1,995 research outputs found
Cosmic microwave background power spectrum estimation with the destriping technique
Extraction of the CMB (Cosmic Microwave Background) angular power spectrum is
a challenging task for current and future CMB experiments due to the large data
sets involved. Here we describe an implementation of MASTER (Monte carlo
Apodised Spherical Transform EstimatoR) which exploits the destriping technique
as a map-making method. In this method a noise estimate based on destriped
noise-only MC (Monte Carlo) simulations is subtracted from the pseudo angular
power spectrum. As a working case we use realistic simulations of the PLANCK
LFI (Low Frequency Instrument). We found that the effect of destriping on a
pure sky signal is minimal and requires no correction. Instead we found an
effect related to the distribution of detector pointings, which affects the
high multipole part of the power spectrum. We correct for this by subtracting a
``signal bias'' estimated by MC simulations. We also give analytical estimates
for this signal bias. Our method is fast and accurate enough (the estimator is
un-biased and errors are close to theoretical expectations for maximal
accuracy) to estimate the CMB angular power spectra for current and future CMB
space missions. This study is related to PLANCK LFI activities.Comment: 16 pages, 23 figures, submitted to MNRA
Calculating the 3D magnetic field of ITER for European TBM studies
The magnetic perturbation due to the ferromagnetic test blanket modules
(TBMs) may deteriorate fast ion confinement in ITER. This effect must be
quantified by numerical studies in 3D. We have implemented a combined finite
element method (FEM) -- Biot-Savart law integrator method (BSLIM) to calculate
the ITER 3D magnetic field and vector potential in detail. Unavoidable geometry
simplifications changed the mass of the TBMs and ferritic inserts (FIs) up to
26%. This has been compensated for by modifying the nonlinear ferromagnetic
material properties accordingly. Despite the simplifications, the computation
geometry and the calculated fields are highly detailed. The combination of
careful FEM mesh design and using BSLIM enables the use of the fields
unsmoothed for particle orbit-following simulations. The magnetic field was
found to agree with earlier calculations and revealed finer details. The vector
potential is intended to serve as input for plasma shielding calculations.Comment: In proceedings of the 28th Symposium on Fusion Technolog
Euclid: Searching for pair-instability supernovae with the Deep Survey
Pair-instability supernovae are theorized supernovae that have not yet been observationally confirmed. They are predicted to exist in low-metallicity environments. Because overall metallicity becomes lower at higher redshifts, deep near-infrared transient surveys probing high-redshift supernovae are suitable to discover pair-instability supernovae. The Euclid satellite, which is planned launch in 2023, has a near-infrared wide-field instrument that is suitable for a high-redshift supernova survey. The Euclid Deep Survey is planned to make regular observations of three Euclid Deep Fields (40 deg(2) in total) spanning Euclid's six-year primary mission period. While the observations of the Euclid Deep Fields are not frequent, we show that the predicted long duration of pair-instability supernovae would allow us to search for high-redshift pair-instability supernovae with the Euclid Deep Survey. Based on the current observational plan of the Euclid mission, we conduct survey simulations in order to estimate the expected numbers of pair-instability supernova discoveries. We find that up to several hundred pair-instability supernovae at z less than or similar to 3.5 can be discovered within the Euclid Deep Survey. We also show that pair-instability supernova candidates can be efficiently identified by their duration and color, which can be determined with the current Euclid Deep Survey plan. We conclude that the Euclid mission can lead to the first confirmation of pair-instability supernovae if their event rates are as high as those predicted by recent theoretical studies. We also update the expected numbers of superluminous supernova discoveries in the Euclid Deep Survey based on the latest observational plan.Peer reviewe
- …