ISSN:1044-8632    

DOI:10.1080/10448639008202031

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Welcome to the third issue of Neutron News. Many comments have been received on this new newsletter and all are highly favorable. The editors and their associates are to be congratulated for their successful efforts in reporting activities and highlights of interest to the neutron scattering community. This, no doubt, can be attributed in part to the cooperation of the correspondents from the numerous neutron scattering centers. They are the direct links to our community and they are encouraged to communicate their own and their colleagues ideas, comments and desires to the editors, associate editors and, when appropriate or convenient, to members of the Neutron Diffraction Commission.

ISSN:1044-8632    

DOI:10.1080/10448639008202032

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The first meeting devoted to cold neutron sources was held at the Los Alamos National Laboratory (New Mexico, USA) from March 5–8, 1990. The meeting (cosponsored by Los Alamos and Oak Ridge National Laboratories) was organized as an International Workshop on Cold Neutron Sources, and brought together experts in the fields of reactor and spallation cold-neutron-source design. Eighty-four people from seven countries attended. Because the meeting was the first of its kind in over forty years, much time was spent acquainting participants with past and planned future activities at reactor and spallation facilities worldwide. As a result, the meeting had more of a conference flavor than a workshop; nevertheless, it was deemed successful by all involved. A follow-up meeting was proposed with the date and location to be decided.

ISSN:1044-8632    

DOI:10.1080/10448639008202033

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A symposium on Applied Neutron Scattering was held as part of the Annual UK Solid State Physics Conference at the University of Warwick on December 20, 1989. The idea was bring together scientists from industry, government laboratories and universities who were using neutrons as a non-destructive testing technique. It is appropriate that the invited talks and some of the contributed posters will be published in the ‘Journal of Non-destructive Testing and Evaluation.’

ISSN:1044-8632    

DOI:10.1080/10448639008202034

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:1044-8632    

DOI:10.1080/10448639008202035

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A two-day meeting was held at Argonne on April 16–17, 1990 to celebrate the inauguration of GLAD, a new diffractometer dedicated to measuring the structures of glasses and liquids. It has just come into operation at Argonne's Intense Pulsed Neutron Source (IPNS). The instrument is the first neutron diffractometer optimized for such measurments and takes advantage of the copious supply of short-wavelength neutrons available at a pulsed spallation source such as IPNS. The use of wavelengths as low as 0.1 Å will make it possible to obtain complete diffraction patterns at low scattering angles, and avoid the systematic errors due to absorption and inelasticity effects which have plagued many measurements this kind made upt to now on conventional instruments. Data can be collected simultaneously over a wide range of scattering vector Q, overlapping with the small-angle region at low (0.05 Å−1) and extending out to Q values as high as 50 Å−1, corresponding to very high spatial resolution in the radial distribution functions. A wide range sample environments will be available, including low temperature (10 K), high temperature (1500 K) and, eventually, high pressure.

ISSN:1044-8632    

DOI:10.1080/10448639008202036

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The Intense Pulsed Neutron Source (IPNS) is a pulsed spallation neutron source located at Argonne National Laboratory near Chicago, Illinois in the US. This facility is the outgrowth of a long line of pioneering work on pulsed spallation neutron sources begun at Argonne in the early 1970s. IPNS uses protons accelerated in the Rapid Cycling Synchrotron (RCS) to produce neutrons via the spallation process (effectively a nuclear ‘evaporation’ in which ten to fifty neutrons are released per incident proton) in a heavy-element target. These neutrons are then moderated to produce spectra peaked at thermal or subthermal energies, and directed into beams which serve a variety of instruments. Figure 1 shows a layout of the accelerator and target system, and Figure 2 shows the target/moderator system and the beamlines and instruments currently installed or under development at IPNS.

ISSN:1044-8632    

DOI:10.1080/10448639008202037

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The NRU reactor at Chalk River Laboratories of AECL Research, has provided intense neutron beams since it began operation in 1957. The reactor uses D2O as both moderator and coolant and operates at 125 MW. It presently uses 93% enriched fuel. It has a large core contained in a vessel that is 12 ft in diameter and 10 ft high. The core contains ninety fuel sites and has eight reactor loops and thirty isotope irradiation sites. It also has beam tubes, seven of which are for neutron scattering instruments and one for neutron radiography. The on-line fueling capability of NRU means the reactor does not operate on a fixed-fueling cycle. Rather, shut-downs are scheduled as required by the scientific, engineering or maintenance needs.

ISSN:1044-8632    

DOI:10.1080/10448639008202038

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In type II superconductors, like the new high Tcoxide materials, if you cool acrystal below the superconducting transition in an applied magnetic field, B>Bc1, the system minimizes its free energy by distributing the flux, in units of single flux quanta, on a lattice. This should be a perfect experiment for the loveable neutron with its ability to detect variations of magnetic field in a sample. There exist several studies of these effects in conventional superconductors but, as usual for high Tcsystems, weird and wonderful things are expected. The theoreticians predict: no flux lattice only a glassy state, a lattice at low T which will melt below Tc, entangled-disentangled configurations in the liquid state, a vortex-plasma of flux-lines (whatever that may be) and so on. Its the usual story, we need some experiments to separate fact from highly entertaining theoretical models. However, the experiments are not that easy…

ISSN:1044-8632    

DOI:10.1080/10448639008202039

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

When liquid crystalline molecules (a) are grafted laterally via a spacer (b) on the backbone (c) of a polymer, one obtains a mesomorphic polymer (Figure 1) which will present liquid crystalline phases such as the nematic or the smectic phase (1).

ISSN:1044-8632    

DOI:10.1080/10448639008202040

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor