Junji Inatani

An Octave Bandwidth SIS Mixer for Accurate and Compact Terahertz Spectrometers

A SIS mixer with RF bandwidth of 1 octave is designed, fabricated, and characterized. The mixer chip consists of 8 Nb/AlOx/Nb junctions connected in parallel through Nb/SiO2/Nb microstrip lines (MSL), a twin-slot antenna, and a 3-stage MSL transformer. Experimentally, the 2.5 dB RF band is found to be 230-440 GHz, which agrees quantitatively with theoretical calculation. Receiver noise temperature Trx is measured as 260-680 K in the band. After correction for IF-amplifler noise and beam-splitter reflectivity, the noise is 170-320 K, i.e., 13-20 times of the quantum noise. The sensitivity flatness in the band can be improved to 1.9 dB by further optimization of the transformer.

Flux-flow-type Josephson oscillator consisting of epitaxial NbCN/MgO/NbCN junction

Flux-flow-type Josephson oscillators consisting of epitaxial NbCN/MgO/NbCN junctions were fabricated and their current-voltage (I-V) characteristics were measured in various magnetic fields to evaluate their oscillation characteristics. On the I-V curve for a fabricated oscillator, clear current steps were observed up to 3 mV, indicating that oscillation occurs up to 1.4 THz. Using a theoretical model, available output power for the oscillator was calculated to be in the range from 20 mu W to 40 mu W in the frequency range from 500 GHz to 1.2 THz.<<ETX>>

Fabrication of all-NbCN flux-flow oscillators with a tapered slotline antenna and off-chip detection of their radiation power

All-NbCN flux-flow oscillators (FFO) with tapered slotline antenna (TSA) were fabricated on MgO substrates. A five-step microstrip transformer was used to couple an FFO, which has a low impedance, to a TSA having a high impedance, The microstrip transformer is designed to have a return loss more than 20 dB at the center frequency. We have measured submillimeter wave radiation from the oscillators using an off-chip silicon-composite bolometer. Radiation from a fabricated FFO was detected in a bias voltage range from 1.18 mV to 1.48 mV, which corresponds to a frequency range from 570 GHz to 710 GHz.<<ETX>>

Phase locking of SWL array junctions in submillimeter mixing

We have fabricated a submillimeter mixer with two SWL (short-weak-link) junctions connected in series. This mixer has been used for a 337 GHz fundamental mixing. It has been found that these two junctions independently contribute the IF (intermediate frequency) output when the applied LO (local oscillator) power is small, but that they behave just as a single junction for the increased LO power.

The optical design and physical optics analysis of a cross-Dragonian telescope for LiteBIRD

The Lite satellite for the studies of B-mode polarization and Inflation from the cosmic microwave background (CMB) Radiation Detection (LiteBIRD) is a next generation CMB satellite dedicated to probing the inflationary universe. It has two telescopes, Low Frequency Telescope (LFT) and High Frequency Telescope (HFT) to cover wide observational bands from 34 GHz to 448 GHz. In this presentation, we report the optical design and characterization of the LFT. We have used the CODE-V to obtain the LFT optical design based on a cross- Dragonian telescope. It is an image-space telecentric system with an F number of 3.5 and 20 x 10 degrees2 field of view. The main, near and far side lobes at far-field have been calculated by using a combination of HFSS and GRASP 10. It is revealed that the LFT telescope has good main lobe properties to satisfy the requirements. On the other hand, the side lobes are affected by the stray light that stems from the triple reflection and the direct path from feed. In order to avoid the stray light, the way to block these paths is now under study.

Demonstration of superconducting sub-millimeter-wave limb emission sounder (SMILES) for observing trace gases in the middle atmosphere using the exposed facility of the Japanese experimental module (JEM) of the international space station

The sub-millimeter wavelength region is advantageous for high-precision observations of trace species in the stratosphere. A Superconducting Sub-Millimeter-wave Limb Emission Sounder (SMILES) is scheduled to demonstrate the measurements of extremely faint sub-millimeter-wave emissions of the atmospheric trace gases on the Exposed Facility (EF) of the Japanese Experimental Module (JEM) of the International Space Station in 2003. The applications of superconductivity and mechanical 4K-refrigerator in space will be demonstrated in the experiment. JEM/SMILES obtains the diurnal and seasonal variability in the global three-dimensional distributions of the stratospheric trace gases for quantitative understanding of the stratospheric ozone depletion and its effect on the climate change with respect to the relationships among chemical reaction processes and their relationships with atmospheric dynamics. JEM/SMILES utilizes the 640GHz band to measure the vertical profiles of trace gases involved in the stratospher...

Fine Structure of Molecular Clouds within 1 Minute of Arc of the Galactic Center

We have observed the HCN(J=1-0) line in the vicinity of the galactic center with the 18″ beam of the Nobeyama 45-m telescope. Profiles were taken at 53 points within 1 arcmin from the galactic nucleus [R.A. = 17h42m29.29s, Dec. = −28°59′17.6″ (1950)] with a 10″ grid (see figure 1). A SSB cooled-mixer receiver (TRX = 600 K) and a wideband AOS (acousto-optical radiospectrometer) with 250 kHz resolution were used.

CO and OH in the Galactic Center Region

The two-dimensional distribution of molecular clouds in the galactic center region has been investigated in the CO 115 GHz line and in the OH 1665 and 1667 MHz lines. As the former is an emission line, we can find molecular clouds without the unavoidable bias to continuum sources which is inherent in a survey of OH absorption lines. Because the CO line is usually optically thick, the brightness temperature of the line is directly related to the kinetic temperature of the cloud. On the other hand, the real optical depth of the OH line can be obtained from the intensity ratio between 1665 and 1667 MHz lines (assuming LTE). From this point of view we have compared the CO and OH observational results.