L’utilisation du tritium dans l’industrie horlogère pour amplifier la luminosité de la peinture luminescente peut être à l’origine de doses non négligeables au personnel de posage et conduit à la production de déchets radioactifs qui doivent être éliminés de façon correcte. Comme l’indiquent certaines enquêtes, bien des montres commercialisées n’ont pas la luminosité qu’est en droit d’attendre l’acheteur conformément à la norme concernant la radioluminescence pour les instruments horaires. Par ailleurs, il existe aujourd’hui des produits de substitution non radioactifs sur le marché. Enfin, la difficulté de maîtriser les héritages radiologiques provenant de l’industrie horlogère favorise inévitablement leur dissémination. L’ensemble de ces éléments est à la base du réexamen de la justification des peintures luminescentes radioactives. Les résultats exposés dans cet article confirment que la stratégie visant à renoncer naturellement à leur utilisation et à assister les entreprises dans le ramassage et l’élimination contrôlée des déchets est profitable à la radioprotection.

We present data on the differential cross section for neutron-proton scattering for an incident neutron energy of 67 MeV. These data allow a precise determination of the 1P1 phase which, in phase-shift analyses, is strongly correlated with the S-D amplitude which we are measuring via different observables.

The authors conclude, using the current world data around 50 MeV there is no question that experimental values of e1 and 1P1 are significantly different from theoretical prediction. (AIP)Received 20 December 1993DOI:https://doi.org/10.1103/PhysRevLett.72.2665©1994 American Physical Society

We have measured the spin-dependent total cross-section difference ΔσL in neutron-proton scattering at 66 MeV which is highly sensitive to the 3S1-3D1 mixing parameter ε1. The result ΔσL = −(26.5 ± 1.2 ± 1.6) mb is in good agreement with recent phase-shift analyses that require a large ε1 (a stronger tensor force).

We have measured the analyzing power Ay in np scattering at 68 MeV with typical accuracies of ⩽0.01. The experiment covers the angular range 38° ⩽ θc.m. ⩽ 156° by observing either the scattered neutrons or the recoil proton. The results are compared to the predictions of the Bonn and Paris NN potentials as well as to recent phase-shift analyses.

The depolarization parameter D in proton- 13C elastic scattering at 72 MeV has been measured at 34° ⩽ θc.m. ⩽ 69° with an overall accuracy of (3–4) × 10−3. Significant deviations from D = 1 were observed around 65°. This finding constitutes unambiguous evidence for a nucleon-nucleus spin-spin interaction. The data were fitted by a conventional optical model potential which included a real, spherical spin-spin potential with surface form factor and Vss = 0.7 ± 0.1 MeV. Good description of the data was also obtained by a microscopic calculation which was based on a density dependent, effective interaction and shell model wave-functions. Similar calculations for 9Be, 15N, 29Si and 31P are consistent with recent data. In particular, they explain the large effects observed for 15N.

We report a first measurement of the spin-correlation parameter ${\mathit{A}}_{\mathit{z}\mathit{z}}$ in neutron-proton scattering at 67.5 MeV. The results, obtained in the angular range 105\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\theta}}}_{\mathrm{c}.\mathrm{m}.}$\ensuremath{\le}170\ifmmode^\circ\else\textdegree\fi{} with typical accuracies of 0.008, are highly sensitive to the $^{3}$${\mathit{S}}_{1}$${\mathrm{\ensuremath{-}}}^{3}$${\mathit{D}}_{1}$ mixing parameter ${\mathrm{\ensuremath{\epsilon}}}_{1}$. A phase-shift analysis based on the current world data yields a value of ${\mathrm{\ensuremath{\epsilon}}}_{1}$ significantly higher than predicted by modern potential models.

We report a first measurement of the spin-correlation parameter A(zz) in neutron-proton scattering at 67.5 MeV. The results, obtained in the angular range 105-degrees less-than-or-equal-to theta-c.m. less-than-or-equal-to 170-degrees with typical accuracies of 0.008, are highly sensitive to the 3S1-3D1 mixing parameter epsilon-1. A phase-shift analysis based on the current world data yields a value of epsilon-1 significantly higher than predicted by modern potential models.

We have measured the analyzing power Ay in n-d elastic scattering at 67.0 MeV. The experiment was based on the detection of recoil deuterons, allowing for a precise measurement of the backward angular range. The results are in good agreement with recent three-nucleon calculations which are based on the Paris and Bonn NN potentials.

Abstract The elastic scattering of 3 He from 208 Pb has been measured at 49 MeV and 130 MeV over a large angular range covering both diffractive and refractive regions. The model-unrestricted Fourier-Bessel analysis of the 130 MeV data results in a unique solution for the underlying scattering potential. Its real central part fits very well into the systematics observed in nucleon, deuteron and alpha scattering and agrees with double folding calculations confirming the weak density-dependence of the nucleon-nucleon interaction found recently.

We have calibrated the analyzing power Ay in proton-carbon elastic scattering at 71.2 MeV via double-scattering with polarized beam. An accuracy of ±0.001 was achieved using a highly efficient setup (statistical uncertainty of ±0.0003) and a new type of analysis based on asymmetry ratios. Our result Ay=0.986±0.001 may indicate the existence of a point with Ay=1 near 65 MeV.

dans la diffusion klastique proton- nucleus nous prksentons la dktermination de l'interaction spin-spin nucleon-nucleus. Des resultats prkcis et rdcents pour des noyaux de spin 112 autour de 70 MeV prouvent sans ambiguit6 la presence des effets spin-spin. Ces resultats concordent avec un calcul de type DWBA, qui prend en compte un potentiel spin-spin microscopique. La comparaison avec l'analyse selon le modble "potentiel op- tique" montre que les effets ne sont pas des propriktks globales mais dkpendent essentiellement de la structure du noyau. Abstract

We discuss the determination of the nucleon-nucleus spin-spin interaction from measurements of the depolarization parameter D in elastic proton-nucleus scattering. Recent, precise data for spin-1/2 nuclei around 70 MeV yield unambiguous evidence for spin-spin effects. The data are well described by a DWBA type of calculation which includes a microscopically derived spin-spin potential. The comparison with optical model calculations indicates that spin-spin effects are not global features but depend sensitively on nuclear structure.

Results of measurements of the transverse polarization transfer coefficients ${\mathrm{K}}_{\mathrm{y}}^{\mathrm{y}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) for ${\mathrm{H}}^{2}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow})pp at 54 and 71 MeV are presented. The magnitude and energy dependence of this parameter have been determined with sufficient precision (4%) to permit the use of this reaction as a source of nearly monoenergetic polarized neutrons in precise measurements. ${\mathrm{K}}_{\mathrm{y}}^{\mathrm{y}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) is found to have a significant dependence on excitation energy. The results at low excitation energy are in agreement with calculations in the impulse approximation using the nucleon-nucleon phase shifts obtained from the Bonn or Paris potentials. A substantial difference from the results obtained using the empirical phase shifts is found. Results of measurements of the longitudinal polarization transfer coefficient ${\mathrm{K}}_{\mathrm{z}}^{\mathrm{z}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) at 54 MeV are also presented.

We have measured the analyzing power A y in n-d elastic scattering at 67.0 MeV. The experiment was based on the detection of recoil deuterons, allowing for a precise measurement of the backward angular range. The results are in good agreement with recent three-nucleon calculations which are based on the Paris and Bonn NN potentials.