DETECTION OF SINGLE X-RAY QUANTA WITH A MAGNETIC CALORIMETER

We give a status report on the development of a particular low tempera ture calorimeter with new experimental results. On absorption of an X- ray photon the increase of temperature changes the magnetization of a diluted magnetic sample, and this quantity is measured with a SQUID-ma gnetometer. It is a special feature of this experimental method that t he magnetic sample has a very high heat capacity and an additional abs orber for a compound detector does not change the sensitivity essentia lly. Besides a short summary on earlier measurements we present new re sults with metallic magnetic samples, which give shorter signal rise t imes (below 100 mu s). On a compound detector with 0.1 g of LaB6:Er an d an absorber of 12 g sapphire, the energy resolution for 5.9 keV and 60 keV X-ray sis 1.6 keV and 2.6 keV (FWHM), respectively. With a sili con absorber an energy resolution of 1.4 keV at 5.9 keV has been found . The energy resolution is in any case limited by two effects. On the one hand the signal height is strongly reduced due to an additional he at capacity of the magnetic sample and on the other had we have an add itional noise from the conduction elections of the metallic sample. Po ssible improvements with respect to both effects are discussed.