Mikhail Gubarev

Bio: Mikhail Gubarev is an academic researcher from Marshall Space Flight Center. The author has contributed to research in topics: Telescope & X-ray optics. The author has an hindex of 14, co-authored 40 publications receiving 529 citations. Previous affiliations of Mikhail Gubarev include University of Alabama in Huntsville & National Research Council.

First Images from the Focusing Optics X-Ray Solar Imager

Abstract: The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload flew for the first time on 2012 November 2, producing the first focused images of the Sun above 5 keV. To enable hard X-ray (HXR) imaging spectroscopy via direct focusing, FOXSI makes use of grazing-incidence replicated optics combined with fine-pitch solid-state detectors. On its first flight, FOXSI observed several targets that included active regions, the quiet Sun, and a GOES-class B2.7 microflare. This Letter provides an introduction to the FOXSI instrument and presents its first solar image. These data demonstrate the superiority in sensitivity and dynamic range that is achievable with a direct HXR imager with respect to previous, indirect imaging methods, and illustrate the technological readiness for a spaceborne mission to observe HXRs from solar flares via direct focusing optics.

Mirror technology development for the International X-ray Observatory mission

Abstract: The International X-ray Observatory (IXO) is designed to conduct spectroscopic, imaging, and timing studies of astrophysical phenomena that take place as near as in the solar system and as far as in the early universe. It is a collaborative effort of ESA, JAXA, and NASA. It requires a large X-ray mirror assembly with an unprecedented X-ray collection area and a suite of focal plane detectors that measure every property of each photon. This paper reports on our effort to develop the necessary technology to enable the construction of the mirror assembly required by IXO.

FOXSI-2: Upgrades of the Focusing Optics X-ray Solar Imager for its Second Flight

Abstract: The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload flew for the second time on 2014 December 11. To enable direct Hard X-Ray (HXR) imaging spectroscopy, FOXSI makes use of grazing-incidence replicated focusing optics combined with fine-pitch solid-state detectors. FOXSI’s first flight provided the first HXR focused images of the Sun. For FOXSI’s second flight several updates were made to the instrument including updating the optics and detectors as well as adding a new Solar Aspect and Alignment System (SAAS). This paper provides an overview of these updates as well as a discussion of their measured performance.

Differential deposition technique for figure corrections in grazing-incidence x-ray optics

Abstract: A differential deposition technique was investigated as a way to minimize axial figure errors in full-shell, grazing-incidence, reflective x-ray optics These types of optics use a combination of off-axis conic segments-hyperbolic, parabolic, and/or elliptical, to reflect and image x-rays Several such mirrors or "shells" of decreasing diameter are typically concentrically nested to form a single focusing unit Individual mirrors are currently produced at Marshall Space Flight Center using an electroforming technique, in which the shells are replicated off figured and superpolished mandrels Several factors in this fabrication process lead to low- and mid-spatial frequency deviations in the surface profile of the shell that degrade the imaging quality of the optics A differential deposition technique, discussed in this paper, seeks to improve the achievable resolution of the optics by correcting the surface profile deviations of the shells after fabrication As a proof of concept, the technique was implemented on small-animal radionuclide-imaging x-ray optics being considered for medical applications This paper discusses the deposition technique, its implementation, and the experimental results obtained to date

Optimal alignment of mirror based pentaprisms for scanning deflectometric devices

Abstract: Replacement of a bulk pentaprism with a mirror-based pentaprism (MBPP) in slope-measuring instruments, such as long trace profilers and autocollimator-based deflectometers, is a well-established way to significantly improve the reliability of surface slope measurements. This is due to the elimination of systematic errors introduced by inhomogeneity of the optical material and fabrication imperfections of bulk pentaprisms. Proper use of an MBPP requires precision mutual alignment of its mirrors. In a recent work we have reported on an original experimental procedure for optimal alignment of MBPP mirrors. The procedure has been verified with numerical ray tracing simulations and via test experiments with the developmental long trace profiler, a slope measuring profiler available at the Advanced Light Source Optical Metrology Laboratory. In the present article, we provide an analytical derivation and verification of easily executed optimal alignment algorithms for two different designs of mirror-based pentaprisms. We also provide an analytical description for a mechanism for reduction of the systematic errors introduced by a typical high quality bulk pentaprism. It is also shown that residual misalignments of an MBPP introduce entirely negligible systematic errors in surface slope measurements with scanning deflectometric devices.

Conceptual design of the International Axion Observatory (IAXO)

Abstract: The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signal-to-noise ratio, IAXO will be about 4–5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few × 10−12 GeV−1 and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling gae with sensitivity — for the first time — to values of gae not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20 m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into ~ 0.2 cm2 spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for ~ 12 h each day.

Towards a new generation axion helioscope

Abstract: We study the feasibility of a new generation axion helioscope, the most ambitious and promising detector of solar axions to date. We show that large improvements in magnetic field volume, x-ray focusing optics and detector backgrounds are possible beyond those achieved in the CERN Axion Solar Telescope (CAST). For hadronic models, a sensitivity to the axion-photon coupling of gaγ few × 10−12 GeV−1 is conceivable, 1–1.5 orders of magnitude beyond the CAST sensitivity. If axions also couple to electrons, the Sun produces a larger flux for the same value of the Peccei-Quinn scale, allowing one to probe a broader class of models. Except for the axion dark matter searches, this experiment will be the most sensitive axion search ever, reaching or surpassing the stringent bounds from SN1987A and possibly testing the axion interpretation of anomalous white-dwarf cooling that predicts ma of a few meV. Beyond axions, this new instrument will probe entirely unexplored ranges of parameters for a large variety of axion-like particles (ALPs) and other novel excitations at the low-energy frontier of elementary particle physics.

The Imaging X-ray Polarimetry Explorer (IXPE)

Abstract: The Imaging X-ray Polarimetry Explorer (IXPE) is an exciting international collaboration for a scientific mission that dramatically brings together the unique talents of the partners to expand observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE uniquely brings to the table polarimetric imaging. IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions-such as neutron stars and black holes. Polarization singularly probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.

Synergistic Cocatalytic Effect of Carbon Nanodots and Co3 O4 Nanoclusters for the Photoelectrochemical Water Oxidation on Hematite.

Abstract: Cocatalysis plays an important role in enhancing the activity of semiconductor photocatalysts for solar water splitting. Compared to a single cocatalyst configuration, a cocatalytic system consisting of multiple components with different functions may realize outstanding enhancement through their interactions, yet limited research has been reported. Herein we describe the synergistic cocatalytic effect between carbon nanodots (CDots) and Co3O4, which promotes the photoelectrochemical water oxidation activity of the Fe2O3 photoanode with a 60 mV cathodically shifted onset potential. The C/Co3O4-Fe2O3 photoanode exhibits a photocurrent density of 1.48 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode), 78 % higher than that of the bare Fe2O3 photoanode. The slow reaction process on the single CoIII-OH site of the Co3O4 cocatalyst, oxidizing H2O to H2O2 with two photogenerated holes, could be accelerated by the timely H2O2 oxidation to O2 catalyzed on CDots.