The HFML-FELIX institute houses an international user facility hosting a series of infrared free-electron lasers (FELs) that are available for experiments to both local and visiting (inter)national scientists. The lasers cover the infrared region from 2.8 – 150 µm with macropulse energies > 100 mJ (10 µs pulses @ 10 Hz). A major application of the FELs involves infrared ion spectroscopy, where vibrational spectra are obtained for the ionized molecules inside a mass spectrometer with the aim to elucidate their chemical structure. For this purpose, a high-resolution and high-sensitivity cryogenic ion trap mass spectrometer (MS) is required that will meet the diverse requirements of high sensitivity in analytical applications, high resolution in MS analysis, ion storage at cryogenic temperature leading to high spectral resolution in the IR spectra, and optical access to the ions in the cryogenic trap by the high pulse energies of the FELs. 1x Cryogenic ion trap mass spectrometer