Design of a Phase Locked Loop for a Low Power Transceiver

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Design and Development of a Digital Radio Frequency Control System for Linear Accelerators

The new control system for Radio Frequency (RF) structures at Legnaro National Laboratories (LNL) is presented in this document. LNL is one of the four national laboratories of the National Institute for Nucler Physics (INFN) and it is devoted to basic research in nuclear physics and nuclear-astrophysics, together with applications of nuclear technologies. The subject of this Ph.D. thesis is indeed the development of a fully digital RF feedback system, focusing on the validation of the RF controller, its programming and its integration in the particle accelerator control system. The RF controller interacts directly with the cavities and it works in a real-time closed loop. It is a set of analog and digital electronics which provides phase, amplitude and frequency corrections to stabilize the RF field in presence of disturbances and vibrations due to other subsystems of the accelerator. The control algorithm is implemented via a programmable device as an FPGA. This increases dramatically the flexibility and the programmability of the controller. The digital board of the RF controller can work in a wide range of the RF spectrum. It is a versatile tool, easy to adapt to 40/80/160/352 MHz resonators, thus spanning all types of cavities of the final SPES configuration. At LNL, it may be used to control RF cavities like bunchers to pulse the beam, superconducting cavities to accelerate the beam and RF quadrupoles (RFQ) to both accelerate and focus the beam. Most of them work in superconducting condition, while the other ones in normal condition. The controlling and the monitoring of the RF controller is done by the particle accelerator control system based on EPICS (Experimental Physics and Industrial Control System). It is a widely adopted software framework for control systems. EPICS is a set of tools, libraries and applications developed collaboratively and used worldwide to create distributed soft real-time control systems for scientific instruments such as particle accelerators. Beam transport was carried out with the 8 cavities working in superconducting mode with the new instruments. The controller kept locked the cavities for few days. In this time the controller has proven to be more stable and reliable than the precedent system. The first chapter of the document introduces the SPES and ALPI facility and the RF subsystem to a certain level of details: RF acceleration concepts and Low Level RF (LLRF) control for an optimum energy gain of the particle beam. In order to better understand the issues faced during the design of the control system it is useful to derive mathematical models of the RF cavities. This is the subject of the second chapter. In the third chapter the disturbance sources of the accelerating field are listed, besides clarifying the stability requirements, the frequency tuning of the cavities and their driving modes. Furthermore, the choice of the frequency sampling is outlined. The fourth chapter introduces the controller in detail. The boards functionalities are highlighted, the fundamental elements of the boards are described as well as the communication between components and boards. The fifth, sixth and seventh chapters describe the main contribution of this Ph.D. thesis. The firmware development for the Field Programmable Field Array, that is the heart of the RF controller, is covered in chapter five, emphasizing the module for the communication with the accelerator control system and the module that implements the control algorithms. The sixth chapter gives an overview of the EPICS framework, focusing on the driver support, the integration of the RF controller with the EPICS based control system is further expanded while in the last section the RF cavity tuning is explained. The seventh chapter is split in two sections. The first section lists the tests performed in order to qualify the boards of the RF controller. The second section analyzes some key parameters acquired during a successful beam test in real working conditions, where the performance of the new controller has been evaluated. Finally, a concluding chapter summarizes the results obtained so far and outlines improvements and future upgrades that can implement new functionalities in the Radio Frequency control system

Towards the First Beams from the ADIGE Injector for the SPES Project

International audienceThe ADIGE (Acceleratore Di Ioni a Grande carica Esotici) injector of the SPES (Selective Production of Exotic Species) project is now in an advanced phase of installation. Its main components have been designed following particular needs of the project: first, an Electron Cyclotron Resonance (ECR)-based Charge Breeder (SPES-CB), to boost the charge states of the radioactive ions produced at SPES and allow their post-acceleration. Then, a stable 1+ source and a complete electrostatic beam line to characterize the SPES-CB. Finally, a unique Medium Resolution Mass Spectrometer (MRMS, R=1/1000), mounted on a high voltage platform downstream the SPES-CB, to clean the radioactive beam from the contaminants induced by the breeding stage. This contribution describes the status of the injector, in particular the installation of the platform housing the MRMS, the access and safety system adopted and the first beams to be extracted from the stable 1+ source