  We performed a $\overline{d}$ beam study at the K1.8 beam line of J-PARC
Hadron Experimental Facility. 1.8 GeV/$c$ $\overline{d}$ beam yield was
measured to be 0.30 $\pm$ 0.04 counts/spill for 30 GeV 70 $\times 10^{12}$
protons/spill irradiated on a 66 mm thick of gold target with the vertical slit
opening widths of 2.2 mm, 5 mm and 5 mm for intermediate focus (IFV), mass slit
1 (MS1) and 2 (MS2), respectively. Corresponding $\overline{p}$ beam yield is
roughly estimated to be $\sim$ 0.3 Mcounts/spill for the same slit condition.
Then, the $\overline{d}/\overline{p}$ production ratio at extraction angle of 6
degrees is estimated to be $\sim 10^{-6}$. This is the first time measurement
of the $\overline{d}$ beam yield and $\overline{d}/\overline{p}$ production
ratio at J-PARC. Further beam line tuning may increase the $\overline{d}$ beam
yield.
