دانلود رایگان مقاله تراز آینه بوکه تلسکوپ چرنکوف

ABSTRACT

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment remains a challenge. Here we present a simple, yet extendable method, to align a segmented reflector using its Bokeh. Bokeh alig nment does not need a star or good weather nights but can be done even during daytime. Bokeh alignment optimizes the facet orientations by comparing the segmented reflectors Bokeh to a predefined template. The optimal Bokeh template is highly constricted by the reflector’s aperture and is easy accessible. The Bokeh is observed using the out of focus image of a near by point like light source in a distance of about 10 focal lengths. We introduce Bokeh alignment on segmented reflectors and demonstrate it on the First Geiger-mode Avalanche Cherenkov Telescope (FACT) on La Palma, Spain.

7. Conclusion

In a first demonstration we aligned the FACT IACT using Bokeh alignment in a single day and a single iteration from an useless state, after a reflector reconfiguration, to an operational state for γ ray astronomy. Bokeh alignment is inexpensive, fast and more versatile than current methods for the alignment of a segmented reflector. Boke alignment is simple, and does not need a lot of custom hardware or software. Yet it gives information about individual mirror facet surfaces and does neither need star light nor dark nights to align a segmented reflector. Boke alignment could even be done during the day. Therefore, we believe that Bokeh alignment is ideal to align a large number of Cherenkov telescopes, for instance the upcoming Cherenkov Telescope Array (CTA).