PIN-diode diagnostics of pulsed electron beam for high repetition rate mode

Abstract

Abstract. This work describes the operating principle and test results of the diagnostics for measuring the pulsed electron beam parameters under repetitive operation mode. The diagnostics is based on a PIN-diode, which is used as a bremsstrahlung detector. The signal from a PIN-diode was converted to a pseudo constant voltage signal which can be measured by a conventional voltmeter. Then the signal acquired by the voltmeter was compared with a reference signal indicating the normal operating regime of the accelerator, thus information about the shot-to-shot reproducibility of the electron beam parameters was given. The system was developed and tested for the ASTRA-M accelerator with the following operating parameters: 470 kV accelerating voltage, 120 ns beam duration and up to 50 pulses per second repetition rate. IntroductionThe field of electron beam applications is growing up rapidly [1,2]. For applications, which require a high level of an average electron beam power [2,3], the continuous and the linear electron accelerators are usually used. The pulsed accelerators are used for relatively lower average power applications and, meanwhile, allow for a compact facility size [4,5]. As a rule, for pulsed systems, a higher pulse repetition rate means a higher productivity. The ASTRA-M pulsed electron accelerator [6] uses the 40 pulses per second (pps) continuous operation mode for the purpose of wastewater treatment, as well as single pulses for research applications [7 -9]. The ASTRA-M accelerator generates electron beams with the kinetic energy of electrons of up to 470 keV and the pulse width of 120 ns at half maximum [6]. During the use of accelerator for some applications, the electron beam parameters cannot be measured directly, thus, the accelerating voltage and the total diode current are used for controlling the electron beam parameters. However, such indirect information about the beam parameters is not enough to ensure an accurate operation of the accelerator, especially when the electron beam is ejected into the atmosphere. An alternative approach to control the electron beam parameters is measuring the bremsstrahlung radiation, which occurs when the electron beam interacts with a matter. The bremsstrahlung intensity for the same measurement geometry depends on the electron beam parameters. One of the most convenient ways to measure the bremsstrahlung with a high time resolution is to use PIN-diodes [10,11]. However, when a great number of pulses, e.g. 10

Optimization of Transmission X-ray Target for Intense Pulsed Electron Beam Accelerators

“…It is verified by experimental and numerical means that under the irradiation of IPEBs, a temperature rise of several tens of K [26] can be induced in the target and the consequent thermal stress is an important cause of target damage. The situation of conversion layer damage can be monitored by online monitoring, such as with a semiconductor X-ray detector [46], and in tests with a titanium electron window, a window with a thickness within 100 µm can well secure the vacuum in the vacuum chamber [23], ensuring that, with the dual-layer target, the working vacuum can be kept even after conversion layer damage. However, frequent maintenance of the window system should undoubtedly be avoided in practical applications.…”