SIS photon detectors are niobium-based superconducting direct detectors for submillimeter-wave that show superior performance when compared with bolometric detectors for ground-based observations. We present the design and development of the SIS photon detectors together with optical and cryogenic components for wide field continuum observation system on Atacama Submillimeter Telescope Experiment (ASTE). Using antenna coupled distributed junctions, SIS photon detectors give wide band response in a 650-GHz atmospheric window as well as high current sensitivity, shot noise limited operation, fast response and high dynamic range. Optical noise equivalent power (NEP) was measured to be 1.6x10-16 W/Hz0.5 that is less than the background photon fluctuation limit for ground based submillimeter-wave observations. Fabrication of focal plane array with 9 detector pixels is underway to install in ASTE.
Readout electronics with Si-JFETs operating at about 100 K will be used for this array. Development of readout electronics for larger array is based on GaAs-JFETs operating at 0.3 K. For the purpose of installing 100 element array of SIS photon detectors, we have developed remotely operable low-vibration cryostat, which now cools bolometers for 350, 450, 850-µm observations down to 0.34 K. GM-type 4-K cooler and He3/He4 sorption cooler is used, which can be
remotely recycled to keep detectors at 0.34 K. Since we have large optical window for this cryostat, sapphire cryogenic window is used to block infrared radiation. The sapphire window is ante-reflection coated with SiO2 by chemical vapor deposition (CVD). The transmittance of the cryogenic window at 650 GHz is more than 95%.
High-sensitivity terahertz direct detectors using superconducting tunnel junctions were fabricated. They were designed for detecting terahertz radiation in the frequency range of 0.4 and 0.65 THz with the fractional bandwidth of above 10 percent. The results of their performance evaluation of five detector elements are presented. We show the results of the frequency response as well as that the absolute efficiency ranged from 10 to 30 percent and that the the
sensitivity was 1.9 x 10-16 W Hz-0.5 in noise equivalent power.
The Extreme Universe Space Observatory (EUSO) is a wide angle refractive telescope in near-ultraviolet wavelength region to detect extremely high energy cosmic rays by observing time-resolved air-fluorescence images of the extensive air showers from the International Space Station. The focal surface detector of the EUSO is designed to be a mosaic of multianode photomultipliers to realize the single photoelectron counting capability. We describe the current status of the conceptual design and the feasibility study of the focal surface of the EUSO telescope.
Superconduting tunnel junctions (STJ) have been developed to detect X-ray ~ visivle photons for application to astrophysics, particle physics, material physics, and so on. STJ are applicable as photon detectors with good energy resolution and a high photon-counting rate. STJ also have good efficiency because of their high absorption efficiency below 1 keV photon energy. That is advantageous in the observation of the faint objects with which the photon number is limited like astronomical objects and planetary plasma observation. STJ have potentials to open new windows of telescope. On the other hand, the progress of multilayers makes it possible to fabricated a normal incidence telescope (NIT) with high angular resolution and wide field of view up to 500 eV photon energyThe combination of the improved optical elements (multilayer) and STJ will enable us to design a new optical system in the near future. We demonstrate the design combined Visible - X-ray Wide-Band Space Telescope (WBST).
In order to broaden the applicability of neutron interferometry, a new type of multilayer cold-neutron interferometer based on a pair of etalons has been developed. The range of experimental application of conventional multilayer cold-neutron interferometer was limited due to the small spatial separation between the two coherent beams. Using etalons with an air gap of 9.75μm in spacing we have observed interference fringes with the contrast of 60%. The present results have demonstrated the feasibility of developing a cold neutron interferometer with a large path separation to carry out high precision measurements and new types of experiment.
We have been developing a neutron lens and prism based on neutron refractive optics. As a neutron has a magnetic dipole moment, it is accelerated in a magnetic field gradient. Thus, we can control a neutron beam free from beam attenuation using the magnetic field gradient. Moreover, its spin dependence of the acceleration is profitable in the case of using the polarized neutron beam. The sextupole magnetic field functions as a focusing or defocusing lens for neutrons depending on the neutron spin states. The focusing and defocusing effects of a prototype sextupole magnet was experimentally studied. By combining focusing and defocusing functions of the sextupole magnet, we can control the neutron beam shape and divergence more flexibly. Adiabatic and nonadiabatic field connections make it possible to realize the magnetic doublet system. A quadrupole magnetic field functions as a neutron prism, which were experimentally confirmed. The neutron spin and energy dependence of the refracting power is applicable to an analysis of the neutron spin and energy. In this paper, the details of the experimental results of the magnetic devices are described and their applications in the neutron scattering experiment are discussed.
We have developed compound refractive prism for cold neutrons. To prevent an increase in neutron absorption, we have developed prism array like a Fresnel lens. The prism characteristics were investigated with experimental and numerical simulation studies. We achieved transmission of 0.75 and refractive angle of 7.5 mrad for 15 neutrons with 49 layered prism array.
NASDA (National Space Development Agency of Japan) has selected MAXI as an early payload of the JEM (Japanese experiment module) Exposed Facility (EF) on the space station. MAXI is designed for all sky x-ray monitoring, and is the first astrophysical payload of four sets of equipment selected for JEM. MAXI will monitor the activities of about 1000 - 2000 x-ray sources. In the present design, MAXI is a slit scanning camera system which consists of two kinds of x-ray detectors; one with one-dimensional position sensitive proportional counters and the other with an x-ray CCD array employed for one-dimensional imaging. MAXI will be able to detect one milli-Crab x-ray sources in a few-day observations. The whole sky will be covered completely in every orbit of the space station. MAXI will be capable of monitoring variability of galactic and extragalactic sources on timescales of days with a sensitivity improvement of a factor of 5 or more over previous missions. NASDA and RIKEN have jointly begun the design and construction of MAXI. The payload will be ready for launch in 2003. In this paper we present the scientific objectives of MAXI, a basic design and some simulation results, after introducing the present status of JEM.