A superconducting bandpass delta-sigma modulator for direct analog-to-digital conversion of microwave radio

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 291-305).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Direct analog-to-digital conversion of multi-GHz radio frequency (RF) signals is the ultimate goal in software radio receiver design but remains a daunting challenge for any technology. This thesis examines the potential of superconducting technology for realizing RF analog-to-digital converters (ADCs) with improved performance. A bandpass delta-sigma (AE) modulator is an attractive architecture for digitizing narrowband signals with high linearity and a large signal-to-noise ratio (SNR). The design of a superconducting bandpass AE modulator presented here exploits several advantages of superconducting electronics: the high quality factor of resonators, the high sampling rates of comparators realized with Josephson junctions, natural quantization of voltage pulses, and high circuit sensitivity. Demonstration of a superconducting circuit operating at clock rates in the tens of GHz is often hindered by the difficulty of high speed interfacing with room-temperature test equipment. In this work, a test chip with integrated acquisition memory is used to simplify high speed testing in a cryogenic environment. The small size (256 bits) of the on-chip memory severely limits the frequency resolution of spectra based on standard fast Fourier transforms. Higher resolution spectra are obtained by "segmented correlation", a new method for testing ADCs. Two different techniques have been found for clocking the superconducting modulator at frequencies in the tens of GHz. In the first approach, an optical clocking technique was developed, in which picosecond laser pulses are delivered via optical fiber to an on-chip metal-semiconductor-metal (MSM) photodiode, whose output current pulses trigger the Josephson circuitry. In the second approach, the superconducting modulator is clocked by an on-chip Josephson oscillator.(cont.) These testing methods have been applied in the successful demonstration of a super-conducting bandpass AE modulator fabricated in a niobium integrated circuit process with 1 kA/cm2 critical current density for the Josephson junctions. At a 42.6 GHz sampling rate, the center frequency of the experimental modulator is 2.23 GHz, the measured SNR is 49 dB over a 20.8 MHz bandwidth, and a full-scale (FS) input is -17.4 dBm. At a 40.2 GHz sampling rate, the measured in-band noise is -57 dBFS over a 19.6 MHz bandwidth.by John Francis Bulzacchelli.Ph.D

Studies for the Commissioning of the CERN CMS Silicon Strip Tracker

In 2008 the Large Hadron Collider (LHC) at CERN will start producing proton-proton collisions of unprecedented energy. One of its main experiments is the Compact Muon Solenoid (CMS), a general purpose detector, optimized for the search of the Higgs boson and super symmetric particles. The discovery potential of the CMS detector relies on a high precision tracking system, made of a pixel detector and the largest silicon strip Tracker ever built. In order to operate successfully a device as complex as the CMS silicon strip Tracker, and to fully exploit its potential, the properties of the hardware need to be characterized as precisely as possible, and the reconstruction software needs to be commissioned with physics signals. A number of issues were identified and studied to commission the detector, some of which concern the entire Tracker, while some are specific to the Tracker Outer Barrel (TOB): - the time evolution of the signals in the readout electronics need to be precisely measured and correctly simulated, as it affects the expected occupancy and the data volume, critical issues in high-luminosity running; - the electronics coupling between neighbouring channels affects the cluster size and hence the hit resolution, the tracking precision, the occupancy and the data volume; - the mechanical structure of the Rods (the sub-assemblies of the TOB) is mostly made of carbon fiber elements; aluminum inserts glued to the carbon fi ber frame provide efficient cooling contacts between the silicon detectors and the thin cooling pipe, made of a copper-nickel alloy; the different thermal expansion coefficients of the various components induce stresses on the structure when this is cooled down to the operating temperature, possibly causing small deformations; a detailed characterization of the geometrical precision of the rods and of its possible evolution with temperature is a valuable input for track reconstruction in CMS. These and other issues were studied in this thesis. For this purpose, a large scale test setup, designed to study the detector performance by tracking cosmic muons, was operated over several months. A dedicated trigger system was set up, to select tracks synchronous with the fast readout electronics, and to be able to perform a precise measurement of the time evolution of the front-end signals. Data collected at room temperature and at the Tracker operating temperature of -10°C were used to test reconstruction and alignment algorithms for the Tracker, as well as to perform a detailed qualification of the geometry and the functionality of the structures at different temperatures

Zeroth-order design report for the next linear collider. Volume 1

This Zeroth Order Design Report (ZDR) for the Next Linear Collider (NLC) has been completed as a feasibility study for a TeV-scale linear collider that incorporates a room-temperature accelerator powered by rf microwaves at 11.424 GHz--similar to that presently used in the SLC, but at four times the rf frequency. The purpose of this study is to examine the complete systems of such a collider, to understand how the parts fit together, and to make certain that every required piece has been included. The design presented here is not fully engineered in any sense, but to be assured that the NLC can be built, attention has been given to a number of critical components and issues that present special challenges. More engineering and development of a number of mechanical and electrical systems remain to be done, but the conclusion of this study is that indeed the NLC is technically feasible and can be expected to reach the performance levels required to perform research at the TeV energy scale. Volume one covers the following: the introduction; electron source; positron source; NLC damping rings; bunch compressors and prelinac; low-frequency linacs and compressors; main linacs; design and dynamics; and RF systems for main linacs

Developments toward a Silicon Strip Tracker for the PANDA Experiment

The PANDA detector at the future FAIR facility in Darmstadt will be a key experiment in the understanding of the strong interaction at medium energies where perturbative models fail to describe the quark-quark interaction. An important feature of the detector system is the ability to reconstruct secondary decay vertices of short-lived intermediate states by means of a powerful particle tracking system with the the Micro-Vertex Detector (MVD) as central element to perform high-resolution charmonium and open-charm spectroscopy. The MVD is conceived with pixel detectors in the inner parts and double-sided silicon strip detectors at the outer half in a very lightweight design. The PANDA detector system shall be operated in a self-triggering broadband acquisition mode. Implications on the read-out electronics and the construction of the front-end assemblies are analyzed and evaluation of prototype DSSD-detectors wrt. signal-to-noise ratio, noise figures, charge sharing behavior, spacial resolution and radiation degradation discussed. Methods of electrical sensor characterization with different measurement setups are investigated which may be useful for future large-scale QA procedures. A novel algorithm for recovering multiple degenerate cluster hit patterns of double-sided strip sensors is introduced and a possible architecture of a Module Data Concentrator ASIC (MDC) aggregating multiple front-end data streams conceived. A first integrative concept for the construction and assembly of DSSD modules for the barrel part of the MVD is introduced as a conclusion of the thesis. Furthermore, a detailed description of a simplified procedure for the calculation of displacement damage in compound materials is given as reference which was found useful for the retrieval of non-ionizing energy loss for materials other than silicon.Der PANDA Detektor im zukünftigen FAIR-Beschleunigerkomplex in Darmstadt wird ein Schlüsselexperiment im Verständnis der starken Wechselwirkung bei mittleren Energien, bei denen kein Zugang über perturbative Methoden zur Quark-Quark Interaktion existiert, sein. Eine wichtige Eigenschaft des Detektorsystems, die Ortsrekonstruktion sekundärer Zerfallsvertizes kurzlebiger Zwischenzustände, wird dabei durch ein Spurverfolgungssystem mit dem Mikro-Vertex Detektor (MVD) als wichtigstem Element zur hochauflösenden Charmoniumund Open-Charm Spektroskopie garantiert. Der MVD ist konzipiert als leichtgewichtiges, geteiltes Silizium-Detektorsystem mit Pixeldetektoren im inneren Bereich und doppelseitigen Streifendetektoren (DSSD) in den äußeren Regionen. Das PANDA Detektorsystem soll in einem selbstgetriggertem Regime Daten breitbandig und ohne Totzeitverluste verarbeiten können. Die sich daraus ergebenden Implikationen auf den Aufbau der Ausleseelektronik und der Front-end-Baugruppen werden analysiert und es werden Ergebnisse von Messungen an DSSD-Prototypen im Hinblick auf Signal-zu-Rausch-Verhältnis, Rauscheigenschaften, Ladungsteilungsverhalten, Ortsauflösung und Bestrahlungstoleranz diskutiert. Methoden zur elektrischen Charakterisierung von Sensoren werden untersucht, die bei zukünftigen großangelegten QA-Untersuchungen nützlich eingesetzt werden können. Ein neuartiger Cluster- Korrelationsalgorithmus, welcher mehrfach entartete Clusterhit-Muster zu erkennen vermag wird ebenso vorgestellt wie eine mögliche Architektur des noch zu entwickelnden Module-Data- Concentrator ASIC (MDC), welcher die Datenströme der Front-end Chips auf Modulebene zusammenfassen soll. Ein erstes integratives Konzept für Konstruktion und Zusammenbau von DSSD-Modulen des Barrel-Bereichs des MVD wird im Abschluss der Dissertation vorgestellt. Darüber hinaus wird eine detaillierte Beschreibung einer vereinfachten Vorschrift zur Berechnung des Versetzungsschadens durch Neutronen in zusammengesetzten Stoffen angegeben, welche sich als nützlich für die Ableitung des nicht-ionisierenden Energieverlustes in Materialien neben Silizium erwiesen hat