Horizontal polarization

Vertical Polarization

Noise from Kobe city

Development of microwave telescopes for detection of Molecular Bremsstrahlung Radiation from EAS of UHECR

T.YAMAMOTO1 H.AKIMUNE1 T.IIJIMA1 K KURAMOTO2 T FUJI2 S.OGIO2 N.SAKURAI2 H.SAGAWA3 M.FUKUSHIMA3

　　　　　　　　 1.Konan University,Kobe,Hyogo 658-8501 Japan　　　　　　　　　　 2.Osaka City University,Osaka 558-8585,Japan　　　　　　　　　　 3.Institute for Cosmic Research,University of Tokyo,Chiba 227-8582,Japan

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Multi-antenna microwave telescope system is under a development for a detection of Molecular Bremsstrahlung Radiation (MBR) from Extensive Air Showers. This system is composed of 12 parabolas fixed on a roof of Konan university in Kobe Japan. Diameter of the parabola is equivalent to 1.2 m. Each parabola has a single feed horn with 12GHz receiver on the focal point.

Fukushima Daiichi Nuclear Power Plant

Kobe City Konan University

Observation of UHECR through Microwave emission has been proposed in [P. Gorham et. Al., Phys. Rev. D, 2008, 78: 032007].The Microwave is expected from low energy electrons in the Extensive Air Showers through Molecular Bremsstrahlung Radiation. The low energy electrons are created in ionization of Atmospheric molecular and scattered isotropically. Therefore the Microwave emission is expected to be omni-direction just like ultra-violet light of Fluorescence emission.

Parabolic antenna for commercial satellite TV can be used to detect the Microwave emission from airshowers. Motivated from this idea, we are developing a multi-antenna observation system in Konan University which is located on Kobe City in Japan. Above picture shows the parabola antenna on a roof of a University building (135°15’E , 34”43’N, 106m above sea level).

Nippon Antenna CS-120K is used. This antenna is off axis parabolic antenna for satellite TV. The radius is equivalent to1.2 m. Anntena gain is about 42 dB. Amount of 12 antennas has been fixed on concrete pads of 1 ton weight as shown above picture. All parabola will be directed to south where Kobe bay and the Pacific Ocean are sweeping away.

UHECR

Extensive AirShower

MBR Microwave

free electrons

Above figure shows expected signal of Microwave from 12.25 to 12.75 GHz on the focal point of the 1.2 m parabola as a function of distance from the airshower to the antenna. The energies of the UHECRs are assumed to be 10 to 16 eV (opened circle) and 10 to 17 eV (closed circle). This simulation is based on the results from electron beam measurement by [P. Gorham et. Al., Phys. Rev. D, 2008, 78: 032007].5 Sigma detection level is also indicated in the graph under an assumption of 150K of System temperature of the data acquisition system. As shown in this figure, 0.1EeV airshower should be observed by this system.

The signal on the focal point of each parabola is received by a single receiver (Nippon Antenna FOC-ASJ5). This receiver measures two direction of polarization (horizontal and vertical) and convert the signal to around 1 GHz . The 1 GHz signal is transmitted through 5 m coaxial cable to a box located near the antenna. Electric power is supplied by a bias-T (Stack Electronics PD264) which includes impedance adapter. Then the signal intensity is measured through Power Detector (Mini-Circuits ZX47-60) and FADC of VEM module.

This figure shows an example of data measured by the parabola system. Noise level is about 1.05~1.1V which is corresponds to about 18dBm. A signal is detected in this figure which is caused by an artificial noise from Kobe city. The pulse height in vertical polarization is about 0.95V from noise level. This signal corresponds to 10 to -12 W on the focal point which is 6 order of magnitudes higher than the expected signal intensity in above simulation. We are now working to reduce noise on the system.