355 research outputs found
Semi-automatic rubble counting system for superheated droplet detectors
Neutron dose rate measurements are normally performed by means of PADC, CR-39 and TLD detectors.
Although, none of these devices can give instant reading of the neutron dose, recently new kind of detectors are
being developed, based on the formation of tiny drops in a superheated liquid suspended in a polymer or gel
solution, called superheated droplet detector (SDD) or also as bubble detectors (BD), with no response for
gamma radiation. This work describes the experimental setup and the developed procedures for acquiring and
processing digital images obtained with bubble detector spectrometer (BDS), developed by Bubble Technology
Industries, for personal neutron dosimeter and/or neutron energy fluence measurements in nuclear facilities. The
results of the neutron measurements obtained during the F-18 production, at the RDS-111 cyclotron, are
presented. These neutron measurements were the first ones with this type of BDS detectors in a particle
accelerator facility in Brazil and it was very important to estimate neutron dose rate received by occupationally
exposed individuals
From Coherent Modes to Turbulence and Granulation of Trapped Gases
The process of exciting the gas of trapped bosons from an equilibrium initial
state to strongly nonequilibrium states is described as a procedure of symmetry
restoration caused by external perturbations. Initially, the trapped gas is
cooled down to such low temperatures, when practically all atoms are in
Bose-Einstein condensed state, which implies the broken global gauge symmetry.
Excitations are realized either by imposing external alternating fields,
modulating the trapping potential and shaking the cloud of trapped atoms, or it
can be done by varying atomic interactions by means of Feshbach resonance
techniques. Gradually increasing the amount of energy pumped into the system,
which is realized either by strengthening the modulation amplitude or by
increasing the excitation time, produces a series of nonequilibrium states,
with the growing fraction of atoms for which the gauge symmetry is restored. In
this way, the initial equilibrium system, with the broken gauge symmetry and
all atoms condensed, can be excited to the state, where all atoms are in the
normal state, with completely restored gauge symmetry. In this process, the
system, starting from the regular superfluid state, passes through the states
of vortex superfluid, turbulent superfluid, heterophase granular fluid, to the
state of normal chaotic fluid in turbulent regime. Both theoretical and
experimental studies are presented.Comment: Latex file, 25 pages, 4 figure
Spin-gravity coupling and gravity-induced quantum phases
External gravitational fields induce phase factors in the wave functions of
particles. The phases are exact to first order in the background gravitational
field, are manifestly covariant and gauge invariant and provide a useful tool
for the study of spin-gravity coupling and of the optics of particles in
gravitational or inertial fields. We discuss the role that spin-gravity
coupling plays in particular problems.Comment: 18 pages, 1 figur
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