Several imaging x-ray telescope (IXT) prototypes have been fabricated independently by the Institute of Precision Optical Engineering, which employed thermal slumping technology. To verify the performance of the IXT prototypes, a three-layer prototype with a focal length of 2052.5 mm was tested using a narrow beam at the Shanghai Synchrotron Radiation Facility. The performance testing posed a challenge due to the need to suppress the finite source distance effect on the IXT prototype (43-m long source-optic distance). In addition, limited use of motorized stages presents challenges. We present the experimental setups and detailed measurement approaches by utilizing limited measurement devices. The prototype is a segmented telescope comprising six sectors. For the best sector, the measured point spread function (PSF) yields a half power diameter (HPD) of 66″ and agrees well with modeling (62″) and the value measured at PANTER (65″). In addition, the integrated HPD of the whole prototype is 82″ obtained by coadding the PSFs of the six sectors.
Conical Wolter-I geometry is employed for many x-ray telescopes to lower their cost and fabrication difficulty at the expense of angular resolution. Owing to the conic error, the angular resolution of conical Wolter-I geometry is much worse than that of Wolter-I geometry, especially for the telescopes with large diameter. We optimized the conical Wolter-I geometry to significantly improve the angular resolution. We designed a conical Wolter-I geometry with sectioned secondary mirrors. Based on the normal conical Wolter-I geometry, we divided the secondary mirror into two equal sections along the optical axis. In this case, the collecting area was reduced by 5% because of the interval between the two sections. Meanwhile, the conic error was reduced by about 50%, indicating a great improvement in angular resolution. Regarding our improvement in the thermal slumping technique, it is feasible to fabricate sectioned mirrors, thus improving the angular resolution by 50% at the cost of a 5%-reduction in collecting area. In addition, a hybrid geometry, comprising the sectioned and nonsectioned geometries, is proposed as an alternative for x-ray telescopes with a large amount of nested shells, to obtain both a large collecting area and decent angular resolution.
X-ray focusing optics is one of the most important technologies for X-ray astronomy with capabilities of direct imaging, low background and high sensitivity. The enhanced X-ray Timing and Polarimetry (eXTP) and hot universe Baryon surveyor (HUBS), are proposed in China as two major X-ray missions for the next decade. The thermally slumping glass optics (SGO) is one of the approaches to satisfy the requirement of large collecting areas and high angular resolution. In the last years, we made a great progress in the research of SGO X-ray focusing telescope and established the whole fabrication platform. This paper will give a review of recent developments in each step, including lens fabrication, multilayer coating, telescope assembly and optical performance testing. We established an in-situ multi-probe platform based on the contact, trigger and non-contact probes. Thus, the radius deviation and the straightness of graphite strip, the surface shape and the radius of the inner surface of each layer can be measured during the telescope assembly process. We also developed a three-dimensional ray-tracing method to calculate the performance degradation induced by the deformed surface appearing on the forming process and optical assembly. Then the result could be feed back into the fabrication process for improving upon the later mounted mirrors in the real time. We have successfully fabricated two telescope prototypes with the focal length of 2000mm in the last years. The optical performance of the two 3-layer and 21-layer prototypes, which was numbered as No.6 and No.7 prototype respectively, were tested in PANTER test facility of MPE in September 2018. The measured angular resolution t of section A of No.6 prototype is 67±2 arc-second at 8keV, and the measured angular resolution in full aperture of No.7 telescope prototype is 96±3 arc-second at 8keV, which is much better than the previous prototypes.
The Hot Universe Baryon Surveyor (HUBS) mission will carry an imaging X-ray telescope (IXT) for covering an energy range from 0.5 keV to 10 keV to study the hot baryon evolution. In this paper, we report the optical design for HUBS mission and the latest developments at IPOE, Tongji Univeristy. For HUBS mission, we had designed a three-stage conic-approximation type to simplify the manufacturing process. The basic process of imaging X-ray telescopes based on thermal glass slumping has been introduced. Nearly ten prototypes have been fabricated for the process optimization over the years. In August 2018, an IXT prototype with 21 layers was measured at the PANTER X-ray test facility, indicating an HPD of 111″ and an effective area of 39 cm2 at 1.49 keV. In September 2019, the latest prototype with 3 layers reached to an HPD of 58″ at 1.49 keV.
We report a ground X-ray calibration of two X-ray telescope prototypes at the PANTER X-ray Test Facility, of the Max-Planck-Institute for Extraterrestrial Physics, in Neuried, Germany. The X-ray telescope prototypes were developed by the Institute of Precision Optical Engineering (IPOE) of Tongji University, in a conical Wolter-I configuration, using thermal glass slumping technology. Prototype #1 with 3 layers and Prototype #2 with 21 layers were tested to assess the prototypes' on-axis imaging performance. The measurement of Prototype #1 indicates a Half Power Diameter (HPD) of 82" at 1.49 keV. As for Prototype #2, we performed more comprehensive measurements of on-axis angular resolution and effective area at several energies ranging from 0.5-10 keV. The HPD and effective area are 111" and 39 cm^2 at 1.49 keV, respectively, at which energy the on-axis performance of the prototypes is our greatest concern.
Abstract We report on a ground X-ray calibration of two X-ray telescope prototypes at the PANTER X-ray Test Facility, operated by the Max-Planck-Institute for Extraterrestrial Physics, in Neuried, Germany. The X-ray telescope prototypes were developed by the Institute of Precision Optical Engineering (IPOE) of Tongji University, in a conical Wolter-I configuration, using thermal glass slumping technology. Prototype #1 with three layers and Prototype #2 with 21 layers were tested to assess the prototypes’ on-axis imaging performance. The measurement of Prototype #1 indicates a Half Power Diameter (HPD) of 82″ at 1.49 keV. As for Prototype #2, we performed more comprehensive measurements of on-axis angular resolution and effective area at several energies ranging from 0.5–10 keV. The HPD and effective area are 111″ and 39 cm 2 at 1.49 keV, respectively, at which energy the on-axis performance of the prototypes is our greatest concern.
The Hot Universe Baryon Surveyor (HUBS) mission is proposed to study "missing" baryons in the universe. Unlike dark matter, baryonic matter is made of elements in the periodic table, and can be directly observed through the electromagnetic signals that it produces. Stars contain only a tiny fraction of the baryonic matter known to be present in the universe. Additional baryons are found to be in diffuse (gaseous) form, in or between galaxies, but a significant fraction has not yet been seen. The latter (missing baryons) are thought to be hiding in low-density warm-hot ionized medium (WHIM), based on results from theoretical studies and recent observations, and be distributed in the vicinity of galaxies (i.e., circum-galactic medium) and between galaxies (i.e., intergalactic medium). Such gas would radiate mainly in the soft X-ray band and the emission would be very weak, due to its very low density. HUBS is optimized to detect the X-ray emission from the hot baryons in the circum-galactic medium, and thus fill a void in observational astronomy. The goal is not only to detect the missing baryons, but to characterize their physical and chemical properties, as well as to measure their spatial distribution. The results would establish the boundary conditions for understanding galaxy evolution. Though highly challenging, detecting missing baryons in the intergalactic medium could be attempted, perhaps in the outskirts of galaxy clusters, and could shed significant light on the large-scale structures of the universe. The current design of HUBS will be presented, along with the status of technology development.
The imaging x-ray telescope (IXT) was first developed at the Institute of Precision Optical Engineering of Tongji University in 2007. Since then, we have made great progress on the development of mirror fabrication, coatings, and optic assembly. In this paper, we intend to provide an overview of the progress. Currently, we can routinely produce cylindrical mirror substrates with angular resolution of 30″ to 60″. To improve the effective area, coatings using C, Ni, and Pt layers were designed and achieved a high reflectivity at 0.5 to 10 keV. During the optic assembly, an in-situ measurement system and a three-dimensional ray-tracing program have been developed, thus guiding the assembly process in real time. Several prototypes have been fabricated, and one of them with 21 mirror layers was calibrated at the MPE PANTER x-ray test facility in Germany. The IXT prototype, with a focal length of 2052.5 mm, is characterized by a measured half-power diameter of 111″ and effective area of 39 cm2 at 1.49 keV.
The Lightweight Asymmetry and Magnetism Probe (LAMP) is a micro-satellite mission concept dedicated for astronomical X-ray polarimetry and is currently under early phase study. It consists of segmented paraboloidal multilayer mirrors with a collecting area of about 1300 cm^2 to reflect and focus 250 eV X-rays, which will be detected by position sensitive detectors at the focal plane. The primary targets of LAMP include the thermal emission from the surface of pulsars and synchrotron emission produced by relativistic jets in blazars. With the expected sensitivity, it will allow us to detect polarization or place a tight upper limit for about 10 pulsars and 20 blazars. In addition to measuring magnetic structures in these objects, LAMP will also enable us to discover bare quark stars if they exist, whose thermal emission is expected to be zero polarized, while the thermal emission from neutron stars is believed to be highly polarized due to plasma polarization and the quantum electrodynamics (QED) effect. Here we present an overview of the mission concept, its science objectives and simulated observational results.
The X-ray Timing and Polarization (XTP) satellite is dedicated to study black hole, neutron star and magnetar and then get more information in the physics under extreme gravity, density and magnetism. With an effective area of about 1 square meter and angular resolution of 1 arcminute, XTP is expected to make the most sensitive temporal and polarization observations with good energy resolution in 1-30 keV. Large collecting areas are obtained by tightly nesting layers of grazing incidence mirrors in a conical approximation Wolter-I design. The segmented mirrors that form these layers are formed by thermally slumping glass substrates coated with depth-graded W/Si multilayers for enhanced reflectivity in higher energy region. In order to force the overall shape of the nominally cylindrical substrates to the appropriate conic form, an over-constraint method was used to assemble the mirrors to a telescope. We will present performance on the XTP optics and report the current status of the telescope.
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