Bragg Curve Detector And Its Application In AMS Mearsurements For Medium-Weight Nuclides

Because of interference of isobars, the sensitivity is restricted in AMS measurement for medium-weight nuclides. The key point for a high-resolution and high-accuracy measurement in the AMS technology is how to effectively identify isobars. Measurement of medium-weight nuclides by AMS needs a high-performance detector which can effectively identify isobars to improve the sensitiveness.The schematic layout and principle of a Bragg Curve Detector were showed in this paper. A Bragg Curve Detector was systemically modified and its performance was improved. Its best working condition was tested and performance was reported. The resolution of the detector was 0.9% for alpha particles at 5.48MeV from a ²⁴¹Am source. The Bragg Peak signal resolution was 1.6%. These results were obtained at the following conditions: (1) the pressure was selected to make incident particle stopping near before the grid mesh; (2) the electric reduced fields for cathode-grid and grid-anode were 0.26V/cm·Torr and 1.94V/cm·Torr in P10 gas, respectively. Compared with same type detectors used elsewhere in world, this detector had a higher performance and could be used to measure medium-weight nuclides in AMS.After these tests, some applications based on the Bragg Curve Detector were carried out. This detector was used to identify medium-weight isobars in AMS measurements at CIAE. A series of ³⁶Cl, ⁴¹Ca and ⁷⁹Se standard samples were measured. This detector could clearly identify ³⁶Cl-³⁶S and ⁴¹Ca-⁴¹K. The results showed that the Bragg Curve Detector could be successfully used for AMS measurement.In the measurement of nuclides with Z near 16,ΔZ/Z of 1/47 could be achieved, corresponding to a Bragg Peak resolution of 2.1%. Compared with the ΔE-E detectors, this Bragg Curve Detector had a higher charge identification capability, and could directly give the Z value within 1.2% uncertainty according to the relationship between Bragg Peak and atomic number of nuclide. By using the waveform recognition technique, the performances of Bragg Curve Detectors could be further improved in terms of charge identification, especially for medium-weight nuclides measurements by AMS.