Mass Measurements of Exotic Ions in the Heavy Mass Region for Nuclear Structure Studies at ISOLTRAP

The mass is a unique fingerprint of each nucleus as it reflects the sum of all interactions within it. Comparing experimental mass values with theoretical calculations provides an important benchmark of how well the role of these interactions is already understood. By investigating differences of experimental binding energies, such as two-neutron separation energies (S2n), valuable indications for nuclear-structure studies are provided. The present thesis contributes to these studies providing new high-precision mass measurements especially in the heavy-mass region. Here, nuclear theory is heavily challenged due to the large number of nucleons. The data have been obtained at the Penning-trap mass spectrometer ISOLTRAP located at the radioactive-ion-beam facility Isolde at CERN. For the determination of the masses, the time-of-flight ion-cyclotron-resonance technique has been applied. While the new mass data for 122−124Ag continue existing trends in the S2n energies, the new mass values for 207,208Fr render them more precisely. In the case of the mass values for 184,186,190,193−195Tl a new interesting odd-even effect has been revealed. The comparison of the measured mass values with theoretical models furthermore demonstrates significant problems in reproducing the strength of the pairing correctly. This is of special interest for the discussion about shape coexistence in the region around the doubly-magic 208Pb

Effects of space charge on the mass purification in Penning traps

The influence of space charge on the mass selection of ions stored in a Penning trap was investigated with the ISOLTRAP experiment at CERN/ISOLDE. A mixture of 85,87Rb +  ions has been used to probe the change of the experimental parameters, e.g. frequencies and amplitudes of the radiofrequency excitations, as a function of the number of ions present in the tra

Habitat models to predict wetland bird occupancy influenced by scale, anthropogenic disturbance, and imperfect detection

Understanding species-habitat relationships for endangered species is critical for their conservation. However, many studies have limited value for conservation because they fail to account for habitat associations at multiple spatial scales, anthropogenic variables, and imperfect detection. We addressed these three limitations by developing models for an endangered wetland bird, Yuma Ridgway's rail (Rallus obsoletus yumanensis), that examined how the spatial scale of environmental variables, inclusion of anthropogenic disturbance variables, and accounting for imperfect detection in validation data influenced model performance. These models identified associations between environmental variables and occupancy. We used bird survey and spatial environmental data at 2473 locations throughout the species' U.S. range to create and validate occupancy models and produce predictive maps of occupancy. We compared habitat-based models at three spatial scales (100, 224, and 500 m radii buffers) with and without anthropogenic disturbance variables using validation data adjusted for imperfect detection and an unadjusted validation dataset that ignored imperfect detection. The inclusion of anthropogenic disturbance variables improved the performance of habitat models at all three spatial scales, and the 224-m-scale model performed best. All models exhibited greater predictive ability when imperfect detection was incorporated into validation data. Yuma Ridgway's rail occupancy was negatively associated with ephemeral and slow-moving riverine features and high-intensity anthropogenic development, and positively associated with emergent vegetation, agriculture, and low-intensity development. Our modeling approach accounts for common limitations in modeling species-habitat relationships and creating predictive maps of occupancy probability and, therefore, provides a useful framework for other species.Department of Defense Legacy Program [W9132T-12-2-0026]; Gap Analysis Program of the U.S. Geological Survey; Nebraska Game and Parks Commission; U.S. Fish and Wildlife ServiceOpen Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

General-purpose spectrometer for vacuum breakdown diagnostics for the 12 GHz test stand at CERN

We discuss a spectrometer to analyze the electrons and ions ejected from a high-gradient CLIC accelerating structure that is installed in the klystron-driven 12 GHz test-stand at CERN. The charged particles escaping the structure provide useful information about the physics of the vacuum breakdown within a single RF pulse. The spectrometer consists of a dipole magnet, a pepper-pot collimator, a fluorescent screen and a fast camera. This enables us to detect both transverse parameters such as the emittance and longitudinal parameters such as the energy distribution of the ejected beams. We can correlate these measurements with e.g. the location of the breakdown inside the structure, by using information from the measured RF powers, giving in that way a complete picture of the vacuum breakdown phenomenon. The spectrometer was installed during Spring 2014 and will be commissioned during Summer 2014

The Momentum Distribution of the Decelerated Drive Beam in CLIC and in the Two-beam Test Stand at CTF3

We present analytical calculations of the momentum spectrum of the drive beam in CLIC and the CLIC Test Facility CTF3 after part of its kinetic energy is converted to microwaves for the acceleration of the main beam. The resulting expressions are used to determine parameters of the power conversion process in the Power Extraction Structure (PETS) installed in the Two-beam Test Stand in CTF3

Recent Results from CTF3 Two Beam Test Stand

From mid-2012, the Two Beam Test Stand (TBTS) in the CTF3 Experimental Facility is hosting 2 high gradient accelerating structures powered by a single power extraction and transfer structure in a scheme very close to the CLIC basic cell. We report here about the results obtained with this configuration as: energy gain and energy spread in relation with RF phases and power, octupolar transverse beam effects compared with modeling predictions, breakdown rate and breakdown locations within the structures. These structures are the first to be fitted with Wake Field Monitors (WFM) that have been extensively tested and used to further improve the structures alignment on the beam line. These results show the unique capabilities of this test stand to conduct experiments with real beams