C. Fred Moore

A digital technique for neutron-gamma pulse shape discrimination

Abstract A technique employing integrating analog-to-digital converters to do pulse shape discrimination between neutron and gamma initiated scintillations in liquid scintillators is described. The technique involves a direct comparison of the fast and slow components of the light output from the scintillator.

The nuclear reaction Y89(d, p)Y90

Abstract The nuclear reaction Y89(d, p)Y90 has been studied with 12 MeV deuterons. The observed Q value for the reaction is 4635 ± 5 keV. Magnetic analysis of the resulting proton groups at 45°, 65°, 75°, 95°, 105°, 124° and 132.5° indicates the existence of the configurations ( p 1 2 ) 1 ( d 5 2 ) 1 , ( p 1 2 ) 1 ( S 1 2 ) 1 ,( p 1 2 ) 1 ( d 3 2 ) 1 and ( p 1 2 ) 1 ( g 7 2 ) 1 . There is approximate agreement between the intensities of the proton groups and the statistical weights (2J + 1) for individual states within a configuration at the middle angles. Position and splittings of the resulting doublets agree well with Kims calculations using tensor forces. There is a clear indication that the excited proton configuration ( g 9 2 ) 1 ( d 5 2 ) 1 is populated at this bombarding energy to less than one part in a thousand relative to the ground state configuration or the excited neutron configurations. Angular distributions of the configuration using solid state detectors agree well with theory in the case of the ( p 1 2 ) 1 ( S 1 2 ) 1 configuration but not as well in the case of the ground state configuration. Previous work on the neutron capture gamma rays is successfully correlated with the levels observed in this work and suggests the tentative assignment of the 1 + , ( g 9 2 ) 1 ( g 7 2 ) 1 state.

Neutron-proton radius differences and isovector deformations from π+ and π− inelastic scattering from 18O

Abstract π+ and π− elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio σ(π − ) σ(π + ) for the 21+ state is 1.86(16), while for the 31− state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31− transition. Optical model analysis of elastic scattering leads to the conclusion that 〈r n 2 〉 1 2 −〈r p 2 〉 1 2 =0.03(3) fm .

CalciumK X-ray spectra produced by oxygen, alpha-particle, and proton bombardment

Kα andKβ X-rays of calcium were produced by bombarding a thick calcium wafer with oxygen, helium and hydrogen ions. These reactions produce a substantial amount of inner shell ionization. TheK X-ray spectra contain X-ray lines from calcium which emanate from initial states with a varying degree ofK orL shell vacancies. The initial configurations were assigned on the basis of Hartree-Fock-Slater calculated energies. Related intensity ratio of1s→2p (Kα) transitions and of1s→3p (Kβ) transitions of H plus Ca, He plus Ca and O plus Ca were obtained. In addition to observing many new transitions due to multipleK and/or multipleL shell vacancies, energy shifts relative to the H plus Ca spectrum were observed in the O plus Ca spectrum due toM shell vacancies.

Indication of Δ-hole configurations in 12C(15.11 MeV)

Abstract A strong energy dependent enhancement is seen in inelastic pion scattering from 12 C to the 1 + , T = 1 state at 15.11 MeV, but not to the 1 + , T = 0 state at 12.71 MeV. This enhancement may be interpreted as evidence for the direct excitation of delta-hole (Δ-h) components in the wave function of the T = 1 state. The required Δ-h amplitude is estimated and found to be in agreement with calculations of Bohr and Mottelson.

Systematics of pion double-charge-exchange reactions on T = 0 nuclei

Abstract Pion induced double charge exchange on 12 C, 16 O, 24 Mg, 28 Si, 32 S, and 40 Ca exhibits forward-angle cross sections that vary rapidly with pion energy and fall off roughly as A −4 3 . Angular distributions at 164 MeV appear diffractive for targets of 12 C, 16 O, and 40 Ca.

A search for πNN bound systems

Abstract The d(π+, π−)T+++ and the d(π−, π+) T− reactions were studied at an incident pion energy of 260 MeV. Outgoing negative pions were detected at 35° and 55° in the first reaction, and the positive pions at 45° in the second. Indications for structures corresponding to a (π+pp) system with a mass of 2003.0±1.0 MeV and a (π−nn) system with a mass of 200.1±1.5 MeV were observed with marginal statistical significance. Upper limits for the cross sections are obtained.

Pion double charge exchange above the Δ(1232) resonance

Abstract First measurements of exclusive cross sections for the ( π + , π − ) reaction at incident energies of 300–500 MeV are reported. For the analog-state transitions in 14 C and 18 O the 5° cross sections are found to remain nearly constant in this energy interval. This behavior is in disagreement both with predictions based on six-quark cluster models and with simple expectations based on recent single-charge-exchange measurements.

Measurement of isospin mixing between the 1+ doublet in 12C using pion inelastic scattering ☆

Abstract Pion inelastic scattering has been used to extract the off-diagonal charge dependent matrix element, H01, between the Jπ = 1+ doublet of states at 12.71 (T = 0) and 15.11 (T = 1) MeV in 12 C . The reported measurements yield a value, H01 = 148 ±29 keV, in good agreement with recent electromagnetic measurements.

Sodium satellite structure

A sample of sodium was bombarded by proton, helium, and oxygen beams and the subsequentK X-ray spectra measured. The spectra exhibit a preponderance of structure which is speculated upon in light of HFS calculations. The strongest lines are ascertained to be the normalKα satellite spectra produced by multiple electron vacancies in single ion-atom collisions.