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[en] We present the experimental results for a comparison between pulsed and continuous transfer of cold ⁸⁷Rb atoms between a vapor chamber magneto-optical trap (VC-MOT) and an ultra-high vacuum magneto-optical trap (UHV-MOT) when using a resonant push beam. We find that employing repetitive cycles of a pulsed and unfocused push beam on an unsaturated VC-MOT cloud results in a significantly higher number of atoms transferred to the UHV-MOT than the number obtained with a continuous push beam focused on a continuous VC-MOT. In pulsed transfer, we find that both the VC-MOT loading duration and the push beam duration play important roles in the transfer process and govern the number of atoms transferred to the UHV-MOT. The parameters and processes affecting the transfer have been investigated and are discussed.

[en] Recent theoretical investigations have unveiled a rich structure in the quantum chromodynamics phase diagram, which consists of quark-gluon plasma and the hadronic phases but also supports the existence of a crossover transition ending at a critical end point (CEP). We find a too large variation in the determination of the coordinates of the CEP in the temperature (T) baryon chemical potential (μ_B) plane; and, therefore, its identification in the current heavy-ion experiments becomes debatable. Here we use an equation of state for a deconfined quark-gluon plasma using a thermodynamically-consistent quasiparticle model involving noninteracting quarks and gluons having thermal masses. We further use a thermodynamically-consistent excluded-volume model for the hadron gas, which was recently proposed by us. Using these equations of state, a first-order deconfining phase transition is constructed using Gibbs's criteria. This leads to an interesting finding that the phase transition line ends at a critical end point (CEP) beyond which a crossover region exists. Using our thermal hadron gas model, we obtain a chemical freeze out curve, and we find that the CEP lies in close proximity to this curve as proposed by some authors. The coordinates of CEP are found to lie within the reach of Relativistic heavy-ion collider experiment.

[en] Location of critical point and mapping the QCD phase boundary still exists as one of the most interesting and studied problems of heavy-ion physics. A new equation of state (EOS) for a gas of extended baryons and pointlike mesons is presented here which accounts for the repulsive hard-core interactions arising due to the geometrical size of the baryons. A first-order deconfining phase transition is obtained using Gibbs' equilibrium criteria and a bag model EOS for the weakly interacting quark matter. It is interesting to find that the phase transition line ends at a critical point beyond which a crossover region exists between hot-dense meson gas and quark-antiquark gluon matter. Our curve closely resembles in shape the predictions of the available lattice gauge calculations and also reproduces the conjectured phase boundary.

[en] We present a systematic study of production of strange and non-strange hadron yields and their ratios obtained in various experiments using our thermodynamically consistent excluded-volume model. We also analyze the production of light nuclei, hypernuclei and their antinuclei in terms of our excluded-volume model over a broad energy range starting from Alternating Gradient Synchrotron (AGS) to Large Hadron Collider (LHC) energies. Further, we extend our model for studying rapidity spectra of hadrons produced in heavy-ion collisions

[en] We present studies on modifications in the temperature, number density and phase-space density when a laser-cooled atom cloud from optical molasses is trapped in a quadrupole magnetic trap. Theoretically, for a given temperature and size of the cloud from the molasses, the phase-space density in the magnetic trap is shown first to increase with increasing magnetic field gradient and then to decrease with it after attaining a maximum value at an optimum value of the magnetic-field gradient. The experimentally-measured variation in the phase-space density in the magnetic trap with changing magnetic field gradient is shown to exhibit a similar trend. However, the experimentally-measured values of the number density and the phase-space density are much lower than the theoretically-predicted values. This is attributed to the experimentally-observed temperature in the magnetic trap being higher than the theoretically-predicted temperature. Nevertheless, these studies can be useful for setting a higher phase-space density in the trap by establishing an optimal value of the field gradient for a quadrupole magnetic trap.

[en] The nonlinear propagation of low-frequency waves in a strongly coupled dusty plasma medium is studied theoretically in the framework of the phenomenological generalized hydrodynamic (GH) model. A set of simplified model nonlinear equations are derived from the original nonlinear integrodifferential form of the GH model by employing an appropriate physical ansatz. Using standard perturbation techniques characteristic evolution equations for finite small amplitude waves are then obtained in various propagation regimes. The influence of viscoelastic properties arising from dust correlation contributions on the nature of nonlinear solutions is discussed. The modulational stability of dust acoustic waves to parallel perturbation is also examined and it is shown that dust compressibility contributions influenced by the Coulomb coupling effects introduce significant modification in the threshold and range of the instability domain.

[en] Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope's Spectropolarimeter (SP) on board Hinode. Besides basing our model calculations on HMI data, we use both SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate how a binning of high-resolution data affects the model outcome. The resulting three-dimensional magnetic fields are compared in terms of magnetic energy content and magnetic topology. We find stronger magnetic fields in the SP data, translating into a higher total magnetic energy of the SP models. The net Lorentz forces of the HMI and SP lower boundaries verify their force-free compatibility. We find substantial differences in the absolute estimates of the magnetic field energy but similar relative estimates, e.g., the fraction of excess energy and of the flux shared by distinct areas. The location and extension of neighboring connectivity domains differ and the SP model fields tend to be higher and more vertical. Hence, conclusions about the magnetic connectivity based on force-free field models are to be drawn with caution. We find that the deviations of the model solution when based on the lower-resolution SP data are small compared to the differences of the solutions based on data from different instruments.

[en] Stainless steel (SS) and Copper are very suitable structural metals for fabrication of UHV vessels. INDUS-1 is an electron storage ring, with 450 MeV electron energy. A new Radio Frequency (RF) cavity was fabricated for INDUS-1, with copper plating on SS. The main factor deciding the vacuum compatibility of the surface is the specific outgassing rate at room temperature as well as at the operating temperature. Surface properties are extremely important in this case. i.e., surface finish should be maintained without any blisters and micro cracks, after baking. In order to evaluate these factors, one sample was prepared (SS pipe plated with copper) and tested with simulated conditions in UHV environment. This paper gives the details of the experiments and the results on specific outgassing rate of the copper plated SS sample in different conditions, namely, at room temperature and after baking at different temperatures

[en] A molecular dynamics (MD) simulation method has been used to predict the interfacial behavior of single-wall carbon nanotube (CNT) reinforced aluminum (Al) composites. At the interface of the CNT and the Al, only van der Waals interaction was considered. The effect of CNT volume fraction and chirality on CNT pull-out has been studied for the first time with a proper distinction between them. The length of all the CNTs was kept constant throughout the study. The approach used in this work was validated with an earlier study. The present study revealed that the average pull-out load was found proportional to both the CNT volume fraction as well as the diameter. The smaller diameter CNTs improved the interfacial shear strength (ISS) at lower volume fraction significantly in comparison to that of the larger diameter CNTs. The highest improvement of 38.7% was observed in the ISS during pull-out of (6, 6) CNT at a CNT volume fraction of 3.17%. The average energy increment was found to be increasing with CNT volume fraction and was higher for larger diameter CNTs. (paper)