1. Introduction

The quest for dark matter is one of the most pressing challenges to cosmology and astro-particle physics. Its direct detection with earthbound detectors will provide decisive explanations of its true nature. Since its discovery by the Swiss astronomer Fritz Zwicky in 1933 [1] a lot more has been learned, mostly in recent years, about this ubiquitous matter, which gravitationally binds stars in galaxies [2], galaxies in clusters and in large-scale structures [3]. From a number of astrophysical observations and from the cosmic microwave background radiation experiment WMAP [4], we have learned that the universe contains about 30% matter and 70% dark energy. Most of this matter is invisible and of exotic nature. In case the dark matter consists of exotic particles which interact weakly with ordinary matter, so-called weakly interacting massive particles (WIMPs), they should be detectable in principle. A recent review on direct dark matter searches can be found in Ref. [5] and references therein.

A prototype liquid Argon Time Projection Chamber for the study of UV laser multi-photonic ionization

ABSTRACT: This paper describes the design, realization and operation of a prototype liquid Argon Time Projection Chamber (LAr TPC) detector dedicated to the development of a novel online monitoring and calibration system exploiting UV laser beams. In particular, the system is intended to measure the lifetime of the primary ionization in LAr, in turn related to the LAr purity level. This technique could be exploited by present and next generation large mass LAr TPCs for which monitoring of the performance and calibration plays an important role. Results from the first measurements are presented together with some considerations and outlook.