36Cl-AMS measurements with 3-MV tandem accelerator

Cl-36 is one of the most interesting nuclides in accelerator mass spectrometry (AMS) measurements. The application of Cl-36 has been widely applied in various fields. All most all of Cl-36 AMS measurements at natural isotopic concentrations have yet been performed at tandem accelerator with 5 MV or higher terminal voltage. The measure improvement of Cl-36 and other medium heavy isotopes performed at 3 MV in AMS facilities is one of the hottest topics in AMS measurements. In order to increase the suppression factor of S-36, the energy loss straggling and angular straggling of Cl-36 and S-36 ions in various counter gases (P10, isobutane and propane) were investigated. Some groundwater samples were measured with energy of 32 MeV, and the results were in good agreement with the result obtained with ion energy of 72 MeV. The results indicate that the approximate detection limit of Cl-36 in 3 MV AMS facility is Cl-36/Cl=1x10(-14), and the uncertainty is 30% when the sample with isotopic ration Cl-36/Cl approximate to 10(-13).