The resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM) consists of an array of 6 × 6 silicon-thermistor microcalorimeters cooled down to 50 mK and a high-throughput x-ray mirror assembly (XMA) with a focal length of 5.6 m. XRISM is a recovery mission of ASTRO-H/Hitomi, and the Resolve instrument is a rebuild of the ASTRO-H soft x-ray spectrometer (SXS) and the Soft X-ray Telescope (SXT) that achieved energy resolution of ∼5 eV FWHM on orbit, with several important changes based on lessons learned from ASTRO-H. The flight models of the Dewar and the electronics boxes were fabricated and the instrument test and calibration were conducted in 2021. By tuning the cryocooler frequencies, energy resolution better than 4.9 eV FWHM at 6 keV was demonstrated for all 36 pixels and high resolution grade events, as well as energy-scale accuracy better than 2 eV up to 30 keV. The immunity of the detectors to microvibration, electrical conduction, and radiation was evaluated. The instrument was delivered to the spacecraft system in 2022-04 and is under the spacecraft system testing as of writing. The XMA was tested and calibrated separately. Its angular resolution is 1.27′ and the effective area of the mirror itself is 570 cm2 at 1 keV and 424 cm2 at 6 keV. We report the design and the major changes from the ASTRO-H SXS, the integration, and the results of the instrument test.
The Resolve instrument onboard the x-ray imaging and spectroscopy mission (XRISM) hosts an x-ray microcalorimeter that consists of 36 pixels in an array operated at 50 mK. It is currently under development and will be launched in 2022. x-ray microcalorimeters are known for their high spectral resolution, but they also excel in timing resolution for the necessity of cross-correlating event signals with templates in the time domain for accurate energy derivation. Primary and redundant modulated x-ray sources (MXS) are installed in Resolve for the purpose of correcting changes in the energy scale of the microcalorimeters while minimizing additional background; each source is switched on for intervals of O (1 ms) with a duty cycle of ∼1 %. The MXS can also be utilized for calibrating relative timing as a function of pixel, event grade, and energy. We had a week-long run in 2022 June using the flight model hardware during the spacecraft level test with several different settings. We describe the method and the result of the relative timing calibration using this dataset.
Resolve is an x-ray microcalorimeter spectrometer on the X-Ray Imaging and Spectroscopy Mission (XRISM) to be launched in Japanese fiscal year 2022. Resolve is required to achieve an energy resolution of 7 eV at FWHM at 6 keV. To satisfy this requirement, it is necessary to correct the in-orbit gain drift. For this purpose, Resolve is equipped with multiple gain tracking calibration sources, including the modulated x-ray sources (MXS). The MXS will be operated in a pulsed mode, in which calibration x-rays illuminating the detector array are emitted at a duty cycle of ∼1%. The low duty cycle allows us to monitor the gain drift with a small loss of the observing efficiency. However, the use of the MXS has drawbacks such as increase in the instrumental background due to exponentially decaying afterglow emission following each MXS pulse and the loss of throughput due to changes in the event-grade branching ratio. To minimize these effects, an optimization of the MXS operating parameters is needed. Based on the results of the MXS component-level tests, we established an analytical model that describes the MXS pulse and afterglow count rates. We obtained the optimal pulse parameters for various gain tracking intervals and estimated the effects of using the MXS on observation data. We further studied the trade-off between these effects and resolution degradation using the actual in-orbit drift observed with the soft x-ray spectrometer on the Hitomi satellite. Our study forms the basis of strategies for the in-orbit gain drift correction of Resolve.
Resolve onboard the x-ray satellite X-Ray Imaging and Spectroscopy Mission (XRISM) is a cryogenic instrument with an x-ray microcalorimeter in a Dewar. A lid partially transparent to x-rays (called gate valve or GV) is installed at the top of the Dewar along the optical axis. Because observations will be made through the GV for the first few months, the x-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the x-ray beamline at ISAS. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be changing at specific energies. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in polycrystal Be, which we incorporated into our transmission phenomenological model. We present the x-ray diffraction measurement on the sample to support our interpretation. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula observed with Hitomi SXS and confirmed improvements of the model parameters.
Resolve onboard the X-ray satellite XRISM is a cryogenic instrument with an X-ray microcalorimeter in a Dewar. A lid partially transparent to X-rays is installed at the top of the Dewar along the optical axis, which is called the gate valve (GV). Because observations will be made through the GV for the first few months, the X-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the X-ray beamline at ISAS for the first time. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in poly-crystal Be, which we incorporated into our phenomenological model. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula data observed with Hitomi SXS and confirmed improvements of the model.
The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise highresolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.
The Resolve instrument onboard the X-ray Astronomy Recovery Mission (XARM) consists of
an array of 6x6 silicon-thermistor microcalorimeters cooled down to 50 mK
and a high-throughput X-ray mirror assembly with a focal length of 5.6 m.
The XARM is a recovery mission of ASTRO-H/Hitomi,
and is developed by international collaboration of Japan, USA, and Europe.
The Soft X-ray Spectrometer (SXS) onboard Hitomi demonstrated high resolution
X-ray spectroscopy of ~ 5 eV FWHM in orbit for most of the microcalorimeter pixels.
The Resolve instrument is planned to mostly be a copy of the Hitomi SXS and
Soft X-ray Telescope designs, though several changes are planned
based on the lessons learned of Hitomi.
The energy resolution budget of the microcalorimeters is updated,
reflecting the Hitomi SXS results.
We report the current status of the Resolve instrument.
The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,“Resolving astrophysical problems by precise high-resolution X-ray spectroscopy”.1 This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission’s initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020’s and 2030’s. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: “Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects”. To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
The Astro-H (Hitomi) Soft X-ray Spectrometer (SXS) was a pioneering imaging x-ray spectrometer with 5 eV energy resolution at 6 keV. The instrument used a microcalorimeter array at the focus of a high-throughput soft x-ray telescope to enable high-resolution nondispersive spectroscopy in the soft x-ray waveband (0.3 to 12 keV). We present the suite of ground calibration measurements acquired from 2012 to 2015, including characterization of the detector system, anti-coincidence detector, optical blocking filters, and filter-wheel filters. The calibration of the 36-pixel silicon thermistor microcalorimeter array includes parameterizations of the energy gain scale and line-spread function for each event grade over a range of instrument operating conditions, as well as quantum efficiency measurements. The x-ray transmission of the set of five Al/polyimide thin-film optical blocking filters mounted inside the SXS dewar has been modeled based on measurements at synchrotron beamlines, including with high spectral resolution at the C, N, O, and Al K-edges. In addition, we present the x-ray transmission of the dewar gate valve and of the filters mounted on the SXS filter wheel (external to the dewar), including beryllium, polyimide, and neutral density filters.
The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
The soft x-ray spectrometer (SXS) was a cryogenic high-resolution x-ray spectrometer onboard the Hitomi (ASTRO-H) satellite that achieved energy resolution of 5 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat sink was composed of two-stage Stirling cryocoolers, a He4 Joule–Thomson cryocooler, and superfluid liquid helium and was installed in a dewar. It was designed to achieve a helium lifetime of more than 3 years with a minimum of 30 L. The satellite was launched on February 17, 2016, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the helium tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and the cryocoolers.
During the Hitomi (Astro-H) commissioning observations the SXS dewar gate valve (GV) remained closed to protect the instrument from initial spacecraft outgassing. As a result, the optical path of the observations included the Be window installed on the GV. Both x-ray fluorescence (XRF) analysis and x-ray transmission measurements were performed in June 2016 on the flight-spare Be window which is the same lot as the flight material at SPring-8 in Japan. The beamline operating range is 3.8 - 30 keV. We used a beam spot size of 1 mm × 0.2 mm to measure two positions on the Be window, at the center of the window and at one position 6.5 mm off-center. We used simultaneous transmission measurements of standard materials for energy calibration. The transmission data clearly showed Fe and Ni K-edges, plus a marginal detection of the Mn K-edge. We found that our transmission data was best fit using the following component Be: 261.86±0.01μm, Cr: 3nm (fixed), Mn: 3.81±0.05nm, Fe: 10.83±0.05nm, Ni: 16.48±0.03nm, Cu: 5nm (fixed). The transmission is reduced 1% at the Fe K-edge. The amount of contaminated materials are comparable to the values of the value provided by the vender. The surface transmission is strained with σ = 0.11% of the unbiased standard deviation calculated variation in the residuals between the measured value and the model.
The Soft X-ray Spectrometer (SXS) onboard the Hitomi (ASTRO-H) satellite observed several celestial objects. All the observations with the SXS were performed through a beryllium (Be) window installed on the gate-valve of the SXS dewar. However, the Be window had not been well calibrated before launching. Therefore, we measured the transmission of a spare Be window, which is from the same lot as the flight material. The measurements were preformed in 3.8–30 keV range with BL01B1 at SPring-8, and in 2.5–12 keV range combined with BL11B and BL7C at KEK-PF. In this paper, we report mainly the results of the KEK-PF experiment. With the KEK-PF, we measured five places of the Be window. Their estimated thicknesses are consistent with each other within 1.3 μm. In the five transmission data, we confirmed absorption edges by Fe-K, Ni-K and Mn-K and six edge like features at 3460, 6057, 6915, 7590, 8790 and 9193 eV, which can be interpreted as Bragg diffraction by Be polycrystal. By combining the transmissions measured at KEK-PF and at SPring-8, we estimated Be thickness of 259.73±0.01 μm. The amounts of contaminated materials are roughly comparable with the provided values from the provider. We also performed scanning measurements of whole surface in the Be window. In the results, thickness of Be window was found to be uniform in ±1µm from the measurement with 4 keV X-rays.
We report recent results of the performance measurement of our X-ray telescope with adaptive optics. The
telescope is designed to use the 13.5nm EUV with the Mo/Si multilayers, making a normal incident optics. The
primary mirror is 80mm in its diameter and the focal length of 2m. The deformable mirror is controlled by
measuring a wave-front of an optical laser. Effects of a difference between the light paths from the reference and
from an object are examined. The angular resolution is measured with optical light and we confirm almost
diffraction limited resolution as well as its appropriate function as adaptive optics.
KEYWORDS: X-rays, Sensors, Spectroscopy, Space operations, Lithium, Field effect transistors, Satellites, Calibration, Single crystal X-ray diffraction, Magnetic sensors
We present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.
The Hitomi (ASTRO-H) mission is the sixth Japanese X-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. After a successful launch on 2016 February 17, the spacecraft lost its function on 2016 March 26, but the commissioning phase for about a month provided valuable information on the on-board instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
We summarize all the in-orbit operations of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H (Hit- omi) satellite. The satellite was launched on 2016/02/17 and the communication with the satellite ceased on 2016/03/26. The SXS was still in the commissioning phase, in which the setups were progressively changed. This article is intended to serve as a reference of the events in the orbit to properly interpret the SXS data taken during its short life time, and as a test case for planning the in-orbit operation for future micro-calorimeter missions.
The Soft X-ray Spectrometer (SXS) is a cryogenic high-resolution X-ray spectrometer onboard the ASTRO-H satellite, that achieves energy resolution better than 7 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator. The cooling chain from room temperature to the ADR heat sink is composed of 2-stage Stirling cryocoolers, a 4He Joule-Thomson cryocooler, and super uid liquid He, and is installed in a dewar. It is designed to achieve a helium lifetime of more than 3 years with a minimum of 30 liters. The satellite was launched on 2016 February 17, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the He tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and cryocoolers.
PolariS (Polarimetry Satellite) is a Japanese small satellite mission dedicated to polarimetry of X-ray and γ-ray sources. The primary aim of the mission is to perform hard X-ray (10-80 keV) polarimetry of sources brighter than 10 mCrab. For this purpose, PolariS employs three hard X-ray telescopes and scattering type imaging polarimeters. PolariS will measure the X-ray polarization for tens of sources including extragalactic ones mostly for the first time. The second purpose of the mission is γ-ray polarimetry of transient sources, such as γ-ray bursts (GRBs). Wide field polarimeters based on similar concept as that used in the IKAROS/GAP but with higher sensitivity will be used, and polarization measurement of 10 GRBs per year is expected.
We report our recent activities for a development of a new X-ray interferometer with a beam splitter and discuss a possible observation of some celestial objects. The X-ray interferometer consists of two flat mirrors and one flat beam splitter. Samples of the beam splitter and the mirrors have been designed and fabricated. We measured the reflectivity of the mirrors and the reflectivity and transmission of the beam splitters with a synchrotron source at KEK-PF. Obtained results of the mirrors are roughly consistent with the design values, but the reflectivity of the beam splitter is roughly half of the design value. Using these measured values, we estimated required area and observation-time to obtain fringe signals of celestial objects. We concluded that a broad-band interferometer using non-dispersive high spectral resolution detector, such as the micro-calorimeter array, is essential for the future development.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of ΔE ≤ 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.
We present the development status of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H mission. The SXS provides the capability of high energy-resolution X-ray spectroscopy of a FWHM energy resolution of < 7eV in the energy range of 0.3 – 10 keV. It utilizes an X-ray micorcalorimeter array operated at 50 mK. The SXS microcalorimeter subsystem is being developed in an EM-FM approach. The EM SXS cryostat was developed and fully tested and, although the design was generally confirmed, several anomalies and problems were found. Among them is the interference of the detector with the micro-vibrations from the mechanical coolers, which is the most difficult one to solve. We have pursued three different countermeasures and two of them seem to be effective. So far we have obtained energy resolutions satisfying the requirement with the FM cryostat.
PolariS (Polarimetry Satellite) is a Japanese small satellite mission dedicated to polarimetry of X-ray and γ-ray sources. The primary aim of the mission is to perform wide band X-ray (4-80 keV) polarimetry of sources brighter than 10 mCrab. For this purpose, Polaris employs three hard X-ray telescopes and two types of focal plane imaging polarimeters. PolariS observations will measure the X-ray polarization for tens of sources including extragalactic ones mostly for the first time. The second purpose of the mission is γ-ray polarimetry of transient sources, such as γ-ray bursts. Wide field polarimeters based on similar concept as that used in the IKAROS/GAP but with higher sensitivity, i.e., polarization measurement of 10 bursts per year, will be employed.
We report our examination of a new X-ray interferometer for observation of celestial objects and our recent work
for preparation of laboratory experiments. The new X-ray interferometer is consisting of two
at mirrors and
one
at beam splitter which are used as grazing incident optics. The aimed wave length is a O-K band or a C-K
band. The beam splitter and the mirrors are fabricated by Mo/Si multilayer. We measured their
atness and
found that the measured
atness is acceptable for the test experiment. A pin hole X-ray source is also preparing
for a laboratory experiment in order to demonstrate a X-ray interference. We investigated a possible observation
of accretion disks around BHs and nearby stars. With a reasonable size of the base line, we can measure their
size and possibly we can obtain an evidence of a black hole shadow.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated
by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy
universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV.
These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3–12 keV with
high spectral resolution of ΔE ≦ 7 eV, enabled by a micro-calorimeter array located in the focal plane of
thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5–80 keV, located in the focal plane of
multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4–12 keV,
with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera
type soft gamma-ray detector, sensitive in the 40–600 keV band. The simultaneous broad bandpass, coupled
with high spectral resolution, will enable the pursuit of a wide variety of important science themes.
We report a study of a new X-ray interferometer with a beam splitter for future observation of celestial objects. A
possible configuration of an interferometer is proposed. By using a beam splitter, the length of the interferometer
becomes short and without a formation flight of satellites a reasonable X-ray interferometric observation can be
possible. An observation of early type stars is discussed. A laboratory experiment for performance verification
is also discussed.
We report experimental results of our normal-incident EUV telescope tuned to a 13.5 nm band, with an adaptive
optics. The optics consists of a spherical primary mirror and a secondary deformable mirror. A laser plasma
source irradiates optical and EUV lights to the system. The system also equips a reference laser, optical light
from which are nearly spherical and reflected by mirrors through the light path along the objective light. We
controlled the deformable mirror to correct the wave form by referring that of the reference laser. At first, we
attempted a normal AO control, where we controlled deformable mirror so that the wave form of the reference
laser becomes spherical. Although we verified an improvement of angular resolution with this method, the
resolution is not good enough comparing with the diffraction limit. The degradation is due to the difference
between the paths of objective light and the reference laser. Then we modify the target wave form to control the
deformable mirror, as the EUV image becomes best. We confirmed the validity of this control and performed a
2.1 arcsec resolution in both optical and EUV lights.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated
by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the
high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular
resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination
of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray
mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV)
provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD
camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray
detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led
by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of
ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be
pursued.
The Soft X-ray Spectrometer (SXS) is a cryogenic high resolution X-ray spectrometer onboard the X-ray astronomy
satellite ASTRO-H. The detector array is cooled down to 50 mK using a 3-stage adiabatic demagnetization
refrigerator (ADR). The cooling chain from room temperature to the ADR heat-sink is composed of superfluid
liquid He, a 4He Joule-Thomson cryocooler, and 2-stage Stirling cryocoolers. It is designed to keep 30 L of liquid
He for more than 3 years in the nominal case. It is also designed with redundant subsystems throughout from
room temperature to the ADR heat-sink, to alleviate failure of a single cryocooler or loss of liquid He.
We have developed a new back-illuminated (BI) CCD which has an Optical Blocking Layer (OBL) directly coating
its X-ray illumination surface with Aluminum-Polyimide-Aluminum instead of Optical Blocking Filter (OBF).
OBL is composed of a thin polyimide layer sandwiched by two Al layers. Polyimide and Al has a capability to
cut EUV and optical light, respectively. The X-ray CCD is affected by large doses of extreme ultraviolet (EUV)
radiation from Earth sun-lit atmosphere (airglow) in orbit as well as the optical light.
In order to evaluate the performance of the EUV-attenuating polyimide of the OBL, we measured the EUV
transmission of both the OBL and the OBF at energies between 15-72 eV by utilizing a beam line located
at the Photon Factory in High Energy Accelerator Research Organization (KEK-PF). We obtained the EUV
transmission to be 3% at 41 eV which is the same as the expected transmission from the designed thickness of
the polyimide layer. We also found no significant change of the EUV transmission of polyimide over the nine
month interval spanned by out two experiments.
We also measured the optical transmission of the OBL at wavelengths between 500-900Å to evaluate the
performance of the Al that attenuates optical light, and found the optical transmission to be less than 4×10-5.
We present the science and an overview of the Soft X-ray Spectrometer onboard the ASTRO-H mission with
emphasis on the detector system. The SXS consists of X-ray focusing mirrors and a microcalorimeter array and
is developed by international collaboration lead by JAXA and NASA with European participation. The detector
is a 6×6 format microcalorimeter array operated at a cryogenic temperature of 50 mK and covers a 3' ×3' field
of view of the X-ray telescope of 5.6 m focal length. We expect an energy resolution better than 7 eV (FWHM,
requirement) with a goal of 4 eV. The effective area of the instrument will be 225 cm2 at 7 keV; by a factor of
about two larger than that of the X-ray microcalorimeter on board Suzaku. One of the main scientific objectives
of the SXS is to investigate turbulent and/or macroscopic motions of hot gas in clusters of galaxies.
We report an experimental result of our normal-incident EUV telescope tuned to a 13.5 nm band, with an
adaptive optics. The optics consists of a spherical primary mirror and a secondary mirror. Both are coated by
Mo/Si multilayer. The diameter of the primary and the secondary mirrors are 80 mm and 55mm, respectively.
The secondary mirror is a deformable mirror with 31 bimorph-piezo electrodes. The EUV from a laser plasma
source was exposed to a Ni mesh with 31 micro-m wires. The image of this mesh was obtained by a backilluminated
CCD. The reference wave was made by an optical laser source with 1 μm pin-hole. We measure the
wave form of this reference wave and control the secondary mirror to get a good EUV image. Since the paths
of EUV and the optical light for the reference were different from each other, we modify the target wave from
to control the deformable mirror, as the EUV image is best. The higher order Zernike components of the target
wave form, as well as the tilts and focus components, were added to the reference wave form made by simply
calculated. We confirmed the validity of this control and performed a 2.1 arc-sec resolution.
We developed an EUV polarimeter consisting of a transmission multilayer and a back-illumination CCD. The
transmission of the multilayer at an incident angle of45-deg depends on the polarization angle. We developed
a polarimeter by using the transmission. Advantages of usage a transmission multilayer are as follows. 1)
The mechanics is simple, because we do not need to move the detectors. 2) High energy photons, where the
multilayer is transparent, can be measured as a normal observation, if we use a CCD as a photon counting. 3)
By removing the multilayer from the optical axis, normal observation with a CCD can be performed. A stand
alone multilayer of Mo/Si was fabricated, which consists of seven layer-pairs with a thickness of 20 nm. We
evaluated the performance of the polarimeter using a synchrotron beam line. We confirmed a modulation factor
of 47% around 95 eV.
The SXS (Soft X-ray Spectrometer) onboard the coming Japanese X-ray satellite NeXT (New Exploration Xray
Telescope) and the SXC (Spectrum-RG X-ray Calorimeter) in Spectrum-RG mission are microcalorimeter
array spectrometers which will achieve high spectral resolution of ~ 6 eV in 0.3-10.0 keV energy band. These
spectrometers are well-suited to address key problems in high-energy astrophysics. To achieve these high spectral
sensitivities, these detectors require to be operated under 50 mK by using very efficient cooling systems including
adiabatic demagnetization refrigerator (ADR). For both missions, we propose a two-stage series ADR as a cooling
system below 1 K, in which two units of ADR consists of magnetic cooling material, a superconducting magnet,
and a heat switch are operated step by step. Three designs of the ADR are proposed for SXS/SXC. In all three
designs, ADR can attain the required hold time of 23 hours at 50 mK and cooling power of 0.4μW with a low
magnetic fields (1.5/1.5 Tesla or 2.0/3.0 Tesla) in a small configuration (180 mmφ× 319 mm in length).
We also fabricated a new portable refrigerator for a technology investigation of two-stage ADR. Two units of
ADR have been installed at the bottom of liquid He tank. By using this dewar, important technologies such as an operation of two-stage cooling cycle, tight temperature control less than 1 μK (in rms) stability, a magnetic
shielding, saltpills, and gas-gap heat switches are evaluated.
The Soft X-ray Spectrometer (SXS) onboard the NeXT (New exploration X-ray Telescope) is an X-ray spectrometer
utilizing an X-ray microcalorimeter array. Combined with the soft X-ray telescope of 6 m focal length,
the instrument will have a ~ 290cm2 effective at 6.7 keV. With the large effective area and the energy resolution
as good as 6 eV (FWHM), the instrument is very suited for the high-resolution spectroscopy of iron K emission
line. One of the major scientific objectives of SXS is to determine turbulent and/or macroscopic motions of the
hot gas in clusters of galaxies of up to z ~ 1. The instruments will use 6 × 6 or 8 × 8 format microcalorimeter
array which is similar to that of Suzaku XRS. The detector will be cooled to a cryogenic temperature of 50 mK
by multi-stage cooling system consisting of adiabatic demagnetization refrigerator, super fluid He, a 3He Joule
Thomson cooler, and double-stage stirling cycle cooler.
We are developing a normal incident EUV-telescope for a future space experiment, using an adaptive optics. The
primary mirror and the secondary mirror were coated with Mo/Si multi-layers. The secondary mirror is a deformable
mirror. The reference wave is produced with a 1 micro-m pin hole laser and its wave front shape is used for a correction
of the EUV wave shape. The imaging experiments with optical was performed with the adaptive optics system. The
imaging with 13.5nm EUV was also performed but without the adaptive optics system. The optical image is almost
diffraction limited. A ray trace simulation was performed and a correction method in our system, where the EUV wave
form is corrected using the optical reference lights, was investigated.
The X-ray Imaging Spectrometers (XIS) on-board Suzaku is an X-ray CCD camera system that has features of low backgroud, good energy resolution, and high quantum efficiency (QE) at 0.2-12 keV band. However, an unexpected degradation of the QE at low energies (<1 keV) has emerged since November 2005. Some contaminants are considered to be adsorbed on the Optical Blocking Filter (OBF) for each sensor and cause the degradation. A suspected contamination source is rubber used in the shock absorber of the satellite gyro. For the recovery of the QE, we now design to remove the contaminants by increasing the OBF temperature. Before the on-board bakeout is performed, we need to confirm on the ground that it does not cause a serious damage to the OBF. In order to reproduce the on-board contamination, we adsorbed the contaminant of ~160 μg cm-2 from the rubber on a spare OBF and a Thermoelectric Quartz Crystal Microbalance simultaneously, which are cooled down to -40°C. Although enexpected wrinkles appeared on the OBF surface during the adsorption and they remained through the subsequent bakeout, we could not find any tears on it. In addition, we estimated the desorption rate at -15°C to be ~5 μg cm-2 per day. In our presentation, we also discuss the expected effect by the on-board bakeout based on these results.
We are developing a normal incident X-ray telescope with an adaptive optics system in order to achieve an
unprecedented high-angular-resolution. The primary mirror with a diameter of 80mm is a spherical shape with a focal
length of 2000 mm, which was coated by Mo/Si multilayer. The secondary mirror is a deformable mirror with 55 mm
diameter, which was also coated by Mo/Si multilayer. Optical lights from a pin-hole were measured by a wave-front
sensor and used as a reference for a correction of the deformable mirror. All the components were installed in a vacuum
chamber. A closed loop control with the wave front sensor and the deformable mirror was successfully performed in the
telescope and we confirmed the correction of the wave front. The rms-deviation of a performed wave front from a target
shape during the control was ~30 nm-rms, whereas it without control was more than ~80 nm-rms. A 13.5 nm X-ray
from an electron impact X-ray source was imaged on a backside CCD installed on a focal plane. A mesh made by steel
was installed in front of the X-ray source, whose pitch and wire-thickness are 500 micro-m and 50 micro-m. The image
of this mesh by optical lights from the X-ray generator is detected by the CCD. The current image quality is ~2.4 arc-sec
and this was comparable to a diffraction limit of an optical wave length with our 80mm primary mirror.
We report the current status of the "X-mas" (X-ray milli-arcsecond) project. X-mas is an application of the AO technology to the X-ray optics, aiming to obtain high-resolution defraction-limited X-ray images. Our X-ray telescope employs the Newton optics with a paraboloid primary and a 31-element deformable secondary mirrors. The aperture of the primary mirror is 80 millimeters with the focal length of 2 meters. Multi-layer coating of the mirrors by silicon and molybdenum realizes a large reflectivity of ~60% for the primary and 30-50% for the secondary mirror at 13.5 nm, which enables us to construct a normal incidence optics at this wavelength. We use a laser guide source and a wave front sensor to optimize the form of the secondary deformable mirror for the purpose of offsetting the large-scale figure errors in the X-ray optics. A back-side illumination X-ray CCD detector manufactured by Hamamatsu Photonics is used for X-ray detections. We have assembled all these elements and started to accumulate data. Closed-loop AO is in operation for the laser guide source. Likely X-ray images are obtained through the telescope. The results in 2005-2006 are presented.
We report a new type X-ray imaging polarimeter: a multilayer-coated CCD. When the X-rays are detected by the CCD,
with the incident angle of 45 deg, through the coated multi-layer, the transmissions of the P and S polarized photons are
different from each other and we can get an image with a selected position angle of the polarization.
By the simulation of the transmission of the multi-layer, we designed an optimal number of the layer-pair and their
thickness. The target wave length is 135Å, because the Mo/Si multi-layer has a good performance in this energy range.
If the dead layer of the back-side CCD is 1000Å, nine layer-pairs make the largest difference between the P and S
transmission.
We deposited the Mo/Si multi-layer directly on a back-side CCD. The CCD was exposed to the polarized photons from
synchrotron radiation with 45 deg incident angle. The detected intensity is measured as a function of the photon energy
and of the rotation angle around the photon beam. The detection of the polarization is confirmed. However the
measured performance is lower than expected. Some possibilities of the cause are discussed.
We give overview and the current status of the development of the Soft X-ray Imager (SXI) onboard the NeXT
satellite. SXI is an X-ray CCD camera placed at the focal plane detector of the Soft X-ray Telescopes for Imaging
(SXT-I) onboard NeXT. The pixel size and the format of the CCD is 24 x 24μm (IA) and 2048 x 2048 x 2
(IA+FS). Currently, we have been developing two types of CCD as candidates for SXI, in parallel. The one is
front illumination type CCD with moderate thickness of the depletion layer (70 ~ 100μm) as a baseline plan.
The other one is the goal plan, in which we develop back illumination type CCD with a thick depletion layer
(200 ~ 300μm). For the baseline plan, we successfully developed the proto model 'CCD-NeXT1' with the pixel
size of 12μm x 12μm and the CCD size of 24mm x 48mm. The depletion layer of the CCD has reached 75 ~ 85μm.
The goal plan is realized by introduction of a new type of CCD 'P-channel CCD', which collects holes in stead
of electrons in the common 'N-channel CCD'. By processing a test model of P-channel CCD we have confirmed
high quantum efficiency above 10 keV with an equivalent depletion layer of 300μm. A back illumination type
of P-channel CCD with a depletion layer of 200μm with aluminum coating for optical blocking has been also
successfully developed. We have been also developing a thermo-electric cooler (TEC) with the function of the
mechanically support of the CCD wafer without standoff insulators, for the purpose of the reduction of thermal
input to the CCD through the standoff insulators. We have been considering the sensor housing and the onboard
electronics for the CCD clocking, readout and digital processing of the frame date.
We are developing a soft x-ray telescope with an adaptive optics system for future astronomical observation with very fine angular resolution of an order of milli-arc-second. From a technical point of view, we are trying to develop a normal incident telescope with multi layers. Thus the wave length is limited to be around 13.5 nm with a band pass of roughly 1nm. Since the x-ray telescope must be installed on a satellite, a stable conditions of temperature, gravity etc, can not be expected. Therefore, we investigate to use an adaptive optics system using an optical light source attached in the telescope. In this paper, we report our present status of the development. The primary mirror is an off-axis paraboloid with 80 mm effective diameter and 2 m focal length. This mirror has been coated with Mo/Si multi-layers. The reflectivity of the 13.5 nm x rays is ranging from 35% to 55%. We use a deformable mirror for the secondary mirror, which has also been coated with Mo/Si multi-layers. This mirror consists of 31 element-bimorph-piezo electrodes. The surface roughness of the mirror is ~6 nm rms. The reflectivity of the 13.5 nm x rays is roughly 65%. The adaptive optics system using an optical laser and a wave front sensor has been performed. We are using a shack-hartmann sensor (HASO 32) with a micro-lens array and a CCD. A pin hole with one micron diameter is used for the optical light source. The precision of the measurement of the wave front shape is a few nm. X-ray exposure test is now conducting, although the optical adaptive optics system is not yet installed. The x-ray detector is a back illumination CCD. The quantum efficiency for 13.5 nm x ray is ~50%. The pixel size is 24 micron square. X-ray source is an electron impact source with an Al/Si alloy target. We confirmed that the x-ray intensity around 13.55 nm is bright enough for our experiment. The imaging performance is now trying to improve and the adaptive optics system will be installed in this year.
We are developing an ultra high precision soft X-ray telescope. The design of the telescope is a normal incident one for 13.5nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X-ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system.
The telescope system is now integrating and checking by optical light. The shape of the primary mirror is an off-axis paraboloid with a focal length of 2m and an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5nm was ranging from 30 to 50 %. The secondary mirror is a basically flat mirror but actually an deformable mirror with 31 piezo-actuators. The detector is now a wave front sensor (shack-hartmann type). The closed loop control has been performed and factor of 2.4 improvement of the wave front shape has been performed comparing to the un-control case.
The NeXT mission has been proposed to study high-energy non-thermal phenomena in the universe. The high-energy response of the super mirror will enable us to perform the first sensitive imaging observations up to 80 keV. The focal plane detector, which combines a fully depleted X-ray CCD and a pixelated CdTe detector, will provide spectra and images in the wide energy range from 0.5 keV to 80 keV. In the soft gamma-ray band upto ~1 MeV, a narrow field-of-view Compton gamma-ray telescope utilizing several tens of layers of thin Si or CdTe detector will provide precise spectra with much higher sensitivity than present instruments. The continuum sensitivity will reach several x 10-8 photons/s/keV/cm2 in the hard X-ray region and a few x 10-7 photons/s/keV/cm2 in the soft gamma-ray region.
We measured optical and soft X-ray transmission of Optical Blocking Filters (OBFs) for Charge Coupled Device (CCD) cameras, which will be launched as focal plane detectors of X-ray telescopes onboard the Japanese 5th X-ray astronomical satellite, Astro-E 2. The filters were made from polyimide coated with Al. The X-ray absorption fine structures (XAFSs) at the K edges of C, N, O and K and L edges of Al were measured. The depth of the absorption edge of O was deep, compared to the other elements of polyimide. This is evidence of the oxidation of Al. The optical transmission is roughly less than 10-6 except for a peak around the wave length of 550 nm. Long term change of the soft X-ray transmission was measured. No significant change of the thickness of the oxidation layer was found during half year.
We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. This is also confirmed that the determination of the image center of each micro lens can be ~1/100 of the pixel size. The precision of the deformable mirror was roughly 5 nm rms. Using the closed loop control the accuracy of the repeatability of the shape of the deformable mirror is less than 2 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80 mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was ranging from 30 to 50%. The X ray-optical separation filter was made from Zr with a thickness of ~170 nm. The transmission of the filter for low energy X-ray measured and was roughly 50% at thickness of ~170 nm. The transmission of the filter for low energy X-ray was measured and was roughly 50% at 13.5 nm.
We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the prevision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an x-ray optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system deformation as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. The preicison of the deformable mirror was roughly 5 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was rnaging from 30 to 50%. The x-ray optical separation filter was made from Zr with a thicknness of ~170nm. The transmission of the filter for low energy x-ray was measured and was roughly 50% at 13.5nm.
We report on design updates for the XIS (X-ray Imaging Spectrometer)
on-board the Astro-E2 satellite. Astro-E2 is a recovery mission of Astro-E, which was lost during launch in 2000. Astro-E2 carries a total of 5 X-ray telescopes, 4 of which have XIS sensors as their focal plane detectors. Each XIS CCD camera covers a field of view of 19×19 arcmin in the energy range of 0.4-12 keV. The design of the Astro-E2 XIS is basically the same as that for Astro-E, but some improvements will be implemented. These are (1) CCD charge injection capability, (2) a revised heat-sink assembly, and (3) addition of a 55Fe radio-isotope on the door. Charge injection may be used to compensate for and calibrate radiation-induced degradation of the CCD charge transfer efficiency. This degradation is expected to become significant after a few year's operation in space. The new heat-sink assembly is expected to increase the mechanical reliability and cooling capability of the XIS sensor. The new radio-isotope on the door will provide better calibration data. We present details of these improvements and summarize the overall design of the XIS.
Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4 - 2.2 keV range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented. Nevertheless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.
We measure various spectral response characteristics around the oxygen and silicon K absorption edges of a Charge- Coupled Device X-ray detector used in the X-ray Imaging Spectrometer developed for the ASTRO-E mission. We have evaluated X-ray Absorption Fine Structure (XAFS) around oxygen K edge in detail. A strong absorption peak of 45% is confirmed just above the oxygen K edge and an oscillatory structure follows whose amplitude decreases from 20% at the edge to less than 1% at 0.9 keV. We also show XAFS and discuss on a change of the response function around the silicon K edge. The discontinuity of the signal pulse height at the silicon K edge is less than 1.8 eV. We determine the thickness of silicon, silicon dioxide, and silicon nitride in the dead layer using the depth of the absorption edge.
A thin crystal with a thickness of approximately micrometers makes it possible to disperse incident x rays in a certain energy band, like a grating. We report a current performance of this new spectroscopic device. We show that Ti K (alpha) 1 and K (alpha) 2 lines are simultaneously diffracted to different directions making a two peaks. The experiment shows the energy resolving power of (E/(Delta) E > 3000) over approximately 24 eV range. A brief comparison will be presented among this thin crystal, gratings and Bragg crystals.
We report the characteristics of 'the thin crystal spectrometer,' which is a new technique for a x-ray spectrometer using a thin crystal. The reflection by a thin crystal in the 'Laue' geometry has a diffraction pattern with a finite width. The reflection angle does not need to be the same to the incident angle. The crystal structure along to the crystal plane makes the interference of the reflected x rays and the reflection angle becomes a function of an x-ray wave length. Therefore, the expected energy resolution of this type of the spectrometer is comparable with a usual Bragg crystal, whereas this new spectrometer can have a certain energy band. We report a simple experiment demonstrating this idea, where we show the energy resolution of (E/(Delta) E greater than 2000) and the energy band of ((Delta) E greater than 6 eV). The applications for a focusing optics are briefly presented.
We report the x-ray quantum efficiency of the XIS in the soft x-ray band between 0.5 keV and 2.2 keV. We also report the x-ray and optical transmission of the OBF. We obtained the quantum efficiency of the XIS of approximately 0.25 at 0.53 keV. We also obtained the x-ray transmission of approximately 0.65 at O K(alpha) and optical transmission below 5 X 10-5 in the range 400-950 nm.
Monitor of All-Sky X-ray Image (MAXI) is the first astrophysical payload for the Japanese Experiment Module (JEM) on the International Space Station. It is designed for monitoring all sky in the x-ray band. Two kinds of x-ray detectors, the gas slit camera and the solid-state slit camera, are employed. The former is the gas proportional counter with 1D position sensitivity and the latter is the x-ray CCD. We have designed and constructed the engineering models of both detectors. We have also developed an x-ray irradiation facility in the Tsukuba Space Center of National Space Development Agency of Japan. We report the status of the mission and introduce the x-ray irradiation facility.
The ASTRO-E X-ray Imaging Spectrometers (XISs) consists of four sets of X-ray CCD camera for the ASTRO-E mission. The XISs have been calibrated at Osaka University, Kyoto University, ISAS and MIT. The calibration experiment at Osaka focuses on the soft x-ray response of the XIS. The calibration of the XIS flight model has been performed since August 1998. We measured the signal-pulse height, the energy resolution and the quantum efficiency of the XIS as a function of energy, all of which are essential to construct the response function of the XIS. The detailed shape of the pulse-height-distribution are also investigated. We also constructed a numerical simulator of the XIS, which tracks the physical process in the CCD so as to reproduce the measured data. With a help of this simulator, we propose a model of the pulse-height-distribution of the XIS for single energy incident x-rays. The model consists of four components; two Gaussians, a constant, plus a triangle-shape component.
The x-ray imaging spectrometers (XIS) are x-ray CCD cameras on-board the Astro-E satellite launched in 2000. The XIS consists of 4 cameras, each of them will be installed on a focal plane of the Astro-E X-ray Telescope (XRT). The XIS not only have a higher sensitivity, which comes from a larger effective area of the XRT and thicker depletion layers of the XIS CCDs, than ASCA SIS. But also have several features that will overcome the radiation damage effects anticipated in the orbit. The calibration experiment at Osaka focuses on the soft x-ray response of the XIS. The calibration system employs a grating spectrometer which irradiates the CCD with dispersed x-rays. We have obtained preliminary results on the XIS proto model, including the energy-pulse-height relation, the energy-resolution relation, and the quantum efficiency at the energy range of 0.25-2.2 keV.
We report here the result of the structure measurement of a charge-coupled device (CCD) pixel with sub pixel resolution by using a new technique. The new technique makes use of a parallel x-ray beam and a metal mesh placed just in front of the CCD. The CCD camera we used in the first experiment, is a conventional system using the TC213 [Texas Instrument Japan (TIJ)] whose pixel size is 12 micrometers by 12 micrometers with one million pixels. The mesh has 4 micrometer diameter holes spaced at 12 micrometer intervals. We produced an efficiency map within a typical pixel showing the gate structure in detail. In the reconstruction process, we have to determine the mutual alignment between the CCD and the mesh in detail. The method we used can easily determine it with enough precision. By selecting single pixel events, we determined a pixel boundary. The distribution of two pixel split event can give us more information in the behavior of the primary charge cloud.
NASDA (National Space Development Agency of Japan) has selected MAXI as an early payload of the JEM (Japanese experiment module) Exposed Facility (EF) on the space station. MAXI is designed for all sky x-ray monitoring, and is the first astrophysical payload of four sets of equipment selected for JEM. MAXI will monitor the activities of about 1000 - 2000 x-ray sources. In the present design, MAXI is a slit scanning camera system which consists of two kinds of x-ray detectors; one with one-dimensional position sensitive proportional counters and the other with an x-ray CCD array employed for one-dimensional imaging. MAXI will be able to detect one milli-Crab x-ray sources in a few-day observations. The whole sky will be covered completely in every orbit of the space station. MAXI will be capable of monitoring variability of galactic and extragalactic sources on timescales of days with a sensitivity improvement of a factor of 5 or more over previous missions. NASDA and RIKEN have jointly begun the design and construction of MAXI. The payload will be ready for launch in 2003. In this paper we present the scientific objectives of MAXI, a basic design and some simulation results, after introducing the present status of JEM.
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