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Title: Radio-transparent multi-layer insulation for radiowave receivers

In the field of radiowave detection, enlarging the receiver aperture to enhance the amount of light detected is essential for greater scientific achievements. One challenge in using radio transmittable apertures is keeping the detectors cool. This is because transparency to thermal radiation above the radio frequency range increases the thermal load. In shielding from thermal radiation, a general strategy is to install thermal filters in the light path between aperture and detectors. However, there is difficulty in fabricating metal mesh filters of large diameters. It is also difficult to maintain large diameter absorptive-type filters in cold because of their limited thermal conductance. A technology that maintains cold conditions while allowing larger apertures has been long-awaited. We propose radio-transparent multi-layer insulation (RT-MLI) composed from a set of stacked insulating layers. The insulator is transparent to radio frequencies, but not transparent to infrared radiation. The basic idea for cooling is similar to conventional multi-layer insulation. It leads to a reduction in thermal radiation while maintaining a uniform surface temperature. The advantage of this technique over other filter types is that no thermal links are required. As insulator material, we used foamed polystyrene; its low index of refraction makes an anti-reflection coating unnecessary.more » We measured the basic performance of RT-MLI to confirm that thermal loads are lowered with more layers. We also confirmed that our RT-MLI has high transmittance to radiowaves, but blocks infrared radiation. For example, RT-MLI with 12 layers has a transmittance greater than 95% (lower than 1%) below 200 GHz (above 4 THz). We demonstrated its effects in a system with absorptive-type filters, where aperture diameters were 200 mm. Low temperatures were successfully maintained for the filters. We conclude that this technology significantly enhances the cooling of radiowave receivers, and is particularly suitable for large-aperture systems. This technology is expected to be applicable to various fields, including radio astronomy, geo-environmental assessment, and radar systems.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [5] ;  [2] ;  [6]
  1. Korea University, Anam-dong Seongbuk-gu, Seoul 136-713 (Korea, Republic of)
  2. Department of Particle and Nuclear Physics, School of High Energy Accelerator Science, The Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa 240-0193 (Japan)
  3. Terahertz Sensing and Imaging Team, Terahertz-wave Research Group, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)
  4. Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan)
  5. (Japan)
  6. (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan)
Publication Date:
OSTI Identifier:
22251536
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 84; Journal Issue: 11; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; APERTURES; ASTRONOMY; FILTERS; GHZ RANGE 100-1000; INFRARED RADIATION; OPACITY; POLYSTYRENE; RADAR; RADIOWAVE RADIATION; REFLECTION; REFRACTIVE INDEX; SHIELDING; THERMAL RADIATION; VISIBLE RADIATION