A Multinuclear NMR Approach to the Study of the Lyotropic System CTAB-D20

CTAB-D2O liquid crystalline phase (CTAB = cetyltrimethylammonium bromide), type I according to magnetic anisotropy, has been investigated by means of 2H, 14N and 17O NMR at variable temperature. The residual quadrupolar splittings of ali these nuclei evidenced the alignment of the phase in the magnetic field. The interpretation of the data of D2O quadrupolar nuclei, commonly used in the Study of lyotropic liquid crystalline phases, is complicated because of water reorientation, exchange processes and variations of the hydration degree. The 14N quadrupolar splittings are much more reliable indicators of the orientation of surfactant aggregates since their interpretation in terms of the order parameter is straightforward in this case because the nitrogen nucleus is subject to an electric field gradient of axial symmetry and resides just in the head of the amphiphile

Loss budget of a setup for measuring mechanical dissipations of silicon wafers between 300 and 4 K

A setup for measuring mechanical losses of silicon wafers has been fully characterized from roomtemperature to 4 K in the frequency range between 300 Hz and 4 kHz: it consists of silicon waferswith nodal suspension and capacitive and optical vibration sensors. Major contributions tomechanical losses are investigated and compared with experimental data scanning the fulltemperature range; in particular, losses due to the thermoelastic effect and to the wafer clamp aremodeled via finite element method analysis; surface losses and gas damping are also estimated. Thereproducibility of the measurements of total losses is also discussed and the setup capabilities formeasuring additive losses contributed by thin films deposited on the wafers or bonding layers. Forinstance, assuming that additive losses are due to an 80-nm-thick wafer bond layer with Youngmodulus about ten times smaller than that of silicon, we achieve a sensitivity to bond losses at thelevel of 510−3 at 4 K and at about 2 kHz

Low temperature mechanical dissipation measurements of silicon and silicon carbide as candidate material for DUAL detector

We present the results of measurements of mechanical dissipation in silicon and silicon carbide samples within 2-300 K range of temperature. These materials are possible candidates for the sensitive mass of DUAL detector. We have investigated sintered and infiltrated Silicon-Carbide (SiC) and P-doped Silicon (Si)in flat plates and cantilevers. Moreover the dissipation of bonded P-doped silicon wafers is scheduled for measurement in the 2-300 K range for the next cryogenic run. We tested a nodal suspension with sapphire and inox steel spheres for flat plates within the same temperature range. We develop two different kinds of capacitive readout: electrostatic comb one for semiconductor silicon and plane capacitor-like for conductor silicon carbide. Moreover an optical lever readout was employed to measure loss angle on SiC cantilevers and silicon disks