Manufacturing method for SiO2—TiO2 based glass, manufacturing method for plate-shaped member made of SiO2—TiO2 based glass, manufacturing device, and manufacturing device for SiO2—TiO2 based glass

A method for manufacturing an SiO2—TiO2 based glass upon a target by a direct method, comprising:

• a first process of preheating the target;
• and
• a second process of growing an SiO2—TiO2 based glass ingot to a predetermined length upon the target which has been preheated, wherein
• the target is heated in the first process such that, in the second process, a temperature of a growing surface of the glass ingot is maintained at or above a predetermined lower limit temperature,
• the target includes a thermal storage portion that accumulates heat during the first process, and a heat insulating portion that suppresses conduction of heat from the thermal storage portion in the direction opposite to that of the glass ingot,
• the thermal storage portion and the heat insulating portion comprise a plate-shaped first member and a plate-shaped second member, respectively,
• the first member has a larger thermal capacity than the second member,
• the second member has a lower thermal conductivity than the first member, and
• the thermal storage portion has convex portions upon a surface of the first member that is opposite to the glass ingot.