Tetra­guanidinium bis­[citrato(3−)]cuprate(II) dihydrate

The asymmetric unit of the title compound, (CH6N3)4[Cu(C6H5O7)2]·2H2O, contains one-half of a centrosymmetric CuII complex anion, two guanidinium cations and a water mol­ecule. The CuII ion, lying on a crystallographic inversion center, is hexa­coordinated with two citrate anions in a distorted octahedral geometry. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, mol­ecules are linked into a three-dimensional framework by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds

Experimental evidence for an intermediate phase in the multiferroic YMnO3

We have studied YMnO$_{3}$ by high-temperature synchrotron X-ray powder diffraction, and have carried out differential thermal analysis and dilatometry on a single crystal sample. These experiments show two phase transitions at about 1100K and 1350K, respectively. This demonstrates the existence of an intermediate phase between the room temperature ferroelectric and the high temperature centrosymmetric phase. This study identifies for the first time the different high-temperature phase transitions in YMnO$_{3}$.Comment: 10 pages 5 figures. New version, Additional data, Journal of Physics: Condensed Matter, in Pres

Simultaneous Measurement of Normal and Friction Forces Using a Cantilever-Based Optical Interfacial Force Microscope

We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope (COIFM) technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of one nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges

Bunch Length Measurements at the CEBAF Injector at 130 kV

In this work, we investigated the evolution in bunch length of beams through the CEBAF injector for low to high charge per bunch. Using the General Particle Tracer (GPT), we have simulated the beams through the beamline of the CEBAF injector and analyzed the beam to get the bunch lengths at the location of chopper. We performed these simulations with the existing injector using a 130 kV gun voltage. Finally, we describe measurements to validate these simulations. The measurements have been done using chopper scanning technique for two injector laser drive frequency modes: one with 500 MHz, and another with 250 MHz

CEBAF Injector Model for K\u3csub\u3eL\u3c/sub\u3e Beam Conditions

The Jefferson Lab KL experiment will run at the Continuous Electron Beam Accelerator Facility with a much lower bunch repetition rate (7.80 or 15.59 MHz) than nominally used (249.5 or 499 MHz). While the proposed average current of 2.5 - 5.0 µA is relatively low compared to the maximum CEBAF current of approximately 180 µA, the corresponding bunch charge is atypically high for CEBAF injector operation. In this work, we investigated the evolution and transmission of low-rep-rate, high-bunch-charge (0.32 to 0.64 pC) beams through the CEBAF injector. Using the commercial software General Particle Tracer, we have simulated and analyzed the beam characteristics for both values of bunch charge. We performed these simulations with the existing injector using a 130 kV gun voltage. We have calculated and measured the transmission as a function of the photocathode laser spot size and pulse length. We report on the findings of these simulations and optimum parameters for operating the experiment