Toward a measurement of $\alpha$-decay lifetime change at high pressure: The case of ${}^{241}\mathrm{Am}$

This paper suggests that a change in the lifetime of the $\alpha$-decay process in ${}^{241}\mathrm{Am}$ may be detected at high pressures achievable in the laboratory, essentially, due to the extraordinary high compressibility of Am at the megabar range. The Thomas-Fermi model was used to calculate the effect of high pressure on the atomic electron density and the variation of the atomic potential of ${}^{241}\mathrm{Am}$. It was found that at pressures of about 0.5 Mbar the relative change in the lifetime of ${}^{241}\mathrm{Am}$ is about $-2\times {10}^{-4}$. Detailed experimental procedures to measure this effect by compressing the ${}^{241}\mathrm{Am}$ metal in a diamond-anvil cell are presented where diagnostics is based on counting of the 60-keV γ rays accompanying the α decay and/or mass spectrometry on the ${}^{237}\mathrm{Np}/{}^{241}\mathrm{Am}$ isotope ratio.

Figure 1

Bare-nucleus and screened nuclear potentials in α-decay tunneling as a function of the daughter-nucleus or α-particle relative distance. Data refer to ${}^{241}\mathrm{Am}$; separation between the $Q$ values and between the nuclear potential curves is magnified by a factor of 100.

Figure 2

Fractional variation of partial and total decay widths for ${}^{241}\mathrm{Am}$ as a function of compression. Variations refer to the bare nucleus (${\lambda }_b$) or matter at STP conditions (${\lambda }_0$), respectively.

Figure 3

Relative volume vs pressure curve for americium [34]. At 50 GPa the compression is about 2.

Figure 4

The inner part of a DAC, and the sample volume dimensions for reaching 1 Mbar are presented on the left.

Figure 5

One-detector setup.

Figure 6

Two-detector setup.

Figure 7

Source-detector distance error vs the difference in distance between the two detectors. Detector 2 is located at a distance of 5 cm from the source, and the allowed relative error in the number of counts is $1\times {10}^{-5}$.

Figure 8

Source-detector distance error vs the difference in distance between the two detectors. Detector 2 is located at a distance of 10 cm from the source, and the allowed relative error in the number of counts is $1\times {10}^{-5}$.

Figure 9

A simulation of the pressure distribution inside a diamond-anvil cell at a sample pressure of 40 GPa. The red color represents the maximum pressure of 40 GPa, whereas the blue color represents 0 pressure.