Design and Construction of a Longitudinally Polarized Solid Nuclear Target for CLAS12

A new polarized nuclear target has been developed, constructed, and deployed at Jefferson Laboratory in Newport News, VA for use with the upgraded 12 GeV CEBAF (Continuous Electron Beam Accelerator Facility) accelerator and the Hall B CLAS12 (12 GeV CEBAF Large Acceptance Spectrometer) detector array. This ‘APOLLO’ (Ammonia POLarized LOngitudinally) target is a longitudinally polarized, solid ammonia, nuclear target which employs DNP (Dynamic Nuclear Polarization) to induce a net polarization in samples of protons (NH3) and deuterons (ND3) cooled to 1K via helium evaporation, held in a 5T polarizing field supplied by the CLAS12 spectrometer, and irradiated with 140 GHz microwave radiation. It was utilized in the RGC (Run Group C) experiment suite through a collaboration of the JLab Target Group, Old Dominion University, Christopher Newport University, the University of Virginia, and the CLAS Collaboration. RGC comprised six experiments which measured multiple spin-dependent observables across a wide kinematic phase space for use in nucleon spin studies. The dimensional constraints necessary for the incorporation of APOLLO into CLAS12, as well as the considerations necessary to utilize the CLAS12 solenoid, introduced unique challenges to the target design. This document presents the innovative solutions developed for these challenges including a novel material transport system, superconducting magnetic correction coils, and an all new bespoke NMR (Nuclear Magnetic Resonance) system. In addition to a detailed description of the complete target system and an initial report of the RGC experimental run, it will also present a study of Quark-Hadron Duality in the g1 spin structure function based on Hall B EG1b data and pQCD fits from the JAM (Jefferson Lab Angular Momentum) Collaboration

Leguminous service crops in cereal production at high latitudes : provision of ecosystem services and disservices from a novel intercropping system

Service crops, crops grown to provide services such as soil protection, weed control, or nutrient capture and provision, can reduce the need for mineral fertilisers and intensive weed control. However, high biomass production is necessary in order for these services to be provided. This can be difficult to achieve at high latitudes (e.g. Sweden), where growing conditions are poor after main crop harvest, when service crops are usually sown. The aim of this thesis was to increase the understanding of service crop species choice and management on service and disservice delivery. Leguminous service crops were sown into oats in spring/early summer for early establishment of the service crop, and terminated in the following spring in winter wheat. The results showed that species sown at the same time as oats, rather than one month later, and which survived oat harvest and cold temperatures in winter, were best at suppressing weeds and increasing winter wheat yields, although they often also reduced oat yield in the establishment year. Presence of a productive service crop (>0.2 t dry weight (DW) per ha) reduced the occurrence of competitive-stress tolerant weed species, in favour of ruderal species, in the oat row and in combination with oat biomass >8 t DW ha-1 the occurrence of competitive perennial species was reduced. Modelling the system using APSIM NG revealed that the service crops mainly provided positive effects on the cropping system, in terms of increased winter wheat yield, increased soil carbon input and reduced losses of nitrogen and water during most of the study period. Drawbacks were reduced oat yield and increased nitrogen losses from winter wheat and in the fallow period after winter wheat. I conclude that the studied intercropping system has potential to provide services and reduce disservices, but that the system needs improvement. These improvements are mainly to ensure even establishment and good termination of the service crops

The Augustana Story: Shaping Lutheran Identity in North America

Review of: "The Augustana Story: Shaping Lutheran Identity in North America," by Maria Erling and Mark Granquist

From America to Norway: Norwegian-American Immigrant Letters, 1838–1914, volume 1, 1838–1870

Review of: "From America to Norway: Norwegian-American Immigrant Letters, 1838–1914: 1838–1870," edited and translated by Orm Øverland