Design and Implementation of a High-Speed Readout and Control System for a Digital Tracking Calorimeter for proton CT

Particle therapy, a non-invasive technique for treating cancer using protons and light ions, has become more and more common. For example, a particle treatment facility is currently being built, in Bergen, Norway. Proton beams deposit a large fraction of their energy at the end of their paths, i.e., the delivered dose can be focused on the tumor, sparing nearby tissue with a low entry and almost no exit dose. A novel imaging modality using protons promises to overcome some limitations of particle therapy and allowing to fully exploit its potential. Being able to position the so-called Bragg peak accurately inside the tumor is a major advantage of charged particles, but incomplete knowledge about a crucial tissue property, the stopping power, limits its precision. A proton CT scanner provides direct information about the stopping power. It has the potential to reduce range uncertainties significantly, but no proton CT system has yet been shown to be suitable for clinical use. The aim of the Bergen proton CT project is to design and build a proton CT scanner that overcomes most of the critical limitations of the currently existing prototypes and which can be operated in clinical settings. A proton CT prototype, the Digital Tracking Calorimeter, is being developed as a range telescope consisting of high-granularity pixel sensors. The prototype is a combined position-sensitive detector and residual energy-range detector which will allow a substantial rate of protons, speeding up the imaging process. The detector is single-sided, meaning that it employs information from the beam delivery system to omit tracker layers in front of the phantom. The detector operates by tracking the charged particles traversing through the detector material behind the phantom. The proton CT prototype will be used to determine the feasibility of using proton CT to increase the dose planning accuracy for particle treatment of cancer cells. The detector is designed as a telescope of 43 layers of sensors, where the two front layers act as the position-sensitive detector providing an accurate vector of each incoming particle. The remaining layers are used to measure the residual energy of each particle by observing in which layer they stop and by using the cluster size in each layer. The Digital Tracking Calorimeter employs the ALPIDE sensor, a monolithic active pixel sensor, each utilizing a 1.2Gb/s data link. Each layer of 18×27 cm consists of 108 ALPIDE sensors, roughly corresponding to the width and height of the head of a grown person. The sensors are connected to intermediary transition boards that route the data and control links to dedicated readout electronics and supply the sensors with power. The readout unit is the main component of both the data acquisition and the detector control system. The power control unit controls the power supply and monitors the current usage of the sensors. Both of these devices are mainly implemented in FPGAs. The main purpose of this work has been to explore and implement possible design solutions for the proton CT electronics, including the front-end, as well as the readout electronics architecture. The resulting architecture is modular, allowing the further scale-up of the system in the future. A major obstacle to the design is the high amount of sensors and the corresponding high-speed data links. Thus, a large emphasis has been on the signal integrity of the front-end electronics and a dynamic phase alignment sampling method of the readout electronics firmware. The readout FPGA employs regular I/O pins for the high-speed data interface, instead of high-speed transceiver pins, which significantly reduces the magnitude of the data acquisition system. A consistent design approach with detailed and systematic verification of the FPGA firmware modules, along with a continuous integration build system, has resulted in a stable and highly adaptive system. Significant effort has been put into the testing of the various system components. This also includes the design and implementation of a set of production test tools for use during the manufacturing of the detector front-end.Doktorgradsavhandlin

Wide Bandgap Based Devices: Design, Fabrication and Applications, Volume II

Wide bandgap (WBG) semiconductors are becoming a key enabling technology for several strategic fields, including power electronics, illumination, and sensors. This reprint collects the 23 papers covering the full spectrum of the above applications and providing contributions from the on-going research at different levels, from materials to devices and from circuits to systems

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Personal area networks (PAN) : near-field intra-body communication

Thesis (M.S.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1995.Includes bibliographical references (leaves 80-81).by Thomas Guthrie Zimmerman.M.S

SOLID-SHELL FINITE ELEMENT MODELS FOR EXPLICIT SIMULATIONS OF CRACK PROPAGATION IN THIN STRUCTURES

Crack propagation in thin shell structures due to cutting is conveniently simulated using explicit finite element approaches, in view of the high nonlinearity of the problem. Solidshell elements are usually preferred for the discretization in the presence of complex material behavior and degradation phenomena such as delamination, since they allow for a correct representation of the thickness geometry. However, in solid-shell elements the small thickness leads to a very high maximum eigenfrequency, which imply very small stable time-steps. A new selective mass scaling technique is proposed to increase the time-step size without affecting accuracy. New ”directional” cohesive interface elements are used in conjunction with selective mass scaling to account for the interaction with a sharp blade in cutting processes of thin ductile shells

NASA Tech Briefs, May 1997

Topics covered include: Advanced Composites, Plastics and Metals; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Reports

NASA Tech Briefs, November/December 1987

Topics include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Fabrication Technology; Machinery; Mathematics and Information Sciences; Life Sciences