Today, I will tell you a little bit of the measurement of I-129, since this is my day of preparing the separated samples for analysis. This is a very exciting thing but unfortunately I cannot do the measurements here in Denmark. Because of the very low concentrations the I-129 has to be measured with a technique called accelerator mass spectrometry (AMS). These instruments are very big (see picture) and expensive (about 1-5 million Euros). One of such instruments exists in my hometown, Xi’an in China so we send the samples there so they can analyze them.

The samples are measured with AMS for 129I.

Fig 5. Accelerator mass spectrometry (AMS) at Xi’an AMS center, China

Often we prepare the samples by pressing the iodine as AgI (silver iodide) into small copper capsules. These capsules are then mounted in a carousel in the machine and a cesium ion beam is sputtering on the sample to release its content. The ions produced are led into the a series of magnets and lenses that finally lets the ions hit a detector and the amount of I-129 can be determined. The same instrument and technique is used for a number of isotopes, the most well known is Carbon-14.