keV 241Am Research Articles

Charge-transfer study of FeAl and CoAl using Compton scattering

Abstract A Compton scattering study, using 59.54 keV 241Am γ-rays, of the alloys Fe49.7Al50.3 and Co49.6Al50.4 is reported. The renormalized free-atom model is used to obtain the charge transfer from Al to the transition metal d band. The results are compared with inferences based on other experimental techniques. The assumptions on which our model is based and the errors in the data are analysed in terms of their effect on the estimate of charge transfer.

A permanently sealed multiwire proportional chamber with two-dimensional readout for X-ray applications in the region 20–60 keV

The construction and performance of a small (15 × 15 cm 2) MWPC with two-dimensional readout are described. Its volume is vacuum-pumped, filled with a Xe + Kr + H 2 mixture and then permanently sealed. The counter has been working for several months after filling, with no visible change in its parameters. Owing to the xenon filling, efficient detection (ca. 20%) and a spatial resolution of ca. 4 × 4 mm 2 are observed for the 60 keV 241Am line, through its escape peak.

Dual photon absorptiometry in lumbar vertebrae. II. Precision and reproducibility.

Bone mineral content in lumbar vertebrae is determined by the attenuation of 59.6 keV (241Am) and 662 keV (137Cs) photons using the intermittent scanning technique. The precision, mainly influenced by decay variations, is analyzed mathematically. The reproducibility in patient measurements is also affected by variations in positioning, movements during measurement and base line errors. In four normal subjects the reproducibility ranged from 3.4 to 5.7%. The long-term stability was better than 1% during a five-month period as tested by phantom measurements.

The estimation of total skeletal mass from bone densitometry measurements using 60 keV photons.

Abstract A bone densitometry technique previously described has been used to measure the “bone index” (g/cm−1) in 45 male skeletons by scanning the femur with 60 keV 241Am photons. A high correlation between this “bone index” and total skeletal mass was demonstrated. This suggests that a good estimate of the skeletal mass may be possible, in vivo by photon beam scanning. The technique is cheaper than whole body neutron activation analysis and patients undergo a less alarming investigation and receive lower radiation doses.

Symmetry of the compton profile of polycrystalline aluminum

The symmetry of the Compton profile in the high momentum region for polycrystalline aluminum has been investigated using 59.54 keV 241Am gamma rays. No asymmetry was found in the high momentum region of the Compton profile down to 5% of its maximum. This is in agreement with the prediction of the impulse approximation. It is in disagreement with a recent MoK α (17 keV) study of beryllium.

Compton profile anisotropy in graphite

The Compton profile in graphite was measured using 59.54 keV 241Am gamma rays. A significant anisotropy was found in agreement with reported positron-annihilation results but in contrast with recent Compton profile measurements using Mo Kα X-rays.

A developmnetal scintillation counter for detection of plutonium in vivo.

A scintillation counter utilizing 52 low-noise 2 in. phototubes with 1 mm sodium iodide crystals was fabricated for the detection of plutonium in vivo. When counting the 17 keV X-rays from plutonium deposited in the lungs, the counter has a sensitivity of 0.385 counts/min per nCi which increases to 2.63 counts/min per nCi when counting both the X-rays and the 60 keV 241Am gamma-rays. Background rates vary among individuals due to the presence of various isotopes (40K, 137Cs, etc.), but the background at higher energies can be used to predict the background rate in the 17 keV and 17 keV plus 60 keV regions. Two standard deviations of the background in the 17 keV X-ray region correspond to 20 nCi of plutonium in the lungs. The counter has been used to detect plutonium in people, animals, and biological samples.

Whole body counting of inhaled plutonium in dogs.

Thin NaI (Tl) scintillation counters were used for the assessment of body burdens in dogs exposed to 239Pu aerosol. Experiments were made with both a dog phantom and live dogs. Although the count rate was affected by changes in dog size and isotopic composition of the plutonium, the limiting factor in the accurate assessment of body burdens in our work was the distribution of the plutonium within the dog. Despite these problems, the body burdens of dogs have been determined with an accuracy of ±10% at 0.1 μCi levels. The average sensitivity obtained when counting the 17 keV X-rays emitted was 2.28 ± 0.16 counts/min/nCi and was 13.3 ± 1.1 counts/min/nCi when counting both the X-rays and 60 keV 241Am gamma rays. These sensitivities are based on body burdens determined by post-mortem alpha-counting analysis of the tissues of eight dogs that had previously been counted in the plutonium counter. In this study thirty exposed dogs were counted and body burdens ranging from 0.136 μCi to 3.12 μCi were observed.