phase between the current straps and the ICRH power on EAST. The feedback control system was tested using both a matched dummy load and a plasma load, and it successfully maintained stable operation in the 2016 EAST campaign. Good control of the injected power and wave phases was achieved during edgelocalized mode operation.     

用于回旋加速器低电平系统的通用软硬件系统设计与实现

针对回旋加速器射频系统幅度、相位、频率、自动启动逻辑、联锁保护、在线参数修改等控制需求，设计了一种用于回旋加速器低电平系统的软硬件系统。该系统的硬件基于ZYNQ系列FPGA和高速ADC及DAC。采用数字下变频技术实现了幅度、相位和调谐控制；采用数字电路实现了腔体打火的快速检测。幅度控制精度为0.015%，相位控制精度为0.04°。该系统充分发挥了数字低电平系统的全可编程优势，通过上位机修改参数即可适用于多种回旋加速器。     

Dynamics of nuclear spin-1/2 system in a strong bichromatic RF-field

Based on calculating the influence of RF-field with various physical parameters on the dynamics of the spin 1/2 system,it was found that the spin state could be changed up and down by choosing appropriate RF pulses,and the coherent control of the RF pulses could substantially modify the behavior of spin dynamics:quicker change of two states could be produced even for small pulse duration.In addition,the oscillatory structures around the resonant frequency and the propagation features of the pulses depend on the relative phase of the biehromatie RF pulses.     

200MeV电子直线加速器能量稳定系统

利用计算机对束流能谱图像进行了处理 ,并自动调整加速场相位 ,建立了 2 0 0MeV电子直线加速器能量稳定系统 ,该系统对束流能量在± 4MeV范围内的漂移进行自动补偿 ,使能量稳定在± 0 .6 %左右