The isomer ^ { 83 m } Kr with its half-life of 1.83 h is an ideal calibration source for a liquid noble gas dark matter experiment like the XENON project .
However , the risk of contamination of the detector with traces of the much longer lived mother isotop ^ { 83 } Rb ( \mbox { $T _ { 1 / 2 } $ } = 86.2 d ) has to be ruled out .
In this work the release of ^ { 83 } Rb atoms from a 1.8 MBq ^ { 83 } Rb source embedded in zeolite beads has been investigated .
To do so , a cryogenic trap has been connected to the source for about 10 days , after which it was removed and probed for the strongest ^ { 83 } Rb \gamma -rays with an ultra-sensitive Germanium detector .
No signal has been found .
The corresponding upper limit on the released ^ { 83 } Rb activity means that the investigated type of source can be used in the XENON project and similar low-background experiments as ^ { 83 m } Kr generator without a significant risk of contaminating the detector .
The measurements also allow to set upper limits on the possible release of the isotopes ^ { 84 } Rb and ^ { 86 } Rb , traces of which were created alongside the production of ^ { 83 } Rb at the Rez cyclotron .