Siemens Corporate Technology New Technology Fields Healthcare & Technology Concepts (CT NTF HTC) have proposed a novel electrostatic accelerator for nuclear medicine which aims at gradients of up to 10 MV m^-1. With beam currents of 100 μA at ≈10 MeV it might replace cyclotrons whilst being simpler, more reliable and more cost effective. The accelerator concept consists of concentric hemispherical metallic shells spaced by insulators and placed in a vacuum system. The shells are interconnected by high voltage diodes so that they form a voltage multiplier with its highest voltage in its centre. Particle beams can be accelerated towards the centre through a set of holes in the shells. In tandem mode, with a stripper in the centre and a negative ion source as injector, beams of twice the centre voltage can be achieved. This thesis presents several commissioning milestones of a test system for the novel electrostatic accelerator, thus validating the concept for commercial applications. An inter shell insulator has been designed and successfully tested to fields of 12 MV m^-1. A diode protection concept has been devised and validated in realistic breakdown scenarios. An AC drive system including control software has been developed, delivering a sinusoidal input voltage of up to 140 kV peak to peak at 80 kHz. An automatic process to carefully commission the high voltage system in vacuum has been created, implemented in a control system and successfully operated. A 4-shell prototype with these components has been successfully tested with achieved gradients of up to 5.5 MV m^-1. A negative hydrogen ion source has been constructed, commissioned and characterised with a purposely developed wire grid. Beam currents beyond 200 μA have been achieved. Beam transport from the ion source through the 7-shell system has been demonstrated in simulations which are based on experimental data from the ion source characterisation. A stripper system has been designed and constructed.

<p>The Duke Free-electron laser (FEL) system, driven by the Duke electron storage ring, has been at the forefront of developing new light source capabilities over the past two decades. In 1999, the Duke FEL demonstrated the first lasing of a storage ring FEL in the vacuum ultraviolet (VUV) region at $194$ nm using two planar OK-4 undulators. With two helical undulators added to the outboard sides of the planar undulators, in 2005 the highest FEL gain ($47.8\%$) of a storage ring FEL was achieved using the Duke FEL system with a four-undulator configuration. In addition, the Duke FEL has been used as the photon source to drive the High Intensity $\gamma$-ray Source (HIGS) via Compton scattering of the FEL beam and electron beam inside the FEL cavity. Taking advantage of FEL's wavelength tunability as well as the adjustability of the energy of the electron beam in the storage ring, the nearly monochromatic $\gamma$-ray beam has been produced in a wide energy range from $1$ to $100$ MeV at the HIGS. To further push the FEL short wavelength limit and enhance the FEL gain in the VUV regime for high energy $\gamma$-ray production, two additional helical undulators were installed in 2012 using an undulator switchyard system to allow switching between the two planar and two helical undulators in the middle section of the FEL system. Using different undulator configurations made possible by the switchyard, a number of novel capabilities of the storage ring FEL have been developed and exploited for a wide FEL wavelength range from infrared (IR) to VUV. These new capabilities will eventually be made available to the $\gamma$-ray operation, which will greatly enhance the $\gamma$-ray user research program, creating new opportunities for certain types of nuclear physics research.</p><p>With the wide wavelength tuning range, the FEL is an intrinsically well-suited device to produce lasing with multiple colors. Taking advantage of the availability of an undulator system with multiple undulators, we have demonstrated the first two-color lasing of a storage ring FEL. Using either a three- or four-undulator configuration with a pair of dual-band high reflectivity mirrors, we have achieved simultaneous lasing in the IR and UV spectral regions. With the low-gain feature of the storage ring FEL, the power generated at the two wavelengths can be equally built up and precisely balanced to reach FEL saturation. A systematic experimental program to characterize this two-color FEL has been carried out, including precise power control, a study of the power stability of two-color lasing, wavelength tuning, and the impact of the FEL mirror degradation. Using this two-color laser, we have started to develop a new two-color $\gamma$-ray beam for scientific research at the HIGS.</p><p>Using the undulator switchyard, four helical undulators installed in the beamline can be configured to not only enhance the FEL gain in the VUV regime, but also allow for the full polarization control of the FEL beams. For the accelerator operation, the use of helical undulators is essential to extend the FEL mirror lifetime by reducing radiation damage from harmonic undulator radiation. Using a pair of helical undulators with opposite helicities, we have realized (1) fast helicity switching between left- and right-circular polarizations, and (2) the generation of fully controllable linear polarization. In order to extend these new capabilities of polarization control to the $\gamma$-ray operation in a wide energy range at the HIGS, a set of FEL polarization diagnostic systems need to be developed to cover the entire FEL wavelength range. The preliminary development of the polarization diagnostics for the wavelength range from IR to UV has been carried out.</p> / Dissertation

Kommersiellt entreprenörskap är den vanligaste formen av entreprenörskap, men under de senaste decennierna har samhällsentreprenörskap fått en mer betydande roll (Austin et al., 2006, s. 1). Mycket är ostuderat kring samhällsentreprenörskap, främst gällande processen att starta och utveckla samhällsorienterade företag (Martínez et al., 2018, s. 2). Drivkrafterna hos en samhällsentreprenör fokuserar på att bidra till samhällsnytta till skillnad från en kommersiell entreprenör där fokus ligger på ekonomisk tillväxt (Sastre-Castillo et al., 2015, s. 354). I och med detta fokus kan en del hinder och svårigheter för samhällsentreprenörer identifieras. Dessa är enligt Oganisjana et al.  (2017, s. 34) bristande kompetens, begränsade kontaktnät, höga risker, bristande finansieringsmöjligheter och brist på mätbarhet. För att underlätta dessa hinder finns möjligheten att få vägledning från en accelerator. En accelerator fokuserar på att effektivisera lärandet hos entreprenörer, förbättra deras innovativa förmåga och utbilda entreprenörer inom affärsutveckling (Levinsohn, 2014, s. 4).   Efter vår undersökning av tidigare forskning upplevde vi ett gap i forskningen kring kopplingen mellan en accelerator och samhällsentreprenörer. Med detta som grund är syftet med studien att berika den forskning som finns gällande samhällsentreprenörskap och undersöka hur en accelerator påverkar samhällsentreprenörer i processen från idé till hållbar verksamhet, vilket leder fram till vår frågeställning: Hur påverkar acceleratorer samhällsentreprenörer i processen från idé till hållbar verksamhet? För att svara på denna frågeställning utförde vi en kvalitativ studie med en grupp samhällsentreprenörer som alla är anslutna till en accelerator. Datainsamlingsmetoden som användes var semi-strukturerade intervju i fokusgrupp och därefter genomfördes en analys för att hitta mönster och återkommande teman i datan. Från våra respondenter kunde vi utläsa att det finns ett antal hinder och svårigheter som uppkommer under processen. De största svårigheterna som identifierades är kombinationen av samhällsnytta och lönsamhet, att legitimera verksamheten genom att formulera och förmedla ett värdeerbjudande, finansiering och en förlängd startfas. För att överkomma dessa hinder anser respondenterna att passion och empati är de viktigaste egenskaperna och därmed ses kompetenser som sekundärt.   Resultatet från denna studie påvisar att genom att bortse från vikten av kompetens i uppstarten av verksamheten synliggörs tecken på begränsad rationalitet och samhällsentreprenörerna löper därmed risken att förlänga uppstartsfasen då anskaffning av kompetenser inte får tillräckligt stort fokus. Detta i kombination med de hinder och svårigheter som identifierats leder till en förlängd startfas där samhällsentreprenörerna genomgår både en utvecklingsfas och även en etableringsfas. Etableringsfasen innefattar svårigheter som utveckling av en stabil kundbas och hållbar finansiering. Baserat på detta anser vi att samhällsacceleratorer i stor utsträckning påverkar samhällsentreprenörer i deras process då de kan vägleda och utbilda dem genom att uppmärksamma begränsad rationalitet och därmed även vikten av kompetens. Genom denna vägledning kan processen underlättas och förkortas vilket kan medföra reducerade svårigheter. Således kan denna studie bidra med kunskap kring acceleratorers påverkan på den samhällsentreprenöriella processen.

Moore’s law reaching its physical limitations has pushed the industry to produce multicore processors. However, programming those processors with an imperative language is not easy since it requires developers to create and synchronize threads. A pure functional language is an adequate tool for this task both from the architectural point of view and from the developer’s. We will show that an architecture can benefit from the implicit parallelism present on functional programs and from the lack of side effects making it easier to parallelize. The developer benefits from functional languages from the superior expressiveness of the language to avoid bugs. In this dissertation, we present the ACQuA architecture, a multicore accelerator created to explore parallelism available in function calls from a pure functional program. ACQuA uses hardware support and a specificallytailored memory organization to minimize the overheads of scheduling, communication, and synchronization. Function calls are placed into a queue and are scheduled to different processing units. The processing units are interconnected and exchange results from function applications. In this work we defined a high level model of the accelerator and how to compile a functional program to it. We also simulated the accelerator and evaluated results, such as speedup, memory usage, and communication overhead of the proposed architecture. We defined the necessary traits of a program to achieve a good speedup on the architecture. On the ideal use case, we can increase the speed up at the same rate we increase the number of processing units in the architecture.

In the Large Hadron Collider (LHC), particle physics events are created by colliding high energy proton beams at a number of interaction points around the ring. One of the main performance indicating parameters of the LHC is the luminosity. The luminosity is limited by, amongst other things, the strength of the beam-beam interaction. In this thesis, the effect of the beam-beam interaction on the luminosity performance of the LHC and the proposed High Luminosity Large Hadron Collider (HL-LHC) is investigated. Results from a number of dedicated, long-range beam-beam machine studies are presented and analysed. In these studies, the minimum beam-beam separation for two different beta star— optics are identified. This separation defines the minimum operational crossing angle in the LHC. The data from these studies are then compared to simulation of the dynamic aperture and the results are discussed. In addition to studies of the LHC, an analytical approach is derived in order to describe the hourglass effect, which may become a contributing factor in limiting the luminosity performance of the HL-LHC.

Superconducting thin films are a possible alternative to bulk niobium for superconducting radio frequency cavity applications. Thin film cavities have produced larger Q0 than bulk niobium at low accelerating voltages [1], are less susceptible to external magnetic fields and therefore require less magnetic shielding than bulk niobium cavities [2] and can benefit from substrates which conduct heat more effectively than bulk niobium [3]. The major drawback for current thin film cavity technology is the large Q slope which is observed above accelerating gradients of 6 7 MV/m. The mechanism for the Q slope is not yet fully understood. Theories have been suggested but are not accepted by everyone within the scientific community [2, 4, 5, 6, 7]. It is assumed that a better understanding of the physical properties of superconducting films is required before the origins of the sharp Q slope can be elucidated. This study has been conducted to better understand the physical properties of superconducting thin films deposited by the magnetron sputtering process. In particular, superconducting niobium films have been deposited by high power impulse magnetron sputtering (HiPIMS) and tested by a wide range of analytical techniques as a function of the substrate temperature and applied bias during deposition. Analytical techniques which have been used include x-ray diffraction crystallography, Rutherford backscattering spectroscopy, scanning electron microscopy, residual resistance ratio, DC magnetometry and RF surface resistance measurements. Results showed that the application of an applied bias during deposition resulted in increased energy of bombarding ions and enhanced rates of surface diffusion and defect annihilation within the microstructure of a growing niobium film. However, large numbers of random complex defects formed once the energy of bombarding ions becomes too large. The systematic approach that was described to investigate the changing morphological and DC superconducting properties of deposited films, as a function of the applied bias, allowed the identification of which process conditions produce the fewest random complex defects. The same systematic investigations could be applied to any HiPIMS deposition facility to provide similar results. An important observation during the study is that the initial substrate conditions have a large influence on the properties of a deposited niobium film. Niobium films deposited onto polycrystalline copper substrate that was pre-annealed at 700 ˚C prior to deposition displayed more stable magnetic flux pinning, larger RRR and an enhanced resistance to the onset of flux penetration, than was observed for films deposited with a wide range of process conditions onto as received copper substrate. Superconductors other than niobium have been successfully deposited by HiPIMS and tested. Niobium titanium nitride thin films displayed a superconducting transition temperature up to 16.7 K, with a normal state resistivity as small as 45±7 μΩcm. The findings suggest that similar niobium titanium nitride thin films could produce smaller RF surface resistance than bulk niobium cavities at 4.2 K.

abstract: With the end of Dennard scaling and Moore's law, architects have moved towards heterogeneous designs consisting of specialized cores to achieve higher performance and energy efficiency for a target application domain. Applications of linear algebra are ubiquitous in the field of scientific computing, machine learning, statistics, etc. with matrix computations being fundamental to these linear algebra based solutions. Design of multiple dense (or sparse) matrix computation routines on the same platform is quite challenging. Added to the complexity is the fact that dense and sparse matrix computations have large differences in their storage and access patterns and are difficult to optimize on the same architecture. This thesis addresses this challenge and introduces a reconfigurable accelerator that supports both dense and sparse matrix computations efficiently. The reconfigurable architecture has been optimized to execute the following linear algebra routines: GEMV (Dense General Matrix Vector Multiplication), GEMM (Dense General Matrix Matrix Multiplication), TRSM (Triangular Matrix Solver), LU Decomposition, Matrix Inverse, SpMV (Sparse Matrix Vector Multiplication), SpMM (Sparse Matrix Matrix Multiplication). It is a multicore architecture where each core consists of a 2D array of processing elements (PE). The 2D array of PEs is of size 4x4 and is scheduled to perform 4x4 sized matrix updates efficiently. A sequence of such updates is used to solve a larger problem inside a core. A novel partitioned block compressed sparse data structure (PBCSC/PBCSR) is used to perform sparse kernel updates. Scalable partitioning and mapping schemes are presented that map input matrices of any given size to the multicore architecture. Design trade-offs related to the PE array dimension, size of local memory inside a core and the bandwidth between on-chip memories and the cores have been presented. An optimal core configuration is developed from this analysis. Synthesis results using a 7nm PDK show that the proposed accelerator can achieve a performance of upto 32 GOPS using a single core. / Dissertation/Thesis / Masters Thesis Computer Engineering 2018

Following the discovery of the Higgs-like boson at the Large Hadron Collider, there is demand for precision measurements on recent findings. The Compact Linear Collider, CLIC, is a candidate for a future linear electron-positron collider for such precision measurements. In CLIC, the beams will be brought to collisions in the multi-TeV regime through high gradient acceleration with high frequency RF power. A high intensity electron beam, the so-called drive beam, will serve as the power source for the main beam, as the drive beam is decelerated in special structures, from which power is extracted and transfered to the main beam. When the drive beam is decelerated the beam quality deteriorates and the momentum spread increases, which makes the beam transport challenging. Dedicated diagnostics to monitor the momentum profile along each bunch train and transverse profile diagnostics will be needed to guarantee the reliability of the decelerator and consequently the power source of the main beam acceleration. A test facility, CTF3, has been constructed at CERN to validate key technical aspects of the CLIC concept. The beam quality in the decelerator will be investigated in the test beam line, TBL, where several power extraction structures reduce the drive beam energy by up to 55%. At the same time, the single-bunch rms energy spread grows from the initial value of 1% to almost 6%. To monitor the parameters of such a beam is challenging but crucial for the optimization of the beamline. In this thesis we report on progress made on adapting generally used methods for beam profile measurements to the demanding conditions of a wide momentum profile. Two detector technologies are used for measuring transverse profile and momentum profile and we discuss the performance of these instruments, in the view of the large momentum spread and with the outlook towards equivalent beam profile monitors in the CLIC decelerator.

At the Los Alamos Neutron Science Center accelerator complex, protons are accelerated to 800 MeV and directed to two tungsten targets, Target 4 at the Weapons Neutron Research facility and the 1L target at the Lujan Center. The Department of Energy requires hazard classification analyses to be performed on these targets and places limits on certain radionuclide inventories in the targets to avoid characterizing the facilities as nuclear facilities. Gadolinium-148 is a radionuclide created from the spallation of tungsten. Allowed isotopic inventories are particularly low for this isotope because it is an alpha-particle emitter with a 75-year half-life. The activity level of Gadolinium-148 is low, but it encompasses almost two-thirds of the total dose burden for the two tungsten targets based on present yield estimates. From a hazard classification standpoint, this severely limits the lifetime of these tungsten targets. The cross section is not well-established experimentally and this is the motivation for measuring the Gadolinium-148 production cross section from tungsten. In a series of experiments at the Weapons Neutron Research facility, Gadolinium-148 production was measured for 600- and 800-MeV protons on tungsten, tantalum, and gold. These experiments used 3 m thin tungsten, tantalum, and gold foils and 10 m thin aluminum activation foils. In addition, spallation yields were determined for many short-lived and long-lived spallation products with these foils using gamma and alpha spectroscopy and compared with predictions of the Los Alamos National Laboratory codes CEM2k+GEM2 and MCNPX. The cumulative Gadolinium-148 production cross section measured from tantalum, tungsten, and gold for incident 600-MeV protons were 15.24.0, 8.310.92, and 0.5910.155, respectively. The average production cross sections measured at 800 MeV were 28.63.5, 19.41.8, and 3.690.50 for tantalum, tungsten, and gold, respectively. These cumulative measurements compared best with Bertini and were within a factor of two to three of CEM2k+GEM2.

For decades, the semiconductor industry enjoyed exponential improvements in microprocessor power and performance with the device scaling of successive technology generations. Scaling limitations at sub-micron technologies, however, have ceased to provide these historical performance improvements within a limited power budget. While device scaling provides a larger number of transistors per chip, for the same chip area, a growing percentage of the chip will have to be powered off at any given time due to power constraints. As such, the architecture community has focused on energy-efficient designs and is looking to specialized hardware to provide gains in performance. A focus on energy efficiency, along with increasingly less reliable transistors due to device scaling, has led to research in the area of approximate computing, where accuracy is traded for energy efficiency when precise computation is not required. There is a growing body of approximation-tolerant applications that, for example, compute on noisy or incomplete data, such as real-world sensor inputs, or make approximations to decrease the computation load in the analysis of cumbersome data sets. These approximation-tolerant applications span application domains, such as machine learning, image processing, robotics, and financial analysis, among others. Since the advent of the modern processor, computing models have largely presumed the attribute of accuracy. A willingness to relax accuracy requirements, however, with goal of gaining energy efficiency, warrants the re-investigation of the potential of analog computing. Analog hardware offers the opportunity for fast and low-power computation; however, it presents challenges in the form of accuracy. Where analog compute blocks have been applied to solve fixed-function problems, general-purpose computing has relied on digital hardware implementations that provide generality and programmability. The work presented in this thesis aims to answer the following questions: Can analog circuits be successfully integrated into general-purpose computing to provide performance and energy savings? And, what is required to address the historical analog challenges of inaccuracy, programmability, and a lack of generality to enable such an approach? This thesis work investigates a neural approach as a means to address the historical analog challenges of inaccuracy, programmability, and generality and to enable the use of analog circuits in general-purpose, high-performance computing. The first piece of this thesis work investigates the use of analog circuits at the microarchitecture level in the form of an analog neural branch predictor. The task of branch prediction can tolerate imprecision, as roll-back mechanisms correct for branch mispredictions, and application-level accuracy remains unaffected. We show that analog circuits enable the implementation of a highly-accurate, neural-prediction algorithm that is infeasible to implement in the digital domain. The second piece of this thesis work presents a neural accelerator that targets approximation-tolerant code. Analog neural acceleration provides application speedup of 3.3x and energy savings of 12.1x with a quality loss less than 10% for all except one approximation-tolerant benchmark. These results show that, using a neural approach, analog circuits can be applied to provide performance and energy efficiency in high-performance, general-purpose computing. / text