太魯閣計劃新觸發系統的模擬與設計

Abstract

極高能宇宙射線是指能量高於 10^18 電子伏特的宇宙射線，物理學家們希望透過這一活躍的研究領域去探索如此高能量粒子的來源與它們的形成機制。臺灣天文粒子地磁同步輻射觀測站（Taiwan Astroparticle Radiowave Observatory for Geo-synchrotron Emissions，簡稱 TAROGE），坐落於臺灣東部沿海的高山上指向海洋，是一個致力於探測極高能宇宙射線誘發的廣延空氣簇射所產生的納秒級別的無線電波信號的天線陣列。在 2014-2015 期間，我們成功安裝了兩個觀測站作為無線電波環境測量與調節儀器參數的工具。 這兩個觀測站的觸發機制使用的是通過把一個整頻段分成四個子頻段要求它們同時觸發的多頻段復合探測技術。這能有效的提高對於脈衝地磁同步輻射信號與熱噪聲和人為連續波背景之間的分辨能力。 但是數據分析顯示人為連續波依然極大的限制了探測效率。這主要是因為 TAROGE 是坐落于郊區。我們應該繼續研發一個新的觸發機制專門去提高信號與連續波之間的分辨能力。 我們的方法是通過使用表面聲波濾波器把整個母頻段（110MHz 到 350MHz）分為 10 到 20 個子頻段。通過電腦模擬，我們找到了多頻段復合探測技術的最佳配置。模擬還表明了通過這一新配置，探測效率能得到有效的提高。實物觸發板正在調試階段。

Ultra-high energy cosmic rays (UHECRs) are cosmic rays with energies greater than 10^18 eV, it is a new and active research area where the sources and mechanics of such high energy particles are expected to be discovered. Taiwan Astroparticle Radiowave Observatory for Geo-synchrotron Emissions (TAROGE), sitting on high mountains of Taiwan east coast and pointing to the ocean, is an antenna array dedicated for detecting radio impulse of nanosecond duration from extensive air showers induced by UHECRs. Two stations had been installed successfully in 2014-15 for the purposes of radio survey and optimization of instrumental parameters. Multi-frequency bands coincidence technique by dividing the full-band into 4 sub-bands for trigger have been used in those two stations to provide an effective discriminating power for impulsive geo-synchrotron signals against thermal noises as well as CW anthropogenic backgrounds. However, analysis of data shows that detection efficiency is still highly restricted by the CW noises because TAROGE is sitting on suburban area. To overcome this problem, a new trigger is need to be designed, to further enhance the discriminating power between signals and CW especially. Our method is dividing the full-band (110 MHz – 350 MHz) to 10-20 subbands by using SAW filters. A trigger simulation has been set up to investigate the optimum configuration of this novel technique. Simulation study shows improvement in trigger efficiency as new trigger configuration been implemented. And the real trigger board is under testing.