  We present research program and project for high-resolution
wavelength-dispersive spectrometer dedicated to low-energy X-ray spectroscopy
at the electron cooler of the CRYRING@ESR storage ring, which is a part of the
international Facility for Antiproton and Ion Research (FAIR) currently being
built in Darmstadt. Due to the unique shape of the electorn-ion recombination
X-ray source, resulting from the overlapping of the electron and ion beams in
the electron cooler, the spectrometer can work in the specific asymmetric von
Hamos (AvH) geometry. In order to completely eliminate the influence of Doppler
effect on the measured X-ray energies, two asymmetric von Hamos spectrometers
will be installed next to the dipole magnets on both sides of the electron
cooler to detect blue/red (0$^{\circ}$/180$^{\circ}$) shifted X-rays, e.g.
emitted in the radiative recombination (RR) process. The X-ray-tracing
Monte-Carlo simulations show that the proposed AvH spectrometer will allow to
determine with sub-meV precision, the low-energy X-rays (5-10 keV) emitted from
stored bare or few-electron heavy ions interacting with cooling electrons. This
experimental precision will enable accurate studies of the quantum
electrodynamics (QED) effects in mid-Z H- and He-like ions.
