| 151Sm (T1/2=90a) is a long-lived fission product. The concentration measurement of 151Sm is very significant in environment science, life science, etc. Detection of 151Sm byβorγray measurement is unfeasible due to its overall low activity. Accelerator Mass Spectrometry (AMS) may be the method of choice to measure ultra-trace 151Sm with sufficient sensitivity.The present work is for the first time to study the AMS measurement of 151Sm, and to use 151Sm as tracer for clarifying whether the rare earth elements can enter into the brain.The main contributions of the author in this study include: 1) Preparation of calibration samples, blank samples and biological samples. Among the procedures established are the measurement method of isotopic ratios 151Sm/150Sm with the Thermal Ionization Mass Spectrometry (TIMS), the chemical separation of Eu by pressured cation exchange chromatography, and the measurement of residual Eu by ICP-MS. 2) The resolution of ionizer poisoning and the optimization of chemical form of target samples for AMS measurement of 151Sm. 3) The development of 151Sm tracer -AMS method for the study on REE metabolism in brain. 4) The measurement of sensitivity for 151Sm by AMS using blank sample, and the AMS measurement of calibration samples.The preparation of sample is the key to AMS measurement. 151Sm was produced via neutron capture of 150Sm by the irradiation of Sm2O3 with 150Sm enriched to 87.27%, with the neutron flux of 5.16×1013s-1·cm-2 in the heavy water research reactor at CIAE for eighteen days. The sample after irradiation was dissolved with nitric acid. The 151Sm/150Sm in the irradiated sample was measured by TIMS to be (3.750±0.002)×10-3. Standards with 151Sm/154Sm ratios of (9.25±0.08)×10-7, (8.87±0.08)×10-8, (8.08±0.08)×10-9 were prepared by series dilution of the irradiated sample with the enriched 154Sm. A set of facilities was designed for the separation of Sm and Eu withα-HIBA-cation exchange chromatogramphy technique. And the Eu in all samples were separated with this method. The recovery of Sm is about 60%, and the decontamination facot is 250 or so.Sm is a lanthanide element, it can deteriorate the ionization efficiency of the ionizer because of its low vapor pressure and low work function. This phenomenon is called the ionizer poisoning, which causes the beam current decreasing rapidly. The problem was resolved by using tungsten cathode, mixing samples with tungsten or molybdenum powder, etc. Stable operation of the ion source was successfully achieved with a samarium (Sm) oxide beam current of 100nA.The main interference for detection of 151Sm is stable isobar 151Eu. 151Eu can not be separated from 151Sm in the detector. But 151Eu can be suppressed by using Sm2O3 as sample material and extracting SmO- from the ion source. In order to further suppress 151Eu, theα-HIBA-cation exchange chromatography technique was used to separate Eu in samples. 151Eu can be further reduced by adding enriched 153Eu into the sample separated, and repeating the separation procedure. In addition, the 153Eu/154Sm and 151Eu/153Eu need to be measured to subtract the 151Eu contribution from the counts of 151Sm+151Eu. The more accurate 151Sm/154Sm can be obtained by the bfore mentioned treatment.The blank sample and a series of calibration standard samples were measured with AMS. The pilot beam for 151Sm AMS measurement is 151SmO-. The sputter and ionization yield for SmO- was about 6×10-4 in the ion source. The transmission efficiency from the low energy Faraday cup to the AMS cup was 4.4×10-3. The isotopic ratio 151Eu/151Eu in blank sample is (4.8±1.4)×10-8, so the sensitivity of 151Sm AMSmeasurement is about 1×10-8 .151Sm is a rare earth elements (REE). They have come into extensive use rapidly in a number of fields. The impact of REE on environment and human health has become a major concern. So far whether the rare earth elements can penetrate the blood-brain barrier (BBB) into the brain is still in controversy. In this work, 151Sm was used as tracer in an effort to clarify this problem.The Wistar rats were intravenously injected with the solution of 151Sm. The animals were anesthetized with chloral hydrate at 24, 48, 96, 144 and 288h after the injection, respectively. The brain, blood and liver samples were collected. The biological samples need to be prepared to extract 151Sm in the form of Sm2O3 with enriched 154Sm as carrier for AMS measurement. The brain and blood samples were measured with AMS. The isotopic ratio of 151Eu/154Sm is (5.4±1.5)×10-8 in the blank sample of brain. And the concentration of 151Sm in 12d brain samples is (7.8±2.2)×10-10g/g after isobaric interference corrections. The isotopic ratio of 151Eu/154Sm in the blank sample of blood (separated) and the blank sample of blood (not separated) is (5.4±1.5)×10-8 and (3.2±0.9)×10-7 respectively. And the concentration of 151Sm in 1h blood (separated) and 1h blood (not separated) samples are (9.0±2.6)×10-9g/g and (1.4±0.4)×10-8g/g after isobaric interference corrections.A new method is being developed for AMS measurement of 151Sm. It is the first measurement of 151Sm with AMS in the world. The method was used in life science, and some biological samples were measured with AMS.
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