Polarized proton target (PPT)

The photograph shows the polarized proton target. In this photograph, PPT is placed out of the beam axis. The size of PPT was 3 cm in diameter and 20 cm in length. Chromium-V doped pentanol was used as the target material. Using the polarizing mode of the solenoid magnet with the magnetic field of 25 kG, the free protons in the target material were polarized at the temperature of 400 mK with the microwaves of 70 GHz. After the maximum polarization was obtained, the solenoid magnet was moved to upstream (frozen spin mode). The frozen spin mode appeared at the temperature below 80 mK and magnetic field of 7 kG. In this condition, the proton spin relaxation time was longer than 50 days. The long data-taking time without re-polarization of free protons, therefore, was realized. The sign of the polarization was reversed every few days in order to reduce possible systematic errors. During the beam time, the average polarization observed was -0.808+/-0.026 for the negative polarization and +0.780+/-0.025 for the positive one.

by Seiji Makino