Microwave Kinetic Inductance Detectors for Long Duration Balloon experiments .

Long Duration Balloon experiments have played a key role in the study of the Cosmic Microwave Background. The measurement of its temperature anisotropies has been the first step towards a deeper understanding of the structure of the Universe. Yet to date many questions regarding its birth and evolution remain open. The polarization signal of the CMB can help us answer most of them. In particular, the so called B modes would be a direct test of the Inflation and could give information on the scale of energies at which it took place. The amplitude of the B modes is expected to be less then 1mu K. In order to measure this kind of signal one needs either a very long integration time, or a very fast mapping speed. In the case of LDB and satellite missions the second is the only viable solution. This poses a serious technological challenge as large arrays of detectors are usually very hard to implement. In this paper we present the working principle of the Microwave Kinetic Inductance Detectors and their status of development in Italy, focusing on the key aspects that make them ideal for application in LDBs experiments and in particular for a high purity, ultra-sensitive, polarization mapper.