The new Beam Halo Monitor for the CMS experiment at the LHC

In the context of increasing beam energy and luminosity of the LHC accelerator at CERN, it will be important to accurately measure the Machine Induced Background. A new monitoring system will be installed in the CMS cavern for measuring the beam background at high radius. This detector, called the Beam Halo Monitor, will provide an online, bunch-by-bunch measurement of background induced by beam halo interactions, separately for each beam. The detector is composed of synthetic quartz Cherenkov radiators, coupled to fast UV sensitive photomultiplier tubes. The directional and fast response of the system allows the discrimination of the background particles from the dominant flux in the cavern induced by pp collision debris, produced within the 25 ns bunch spacing. The readout electronics of this detector will make use of many components developed for the upgrade of the CMS Hadron Calorimeter electronics, with a dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal will be digitized by a charge integrating ASIC, providing both the signal rise time and the charge integrated over one bunch crossing. The backend electronics will record bunch-by-bunch histograms, which will be published to CMS and the LHC using the newly designed CMS beam instrumentation specific DAQ. A calibration and monitoring system has been designed to generate triggered pulses of UV light to monitor the efficiency of the system. The experimental results validating the design of the detector, the calibration system and the electronics will be presented

Development of anFPGA-based Data Reduction System for the Belle II DEPFET Pixel Detector

The innermost two layers of the Belle II detector at the KEKB collider in Tsukuba, Japan will be covered by highly granular DEPFET pixel sensors. The large number of pixels lead to a maximum data rate of 256 Gbps, which has to be significantly reduced by the Data Acquisition System. For data reduction, the hit information of the silicon-strip vertex detector surrounding the pixel detector is used to define so-called Regions of Interest (ROI) in the pixel detector. Only hit information of the pixels located inside these ROIs are saved. The ROIs for the pixel detector are computed by reconstructing track segments from strip data and extrapolation to the pixel detector. The goal is to achieve a reduction factor of up to 10 with this ROI selection. All the necessary processing stages, the receiving, decoding and multiplexing of SVD data on 48 optical fibers, the track reconstruction and the definition of the ROIs, will be performed by the DATCON system, developed in the scope of this thesis. The planned hardware design is based on a distributed set of Advanced Mezzanine Cards (AMC), each equipped with a Field Programmable Gate Array (FPGA) and four optical transceivers. An algorithm is developed based on a Hough Transformation, a commonly used pattern recognition method in image processing to identify the track segments in the strip detector and calculation of the track parameters. Using simulations, the performance of the developed algorithms are evaluated. For use in the DATCON system the Hough track reconstruction is implemented on FPGAs. Several tests of the modules required to create the ROIs are performed in a simulation environment and tested on the AMC hardware. After a line of successful tests, the DATCON prototype was used in two test beam campaigns to verify the concept and practice the integration with the other detector systems. The developed track reconstruction algorithm shows a high reconstruction efficiency down to low track momenta. A higher data reduction than originally intended was achieved within the limits of the available processing time. The FPGA track reconstruction algorithm is found to be even three times faster than demanded by the trigger rate of the experiment. The used concepts and developed algorithms are not specifically designed for the Belle II vertex detector only, but can be used in different experiments. It was successfully tested on the low-level trigger for Belle II, using drift chamber information and showed a comparably good track reconstruction performance

Instrumentation of CdZnTe detectors for measuring prompt gamma-rays emitted during particle therapy

Background: The irradiation of cancer patients with charged particles, mainly protons and carbon ions, has become an established method for the treatment of specific types of tumors. In comparison with the use of X-rays or gamma-rays, particle therapy has the advantage that the dose distribution in the patient can be precisely controlled. Tissue or organs lying near the tumor will be spared. A verification of the treatment plan with the actual dose deposition by means of a measurement can be done through range assessment of the particle beam. For this purpose, prompt gamma-rays are detected, which are emitted by the affected target volume during irradiation. Motivation: The detection of prompt gamma-rays is a task related to radiation detection and measurement. Nuclear applications in medicine can be found in particular for in vivo diagnosis. In that respect the spatially resolved measurement of gamma-rays is an essential technique for nuclear imaging, however, technical requirements of radiation measurement during particle therapy are much more challenging than those of classical applications. For this purpose, appropriate instruments beyond the state-of-the-art need to be developed and tested for detecting prompt gamma-rays. Hence the success of a method for range assessment of particle beams is largely determined by the implementation of electronics. In practice, this means that a suitable detector material with adapted readout electronics, signal and information processing, and data interface must be utilized to solve the challenges. Thus, the parameters of the system (e.g. segmentation, time or energy resolution) can be optimized depending on the method (e.g. slit camera, time-of-flight measurement or Compton camera). Regardless of the method, the detector system must have a high count rate capability and a large measuring range (>7 MeV). For a subsequent evaluation of a suitable method for imaging, the mentioned parameters may not be restricted by the electronics. Digital signal processing is predestined for multipurpose tasks, and, in terms of the demands made, the performance of such an implementation has to be determined. Materials and methods: In this study, the instrumentation of a detector system for prompt gamma-rays emitted during particle therapy is limited to the use of a cadmium zinc telluride (CdZnTe, CZT) semiconductor detector. The detector crystal is divided into an 8x8 pixel array by segmented electrodes. Analog and digital signal processing are exemplarily tested with this type of detector and aims for application of a Compton camera to range assessment. The electronics are implemented with commercial off-the-shelf (COTS) components. If applicable, functional units of the detector system were digitalized and implemented in a field-programmable gate array (FPGA). An efficient implementation of the algorithms in terms of timing and logic utilization is fundamental to the design of digital circuits. The measurement system is characterized with radioactive sources to determine the measurement dynamic range and resolution. Finally, the performance is examined in terms of the requirements of particle therapy with experiments at particle accelerators. Results: A detector system based on a CZT pixel detector has been developed and tested. Although the use of an application-specific integrated circuit is convenient, this approach was rejected because there was no circuit available which met the requirements. Instead, a multichannel, compact, and low-noise analog amplifier circuit with COTS components has been implemented. Finally, the 65 information channels of a detector are digitized, processed and visualized. An advanced digital signal processing transforms the traditional approaches of nuclear electronics in algorithms and digital filter structures for an FPGA. With regard to the characteristic signals (e.g. varying rise times, depth-dependent energy measurement) of a CZT pixel detector, it could be shown that digital pulse processing results in a very good energy resolution (~2% FWHM at 511 keV), as well as permits a time measurement in the range of some tens of nanoseconds. Furthermore, the experimental results have shown that the dynamic range of the detector system could be significantly improved compared to the existing prototype of the Compton camera (~10 keV..7 MeV). Even count rates of ~100 kcps in a high-energy beam could be ultimately processed with the CZT pixel detector. But this is merely a limit of the detector due to its volume, and not related to electronics. In addition, the versatility of digital signal processing has been demonstrated with other detector materials (e.g. CeBr3). With foresight on high data throughput in a distributed data acquisition from multiple detectors, a Gigabit Ethernet link has been implemented as data interface. Conclusions: To fully exploit the capabilities of a CZT pixel detector, a digital signal processing is absolutely necessary. A decisive advantage of the digital approach is the ease of use in a multichannel system. Thus with digitalization, a necessary step has been done to master the complexity of a Compton camera. Furthermore, the benchmark of technology shows that a CZT pixel detector withstands the requirements of measuring prompt gamma-rays during particle therapy. The previously used orthogonal strip detector must be replaced by the pixel detector in favor of increased efficiency and improved energy resolution. With the integration of the developed digital detector system into a Compton camera, it must be ultimately proven whether this method is applicable for range assessment in particle therapy. Even if another method is more convenient in a clinical environment due to practical considerations, the detector system of that method may benefit from the shown instrumentation of a digital signal processing system for nuclear applications.:1. Introduction 1.1. Aim of this work 2. Analog front-end electronics 2.1. State-of-the-art 2.2. Basic design considerations 2.2.1. CZT detector assembly 2.2.2. Electrical characteristics of a CZT pixel detector 2.2.3. High voltage biasing and grounding 2.2.4. Signal formation in CZT detectors 2.2.5. Readout concepts 2.2.6. Operational amplifier 2.3. Circuit design of a charge-sensitive amplifier 2.3.1. Circuit analysis 2.3.2. Charge-to-voltage transfer function 2.3.3. Input coupling of the CSA 2.3.4. Noise 2.4. Implementation and Test 2.5. Results 2.5.1. Test pulse input 2.5.2. Pixel detector 2.6. Conclusion 3. Digital signal processing 3.1. Unfolding-synthesis technique 3.2. Digital deconvolution 3.2.1. Prior work 3.2.2. Discrete-time inverse amplifier transfer function 3.2.3. Application to measured signals 3.2.4. Implementation of a higher order IIR filter 3.2.5. Conclusion 3.3. Digital pulse synthesis 3.3.1. Prior work 3.3.2. FIR filter structures for FPGAs 3.3.3. Optimized fixed-point arithmetic 3.3.4. Conclusion 4. Data interface 4.1. State-of-the-art 4.2. Embedded Gigabit Ethernet protocol stack 4.3. Implementation 4.3.1. System overview 4.3.2. Media Access Control 4.3.3. Embedded protocol stack 4.3.4. Clock synchronization 4.4. Measurements and results 4.4.1. Throughput performance 4.4.2. Synchronization 4.4.3. Resource utilization 4.5. Conclusion 5. Experimental results 5.1. Digital pulse shapers 5.1.1. Spectroscopy application 5.1.2. Timing applications 5.2. Gamma-ray spectroscopy 5.2.1. Energy resolution of scintillation detectors 5.2.2. Energy resolution of a CZT pixel detector 5.3. Gamma-ray timing 5.3.1. Timing performance of scintillation detectors 5.3.2. Timing performance of CZT pixel detectors 5.4. Measurements with a particle beam 5.4.1. Bremsstrahlung Facility at ELBE 6. Discussion 7. Summary 8. ZusammenfassungHintergrund: Die Bestrahlung von Krebspatienten mit geladenen Teilchen, vor allem Protonen oder Kohlenstoffionen, ist mittlerweile eine etablierte Methode zur Behandlung von speziellen Tumorarten. Im Vergleich mit der Anwendung von Röntgen- oder Gammastrahlen hat die Teilchentherapie den Vorteil, dass die Dosisverteilung im Patienten präziser gesteuert werden kann. Dadurch werden um den Tumor liegendes Gewebe oder Organe geschont. Die messtechnische Verifikation des Bestrahlungsplans mit der tatsächlichen Dosisdeposition kann über eine Reichweitenkontrolle des Teilchenstrahls erfolgen. Für diesen Zweck werden prompte Gammastrahlen detektiert, die während der Bestrahlung vom getroffenen Zielvolumen emittiert werden. Fragestellung: Die Detektion von prompten Gammastrahlen ist eine Aufgabenstellung der Strahlenmesstechnik. Strahlenanwendungen in der Medizintechnik finden sich insbesondere in der in-vivo Diagnostik. Dabei ist die räumlich aufgelöste Messung von Gammastrahlen bereits zentraler Bestandteil der nuklearmedizinischen Bildgebung, jedoch sind die technischen Anforderungen der Strahlendetektion während der Teilchentherapie im Vergleich mit klassischen Anwendungen weitaus anspruchsvoller. Über den Stand der Technik hinaus müssen für diesen Zweck geeignete Instrumente zur Erfassung der prompten Gammastrahlen entwickelt und erprobt werden. Die elektrotechnische Realisierung bestimmt maßgeblich den Erfolg eines Verfahrens zur Reichweitenkontrolle von Teilchenstrahlen. Konkret bedeutet dies, dass ein geeignetes Detektormaterial mit angepasster Ausleseelektronik, Signal- und Informationsverarbeitung sowie Datenschnittstelle zur Problemlösung eingesetzt werden muss. Damit können die Parameter des Systems (z. B. Segmentierung, Zeit- oder Energieauflösung) in Abhängigkeit der Methode (z.B. Schlitzkamera, Flugzeitmessung oder Compton-Kamera) optimiert werden. Unabhängig vom Verfahren muss das Detektorsystem eine hohe Ratenfestigkeit und einen großen Messbereich (>7 MeV) besitzen. Für die anschließende Evaluierung eines geeigneten Verfahrens zur Bildgebung dürfen die genannten Parameter durch die Elektronik nicht eingeschränkt werden. Eine digitale Signalverarbeitung ist für universelle Aufgaben prädestiniert und die Leistungsfähigkeit einer solchen Implementierung soll hinsichtlich der gestellten Anforderungen bestimmt werden. Material und Methode: Die Instrumentierung eines Detektorsystems für prompte Gammastrahlen beschränkt sich in dieser Arbeit auf die Anwendung eines Cadmiumzinktellurid (CdZnTe, CZT) Halbleiterdetektors. Der Detektorkristall ist durch segmentierte Elektroden in ein 8x8 Pixelarray geteilt. Die analoge und digitale Signalverarbeitung wird beispielhaft mit diesem Detektortyp erprobt und zielt auf die Anwendung zur Reichweitenkontrolle mit einer Compton-Kamera. Die Elektronik wird mit seriengefertigten integrierten Schaltkreisen umgesetzt. Soweit möglich, werden die Funktionseinheiten des Detektorsystems digitalisiert und in einem field-programmable gate array (FPGA) implementiert. Eine effiziente Umsetzung der Algorithmen in Bezug auf Zeitverhalten und Logikverbrauch ist grundlegend für den Entwurf der digitalen Schaltungen. Das Messsystem wird mit radioaktiven Prüfstrahlern hinsichtlich Messbereichsdynamik und Auflösung charakterisiert. Schließlich wird die Leistungsfähigkeit hinsichtlich der Anforderungen der Teilchentherapie mit Experimenten am Teilchenbeschleuniger untersucht. Ergebnisse: Es wurde ein Detektorsystem auf Basis von CZT Pixeldetektoren entwickelt und erprobt. Obwohl der Einsatz einer anwendungsspezifischen integrierten Schaltung zweckmäßig wäre, wurde dieser Ansatz zurückgewiesen, da kein verfügbarer Schaltkreis die Anforderungen erfüllte. Stattdessen wurde eine vielkanalige, kompakte und rauscharme analoge Verstärkerschaltung mit seriengefertigten integrierten Schaltkreisen aufgebaut. Letztendlich werden die 65 Informationskanäle eines Detektors digitalisiert, verarbeitet und visualisiert. Eine fortschrittliche digitale Signalverarbeitung überführt die traditionellen Ansätze der Nuklearelektronik in Algorithmen und digitale Filterstrukturen für einen FPGA. Es konnte gezeigt werden, dass die digitale Pulsverarbeitung in Bezug auf die charakteristischen Signale (u.a. variierende Anstiegszeiten, tiefenabhängige Energiemessung) eines CZT Pixeldetektors eine sehr gute Energieauflösung (~2% FWHM at 511 keV) sowie eine Zeitmessung im Bereich von einigen 10 ns ermöglicht. Weiterhin haben die experimentellen Ergebnisse gezeigt, dass der Dynamikbereich des Detektorsystems im Vergleich zum bestehenden Prototyp der Compton-Kamera deutlich verbessert werden konnte (~10 keV..7 MeV). Nach allem konnten auch Zählraten von >100 kcps in einem hochenergetischen Strahl mit dem CZT Pixeldetektor verarbeitet werden. Dies stellt aber lediglich eine Begrenzung des Detektors aufgrund seines Volumens, nicht jedoch der Elektronik, dar. Zudem wurde die Vielseitigkeit der digitalen Signalverarbeitung auch mit anderen Detektormaterialen (u.a. CeBr3) demonstriert. Mit Voraussicht auf einen hohen Datendurchsatz in einer verteilten Datenerfassung von mehreren Detektoren, wurde als Datenschnittstelle eine Gigabit Ethernet Verbindung implementiert. Schlussfolgerung: Um die Leistungsfähigkeit eines CZT Pixeldetektors vollständig auszunutzen, ist eine digitale Signalverarbeitung zwingend notwendig. Ein entscheidender Vorteil des digitalen Ansatzes ist die einfache Handhabbarkeit in einem vielkanaligen System. Mit der Digitalisierung wurde ein notwendiger Schritt getan, um die Komplexität einer Compton-Kamera beherrschbar zu machen. Weiterhin zeigt die Technologiebewertung, dass ein CZT Pixeldetektor den Anforderungen der Teilchentherapie für die Messung prompter Gammastrahlen stand hält. Der bisher eingesetzte Streifendetektor muss zugunsten einer gesteigerten Effizienz und verbesserter Energieauflösung durch den Pixeldetektor ersetzt werden. Mit der Integration des entwickelten digitalen Detektorsystems in eine Compton-Kamera muss abschließend geprüft werden, ob dieses Verfahren für die Reichweitenkontrolle in der Teilchentherapie anwendbar ist. Auch wenn sich herausstellt, dass ein anderes Verfahren unter klinischen Bedingungen praktikabler ist, so kann auch dieses Detektorsystem von der gezeigten Instrumentierung eines digitalen Signalverarbeitungssystems profitieren.:1. Introduction 1.1. Aim of this work 2. Analog front-end electronics 2.1. State-of-the-art 2.2. Basic design considerations 2.2.1. CZT detector assembly 2.2.2. Electrical characteristics of a CZT pixel detector 2.2.3. High voltage biasing and grounding 2.2.4. Signal formation in CZT detectors 2.2.5. Readout concepts 2.2.6. Operational amplifier 2.3. Circuit design of a charge-sensitive amplifier 2.3.1. Circuit analysis 2.3.2. Charge-to-voltage transfer function 2.3.3. Input coupling of the CSA 2.3.4. Noise 2.4. Implementation and Test 2.5. Results 2.5.1. Test pulse input 2.5.2. Pixel detector 2.6. Conclusion 3. Digital signal processing 3.1. Unfolding-synthesis technique 3.2. Digital deconvolution 3.2.1. Prior work 3.2.2. Discrete-time inverse amplifier transfer function 3.2.3. Application to measured signals 3.2.4. Implementation of a higher order IIR filter 3.2.5. Conclusion 3.3. Digital pulse synthesis 3.3.1. Prior work 3.3.2. FIR filter structures for FPGAs 3.3.3. Optimized fixed-point arithmetic 3.3.4. Conclusion 4. Data interface 4.1. State-of-the-art 4.2. Embedded Gigabit Ethernet protocol stack 4.3. Implementation 4.3.1. System overview 4.3.2. Media Access Control 4.3.3. Embedded protocol stack 4.3.4. Clock synchronization 4.4. Measurements and results 4.4.1. Throughput performance 4.4.2. Synchronization 4.4.3. Resource utilization 4.5. Conclusion 5. Experimental results 5.1. Digital pulse shapers 5.1.1. Spectroscopy application 5.1.2. Timing applications 5.2. Gamma-ray spectroscopy 5.2.1. Energy resolution of scintillation detectors 5.2.2. Energy resolution of a CZT pixel detector 5.3. Gamma-ray timing 5.3.1. Timing performance of scintillation detectors 5.3.2. Timing performance of CZT pixel detectors 5.4. Measurements with a particle beam 5.4.1. Bremsstrahlung Facility at ELBE 6. Discussion 7. Summary 8. Zusammenfassun

Longitudinal oxygen imaging in 3D (bio)printed models

Electron paramagnetic resonance (EPR), and its molecular imaging modality, is a powerful tool to noninvasively map various biological and chemical markers within objects of interest. Reliable data acquisition is a major impeding factor for longitudinal hands-off measurements. Measurements are especially challenging in biomedical applications, as live objects are not static. Frequent changes occur that require constant fine recalibration of the EPR detection system, called the resonator. To enable longitudinal imaging, a technology permitting automatic digital control of resonator coupling, tuning, and EPR data acquisition was developed. Automation was achieved through the utilization of a microcontroller and digital peripheral components such as digitally controlled capacitors, a digital frequency source, and a printed circuit board resonator. Several applications of this technology have been suggested and tested, including in vivo EPR imaging. The first was to develop a tool for the optimization of light-based 3D printing, for which oxygen plays a major role. Towards this goal, an EPR oxygen-sensitive probe was incorporated into 3D printing resin. Oxygen depletion was measured during the 3D printing process as the polymerization front progressed. After printing, oxygen depletion was again measured during the post-curing process, proposed as a method to optimize post-curing light intensity, temperature, and duration in order to produce quality 3D printed constructs. The second application of longitudinal EPR imaging was directed toward resolving an important problem of oxygen delivery to thick (\u3e1 cm) bioprinted models. Oxygen-sensitive EPR probes (water-soluble trityls or crystalline lithium octa-n-butoxynaphthalocyanine) were introduced into bioinks (liquid hydrogels containing cells, nutrients, and other biological factors) before printing. Bioinks become solid structures after printing due to crosslinking. EPR imaging was demonstrated to measure oxygen consumption by the cells embedded in the bioprints. As expected, an increase of oxygen depletion was observed by introducing a nutrient (pyruvate) to bioink. A numerical MATLAB simulation program was developed to predict rates of oxygen consumption by the cells in the bioprint. The input parameters for the mathematical model include the size and number of cells, the diffusion coefficient of the media, and rates of oxygen transfer through the cell membrane. The software is being further refined and optimized for computational speed. Future efforts will be aimed at improving the speed and scope of EPR automatic digital control, imaging the oxygen depletion process in commercial 3D printers, and applying EPR mapping of oxygen consumption rate to quantify the delivery of oxygen to cells deep inside bioprinted tissue models. Optimizing the delivery of oxygen to cells would overcome the challenge of the limit of diffusion, facilitating the development of larger and more complex bioprinted tissues and organs. These complex tissue and organ models are envisioned for use in drug testing, biomedical research, and, in the distant future, implants in humans

Digital control systems in the regeneration cavity of ALPS IIa

ALPS II ist ein Licht durch die Wand-Experiment, das nach axionartigen Teilchen sucht. Diese Experimente zielen darauf ab axionartige Teilchen in einem Labor zu erzeugen und zu messen, wobei in Gegenwart eines Magnetfelds die Oszillation zwischen Photonen und axionartige Teilchen erfolgt. ALPS II baut auf die Neuerungen seines Vorgängerexperiments ALPS I auf: optische Resonatoren zur Verbesserung der Empfindlichkeit. ALPS II wird einen Produktionsresonator (PC) verwenden, um die Anzahl der zur Erzeugung von axionartigen Teilchen verfügbaren Photonen zu erhöhen und einen Regenerationsresonator (RC), um die Wahrscheinlichkeit zu erhöhen, dass axionartige Teilchen zurück in Photonen konvertieren. Um das Licht in den Resonatoren resonant zu überhöhen, muss das auf den Resonator einfallende Laserlicht, auch in Gegenwart von Rauschquellen, an die Resonanz des Resonators angepasst werden. Zusätzlich müssen die Resonanzen der beiden Resonatoren so aufeinander abgestimmt werden, dass die Rekonversionswahrscheinlichkeit der axionartigen Teilchen im RC erhöht wird. Die Anforderung an das Frequenzrauschen zwischen den beiden Resonatoren für ALPS IIc müssen kleiner sein als eine Effektivwertabweichung (RMS) von 3.0 Hz. Dies erfordert die Verwendung von Regelkreisen mit hohen Regelbandbreiten. ALPS IIa ist ein kleineres Experiment zum Testen und Charakterisieren kritischer Systeme für den Einsatz in ALPS IIc. ALPS IIa verfügt über Räumlichkeiten, in denen zwei Resonatoren, ähnlich der PC und RC in ALPS IIc, aufgebaut sind. Regelkreise können entworfen und getestet werden, um sie für die Eignung in ALPS IIc zu testen und die Leistungsfähigkeit alternativer Designs kann im kleinen Maßstab evaluiert werden. In dieser Dissertation werden die grundlegenden analogen Regelkreise der ALPS IIa RC charakterisiert. Dazu gehören Frequenzstabilisierungssysteme für zwei Laserquellen und ein Längenstabilisierungssystem. Das Rauschen dieses Längenstabilisierungssystems wird auf die Anforderungen der Resonanzüberlappung zwischen den beiden Resonatoren projiziert und ein RMS Wert von 1.0 Hz sollte mit diesem System erreicht werden. Um die Funktionsfähigkeit digitaler Regelsysteme zu untersuchen, werden zwei digitale Frequenzstabilisierungssysteme getestet: eines, das analoge Servo ersetzt, und eines, das zusätzlich das analoge Demodulationssystem ersetzt. Das RMS des Frequenzrauschens beider digitaler Systeme liegt innerhalb eines Faktors von zwei des vollständig analogen Systems. Das System mit der digitalen Demodulation ist das leistungsfähigere der beiden Systeme. Ein vollständig digitales System ist so ausgelegt, dass es Phasenänderungen zwischen dem in den beiden Resonatoren zirkulierenden Licht erfasst, um Phasendifferenzen zu minimieren. Dieses System kann die Laserfrequenz beeinflussen und eine ähnliche Stabilität wie andere Frequenzstabilisierungsysteme erreichen.ALPS II is a light-shining-through-a-wall experiment that will search for axion-like particles. These experiments seek to generate and measure axion-like particles in a laboratory using oscillations between photons and axions in the presence of a magnetic field. ALPS II builds on the innovation of its predecessor, ALPS I: optical cavities to enhance the sensitivity. ALPS II will use a production cavity (PC) to increase the number of photons available to generate axion-like particles, and a regeneration cavity (RC) to enhance the probability of the axion-like particles oscillating back into photons. To resonantly enhance the light in the cavities, the input laser light needs to be well-matched to the resonance of the cavities even in the presence of disturbances. Additionally, the resonances of the two cavities must be matched such that the axion-like particles' reconversion probability is enhanced in the RC. The requirement on the frequency noise between the two cavities for ALPS IIc is a root-mean-square (RMS) deviation of smaller than 3.0 Hz. This necessitates the use of high-performance control loops. ALPS IIa is a smaller-scale experiment to test and characterize critical systems for use in the full-scale ALPS IIc. ALPS IIa has the facilities for two cavities to mirror the PC and RC in ALPS IIc. Control systems can be designed and tested to determine their suitability for use in ALPS IIc, and alternative designs can be compared based on their performance in the short-scale experiment. In this thesis, the baseline analog control systems in the ALPS IIa RC are characterized. These include frequency actuation systems for two laser sources, and a length actuation system. The noise of this length actuation system is projected onto the requirements of the resonance overlap between the two cavities and an RMS of 1.0 Hz should be achievable with this system. In order to investigate the viability of digital control systems, two digital frequency control systems are tested: one that replaces the analog servo, and one that replaces the analog demodulation system as well. The RMS of the frequency noise of both digital systems is within a factor of two of the fully analog system. The system with the digital demodulation is the better-performing of the two. A fully digital system is designed to sense phase changes between the light circulating in the two cavities to minimize that phase difference. This system is able to actuate on laser frequency to achieve similar performance to other frequency control systems

Mu2e Technical Design Report

The Mu2e experiment at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --> e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the preliminary design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-2 approval.Comment: compressed file, 888 pages, 621 figures, 126 tables; full resolution available at http://mu2e.fnal.gov; corrected typo in background summary, Table 3.

Cavity Field Control for Linear Particle Accelerators

High-energy linear particle accelerators enable exploration of the microscopic structure of pharmaceuticals, solar cells, fuel cells, high-temperature superconductors, and the universe itself. These accelerators accelerate charged particles using oscillating magnetic fields that are confined in metal cavities. The amplitudes and phases of the electromagnetic fields need to be accurately controlled by fast feedback loops for proper accelerator operation.This thesis is based on the author's work on performance analysis and control design for the field control loops of the linear accelerator at the European Spallation Source (ESS), a neutron microscope that is under construction in Lund, Sweden. The main contribution of the thesis is a comprehensive treatment of the field control problem during flat-top, which gives more insight into the control aspects than previous work. The thesis demonstrates that a key to understand the dynamics of the field control loop is to represent it as a single-input single-output system with complex coefficients. This representation is not new itself but has seen limited use for field control analysis.The thesis starts by developing practical and theoretical tools for analysis and control design for complex-coefficients systems. This is followed by two main parts on cavity field control. The first part introduces parametrizations that enable a better understanding of the cavity dynamics and discusses the most essential aspects of cavity field control. The second part builds on the first one and treats a selection of more advanced topics that all benefit from the complex-coefficient representation: analysis of a polar controller structure, field control design in the presence of parasitic cavity resonances, digital downconversion for low-latency feedback, energy-optimal excitation of accelerating cavities, and an intuitive design method for narrowband disturbance rejection. The results of the investigations in this thesis provide a better understanding of the field control problem and have influenced the design of the field controllers at ESS