Ground State Properties of One Dimensional S=1/2 Heisenberg Model with Dimerization and Quadrumerization

The one dimensional S=1/2 Heisenberg model with dimerization and quadrumerization is studied by means of the numerical exact diagonalization of finite size systems. Using the phenomenological renormalization group and finite size scaling law, the ground state phase diagram is obtained in the isotropic case. It exhibits a variety of the ground states which contains the S=1 Haldane state, S=1 dimer state and S=1/2 dimer state as limiting cases. The gap exponent $\nu$ is also calculated which coincides with the value for the dimerization transition of the isotropic Heisenberg chain. In the XY limit, the phase diagram is obtained analytically and the comparison is made with the isotropic case.Comment: 4 pages, 7 figure

Spatial Resolution of the Heavy Ion Beam Probe on LHD

he sizes of sample volumes, which determine the spatial resolution, are estimated by trajectory calculation for the heavy ion beam probe on LHD. The beam width, the divergence, and the beam energy difference are taken into account. From the points of view of the spatial resolution and the signal intensity, parallel beam is suitable for the injection beam. The size of the sample volume by the parallel beam with 10mm diameter is 42 mm. It is sufficient to measure the potential profile in the internal transport barrier in the LHD plasma. Taking into account the spatial profile of the beam, the spatial resolution will be better than 42 mm

Status of the heavy ion beam probe system in the Large Helical Device

A heavy ion beam probe (HIBP) system has been installed into the Large Helical Device (LHD) to measure the spatial profile of the plasma potential and density fluctuations. The optimization of the HIBP system, especially the beam injector, is described. The negative ion beam is required for the MeV beam production in a tandem accelerator. A sputter-type heavy negative ion source has been developed as an intense Au^? beam source to produce Au^+ beams with energy in the MeV range. The extraction electrodes and the Einzel lens system of the ion source have been designed taking into account the beam optics, and installed into the real machine. Throughout the plasma diagnostics on LHD experiments, the consumptions of vaporized caesium and gold target are being characterized for practical operations. In addition, the experimental charge fractions are compared with the theoretical fractions for understanding the charge-changing behavior of Au^? ions and optimizing the fraction of Au^+ ions at the exit of the tandem accelerator of the HIBP syste

The photometric properties of a vast stellar substructure in the outskirts of M33

We have surveyed $\sim40$sq.degrees surrounding M33 with CFHT MegaCam in the g and i filters, as part of the Pan-Andromeda Archaeological Survey. Our observations are deep enough to resolve the top 4mags of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low-surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations of this feature are consistent with an old population with $<[Fe/H]>\sim-1.6$dex and an interquartile range in metallicity of $\sim0.5$dex. We construct a surface brightness map of M33 that traces this feature to $\mu_V\simeq33$mags\,arcsec$^{-2}$. At these low surface brightness levels, the structure extends to projected radii of $\sim40$kpc from the center of M33 in both the north-west and south-east quadrants of the galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns with the orientation of the HI disk warp. We calculate a lower limit to the integrated luminosity of the structure of $-12.7\pm0.5$mags, comparable to a bright dwarf galaxy such as Fornax or AndII and slightly less than $1\$ of the total luminosity of M33. Further, we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the HI disk that occurs at similar azimuth to the warp in HI. The data also hint at a low-level, extended stellar component at larger radius that may be a M33 halo component. We revisit studies of M33 and its stellar populations in light of these new results, and we discuss possible formation scenarios for the vast stellar structure. Our favored model is that of the tidal disruption of M33 in its orbit around M31.Comment: Accepted for publication in ApJ. 17 figures. ApJ preprint forma

Electron Loss Cross Sections for a Heavy Ion Beam Probe

Electron loss cross sections of Au+ and Au2+ by electron and proton impact are calculated by using respectively the Lotz formula and the LOSS and CAPTURE computer codes. The corresponding rate coefficients have also been calculated. Using this information, the signal levels of heavy ion beam probe in the Large Helical Device are estimated. The calculated beam currents at the detector position are compared with the detected beamcurrents in the MeV energy range for a plasma electron density of 1 × 1019 m?3 and electron temperature of 1.5 keV. The obtained cross section / rate coefficient data can also be used for reconstruction of electron density and temperature profiles