  Cryogenics is a pivotal aspect in the development of quantum technologies.
Closed-cycle devices have recently emerged as an environmentally friendly and
low-maintenance alternative to liquid helium cryostats. Yet the larger level of
vibrations in dry cryocoolers forbids their use in most sensitive applications.
In a recent work, we have proposed an inertial, broadband, contactless sensor
based on the piezospectroscopic effect, ie the natural sensitivity of optical
lines to strain exhibited by impurities in solids. This sensor builds on the
exceptional spectroscopic properties of rare earth ions and operates below 4K,
where spectral hole burning considerably enhances the sensitivity. In this
paper, we investigate the fundamental and technical limitations of this
vibration sensor by comparing a rigid sample attachment to cold stage of a
pulse-tube cryocooler and a custom-designed exchange gas chamber for acoustic
isolation.
