Tadayuki Takahashi

A data readout system with high-speed serial data link for balloonborne X-ray detectors

Data size of recent balloonborne detector is growing. High speed data readout is one of the key technologies for those detectors. A parallel data bus has been used for sending data with high speed. However, it causes problems in noise, mechanical size and power consumption. We apply the serial data link for our apparatus as a replacement of the parallel data link to solve those problems. We designed the hardware and firmware based on the SpaceWire protocol. Because of simple and flexible routing protocol of SpaceWire, the system was compact and has very high modularity. The protocol is implemented on Alteras FPGAs, APEX20KE and Cyclone. The speed of the serial data link was 48-53 Mbps. The maximum data rate to the computer was 4.5 MB/s.

SWIFT/BAT calibration and the estimated BAT hard x-ray survey sensitivity

In addition to providing the initial gamma-ray burst trigger and location, the Swift Burst Alert Telescope (BAT) will also perform an all-sky hard x-ray survey based on serendipitous pointings resulting from the study of gamma-ray bursts. BAT was designed with a very wide field-of-view (FOV) so that it can observe roughly 1/7 of the sky at any time. Since gamma-ray bursts are uniformly distributed over the sky, the final BAT survey coverage is expected to be nearly uniform. BATs large effective area and long sky exposures will produce a 15 - 150 keV survey with up to 30 times better sensitivity than any previous hard x-ray survey (e.g. HEAO A4). Since the sensitivity of deep exposures in this energy range is systematics limited, the ultimate survey sensitivity depends on the relative sizes of the statistical and systematic errors in the data. Many careful calibration experiments were performed at NASA/Goddard Space Flight Center to better understand the BAT instruments response to 15-150 keV gamma-rays incident from any direction within the FOV. Using radioactive sources of gamma-rays with known locations and energies, the Swift team can identify potential systematic errors in the telescopes performance and estimate the actual Swift hard x-ray survey sensitivity in flight. These calibration results will be discussed and a preliminary parameterization of the BAT instrument response will be presented. While the details of the individual BAT CZT detector response will be presented elsewhere in these proceedings, this talk will focus on the translation of the calibration experimental data into overall hard x-ray survey sensitivity.

Thermal Control Design of X-ray Astronomy Satellite ASTRO-H

The thermal control design of JAXA’s next major x-ray astronomy mission, ASTRO-H is presented. ASTRO-H will be launched in 2014 by HⅡA rocket from Tanegashima Space Center and is currently under detailed design. ASTRO-H is a three-axis stabilized spacecraft and its orbit altitude is 550 km and orbit inclination is 31 degree. ASTRO-H will observe black holes and clusters of galaxies by several science instruments: two telescopes and imagers for hard x-ray, two telescopes, a spectrometer, and an imager for soft x-ray, and two detectors for gamma rays. All instruments are mounted on honeycomb panels and the panels are supported by a truss structure. The skins of panels and truss poles are made of CFRP whose coefficient of thermal expansion is very low because of harsh requirement for preventing thermal distortion. The thermal design of the spacecraft and the science instruments present some engineering challenges requiring the high energy resolution and sensitivity to achieve desired science objectives. The results of detailed design and the plan of TTM TBT is presented.

The FOXSI-3 sounding rocket experiment (Conference Presentation)

The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket experiment aims to investigate fundamental questions about the high-energy Sun through direct imaging and spectroscopy of hard X-rays. The experiment utilizes Wolter-I type nested hard X-ray mirrors and fine-pitch semiconductor detectors, which are separated by a 2m focal length. Tol date, FOXSI has had two successful flights, on 2012 November 02 and 2014 December 11, demonstrating that the technology can measure small-scale energy releases (microflares and aggregated nanoflares) from the solar corona. The third flight for FOXSI is scheduled for August 2018. Significant improvements have been made on the FOXSI instrumentation, including upgraded optic modules with more nested mirror shells; specially designed collimators to mitigate the number of single bounce photons (ie., ghost rays) reaching the focal plane detector; and fine-pitch double-sided CdTe strip detectors to replace some of the Si-based hard X-ray detectors for better efficiency for hard X-rays. Furthermore, a CMOS based soft X-ray (SXR) instrument, “Phoenix”, will be added to FOXSI-3 by replacing one hard X-ray detector with a photon-counting SXR sensor. This will enable evaluation of the Sun via imaging spectroscopy simultaneously over a large X-ray energy range covering soft to hard X-rays. This paper will describe the overall instrument design of the FOXSI-3 experiment, which will be sensitive to solar soft and hard X-rays in the 1 – 20 keV range, as well as give a summary of insightful results and lessons from the first two flights. Possible observations for FOXSI-3 will also be discussed.

In vivo simultaneous imaging with 99m Tc and 18 F using a Compton camera

We have been developing a medical imaging technique using a Compton camera. This study evaluates the feasibility of clear imaging with 99mTc and 18F simultaneously, and demonstrates in vivo imaging with 99mTc and/or 18F. We used a Compton camera with silicon and cadmium telluride (Si/CdTe) semiconductors. We estimated the imaging performance of the Compton camera for 141 keV and 511 keV gamma rays from 99mTc and 22Na, respectively. Next, we simultaneously imaged 99mTc and 18F point sources to evaluate the cross-talk artifacts produced by a higher energy gamma-ray background. Then, in the in vivo experiments, three rats were injected with 99mTc-dimercaptosuccinic acid and/or 18F-fluorodeoxyglucose and imaged. The Compton images were compared with PET images. The rats were euthanized, and the activities in their organs were measured using a well counter. The energy resolution and spatial resolution were measured for the sources. No apparent cross-talk artifacts were observed in the practical-activity ratio (99mTc:18F  =  1:16). We succeeded in imaging the distributions of 99mTc and 18F simultaneously, and the results were consistent with the PET images and well counter measurements. Our Si/CdTe Compton camera can thus work as a multi-tracer imager, covering various SPECT and PET probes, with less cross-talk artifacts in comparison to the conventional Anger cameras using a collimator. Our findings suggest the possibility of human trials.

Monte-Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries.

Blue–shifted absorption lines from highly ionised iron are seen in some high inclination X-ray binary systems, indicating the presence of an equatorial disc wind. This launch mechanism is under debate, but thermal driving should be ubiquitous. X-ray irradiation from the central source heats disc surface, forming a wind from the outer disc where the local escape velocity is lower than the sound speed. The mass loss rate from each part of the disc is determined by the luminosity and spectral shape of the central source. We use these together with an assumed density and velocity structure of the wind to predict the column density and ionisation state, then combine this with a Monte-Carlo radiation transfer to predict the detailed shape of the absorption (and emission) line profiles. We test this on the persistent wind seen in the bright neutron star binary GX 13+1, with luminosity L/LEdd ∼ 0.5. We approximately include the effect of radiation pressure because of high luminosity, and compute line features. We compare these to the highest resolution data, the Chandra third order grating spectra, which we show here for the first time. This is the first physical model for the wind in this system, and it succeeds in reproducing many of the features seen in the data, showing that the wind in GX13+1 is most likely a thermal-radiation driven wind. This approach, combined with better streamline structures derived from full radiation hydrodynamic simulations, will allow future calorimeter data to explore the detail wind structure.

Residual Radiation Measurements at J-PARC MR Using the ASTROCAM 7000HS Newly Developed Radioactive Substance Visualization Camera

Mitsubishi heavy Industries, Ltd. (MHI) released the ASTROCAM 7000HS, a radioactive substance visualization camera. The ASTROCAM 7000HS incorporates the technologies for the gamma-ray detector used for the ASTRO-H satellite, which MHI has been developing under entrustment from and together with scientists at the Institute of Space and Astronautical Science (ISAS) at the Japan Aerospace Exploration Agency (JAXA), and the design was modified for use on land to commercialize the product [1]. MHI and Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS) performed on-site residual radiation measurements at the 50 GeV Main Ring (MR) of the Japan Proton Accelerator Research Complex (J-PARC) under collaboration with the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Agency (JAEA) and succeeded visualization of radiation hot spots of the accelerator components. The outline of the ASTROCAM 7000HS, the measurement principle and the first measurement results at the JPARC MR are described.

Thermal Control System of Microsatellite with Loop Heat Pipes

A thermal control system (TCS) of a microsatellite is proposed with loop heat pipes (LHPs) including bypass valves. “Free from restrictions in thermal design,” all instruments can be mounted anywhere on the internal side of the six structure panels making up the satellite without concern for the thermal design of the entire satellite and other instruments. The temperatures of all instruments are maintained under any attitude (i.e., external thermal environment) by concentrating dissipated heat in a “center heat source” (CHS) using six LHPs mounted between the CHS and structure panels and other heat transport devices. An experimental study and numerical simulation are conducted to validate the microsatellite TCS. In the experimental study, two LHPs are connected to a heat source and a heat load is input to a condenser to simulate the heat input to a radiator in orbit. The heat from the heat source is successfully transported via one LHP if heat is input to the radiator connected to the second LHP. Orbital thermal analyses of the microsatellite are also conducted. Typical low-Earth, geostationary, and polar orbits are investigated for spinning and three-axis stabilized satellites. Heat from the CHS is transported via the LHPs, and the CHS temperature is maintained within the required temperature range in all analysis cases as a result of bypass valve operation.