Measurement of ion cascade energies through resolution degradation of alpha particle microcalorimeters

Abstract

Atomic cascades caused by ions impinging on bulk materials have remained of interest to the scientific community since their discovery by Goldstein in 1902. While considerable effort has been spent describing and, more recently, simulating these cascades, tools that can study individual events are lacking and several aspects of cascade behavior remain poorly known. These aspects include the material energies that determine cascade magnitude and the variation between cascades produced by monoenergetic ions. We have recently developed an alpha particle detector with a thermodynamic resolution near 100 eV full-width-at-half-maximum (FWHM) and an achieved resolution of 1.06 keV FWHM for 5.3 MeV particles. The detector relies on the absorption of particles by a bulk material and a thermal change in a superconducting thermometer. The achieved resolution of this detector provides the highest resolving power of any energy dispersive technique and a factor of 8 improvement over semiconductor detectors. The exquisite resolution can be directly applied to improved measurements of fundamental nuclear decays and nuclear forensics. In addition, we propose that the discrepancy between the thermodynamic and achieved resolution is due to fluctuations in lattice damage caused by ion-induced cascades in the absorber. Hence, this new detector is capable of measuring the kinetic energy converted to lattice damage in individual atomic cascades. This capability allows new measurements of cascade dynamics; for example, we find that the ubiquitous modeling program, SRIM, significantly underestimates the lattice damage caused in bulk tin by 5.3 MeV alpha particles.

Experimental study ofβ-delayed proton decay ofAl23for nucleosynthesis in novae

“…Also, improved resolution is needed to distinguish any possible contribution from protons originating from the IAS in 23 Mg. Promising technologies, such as active target systems or superconducting micro-calorimeters [41] may make such improvements possible.…”

Cryogenic micro-calorimeters for mass spectrometric identification of neutral molecules and molecular fragments

“…In contrast, however, this main peak now has a clear tail extending towards low energies, suggesting that a small but significant part of the ion kinetic energy was not detected for a noticeable fraction of events with heavier atomic ions. In order to quantitatively describe the resulting asymmetric peak shape we extend our analysis by fitting the spectra by a convolution of a Gaussian function and a left-sided exponential function 47,64 …”

“…For details on the relations between E displ ; E latt , and E FP see, e.g., the SRIM documentation 58 or Figure 11 in Ref. 47. Adding all the systematic uncertainties together in quadrature gives a Frenkel-pair energy of E FP ¼ 2:860:9 eV.…”

“…[47][48][49] However, energy resolutions of only $10 À1 were reported for detecting atoms and molecules at energies of Շ10 keV, [40][41][42]44,50,51 i.e., in the regime most relevant for mass spectrometry. Only a few studies have attempted to understand this issue.…”

“…Quantitatively, Andersen's predictions for various detector types match to within an order of magnitude the energy resolutions measured later at MeV to GeV energies. 46 More recently Horansky et al have numerically modeled the micro-calorimeter energy spectra from 5.5 MeV a-particles 47 and have concluded that the dominant spectral broadening is due to lattice damages. Their model underestimates the energy spread by a factor of $2 compared to the measurements.…”