L.W. Fagg

Large-aperture system for high-resolution 180° electron scattering

Abstract A new system for 180° electron scattering has been put into operation at the superconducting Darmstadt linear electron accelerator S-DALINAC, using a large-aperture QCLAM spectrometer. The properties of the spectrometer allow for high-resolution 180° measurements with a larger momentum acceptance than that of any previous 180° system, together with unprecedented capabilities for solid angle definition as well as for alignment and monitoring of the system. The large angular acceptance and the precise angular definition allow the solid angle acceptance of the system to be specified by software cuts after the data have been taken, permitting the appropriate balance between maximum statistical precision and maximum longitudinal-to-transverse suppression ratio.

Low-multipolarity magnetic transitions in Si-30, S-32, and S-34 studied by 180-degrees electron scattering

Low-multipolarity magnetic transitions of [sup 30]Si, [sup 32]S, and [sup 34]S were studied by 180[degree] inelastic electron scattering at low momentum transfers ([ital q][similar to]0.3--0.5 fm[sup [minus]1]). These measurements, made in the excitation energy region from 9 to 14 MeV, revealed several previous unreported levels. These are the first low-[ital q] results obtained by electron scattering for [sup 30]Si and [sup 34]S. Multipolarities and transition strengths for all the observed transitions were determined in a model-independent analysis. A large fragmentation of [ital M]1 strength is observed in the 4[ital N]+2 nuclei [sup 30]Si and [sup 34]S, while more strength is concentrated into fewer transitions in the self-conjugate nucleus [sup 32]S. The experimental [ital M]1 strength distributions are compared with configuration-mixing shell-model calculations. The sums of the transition strengths are in good agreement with recent shell-model calculations using an effective [ital M]1 operator.

Are There Intimations of Divine Transcendence in the Physical World

This essay, suggesting two physical phenomena that might serve as meaningful analogies to divine transcendence, is a theological complement to two earlier Zygon articles that show how the underlying ubiquity of electromagnetic phenomena in all of nature is a compelling physical analogy to divine immanence. My perception of transcendence and its relation to immanence are specified to provide a context for the discussion. A description of our being ensconced in what I term a cosmic cocoon introduces the discussion of how the finite limit of the speed of light and quantum non-locality could be considered as physical analogies of, or pointers to, Cods transcendence. The relevance of our cosmologic fixture to transcendence is also treated. Selected examples of transcendence found in spiritual experiences and in religious scriptures are presented that complement the physical discussion. Finally, the relevance of this study to a theology of nature as well as a natural theology is examined.

Sacred Indwelling and the Electromagnetic Undercurrent in Nature: A Physicist's Perspective

Wolfhart Pannenberg has related the concept of the physical field to the idea of Gods divine cosmic field in all of creation. In this article I proffer a physicists viewpoint by treating the subject from a more specific and focused perspective. In particular, I describe how electromagnetic interactions underlie the operation of all earthly nature, including human beings and their brains. I argue that this ubiquity constitutes a compelling physical analogy for the ubiquity of Gods indwelling. The discussion includes the role of electromagnetism in quantum theory, concepts of time, and the evolution of life. I suggest the value of such analogical thought as an area of study to be exploited in the development of a theology of nature as well as a significant datum in the pursuit of a tenable natural theology. This article is intended to clarify, refine, and considerably expand upon an earlier article published in Zygon (Fagg 1996). Included also are discussions on the role of electromagnetism in our sense of evil and eternity.

180/sup 0/ electron scattering from /sup 3/He

Elastic and inelastic cross sections for 180/sup 0/ electron scattering from /sup 3/He were measured at incident electron energies of 40.44, 50.58, and 60.63 MeV. Our radiatively corrected cross section measurements are in good agreement with theoretical calculations of the behavior near the two-body breakup threshold at 5.5 MeV. The measurements were also compared to cross sections calculated in the zero-range approximation and to sum rules. At q = 0.602 fm/sup -1/ the measured magnetic radius was r = 1.79 + 0.14 fm. The possibility of the existence of a state at about 10 MeV excitation is also discussed.

Magnetic dipole strength in 46Ca observed with 180° electron scattering

Abstract Results are presented from a search for M1 strength in 46 Ca by means of 180° electron scattering at low momentum transfer. We report the presence of a 1 + state at 13.02±0.04 MeV with a reduced electromagnetic transition strength, B (M1)=2.47±0.77 μ 2 N . The excitation energy of this level is ∼2 MeV higher than strong 1 + states seen in other even-even calcium isotopes. No evidence was seen for M1 strength in the 10 MeV excitation energy region where strength is predicted by shell model calculations.

Preliminary results of a new determination of the rms charge radius of the proton

Abstract New absolute and relative cross sections for elastic scattering of electrons from the proton have been measured using the linac facilities at NIST. The data were obtained using a high-pressure, flowing-gas target cell alternately filled with H 2 and CH 4 gas. The measurements span a momentum transfer range from 0.22 to 0.73 fm −1 . These new results have been combined with an extensive set of existing elastic electron scattering data in a Fourier-Bessel analysis to obtain the charge density parameters and the rms radius of the proton. Some selection among the available data was necessary because of inconsistencies between published data sets. We obtain an rms radius of 0.865 ±0.020 fm.

Design and testing of apparatus for 180° electron scattering at low momentum-transfer

Abstract We report the design, installation, and performance history of a system for electron scattering measurements at 180°. The initial planning for this system is described, with reference to earlier 180° systems, and including the rationale behind various crucial design choices. Magnet optics, sliding vacuum seals, beam monitoring, focal plane corrections, and background suppression measures are discussed. Sample data from representative scattering experiments are presented.

A rugged sliding vacuum seal for angular motion over a limited range

Abstract We report the construction and successful testing of a sliding vacuum seal of novel design that is substantially more rugged than conventional sliding foil arrangements. The device is fabricated from a stack of concentric aluminum sectors of graduated size. Vacuum seal is maintained by neoprene O-rings between adjacent sectors, allowing relative motion of the various sectors over a total angular range of 30° on a chamber of mean radius ∼ 22 cm.

Electroexcitation of 8^{-} states in^{52}Cr

Inelastic electron scattering at incident energies between 170 and 260 MeV was used to identify and study M8 transitions in /sup 52/Cr. A strong transition to an 8/sup -/ state at E/sub x/ = 15.47 MeV was observed, as well as a number of weaker transitions. The results are compared with a single particle-hole shell model calculation that uses a model space of the form ((f/sub 7/2//sup 11/ x g/sub 9/2/)/sub 8//sub -/. The shell model calculation and systematics in neighboring nuclei were used to determine the isospin of the observed states. The experimentally determined strengths exhaust 60.8% and 34.5% of the T = 3 and T = 2 sum rules, respectively.