Unique Experimental Facility Research Articles

The Closed Tritium Cycle of the Tritium Laboratory Karlsruhe

The Tritium Laboratory Karlsruhe (TLK) was commissioned with tritium in 1994 and since then has continuously improved its infrastructure and has expanded its experimental activities. With a fully closed tritium cycle and the license to handle 40 g of tritium TLK is an almost unique experimental facility. More than 10 glove box systems with a total volume of about 125 m3 are operated to house experiments and infrastructure facilities on an area of more than 1000 m2. Today TLK has about 23 g of tritium on site. The paper describes the closed tritium loop of the TLK infrastructure and its links to different experiments. Some experience gained during operation of TLK is also presented.

Development of a tagged neutron facility at intermediate energies

A unique experimental facility has been developed to measure absolute neutron scattering cross-sections through the use of tagged intermediate-energy neutrons. The neutrons are produced via the reaction p+d→n+2p with an electron-cooled circulating proton beam of 200 MeV bombarding energy incident on a deuterium gas jet target. The “tagging” of the neutrons is accomplished by detection of the associated recoil protons in an array of silicon microstrip detectors located in vacuum. The detection of two protons in coincidence signals the production of a neutron, while energy and position measurements on the recoil protons allow for reconstruction of the four-momentum of the neutron, and its impact position on a secondary target, on an event-by-event basis. Performance characteristics of this facility are presented, and its future application to an absolute measurement of the np elastic scattering cross-section is described.

Experimental observations of spontaneous breaking of reflectional symmetry in turbulent flow

A unique experimental facility along with unique methods of measurement of vorticity, helicity and related quantities were used in order to obtain the following main results. Strong experimental evidence in favour of the existence of the phenomenon of spontaneous reflectional symmetry breaking (SRSB) in turbulent flows with initial and boundary conditions, which are nominally reflectionally symmetrical. In contrast to widespread expectation, this SRSB is exhibited not only in production of nonzero mean helicity, but in a number of more subtle effects related to spectrally and spatially localized SRSB. We observed qualitatively different cases of SRSB exhibited in large and small scales separately and concomitantly with helicity of different signs at different scales and, in particular, cases with SRSB and vanishing mean helicity. Finally, in some cases the flow was almost perfectly reflectionally symmetrical, possessing an almost vanishing cospectrum. A surprisingly strong variability of this phenomenon was observed in contrast with ‘conventional‘ characteristics, which exhibited regular behaviour. On the basis of a large number of different results our conclusion is that the variability of parameters characterizing SRSB is an intrinsic property at least of some turbulent flows.

The structure of cool flame fronts of pentane, iso-pentane and their mixture

An experimental study of the combustion of two isomers of n-pentane and iso-pentane in laminar cool flames has been carried out. Three flames were studied, one with n-pentane, the second with iso-pentane, and the third with an equimolar mixture of the two isomers. Particular attention has been given to the low temperature region ahead of the hot region of the flame and the cool flame chemistry occurring there. A unique experimental facility has been used to provide access to this cool flame region. Comparisons are made of the structures of the three flames, with particular attention on the different intermediate species produced and the correlations between the fuel molecule structure and the specific intermediates produced.

Investigation of relative effects of mass and damping in vortex-induced vibration of a circular cylinder

Abstract An experimental study of vortex-induced vibration of a circular cylinder was conducted in a unique experimental facility especially designed for low mass and low damping. In this low mass-damping regime, two separate regions of the high amplitude response curve were identified, which we label “upper” and “lower” branches of response. A systematic study including twelve responses was performed to determine the effect of separately varying the nondimensional mass and varying the nondimensional damping. It seems apparent over the range of our present investigation that the mass - damping (the product of mass and damping) collapses well the amplitude of response, indicating two distinct amplitude curves, rather than the single, unique relationship previously supposed.

The Measurement of Boundary Layers on a Compressor Blade in Cascade: Part 1—A Unique Experimental Facility

A unique cascade facility is described which permits the use of laser-Doppler velocimetry (LDV) to measure blade boundary layer profiles. Because of the need for a laser access window, the facility cannot reply on continuous blade pack suction to achieve two-dimensional, periodic flow. Instead, a strong suction upstream of the blade pack is used in combination with tailboards to control the flow field. The distribution of the upstream suction is controlled through a complex baffling system. A periodic, two–dimensional flow field is achieved at a chord Reynolds number of 500,000 and an incidence angle of 5 deg on a highly loaded, double circular arc, compressor blade. Inlet and outlet flow profiles, taken using five-hole probes, and the blade static-pressure distribution are used to document the flow field for use with the LDV measurements (see Parts 2 and 3). Inlet turbulence intensity is measured, using a hot wire, to be 0.18 percent. The static-pressure distribution suggests both separated flow near the trailing edge of the suction surface and an initially laminar boundary layer profile near the leading edge of the pressure surface. Probe measurements are supplemented by sublimation surface visualization studies. The sublimation studies place boundary layer transition at 64.2 ± 3.9 percent chord on the pressure surface, and indicate separation on the suction surface at 65.6 percent ± 3.5 percent chord.

Numerical simulation of three‐dimensional flow in a cavity

AbstractPrevious three‐dimensional simulations of the lid‐driven cavity flow have reproduced only the most general features of the flow. Improvements to a finite difference code, REBUFFS, have made possible the first completely successful simulation of the three‐dimensional lid‐driven cavity flow. The principal improvement to the code was the incorporation of a modified QUICK scheme, a higher‐order upwind finite difference formulation. Results for a cavity flow at a Reynolds number of 3200 have reproduced experimentally observed Taylor‐Görtler‐like vortices and other three‐dimensional effects heretofore not simulated. Experimental results obtained from a unique experimental cavity facility validate the calculated results.

Arcing from coated surfaces: Test facility development and coating deposition using ion plating techniques

Electrical arcing from surfaces is recognized as a potentially deleterious source of plasma impurities for next generation fusion devices. Surface coatings and/or surface conditioning techniques can be applied to reduce the amount of such arc generated impurity atoms. In order to investigate the arcing phenomenon and to assess the arcing performance of various coatings and coating techniques, a unique experimental facility is being developed. This dual purpose facility, developed around an existing ion plating system, allows for the convenient joint studies of arcing phenomenon and coating deposition processes. Completed work includes the construction of an arcing test fixture for study of coating performance in a ‘‘glow discharge to biased surface’’ configuration, and the deposition of selected coating materials using ion plating techniques. Work is continuing toward the development of arc testing and diagnostic instrumentation.

Responses of a Grassland Arthropod Community to Simulated Radioactive Fallout

Responses of an arthropod community to beta and gamma radiation from ${}^{137}{\rm Cs}\text{-tagged}$ simulated fallout and the interaction of radiation with other environment parameters are being investigated in a unique experimental facility at Oak Ridge National Laboratory. Lithium fluoride microdosimeters attached to the thorax and abdomen of insects in a fallout field indicate that closely related organisms may receive significantly different doses owing to differences in habitat or behavior. Significant differences in variation between control and contaminated communities appeared in summer 1970 (P ≤ 0.05), disappeared in autumn 1970, and reappeared in summer 1971 (P ≤ 0.01). Population densities of four arthropod taxa had been significantly (P ≤ 0.05) reduced by summer 1970. By summer 1971, three of these taxa had recovered to control levels, but four additional taxa underwent significant (P ≤ 0.05) reductions in population density. This number of affected populations is not statistically significa...

Friction-Instability: A New Design Parameter for Brakes

A new design parameter, friction-instability, is defined in this paper. Friction-instability is a variation in the coefficient of friction which may occur at any time during the life of a brake lining. A friction-index is defined which measures this variation. A lining which has a high friction index may tend to cause an automobile to swerve either to the right or to the left. A unique experimental facility is described by means of which the friction-instability characteristics of brake linings can be measured. Test results using this facility are presented and interpreted. The friction-index is proposed as a new parameter which should be taken into consideration when brakes are designed and, developed. This index should be particularly useful as a quality control device to insure that machines which use mass-produced braking systems will perform in a safe and effective manner.