Recombination of radiation defects in solid methane - neutron sources and cryo-volcanism on celestial bodies

TL;DR

This paper investigates radiation-induced defect recombination in solid methane, revealing two-stage relaxation phenomena that impact neutron source design and may explain cryo-volcanism on celestial bodies.

Contribution

It introduces a new model describing two-stage defect recombination in irradiated solid methane across a range of temperatures.

Findings

Recombination occurs around 20K and between 50-60K.

Experimental results align with the two-stage model.

Insights into cryo-volcanism mechanisms on celestial bodies.

Abstract

Physicochemical properties of solid methane exposed to ionizing radiation have attracted significant interest in recent years. Here we present new trends in the study of radiation effects in solid methane. We particularly focus on relaxation phenomena in solid methane pre-irradiated by energetic neutrons and electron beam. We compare experimental results obtained in the temperature range from 10K to 100K with a model based on the assumption that radiolysis defect recombinations happen in two stages, at two different temperatures. In the case of slow heating up of the solid methane sample, irradiated at 10K, the first wave of recombination occurs around 20K with a further second wave taking place between 50 and 60K. We also discuss the role of the recombination mechanisms in burp phenomenon discovered by J. Carpenter in the late 1980s. An understanding of these mechanisms is vital for the designing and operation of solid methane moderators used in advanced neutron sources and could also be a possible explanation for the driving forces behind cryo-volcanism on celestial bodies.