Do new data on the nucleon spin agree with what we expected in the high x_bj region? Left: Neutron spin asymmetry A1n; Right: Spin directions of quarks inside the nucleon.
The Quark-Meson Coupling (QMC) model, a theory which takes the radical step of incorporating self-consistent changes in the quark structure of a nucleon when it is bound in matter, has been transformed into a theory of quasi-nucleons interacting through many-body forces. This adjustment allows the QMC model to be related to the time-honored descriptions of the nucleus where nucleon structure was supposed to play no role. Of course, in experiments conducted at very high energies, it is customary to see the nucleus as a collection of quarks interacting via the exchange of gluons.
Jefferson Lab continues to integrate the fruit of superconducting radiofrequency (SRF) R&D into the production of higher-performing accelerator components. One dimension of this is a program to leverage recent technological developments in the design and implementation of higher quality standards and more efficient techniques for the chemical processing, clean handling and assembly of accelerator components.
The purpose of this collaboration between the University of Florida (UF; David Gilland, PI), the University of South Florida (USF; Claudia Berman, Maria Kallergi, PIs) and Thomas Jefferson National Accelerator Facility (Jefferson Lab) is to design, build and evaluate compact, mobile, high resolution gamma ray and positron medical imaging devices. The targeted applications are molecular imaging of heart disease and breast cancer. Mobile gantries with articulated arms will position the imaging cameras close to the body.
The Jefferson Lab Detector and Imaging Group in collaboration with Oak Ridge National Laboratory (Dr. Justin Baba), Johns Hopkins University (Dr. Martin Pomper) and the University of Sydney (Dr. Steve Meikle) is developing an imaging methodology that utilizes SPECT and X-ray CT for small animal research. The primary challenging task of this project is to develop a SPECT imaging system to allow molecular imaging of unrestrained and un-anesthetized mice.
The high-Q superconducting cavities being developed at JLab have complicated RF control, with large Lorentz detuning at start up. Typically, Lorentz detuning can be much larger than the loaded cavity bandwidth. Several near-term (e.g. JLab 12 GeV project) and longer-term (e.g. ERLs) projects will involve operation of a large number of high-Q superconducting cavities. Of particular importance in these machines is the stability with respect to ponderomotive instabilities, rapid turn-on time and recovery from a trip.
A positron emission mammography/tomography (PEM/PET) biopsy device is being developed to detect suspicious breast lesions and then to guide needle biopsies of these lesions in women who have indeterminate mammograms because of dense or fibroglandular breasts. The PI of this NIH-funded project is Ray Raylman at West Virginia University (WVU). Jefferson Lab will design and build two sets of large-area PEM detectors that will be integrated into a rotating gantry at WVU.
Well-behaved magnetic thin films of stoichiometric alloys, such as an alloy of nickel and iron (NiFe), are not easily formed. Anne Reilly and colleagues at Jefferson Lab and The College of William & Mary excited bulk NiFe with the Jefferson Lab FEL and found a strikingly different response than that found with a conventional titanium-sapphire laser.
Nuclear-spin polarized targets play a key role in experimental nuclear and particle physics. They are essential for understanding how the proton and neutron get their spins from their constituent quarks and gluons and for measuring the electromagnetic structure of these nucleons in both their ground and excited states. While the Jefferson Lab Frozen Spin Target (FROST) is the fourth and latest polarized target to be used at JLab, it is the first to be entirely designed and built here.
