[en] The heart of each time-of-flight neutron scattering instrument is its complement of detectors and the associated encoding and counting electronics. Currently there are ten fully-scheduled neutron scattering instruments in operation at IPNS, with three more instruments under development. Six of these instruments use position-sensitive neutron detectors (PSDs) of various types. These PSDs include a 30 cm x 30 cm, ∼3 mm resolution, neutron Anger camera area PSD with ⁶Li-glass scintillator; a 2.5 cm dia, ∼0.7 mm resolution, microchannel-plate area PSD with ⁶Li-glass scintillator; a 20 cm x 20 cm, ∼5 mm resolution, ³He proportional counter area PSD; a 40 cm x 40 cm, ∼4 mm resolution, ³He proportional counter area PSD; a flat 25 cm long, ∼1.6 mm resolution, ³He proportional counter linear PSD; and 160 cylindrical ³He proportional counter linear PSDs, each of which is 1.27 cm in dia and 60 cm long and has ∼14 mm resolution. In addition to these PSDs, ∼750 standard cylindrical ³He proportional counters of various sizes are utilized on IPNS instruments, and ∼20 BF₃ pulsed ion chambers are in use as beam monitors. This paper discusses these various detectors and associated electronics, with emphasis on the instrumental specifications and the reasons for the selection of the different types of detectors. Observed performance of these detectors is also discussed. 19 refs., 5 figs., 2 tabs

[en] The correlation technique at a pulsed neutron spallation source using a mechanical pseudo-random chopper is found to be technically feasible and can be accomplished with relatively minor changes to a conventional chopper spectrometer. The strong variation of resolution with incident energy is a serious disadvantage for some applications. There may be specific instances in which the method is advantageous to the conventional chopper at such a source, but these remain to be identified. 8 refs., 5 figs

[en] The neutron inelastic scattering function of liquid helium-3 at 0.015 K has been measured for wave vectors in the range 0.8 A^-1 less than or equal to q less than or equal to 2.2 A^-1. For q less than or equal to 1.3 A^-1 the spectrum shows a two-peak structure and the peaks are identified as quasiparticle excitations and zero sound excitations, respectively. By comparing the measured structure factor with the x-ray structure factor the spin-dependent scattering cross section and the corresponding structure factor are determined. It is conjectured that the quasiparticle excitations at small values of q are seen through the spin-dependent scattering

[en] The heart of each time-of-flight neutron scattering instrument is its complement of detectors and the associated encoding and counting electronics. Currently there are ten fully-scheduled neutron scattering instruments in operation at IPNS, with three more instruments under development. Six of these instruments use position-sensitive neutron detectors (PSDs) of various types. These PSDs include a 30 cm x 30 cm, ∼3 mm resolution, neutron Anger camera area PSD with ⁶Li-glass scintillator; a 2.5 cm dia, ∼0.7 mm resolution, microchannel-plate area PSD with ⁶Li-glass scintillator; a 20 cm x 20 cm, ∼5 mm resolution, ³He proportional counter area PSD; a 40 cm x 40 cm, ∼4 mm resolution, ³He proportional counter area PSD; a flat 25 cm long, ∼1.6 mm resolution, ³He proportional counter linear PSD; and 160 cylindrical ³He proportional counter linear PSDs, each of which is 1.27 cm in dia. and 60 cm long and has ∼14 mm resolution. In addition to these PSDs, ∼750 standard cylindrical ³He proportional counters of various sizes are utilized on IPNS instruments, and ∼20 BF₃ pulsed ion chambers are in use as beam monitors. This paper discusses these various detectors and associated electronics, with emphasis on the instrumental specifications and the reasons for the selection of the different types of detectors. Observed performance of these detectors is also discussed. (author)

[en] We briefly describe the layout and operation of the two chopper experiments at IPNS-I. The recent measurement on solid ₄He by Hilleke et al. provides examples of time-of-flight data from the Low Resolution Chopper Spectrometer

No abstract available

[en] Several of the instruments at the Intense Pulsed Neutron Source (IPNS) at Argonne use rotating Fermi choppers. The techniques used to control the speed and phase of these rotating devices are discussed

[en] Phonon spectra are obtained using inelastic neutron scattering by polycrystals of the Chevrel-phase superconductors SnMo₆S₈, PbMo₆S₈, Pb₁.₂Mo₆Se₈, and Mo₆Se₈. Modes associated with Sn (or Pb) atomic displacements are identified and acoustic softening is observed for SnMo₆S₈. Anharmonicity and the superconductivity are discussed utilizing the molecular-crystal concept

[en] A multi-detector chopper spectrometer enables measurements of the scattering function S(Q,E) to be made over a wide range of momentum and energy transfer (Q,E). The application of pulsed-source chopper spectrometers for inelastic measurements at thermal and epithermal energies (50 meV < E < 1000 meV) is well known. Recently at IPNS, we have extended the energy-transfer region down to about 0.5 meV with a resolution of the order of 150 μeV. It is made possible by utilizing the cold-neutron incident spectrum of the 100 K methane moderator in conjunction with a dual beryllium-body rotor system. Neutron incident energies can be changed efficiently over the 4 to 1000 meV region while maintaining an undisturbed sample environment. We describe the operation of the IPNS chopper spectrometers (HRMECS and LRMECS), the instrumental resolution and the background-suppression performance. The capability of measuring inelastic features from 0.5 to 100 meV with an energy resolution of ΔE/E₀ = 2.5% is demonstrated by experimental results of crystal-field excitation spectra of a high-Tc superconductor ErBa₂Cu₃O₇. Preliminary data of quasielastic scattering from a room-temperature molten salt AlCl₃-EMIC are presented

[en] The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a major new user-oriented facility which is now coming on line for basic research in neutron scattering and neutron radiation damage. This paper describes the data-acquisition system which will handle data acquisition and instrument control for the time-of-flight neutron-scattering instruments at IPNS. This discussion covers the scientific and operational requirements for this system, and the system architecture that was chosen to satisfy these requirements. It also provides an overview of the current system implementation including brief descriptions of the hardware and software which have been developed