Xtend is one of the two telescopes onboard the X-ray imaging and spectroscopy mission (XRISM), which was launched on September 7th, 2023. Xtend comprises the Soft X-ray Imager (SXI), an X-ray CCD camera, and the X-ray Mirror Assembly (XMA), a thin-foil-nested conically approximated Wolter-I optics. A large field of view of 38′ × 38′ over the energy range from 0.4 to 13 keV is realized by the combination of the SXI and XMA with a focal length of 5.6 m. The SXI employs four P-channel, back-illuminated type CCDs with a thick depletion layer of 200 μm. The four CCD chips are arranged in a 2×2 grid and cooled down to −110°C with a single-stage Stirling cooler. Before the launch of XRISM, we conducted a month-long spacecraft thermal vacuum test. The performance verification of the SXI was successfully carried out in a course of multiple thermal cycles of the spacecraft. About a month after the launch of XRISM, the SXI was carefully activated and the soundness of its functionality was checked by a step-by-step process. Commissioning observations followed the initial operation. We here present pre- and post-launch results verifying the Xtend performance. All the in-orbit performances are consistent with those measured on ground and satisfy the mission requirement. Extensive calibration studies are ongoing.
XRISM (X-ray Imaging and Spectroscopy Mission) is an X-ray astronomy satellite developed in collaboration with JAXA, NASA and ESA. It successfully launched on Sept. 7, 2023. Two complementary X-ray telescopes, Resolve and Xtend are on-board XRISM. Resolve uses the pixelized X-ray micro calorimeter developed by NASA/GSFC and has very high energy resolution of 5 eV. On the other hand, Xtend uses an X-ray CCD camera as its focal plane detector which has high spatial resolution and a wide field of view. We evaluated the performance of the X-ray Mirror Assembly (XMA) for Xtend using data observed during the commissioning and PV phases of XRISM. To verify the imaging performance, the Point Spread Functions (PSF) generated from the observations of NGC 4151 and PDS 456 were compared with the ground-calibration results. The results show that the imaging performance of Xtend-XMA is not significantly different from that of the ground calibration, and that it meet the requirement. The effective area was verified by comparing the results of simultaneous observations of 3C 273 by XRISM and four X-ray astronomy satellites (Chandra, XMM-Newton, NuSTAR, and Swift). The results of the fitting of the X-ray spectrum of Xtend show no significant difference from the results of other satellites, suggesting the effective area used for fitting is correct. The on-axis position on the detector was estimated from the intensity of the Abell 2029 observations at four off-axis angles. The on-axis is about 40 arcsec away from the aim point, and the decrease in effective area at the aim point is less than 1%. Stray light observations of the Crab Nebula at 60 arcmin off-axis were obtained at two different satellite roll angles. The stray light intensity obtained at each roll angle was significantly different, verifying the dependence of the stray light on the roll angle.
The X-ray Imaging Spectroscopy Mission (XRISM) was launched on 2023-09-06 (UT). The onboard Xtend camera is now performing spectral imaging in the 0.4–13 keV band. Utilizing the wide field of view of Xtend of 38′ ×38′, we have been conducting searches for transient sources once a day, under the name of “XRISM/Xtend Transient Search (XTS)”. We report an Astronomer’s Telegram (ATel) within ∼1 day after downlinking the data from the satellite. Since the beginning of March 2024, when the XTS began full-scale operations, through early July, we issued nine ATel reports. The sensitivity limit of XTS is about 10−14 erg s−1cm−2 for a one-day observation, i.e. for an exposure time of ∼40 ks with the typical XRISM observing efficiency of about 50%. This sensitivity limit is orders of magnitude fainter than those obtained with all-sky survey missions such as MAXI and Einstein probe. It is comparable to those of Swift/XRT and eROSITA/SRG. XRISM observations are 4 days long on average, allowing for searches of sources that vary on time scales of more than one day, and down to the 10−14 erg s−1cm−2 flux range. Consequently, XRISM now plays a key role in time-domain astronomy.
The X-Ray Imaging and Spectroscopy Mission (XRISM) project at JAXA officially started in 2018. Following the development of onboard components, the proto-flight test was conducted from 2021 to 2023 at JAXA Tsukuba Space Center. The spacecraft was launched from JAXA Tanegashima Space Center on September 7, 2023 (JST), and onboard components, including the science instruments, were activated during the in-orbit commissioning phase. Following the previous report in 2020, we report the spacecraft ground tests, the launch operation, in-orbit operations, and the status and plan of initial and subsequent guest observations.
XRISM (X-Ray Imaging and Spectroscopy Mission) is an astronomical satellite with the capability of highresolution spectroscopy with the X-ray microcalorimeter, Resolve, and wide field-of-view imaging with the CCD camera, Xtend. The Xtend consists of the mirror assembly (XMA: X-ray Mirror Assembly) and detector (SXI: Soft X-ray Imager). The components of SXI include CCDs, analog and digital electronics, and a mechanical cooler. After the successful launch on September 6th, 2023 (UT) and subsequent critical operations, the mission instruments were turned on and set up. The CCDs have been kept at the designed operating temperature of −110°C after the electronics and cooling system were successfully set up. During the initial operation phase, which continued for more than a month after the critical operations, we verified the observation procedure, stability of the cooling system, all the observation options with different imaging areas and/or timing resolutions, and operations for protection against South Atlantic Anomaly. We optimized the operation procedure and observation parameters including the cooler settings, imaging areas for the specific modes with higher timing resolutions, and event selection algorithm. We summarize our policy and procedure of the initial operations for SXI. We also report on a couple of issues we faced during the initial operations and lessons learned from them.
The upper atmosphere at the altitude of 60–110 km, the mesosphere and lower thermosphere (MLT), has the least observational data of all atmospheres due to the difficulties of in-situ observations. Previous studies demonstrated that atmospheric occultation of cosmic X-ray sources is an effective technique to investigate the MLT. Aiming to measure the atmospheric density of the MLT continuously, we are developing an X-ray camera, “Soipix for observing Upper atmosphere as Iss experiment Mission (SUIM)”, dedicated to atmospheric observations. SUIM will be installed on the exposed area of the International Space Station (ISS) and face the ram direction of the ISS to point toward the Earth rim. Observing the cosmic X-ray background (CXB) transmitted through the atmosphere, we will measure the absorption column density via spectroscopy and thus obtain the density of the upper atmosphere. The X-ray camera is composed of a slit collimator and two X-ray SOI-CMOS pixel sensors (SOIPIX), and will stand on its own and make observations, controlled by a CPU-embedded FPGA “Zynq”. We plan to install the SUIM payload on the ISS in 2025 during the solar maximum. In this paper, we report the overview and the development status of this project.
We evaluate the single event tolerance of the x-ray silicon-on-insulator (SOI) pixel sensor named XRPIX, developed for the future x-ray astronomical satellite FORCE. In this work, we measure the cross-section of single event upset (SEU) of the shift register on XRPIX by irradiating heavy ion beams with linear energy transfer (LET) ranging from 0.022 to 68 MeV / ( mg/cm2 ) . From the SEU cross-section curve, the saturation cross-section and threshold LET are successfully obtained to be 3.4−0.9+2.9×10−10 cm2/bit and 7.3−3.5+1.9 MeV/(mg/cm2), respectively. Using these values, the SEU rate in orbit is estimated to be ≲ 0.1 event / year primarily due to the secondary particles induced by cosmic-ray protons. This SEU rate of the shift register on XRPIX is negligible in the FORCE orbit.
Xtend is a soft x-ray imaging telescope developed for the x-ray imaging and spectroscopy mission (XRISM). XRISM is scheduled to be launched in the Japanese fiscal year 2022. Xtend consists of the soft x-ray imager (SXI), an x-ray CCD camera, and the x-ray mirror assembly (XMA), a thin-foil-nested conically approximated Wolter-I optics. The SXI uses the P-channel, back-illuminated type CCD with an imaging area size of 31mm on a side. The four CCD chips are arranged in a 2×2 grid and can be cooled down to −120 °C with a single-stage Stirling cooler. The XMA nests thin aluminum foils coated with gold in a confocal way with an outer diameter of 45 cm. A pre-collimator is installed in front of the x-ray mirror for the reduction of the stray light. Combining the SXI and XMA with a focal length of 5.6m, a field of view of 38′ × 38′ over the energy range from 0.4 to 13 keV is realized. We have completed the fabrication of the flight model of both SXI and XMA. The performance verification has been successfully conducted in a series of sub-system level tests. We also carried out on-ground calibration measurements and the data analysis is ongoing.
In this multi-messenger astronomy era, all the observational probes are improving their sensitivities and overall performance. The Focusing on Relativistic universe and Cosmic Evolution (FORCE) mission, the product of a JAXA/NASA collaboration, will reach a 10 times higher sensitivity in the hard X-ray band (E > 10 keV) in comparison with any previous hard x-ray missions, and provide simultaneous soft x-ray coverage. FORCE aims to be launched in the early 2030s, providing a perfect hard x-ray complement to the ESA flagship mission Athena. FORCE will be the most powerful x-ray probe for discovering obscured/hidden black holes and studying high energy particle acceleration in our Universe and will address how relativistic processes in the universe are realized and how these affect cosmic evolution. FORCE, which will operate over 1–79 keV, is equipped with two identical pairs of supermirrors and wideband x-ray imagers. The mirror and imager are connected by a high mechanical stiffness extensible optical bench with alignment monitor systems with a focal length of 12 m. A light-weight silicon mirror with multi-layer coating realizes a high angular resolution of < 15′′ in half-power diameter in the broad bandpass. The imager is a hybrid of a brand-new SOI-CMOS silicon-pixel detector and a CdTe detector responsible for the softer and harder energy bands, respectively. FORCE will play an essential role in the multi-messenger astronomy in the 2030s with its broadband x-ray sensitivity.
We have been developing the SOI pixel detector “INTPIX” for space use and general purpose applications such as the residual stress measurement of a rail and high energy physics experiments. INTPIX is a monolithic pixel detector composed of a high-resistivity Si sensor, a SiO2 insulator, and CMOS pixel circuits utilizing Silicon-On- Insulator (SOI) technology. We have considered the possibility of using INTPIX to observe X-ray polarization in space. When the semiconductor detector is used in space, it is subject to radiation damage resulting from high-energy protons. Therefore, it is necessary to investigate whether INTPIX has high radiation tolerance for use in space. The INTPIX8 was irradiated with 6 MeV protons up to a total dose of 2 krad at HIMAC, National Institute of Quantum Science in Japan, and evaluated the degradation of the performance, such as energy resolution and non-uniformity of gain and readout noise between pixels. After 500 rad irradiation, which is the typical lifetime of an X-ray astronomy satellite, the degradation of energy resolution at 14.4 keV is less than 10%, and the non-uniformity of readout noise and gain between pixels is constant within 0.1%.
We have been developing monolithic active pixel sensors, X-ray SOIPIXs based on a Silicon-On-Insulator CMOS technology. Its event trigger output function offers a high time resolution better than ~10 usec. (1) We report the device structure optimized to achieve both low noise, a thick depletion layer, and to non-punch-through. (2) We succeeded in achieving an energy resolution of ~300 eV (FWHM) at 6 keV with a depletion layer of 300 um at room temperature by operating frequent reset to reduce the shot noise. (3) We present the development of "Digital X-ray SOIPIXs" having on-chip ADCs, DACs and readout sequencers.
We have been developing the monolithic active pixel detector XRPIX onboard the future x-ray astronomical satellite FORCE. XRPIX is composed of complementary metal-oxide-semiconductor pixel circuits, SiO2 insulator, and Si sensor by utilizing the silicon-on-insulator (SOI) technology. When the semiconductor detector is operated in orbit, it suffers from radiation damage due to x-rays emitted from celestial objects as well as cosmic rays. From previous studies, positive charges trapped in the SiO2 insulator are known to cause degradation of the detector performance. To improve the radiation hardness, we developed XRPIX equipped with a double-SOI (D-SOI) structure, introducing an additional silicon layer in the SiO2 insulator. This structure is aimed at compensating for the effect of the trapped positive charges. Although the radiation hardness of the D-SOI detectors to cosmic rays has been evaluated, the radiation effect due to x-ray irradiation has not been evaluated. Thus, we then conduct an x-ray irradiation experiment using an x-ray generator with a total dose of 10 krad at the SiO2 insulator, equivalent to 7 years in orbit. As a result of this experiment, the energy resolution in full-width half maximum for the 5.9 keV x-ray degrades by 17.8 % ± 2.8 % and the dark current increases by 89 % ± 13 % . We also investigate the physical mechanism of the increase in the dark current due to x-ray irradiation using technology computer-aided design simulation. It is found that the increase in the dark current can be explained by the increase in the interface state density at the Si / SiO2 interface.
X-ray silicon-on-insulator (SOI) pixel sensors, “XRPIX,” are being developed for the next-generation x-ray astronomical satellite, “FORCE.” The XRPIX is fabricated with the SOI technology, which makes it possible to integrate a high-resistivity Si sensor and a low-resistivity Si complementary metal oxide semiconductor (CMOS) circuit. The CMOS circuit in each pixel is equipped with a trigger function, allowing us to read out outputs only from the pixels with x-ray signals at the timing of x-ray detection. This function thus realizes high throughput and high time resolution, which enables to employ anti-coincidence technique for background rejection. A new series of XRPIX named XRPIX6E developed with a pinned depleted diode (PDD) structure improves spectral performance by suppressing the interference between the sensor and circuit layers. When semiconductor x-ray sensors are used in space, their spectral performance is generally degraded owing to the radiation damage caused by high-energy protons. Therefore, before using an XRPIX in space, it is necessary to evaluate the extent of degradation of its spectral performance by radiation damage. Thus, we performed a proton irradiation experiment for XRPIX6E for the first time at Heavy Ion Medical Accelerator in Chiba in the National Institute of Radiological Sciences. We irradiated XRPIX6E with high-energy protons with a total dose of up to 40 krad, equivalent to 400 years of irradiation in orbit. The 40-krad irradiation degraded the energy resolution of XRPIX6E by 25 ± 3 % , yielding an energy resolution of 260.1 ± 5.6 eV at the full-width half maximum for 5.9 keV X-rays. However, the value satisfies the requirement for FORCE, 300 eV at 6 keV, even after the irradiation. It was also found that the PDD XRPIX has enhanced radiation hardness compared to previous XRPIX devices. In addition, we investigated the degradation of the energy resolution; it was shown that the degradation would be due to increasing energy-independent components, e.g., readout noise.
We are developing an X-ray SOI pixel detector “XRPIX” for the next generation X-ray astronomical satellite “FORCE”. XRPIX is the detector using SOI (Silicon-On-Insulator) technology which makes it possible to integrate a high-resistivity Si sensor part and a low-resistivity Si CMOS circuit part. The CMOS circuit is equipped with the trigger function, which can read out only the output signal of the pixel where the X-ray is incident. This function realizes high throughput and high time resolution, enabling the background rejection with anticoincidence technique. A new series of XRPIX named XRPIX6E, we developed, with a Pinned Depleted Diode (PDD) structure improves the spectral performance by suppressing the interference between the sensor layer and the circuit layer. When semiconductor X-ray detectors are used in space, it is known that their spectral performance is degraded due to radiation damage caused by high-energy protons. Therefore, before using XRPIX in space, it is necessary to evaluate how much the spectral performance will be degraded by radiation damage. Then we performed proton irradiation experiment for XRPIX6E for the first time at HIMAC in National Institute of Radiological Sciences. We irradiated XRPIX with high-energy protons up to a total dose of 40 krad, equivalent to 400 years irradiation in orbit. As a result, the energy resolution in full width half maximum at the 5:9 keV degrades by 25 ± 3%, however, is better than the required performance of FORCE, 300 eV at 6 keV. It was also found that the PDD structure XRPIX has better radiation hardness than the previous XRPIX series. In addition, We investigated about the degradation of the energy resolution; it was found that the degradation would be due to increasing energy independent components, for example, readout noise.
We report current status of developing Soft X-ray Imager (SXI), the X-ray CCD camera onboard X-Ray Imaging and Spectroscopy Mission (XRISM). Four flight model (FM) CCDs have been selected considering several items including energy resolution at 5.9keV, CTI, dark current, etc. We have also completed calibration campaign for all the FM CCDs. Initial analyses show that the response function for monochromatic X-rays is basically the same as that of Hitomi CCDs. The focal plane including the single-stage Stirling cooler has been assembled. Production of key parts in SXI sensor body such as contamination blocking filter and onboard calibration source has been finished and they are waiting for assemble. The digitized signals of the CCD are corrected step by step before conversion to X-ray energy. We are preparing calibration database for the correction such as CTI, gain, and line redistribution function.
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.
We have been developing monolithic active pixel sensors, X-ray Astronomy SOI pixel sensors, XRPIXs, based on a Silicon-On-Insulator (SOI) CMOS technology as soft X-ray sensors for a future Japanese mission, FORCE (Focusing On Relativistic universe and Cosmic Evolution). The mission is characterized by broadband (1-80 keV) X-ray imaging spectroscopy with high angular resolution (< 15 arcsec), with which we can achieve about ten times higher sensitivity in comparison to the previous missions above 10 keV. Immediate readout of only those pixels hit by an X-ray is available by an event trigger output function implemented in each pixel with the time resolution higher than 10 µsec (Event-Driven readout mode). It allows us to do fast timing observation and also reduces non-X-ray background dominating at a high X-ray energy band above 5{10 keV by adopting an anti-coincidence technique. In this paper, we introduce our latest results from the developments of the XRPIXs. (1) We successfully developed a 3-side buttable back-side illumination device with an imaging area size of 21.9 mm x 13.8 mm and an pixel size of 36 µm x 36 µm. The X-ray throughput with the device reaches higher than 0.57 kHz in the Event-Driven readout mode. (2) We developed a device using the double SOI structure and found that the structure improves the spectral performance in the Event-Driven readout mode by suppressing the capacitive coupling interference between the sensor and circuit layers. (3) We also developed a new device equipped with the Pinned Depleted Diode structure and confirmed that the structure reduces the dark current generated at the interface region between the sensor and the SiO2 insulator layers. The device shows an energy resolution of 216 eV in FWHM at 6.4 keV in the Event-Driven readout mode. .
We have developed SOIPIXs based on the CMOS SOI technology for the future X-ray astronomical satellite. SOIPIXs has the event trigger output function implemented in each pixel offers microsecond time resolution and its event trigger function enables to separate celestial X-rays and non-X-ray background by combining the anticoincidence system and to reduce the non-X-ray background that dominates the high X-ray energy band above 5-10 keV. A fully depleted SOIPIXs with a 300-500 um thick depletion layer and back illumination offers wide band coverage of 0.3-40 keV.
In order to use XRPIXs in space environment, to investigate the radiation hardness of XRPIXs is important because semiconductor detectors such as XRPIXs and CCDs are damaged by interacting with many cosmic rays which are composed primarily energy protons in orbit. The damage causes the increase of dark current and the degradation of the performance such as the energy resolution of XRPIXs.
To evaluate the radiation hardness of XRPIXs, we have carried out the radiation damage test at the heavy ion medical accelerator (HIMAC) in Japan. For this experiment, we used the XRPIX2b-FZ (Takeda et al, 2015) which was the front illuminated XRPIX with 300um thick depletion layer. XRPIX2b-FZ has 144 x 144 pixels and the pixel size is 30um x 30 um. We installed XRPIX2b-FZ in the vacuum chamber and cooled it around -80 C degree. The proton beam flux was much strong for our purpose of this experiment, we set the 3 um thick Au film as a scatterers in the cubic flange in front of vacuum chamber in order to reduce the beam flux. We introduced the scattered proton beam to the two direction of the downstream of the beam line, and one was irradiated to XRPIX2b-FZ in the vacuum chamber and the other was irradiated to the faraday cup connected to the cubic flange to monitor the scattered beam flux. We also obtained the total doze of proton beam using the faraday cup.
We irradiated the proton beam to XRPIX2b-FZ until the total irradiation dose reached 10 krad while increasing the irradiation dose and evaluated the performance such as leak current, gain and energy resolution using X-ray from 109 Cd after the proton irradiation of 1 rad, 400 rad, 1 k rad, 4 k rad, and 10 krad.
From above experimental results, we found that the gain and the energy resolution was degraded by 0.2 % and 10 % respectively with 400 rad whose equivalent time in orbit was 3.5 years, and the gain and energy resolution became worse by 0.8 % and 32 % respectively after irradiation of 4k rad. We investigated the reason of the degradation of the energy resolution and found the degradation was mainly caused by the increasing the read out noise. We also found the number of bad pixels clearly increased by about 10 times after the irradiation of 10 krad.
X-ray Astronomy Recovery Mission (XARM) scheduled to be launched in early 2020’s carries two soft X-ray telescopes. One is Resolve consisting of a soft X-ray mirror and a micro calorimeter array, and the other is Soft X-ray Imaging Telescope (Xtend), a combination of an X-ray mirror assembly (XMA) and an X-ray CCD camera (SXI). Xtend covers a field of view (FOV) of 38′ × 38′ , much larger than that of Resolve (3′ × 3 ′ ) with moderate energy resolution in the energy band from 0.4 keV to 13 keV, which is similar to that of Resolve (from 0.3 keV to 12 keV). Simultaneous observations of both telescopes provide complimentary data of X-ray sources in their FOV. In particular, monitoring X-ray sources outside the Resolve FOV but inside the Xtend FOV is important to enhance the reliability of super high resolution spectra obtained with Resolve. Xtend is also expected to be one of the best instruments for low surface brightness X-ray emissions with its low non X-ray background level, which is comparable to that of Suzaku XIS. The design of Xtend is almost identical to those of Soft X-ray Telescope (SXT) and Soft X-ray Imager (SXI) both on board the Hitomi satellite. However, several mandatory updates are included. Updates for the CCD chips are verified with experiment using test CCD chips before finalizing the design of the flight model CCD. Fabrication of the foils for XMA has started, and flight model production of the SXI is almost ready.
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 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 Imager (SXI) is an imaging spectrometer using charge-coupled devices (CCDs) aboard the Hitomi x-ray observatory. The SXI sensor has four CCDs with an imaging area size of 31 mm×31 mm arranged in a 2×2 array. Combined with the x-ray mirror, the Soft X-ray Telescope, the SXI detects x-rays between 0.4 and 12 keV and covers a 38′×38′ field of view. The CCDs are P-channel fully depleted, back-illumination type with a depletion layer thickness of 200 μm. Low operation temperature down to −120°C as well as charge injection is employed to reduce the charge transfer inefficiency (CTI) of the CCDs. The functionality and performance of the SXI are verified in on-ground tests. The energy resolution measured is 161 to 170 eV in full width at half maximum for 5.9-keV x-rays. In the tests, we found that the CTI of some regions is significantly higher. A method is developed to properly treat the position-dependent CTI. Another problem we found is pinholes in the Al coating on the incident surface of the CCDs for optical light blocking. The Al thickness of the contamination blocking filter is increased to sufficiently block optical light.
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 report here the performance of the SXI on ASTRO-H that was started its operation from March,02 2016. The SXI consists of 4 CCDs that cover 38' X 38' sky region. They are P-channel back-illumination type CCD with a depletion layer of 200 μm. Charge injection (CI) method is applied from its beginning of the mission. Two single stage sterling coolers are equipped with the SXI while one of them has enough power to cool the CCD to -110°C. There are two issues in the SXI performance: one is a light-leak and the other is a cosmic-ray echo. The light-leak is due to the fact that the day-Earth irradiates visible lights onto the SXI body through holes in the satellite base plate. It can be avoided by selecting targets not on the anti-day-Earth direction. The cosmic-ray echo is due to the improper parameter values that is fixed by revising them with which the cosmic-ray echo does not affect the image. Using the results of RXJ1856.5-3754, we confirm that the possible contaminants on the CCD is well within our expectation.
The Soft X-ray Imager (SXI) is an X-ray CCD camera onboard the ASTRO-H X-ray observatory. The CCD chip used is a P-channel back-illuminated type, and has a 200-µm thick depletion layer, with which the SXI covers the energy range between 0.4 keV and 12 keV. Its imaging area has a size of 31 mm x 31 mm. We arrange four of the CCD chips in a 2 by 2 grid so that we can cover a large field-of-view of 38’ x 38’. We cool the CCDs to -120 °C with a single-stage Stirling cooler. As was done for the CCD camera of the Suzaku satellite, XIS, artificial charges are injected to selected rows in order to recover charge transfer inefficiency due to radiation damage caused by in-orbit cosmic rays. We completed fabrication of flight models of the SXI and installed them into the satellite. We verified the performance of the SXI in a series of satellite tests. On-ground calibrations were also carried out and detailed studies are ongoing.
X-ray CCD operated onboard satellite are contaminated by outgas from organic material used in satellites. This contamination causes a significant reduction in the detection sensitivity of X-ray detectors.
In order to prevent such contamination to the Back-Illuminated CCD (BI-CCD) of the Soft X-ray Imager
(SXI) onboard ASTRO-H, we have developed a Contamination Blocking Filter (CBF), which consists of ~30nm thick Aluminum and ~200nm thick Polyimide. The CBF is be placed on the top of the CCD camera hood and is required to have a high X-ray transmission in order to take advantage of the high detection efficiency of BI-CCD.
We measured the X-ray transmission of three flight candidates of the CBF last October at the SPring-8 and obtained the X-ray transmission of three CBFs in the soft X-ray energy from 0.2 to 1.8 keV which covers the absorption edges around C-K, N-K, O-K, and Al-K including X-ray absorption fine structure (XAFS). In these measurements, we found three CBFs have high X-ray transmission below 2ke V, e.g. ~70% at around 0.5 keV, and determined the thickness of Al and Polyimide to be 220 nm and ~50 nm, respectively. We will calculate the response function of SXI including these results.
Soft X-ray Imager (SXI) is a CCD camera onboard the ASTRO-H satellite which is scheduled to be launched in 2015. The SXI camera contains four CCD chips, each with an imaging area of 31mm x 31 mm, arrayed in mosaic, covering the whole FOV area of 38′ x 38′. The CCDs are a P-channel back-illuminated (BI) type with a depletion layer thickness of 200 _m. High QE of 77% at 10 keV expected for this device is an advantage to cover an overlapping energy band with the Hard X-ray Imager (HXI) onboard ASTRO-H. Most of the flight components of the SXI system are completed until the end of 2013 and assembled, and an end-to-end test is performed. Basic performance is verified to meet the requirements. Similar performance is confirmed in the first integration test of the satellite performed in March to June 2014, in which the energy resolution at 5.9 keV of 160 eV is obtained. In parallel to these activities, calibrations using engineering model CCDs are performed, including QE, transmission of a filter, linearity, and response profiles.
KEYWORDS: Avalanche photodetectors, X-rays, Field effect transistors, Resistance, Crystals, Sensors, Hard x-rays, Scintillators, Analog electronics, Stanford Linear Collider
WF-MAXI is a mission to detect and localize X-ray transients with short-term variability as gravitational-wave (GW) candidates including gamma-ray bursts, supernovae etc. We are planning on starting observations by WF-MAXI to be ready for the initial operation of the next generation GW telescopes (e.g., KAGRA, Advanced LIGO etc.). WF-MAXI consists of two main instruments, Soft X-ray Large Solid Angle Camera (SLC) and Hard X-ray Monitor (HXM) which totally cover 0.7 keV to 1 MeV band. HXM is a multi-channel array of crystal scintillators coupled with APDs observing photons in the hard X-ray band with an effective area of above 100 cm2. We have developed an analog application specific integrated circuit (ASIC) dedicated for the readout of 32-channel APDs' signals using 0.35 μm CMOS technology based on Open IP project and an analog amplifier was designed to achieve a low-noise readout. The developed ASIC showed a low-noise performance of 2080 e- + 2.3 e-/pF at root mean square and with a reverse-type APD coupled to a Ce:GAGG crystal a good FWHM energy resolution of 6.9% for 662 keV -rays.
A formation flight astronomical survey telescope (FFAST) is a new project that will cover a large sky area in hard X-ray. In particular, it will focus on the energy range up to 80keV. It consists of two small satellites that will go in a formation flight. One is an X-ray telescope satellite carrying a super mirror, and the other is a detector satellite carrying an SDCCD. Two satellites are put into a low earth orbit in keeping the separation of 12m. This will survey a large sky area at hard X-ray region to study the evolution of the universe.
WF-MAXI is a soft X-ray transient monitor proposed for the ISS/JEM. Unlike MAXI, it will always cover a large field of view (20 % of the entire sky) to detect short transients more efficiently. In addition to the various transient sources seen by MAXI, we hope to localize X-ray counterparts of gravitational wave events, expected to be directly detected by Advanced-LIGO, Virgo and KAGRA in late 2010's. The main instrument, the Soft X-ray Large Solid Angle Cameras (SLC) is sensitive in the 0.7-12 keV band with a localization accuracy of ~ 0:1°. The Hard X-ray Monitor (HXM) covers the same sky field in the 20 keV-1 MeV band.
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.
Wide-Field MAXI (WF-MAXI) planned to be installed in Japanese Experiment Module “Kibo” Exposed Facility of the international space station (ISS). WF-MAXI consists of two types of cameras, Soft X-ray Large Solid Angle Camera (SLC) and Hard X-ray Monitor (HXM). HXM is multi-channel arrays of CsI scintillators coupled with avalanche photodiodes (APDs) which covers the energy range of 20 - 200 keV. SLC is arrays of CCD, which is evolved version of MAXI/SSC. Instead of slit and collimator in SSC, SLC is equipped with coded mask allowing its field of view to 20% of all sky at any given time, and its location determination accuracy to few arcminutes. In older to achieve larger effective area, the number of CCD chip and the size of each chip will be larger than that of SSC. We are planning to use 59 x 31 mm2 CCD chip provided by Hamamatsu Photonics. Each camera will be quipped with 16 CCDs and total of 4 cameras will be installed in WF-MAXI. Since SLC utilize X-ray CCDs it must equip active cooling system for CCDs. Instead of using the peltier cooler, we use mechanical coolers that are also employed in Astro-H. In this way we can cool the CCDs down to -100C. ISS orbit around the earth in 90 minutes; therefore a point source moves 4 arcminutes per second. In order to achieve location determination accuracy, we need fast readout from CCD. The pulse heights are stacked into a single row along the vertical direction. Charge is transferred continuously, thus the spatial information along the vertical direction is lost and replaced with the precise arrival time information. Currently we are making experimental model of the camera body including the CCD and electronics for the CCDs. In this paper, we show the development status of SLC.
We have been developing monolithic active pixel sensors, known as Kyoto’s X-ray SOIPIXs, based on the CMOS SOI (silicon-on-insulator) technology for next-generation X-ray astronomy satellites. The event trigger output function implemented in each pixel offers microsecond time resolution and enables reduction of the non-X-ray background that dominates the high X-ray energy band above 5–10 keV. A fully depleted SOI with a thick depletion layer and back illumination offers wide band coverage of 0.3–40 keV. Here, we report recent progress in the X-ray SOIPIX development. In this study, we achieved an energy resolution of 300 eV (FWHM) at 6 keV and a read-out noise of 33 e- (rms) in the frame readout mode, which allows us to clearly resolve Mn-Kα and Kβ. Moreover, we produced a fully depleted layer with a thickness of 500 μm. The event-driven readout mode has already been successfully demonstrated.
The Soft X-ray Imager, SXI, is an X-ray CCD camera onboard the ASTRO-H satellite to be launched in 2015. ASTRO-H will carry two types of soft X-ray detector. The X-ray calorimeter, SXS, has an excellent energy resolution with a narrow field of view while the SXI has a medium energy resolution with a large field of view, 38′ square. We employ 4 CCDs of P-channel type with a depletion layer of 200 μm. Having passed the CDR, we assemble the FM so that we can join the final assembly. We present here the SXI status and its expected performance in orbit.
The scientific objective of the X-ray Advanced Concepts Testbed (XACT) is to measure the X-ray polarization
properties of the Crab Nebula, the Crab pulsar, and the accreting binary Her X-1. Polarimetry is a powerful tool for
astrophysical investigation that has yet to be exploited in the X-ray band, where it promises unique insights into neutron
stars, black holes, and other extreme-physics environments. With powerful new enabling technologies, XACT will
demonstrate X-ray polarimetry as a practical and flight-ready astronomical technique. Additional technologies that
XACT will bring to flight readiness will also provide new X-ray optics and calibration capabilities for NASA missions
that pursue space-based X-ray spectroscopy, timing, and photometry.
Soft X-ray Imager (SXI) is a CCD camera onboard the ASTRO-H satellite which is scheduled to be launched
in 2014. The SXI camera contains four CCD chips, each with an imaging area of 31mm×
31 mm, arrayed in
mosaic, which cover the whole FOV area of 38' ×
38'. The SXI CCDs are a P-channel back-illuminated (BI) type
with a depletion layer thickness of 200 μm. High QE of 77% at 10 keV expected for this device is an advantage
to cover an overlapping energy band with the Hard X-ray Imager (HXI) onboard ASTRO-H. Verification with
engineering model of the SXI has been performed since 2011. Flight model design was fixed and its fabrication
has started in 2012.
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 on the development of the X-ray CCD for the soft X-ray imager (SXI) onboard ASTRO-H. SXI CCDs are
P-channel, back-illuminated type manufactured by Hamamatsu Photonics K. K.
Experiments with prototype CCD for the SXI shows the device has a depletion layer as thick as 200μm, high efficiency for hard X-rays.
By irradiating soft X-rays to the prototype CCD for the SXI.
At the same time, we found a significant low energy tail in the soft X-ray response of the SXI prototype CCD.
We thus made several small size CCD chips with different treatment in processing the surface layers.
CCDs with one of the surface layers treatment show a low energy tail of
which intensity is one order of magnitude smaller than that of the original SXI prototype CCD for 0.5keV X-ray incidence.
The same treatment will be applied to the flight model CCDs of the SXI.
We also performed experiments to inject charge with the SXI prototype CCD, which is needed to mitigate the radiation damage in the orbit.
We investigated the operation conditions of the charge injection.
Using the potential equilibration method, charges are injected in each column homogeneously,
though the amount of the charge must be larger than 20ke-.
Soft X-ray Imager (SXI) is a CCD camera onboard the ASTRO-H satellite which is scheduled to be launched
in 2014. The SXI camera contains four CCD chips, each with an imaing aread of 31mmx31 mm, arrayed in
mosaic, which cover the whole FOV area of 38'x38'. The SXI CCD of which model name is HPK Pch-NeXT4
is a P-channel type, back-illuminated, fully depleted device with a thickness of 200μm. We have developed an
engineering model of the SXI camera body with coolers, and analog electronics for them. Combined with the
bread board digital electronics, we succeeded in operation the whole the SXI system. The CCDs are cooled down
to -120°C with this system, and X-rays from 55Fe sources are detected. Although optimization of the system is in
progress, the energy resolution of typical 200 eV and best 156 eV (FWHM) at 5.9 keV are obtained. The readout
noise is 10 e- to 15 e-, and to be improved its goal value of 5 e-. On-going function tests and environment tests
reveal some issues to be solved until the producntion of the SXI flight model in 2012.
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.
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 are designing an X-ray CCD camera (SXI) for ASTRO-H, including many new items. We have developed
the CCD, CCD-NeXT4, that is a P-channel type CCD. It has a thick depletion layer of 200μm with an imaging
area of 30mm square. Since it is back-illuminated, it has a good low energy response and is robust against the
impact of micro-meteorites. We will employ 4 chips to cover the area of 60mm square. A mechanical rather
than peltier cooler will be employed so that we can cool the CCD to -120°C. We will also introduce an analog
ASIC that is placed very close to the CCD. It performs well, having a similar noise level to that assembled by
using individual parts used on SUZAKU. We also employ a modulated X-ray source (MXS), that improves the
accuracy of the calibration. The SXI will have one of the largest SΩ among various satellites.
The Soft X-ray Imager (SXI) is the X-ray CCD detector system on board the NeXT mission that is to be launched around 2013. The system consists of a camera, an SXI-specific data processing unit (SXI-E) and a CPU unit commonly used throughout the NeXT satellite. All the analog signal handling is restricted within the camera unit, and all the I/O of the unit are digital.
The camera unit and SXI-E are connected by multiple LVDS lines, and SXI-E and the CPU unit will be connected by a SpaceWire (SpW) network. The network can connect SXI-E to multiple CPU units (the formal SXI CPU and neighbors) and all the CPU units in the network have connections to multiple neighbors: with this configuration, the SXI system can work even in the case that one SpW connection or the formal SXI CPU is down.
The main tasks of SXI-E are to generate the CCD driving pattern, the acquisition of the image data stream and HK data supplied by the camera and transfer them to the CPU unit with the Remote Memory Access Protocol (RMAP) over SpW. In addition to them, SXI-E also detects the pixels whose values are higher than the event threshold and both adjacent pixels in the same line, and send their coordinates to the CPU unit. The CPU unit can reduce its load significantly with this information because it gets rid of the necessity to scan whole the image to detect X-ray events.
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 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.
We present the current status of soft X-ray calibration of X-ray CCD cameras, X-ray Imaging Spectrometer (XIS), onboard Astro-E2. We perform soft X-ray calibration of four front illuminated (FI) CCD cameras and two back illuminated (BI) CCD cameras, among which four cameras will be selected to be installed on the satellite. The calibration aims to measure the quantum efficiency and re-distribution function of the CCDs as a function of incident X-ray energy. A soft X-ray spectrometer is used to measure these items. In addition, we employ a gas proportional counter and an XIS engineering unit as reference detectors for the quantum efficiency measurement. We describe how we calibrate the absolute quantum efficiency of the XIS using these instruments. We show some of the preliminary results of the calibration including quick look results of BI CCD cameras.
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.
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.
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.
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.
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