Doctoral thesis of Isaías Martín on the design and application of ADEX in superconducting cavities of a proton linear accelerator

In News — July 12 2018

The work of the doctoral thesis presented by Isaías Martín, Deputy Technical Director of ADEX, on July 10 at the National University of Distance Education (UNED), has been carried out within the framework of the development of the MYRRHA transmutation reactor, which will have the ability to incinerate nuclear waste. The research effort has focused on the development of an Optimized Adaptive Control System (SCOA) that provides high reliability to the superconducting cavities (SC) of the proton accelerator that drives the operation of the MYRRHA. The thesis has combined two fields at the forefront of research: that of particle acceleration and that of advanced control methodologies.

The SCOA developed is based on the Adaptive Predictive Expert (ADEX) control methodology and its operation responds to an Optimized Control Strategy (ECO) that constitutes one of the main original contributions of the thesis. The design of the ECO combines ADEX controllers, notch and Chebyshev filters and anticipator blocks, to attenuate the excitation of resonant modes that could cause the ADEX controller’s own actions, and to minimize the effect of microphonic disturbances and those caused by changes in beam intensity.

The performance of the SCOA was analyzed comparatively with the most advanced previous solutions in a simulation of the 704.4 MHz elliptical cavity developed by the Centre Nationale de la Recherche Scientifique (CNRS) of France. The favorable evaluation led to the application in an elliptical cavity operated at cryogenic temperature, which proved that the SCOA achieves a considerable reduction of the oscillations of the resonance frequency of the cavity around its setpoint, in comparison with the previous advanced systems based on PID.

This implies that the operation of the SCOA minimizes the energy consumption of the cavity, it can modify its behavior under the effect of unexpected disturbances, return appropriate control actions for the new circumstances, maintain the resonance frequency within its operational limits and the cavity under control. This same type of unexpected disturbances caused the advanced PID-based systems to lose control of the cavity.

These results have highlighted that the SCOA ADEX considerably increases the operational reliability of the cavities against changes in their dynamics and uncertain operating scenarios with unforeseen disturbances and, therefore, the reliability of the operation of the proton accelerator.

The committee of this thesis with international connotation, was chaired by professor José Rodellar of the Polytechnic University of Catalonia (second from the right of the photograph), professor Javier Sanz of the UNED acted as secretary (first by the left) and as member, Senior Researcher Frédéric Bouly of the Laboratoire de Physique Subatomique et Cosmologique de Grenoble, of the CNRS of France (third by the left). The photo also includes the director of the thesis, Professor José Carpio (second from the left), the co-director, Professor Juan Manuel Martín (first from the right) and the doctoral student.