Madis Kiisk

Detection of 59Ni at the Lund AMS facility

Abstract In the use of small tandem accelerators for accelerator mass spectrometry (AMS), interfering isobars are often troublesome, especially when heavier isotopes such as 59Ni are to be measured. One way to reduce this problem is to combine AMS with the detection of characteristic projectile X-rays. After analysis in the AMS system, the ions are stopped in a suitable target and it is possible to identify the ions by atomic number and thereby separate the isobars. In order to lower the detection limit in the case of 59Ni in stainless steel samples, it is necessary to chemically reduce the content of 59Co in the sample. Further improvements in the reduction of the X-ray background and in the chemical reduction of cobalt have led to nearly a factor of 10 lower detection limit of 59Ni at the Lund AMS facility compared to what has been reported earlier. The content of 59Ni in some steel samples obtained from Swedish nuclear power plants has been measured and the results are presented here.

AMS studies of the long-term turnover of -labelled fat in man

Abstract To estimate the biokinetics of 14 C -labelled fatty acids and the associated radiation absorbed dose to man, long-term retention of 14 C from oral intake of glycerol tri[1- 14 C ]oleate (triolein) has been studied using accelerator mass spectrometry (AMS). As a complement to earlier reported data for three individuals, we present here results for one person from measurements up to 4.6 yr after administration, now also including 14 C -levels in fat, muscle and bone. In this subject, a total of 44% of the administered activity was recovered in the exhaled air. Fasting increased the exhalation of 14 C . The “excess” 14 CO 2 due to fasting had a half-life of about 400 d. AMS measurements on fat, muscle and bone biopsies taken from the same subject 4.5 yr after ingestion indicated that a small fraction of the administered activity was still present in fat. Also, bone tissue had a higher 14 C specific activity than the current environmental level. No significantly increased level was found in the muscle sample.

The charge state distribution of a carbon beam measured at the lund pelletron accelerator with the newly installed terminal pumping system in use

Charge state distributions for (12) C and C-13 ions have been measured at the Lund Pelletron tandem accelerator for the N-2 gas stripper with a newly installed terminal pumping system in use. A comparison of the results obtained for the ion energies between 1.5 and 2.8 MeV with the foil stripper and the gas stripper without terminal pumping demonstrates the great improvement of the stripping process achieved with the new terminal pumping

26Al investigations at the AMS-laboratory in Lund

At the accelerator mass spectrometry (AMS) laboratory in Lund, a facility for (26)Al analysis is under development. The sensitivity is expected to be several orders of magnitude higher than with standard mass spectrometry. The planned biomedical program includes studies of aluminium uptake, distribution and retention in man. The initial work has been concentrated on the construction and testing of a new dedicated injector for the accelerator and on the preparation of biological samples for aluminium analysis. The current quality of the facility is presented and the first experimental results reported.

Characteristic X-ray production in heavy ion collisions

The characteristic K X-ray production from projectile and solid target atoms in heavy ion collisions have been measured using a high-resolution Ge-detector. Ni projectiles in the energy range 15–25 MeV have been used to irradiate various thick targets made of materials in the Z range 22–32. In this energy region, the transition from predominantly quasi-molecular excitation to predominantly Coulomb excitation occurs. These measurements have been done in connection with our programme with a fairly new analytical technique, a combination of accelerator mass spectrometry (AMS) and the detection of characteristic X-rays. From the measurements, experimental K X-ray cross-sections have been extracted. Comparisons with other experimental data as well as with theoretical values are presented.

The pressure profile in the Lund Pelletron accelerator with the newly installed terminal pumping in use

Terminal pumping has recently been installed in the Lund tandem Pelletron electrostatic accelerator. The equipment allows a higher gas density in the stripper and an improved vacuum in the accelerator tubes compared to the former system. This improvement has led to an increased beam transmission and to superior measurements for our accelerator mass spectrometry programme. The pressure profile of the stripper system as well as of the accelerator tubes has been calculated using kinetic gas theory. The result will be used to identify possible technical improvements in the future.

Biokinetic and dosimetric investigations of 14C-labeled substances in man using AMS

Up to now, radiation dose estimates from radiopharmaceuticals, labeled with pure β-emitting radionuclides, e.g., 14C or 3H have been very uncertain. Using accelerator mass spectrometry (AMS) we have derived new and improved data for 14C-triolein and 14C-urea and are currently running a program related to the biokinetics and dosimetry of 14C-glycocholic acid and 14C-xylose. The results of our investigations have made it possible to widen the indications for the clinical use of the 14C-urea test for Helicobacter pylori infection in children. The use of ultra-low activities, which is possible with AMS (down to 1/1000 of that used for liquid scintillation counting), has opened the possibility for metabolic investigations on children as well as on other sensitive patient groups like new-borns, and pregnant or breast-feeding women. Using the full potential of AMS, new 14C-labeled drugs could be tested on humans at a much earlier stage than today, avoiding uncertain extrapolations from animal models.

Environmental radiation protection studies related to nuclear industries, using AMS

14C is produced in nuclear reactors during normal operation and part of it is continuously released into the environment. Because of the biological importance of carbon and the long physical half-life of 14C it is of interest to study these releases. The 14C activity concentrations in the air and vegetation around some Swedish as well as foreign nuclear facilities have been measured by accelerator mass spectrometry (AMS). 59Ni is produced by neutron activation in the stainless steel close to the core of a nuclear reactor. The 59Ni levels have been measured in order to be able to classify the different parts of the reactor with respect to their content of long-lived radionuclides before final storage. The technique used to measure 59Ni at a small accelerator such as the Lund facility has been developed over the past few years and material from the Swedish nuclear industry has been analyzed.

Radionuclides in man and his environment measured by accelerator mass spectrometry

Accelerator mass spectrometry (AMS) is a highly sensitive analytical method for measuring very low concentrations of both radionuclides and stable nuclides. For radioanalytical purposes, the main advantages of AMS compared to conventional radiometric methods are the use of smaller samples (mg size) and shorter measuring times (less than one hour). In this report some current applications of the AMS technique at the Lund Pelletron accelerator are presented, in particular studies of 14C-labeled pharmaceuticals used in clinical nuclear medicine and biomedical research.