Method for producing glass particulate deposit and method for producing glass preform

A production method for a glass particulate deposit comprising:

• a deposition step where a starting rod and a burner for production of glass particles are installed in a reactor, a glass source material is introduced into the burner, the glass source material is subjected to flame thermal decomposition in the flame formed by the burner to thereby form glass particles, and the formed glass particles are deposited on the starting rod to produce a glass particulate deposit,
• wherein, in the deposition step, at least two ejecting ports are provided per one burner for ejecting the glass source material from the burner, and a gas flow velocity of the glass source material jetting out through one glass source material ejecting port is from 4 m/s to 60 m/s,
• wherein the burner is a columnar burner at a center of which at least three of the ejecting ports, around of which a seal gas port is arranged, are arranged at a position of each vertex of a regular polygon with vertexes equal or less than ten,
• the seal gas port is arranged to be substantially coaxial with a central axis of the columnar burner, and
• a hydrogen gas port is arranged on an outer periphery of the seal gas port of the columnar burner,
• wherein the burner is alternatively a linear burner in a center part of a widthwise direction of which the at least two ejecting ports, both sides of which a plurality of seal gas ports of the linear burner are arranged, are arranged linearly,
• a plurality of combustion gas ports are arranged on an outer side of the seal gas ports of the linear burner.