Radioisotope dating with the LBL 88'' cyclotron

Since July 1976, a group at the Lawrence Berkeley Laboratory has been studying and developing the potential of the 88'' cyclotron for radioisotope detection and dating. This cyclotron is much larger and more powerful than required for dating, but its flexibility and ability to tune rapidly to accelerate almost any isotope has enabled the study of several different applications. The sensitivity of using the cyclotron for the detection at natural concentrations of tritium, beryllium-10, carbon-14, and chlorine-36, was demonstrated. The key feature that allows direct detection of low-level radionuclides is the high energy of the emerging beam, which allows particle-identification techniques to be used on an atom-by-atom basis. Without such particle identification, direct counting is impossible since unstripped background ions with the same charge-to-mass ratio always appear in the beam. A simple gas cell which completely stops the nitrogen beam while allowing the carbon-14 atoms to pass was built and used