| 1. |
- Meech, K. J., et al.
(författare)
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EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
- 2011
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Ingår i: Astrophysical Journal Letters. - London : IOP. - 2041-8213 .- 2041-8205. ; 734:L1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4?hr. Starting in 2010 August the period changed from 16.6?hr to near 19?hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO 2 -driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.
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| 2. |
- Wright, Gillian, et al.
(författare)
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The Mid-infrared Instrument for JWST and Its In-flight Performance
- 2023
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Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 135:1046
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Tidskriftsartikel (refereegranskat)abstract
- The Mid-Infrared Instrument (MIRI) extends the reach of the James Webb Space Telescope (JWST) to 28.5 μm. It provides subarcsecond-resolution imaging, high sensitivity coronagraphy, and spectroscopy at resolutions of λ/Δλ ∼ 100-3500, with the high-resolution mode employing an integral field unit to provide spatial data cubes. The resulting broad suite of capabilities will enable huge advances in studies over this wavelength range. This overview describes the history of acquiring this capability for JWST. It discusses the basic attributes of the instrument optics, the detector arrays, and the cryocooler that keeps everything at approximately 7 K. It gives a short description of the data pipeline and of the instrument performance demonstrated during JWST commissioning. The bottom line is that the telescope and MIRI are both operating to the standards set by pre-launch predictions, and all of the MIRI capabilities are operating at, or even a bit better than, the level that had been expected. The paper is also designed to act as a roadmap to more detailed papers on different aspects of MIRI.
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| 3. |
- Sato, T., et al.
(författare)
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Overview of particle and heavy ion transport code system PHITS
- 2015
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 82, s. 110-115
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Tidskriftsartikel (refereegranskat)abstract
- A general purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS, is being developed through the collaboration of several institutes in Japan and Europe. The Japan Atomic Energy Agency is responsible for managing the entire project. PHITS can deal with the transport of nearly all particles, including neutrons, protons, heavy ions, photons, and electrons, over wide energy ranges using various nuclear reaction models and data libraries. It is written in Fortran language and can be executed on almost all computers. All components of PHITS such as its source, executable and data-library files are assembled in one package and then distributed to many countries via the Research Organization for Information Science and Technology, the Data Bank of the Organization for Economic Co-operation and Development's Nuclear Energy Agency, and the Radiation Safety Information Computational Center. More than 1500 researchers have been registered as PHITS users, and they apply the code to various research and development fields such as nuclear technology, accelerator design, medical physics, and cosmic-ray research. This paper briefly summarizes the physics models implemented in PHITS, and introduces some important functions useful for specific applications, such as an event generator mode and beam transport functions. (C) 2014 Elsevier Ltd. All rights reserved.
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| 4. |
- Sato, T., et al.
(författare)
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Overview of Particle and Heavy Ion Transport Code System PHITS
- 2014
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Ingår i: Sna + Mc 2013 - Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo. - Les Ulis, France : EDP Sciences. ; , s. article no 06018-
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Konferensbidrag (refereegranskat)abstract
- A general purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS, is being developed through the collaboration of several institutes in Japan and Europe. The Japan Atomic Energy Agency is responsible for managing the entire project. PHITS can deal with the transport of nearly all particles, including neutrons, protons, heavy ions, photons, and electrons, over wide energy ranges using various nuclear reaction models and data libraries. It is written in Fortran language and can be executed on almost all computers. All components of PHITS such as its source, executable and data-library files are assembled in one package and then distributed to many countries via the Research organization for Information Science and Technology, the Data Bank of the Organization for Economic Co-operation and Development's Nuclear Energy Agency, and the Radiation Safety Information Computational Center. More than 1,000 researchers have been registered as PHITS users, and they apply the code to various research and development fields such as nuclear technology, accelerator design, medical physics, and cosmic-ray research. This paper briefly summarizes the physics models implemented in PHITS, and introduces some important functions useful for specific applications, such as an event generator mode and beam transport functions.
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| 5. |
- Sato, T., et al.
(författare)
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Particle and Heavy Ion Transport code System, PHITS, version 2.52
- 2013
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Ingår i: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 50:9, s. 913-923
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Tidskriftsartikel (refereegranskat)abstract
- An upgraded version of the Particle and Heavy Ion Transport code System, PHITS2.52, was developed and released to the public. The new version has been greatly improved from the previously released version, PHITS2.24, in terms of not only the code itself but also the contents of its package, such as the attached data libraries. In the new version, a higher accuracy of simulation was achieved by implementing several latest nuclear reaction models. The reliability of the simulation was improved by modifying both the algorithms for the electron-, positron-, and photon-transport simulations and the procedure for calculating the statistical uncertainties of the tally results. Estimation of the time evolution of radioactivity became feasible by incorporating the activation calculation program DCHAIN-SP into the new package. The efficiency of the simulation was also improved as a result of the implementation of shared-memory parallelization and the optimization of several time-consuming algorithms. Furthermore, a number of new user-support tools and functions that help users to intuitively and effectively perform PHITS simulations were developed and incorporated. Due to these improvements, PHITS is now a more powerful tool for particle transport simulation applicable to various research and development fields, such as nuclear technology, accelerator design, medical physics, and cosmic-ray research.
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| 6. |
- Mitsuhashi, Ikki, et al.
(författare)
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SERENADE. II. An ALMA Multiband Dust Continuum Analysis of 28 Galaxies at 5
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 971:2
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Tidskriftsartikel (refereegranskat)abstract
- We present an analysis of the Atacama Large Millimeter-submillimeter Array (ALMA) multiband dust continuum observations for 28 spectroscopically confirmed bright Lyman break galaxies at 5 lt; z lt; 8. Our sample consists of 11 galaxies at z ∼ 6 newly observed in our ALMA program, which substantially increases the number of 5 lt; z lt; 8 galaxies with both rest-frame 88 and 158 μm continuum observations, allowing us to simultaneously measure the IR luminosity and dust temperature for a statistical sample of z ≳ 5 galaxies for the first time. We derive the relationship between the ultraviolet (UV) slope (β UV) and infrared excess (IRX) for the z ∼ 6 galaxies, and find a shallower IRX-β UV relation compared to the previous results at z ∼ 2-4. Based on the IRX-β UV relation consistent with our results and the β UV-M UV relation including fainter galaxies in the literature, we find a limited contribution of the dust-obscured star formation to the total star formation rate density, ∼30% at z ∼ 6. Our measurements of the dust temperature at z ∼ 6-7, T dust = 40.9 − 9.1 + 10.0 K on average, support a gentle increase of T dust from z = 0 to z ∼ 6-7. Using an analytic model with parameters consistent with recent James Webb Space Telescope results, we discuss that the observed redshift evolution of the dust temperature can be reproduced by an ∼0.6 dex decrease in the gas depletion timescale and ∼0.4 dex decrease in the metallicity. The variety of T dust observed at high redshifts can also be naturally explained by scatters around the star formation main sequence and average mass-metallicity relation including an extremely high dust temperature of T dust gt; 80 K observed in a galaxy at z = 8.3.
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| 7. |
- Sihver, Lembit, 1962, et al.
(författare)
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Improvements and developments of physics models in PHITS for space applications
- 2015
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Ingår i: IEEE Aerospace Conference Proceedings. - 1095-323X. - 9781479953806 ; 2015-June
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Konferensbidrag (refereegranskat)abstract
- Precise predictions of the radiation environment inside space vehicles, and inside the human body, are essential when planning for long term deep space missions. Since these predictions include complex geometries, as well as the contributions from many different types of radiation, including neutrons, 3-D Monte Carlo codes with precise physics models are needed. In this paper, we present improvements and developments of some physics models used in the general purpose 3-D Monte Carlo code PHITS [1]. The total reaction cross section (σR) and the decay lifetime of a projectile particle are the first essential quantities in MC calculations, since these determine the mean free path of the transported particles and the probability function according to which a projectile particle will collide within a certain distance in the matter depends on the σR. This will also scale the calculated partial fragmentation cross sections. In this paper we present comparisons of calculated and measured σR using the Kurotama Hybrid σR, model [2] which is incorporated into PHITS. The prediction of the fragmentation reactions of relativistic heavy ions is also essential for ensuring radiation safety of astronauts. The default model for nuclear-nuclear reactions is JQMD in PHITS. However, JQMD cannot accurately enough describe the nucleon and d, t, 3He and 4He induced reactions. Therefore the Intra-Nuclear Cascade of Liège (INCL) [3] has been selected as the default model for these reactions. Moreover, it has been realized that the production of light fragments is underestimated by conventional simulation codes based on a combination of intranuclear cascade and statistical decay models. This is because this combination cannot reproduce the high multiplicity events that are responsible for the production of light fragments. To better reproduce high multiplicity events, we have simulated fragmentation cross sections using a combination of JQMD/INCL, statistical multi-fragmentation model (SMM) [4,5] and the generalized evaporation model (GEM). Examples of these simulations will be presented. A new approach to describe neutron spectra of deuteron-induced reactions in the Monte Carlo simulations has also been developed by combining the INCL and the Distorted Wave Born Approximation (DWBA) calculation [6]. We have incorporated this combined method into PHITS and applied it to estimate (d,xn) spectra on light targets at incident energies ranging from 10 to 40 MeV. In this paper, we will show that the double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively.
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| 8. |
- Binggeli, Christian, et al.
(författare)
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A puzzling non-detection of [O III] and [C II] from a z ≈ 7.7 galaxy observed with ALMA
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 646
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Tidskriftsartikel (refereegranskat)abstract
- Context. Characterizing the galaxy population in the early Universe holds the key to understanding the evolution of these objects and the role they played in cosmic reionization. However, there have been very few observations at the very highest redshifts to date. Aims. In order to shed light on the properties of galaxies in the high-redshift Universe and their interstellar media, we observe the Lyman-α emitting galaxy z7_GSD_3811 at z = 7.664 with bands 6 and 8 at the Atacama Large Millimeter/submillimeter Array (ALMA). Methods. We target the far-infrared [O iii] 88 µm and [C ii] 158 µm emission lines and dust continuum in the star-forming galaxy z7_GSD_3811 with ALMA. We combine these measurements with earlier observations in the rest-frame ultraviolet (UV) in order to characterize the object and compare the results to those of earlier studies that observed [O iii] and [C ii] emission in high-redshift galaxies. Results. The [O iii] 88 µm and [C ii] 158 µm emission lines are undetected at the position of z7_GSD_3811, with 3σ upper limits of 1.6 × 108 L and 4.0 × 107 L, respectively. We do not detect any dust continuum in band 6 nor band 8. The measured rms in the band 8 and band 6 continua are 26 and 9.9 µJy beam−1, respectively. Similar to several other high-redshift galaxies, z7_GSD_3811 exhibits low [C ii] emission for its star formation rate compared to local galaxies. Furthermore, our upper limit on the [O iii] line luminosity is lower than the previously observed [O iii] lines in high-redshift galaxies with similar UV luminosities. Our ALMA band 6 and 8 dust continuum observations imply that z7_GSD_3811 likely has a low dust content, and our non-detections of the [O iii] and [C ii] lines could indicate that z7_GSD_3811 has a low metallicity (Z. 0.1 Z).
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| 9. |
- Sihver, Lembit, 1962, et al.
(författare)
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PHITS - Applications to radiation biology and radiotherapy
- 2013
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Ingår i: 13th International Varenna Conference on Nuclear Reaction Mechanisms, NRM 2012. - 2078-8835. - 9789290833826 ; , s. 497-502
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Konferensbidrag (refereegranskat)abstract
- PHITS is a 3-dimensional general-purpose Monte Carlo code, which can transport of all varieties of hadrons and heavy ions with energies up to around 100 GeV/nucleon. To be able to estimate the biological damage from neutrons with PUTTS, a feature has been included to treat low energy neutron collisions as "events" which means that the energy and momentum is conserved in each event and makes it possible to extract the kinetic energy distributions of all the residual nuclei without using any local approximation. To estimate the direct biological effects of radiation, mathematical functions, for calculating the microdosmetric probability densities in macroscopic material, have been incorporated in PUTTS. This makes it possible to instantaneously calculate the probability densities of lineal and specific energies around the trajectories of high energetic charged particle tracks. A method for estimating the biological dose has also been established by using the improved PUTTS coupled to a microdosimetric kinetic model.
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