Energy levels of A = 21−44 nuclei (V)

This paper is focused mainly on the subject of elastic magnetic electron scattering and how it has come to be a useful tool for studying the spatial distributions of convection and magnetization currents in the nuclear ground state. Using such a probe, emphasis is clearly placed on the electromagnetic currents provided by the valence nucleons in the nucleus, indeed, by neutrons as well as protons. These do not yield a complete description of the problem, however, and more complex nuclear many-body configurations are generally required. Various models are employed (shell-model configuration mixing, core-polarization effects, models of deformed nuclei, for instance), giving rise to quantitative comparisons with experimental measurements. Moreover, to achieve such successful descriptions, especially at high momentum transfers, it is frequently necessary to go beyond a purely one-body nucleonic reaction mechanism and to include the effects of two-body meson-exchange currents based on non-nucleonic degrees of freedom ($\ensuremath{\pi}$,$\ensuremath{\rho}$,$\ensuremath{\Delta},\dots{}$). The authors discuss all of these various facets of the problem, beginning with surveys of the historical development of the field and of the experimental techniques employed in such studies. They present a detailed treatment of the formalism needed in discussions of elastic electron scattering, including an introduction to the density-matrix approach to the nuclear many-body problem, with simple examples to clarify the ideas involved. For the nonspecialist a separate section of illustrative examples is supplied in which qualitative discussions of various aspects of the physics accessible in such ($e$,${e}^{\ensuremath{'}}$) studies are highlighted. Experimental and theoretical results for a large number of nuclei ranging from $A=2 \mathrm{to} 209$ are described in detail; this represents a compilation of virtually all of the high-quality data that are available at present. The paper concludes with projections as to which directions may be followed in the future, in particular, with a relatively complete discussion of the use of polarization in elastic electron scattering.

Elastic magnetic electron scattering from nuclei

A set-up of three high-resolution magnetic spectrometers, for simplicity named A, B and C, has been built as the central facility for the precise determination of double and triple coincidence cross sections of hadron knock-out and meson production through the scattering of electrons at the Mainz microtron MAMI. The spectrometers A and C with point-to-point optics in the dispersive plane and parallel-to-point optics in the non-dispersive plane have a solid angle of 28 msr and a momentum acceptance of 20 and 25%, respectively. They each consist of a quadrupole, a sextupole and two dipole magnets, reaching maximum momenta of 735 and 550 MeV/c, respectively. The spectrometer B has a solid angle of 5.6 msr and a somewhat reduced momentum acceptance of 15%, but it reaches a maximum momentum larger than that of the MAMI electron beam (855 MeV/c). It consists of a single-clamshell dipole magnet with point-to-point optics in both planes. Each spectrometer is equipped with a position-sensitive detector system consisting of four planes of vertical drift chambers, two planes of plastic scintillators and a threshold gas Cherenkov detector. The operational experiences demonstrate that all three spectrometers exceed the specifications. Selected results of double (e, e′ x ) and triple (e, e′ x 1 x 2 ) coincidence experiments, x 1 and x 2 standing for charged hadrons, are presented, which demonstrate the performance of the whole set-up.

The three-spectrometer facility at the Mainz microtron MAMI

https://cds.cern.ch/record/261499/files/P00022619.pdf

3H and 3He electromagnetic form factors

1 Introduction 2 Electromagnetic interactions of charged particles with matter 3 Interactions of photons and neutrons with matter 4 Drift and diffusion of charges in gases 5 Collisional excitations and charge multiplication in uniform fields 6 Parallel plate counters 7 Proportional counters 8 Multiwire proportional chambers 9 Drift chambers 10 Time projection chambers 11 Multitube arrays 12 Resistive plate chambers 13 Micro-pattern gas detectors 14 Cherenkov ring imaging 15 Miscellaneous detectors and applications 16 Time degeneracy and aging Further reading References Index

Gaseous Radiation Detectors: Fundamentals and Applications

Focal plane instrumentation: A very high resolution MWPC system for inclined tracks

The unique high-resolution and high-energy features of the electron-scattering facility at the MIT-Bates Accelerator were used to locate a dominant narrow resonance at 15.045 +- 0.035 MeV in /sup 24/Mg. A spin-parity assignment of 6/sup -/ and an isospin T=1 assignment were made. The M6 form factor was measured and compared to the prediction of a theoretical calculation which uses the open-shell random-phase approximation on a shell-model ground state for /sup 24/Mg.

Discovery of a6−,T=1Resonance inMg24via High-Resolution Inelastic Electron Scattering

A simple model for nuclear surface vibrations in permanently deformed nuclei does well in reproducing electron scattering cross sections of rotational levels built on a K/sup ..pi../= 0/sup -/ intrinsic octupole vibration in /sup 238/U.

A. Hirsch

Papers

Focal plane instrumentation: A very high resolution MWPC system for inclined tracks

Discovery of a6−,T=1Resonance inMg24via High-Resolution Inelastic Electron Scattering

Electron scattering from the octupole band in /sup 238/U