| 摘要 |
PROBLEM TO BE SOLVED: To provide a burner for production of a porous glass preform which can provide a porous glass preform having a desired density distribution according to the production method, does not cause cracking during piling or leave bubbles during vitrification by baking and allows improvement of the yield.SOLUTION: A burner for synthesis of a glass fine particle is provided with combustion gas jetting ports which are arranged outside a central glass raw material gas jetting port, concentrically in one or more rows relative to the glass raw material gas jetting port, with jetting ports of the same row including a small-bore-diameter combustion assisting gas jetting port having the same focal distance. The small-bore-diameter combustion assisting gas jetting ports of the same row vary in inner diameter in the circumferential direction of the same row. |
