Regresar

A calibration study of local ice and optical sensor properties in IceCube

Abstract:

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector installed in the ice at the geographic South Pole [1] instrumenting depths between 1450m and 2450m. It detects Cherenkov radiation emitted by secondary particles produced in neutrino interactions in the surrounding ice or the nearby bedrock. The optical properties of ice surrounding the detector have been studied in detail, and the latest results are presented at this conference [2]. This paper focuses on the properties of ice in the immediate vicinity of the optical sensors (digital optical module, or DOM), and on the relative position and orientation of the DOMs within this local ice. Each of the 5160 DOMs deployed in ice is equipped with 12 light emitting diodes (LEDs) that are positioned on a daughter" flasher" board and can emit light one at a time or in simultaneous combinations. The LEDs are placed in pairs (1 and 7, 2 and 8, and so on) at 60-degree increments in azimuth. LEDs 1-6 emit light at an angle of 48 degrees up, and LEDs 7-12 point straight out horizontally. Most of the instrumented LEDs emit light centered at 405 nm wavelength in a cone of about 9.7 degree width (RMS). Initial all-purpose calibration sets (taken mainly to study the optical properties of ice) used configuration in which all 6 horizontal LEDs were emitting light simultaneously, creating an approximately azimuthally-symmetric pattern of light. This light was observed by the DOMs on the surrounding strings and the resulting data sets were used to fit the properties of interstring ice. Because of the abundance of data (high number of emitter-receiver pairs) the simple hypothesis of cylindrically-symmetric …