  Low-temperature detectors often use mechanical coolers as part of the cooling
chain in order to reach sub-Kelvin operating temperatures. The microphonics
noise caused by the mechanical coolers is a general and inherent issue for
these detectors. We have observed this effect in the ground test data obtained
with the Resolve instrument to be flown on the XRISM satellite. Resolve is a
cryogenic X-ray microcalorimeter spectrometer with a required energy resolution
of 7 eV at 6 keV. Five mechanical coolers are used to cool from ambient
temperature to about 4 K: four two-stage Stirling coolers (STC) driven
nominally at 15 Hz and a Joule-Thomson cooler (JTC) driven nominally at 52 Hz.
In 2019, we operated the flight-model instrument for two weeks, in which we
also obtained accelerometer data inside the cryostat at a low-temperature stage
(He tank). X-ray detector and accelerometer data were obtained continuously
while changing the JTC drive frequency, which produced a unique data set for
investigating how the vibration from the cryocoolers propagates to the
detector. In the detector noise spectra, we observed harmonics of both STCs and
JTC. More interestingly, we also observed the low (<20 Hz) frequency beat
between the 4'th JTC and 14'th STC harmonics and the 7'th JTC and the 23--24'th
STC harmonics. We present here a description and interpretation of these
measurements.
