Application of the nitrogen laser calibration system in LAASO-WFCTA

Discussion timeslot (ZOOM-Meeting): 21. July 2021 - 12:00
ZOOM-Meeting URL: https://desy.zoom.us/j/92210078166
ZOOM-Meeting ID: 92210078166
ZOOM-Meeting Passcode: ICRC2021
Corresponding Session: https://icrc2021-venue.desy.de/channel/13-New-Instrumentation-and-Tools-for-EAS-Detection-CRI/92
Live-Stream URL: https://icrc2021-venue.desy.de/livestream/Discussion-03/4

Abstract:
"The nitrogen laser calibration system for the Wide Field of View Cherenkov Telescope Array (WFCTA) is one of the most important components of the Large High Altitude Air Shower Observatory (LHAASO). This calibration system is composed of three parts, including a high-precision 3D lifting and rotating platform (HiRoP), a nitrogen laser and the wide field of view Cherenkov telescope prototypes. The accuracy of the HiRoP is of great importance for the precise calibration of WFCTA since it controls the laser beam’s pointing direction. A home-made HiRoP was then introduced and the measurements showed the angular and lifting accuracies of HiRoP were better than 0.004° and 0.075 mm, respectively. In addition, the corresponding repeatabilities of HiRoP were better than 0.003° and 0.025 mm, respectively. Furthermore, the pulse energy stability of the nitrogen laser beam is another remarkably important factor. The nitrogen laser system with a wavelength of 337.1 nm located in a high-precision temperature and humidity's controlling container, resulting in a pulse energy fluctuation less than 3 percent. Besides, the method of a standard zero verification was employed to improve the long-term accuracy of the beam pointing direction. Finally, we obtained the repeatability of 0.049° for the focal imagines on the camera in the WFCT after a 15-day’s statistical measurements. These results indicate that our calibration system meets the requirements of the LHASSO for a long-term observation."

Authors: Long Chen
Co-Authors: Xin Li | Lisi Ge | Hu Li | Qinning Sun | Wang Yang | Junji Xia | Fengrong Zhu | Yong Zhang 
Indico-ID: 1275
Proceeding URL: https://pos.sissa.it/395/269