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An Event Horizon Imager(EHI) Mission Concept Utilizing Medium Earth Orbit Sub-mm Interferometry

空间科学学报 2021年第2期41卷 211-233页

作者： KUDRIASHOV V MARTIn-nEIRA M ROELOFS F FALCKE H BRInKERInK C BARYSHEV A HOGERHEIJDE M YOUnG A POURSHAGHAGHI H KLEIn-WOLT M MOSCIBRODZKA M DAVELAAR J BARAT I DUESMAnn B VALEnTA V PERDIGUES ARMEnGOL J M DE WILDE D MARTIn IGLESIAS P alagha n VAn DER VORST M Department of Astrophysics/IMAPP Radboud University NijmegenP.O.Box 90106500 GL Nijmegenthe Netherlands ESTEC/ESA Keplerlaan 12201 A2 Noordurigkthe Netherlands Mar Planck Institute for Radio Astrorny Auf dem Higel 69D-53121 Bon(Endenich)Germany University of Groningen Landleven 129747 AD Groningenthe Netherlands Leiden Observatory Leiden UniversityPO Box 95132300 RALeidenthe Netherlands Anton Pannekoek Institute for Astronomy University of AmsterdamScience Park 9041098 XHAmsterdamthe Netherlands Center for Computational Astrophysics Flatiron Institute162 Fifth AvenueNew YorkNY 10010USA

Submillimeter interferometry has the potential to image supermassive black holes on event horizon scales,providing tests of the theory of general relativity and increasing our understanding of black hole accretion *** Event Horizon Telescope(EHT) performs these observations from the ground,and its main imaging targets are Sagittarius A~* in the Galactic Center and the black hole at the center of the M87 ***,the EHT is fundamentally limited in its performance by atmospheric effects and sparse terrestrial(u,v)-coverage(Fourier sampling of the image).The scientific interest in quantitative studies of the horizon size and shape of these black holes has motivated studies into using space interferometry which is free of these *** resolution considerations and interstellar scattering effects push the desired observing frequency to bands above 500 *** paper presents the requirements for meeting these science goals,describes the concept of interferometry from Polar or Equatorial Medium Earth Orbits(PECMEO) which we dub the Event Horizon Imager(EHI),and utilizes suitable space technology *** this concept,two or three satellites orbit at slightly different orbital radii,resulting in a dense and uniform spiral-shaped(u,v)-coverage over *** local oscillator signals are shared via an inter-satellite link,and the data streams are correlated on-board before final processing on the ***-satellite metrology and satellite positioning are extensively employed to facilitate the knowledge of the instrument position vector,and its time *** European space heritage usable for both the front ends and the antenna technology of such an instrument is *** and future sensors for the required inter-satellite metrology are *** performance estimates and simulation results are given.

关键词： Instrumentation Space VLBI Radio Telescopes

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Thermoluminescence Energy Response of Copper and Magnesium Oxide Doped Lithium Potassium Borate Using a Monte Carlo n-Particle Code Simulation

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2017年第3期6卷 304-312页

作者： Khaled M. Abushab Yasser S. Alajerami Sami alagha Suhairul Hashim Department of Medical Radiography Al-Azhar University Gaza Strip Palestine Department of Physics Universiti Teknologi Malaysia Skudai Malaysia

The energy absorption coefficient of Cu-doped lithium potassium borate (LKB) dosimeter and TLD 100 was reported theoretically and checked by simulation of Monte Carlo n-particle code version 5 (MCnP5). The response of LKB:Cu for various photon energies (20 keV to 10 MeV) were determined by calculation, experiment and simulation. The obtained results were discussed and compared with TLD 100. For more precise results, the geometry specification, the source information, the material information and tallies were identified and fully described. The results obtained by simulation were determined based on the tally F6, which exhibited the response as energy-dependant on heating function instead of flux. The current results showed that the prepared dosimeter has a greater response than TLD 100 in the lower energy range and a flat response in the higher energy ranges (≥100 keV).

关键词： Thermoluminescence MCnP Lithium Potassium Borate Energy Response

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