The work in this thesis covers the design, growth and characterisation of neutron multilayers. The performance of these multilayers is highly dependent on the obtained interface width between the layers, even a modest improvement can offer a substantial increase in reflectivity performance. As multilayers are such an integral component of many neutron optical instruments, any improvement in terms of reflectivity performance has broad implications for all neutron scattering experiments. This project has been carried out with the construction of the European Spallation Source (ESS) in mind, but the principles extend to all neutron scattering sources. Ni/Ti is the conventional material system of choice for neutron optical components due to the high contrast in scattering length density (SLD). The reflected intensity of such components is largely dependent on the interface width, caused by the formation of nanocrystallites, interdiffusion, and/or intermixing. Apart from hampering the reflectivity performance, the finite interface width between the layers also limits the minimum usable layer thickness in the mirror stack. The formation of nanocrystallites has been eliminated by co-depositing of B4C . This has been combined with a modulated ion assistance scheme to smoothen the interfaces. X-ray reflectivity (XRR) measurements show significantly improvements compared to pure Ni/Ti multilayers. This has further been investigated using low neutron-absorbing 11B4C instead. After deposition, the 11B4C containing films have been characterized using neutron reflectometry, X-ray reflectivity, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy. A large part of his work has focused on fitting X-ray and neutron reflectivity measurements in order to obtain structural parameters. The fits to the experimental data suggest a significant improvement in interface width for the samples that have been co-deposited with 11B4C using a modulated ion assistance scheme during deposition. Any accumulation of roughness has been eliminated, and the average initial interface width at the first bilayer has been reduced from 6.3 Å to 4.5 Å per bilayer. The respective reflectivity performance for these structural parameters have been simulated for a neutron supermirror (N = 5000) for both materials at a neutron wavelength at λ = 3 Å using the IMD software. The predicted reflectivity performance for the 11B4C containing samples amounts to about 71%, which is a significant increase compared to the pure Ni/Ti samples which have a predicted reflectivity of 62%. This results in a reflectivity increase from 0.84% to 3.3% after a total of 10 reflections, resulting in more than 400% higher neutron flux at experiment.

The purpose of the project described in this paper has been to complete construction and to determine the operating characteristics of a charging system and a corona-type controlled leakage system for the compact Van de Graaf generator now under construction at North Texas State University. Calibration data of the generating voltmeter to be used for determining the potential developed by the generator are also included in the paper.

High electrical fields are needed inside the accelerating cavities of particle accelerators in order to accelerate the particles to higher energies in shorter distances. But high electrical fields will lead to electrical breakdowns. The electrical breakdowns are events in which the insulating proprieties of a typically electrically insulating medium are weakened due to the presence of high electrical fields. One of the best insulating mediums is the ultra high vacuum because there are no molecules that will ionize and that will conduct the electricity. But even in vacuum, there will be electrical breakdowns. They are called vacuum arc breakdowns. The conducting medium in this case is given by the ions and the electrons emitted from the metal surface of the electrodes that create the high electrical fields.  It has been observed that applying repeatedly high electrical fields on the surface of the electrodes reduces the number of breakdowns. This process is called conditioning. One explanation is that the large electric fields create dislocations near the surface of the metal that reduce the probability of having new vacuum arc breakdowns. These dislocations should also increase the electrical resistivity of the metal near its surface. To test if new dislocations are formed during conditioning, precise measurements of the surface resistivity are needed. These measurements will be made with radio pulses in the GHz range. In this range of frequencies, the electromagnetic fields penetrate only a few microns inside the surface of the metal and it will be possible to measure only the resistivity of the metal near its surface. The surface resistivity data is encoded in the quality factor (Q-factor) of a resonant cavity. This parameter describes how fast the energy is dissipated inside the cavity. A larger surface resistivity leads to a larger dissipation of energy in the walls of the cavity and to a lower Q-factor. It is advantageous to perform the measurements in cryogenic conditions because the increase in resistivity due to the formation of dislocations is much more pronounced at very low temperatures. The measurements are planned for the discharge system available in FREIA laboratory, that consists of two electrodes, separated by a small gap (60 µm), and placed inside a cryostat cooled with liquid helium. In this thesis, I describe the algorithms used to extract the Q-factor from experimental data and the results of some experiments done using the electrodes and test cavities. Small changes in resistivity (less than 0.6%), induced by temperature changes, were measured. The final chapter explores the results of the 3D EM simulations, where the electrode system in the cryogenic setup in FREIA laboratory is modified to act as a resonant cavity.

Att få en fördjupad bild av energiförlusten när joner med olika initialenergier interagerar med diverse material kan lägga grunden till viktig forskning inom till exempel materialvetenskap och strålbehandling. Det här projektet gick ut på att utföra flygtidsmätningar för att bestämma energiförlust för accelererade jod och vanadinjoner med energier mellan 4 och 44 MeV vid passage genom tunna fristående filmer av aluminium och titan. För att framställa tunna filmer sputtras material på en saltbelagd glasskiva som därefter sänks ner i vatten så saltet löses upp och filmen kan fiskas upp på en hållare. I en accelerator bombarderas folierna med joner och flygtiden mäts i en flygtidsdetektor. Skillnaden mellan de flygtider som mätts med och utan en folie kan sedan kalibreras om till energiförlust. Vid analys av filmernas tjocklek visade sig, framförallt för titanfilmerna, föroreningar och ojämnheter bidra till felkällor och påverka resultatet. Resultatet följer tidigare forskning väl vilket ger metoden merit men med vissa avvikelser som antas bero på felanpassad mätdata.

Vid underhållsarbeten av trafikerade tunnlar stängs trafiken av. Därav sker dessa arbeten oftast nattetid. För att kunna släppa på trafiken igen så snabbt som möjligt eftersträvas effektiva förstärkningsarbeten. Av säkerhetsskäl kan utökade hållfasthetskrav förekomma för sprutbetong som förstärkningsmetod. Om betongen hinner uppnå det krav som ställs för hållfastheten snabbare kan antal nätter som tillägnas förstärkningsarbeten reduceras. Detta examensarbete ska undersöka hur olika tillsatser av typen acceleratorer kan påskynda den tidiga hållfasthetsutvecklingen för sprutbetong. Utav de acceleratorer som utreds ska en slutsats kunna dras om dessa typer av tillsatser lämpar sig för förstärkningsmetoden våt sprutbetong. För att utreda acceleratorernas påverkan på sprutbetong har fullskaliga tester utförts. Vid testning sprutades olika betongrecept i testlådor. På lådorna kunde sedan hållfasthetstester utföras enligt gällande standarder. Testerna undersöker endast betongens tidiga hållfasthet, vilket blir en av arbetets avgränsningar. Resultatet av testerna visas i form av grafer och diagram. Därefter diskuteras metodernas osäkerhet och hur skiljande parametrar påverkar resultatet. Ur graferna kan en positiv effekt utläsas för recepten med tillsatt hållfasthetsaccelerator jämfört med recepten där endast sprutbetongaccelerator användes. Den positiva trenden syns tydligast inom de första fyra timmarna, efter detta framträder osäkerheten i mätvärdena. Slutsatser om acceleratorernas verkan för hela testet kan inte dras utan en statistisk hypotesprövning mellan de olika recepten. En sådan prövning utesluter om det statistiskt går att skilja resultaten åt. Dessutom rekommenderas företaget utföra mindre kompletterande tester på provkroppar i laborativ miljö, där skiljande parametrar kan elimineras och säkrare utdata erhållas. / During maintenance work in trafficked tunnels, the traffic must be halted. Therefore, such efforts often take place night-time. In order to enable a quick release of traffic again, it is crucial to have an effective reinforcement work. Due to the safety risks of using shotcrete as a reinforce method, there is a chance of adding additional strength-requirement can exist due to safety risks. If the concrete achieves the strength requirements sooner than expected, the number of nights dedicated to maintenance work can be reduced. This study intends to investigate how different types of admixtures, so called accelerators, can expedite the shotcrete’s initial strength development. Furthermore, the study will include a conclusion of the suitability for the accelerators that have been applied in the shotcrete. To investigate the effects of these accelerators, extensive tests has taken place. During these tests, shotcretes with different recipes were sprinkled into test boxes. Thereafter, tests of strength development could be performed on these boxes in agreement with prevailing standards. To delimitate the study, the selected methods only show the early strength-development of shotcrete. The results from these tests will be presented in graphs. Uncertainties regarding measurement data and how separated physical parameters affect the test results will be discussed as well. By reading the data presented in the graphs, a positive development can be identified in recipes with added hardening accelerators compared to recipes containing only shotcrete accelerators within the first four hours. Following the first four hours, a significant uncertainty in measurements will be noticed. Finally, due to high irregularity in measured values, conclusions of the accelerators’ effect cannot be confirmed solely by the results from these tests. Therefore, a hypothesis trial is necessary as it would exclude if the recipes statically can be separated. Furthermore, the company recommends performing additional small-scale tests in a laboratory environment. Through laboratory tests, a more certain result can be received.

<p>Presentation held over Zoom.</p>

This project was concerned with the analysis and development of a decanter centrifuge. The aim of the project was to increase the understanding of the operation of the machine, and identify and implement methods of improving the performance. A comprehensive breakdown of the power consumption of a GTech-Bellmor 1456 Centrifuge Decanter was completed. There are four components of the power consumption in a decanter centrifuge: friction during product transport, viscous and kinetic losses during feed acceleration, inefficiencies in power transmission components, and aerodynamic losses, known as windage. A mathematical model was developed to predict the power, torque, and axial force required by product transport. A relationship for the power consumed during feed acceleration was derived from first principles. The power transmission losses are comprised of inefficiencies in the motors, belt drives, gearbox, bearings, and seals; each of these was quantified. The windage has two components: the surface drag on the bowl as it rotates in an annular space and the pressure drag on external protrusions. The windage was predicted empirically and computationally. Methods that were identified for improving the decanter centrifuge were: reduce the mass of bowl and scroll, improve wear resistance, reduce the coefficient of friction of the bowl wall and scroll faces, optimise scroll geometry, redesign the feed accelerator to increase acceleration efficiency, implement control of the bowl speed, differential speed, and pool depth, and recess the bolt heads on the bowl and cover the third phase ports. An analysis of several worn centrifuges revealed that the majority of the wear occurs on the scroll, bowl wall, accelerator, and solids discharge ports. An experiment was developed to recreate the wear conditions inside a centrifuge. A high pressure abrasive film was forced between materials moving relative to each other. Similar results were observed for acetel, UHMWPE, and 316 stainless steel when using a pin-on-disk wear test rig. A new composite bowl was developed for two main reasons, weight reduction, and improved wear and friction characteristics. The full design process was applied to the bowl and several concepts were generated for a new scroll. The design of the bowl included conceptual design, material selection, material testing, constructing scale models, and the manufacture of a full-size bowl for a GTech-Bellmor 1456 Centrifuge Decanter. The potential for using composite materials in decanter centrifuges was demonstrated. The manufacturing method developed during this project was novel and produced parts suitable for use in high-speed rotating machinery. The feed accelerator analysis consisted of three components: theoretical, experimental, and computational analysis. Three feed acceleration mechanisms were identified: viscous dissipation, impulse force, and mass flow induced velocity. An experimental method was developed to examine decanter centrifuge feed accelerator designs. The method allowed for the measurement of efficiency and high-speed photography of the flow between the accelerator and the rotating pool. The order of best to worst performing of the six tested designs was Modified Disk, Disk, Plate, Conical, Drum, and Esbjerg. The feed accelerator was modelled using ANSYS-CFX 14.5 and compared to the experimental results. There was excellent agreement between the flow in the annular space observed using high-speed photography and the paths predicted using the computational model. A parametric study of the Drum and Disk feed accelerator designs was undertaken using the computational model. It was found that increasing the surface area of the port faces of the Drum accelerator and increasing the discharge angle and discharge radius for the Disk accelerator improved the performance.

No description available.

新創加速器主要功能取向為Mentoring、Funding、Networking。以創業加速器而在今日創業團隊的發展中扮演了重要角色。各創業加速器各自有一套運作的模式，但整體而言，它們能為創業者提供全球性的事業網絡、優秀的Mentor、紮實的創業訓練、工作的空間、創業團隊組合，以及可以曝光的場合。新創加速器主要的目的推動新創事業快速成長，提高企業價值。 全球加速器網絡(GAN)統計全球加速器集中在北美，而產業的成長在亞洲，表示在亞洲的新創加速器仍有相當大的成長空間。 國際加速器串聯形成網絡時，網絡內因連結豐厚的創業資金與產業關係，可協助新創公司的營運快速發展；而加速器間也建立優質個案分享的機制與管道，能促使有潛力的新創企業更快取得市場發展的必要資源，以致高成長中小企業可透過進入國際市場策略，以達到加速營收成長及擴大營運據點的成效。 市場上評斷商業加速器成功與否，募資與對加速計畫中企業是否引入股權投資以及其投資回報、財務活動、網絡關係、出場機制的設計是否符合期望，皆是相當 關鍵的衡量指標，亦是加速器之主要功能與核心要點。 全球加速器趨勢朝向專業化、亞洲成長及資源聯結功能強化等趨勢。。加速器未來的發展朝向加速器差別化發展，亦著重Valuation價值提昇在資本市場的重要性。未來在大企業型的定向培育、天使投資合作將有更密切合作。新創企業的經營與出場策略將更靈活，而已穩定經營企業的成長轉型，都將與加速器平台緊密結合。

The International Linear Collider (ILC) aims to collide electrons and positrons with a centre of mass energy of 500GeV and a luminosity of 2×10³⁴ cm⁻² s⁻¹. To achieve this luminosity, the nominal final emittance of the electron and positron beams have to be below 10μm.rad horizontally and 0.04&mu;m.rad vertically. To prevent the emittance from becoming too large, the main linacs will require alignment at an unprecedented level. The ILC main linacs will be aligned with respect to a reference network which runs along the entire length of the tunnel. The Linear Collider Alignment and Survey (LiCAS) Rapid Tunnel Reference Surveyor (RTRS) is the prototype of a device proposed to survey the ILC reference network. The LiCAS RTRS has several measurement systems; its Frequency Scanning Interferometry (FSI) measurement system is studied in this thesis. The FSI system has three distinct sub-systems: the reference interferometers, the external FSI measurement system and the internal FSI measurement system. The errors on the length of the reference interferometers are shown to be of the order of 1.1μm (0.3ppm). The external FSI measurement system is shown to measure distances close to 0.42m with errors of &pm;1.9&mu;m stat &pm;0.16&mu;m syst and the internal FSI measurement system is shown to measure distances close to 4.2m with errors of &pm;0.24&mu;m stat &pm;1.6&mu;m syst. A survey of the ILC reference network using laser trackers is simulated without taking account of systematic measurement errors from refraction in the tunnel air. The simulated networks are used to misalign the simulated accelerators in Dispersion Matched Steering (DMS) simulations. The DMS simulations show that only 30% of the simulated accelerators produce an acceptable final corrected vertical emittance. It is further shown that the introduction of long range distance measurements between primary reference markers (PRMs) using GPS, reduces the long range error growth in the network, and that 95% of simulated accelerators give acceptable performance. A simplified network simulation model, which is capable of simulating reference networks surveyed by conventional and novel devices, is produced and compares favorably to full simulations.