The GALATEA test facility and a first study of alpha-induced surface events in a Germanium detector

Germanium detectors are a choice technology in fundamental research. They are suitable for the search for rare events due to their high sensitivity and excellent energy resolution. As an example, the GERDA (GERmanium Detector Array) experiment searching for neutrinoless double beta decay is described. The observation of this decay would resolve the fundamental question whether the neutrino is its own antiparticle. Especially adapted detector technologies and low background rates needed to detect very rare events such as neutrinoless double beta decays are discussed. The identification of backgrounds originating from the interaction of radiation, especially alpha-particles, is a focus of this thesis. Low background experiments face problems from alpha-particles due to unavoidable surface contaminations of the germanium detectors. The segmentation of detectors is used to obtain information about the special characteristics of selected events. The high precision test stand GALATEA was especially designed for surface scans of germanium detectors. As part of this work, GALATEA was completed and commissioned. The final commissioning required major upgrades of the original design which are described in detail. Collimator studies with two commercial germanium detectors are presented. Different collimation levels for a beta-source were investigated and crystal axis effects were examined. The first scan with an alpha-source of the passivated end-plate of a special 19-fold segmented prototype detector mounted in GALATEA is described. The alpha-induced surface events were studied and characterized. Crosstalk and mirror pulses seen in the segments of the germanium detector were analyzed. The detector studies presented in this thesis will help to further improve the design of germanium detectors for low background experiments.Germaniumdetektoren eignen sich für die Suche nach sehr seltenen Ereignissen, da sie aufgrund ihrer hohen Sensitivität und hervorragenden Energieauflösung geringe Mengen von Radioaktivität nachweisen können. Germaniumdetektoren finden daher zum Beispiel Anwendung beim GERDA (GERmanium Detector Array) Experiment, welches sich mit der Suche nach dem neutrinolosen doppelten Betazerfall beschäftigt. Die Beobachtung dieses Zerfalls würde die fundamentale Frage beantworten, ob das Neutrino sein eigenes Antiteilchen ist. Die experimentelle Voraussetzung zum Nachweis von sehr seltenen Ereignissen wie dem neutrinolosen doppelten Betazerfall sind niedrige Untergrundraten und speziell angepasste Detektortechnologien. Das GERDA Experiment sowie Methoden zur Untergrundminimierung werden vorgestellt. Unvermeidbare Oberflächenkontaminationen von Germaniumdetektoren erzeugen einen zusätzlichen intrinsischen Untergrund. Im Besonderen werden Oberflächenereignisse, die durch die Wechselwirkung von alpha-Teilchen, entstehen im Rahmen dieser Arbeit diskutiert. Eine spezielle Segmentierung der Detektoren liefert zusätzliche Informationen zur Unterscheidung von Signal und Untergrundereignissen. Ein eigens zur Untersuchung von Oberflächenereignissen entwickelter Hochpräzisionsteststand, GALATEA, wurde im Rahmen dieser Arbeit vollständig in Betrieb genommen. Die Inbetriebnahme der Apparatur erforderte umfangreiche Umbaumaßnahmen und die Implementierung zusätzlicher Komponenten. In der Vorbereitung wurden auch Kollimatorstudien an zwei kommerziellen Germaniumdetektoren durchgeführt. Das Kollimationsverhalten sowie Kristallachseneffekte wurden untersucht. Die Oberfläche eines speziell 19-fach segmentierten Prototyp-Detektors wurde erstmalig in GALATEA mit einer alpha-Quelle abgetastet. Oberflächennahe Ereignisse wurden untersucht und charakterisiert. Die hier vorgestellten Detektorstudien dienen der Untersuchung und Charakterisierung von Germaniumdetektoren. Die daraus gewonnenen Resultate können nützlich für die Identifizierung von Untergrundereignissen im GERDA Experiment sein oder generell Anwendung in Experimenten finden, die Germaniumdetektoren verwenden

The GALATEA test facility and a first study of alpha-induced surface events in a Germanium detector

Germanium detectors are a choice technology in fundamental research. They are suitable for the search for rare events due to their high sensitivity and excellent energy resolution. As an example, the GERDA (GERmanium Detector Array) experiment searching for neutrinoless double beta decay is described. The observation of this decay would resolve the fundamental question whether the neutrino is its own antiparticle. Especially adapted detector technologies and low background rates needed to detect very rare events such as neutrinoless double beta decays are discussed. The identification of backgrounds originating from the interaction of radiation, especially alpha-particles, is a focus of this thesis. Low background experiments face problems from alpha-particles due to unavoidable surface contaminations of the germanium detectors. The segmentation of detectors is used to obtain information about the special characteristics of selected events. The high precision test stand GALATEA was especially designed for surface scans of germanium detectors. As part of this work, GALATEA was completed and commissioned. The final commissioning required major upgrades of the original design which are described in detail. Collimator studies with two commercial germanium detectors are presented. Different collimation levels for a beta-source were investigated and crystal axis effects were examined. The first scan with an alpha-source of the passivated end-plate of a special 19-fold segmented prototype detector mounted in GALATEA is described. The alpha-induced surface events were studied and characterized. Crosstalk and mirror pulses seen in the segments of the germanium detector were analyzed. The detector studies presented in this thesis will help to further improve the design of germanium detectors for low background experiments.Germaniumdetektoren eignen sich für die Suche nach sehr seltenen Ereignissen, da sie aufgrund ihrer hohen Sensitivität und hervorragenden Energieauflösung geringe Mengen von Radioaktivität nachweisen können. Germaniumdetektoren finden daher zum Beispiel Anwendung beim GERDA (GERmanium Detector Array) Experiment, welches sich mit der Suche nach dem neutrinolosen doppelten Betazerfall beschäftigt. Die Beobachtung dieses Zerfalls würde die fundamentale Frage beantworten, ob das Neutrino sein eigenes Antiteilchen ist. Die experimentelle Voraussetzung zum Nachweis von sehr seltenen Ereignissen wie dem neutrinolosen doppelten Betazerfall sind niedrige Untergrundraten und speziell angepasste Detektortechnologien. Das GERDA Experiment sowie Methoden zur Untergrundminimierung werden vorgestellt. Unvermeidbare Oberflächenkontaminationen von Germaniumdetektoren erzeugen einen zusätzlichen intrinsischen Untergrund. Im Besonderen werden Oberflächenereignisse, die durch die Wechselwirkung von alpha-Teilchen, entstehen im Rahmen dieser Arbeit diskutiert. Eine spezielle Segmentierung der Detektoren liefert zusätzliche Informationen zur Unterscheidung von Signal und Untergrundereignissen. Ein eigens zur Untersuchung von Oberflächenereignissen entwickelter Hochpräzisionsteststand, GALATEA, wurde im Rahmen dieser Arbeit vollständig in Betrieb genommen. Die Inbetriebnahme der Apparatur erforderte umfangreiche Umbaumaßnahmen und die Implementierung zusätzlicher Komponenten. In der Vorbereitung wurden auch Kollimatorstudien an zwei kommerziellen Germaniumdetektoren durchgeführt. Das Kollimationsverhalten sowie Kristallachseneffekte wurden untersucht. Die Oberfläche eines speziell 19-fach segmentierten Prototyp-Detektors wurde erstmalig in GALATEA mit einer alpha-Quelle abgetastet. Oberflächennahe Ereignisse wurden untersucht und charakterisiert. Die hier vorgestellten Detektorstudien dienen der Untersuchung und Charakterisierung von Germaniumdetektoren. Die daraus gewonnenen Resultate können nützlich für die Identifizierung von Untergrundereignissen im GERDA Experiment sein oder generell Anwendung in Experimenten finden, die Germaniumdetektoren verwenden

Latino Police Officers: Negotiating the Police Role

Tension and mistrust have characterized relations between the police and Latino communities. Civil rights leaders and community groups argue that increased employment of Latino police officers will improve the quality of police services, based on the assumption that Latino officers will be better able to relate to Latino community members and will not engage in discriminatory behavior. This assumption presupposes that Latinos are a relatively homogenous group, readily encompassed by clear ethnic boundaries and a shared sense of ethnic identity. In addition to presupposing a unidimensional “Latino” identity, it also presumes that Latino police officers share a common vision of their police role in the Latino community stemming from this shared sense of ethnic identity. This may, however, be far from a straight forward relationship. The growing Latino population is much more heterogeneous than in past decades. Latino police officers, who are primarily second and third generation middle-class citizens are now policing a Latino population that is increasingly diversified by country of origin, social class background, length of residence in the United States, educational and language skill levels, and other social and human capital variables. This study of Latino police officers examines public policy assumptions that Latinos are a homogenous ethnic group, and the related assumption that Latino police officers share a common vision of their role in the Latino community, one that is more supportive of and better qualified to meet the needs of the Latino community. Through systematic, in-depth interviews with the complete population (100%) of sworn Latino officers in Omaha, NE (N=34), I investigate the officers’ attitudes regarding their ethnic identification and their experiences policing in a diverse Latino community. By illustrating various degrees of identification with the ethnic minority group as well as various degrees of identification with the Anglo majority, I delineate three general ethnic identity patterns expressed by the officers. I also examine socio‐demographic factors relevant to identity formation and assess their explanatory value. Second, I investigate whether officers who identify with the Latino community do have, as policy predicts, more empathic and supportive attitudes. Two general approaches to policing in the Latino community are profiled. Implications are discussed

Crisis Communications in a Natural Agricultural Disaster

Wildfires in Texas, Oklahoma, and Kansas in the late 2010s caused seven deaths and catastrophic damage to millions of acres of ranch and farmland. Because of the rural location of these disasters, agricultural communicators were releasing information to media, internal stakeholders, social media, and other agricultural audiences. The purpose of this study was to explore the communications efforts made and subsequent lessons learned from agricultural communicators during the fires. Through a qualitative case study, researchers interviewed 14 agricultural communicators about their experiences in disseminating information about the fires. Most of the findings align with pre-existing literature; however the researchers found that communicators should be prepared to develop a system to communicate about and accept donations, develop a network of organizations that can be supportive in a crisis situation, and let people be the subject of the messaging. The data also indicate that an undergraduate course in crisis communications would be beneficial

See You On TV: A Phenomenology of Careers on Extension Television in Oklahoma

Extension specialists are under increasing pressure to interact with audiences through emerging digital media including video. In an effort to understand how such interactions affect the careers of engaged specialists, this study seeks to explore the career effects on Extension subject-matter specialists that resulted from long-term, regular participation in an Extension television effort. Using Cultivation theory and source credibility as a lens, a qualitative phenomenology was conducted by interviewing individuals who have contributed to one such program on a weekly or bi-weekly program for multiple decades. Participants reported improved career effectiveness via increased credibility in face to face communications as well as enhanced communication when broadcast messages were seen as a continuation of in-person communications. Early career advancement was said to have resulted in spite of broadcast participation rather than as a result of participation, however, administrative attitudes toward broadcast have shifted in favor of such efforts

Are We There Yet? Toward an Agricultural Communications Academic Organization

As agricultural communications has grown and evolved since its origins more than 100 years ago, the future directions of the discipline related to teaching, research, and as a professional organization are discussed with a challenge to the members of the profession to be engaged in future discussions and decisions

Agri-Science Faculty Perceptions of Communication Activities at Texas Tech University, a Non-Land-Grant Institution

Due to the direct impact science has on society, it is important for scientists to communicate with the general public (Rose et al., 2020). There are various means of communication that scientists may choose to disseminate their research. Recently, Bowman et al. (2018) assessed how often Extension personnel at a land-grant institution used various communication skills, how important they perceived each skill to be, and how comfortable they were performing them. Land-grant institutions have different communication expectations for their faculty than those at non-land-grant institutions. Therefore, this study focused on the Use, Comfort, and Importance of communication skills according to faculty members at a non-land-grant university. Survey data were collected from 57 (N = 57) faculty members at Texas Tech University, a non-land-grant institution, within its College of Agricultural Sciences and Natural Resources. Average Use, Comfort, and Importance scores were calculated for each communication skill and categorized as high, average, or low. These scores indicated whether the faculty members at this non-land-grant institution had adopted each communication skill according to Rogers’ Innovation Diffusion Process

Salmonella and the Media: A Comparative Analysis of Coverage of the 2008 Salmonella Outbreak in Jalapenos and the 2009 Salmonella Outbreak in Peanut Products

The purpose of this study was to catalog and compare data from the coverage of two different Salmonella outbreak events in the United States through the lens of framing theory. Using qualitative content analysis, the transcripts of television newscasts that covered the 2008 Salmonella outbreak in tomatoes and jalapenos and the 2009 Salmonella outbreak in peanut products were researched and analyzed. These transcripts were taken from ABC, CBS, NBC, and CNN for both outbreaks. The researchers determined that while the manner in which the stories were framed was similar in some respects, such as story presentation and attitudes, there were also differences, particularly in regard to interview sources used. Tomato growers were used as sources in the 2008 outbreak, but peanut farmers were not used in the 2009 outbreak, where victims and politicians were favored. However, it was determined this had no overall effect on the accuracy, fairness, or overall economic or social impact of the stories presented

Postsecondary Students\u27 Reactions to Agricultural Documentaries: A Qualitative Analysis

Prior studies have found that television and movie portrayals of science and agriculture can influence attitudes and opinions toward the featured topic or issue. The prevalence of media in modern society emphasizes the need to better understand the possible impact representations of agriculture in entertainment media have on audience members’ attitudes. The purpose of this study was to explore the influence two agricultural documentaries (Food, Inc. and King Corn) had on students’ perceptions of agriculture. Students enrolled in two agricultural communications classes at a southwest university watched one documentary per class, and through reflective journaling, recorded their thoughts about the documentaries. These journals were then analyzed to determine dominant themes and key quotes. Overall, students stated they were upset and offended by the messages presented and sources used in each documentary. Although some students found both documentaries to contain interesting information, for the most part, they found the films to be one-sided and did not portray an accurate depiction of modern agricultural practices. The use of reflective journaling was effective because it allowed all students to provide their viewpoints in response to the films. It also allowed the students to practice writing response statements as some will work in public relations and may be expected to defend their industry should other negative documentaries about agriculture be produced in the future. Additional research should further examine the effectiveness of reflective journaling and gather student perceptions to other films or television shows that feature agriculture