High-repeatable data acquisition systems for pulsed power converts in particle accelerator structures

Abstract

In this Ph.D. thesis, the issues related to the metrological characterization of high-performance pulsed power converters are addressed. Initially, a background and a state of the art on the measurement systems needed to correctly operate a high-performance power converter are presented. As a matter of fact, power converters usually exploits digital control loops to enhance their performance. In this context the final performance of a power converter has to be validated by a reference instrument with higher metrological characteristics. In addition, an on-line measurement systemis also needed to digitize the quantity to be controlled with high accuracy. Then, in industrial applications of power converters metrology, specifications are given in terms of Worst-Case Uncertainty (WCU). Therefore, an analytical model for predicting the Worst-Case Uncertainty (WCU) of a measurement system is discussed and detailed for an instrument affected by Gaussian noise. Furthermore, the study and the design of a Reference Acquisition System for characterizing the high-power pulses of the klystronmodulators of the Compact LInear Collider (CLIC), a new linear accelerator under study at CERN, is presented. Finally, the design of an On-line Acquisition Systemfor controlling the CLIC power converter, is presented. The Thesis continues with the numerical results obtained in simulation for the three main topics (Worst-Case Uncertainty, Reference Acquisition System, On-line Acquisition System) to demonstrate the effectiveness of the proposals. Finally, the experimental results of a case study in the framework of the above-mentioned CLIC accelerator are reported and compared with the simulations in order to obtain the final validation of the proposals. In particular, CLIC main requirements for the measurement systems mostly concern their level of repeatability which was proven to be only affected by the instrumental noise under certain assumptions. Thus, the two systems were designed to be ultra-low noise solutions and, in turn, they are demonstrated to be repeatable in the order of few tens of parts per million (ppm).