[en] A conditioning procedure using N₂ or Ar gas is applied to a distributed ion pump (DIP) of the TRISTAN accumulation ring. Effectiveness and problems of conditioning are experimentally investigated. Only a slight effect is observed in the N₂ gas conditioning due to the great pressure difference along the beam duct, so that a uniform conditioning cannot be achieved. The Ar gas conditioning, on the other hand, well activates the DIP. Pumping speeds near the design value, ≅ 80 1 s^-1 per meter at pressures ≅ 1 x 10^-6 Pa, are obtained. The Ar component, however, increases after baking by more than a factor of 3 within 280 h. This increase makes it difficult to apply Ar gas conditioning to an accelerator ring. (author)