HiZ-GUNDAM is a future satellite mission whose mission concept was approved by ISAS/JAXA, and it is one of the future satellite candidates of JAXA’s competitive medium-class mission. HiZ-GUNDAM will lead time-domain astronomy in 2030s, and its key sciences are (1) exploration of the early universe with high-redshift gamma-ray bursts, and (2) contribution to the multi-messenger astronomy. Two mission payloads are aboard HiZ-GUNDAM to realize these two scientific issues. The wide field X-ray monitors which consist of Lobster Eye optics array and focal imaging sensor, monitor ~0.5 steradian field of view in 0.5–4 keV energy range. The near infrared telescope with an aperture size of 30 cm in diameter performs simultaneous 5-band photometric observation in 0.5–2.5 μm wavelength with Koester’s prism for X-ray transients discovered by Wide Field X-ray Monitor. In this paper, we introduce the mission overview of HiZ-GUNDAM while the information contained herein may change in future studies.
MeV gamma-ray observations provide unique information about nucleosynthesis, diffusion in our galaxy, low-energy cosmic rays, particle acceleration, and other phenomena. However, the detection sensitivity in this band is significantly lower than that in other bands due to a large background contamination. To address this issue, we are developing an electron-tracking Compton camera (ETCC) with powerful background rejection tools based on Compton recoil electron tracks. This will enable future observations to be conducted with greater sensitivity. We have successfully demonstrated the detection technology and performance of the ETCC with two balloon experiments. We are preparing for the next balloon flight, SMILE-3, to observe galactic diffusion gamma rays and some bright celestial objects.
HiZ-GUNDAM is a future satellite mission which will lead the time-domain astronomy and the multi-messenger astronomy through observations of high-energy transient phenomena. A mission concept of HiZ-GUNDAM was approved by ISAS/JAXA, and it is one of the future satellite candidates of JAXA’s medium-class mission. We are in pre-phase A (before pre-project) and elaborating the mission concept, mission/system requirements for the launch in the late 2020s. The main themes of HiZ-GUNDAM mission are (1) exploration of the early universe with high-redshift gamma-ray bursts, and (2) contribution to the multi-messenger astronomy. HiZ-GUNDAM has two kinds of mission payload. The wide field X-ray monitors consist of Lobster Eye optics array and focal imaging sensor, and monitor ~1 steradian field of view in 0.5 – 4 keV energy range. The near infrared telescope has an aperture size 30 cm in diameter, and simultaneously observes four wavelength bands between 0.5 – 2.5 μm. In this paper, we introduce the mission overview of HiZ-GUNDAM.
MeV gamma-ray astronomy in an energy range of hundreds of keV to tens of MeV is a unique window for observing nucleosynthesis, however this field has not opened up until recently because of imaging difficulties. Thus, we are developing an electron-tracking Compton camera (ETCC), which consists of a gaseous electron tracker and pixel scintillator arrays, as a next generation MeV gamma-ray telescope. Because the ETCC detects all parameters after Compton scattering, we can determine the momentum of incident gamma-rays with powerful background rejection. This ETCC has confirmed low-noise and high-sensitivity observations at high altitude through Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) in 2006 and SMILE-2+ in 2018. Therefore, we are planning scientific observations using an ETCC with an effective area of ∼10 cm2 for 0.3 MeV, a spatial resolution of ≤10 degrees for 0.5 MeV, and a field of view of 3 sr as the next step (SMILE-3). In this paper, we present the design of the SMILE-3 ETCC and its expected observations.
Y. Nakamura, T. Tanimori, A. Takada, Y. Mizumura, S. Komura, T. Kishimoto, T. Takemura, K. Yoshikawa, T. Tanigushi, K. Onozaka, K. Saito, T. Mizumoto, S. Sonoda, H. Kubo, Y. Matsuoka, Y. Nakamasu, S. Kurosawa, K. Miuchi, T. Sawano
KEYWORDS: Gamma radiation, Cameras, Point spread functions, Scintillators, Data acquisition, Gamma ray imaging, Sensors, Global Positioning System, Compton scattering
To establish imaging spectroscopy of cosmic gamma-rays from a few hundreds of keV to a few tens MeV, we developed an electron-tracking Compton camera (ETCC). The ETCC consists of a time projection chamber (TPC) and pixelated scintillator arrays (PSAs). The ETCC is superior to conventional gamma-ray imaging detectors of this energy band in that the arrival direction of an incident gamma-ray is firmly determined at one point and realizes high noise rejection efficiency. We performed a campaign to demonstrate the gamma-ray imaging performance of the ETCC at balloon altitude via the sub-MeV gamma-ray imaging loaded-on-balloon experiment 2+ (SMILE-2+). The balloon was launched on April 7, 2018, at 6:26 ACST (UTC +9:30) from Alice Springs, Australia. We performed a level flight for 26 hours at an altitude of 39.6 km. The main observation targets were the Galactic Center region and the Crab Nebula and we succeeded in observing them without any critical problems. The configuration of the flight model ETCC and the housekeeping data are described in detail.
A. Takada, T. Tanimori, H. Kubo, T. Mizumoto, Y. Mizumura, S. Komura, T. Kishimoto, T. Takemura, K. Yoshikawa, Y. Nakamasu, Y. Matsuoka, M. Oda, S. Miyamoto, S. Sonoda, D. Tomono, K. Miuchi, S. Kurosawa, T. Sawano
KEYWORDS: Point spread functions, Gamma radiation, Telescopes, Telescopes, Sensors, Electrons, Polarization, Space telescopes, Polarimetry, Photon polarization, Monte Carlo methods
The field of MeV gamma-ray astronomy has not opened up until recently owing to imaging difficulties. Compton telescopes and coded-aperture imaging cameras are used as conventional MeV gamma-ray telescopes; however their observations are obstructed by huge background, leading to uncertainty of the point spread function (PSF). Conventional MeV gamma-ray telescopes imaging utilize optimizing algorithms such as the ML-EM method, making it difficult to define the correct PSF, which is the uncertainty of a gamma-ray image on the celestial sphere. Recently, we have defined and evaluated the PSF of an electron-tracking Compton camera (ETCC) and a conventional Compton telescope, and thereby obtained an important result: The PSF strongly depends on the precision of the recoil direction of electron (scatter plane deviation, SPD) and is not equal to the angular resolution measure (ARM). Now, we are constructing a 30 cm-cubic ETCC for a second balloon experiment, Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-II. The current ETCC has an effective area of ~1 cm2 at 300 keV, a PSF of ~10° at FWHM for 662 keV, and a large field of view of ~3 sr. We will upgrade this ETCC to have an effective area of several cm2 and a PSF of ~5° using a CF4-based gas. Using the upgraded ETCC, our observation plan for SMILE-II is to map of the electron-positron annihilation line and the 1.8 MeV line from 26Al. In this paper, we will report on the current performance of the ETCC and on our observation plan.
A. Takada, T. Tanimori, H. Kubo, J. Parker, T. Mizumoto, Y. Mizumura, T. Sawano, K. Nakamura, Y. Matsuoka, S. Komura, S. Nakamura, M. Oda, K. Miuchi, S. Kurosawa
As a next generation MeV gamma-ray telescope, we develop an electron-tracking Compton camera (ETCC) that consists of a gaseous electron tracker surrounded by pixel scintillator arrays. The tracks of the Compton-recoil electron measured by the tracker restrict the incident gamma-ray direction to an arc region on the sky and reject background by using the energy loss rate dE/dx and a Compton-kinematics test. In 2013, we constructed, for a balloon experiment, a 30-cm-cubic ETCC with an effective area of ~1 cm2 for detecting sub-MeV gamma rays (5 σ detection of the Crab Nebula for 4 h). In future work, we will extend this ETCC to an effective area of ~10 cm2. In the present paper, we report the performance of the current ETCC.
We are now investigating and studying a small satellite mission HiZ-GUNDAM for future observation of gamma-ray bursts (GRBs). The mission concept is to probe “the end of dark ages and the dawn of formation of astronomical objects”, i.e. the physical condition of early universe beyond the redshift z > 7. We will consider two kinds of mission payloads, (1) wide field X-ray imaging detectors for GRB discovery, and (2) a near infrared telescope with 30 cm in diameter to select the high-z GRB candidates effectively. In this paper, we explain some requirements to promote the GRB cosmology based on the past observations, and also introduce the mission concept of HiZ-GUNDAM and basic development of X-ray imaging detectors.
In order to explore MeV gamma-ray astronomy, we have developed the Electron Tracking Compton Camera (ETCC)
consisting of a Time projection Chamber based on the micro pixel gas counter and pixel array scintillators. By measuring the track of a recoil electron in the TPC event by event, the ETCC measures the direction of each gamma-ray, and provides both good background rejection and an angular resolution over ~1 degree. A 1m-cubic size ETCC in satellite would be a good candidate for an All sky MeV gamma-ray survey of a wide band energy region of 0.1-100MeV with several ten times better sensitivity than COMPTEL. Already we carried out a balloon experiment with a small ETCC
(Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-I) in 2006, and measured diffuse cosmic and
atmosphere gamma rays. We are now constructing a 30cm-cube ETCC to catch gamma-rays from the Crab and
terrestrial gamma-ray bursts at the North Pole from 2013 (SMILE-II project). Terrestrial gamma-ray bursts are generated
by relativistic electron precipitation in the Pole region. Recently performance of tracking a recoil electron has been
dramatically improved, which may enable us to reach the ideal efficiency expected for the detector. In addition, we
mention about the unique capability to find a high-z Gamma-Ray Bursts beyond z>10 by ETCC, in particular long
duration GRBs over 1000 sec, which are expected to be due to POP-III stars.
We have developed a sub-MeV and MeV gamma-ray imaging Compton camera for use in gamma-ray astronomy; it
consists of a gaseous time-projection chamber (TPC) to convert the Compton scattering events and a scintillator array to
absorb photons. The TPC measures the energy and three-dimensional tracks of Compton-recoil electrons, while the pixel
scintillator arrays measure the energy and positions of scattered gamma rays. Therefore, our camera can reconstruct the
incident gamma rays, event by event, over a wide field of view of approximately 3 str. We are now developing a
Compton camera for a balloon-borne experiment.
We have developed an Electron-Tracking Compton Camera (ETCC) based on a gaseous micro Time Projection Chamber (ETCC) based on a gaseous micro Time Projection Chamber (μ-TPC) which measures the direction and the energy of the recoil electron and a GSO(Ce) scintillation camera which surrounds the μ-TPC
and measures the Compton scattered gamma ray. If not measuring a direction of a recoil electron, a direction of the
incident gamma-ray could only be reconstructed as a circle. Measuring the direction of the recoil electron reduces the Compton cone
to a point, and thus reconstructs the incident direction completely for a single photon and realizes the strong background
rejection. Using the ETCC with a detection volume of about 10cm×10cm×15cm, we had the balloon-borne experiment
supported by ISAS/JAXA in 2006 for the purpose of the observation of diffuse cosmic and atmospheric gamma rays. The ETCC
obtained about 200 photons with FOV of 3 str in 3 hours in the energy range from 100 keV to 1 MeV, and the obtained flux was
consistent with previous observations. On the basis of the results, we are developing the large size ETCC in order to improve the effective area for the next balloon
experiment. The large size ETCC has the detection volume of 23cm ×28cm×30cm which consists of the
23cm×28cm×30cm μ-TPC and the 30cm×30cm×1.3cm scintillation camera. Then we
obtained the gamma-ray image and investigated the first performances of the large size ETCC. The Angular Resolution Measure
(ARM) and the Scatter Plane Deviation (SPD) are 12.1 degree and 117 degree (FWHM) at 662keV, respectively, and the energy
resolution is 16.9%(FWHM) at 662keV.
We developed the new readout system for the pixel-readout μ-PIC (micro pixel chamber), which is one of the micro-pattern gas detectors that have been developed as a X-ray polarimeter so far. By using this system, we succeeded in achieving the sensitivity predicted by the simulation, i.e, the modulation factors, which is one of the most important factors for X-ray polarimeter as defined later in this paper, 0.24±0.08 at 8 keV, 0.18±0.07 at 15 keV in the neon-based gas mixture, and 0.18±0.04 in the argon-based gas although there still remain problems such as the pitch size among pixels and the non-uniformity of the response.
Akihiro Asahara, Y. Komiyama, G. Kosugi, Hidetoshi Kubo, S. Miyazaki, M. Mori, M. Nakagiri, D. Nishida, R. Ogasawara, R. Orito, K. Sakurazawa, T. Takata, Toru Tanimori, T. Usuda
We developed the gamma-ray camera for SUBARU infrared-optical telescope, named CheSS (Cherenkov light detecting System on Subaru). The CheSS was designed based on Imaging Atmospheric Cherenkov Technique (IACT) which has been established by detections of high energy gamma-ray sources in the last decade. According to our Monte Carlo simulation, the energy thresholds of the CheSS for the Crab are 30 GeV at zenith angle of 10 degrees, and the expected sensitivity for the unpulsed component can reach ~10σ level and more for pulsed one during 10 hours on-source pointing.
An intermediate electron multiplier for a MicroStrip Gas Chamber has been developed using a capillary plate. Our purpose was to develop a capillary plate as an intermediate electron multiplier able to be steadily operated under a medium gain of about one hundred and under a high counting rate. The capillary plate used here consists of a bundle of fine glass capillaries each with a diameter of 100 micrometers and a thickness of 1 mm, and has a 9.5 X 9 cm2 detection area and a 57% opening aperture ratio. In order to avoid the charge-up effect on the surfaces of the capillaries, some conductivity was added on the capillaries surfaces, and consequently about a 40 M(Omega) resistivity appeared between both sides of the plate. The conductivity dramatically improved the plates performance: the capillary plate was operated stable with counting rates up to 105 cps/mm2 and no decrease in the gas gain was observed. The capillary plate sufficiently satisfies the requirements for a pre-amplification device for an MSGC. In this paper, a 2D MSGC combined with the above conductive capillary plate was examined, and found to achieve stable operation with a sufficient gain under a high counting rate with no discharge problems.
This paper presents two novel applications of X-ray diffraction studies and their preliminary results using an MSGC. One involves the rapid analysis of single crystal structures using information on both the position and timing of incident X-rays. With this application, crystal structures of organic molecules could be obtained in a measurement time of 1 approximately 10 minutes. The other involves time-resolved X-ray diffraction measurements on the order of milliseconds. The time variation of the SAXS (small angle X-ray scattering) pattern of the protein solution was measured up to a frame time of 10 milli-seconds.
We have developed a microstrip gas chamber (MSGC) by using multi-chip technology which enables high-density assembly of bare LSI chips on a silicon board. Our MSGC was operated steadily with approximately 103 gain more than one week. An energy resolution of 15% (FWHM) for 5.9 keV x ray of 55Fe was obtained. With a very thin polyimide substrate of 16 micrometers thickness, two interesting phenomena were observed; one is a strong dependence of gains on the back plane potential, and the other is little time variation of gains. A new type of MSGC with a guarding mask of a thin polyimide layer on the cathode edges has been examined to reduce incidental electrical discharges between anode and cathode strips. Furthermore, a new approach to reduce the resistivity of the substrate has been examined. By these approaches, the stability of the high gain operation of approximately 104 has been drastically improved. In addition, we discuss the possibility of the application of MSGC to the coded mask x-ray imaging detector for astrophysics.
We plan to use an array of 9600 CsI(Tl) crystals as the electromagnetic (EM) shower detector for the asymmetric B-Factory at KEK. In order to determine the length of a crystal, we studied energy resolution, electron/pion separation, and other properties of 25 cm and 30 cm long CsI(Tl) crystals of a 3 X 3 matrix at GeV energy region. When electrons with energy of 1 GeV (4 GeV) is injected into the crystals, the energy resolution of 25 cm and 30 cm length is 2.7% (3.0%) and 2.4% (1.8%), respectively. The misidentification of a pion as an electron is less than 0.5% for energies above 1 GeV.
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