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The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (√sNN = 2-4.9 GeV) is to discover fundamental properties of QCD matter, namely, the equation-of-state at high density as it is expected to occur in the core of neutron stars, effects of chiral symmetry, and the phase structure at large baryon-chemical potentials (μB ≥ 500 MeV).We are focusing here on the contribution of JINR to the CBM experiment: design of the superconducting dipole magnet; manufacture of the straw and micro-strip silicon detectors, participation in the data taking and analysis algorithms and physics program.

A precision liquid hydrogen bubble chamber with rapid cycling capability and a photographed volume of 150 × 70 × 50 mm 3 has been constructed to study short-living elementary particles. Its refrigeration system is operated with liquid helium. The chamber body, manufactured from the polycarbonate Lexan ® , is almost free of vibrations due to the innovative expansion system with two pistons operating in opposite directions. The chamber operates with 5 ms cycle time and a rate up to 30 s −1 . The chamber has already been cycled 6.7 million times and about 0.3 million pictures have been taken. At the hydrogen temperature of 29.8 K a track density of 150 bubbles/cm has been achieved with bubble diameters of 25 μm.