Method and device for production of a quartz glass blank
A conventional method for the production of a quartz glass blank comprises a method step in which SiO 2 particles are generated by means of a series of deposition burners and deposited on a cylinder outer surface of a support, rotating about the longitudinal axis thereof to form a cylindrical porous SiO 2 soot body. The surface temperature of the forming soot body is altered by means of a temperature adjustment body. According to the invention, the above may be developed to give an economical method for the production of an SiO 2 soot body with low axial thickness variations and to provide a device of simple construction of the same, whereby the temperature adjustment body is applied in the form of a planar element running along a significant part of the SiO 2 soot body, which either acts on the soot body surface as a temperature-screening homogeneous heat sink or as a homogeneous reflector for temperature raising, by means of heat radiation. A device suitable for carrying out the above method is characterised in comprising a temperature adjustment body ( 13 ), with a planar element acting as a homogeneous heat sink or a homogeneous reflector which runs along a significant part of the SiO 2 soot body ( 2 ) and which has a given reflectance for IR radiation.
1 . A method for producing a quartz glass blank, said method comprising: a method step in which SiO 2 particles are produced by a row of deposition burners and deposited on a cylinder outer surface of a carrier rotating about a longitudinal axis thereof to form a cylindrical porous SiO 2 soot body, a temperature adjustment body altering a surface temperature of the soot body as it is being formed, wherein the temperature adjustment body comprises a planar element extending along a substantial part of the SiO 2 soot body, which either acts as a homogeneous heat sink and has a temperature-shielding effect on the soot body surface or, acts as a homogeneous reflector, and has a temperature-raising effect due to heat radiation.
2 . The method according to claim 1 , wherein said planar element is formed by an inner wall of a housing surrounding the SiO 2 soot body.
3 . The method according to claim 1 , wherein the planar element acts as a reflector with a reflectance for IR radiation between 80% and 100%.
4 . The method according to claim 3 , wherein heat of the deposition burners is reflected towards the soot body by means of the planar element.
5 . The method according to claim 3 , wherein heat of the forming SiO 2 soot body is reflected by means of the planar element towards the soot body surface.
6 . The method according to claim 1 , wherein the planar element has an efficiency, defined as a solid angle covering the forming SiO 2 soot body, of at least 60%.
7 . The method according to claim 1 , wherein the planar element acts as a heat sink absorbing IR radiation.
8 . The method according to claim 7 , wherein the planar element has a roughened surface having a mean surface roughness R a of at least 10 μm.
9 . The method according to claim 7 , wherein the planar element has a blackened surface.
10 . The method according to claim 7 , wherein the planar element is cooled.
11 . The method according to claim 3 , wherein the planar element is moved along the soot body.
12 . The method according to claim 3 , wherein the distance between the planar element and the surface of the forming SiO 2 soot body is kept constant.
13 . The method according to claim 1 , wherein the planar element extends over the whole usable length of the soot body.
14 . A device for carrying out the method according to claim 1 , said device comprising: a row of deposition burners for producing SiO 2 particles, a carrier which is rotatable about the longitudinal axis thereof and having a cylinder outer surface on which the produced SiO 2 particles are deposited to form a cylindrical porous SiO 2 soot body, and at least one temperature adjustment body that is supported in an area of the forming soot body and that acts on a surface temperature of the forming soot body for altering an axial density profile, wherein the temperature adjustment body comprises a planar element that acts as a homogeneous heat sink or as a homogeneous reflector and that extends along a substantial part of the SiO 2 soot body and has a predetermined reflectance for IR radiation.
15 . The device according to claim 14 , wherein the planar element is formed by an inner wall of a housing surrounding the SiO 2 soot body.
16 . The device according to claim 14 , wherein the planar element has a reflectance between 80% and 100% for IR radiation.
17 . The device according to claim 16 , wherein the planar element has a concave curvature.
18 . The device according to claim 16 , wherein the concave curvature has a focal point which is located in an area of the row of deposition burners.
19 . The device according to claim 16 , wherein the concave curvature comprises a focal point which is located in the area of the forming SiO 2 soot body.
20 . The device according to claim 14 , wherein the planar element comprises a surface absorbing IR radiation.
21 . The device according to claim 20 , wherein the planar element is roughened and has a mean surface roughness R a of at least 10 μm.
22 . The device according to claim 20 , wherein the planar element has a blackened surface.
23 . The device according to claim 20 , wherein the planar element is provided with a cooling device.
24 . The device according to claim 16 , wherein the planar element is supported for movement along the soot body.
25 . The device according to claim 16 , wherein the planar element is made displaceable in a direction perpendicular to the longitudinal axis of the carrier.
26 . The device according to claim 14 , wherein the planar element extends over the whole usable length of the soot body.