Ultra low noise current sources

CRESST operates detectors placed at 10mK. These sensors interact with energetic elementary particles and deliver a signals which can be related to the type of particles and the nature of the interactions. The reason for operating sensors at low temperature is the reduction in thermal noise, which is proportional to the square root of the absolute temperature. By 2020 CRESST collaboration expects to have installed 5 time more detectors than in the current setup. To operate the detectors a fully new readout system is required. At HEPHY we are designing and building a system of one thousand ultra-low noise current sources that will operate the cryogenic detectors in the next years. To keep CRESST leading role in the search for Dark Matter our challenge is to integrate such an amount of current sources by keeping the noise level below a few pA/sqrt(Hz) and to develop an automated way to characterize the sensors, task that currently is done manually. To facilitates further upgrades our system holds the current sources in boards of few 50x50 mm2 that are plugged to a backplane. Following our design specification, this gives the opportunity to test any day new designs with new components in the real experiment without stopping the data taking.