Suite Of Measurement Techniques Research Articles

Raman temperature and density measurements in supersonic jets

Prediction of flow-field properties in supersonic jets using computational fluid dynamics (CFD) code predictions has become routine; however, obtaining accurate solutions becomes more challenging when there is a significant temperature difference between the jet core and the ambient air and/or compressibility effects are significant. Benchmark sets of flow field property data are required in order to assess current CFD capabilities and develop better modeling approaches for these turbulent flow fields where accurate calculation of temperatures and turbulent heat flux is important. Particle Image Velocimetry, spontaneous rotational Raman scattering spectroscopy, and Background-Oriented Schlieren (BOS) have been previously used to acquire measurements of the mean and root-mean-square (rms) velocities, the mean and rms gas temperatures, and density gradients in subsonic jet flows and film cooling flows. In this work, the ability to measure density is added to the list of measurands available using the acquired Raman spectra. The suite of measurement techniques are now applied to supersonic jet flows. The computation of the local gas pressure in the potential core of an over-expanded jet is demonstrated using the Raman measured gas temperature and density. Additionally, a unique density feature in temperature matched, perfectly expanded jet flow shear layers identified using BOS was verified using the Raman measurement technique. These non-intrusive flow measurements are compared against RANS predictions of the supersonic jet flow properties as a means of assessing their prediction accuracy.Graphic abstract

High-pressure phase of CrSb2 : A new quasi-one-dimensional itinerant magnet with competing interactions

We have synthesized the high-pressure form of $\mathrm{CrS}{\mathrm{b}}_{2}$ with $\mathrm{CuA}{\mathrm{l}}_{2}$-type structure under 7 GPa and 700 \ifmmode^\circ\else\textdegree\fi{}C, and characterized its structural, transport, and magnetic properties by a suite of measurement techniques over a broad range of temperature, magnetic field, and pressure. In addition to previously reported ferromagnetic (FM) transition at ${T}_{\mathrm{C}}\ensuremath{\approx}160$ K, we discover another antiferromagnetic spin-density-wave (SDW) transition at ${T}_{\mathrm{s}}\ensuremath{\approx}90$ K, which is characterized by FM sheets of spins in the $ab$ plane that vary along the $c$ axis as determined by neutron powered diffraction. Pronounced anomalies around these two magnetic transitions are visible only in the lattice parameter $c$, signaling a strong spin-lattice coupling along the -Cr-Cr-Cr- infinite linear chain. We find that the application of magnetic field can suppress the SDW phase and stabilize the FM state down to the lowest temperature above ${\ensuremath{\mu}}_{0}{H}_{\mathrm{c}}\ensuremath{\approx}3$ T, around which a peculiar non-Fermi-liquid behavior with reduced effective mass emerges. On the other hand, the application of high pressure induces complex evolution of the magnetic states, i.e., the FM order is lowered while the SDW order is enhanced quickly until they merge together into a single antiferromagnetic transition, which is suppressed completely at ${P}_{\mathrm{c}}\ensuremath{\approx}9$ GPa. We observe near ${P}_{\mathrm{c}}$ non-Fermi-liquid behavior and enhancement of effective mass, which indicates the possible occurrence of magnetic quantum critical point. No superconductivity was observed down to 2 K around ${P}_{\mathrm{c}}$.

Meeting Reports: International Workshop on Diamond Single Crystals for 3rd and 4th Generation X-ray Sources

Diamonds attract enormous interest as gemstones. This rather frivolous “application” is based on their optical properties and contributes about 95 percent of the turnover in the diamond industry. Another area of application, which may now be seen as a crude application, is a diamond-tipped tool for the abrasive and cutting industries. These applications exploit the hardness and wear resistance of diamond, and dominate the demand for synthetic diamond production. These applications do not place the most stringent requirements on the quality of diamond. As has become clear at this workshop, a crucial new role for diamond in an ultra-high technology area is emerging. Diamond devices at synchrotrons require near– theoretical values of perfection of the diamond lattice. This material is vital to the continued increase in beam performance as well as the expansion of the suite of measurement techniques of modern synchrotrons. An international workshop on “diamond single crystals for 3rd and 4th generation X-ray sources” was held in Grenoble, France, on May 24–25, 2004.