78 research outputs found
Gaps below strange star crusts
The gap caused by a strong electric field between the quark surface and
nuclear crust of a strange star is studied in an improved model including
gravity and pressure as well as electrostatic forces. The transition from gap
to crust is followed in detail. The properties of the gap are investigated for
a wide range of parameters assuming both color-flavor locked and non
color-flavor locked strange star cores. The maximally allowed crust density is
generally lower than that of neutron drip. Finite temperature is shown to
increase the gap width, but the effect is significant only at extreme
temperatures. Analytical approximations are derived and shown to provide useful
fits to the numerical results.Comment: 12 pages incl. 14 figures. To appear in Physical Review
Signature of deconfinement with spin down compression in cooling hybrid stars
The thermal evolution of neutron stars is coupled to their spin down and the
resulting changes in structure and chemical composition. This coupling
correlates stellar surface temperatures with rotational state as well as time.
We report an extensive investigation of the coupling between spin down and
cooling for hybrid stars which undergo a phase transition to deconfined quark
matter at the high densities present in stars at low rotation frequencies. The
thermal balance of neutron stars is re-analyzed to incorporate phase
transitions and the related latent heat self-consistently, and numerical
calculations are undertaken to simultaneously evolve the stellar structure and
temperature distribution. We find that the changes in stellar structure and
chemical composition with the introduction of a pure quark matter phase in the
core delay the cooling and produce a period of increasing surface temperature
for strongly superfluid stars of strong and intermediate magnetic field
strength. The latent heat of deconfinement is found to reinforce this signature
if quark matter is superfluid and it can dominate the thermal balance during
the formation of a pure quark matter core. At other times it is less important
and does not significantly change the thermal evolution.Comment: 30 pages, 13 figures. Updated to match the version published in Ap
Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas
Inference of -particle density profiles from ITER collective Thomson scattering
The primary purpose of the collective Thomson scattering (CTS) diagnostic at
ITER is to measure the properties of fast-ion populations, in particular those
of fusion-born -particles. Based on the present design of the
diagnostic, we compute and fit synthetic CTS spectra for the ITER baseline
plasma scenario, including the effects of noise, refraction, multiple fast-ion
populations, and uncertainties on nuisance parameters. As part of this, we
developed a model for CTS that incorporates spatial effects of
frequency-dependent refraction. While such effects will distort the measured
ITER CTS spectra, we demonstrate that the true -particle densities can
nevertheless be recovered to within ~10% from noisy synthetic spectra, using
existing fitting methods that do not take these spatial effects into account.
Under realistic operating conditions, we thus find the predicted performance of
the ITER CTS system to be consistent with the ITER measurement requirements of
a 20% accuracy on inferred -particle density profiles at 100 ms time
resolution.Comment: 17 pages, 11 figures. Accepted for publication in Nucl. Fusio
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