Absolute energy calibration of the Telescope Array fluorescence detector with an Electron Linear Accelerator

Abstract

The measurement of primary energy and spectrum is one of the most important themes for the experiments of Ultra-High Energy Cosmic Rays (UHECRs). The Electron Light Source (ELS) is an electron linear accelerator, which was installed 100m in front of the Fluorescence Detector (FD) of Telescope Array (TA) experiment operating in the field of Utah, USA for the observation of UHECRs. A beam of 40MeV electrons is vertically injected into the air from the ELS and generated Air Fluorescence (AF) photons are detected by the TA/FD telescope. A direct calibration of the TA/FD is achieved by comparing the measured ELS signal with the predicted signal by simulation using a model of AF generation. In this report, we present the status of ELS operation and the first result of calibration.