COTS Analog Prototype for LHCb's Calorimeter Upgrade

Abstract

The objective of this thesis is to present a proposal for the analogue signal processing chain needed for the LHCb calorimeter upgrade improving the design used originally.

The design contains several novelties: the system was designed with low noise in mind from the beginning, it is made to have good immunity to interferences stressing the fact that the board will be shared with large digital circuits, differential operational amplifiers are used in a non-standard way as a mean to obtain opposite polarity signals for the signal treatment and a way to increase the available signal in the front end electronics is proposed.

The thesis starts with a brief introduction to the detector and its environment. This is followed by an explanation of the use of shapers in high energy physics detectors and the constraints that the shaper must address in the LHCb calorimeter.

This leads to a chapter where the circuit design is explained starting from the analysis of the original circuit and its flaws. Once the original circuit and the restrictions are understood the different parts of the circuit are explained showing the key points of each one. The explanation always starts as theoretic calculations, followed by practical problems and its solution until a fine tuning is obtained.

Once the functional circuit is designed a chapter of electromagnetic considerations explains all the measures taken during the PCB design to prevent noise from leaking into the system.

Stability and noise issues are discussed in depth in the last theoretic chapters. After that the different measurement procedures and results are exposed followed by the conclusions.

La presente tesis doctoral versa sobre una propuesta para la actualización del sistema de tratamiento analógico de la señal procedente del calorímetro de LHCb.

El esquema propuesto incluye diversos elementos diferenciadores: ha sido diseñado específicamente para minimizar el ruido electrónico y coexistir en la misma placa de circuito impreso que la lógica digital minimizando la contaminación por el ruido que esta genera; utiliza amplificadores operacionales de un modo no convencional para conseguir señales de polaridades opuestas con gran precisión y propone un método para maximizar la carga entregada a la electrónica en el caso particular del calorímetro de LHCb.

El documento arranca con una introducción al experimento, los denominados shapers y su utilización el física de altas energías para luego describir en detalle las fases de diseño, prototipado y medición de resultados haciendo especial hincapié en la compatibilidad electromagnética, la integridad de señal y la minimización del ruido.