Abstract: A method for feeding a flow of gas to a burner for manufacturing an optical fibre preform. The burner has a plurality of coaxial tubes, each two adjacent coaxial tubes defining an annular channel between themselves; an annular gas distribution chamber at one extremity of the annular channels and in fluid communication therewith, the annular distribution chamber being delimited in the radial direction by an inner and an outer surface. The flow of gas is introduced into the distribution chamber so that the direction of its radially outermost portion is tangential to the radially outer surface of the distribution chamber. The method allows obtaining a better gas velocity distribution in the annular channels.

Abstract: A device for manufacturing a preform of glass material for optical fibres. A chemical deposition chamber, at least one burner mobile along a direction Z and adapted to deposit a chemical substance on at least an elongated element positioned along an axis Z-Z, at least one suction element mobile along the direction Z for collecting exhaust chemical substances, a collector tube associated with the at least one suction element and adapted to discharge the exhaust chemical substances outside the chemical deposition chamber through an exhaust opening formed on a wall of the chamber, and a coupling device between the collector tube and the wall at the exhaust opening, allowing sliding of the collector along the direction Z and along a direction X towards/away from the axis z-z.

Abstract: A burner which prevents obstruction by combustion products has a circularly concentric multi-tube construction of three or more tubes, comprising a central tube which emits a liquid containing a chemical element that forms a solid oxide by combustion or flame hydrolysis, a first outer tube disposed concentrically outside the central tube for emitting a combustion-supporting gas and/or a non-combustible gas, a second outer tube disposed concentrically outside the first outer tube for emitting a combustion-supporting gas and/or a non-combustible gas, and optionally, a passage disposed outside the second outer tube for supplying a combustion-supporting gas and/or a non-combustible gas. The liquid emitted from the central tube is atomized and burned by the combustion-supporting gases and/or non-combustible gases supplied from the outer tubes and the optional passage disposed outside thereof.

Abstract: A chemical deposition chamber includes at least one gripping member rotatably mounted about an axis Z-Z adapted to hold at least one end of at least one elongated element for chemical vapour deposition for the formation of a preform. The chamber includes at least one burner which is mobile along a direction substantially parallel to the axis Z-Z and adapted to deposit, on the elongated element, a chemical substance for the formation of a preform, and at least one suction element arranged on the opposite side of the burner on a portion of a wall of the chamber on the opposite side of the gripping member from the burner. At least one air suction member, mobile along direction Z, is provided with a motion which is synchronous with respect to that of the burner. The chamber wall on which the air suction member is provided has a pair of respective upper and lower tapes rigidly associated with the burner.

Abstract: The present invention relates to a method of making a soot particle and apparatus for making such soot particle. Preferably the method of making the soot particle is substantially free of the step of combusting a fuel and substantially free of the step of forming a plasma. Preferably, the apparatus is devoid of a heating element associated with both combustion and formation of a plasma. A preferred technique for at least one heating step for forming the doped soot particle is induction heating.

Abstract: A burner for use in the manufacture of quartz glass is provided, which comprises a triple-tube assembly of a center tube for feeding a silane or siloxane compound, an intermediate tube for feeding oxygen, and an outer tube for feeding hydrogen, a first tubular shell surrounding the triple-tube assembly for feeding hydrogen, a plurality of first nozzles disposed within the first tubular shell for feeding oxygen, a second tubular shell surrounding the first tubular shell for feeding hydrogen, and a plurality of second nozzles disposed within the second tubular shell for feeding oxygen. Synthetic quartz glass ingots having high optical homogeneity are produced.

Abstract: Burners (14) are used to make glass bodies (19) from OMCTS. The burners have six concentric regions. Putting certain gases through the regions results in thicker bodies than can be achieved with existing techniques and with improved efficiency.

Abstract: Multi-flame burner wherein each flame is separated with respect to the neighboring flame by at least one separating tube made of a heat resistant material, for example, quartz glass or ceramic material. The burner also has a plurality of co-axial pipes, preferably made of a metallic material. The cross section of the upper end of the separating tube can be modified in order to increase the deposition rate of the burner. Methods for manufacturing optical fibre preforms by vapour deposition using the multi-flame deposition burners.

Abstract: Method and burner for increasing the deposition rate of porous glass deposit in the manufacture of optical preforms, by modifying the cross-sectional shape of the flow of glass particles impacting onto a target preform. In particular, the cross-section of the flow of glass particles is modified by increasing the dimension of the flow from a circular cross-section to one having a major and minor axis in a direction substantially perpendicular to the longitudinal axis of the target preform.

Abstract: A mandrel for producing quartz glass, comprising at least two columnar or cylindrical, carbon fiberreinforced carbon composite material made members joined in series by screw thread parts. The mandrel is carbon-impregnated and/or carbon-coated on the screw thread parts, and, in addition, may be provided with reinforcing members on the outer sides of the screw thread parts. Quartz glass fine particles obtained by flame-hydrolyzing a volatile silicon compound are deposited, using this mandrel, on the surface of a heat-resisting substratum or on a starting rod at the end of the mandrel to easily form a large porous quartz glass mother material, the porous quartz glass mother material is dehydrated and transparently vitrified to produce a large optical fiber mother material, and further the optical fiber mother material is drawn to produce a low-cost, high-precision optical fiber.

Abstract: Burners and methods for producing fused silica members. The burner includes seven gas-emitting regions, including four regions for emitting a mixture of oxygen and combustible gas.

Abstract: A reaction chamber including a reaction chamber in which preform is formed is provided. A cladding burner for forming a cladding of the preform is arranged in the reaction chamber, and a blocking member for suppressing ascending of the air in the reaction chamber is provided above the cladding burner. With this arrangement, abrupt flame-up of a flame containing glass particles produced through the burner is suppressed, the productivity of a preform is improved by accelerated formation of a preform, and the amount of glass particles which may adhere to a wall of the reaction chamber is reduced.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: To provide an apparatus for manufacturing a glass particles deposit in which it is possible to effectively prevent the foreign matter from being deposited on or mixed into the glass particles deposit during the manufacturing operation. The apparatus for manufacturing the glass particles deposit comprises an upper funnel, a reaction vessel and a lower funnel, wherein the glass particulates are deposited around the outer circumference of a starting rod supported by a support rod within the reaction vessel while the starting rod is being rotated around its axis and reciprocated up and down, characterized in that a sleeve made of quartz separating an inner wall of the reaction vessel and a central rotation member is installed inside the reaction vessel.

Abstract: Methods and apparatus for producing fused silica members having high internal transmission are disclosed. The apparatus and methods are capable of producing fused silica having internal transmission of at least 99.65%/cm at 193 nm.

Abstract: An object of the present invention is to reduce the adhesion of floating glass particulates to the surface of a soot preform during the manufacture of the soot preform, thereby reducing the voids generated in the transparent glass preform made from the soot preform, and to improve the quality of the optical fiber manufactured from the transparent glass preform. The equipment of the invention is equipped with a reaction vessel 1, a burner 2 provided within the reaction vessel 1 into which raw material gas and combustion gas are supplied so as to generate glass particulates by hydrolysis reaction, and a starting rod 5 onto which the glass particulates generated by the burner 2 are deposited. By drawing up the starting rod 5 while turning it around its axis, the glass particulates are deposited on the tip of or around the starting rod 5 to form a soot preform 6 in column-like shape.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, comprising: a base rod, around and along which said glass base material is formed; a burner that hydrolyzes and accumulates a gas material, which is a base material of said glass base material, around and along said base rod; a first burner-moving-unit that moves said burner in a direction parallel with a longitudinal direction of said base rod; and a second burner-moving-unit that moves said first burner-moving-unit in a same moving direction of said first burner-moving-unit.

Abstract: A method and apparatus for manufacturing optical components. A burner generates soot, and a surface area collector collects the soot. The burner is disposed such that the soot collected within the surface area collector is substantially not reheated by subsequently deposited soot. Magnetic forces direct the soot to desired location(s) within the surface area collector. The surface area collector operates at relatively low temperatures sufficient to retain rather volatile substances, such as fluorine, in the soot.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, comprising: a base rod, around and along which said glass base material is formed; a burner that hydrolyzes and accumulates a gas material, which is a base material of said glass base material, around and along said base rod; a first burner-moving-unit that moves said burner in a direction parallel with a longitudinal direction of said base rod; and a second burner-moving-unit that moves said first burner-moving-unit in a same moving direction of said first burner-moving-unit.

Abstract: Burners (40) for producing fused silica boules are provided. The burners employ a tube-in-tube (301-306) design with flats (56, 50) on some of the tubes (305, 301) being used to limit the cross-sectional area of certain passages (206, 202) within the burner and/or to atomize a silicon-containing, liquid source material, such as OMCTS. To avoid the possibility of flashback, the burner has separate passages for fuel (205) and oxygen (204, 206), i.e., the burner employs nozzle mixing, rather than premixing, of the fuel and oxygen. The burners are installed in burner holes (26) formed in the crown (20) of a furnace and form a seal with those holes so that ambient air cannot be entrained into the furnace through the holes. An external air cooled jacket (60) can be used to hold the temperature of the burner below a prescribed upper limit, e.g., 400° C.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, comprising: a base rod, around and along which said glass base material is formed; a burner that hydrolyzes and accumulates a gas material, which is a base material of said glass base material, around and along said base rod; a first burner-moving-unit that moves said burner in a direction parallel with a longitudinal direction of said base rod; and a second burner-moving-unit that moves said first burner-moving-unit in a same moving direction of said first burner-moving-unit.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, comprising: a base rod, around and along which said glass base material is formed; a burner that hydrolyzes and accumulates a gas material, which is a base material of said glass base material, around and along said base rod; a first burner-moving-unit that moves said burner in a direction parallel with a longitudinal direction of said base rod; and a second burner-moving-unit that moves said first burner-moving-unit in a same moving direction of said first burner-moving-unit.

Abstract: Vent holes are provided on a reaction vessel in the vicinity of burners which are placed in the reaction vessel. The gas of different flow rate and/or temperature is supplied through the vent holes toward a soot body in a length direction of the soot body.

Abstract: In a known procedure for manufacture of a quartz glass body, a glass starting material and fuel gas are fed to a rotationally symmetrical deposition burner (1) having several annular gap nozzles (7-9) and being formed by coaxial arrangement of a number of quartz glass tubes (2-5), such glass starting material in a burner flame forming SiO2 particles which, under back and forth motion of the deposition burner (1) along the longitudinal axis of a rotating mandrel (12), are deposited on such rotating mandrel under formation of an essentially cylindrical porous blank. To enable replacement of such deposition burner without major efforts in terms of work and costs, the procedure of the inventioin proposes to use a deposition burner (1) the annular gap nozzles (7- 9) of which have gap widths with a maximum dimensional deviation of 0.

Abstract: In an apparatus for producing glass particles deposit according to the present invention, a plurality of glass particle synthesis burners are placed on a front face of a reaction vessel, and at least one exhaust port is provided on a rear face of the reaction vessel. Two wall faces extending from both sides of the exhaust port and being in contact with two side faces of the reaction vessel are provided so that its contained angle is 90 degrees or less. Assuming that the shorter distance between the shortest distance from a rotation axis of a target rod to the side face of the reaction vessel and the shortest distance from the rotation axis of the target rod to the wall face is L, and the outer diameter of the glass particles deposit deposited on the target rod is d, L is greater than d.

Abstract: A device for manufacturing a preform for optical fibers is described, comprising a chemical deposition chamber including at least one gripping member rotatably mounted about an axis Z-Z and adapted to hold at least one end of at least one elongated element constituting a substrate for chemical deposition for forming a preform for optical fibers. The chamber further includes at least one burner which is mobile along a direction substantially parallel to said axis Z-Z and suitable for depositing, on said at least one elongated element, a chemical substance for forming a preform, and at least one suction element arranged on the opposite side to said at least one burner with respect to said axis Z-Z and adapted to collect and discharge, from said chemical deposition chamber, exhaust chemical substances.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, the glass base material having a core rod as a central axis, comprises a holding unit having a plurality of scroll chucks connected in series along the core rod for holding an end of the core rod; and a burner that hydrolyzes a gas material, which is abase material of the glass base material, into glass particles and accumulates the glass particles around the core rod to form the glass base material.

Abstract: An apparatus for manufacturing an optical fiber soot according to a VAD method, in which a cross-section shape of a combustion nozzle of a side burner for heating a core portion is rectangular. A method for manufacturing an optical fiber soot using the apparatus.

Abstract: An apparatus for manufacturing an optical fiber soot, which comprises a core partition having an opening portion at core burner side provided on a periphery of a core burner, in a reactor of the apparatus to be used in a conventional VAD method.

Abstract: In a known procedure for manufacture of a quartz glass body, a glass starting material and fuel gas are fed to a rotationally symmetrical deposition burner (1) having several annular gap nozzles (7-9) and being formed by coaxial arrangement of a number of quartz glass tubes (2-5), such glass starting material in a burner flame forming SiO2 particles which, under back and forth motion of the deposition burner (1) along the longitudinal axis of a rotating mandrel (12), are deposited on such rotating mandrel under formation of an essentially cylindrical porous blank. To enable replacement of such deposition burner without major efforts in terms of work and costs, the procedure of the invention proposes to use a deposition burner (1) the annular gap nozzles (7-9) of which have gap widths with a maximum dimensional deviation of 0.

Abstract: Fused silica created by pyrolysis of SiCl4 are introduced in a powder state into a vacuum chamber. Pluralities of jet streams of fused silica are directed towards a plurality of heated substrates. The particles attach on the substrates and form shaped bodies of fused silica called preforms. For uniformity the substrates are rotated. Dopant is be added in order to alter the index of refraction of the fused silica. Prepared soot preforms are vitrified in situ. The material is processed into quartz tubes for fiber optics and other applications, quartz rods for fused silica wafers for semiconductors and various optical applications and quartz plates for wafer processing and optical windows.

Abstract: An apparatus for producing a glass soot includes a first a burner having a droplet-emitting first region, a gas-emitting second region surrounding the first region, and a gas-emitting third region surrounding the second region. The first region emits a glass-forming mixture, the second region emits an inert gas, and the third region emits a combination of oxygen and a combustible gas. The apparatus further includes a combustion area having a first section proximate the first burner and a second section distal from the first burner. A glass-forming mixture is at least partially vaporized in the first section of the combustion area. The apparatus further includes at least one secondary burner having gas-emitting fourth and fifth regions. The fourth region of the secondary burner emits oxygen and the fifth region of the secondary burner emits a combustible gas.

Abstract: A method is provided for manufacturing a silica glass that is substantially free of chlorine. The method includes the step of separately expelling a silicon tetrafluoride gas, a combustion gas, and a combustible gas from a burner made of silica glass, the flow velocity of the silicon tetrafluoride gas being within the range of about 9 slm/cm2 to about 20 slm/cm2. The method further includes the steps of producing minute silica glass particles by reacting the silicon tetrafluoride gas with water produced by a reaction of the combustion gas with the combustible gas, depositing the minute silica glass particles on a target, and producing the silica glass by fusing and vitrifying the minute silica glass particles deposited on the target.

Abstract: An apparatus for fabricating a soot preform for an optical fiber. The soot preform is fabricated by depositing glass particles on a starting rod capable of being rotated and pulled up. The apparatus comprises elements as follows. A reaction chamber is used for depositing the glass particles on the starting rod. An upper room is located above the reaction chamber for receiving the soot preform formed in the upper portion of the reaction chamber. At least one core burner is installed in the reaction chamber. A gas-supplying inlet is located in the top part of the sidewall of the reaction chamber closest to burner(s), and a gas-exhausting outlet is located in the top part of another sidewall opposite to the gas-supplying inlet. In addition, at least one cladding burner is installed in the reaction chamber.

Abstract: In furnaces for producing high purity fused silica glass boules, glass particles have a tendency to build-up adjacent the burner hole rim. It was discovered that unburned furnace gases containing silica particles where re-circulated in the furnace close to the burner hole rim and reacted with the oxygen of infiltrated air adjacent the burner hole, and thus deposited such particles in the form of a glassy build-up about the rim of the burner hole. In order to eliminate the source of oxygen adjacent the burner hole rim, a curtain of an inert gas is caused to flow through the burner hole between the sidewalls of the burner hole and the flame of the burner. Accordingly, the curtain of inert gas inhibits the combustion of the unburned hydrogen and carbon monoxide furnace gases adjacent the exit rim of the burner hole and thereby minimizes glass build-up about the burner hole rim.

Abstract: An apparatus for producing the glass soot used in the formation of optical fiber includes a burner with an internal atomizer. The atomizer includes an outer tube having a nozzle at an end thereof, and an inner tube located within the outer tube and having a closed end restricting fluid flow therethrough and defining a cylindrical sidewall having radially extending apertures spaced there along. The outer tube receives the glass-forming mixture in liquid form and the inner tube receives an atomizing gas which flows through the apertures in the sidewall of the inner tube and atomizes the glass-forming mixture as the glass-forming mixture travels through the outer tube.

Abstract: A method of manufacturing a preform, the method comprising rotating a primary preform about an axis X, establishing relative displacement in translation between the preform and a plasma torch, and introducing a glass powder into the plasma flame, the glass powder being accelerated prior to penetrating into the plasma flame by an accelerator gas introduced into the flow of glass powder, said process being performed in an enclosure and said introduction being performed into an atmosphere at a regulated pressure lower than the pressure outside the enclosure. Apparatus for manufacturing the preform comprises an enclosure connected to a unit for regulating the pressure inside the enclosure.

Abstract: Methods, apparatus and precursors for producing substantially water-free silica soot, preforms and glass. The methods and apparatus make substantially water-free fused silica preforms or glass by removing water as a reaction product, removing water from the atmosphere, removing water from the transport process, or combinations thereof. In a first embodiment, substantially water-free soot, preforms or glass are achieved by using a hydrogen-free fuel, such as carbon monoxide, in the deposition process. In another embodiment, a soot producing burner has parameters that enable operation on a substantially hydrogen-free fuel. End burners, which minimize water production, are also described. Such water-free methods are useful in depositing fluorine-doped soot because of the low water present and the efficiency in which fluorine is incorporated. In another embodiment, glassy barrier layer methods and apparatus are described for minimizing dopant migration, especially fluorine.

Abstract: An apparatus and process for cooling a quartz tube used in fabrication of an optical fiber preform by modified chemical vapor deposition. The apparatus has a nozzle ring supplied with a coolant. The nozzle ring has at least two vent sections that are be separatable for detaching the quartz tube from a lathe during processing, and a plurality of vents formed along the inside of the two vent sections for ejecting the coolant.

Abstract: A hooded glass particulate synthesizing torch, provided with at least a glass particulate synthesizing torch body having a feedstock gas injection passage formed at the center of its front end, a combustible gas injection passage formed concentrically at the outer circumference of the feedstock gas injection passage, and a plurality of small diameter combustion aid gas injection passages formed in the combustible gas injection passage along the outer circumference of the feedstock gas injection passage and a hood projecting out at the outer circumference of the front end of the torch body, the torch hood satisfying 0.5≦D/L≦2.0, where, L is the focal distance, that is, a distance from a point P, to which the small diameter combustion aid gas injection passages are directed and on an extension of the center line of the torch body in front of the torch body, to the front end of the torch body, and D is the hood length, that is, the distance from the front end of the hood to the front end of the torch body.

Abstract: The object of the invention is to provide an apparatus for manufacturing a porous glass preform, which comprises a reaction vessel in which local stress concentration caused by expansion due to heat is prevented, and there is no fear of the occurrence of deformation or cracks. The apparatus of this invention manufactures the porous glass preform by depositing glass particles blown from a burner on the seed rod rotating around its axis, and this apparatus is characterized in that the reaction vessel is provided with a means for relieving concentration of stress due to thermal expansion of the reaction vessel.

Abstract: A method and apparatus for producing a glass base material for an optical fiber. A material for an optical fiber and a reaction gas are jetted from a burner connected to a material line and a gas line toward a surface of a quartz substrate, in order to deposit a soot-like reaction product on the substrate at a predetermined position to thereby produce a glass base material for an optical fiber. Dry air is introduced into a reaction container in an amount of 2 to 30 times the amount of water vapor that is generated due to flame hydrolysis during the reaction.

Abstract: A method and a burner for manufacturing silica-containing soot is disclosed. The method includes providing a liquid silicon-containing feedstock and a gas mixture and ejecting the liquid-gas mixture from an orifice into a combustion site to convert the silica-containing feedstock into silica containing soot. The burner includes a plurality of channels for delivering a gas to provide a flame, an effervescent atomizer for atomizing a liquid, silicon-containing feedstock and a rail for guiding the atomized liquid, silicon-containing feedstock into the burner flame. The method and burner can be used to produce silica-containing articles such as high purity fused silica optical members and waveguides.

Abstract: The invention relates to apparatus for supporting a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, said installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to said supporting core and being mounted to move in axial translation relative to and parallel to the supporting core so as to make said preform around said supporting core, said apparatus being wherein it includes controlled support means constituting additional localized abutment points between said mounting points for said preform being manufactured or built up.

Abstract: Proposed is an improvement in the VAD process for the preparation of a porous silica glass preform for double-core optical fibers by using three oxyhydrogen flame burners installed one above the other in a flame hydrolysis chamber in which a porous silica glass body consisting of the center core portion formed by the lowermost burner, side core portion formed by the middle burner and the cladding layer formed by the uppermost burner is gradually pulled up as it grows under rotation. Different from conventional procedures in which the extension of the nozzle axis of each of the burners intersects with the rotation axis of the growing body, the extension of the nozzle axis of the middle burner for the side core is displaced in a horizontal direction by a limited distance not to intersect nor to be in parallel with the rotation axis in the invention. By this means, an improvement is obtained in the uniformity of distribution of the refractive index in the side core which otherwise is remarkably disordered.

Abstract: Disclosed is a process of producing an optical fiber preform having a step of charging a feedstock gas in an oxygen-hydrogen burner via an electrode and hydrolyzing the same in an oxygen-hydrogen flame to produce particulates containing charged glass particulates and a step of blowing the charged particulates onto a target comprised of a seed rod or a soot body formed on the seed rod so as to cause them to deposit on the target and build up as a soot body. Preferably, the process includes the further step of reducing the magnitude of the charge of the particulates in the burner along with an increase of the diameter of the target which is formed. More preferably, the process also includes the further step of making the position facing the burner across the target an opposite polarity from the charging polarity of the particulates ejected from the burner so as to electrically attract the particulates ejected from the burner.

Abstract: A method for making an optical fiber preform comprises depositing fine particles of glass serving as a dad on the surfaces of a rod-shaped core over a given length of the rod-shaped core by use of a plurality of oxyhydrogen flame burner units, detecting an amount of the resultant deposit to check uniformity in the amount of the deposit along the lengthwise direction of the rod-shaped core during the course of the deposition, and further depositing fine particles of glass on any surface portion of the rod-shaped core within the given length from at least one burner unit other than the plurality of burner units to correct the amount of the deposit over the given length based on the results of the detection. The resultant deposit is dehydrated and fired by a usual manner to obtain a preform. An apparatus for carrying out the method is also described.

Abstract: A precision burner for oxidizing halide-free, silicon-containing compounds, such as, octamethylcyclotetrasiloxane (OMCTS), is provided. The burner includes a subassembly (13) which can be precisely mounted on a burner mounting block (107) through the use of an alignment stub (158), a raised face (162) on the burner mounting block (107), and a recess (160) in the back of the subassembly (13). The burner's face includes four concentric gas-emitting regions: a first central region (36, 90) from which exits a mixture of OMCTS and O.sub.2, a second innershield region (38, 92) from which exits N.sub.2, a third outershield region (40, 42, 94, 96) from which exits O.sub.2, and a fourth premix region (44, 98) from which exits a mixture of CH.sub.4 and O.sub.2. The burner provides more efficient utilization of halide-free, silicon-containing raw materials than prior burners.

Abstract: A linear burner for the synthesis of silica by vapor-phase reaction of a silicon-containing feedstock in a flame comprises at least five slots opening to an exit face (52a) of the burner and extending side-by-side in the elongate direction of the linear burner, and includes means (P1-P10) to supply a separate gas flow to each of said slots. An assembly of separator plates (52) is disposed between opposed casing parts (50, 51), which assembly defines the slots. At least one of the casing parts (50, 51) defines at least part of a respective plenum chamber (54) for each gas flow, each plenum chamber (54) communicating with a different one of said slots in the separator assembly. The invention also extends to a method of operating such a linear burner.

Abstract: Recent UV-lithography is required to provide a fine and sharp pattern with a line width of 0.5 .mu.m or less. A silica glass member adapted for use as an optical element for UV-lithography, by giving consideration to the RMS value of wave front aberration and the slant element of refractive index, which have not been considered in the art. Also there is provided a silica glass member excellent in durability to the ultraviolet irradiation, by introduction of hydrogen molecules at the synthesis of the silica glass, instead of using a secondary treatment for hydrogen introduction.