As a cutting-edge technology for photoinjectors, SRF guns are expected to provide CW electron beams with high bunch charge and low emittance, which is critical to the development of future FELs, ERLs and 4th/5th generation light sources. However, existing research has not explored the full potential of SRF guns as predicted by theory. Currently, the research activities at ELBE focus on solving technological challenges of a 3.5 cell SRF gun as well as applying it to high-bunch-charge experiments. This thesis aims to optimize the ELBE SRF gun and the relevant beam transport for future high-bunch-charge applications at pELBE, nELBE, TELBE and CBS experimental stations. Chapter 1 describes the demands of these applications on the SRF gun in detail. Chapter 2 outlines the development of a simulation tool based on ASTRA and Elegant, followed by the optimized gun parameters and the beam transport for the four experimental stations. Chapter 3 introduces beam diagnostic methods and data processing applied in this thesis. Chapter 4 presents results of experiments, including the pulse length measurement of the UV laser for generating electrons from the photcathode, the commissioning of ELBE SRF Gun II, a verification experiment on the LSC effect conducted at PITZ and a beam transport experiment with the bunch charge of 200 pC. Simulation results have determined the effect of each SRF gun parameter on the beam quality and have provided optimized settings according to the requirements in Chapter 1. Experimentally, the LSC effect was confirmed at PITZ, in agreement with simulations which indicated that LSC significantly influences beam quality. The performance of ELBE SRF Gun II was improved and a beam with a bunch charge of 200 pC and an emittance of 7.7 μm from ELBE SRF Gun II has been transported through ELBE without visible beam loss. The development of the simulation tool and beam diagnostics will serve further research at ELBE. Results of both simulations and experiments enrich the understanding of the existing SRF gun as well as the ELBE beamline and will guide continuing improvements. Already, ELBE SRF Gun II can deliver twice the bunch charge and lower emittance compared to the thermionic injector routinely used for ELBE. Ongoing modifications and development of the gun-cavity and photocathodes are expected to provide still further improvements. Progress on high-bunch-charge experiments at ELBE can be expected by applying the SRF gun.

Penetrating brain injury resulting from nail-gun use is a well-characterized entity, one that is increasing in frequency as nail guns become more powerful and more readily available to the public. We present a case and offer management strategies for a 50-year-old male with two intracranial penetrating nail gun injuries. Nail gun brain injuries are commonly intentionally self-inflicted. Suicide should be considered when straight nails cause wounds to the chest, head, or abdomen. The primary preoperative concern is formation of a traumatic pseudoaneurism, which prompts both preoperative and follow-up cerebral angiography. Surgery for combined intracranial and extracranial injury may require the collaborative expertise of colleagues from the fields of ophthalmology, otolaryngology, and oral maxillofacial surgery. A rational management strategy should permit these patients to be discharged with no additional injury.

Gun violence is a pandemic problem in the United States, resulting in over two thirds of all homicides each year. Consequently, gun related policies have been fiercely debated within the political spectrum, with the 20th century seeing a dramatic increase in gun control legislation. Gun-free zones are designated areas that strictly prohibit all private citizens from carrying a firearm, even those with concealed weapon permits. The statistics indicate that numerous instances of gun related mass shootings have occurred within the confines of these gun-free zones (schools, movie theatres, government installations, etc.). However, little research exists to understand whether citizens actually feel any safer when they are in a gun-free zone. The purpose of this study was to explore citizens’ perceptions about gun control policies, specifically about using gun-free zones, who resided in the five states with the highest rates of gun violence per capitain descending order, these included Virginia, Florida, Texas, Nevada, and Connecticut. Moreover, these five states were the locations of the top five deadliest mass shootings in U.S. history to date. The researcher also discovered how residents felt about pro-gun areas, where responsible citizens could legally carry firearms, as well as determine whether gun-free zones influenced their likelihood of visiting a prescribed location. Finally, the study sought to understand residents’ perceptions regarding using gun-free zones pertaining to their impact on reducing incidents of mass shootings. The researcher filled the gap in the literature regarding knowledge pertaining to citizens’ perceptions about using specific gun control measures, such as gun-free zones, and the influence that the historical evidence had on their perceptions. The answer to RQ1 (do residents associate using gun-free zones with feelings of safety or feelings of concern?) was that participants were twice as likely to associate using gun-free zones with feelings of concern rather than feelings of safety. The answer to the first part of RQ2 (whether participants believed that gun-free zones reduced gun-related violence) was no, based on a 2-to-1 ratio. Responses to the impact of gun control measures on reducing gun violence were closely matched to perceptions of the role of gun-free zones in reducing gun violence. The answer to the second part of RQ2 (do residents believe that gun-free zones lower the occurrences of mass shooting incidents?) was no, again based on a 2-to-1 ratio. The answer to the third and final part of RQ2 (whether participants’ perceptions correlated to the historical/empirical evidence of the location of mass shootings as primarily inside of or outside of gun-free zones) was yes for participants from Florida, Texas, Nevada, and Connecticut and no for participants from Virginia.

The thesis deals with numerical simulations of a hairpin thermionic electron gun, an electron source of the electron-beam welding machine. Simulations showed that the space charge in the electron gun has a significant influence on the beam current and electron trajectories. Simulation outputs are in a sufficient agreement with the experimental measurements.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第21472号 / エネ博第377号 / 新制||エネ||74(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)准教授 増田 開, 教授 長﨑 百伸, 教授 大垣 英明 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

No description available.

This paper addresses the pressing problem of the surge in crime in Sweden, which has led to substantial uncertainty about its underlying causes. By investigating the correlation between socio-economic factors and crime on a municipality level from 2015 to 2020, we aim to provide valuable insights into understanding and effectively tackling this issue. Specifically, we examine the role of male immigrants, income, education level, and population density, contributing to the field of economics by shedding light on potential economic policies that can effectively reduce overall crime rates. Additionally, we focus on gun violence, considering Sweden's notorious reputation in recent years, to comprehensively analyze the relationship between these factors and crime. Our empirical analysis, employing the Fixed Effects Model and Pearson Correlation Matrix, explores these connections, revealing both inconclusive evidence regarding the link between immigration and crime and ambiguous conclusions for the remaining independent variables. These findings have important implications for policymakers striving to address the urgent problem of rising crime in Sweden.

In the last half century, gun ownership has been one of the most hotly debated topics in the United States. The right to bear arms was written into the U. S. Constitution and into the hearts and minds of its citizens. During the last half century, however, numerous gun control laws have been enacted at Federal, state and local levels, and it can be argued (plausibly or not) that part of the legislative intent has been to decrease the number of gun owning households in the United States. For many decades, this number hovered at one half of all households (Wright, 1995). The possible success of these gun control efforts is suggested by an apparent and rather sharp decline in the ownership percentage beginning in the 1990s. In 2000, the household gun ownership rate had decreased to 32.5% (according to the General Social Survey). The question raised in this thesis is how to account for declining gun ownership. More specifically, I ask if there has in fact been a decline in ownership, or whether the apparent decline is an illusion resulting from changing demographics. A third possibility, that social norms have changed such that admitting gun ownership in surveys is now more problematic for many people, is also considered and seems, indeed, to be the most telling line of explanation.

This thesis derives working expressions from electromagnetic physical laws to gain a deeper understanding of the nature of railguns. The expressions are refined for ease of use and then compared to electromagnetic simulators that solve complex equations that arise from different rail geometry. Further simplifications lead to an expression for the final velocity of the projectile and showcase the importance of the system resistance to projectile flux gain ratio. A Simulink simulation then incorporates the resulting non-linear differential equations and approximates the projectile velocity over time based on physical dimensions and material properties. Some equations derived can be found in literature regarding the subject but often lack explanation. This work is intended to provide a thorough derivation of all the relative constituent relations between the critical characteristics of the gun such as the strength of the forces acting on the rail and projectile, rail current, and initial velocity of the projectile. This makes it easier to identify what influences acceleration of the projectile, how much bracing each rail needs, how much initial velocity to give the projectile, etc. Design options discussed besides the standard design include the augmented rail system, a magnetic shell design, and a “wrap around” design. The tradeoffs encountered in each design are discussed in length. Due to the lack of a sufficient power source during testing the projectile was unable to travel down the length of the rails due to metal binding, insufficient pulse duration, and too much circuit resistance. It was found that using copper tungsten for the rails ensures that the rails can withstand the arcing inflicted by the kilo-Ampere current along the rails very well compared to other materials. Also, the copper in the tungsten alloy ensures high conductivity while the tungsten provides structural integrity to the rails during arcing between them and the projectile. Frequency response of conductive projectiles is characterized and improvements such as laminated projectiles are suggested as solutions to mitigate eddy currents induced in the projectile and improve performance.

This dissertation examines how relatives of gun-violence victims, specifically Black women, move about their environments in the aftermath of sudden and tragic loss. I explore the following research questions: 1) How do Black women, who are co-victims of gun homicide, navigate spaces of trauma? 2) How does the experience of trauma extend into other spaces and spatialities of their lives? 3) What are the social, political, and health implications for Black women with limited mobility who are co-victims of gun homicide? This study draws on a literature synthesis on health geographies, geotrauma, and Black Feminist Geographies, as well as auto-methods, specifically a Black Feminist auto-ethnography (BFA). BFA involves analyzing your own experiences in relation to others in their family and community. My autoethnography of my lived experiences in the neighborhood I grew up in started with the observation of my mother in the aftermath of losing my brother to gun violence in 2012. My dissertation develops a research agenda to theorize how racism, poverty, and trauma compound and how Black women craft survival strategies as they navigate landscapes of trauma. I describe the ways that conventional approaches to understanding gun violence can overlook the layers of trauma and fail to capture the nuances or lived experience of being a co-victim of gun violence. I propose BFA to center and understand the lived experience of co-victims of gun violence and to bear witness to the ways we engage with the world around us while processing the trauma that is carried with us. My autoethnography uncovers key strategies my mother and I used to cope with our loss, especially in the face of institutional failures from the policy. This research points towards a need for better mental health resources for co-victims of gun violence as they process their grief. / Geography