Alpha decay has historically given insight into the inner workings of the nucleus as the decay rate is strongly affected by nuclear structure. Very long lived alpha decaying isotopes (about T1/2 = 108-10 a) can be used as a powerful tool to date the formation of astronomical objects in the Solar System due to their extremely long half lives. This technique is however very vulnerable to the accuracy of the half-life. This means that improved half-live measurements are important though they pose a significant technical obstacle.
To measure the half-lives of such long lived isotopes besides appropriate targets special care needs to be taken with background and signal efficiency. To overcome these obstacles the design of the twin Frisch-Grid ionisation chamber was chosen . This design combines excellent energy resolution with a hight detector efficiency to measure decay rates in the region of a few counts per day. It is also possible to use pulse shape analysis to obtain position information on each event, allowing for improved signal to background discrimination.
This presentation will give an overview of the detection aspects of the twin Frisch-Grid ionisation chamber, as well as the calibrations that were performed. New measurements of the half-lives of 147Sm and 190Pt will also be presented and discussed here.
 A. Hartmann et al., NIM A 814, 12 (2016).