The polarized deuteron target at COMPASS in 2022
The COMPASS experiment at CERN used a upgraded transversely polarized deuteron target with a muon beam of 160 GeV/c for SIDIS measurements in 2022. The deuteron target material of 6LiD installed in 3 cells was polarized by DNP method with a 2.5 T magnet, a dilution refrig- erator and three 70 GHz microwave oscillators. During the data-taking the target operates in a transversely oriented magnetic dipole field at 0.6 T. This frozen spin operation mode without DNP process leads to a slow depolarization. So that, it is important to reach 40 % polarization that is sufficient for spin asymmetry measurement. The newly installed 3 microwave oscillators played a significant role to increase the polarization. We obtained deuteron polarizations of more than 40 % in each cell for two days. The relaxation time of the deuteron polarizations during the data taking period was measured as about 5000 h with 0.6 T and below 100 mK.
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