The present invention relates to a method for evaluating the thermal expansion properties of a titania-containing glass body. On the basis of measured values, obtained at a certain temperature, for a physical parameter that changes depending on the titania concentration and a physical parameter that changes depending on the fictive temperature, the thermal expansion coefficient of the titania-containing silica glass body and the slope of the thermal expansion coefficient are calculated using a linear relational expression represented by a plurality of physical properties. The thermal expansion properties of the titania-containing silica glass body are evaluated on the basis of the calculated thermal expansion coefficient and thermal expansion coefficient slope.

One aspect is a method for producing a hollow porous quartz glass base material, and a method for producing a synthetic quartz glass cylinder, wherein even when the hollow porous quartz glass base material (soot body) is produced in large weight and high bulk density, the ease of target extraction is maintained and target extraction is performed stably, and a large weight soot body can be produced. The method for producing a hollow porous quartz glass base material comprises: preparing a heat resistant substrate, which has a columnar or cylindrical shape and has an outer surface on which SiO.sub.2 particles are deposited, the outer surface having a surface roughness in which the maximum height Rz is less than 9 m and the arithmetic average roughness Ra is less than 1 m; rotating the heat resistant substrate and depositing SiO.sub.2 particles on the outer surface of the heat resistant substrate to form a glass particulate deposit; and extracting the heat resistant substrate from the glass particulate deposit to produce a hollow porous quartz glass base material.

A method and apparatus for manufacturing a quartz glass ingot of large cross-sectional area by continuous flame-fusion whereby on-line crack-free cutting of the ingot is ensured by using the internal heat of the ingot to permit equilibration of the internal and surface temperatures while passing through one or more annealing chambers, thus ensuring controlled cooling to temperature at which it is possible to cut the ingot with a water-cooled saw.

A method and apparatus for manufacturing a quartz glass ingot of large cross-sectional area by continuous flame-fusion whereby on-line crack-free cutting of the ingot is ensured by using the internal heat of the ingot to permit equilibration of the internal and surface temperatures while passing through one or more annealing chambers, thus ensuring controlled cooling to temperature at which it is possible to cut the ingot with a water-cooled saw.

A known method for homogenizing glass includes the following steps: providing a cylindrical blank composed of the glass, having a cylindrical outer surface which extends between a first end face and a second end face, forming a shear zone in the blank by softening a longitudinal section of the blank and subjecting it to a thermal-mechanical intermixing treatment, and moving the shear zone along the longitudinal axis of the blank. To reduce the risk of cracks and fractures during homogenizing, it is proposed that a thermal radiation dissipator is used that at least partially surrounds the shear zone, the lateral dimension of which in the direction of the longitudinal axis of the blank is greater than the shear zone and smaller than the length of the blank, the thermal radiation dissipator being moved synchronously with the shear zone along the longitudinal axis of the blank.

In an exemplary embodiment, a quartz glass crucible 1 includes: a straight body portion 1a having a cylindrical shape; a bottom portion 1b; and a corner portion 1c, in which a bubble content of an inner surface layer portion ranging from an inner surface to a depth 0.5 mm in an upper portion 1a.sub.1 of the straight body portion 1a is 0.2% to 2%, the bubble content of the inner surface layer portion in a lower portion 1a.sub.2 of the straight body portion 1a is more than 0.1% and not more than 1.3 times a lower limit of the bubble content of the upper portion 1a.sub.1, the bubble content of the inner surface layer portion in the corner portion 1c is more than 0.1% and 0.5% or less, and the bubble content of the inner surface layer portion in the bottom portion 1b is 0.1% or less.

The present invention pertains to: a method for manufacturing an ultraviolet-resistant quartz glass, said method including melting a synthetic silica powder; and a method for manufacturing an ultraviolet-resistant quartz glass, said method including performing arc plasma melting of a silica powder. Provided is an ultraviolet-resistant quartz glass having an ultraviolet-resistance of 2500 seconds, wherein, taking the initial transmittance during irradiation of a quadruple higher harmonic (266 nm) of a YAG laser (irradiation performed at a YAG laser output of 180 mW, pulse width of 20 nsec, and frequency of 80 kHz) at an optical path length of 30 mm to be 100%, the irradiation period until the transmittance falls to 3% is defined as resistance to ultraviolet rays (referred to as ultraviolet-resistance). Also provided is an optical member for YAG-laser higher harmonics, said optical member comprising this quartz glass.

The present invention pertains to: a method for manufacturing an ultraviolet-resistant quartz glass, said method including melting a synthetic silica powder; and a method for manufacturing an ultraviolet-resistant quartz glass, said method including performing arc plasma melting of a silica powder. Provided is an ultraviolet-resistant quartz glass having an ultraviolet-resistance of 2500 seconds, wherein, taking the initial transmittance during irradiation of a quadruple higher harmonic (266 nm) of a YAG laser (irradiation performed at a YAG laser output of 180 mW, pulse width of 20 nsec, and frequency of 80 kHz) at an optical path length of 30 mm to be 100%, the irradiation period until the transmittance falls to 3% is defined as resistance to ultraviolet rays (referred to as ultraviolet-resistance). Also provided is an optical member for YAG-laser higher harmonics, said optical member comprising this quartz glass.

Provided are a quartz glass crucible capable of withstanding a single crystal pull-up step undertaken for a very long period of time, such as multi-pulling, and a manufacturing method thereof.

A quartz glass crucible 1 includes: a cylindrical crucible body 10 which has a bottom and is made of quartz glass; and crystallization-accelerator-containing coating films 13A and 13B which are formed on surfaces of the crucible body 10 so as to cause crystallization-accelerator-enriched layers to be formed in the vicinity of the surfaces of the crucible body 10 by heating during a step of pulling up a silicon single crystal by a Czochralski method.

Provided are a quartz glass crucible capable of withstanding a single crystal pull-up step undertaken for a very long period of time, such as multi-pulling, and a manufacturing method thereof.

A quartz glass crucible 1 includes: a cylindrical crucible body 10 which has a bottom and is made of quartz glass; and crystallization-accelerator-containing coating films 13A and 13B which are formed on surfaces of the crucible body 10 so as to cause crystallization-accelerator-enriched layers to be formed in the vicinity of the surfaces of the crucible body 10 by heating during a step of pulling up a silicon single crystal by a Czochralski method.