TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan)
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
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Volume 49, Issue 8
Displaying 1-6 of 6 articles from this issue
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Preface
Feature: Superconducting Electronics (Part 2)
Focused Reviews
  • Frequency-domain Readout for Transition Edge Sensor Bolometers for the POLARBEAR-2 Cosmic Microwave Background Experiment
    Kaori HATTORI
    2014 Volume 49 Issue 8 Pages 417-424
    Published: August 25, 2014
    Released on J-STAGE: September 29, 2014
    DOIhttps://doi.org/10.2221/jcsj.49.417
    JOURNAL FREE ACCESS
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    Transition edge sensors (TES) have achieved a low noise level and become an attractive tool for detecting photons and measuring the power of millimeter waves. While large TES arrays are awaited in many fields, multiplexing schemes limit the multiplexing factor and the number of detectors. In the case of frequency-domain multiplexing, extending the multiplexing factor requires an increase in the bandwidth of the SQUID electronics. To overcome this limitation, we use digital active nulling (DAN) on a digital frequency multiplexing platform. We present development of the large array's readout for the POLARBEAR-2 cosmic microwave background (CMB) experiment. It aims to observe B-mode polarization generated by the gravitational lensing of CMB and inflationary gravitational waves, with high sensitivity. We will build a receiver that has 7,588 TES bolometers coupled to polarization-sensitive antennas. We present implementation of DAN and show that our system is able to bias a bolometer in its superconducting transition at approximately 3 MHz.
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  • Superconducting Nanowire Single-photon Detector
    Toward Wide-range Application of the Single-photon Detection Technique
    Taro YAMASHITA, Shigehito MIKI, Zhen WANG, Hirotaka TERAI
    2014 Volume 49 Issue 8 Pages 425-432
    Published: August 25, 2014
    Released on J-STAGE: September 29, 2014
    DOIhttps://doi.org/10.2221/jcsj.49.425
    JOURNAL FREE ACCESS
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    We present our recent progress in development of a superconducting nanowire single-photon detector (SSPD) system. Our practical SSPD system with a compactGifford-McMahon cryocooler successfully achieved the high system detection efficiency of 74%, low dark count of 100 cps, and small timing jitter of 68 ps in one device simultaneously, which is useful for actual applications. Furthermore, we propose and demonstrate a new strategy to resolve a trade-off problem between the system detection efficiency and counting rate (speed) in the SSPD.
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Originals
  • Fabrication of 3 THz Quasi-Optical NbN Hot Electron Bolometer Mixers
    Akira KAWAKAMI, Yoshihisa IRIMAJIRI, Shukichi TANAKA, Satoshi OCHIAI, ...
    2014 Volume 49 Issue 8 Pages 433-438
    Published: August 25, 2014
    Released on J-STAGE: September 29, 2014
    DOIhttps://doi.org/10.2221/jcsj.49.433
    JOURNAL FREE ACCESS
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    Hot electron bolometer mixers (HEBM) are expected to be used as low-noise heterodyne mixers in the terahertz frequency range. We are developing quasi-optical HEBMs for applications such as atmospheric remote sensing and radio astronomy in the terahertz frequency range. Therefore, we developed a fabrication method using niobium nitride (NbN) ultrathin films deposited on a silicone (Si) substrate for terahertz applications. First, a magnesium oxide buffer layer 50 nm thick was deposited on a Si substrate at approximately 525 °C. After deposition of this layer, NbN ultrathin films were deposited at ambient temperature. Using the buffer layers, we found the transition temperature of the 3.5-nm-thick NbN thin films to be approximately 10 K. The same method was applied to fabricate NbN-HEBMs on a Si substrate. The fabricated quasi-optical mixers were designed to operate at 3.1 THz. The receiver noise temperature was found to be approximately 1930 K (DSB) at 3.1 THz.
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  • Mobile HTS-SQUID Magnetometer in an Unshielded Environment
    – Application to a Robot-based Non-destructive Evaluation System –
    Yoshimi HATSUKADE, Keisuke YOSHIDA, Takahiro KAGE, Takefumi SUZUKI, Sa ...
    2014 Volume 49 Issue 8 Pages 439-445
    Published: August 25, 2014
    Released on J-STAGE: September 29, 2014
    DOIhttps://doi.org/10.2221/jcsj.49.439
    JOURNAL FREE ACCESS
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    Here, we developed a robust HTS-SQUID magnetometer based on a bicrystal SrTiO3 substrate and single-layer YBa2Cu3O7-x film, aiming for a mobile magnetometer in an unshielded environment. The robustness in the unshielded environment was achieved by coverage of the SQUID magnetometer with another HTS cross-shaped film in a flip-chip configuration, and introduction of a mesh structure in both the magnetometer and the HTS film. The SQUID parameters in DC and AC fields, such as critical current 2Ic, resistance Rn/2, modulation depth Vpp and flux noise S∅1/2, were studied. The SQUID was rotated and moved in the environment using a robot-arm, resulting in stable operation during the motion at 20 mm/s with active magnetic shielding.
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