[en] The neutron small angle camera D11 at the High Flux Reactor in Grenoble uses a two-dimensional multiwire proportional chamber with 3808 elements of 1cm² spread over 3808cm². The limits imposed by the detector onto the D11 system is the overall area of the sensitive volume. The limits, however, imposed on the system by other components are more restricting. These are: the limited count rate due to the electronic part between detector and on-line computer; the limited wavelength resolution due to the monochromator; the limited angular region due to a rigid position of the detector with respect to the incoming beam; the last two limitations are a consequence of the possibility to cover a great domain of scattering angles with the same instrument using the same relative resolution

[en] It is possible to investigate complicated biological structures by neutron diffraction. The present report deals with results of three investigations: 1) Neutron/diffraction at metaphase-chromophores; 2) The comparison of acetylated and deacetylated nuclei; 3) The dissolution and reconstitution of structures of higher order. (BHO)

[en] The neutron small-angle scattering system at the high-flux reactor in Grenoble consists of three major parts: the supply of cold neutrons via bent neutron guides; the small-angle camera D11; and the data handling facilities. The camera D11 has an overall length of 80 m. The effective length of the camera is variable. The full length of the collimator before the fixed sample position can be reduced by movable neutron guides; the second flight path of 40 m full length contains detector sites in various positions. Thus a large range of momentum transfers can be used with the same relative resolution. Scattering angles between 5 x 10^-4 and 0.5 rad and neutron wavelengths from 0.2 to 2.0 nm are available. A large-area position-sensitive detector is used which allows simultaneous recording of intensities scattered at different angles; it is a multiwire proportional chamber. 3808 elements of 1 cm² are arranged in a two-dimensional matrix. (Auth.)

[en] The neutron small-angle scattering system at the High-Flux Reactor in Grenoble consists of three major parts: the supply of cold neutrons via bent neutron guides; the small angle camera D11; and the data handling facilities. The camera D11 has an overall length of 80 m. The effective length of the camera is variable. The length of the collimator before the fixed sample position can be reduced by movable neutron guides; the secondary flight path of 40 m full length contains detector sites in various positions. Thus, a large domain of momentum transfers can be exploited. Scattering angles between 5.10^-4 and 0.5 rad and neutron wavelengths from 0.2 to 2.0 nm are available with the same instrument and the same relative resolution. A large-area position-sensitive detector is used which allows simultaneous recording of intensities scattered into different angles; it is a multiwire proportional chamber. 3808 elements of 1 cm² are arranged in a two-dimensional matrix. Future development comprises an increase of the limit in the count rate due to the electronic interface between the detector and on-line computer, actually at 5.10⁴ per sec. by one order of magnitude

[en] The paper deals with small-angle scattering of neutrons by catalase tetramers, dimers, and monomers and with neutron diffraction by helical assemblies of tetramers in the form of tubules. A preliminary study of catalase is described

[en] The paper describes the first measurements of neutron diffraction from vertebrate striated muscle, and discusses the possible structural implications of the results. It is clear that neutron diffraction contributes significantly to the analysis of muscle structure because of the contrast variations in H₂O--D₂O mixtures and the characteristic differences in the scattering densities of different muscle proteins

[en] The forward scattering of cold neutrons in small-angle scattering experiments on macromolecules dissolved in mixtures of light and heavy water is predominantly determined by the large incoherent cross section of the hydrogen atoms leading to an isotropic background level. The probability per unit solid angle for forward scattering by samples rich in H₂O is approximately equal to the fraction of the primary beam which has not been transmitted through the sample, divided by the full solid angle 4π. When using the camera D11 at the high flux reactor in Grenoble [Ibel (1976), J. Appl. Cryst. 9, 296-309] this simple relation is fulfilled within +- 5% by a 1 mm thick sample of H₂O at 281.8 K using neutrons of 1.0 nm wavelength. In D₂O, the coherent cross section is of the same order as the incoherent one, and about one half of all those neutrons which had been removed from the primary beam are scattered into large angles. The experimental results and the derived graphs allow the determination of the effective forward scattering per unit solid angle for any volume fraction of D₂O in H₂O/D₂O mixtures around room temperature by a simple and accurate transmission experiment in conjunction with the measurement of the scattering of one single sample of H₂O of 1 mm thickness, for neutrons of wavelengths from 0.45 to 1.0 nm. (Auth.)

No abstract available

No abstract available

No abstract available