Electron Accelerator Pulsed Electron Beam Measurement System Research And Design

Pulsed electron beam measurement system is the important part of the electron linearaccelerator. The main function of the accelerating tube system is to achieve the continuouson-line measurement of output pulsed electron beam unobstructed. Single pulsed electronbeam intensity and average of pulse beam is one of the key parameters of the running stateof a electron linear accelerator while adjustment and determine.Pulsed electron beam measurement system is comprised by electron beam sensors,low-noise broadband amplifier circuit and the gating variable gain amplifier circuit, dataacquisition and processing circuit, LED digital display and data communications interface.It can achieve pulsed electron beam measurement, display and data transmission with thehost computer.The key point of this thesis is whether the response speed of pulsed electron beammeasurement system, the accuracy of measurement, especially the stability ofmeasurement and anti-jamming capability can meet the practical application. Because it isdirectly related to the ability to estimate the running state of the high-energy electronlinear accelerator and to reflect the basic parameters of the electron beam processingquality correctly. In this thesis, the application of high-energy electron linear accelerator isour effective target. Start the research and design to make the multiple technology level ofelectron beam line measurement system reached practical level.The main research and discovery of this thesis:Structural optimization of pulsed electron beam sensors.Based on the fundamental theory of the electromagnetic induction, the connectionbetween the pulsed electron beam sensor output voltage u0and the pulsed electron beamas follows:u₀=i₂R_s=R_s/N i₁Equation shows that in the condition of the smaller resistance in the signal sampleswhile the change rate of measured current is high, the output voltage of the pulsed electronbeam sensor u0measured pulsed electron beam current i1proportional.Optimization of the pulsed electron beam sensors includes the selection of annularsecondary coil skeleton cross-sectional area of shape, the secondary coil skeleton materialand the secondary coil winding. Secondary winding skeleton using cross-sectional area ofthe circular ring; using high voltage insulation performance, as a the loss small,95magnetic secondary coil skeleton material; its not only has a good non-magneticquality, but also secondary coil the skeleton should adopt non-magnetic materials. And inwhich the number of non-magnetic materials, due to the characteristics of long service life,it become the prior material for secondary winding skeleton; selected a=60mm; b=10mm, Φ0.35copper wire wound on the skeleton uniformity error≤1%of thecoil （N=320）.（2） low noise broadband amplifier technologySince there is a more complex electromagnetic interference in the pulsed electronbeam measurement environment, and the form of pulses of the pulsed electron beam of thesensor output signal amplitude is small, and its apart from the measurement system, whichuses the impedance matching of the amplifier, the noise suppression capability andbroadband raise a high requirements. Proposed for the practical application needs avariable impedance matching circuit, low-noise broadband preamplifier and gain gatedamplifier circuit. And from the circuit structure, component selection, basic characteristics,we made a more detailed analysis. Among them, the gated amplifiers can work only in thepulsed electron beam sensor output signal Subsisting time, but is closed at other times, andthus, to some extent, can be suppressed interference from complex working environmentof the electromagnetic noise caused.（3） microcontroller-based data acquisition and processing technologyMicrocontroller and data communication interface’s selection should be based on theelectron linear accelerator machine to meet the principle of consistency, as the core tothe PIC16F877and ADM2483to constitute data acquisition measurement circuit. Thecircuit may be better to complete the detection of pulsed electron beam data, datacommunication with the host computer. Technical indicators in design:Single-pulse electron beam measurement range:20³00mA.The accuracy of measurement: better than±2%Band width≥300MHzEnvironmental Operating temperature:0to45°C, humidity≤85%（4） The experimental verificationTest validation work adopts two ways, laboratory validation and hands-onvalidation. Laboratory verification using a pulsed current through the sensor centerconductor of the pulsed electron beam to simulate the actual pulse electron beam, pulsecurrent variation range of20³00mA, and a pulse width of16μs. The measurement accuracy of±2%.To sum up, this paper based on electromagnetic theory, as the core ofmicroprocessors and optimized electronic beam sensor, to improve broadband low noiseamplifier circuit, anti-electromagnetic interference technology, completed the practicalelectron beam line measurement system’s intended research and design work. Prototypehas passed simulation test, and the data results in a high-energy electron acceleratorsapplication proved, the overall design of the system is feasible, reached a preliminarymeasurement accuracy and stability, and other technical indicators meet the designrequirements.