5:15 PM - 7:15 PM
[PEM14-P07] Development of a mechanical cooled cold-load for calibration of mm-wave spectral intensity and plan to resume the observation in Tromsø
Keywords:Atmospheric minor constituents, Millimeter wave spectroscopy, Polar region, Ground based observation
It is well known that the energetic particles that precipitate on the polar regions due to solar activity ionize atmospheric molecules and produce ozone-destroying molecules such as NOx and HOx.
We are planning to distinguish the effects of seasonal changes and those of energetic particles through simultaneous ground-based millimeter-wave spectroscopic observations from both southern polar region, Syowa Station and northern polar region, Tromsø. Due to COVID19 pandemic, the operation at Tromsø has unfortunately been suspended since February 2020, but we checked the instruments and started test observation in January 2025 aiming to full operations.
Millimeter-wave molecular spectroscopy requires the use of blackbody radiation at two different temperatures as a reference for intensity calibration. A blackbody in liquid nitrogen is currently using as the cold one both at Syowa and Tromsø. However, at Tromsø, frost growing on the glass dewar is blocking the line of sight of the radio beam, making long-term unattended automated observations difficult. To solve this problem, we are developing a frost-free cooled blackbody in a vacuum cryostat by using a closed-cycle He refrigerator.
The blackbody is TK-RAM made by Thomas Keating Ltd; a radio absorber commonly used in submillimeter wave. Since TK-RAM is made of polypropylene, which has low thermal conductivity, an important development point is to maintain a stable low radiation temperature against external radiation heat inflow (Saito, Master thesis, Nagoya University, 2022). Basic experiments are underway in the laboratory to improve the cooling efficiency by fixing the TK-RAM to an oxygen-free copper plate by bolting it and cooling it from the inside. At present, the stage of the refrigerator is 29 K, the physical temperature of the TK-RAM blackbody is 86 K, and the equivalent radiation temperature calculated from the radio wave intensity is 116 K which is within the range for use as a cooled blackbody, but we will put it to practical use after further improvement the temperature and stability against internal heat flow from the superconducting receiver block and radiative heat inflow from the outside.
In the presentation, we will introduce not only the development of the mechanically cooled blackbody, but also the current status of the observation system in Tromsø including the plan for resume the operation and replacement with a multi-frequency millimeter spectrometer.
We are planning to distinguish the effects of seasonal changes and those of energetic particles through simultaneous ground-based millimeter-wave spectroscopic observations from both southern polar region, Syowa Station and northern polar region, Tromsø. Due to COVID19 pandemic, the operation at Tromsø has unfortunately been suspended since February 2020, but we checked the instruments and started test observation in January 2025 aiming to full operations.
Millimeter-wave molecular spectroscopy requires the use of blackbody radiation at two different temperatures as a reference for intensity calibration. A blackbody in liquid nitrogen is currently using as the cold one both at Syowa and Tromsø. However, at Tromsø, frost growing on the glass dewar is blocking the line of sight of the radio beam, making long-term unattended automated observations difficult. To solve this problem, we are developing a frost-free cooled blackbody in a vacuum cryostat by using a closed-cycle He refrigerator.
The blackbody is TK-RAM made by Thomas Keating Ltd; a radio absorber commonly used in submillimeter wave. Since TK-RAM is made of polypropylene, which has low thermal conductivity, an important development point is to maintain a stable low radiation temperature against external radiation heat inflow (Saito, Master thesis, Nagoya University, 2022). Basic experiments are underway in the laboratory to improve the cooling efficiency by fixing the TK-RAM to an oxygen-free copper plate by bolting it and cooling it from the inside. At present, the stage of the refrigerator is 29 K, the physical temperature of the TK-RAM blackbody is 86 K, and the equivalent radiation temperature calculated from the radio wave intensity is 116 K which is within the range for use as a cooled blackbody, but we will put it to practical use after further improvement the temperature and stability against internal heat flow from the superconducting receiver block and radiative heat inflow from the outside.
In the presentation, we will introduce not only the development of the mechanically cooled blackbody, but also the current status of the observation system in Tromsø including the plan for resume the operation and replacement with a multi-frequency millimeter spectrometer.