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arXiv 0907.3098astro-ph.IMastro-ph.HE
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无线电空气簇射阵LOPES的时间校准

Time Calibration of the Radio Air Shower Array LOPES

Frank G. Schröder

摘要:

LOPES是由30个校准偶极天线组成的数字读出天线阵列。它位于卡尔斯鲁厄研究中心的KASCADE-Grande实验场地,测量40至80兆赫频带内宇宙射线空气簇射的无线电发射。LOPES由KASCADE触发,并使用KASCADE重建的簇射轴作为分析无线电脉冲的输入。因此,当所有天线的信号被数字合并以形成进入簇射方向的波束时,LOPES作为干涉仪工作。为了对无线电信号的相干性敏感,需要精确到1 ns量级的精确时间校准。因此,有必要知道每个天线的延迟,这是时间和频率相关的。在分析中进行几次校准测量以纠正这种延迟:通过记录在已知时间发射的测试脉冲,定期测量每个天线的群延迟(大约每年一次)。此外,通过所谓的相位校准方法连续监测延迟:信标(偶极天线)连续发射63.5 MHz和68.1 MHz的两个正弦波。由此,可以在无线电事件的后续分析中将延迟的变化检测为这些频率处的相位的变化。最后,模拟电子器件的色散已被测量,以考虑延迟的频率依赖性。

英文摘要:

LOPES is a digitally read out antenna array consisting of 30 calibrated dipole antennas. It is located at the site of the KASCADE-Grande experiment at Forschungszentrum Karlsruhe and measures the radio emission of cosmic ray air showers in the frequency band from 40 to 80 MHz. LOPES is triggered by KASCADE and uses the KASCADE reconstruction of the shower axis as an input for the analysis of the radio pulses. Thereby LOPES works as an interferometer when the signal of all antennas is digitally merged to form a beam into the shower direction. To be sensitive to the coherence of the radio signal, a precise time calibration with an accuracy in the order of 1 ns is required. Thus, it is necessary to know the delay of each antenna which is time and frequency dependent. Several calibration measurements are performed to correct for this delay in the analysis: The group delay of every antenna is measured regularly (roughly once per year) by recording a test pulse which is emitted at a known time. Furthermore, the delay is monitored continuously by the so called phase calibration method: A beacon (a dipole antenna) emits continuously two sine waves at 63.5 MHz and 68.1 MHz. By that a variation of the delay can be detected in a subsequent analysis of the radio events as a change of the phase at these frequencies. Finally, the dispersion of the analog electronics has been measured to account for the frequency dependence of the delay.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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