32Si

the only long-life(~140 a) radioisotope of silicon

plays a unique role in geochronometry in the range of 100-1000 years

and in research of the global biogeochemical silica cycle.Because of its ultra high sensitivity

minute sample amount and short measurement time

the accelerator mass spectrometry(AMS) is the most proper method for detecting 32Si.China Institute of Atomic Energy has been making efforts in establishing the ultra-sensitive method of 32Si determination via AMS.31P and 30Si targets are irradiated in a swimming pool reactor to produce 32Si.Chemical procedures to extract the 32Si from the irradiated targets have been decided

along with electric conductor materials and the mixing ratio

the negative ion formation method

and processes to dilute the solutions to form high 32Si abundance samples.After several tests and improvements of the experimental conditionals

we were able to measure the sample at the abundance of 10-13 in a sensitivity of better than 1.5×10-14.In this paper

we report our progresses in establishing the AMS-based ΔE-Q3D method for 32Si determination.