JP6041347B2 - Fixed point crucible and fixed point blackbody furnace - Google Patents

Description

  The present invention relates to a fixed-point crucible and a fixed-point blackbody furnace used for calibration and evaluation of various thermometers such as a radiation thermometer that measures a surface temperature of a measurement object at high speed without contact.

  2. Description of the Related Art Conventionally, radiation thermometers that measure temperature by detecting infrared rays emitted from an object have been widely used because they can be measured at high speed and relatively accurately. This radiation thermometer is a thermometer capable of measuring the surface temperature of an object in a non-contact manner by measuring infrared rays (electromagnetic waves having a wavelength longer than the visible light region in the range of about 0.77 to 1000 μm) emitted from the object to be measured. In particular, it is used for food control and temperature control in places that are difficult to touch directly in the industrial sector.

  Non-Patent Document 1 below contains pure metal (for example, In, Sn, Zn, Al, Ag, Cu, etc.) as a fixed point material in a fixed point crucible made of high purity graphite. A fixed-point blackbody furnace is disclosed in which the temperature of a thermometer to be calibrated is calibrated by using the latent heat inside the crucible by heating the furnace with an electric furnace.

  FIG. 5 is a schematic cross-sectional view showing an apparatus configuration of a conventional fixed-point blackbody furnace disclosed in Non-Patent Document 1 below. As shown in the figure, a fixed point blackbody furnace 200 is provided in a temperature calibration device that performs temperature calibration of a thermometer to be calibrated such as a radiation thermometer, and is an outer cylinder 201 made of high-purity graphite that contains a fixed-point substance. A fixed point crucible 204 having a measurement opening 202 for measuring a temperature fixed point, and an inner cylinder 203 which is accommodated in the outer cylinder 201 and becomes a black body cavity, and a fixed point crucible 204 to be accommodated A gas injection part 205 for introducing an inert gas that prevents oxidation of the fixed point crucible 204 is provided on the side facing the measurement opening 202, and the stainless steel leveling member to which the lid member 206 is mounted after the fixed point crucible 204 is accommodated. The heat vessel 207, a pair of heat insulating materials 208 provided outside both end surfaces of the heat equalizing vessel 207, and the pair of heat insulating materials 208 centered on the heat equalizing vessel 207 are aligned and sandwiched between the center lines of the heat equalizing vessel 207. And alumina tube 209 which houses a state, and a radiation shield member 210 for shielding the radiant heat from the alumina tube 209.

Japanese Industrial Standard “JIS C1612 Radiation Thermometer Performance Test General Rules” Established 1988, pages 1413 to 1441

  By the way, in the conventional fixed-point blackbody furnace 200 described above, an inert gas is flowed from the closed portion side of the fixed-point crucible 204 to the measurement opening portion 202 side to prevent oxidation, but the structure through which the gas escape route is extremely narrow. Cause that the inert gas does not sufficiently reach the measurement opening 202 side of the fixed point crucible 204, and the measurement opening 202 side of the fixed point crucible 204, in particular, the reduced portion is deteriorated / damaged due to oxidation, thereby shortening the life. It was. Further, as the squeezed portion, not only the replacement at the time of deterioration or breakage due to oxidation, but also the squeezed size may be changed depending on the use conditions, and therefore a structure that can cope with these has been desired.

  Then, this invention is made | formed in view of the said problem, and it aims at providing the fixed point crucible and fixed point blackbody furnace which can extend a lifetime.

In order to achieve the above object, a fixed-point crucible described in claim 1 of the present invention has an outer cylinder for storing a fixed-point metal, a mortar-shaped closed portion at one end, and a phase equilibrium of the fixed-point metal at the other end. In a fixed point crucible having a measurement opening for measuring a temperature fixed point which is in a state and including an inner cylinder which is accommodated in the outer cylinder and becomes a black body cavity,
In part of the outer periphery at both end portions of the outer cylinder, a gas inflow portion is formed for flowing an inert gas from the closed portion side toward the measurement opening portion side ,
A protective member formed with a gas guide recess for guiding the inert gas flowing from the gas inflow portion into the measurement opening toward the center of the measurement opening is provided on the front surface of the measurement opening. It is characterized by having been arranged in .

Fixed point crucible according to claim 2 of the present invention, in the fixed point crucible of claim 1 Symbol placement,
A squeezing part having a squeezing hole having a diameter smaller than that of the measurement opening part is detachably provided on the inner cylinder.

A fixed-point blackbody furnace described in claim 3 of the present invention includes the fixed-point crucible of claim 1 or 2 .

  According to the present invention, since the gas inflow portion into which the inert gas flows from the closed portion side toward the measurement opening portion side is formed at a part of the outer periphery at both end portions of the outer cylinder, the inert gas is fixed to the crucible It can be fed to the measurement opening side, and the life of the fixed point crucible can be extended by suppressing the oxidation on the measurement opening side.

  In addition, a protective member formed with a gas guide recess for guiding the inert gas flowing from the gas inlet to the measurement opening toward the center of the measurement opening is disposed on the front of the measurement opening. By doing so, it is possible to allow the inert gas to sufficiently flow into the center of the measurement opening, and to further extend the life of the fixed point crucible.

  In addition, if an aperture with a smaller diameter hole than the measurement opening is provided in the inner cylinder so that it can be attached and detached, the optimum aperture can be used in response to deterioration or damage due to oxidation or changes in the size of the aperture. Can be replaced.

It is a front view of the temperature calibration apparatus which accommodated the fixed point blackbody furnace which concerns on this invention. It is side surface sectional drawing of the fixed point blackbody furnace in FIG. It is a sectional side view for demonstrating the schematic structure of an identification point blackbody furnace. (A) It is a sectional side view which shows the flow state of the heat carrier in the fixed point blackbody furnace which concerns on this invention. (B) It is an AA line side sectional view in (a). It is a schematic block diagram which shows the apparatus structure of the conventional blackbody furnace.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In addition, the present invention is not limited by this embodiment, and all other forms, examples, operation techniques, and the like that can be implemented by those skilled in the art based on this form are included in the scope of the present invention. .

  The fixed-point blackbody furnace of the present invention is provided in a temperature calibration apparatus that performs temperature calibration of a thermometer to be calibrated such as a radiation thermometer, and a desired fixed-point metal (In, Sn having a purity of 99.999% or more) is placed in a fixed-point crucible. , Zn, Al, Ag, or Cu), and when the plateau state is reached by the latent heat of the fixed point metal M that has been heated and lowered by the heater, the temperature fixed point is measured with a thermometer to be calibrated Calibration is performed.

  And in this embodiment, a pair of protective members centered on a fixed point crucible, and a pair of heat insulating materials are arranged in this order, accommodated in a soaking tube provided with a gas injection part, and further made of alumina that caps both ends of the soaking tube A fixed-point crucible unit provided with a holding part is provided in the fixed-point blackbody furnace, so that the fixed-point crucible can be replaced.

  In this specification, for the convenience of explaining the fixed-point blackbody furnace of this embodiment, when the fixed-point blackbody furnace is horizontally installed in the temperature calibration apparatus, various thermometers including a radiation thermometer that is a thermometer to be calibrated are used. The opening window side for measuring the black body cavity (that is, the position where the calibration thermometer is installed) is defined as the “front surface”, and the opposite side of this front surface side is inside the fixed point crucible unit housed in the furnace. The side on which an inert gas (Ar or the like) for preventing oxidation of the fixed point crucible is injected is defined as the “back surface”.

  As shown in FIG. 1 or FIG. 2, the fixed-point blackbody furnace 1 of the present example includes a fixed-point crucible unit 10 that houses a fixed-point crucible 11 that becomes a blackbody cavity, and a plurality of fixed-point crucible units 10 that are provided outside both end faces of the fixed-point crucible unit 10. And the cylindrical panel heater 30 in which each of the thermal insulation materials 20 is housed with the thermal insulation material 20 sandwiched between the fixed point crucible unit 10 and the thermal insulation material 20 at both ends of the fixed point crucible unit 10. It is configured to be housed in a cylindrical housing member 40 having an opening 41 in a sandwiched state. A receiving member 42 for collecting the fixed point metal M leaking from the fixed point crucible 11 is provided below the opening 41 in the housing member 40.

  And the fixed point blackbody furnace 1 is accommodated in the predetermined position in the outer housing | casing 51 of the temperature calibration apparatus 50, as shown in FIG. 1 or FIG. That is, the fixed-point blackbody furnace 1 has a temperature calibration device 50 having an opening window 51a for measuring radiant heat from a blackbody cavity in the furnace when the radiation thermometer 100 serving as a thermometer to be calibrated is calibrated. In the outer casing 51, the opening 41 is accommodated at a position that matches the center line of the opening window 51a.

  As described above, the fixed-point blackbody furnace 1 is accommodated in the outer casing 51 at a position where the opening 41 of the fixed-point blackbody furnace 1 is aligned with the center line of the opening window 51a. The center of the black body cavity of the fixed point crucible 11 and the center of the opening window 51a are aligned on a straight line. Therefore, when the radiation thermometer 100 is calibrated, the alignment of the radiation thermometer 100 can be easily performed by using the center line of the opening window 51a as a reference axis for measurement.

  Further, various displays for displaying temperature settings and furnace temperatures when the radiation thermometer 100 is calibrated are displayed at predetermined locations (for example, the front side of the outer casing 51) of the outer casing 51 of the temperature calibration device 50. A setting display unit (not shown) configured by a device (for example, a liquid crystal panel or LED), various setting buttons, or the like is provided.

  As shown in FIG. 3 and FIG. 4 (a), (b), the fixed point crucible unit 10 includes a fixed point crucible 11, a protective member 12, a unit heat insulating material 13, a heat equalizing tube 14, a gas injection part 15, It is comprised with the holding | suppressing part 16.

  The fixed point crucible 11 includes a cylindrical outer cylinder 11a and a cylindrical inner cylinder 11b accommodated in the outer cylinder 11a. The outer cylinder 11a is formed of high-purity graphite, a screw-type lid member 11c is provided on the back side, and the other end has an opening 11d for accommodating the inner cylinder 11b. The inner cylinder 11b is made of high-purity graphite, like the outer cylinder 11a, and has a closed mortar-shaped blocking portion 11e at one end and a measurement opening 11f for measuring a temperature fixed point at the other end. A black body cavity is formed.

  Moreover, the gas inflow part 11g is formed in the both ends of the outer cylinder 11a. As shown in FIGS. 4 (a) and 4 (b), the gas inflow portion 11g is formed from a notch portion in which the upper, lower, left, and right sides of the outer periphery at both ends of the outer cylinder 11a are linearly cut from the outer periphery by a predetermined depth. Become. The gas inflow portion 11g allows the inert gas injected from the gas injection portion 15 provided on the back side of the fixed point crucible 11 to flow in the direction from the back side to the front side along the outer peripheral surface of the fixed point crucible 11 (that is, the fixed point crucible). 11 in the inner cylinder 11b from the closed portion 11e toward the measurement opening 11f). As a result, the inert gas injected from the gas injection unit 15 flows from the back side to the front side along the length direction of the fixed crucible 11 as shown by the arrow in FIG. As a result, the inert gas is sufficiently fed into the front side of the fixed point crucible 11 (on the measurement opening 11f side), and the front side oxidation in the fixed point crucible 11 is suppressed.

  In the example of FIGS. 4A and 4B, the gas inflow portion 11g is a notched portion formed at both ends of the outer cylinder 11a, but is not limited thereto. That is, the gas inflow portion 11g may have a shape that can sufficiently allow the inert gas injected from the gas injection portion 15 to flow from the back side of the crucible 11 to the front side. Small-diameter through holes can be formed at a plurality of locations to form the gas inflow portion 11g.

  Furthermore, in the opening 11d of the inner cylinder 11b, the diameter of the measurement opening 11f can be arbitrarily adjusted according to the use conditions (for example, use temperature), so that the diameter of the aperture is smaller than that of the measurement opening 11f. A squeezed portion 11h in which is formed is detachably provided. With this detachable configuration of the squeezed portion 11h, when the size of the squeezed is changed due to deterioration / breakage due to oxidation or use conditions, the squeezed portion 11h can be appropriately replaced with the optimum squeezed size.

  The protection member 12 is composed of a pair of annular members of a front-side protection member 12a and a back-side protection member 12b made of high-purity graphite, like the fixed point crucible 11. The front side protection member 12 a is provided on the front side of the fixed point crucible 11 (that is, the measurement opening 11 f side of the inner cylinder 11 b in the fixed point crucible 11). The back side protection member 12b is provided on the back side of the fixed point crucible 11 (that is, the closed portion 11e side of the inner cylinder 11b in the fixed point crucible 11). That is, the protective member 12 is provided outside the fixed point crucible 11 at both ends in order to suppress oxidation of the fixed point crucible 11 due to outside air.

  In addition, a through-hole 12c for communicating with the measurement opening 11f of the inner cylinder 11b is formed in the front side protection member 12a. Furthermore, a gas guide recess 12d is formed in the through hole 12c of the front surface side protection member 12a so as to face the front surface of the measurement opening 11f of the inner cylinder 11b. The gas guide recess 12d has a curved shape with a predetermined curvature with the most concave position corresponding to the center of the measurement opening 11f of the inner cylinder 11b, and the inert gas flowing in from the gas inflow portion 11g is efficiently fixed at a fixed point. The crucible 11 is led toward the center on the front side (that is, the center of the measurement opening 11f of the inner cylinder 11b). Thereby, the oxidation of the measurement opening 11f of the fixed point crucible 11 is further suppressed, and the life of the fixed point crucible 11 is extended.

  In the example of FIG. 4B, the gas guide recess 12d has a curved shape with a predetermined curvature, but a recess shape (for example, a stepped recess, etc.) that allows the inert gas to sufficiently spread to the front side of the fixed crucible 11 is used. ).

  In addition, guide holes 12e are formed at a plurality of locations on the back side protection member 12b. The guide hole 12e guides the inert gas injected from the gas injection part 15 from the back side of the fixed crucible 11 toward the front side.

  The unit heat insulating material 13 is a heat insulating member in which ceramic fibers are hardened with an adhesive or the like, and includes a front side unit heat insulating material 13a and a back surface side heat insulating material 13b. In order to stabilize the temperature distribution of the fixed point crucible 11, the unit heat insulating material 13 is provided to face the outer end surfaces of the protective members 12 so as to face the both end surfaces of the fixed point crucible 11.

  And the through-hole 13c connected to the through-hole 12c of the front side protection member 12a is formed in the front side unit heat insulating material 13a. Further, the rear unit heat insulating material 13b is formed with a through hole 13d for guiding the inert gas injected from the gas injection part 15 to the rear surface protection member 12b.

  The soaking tube 14 is formed with a through hole 14a that communicates with the through hole 13c of the front side unit heat insulating material 13a and a through hole 14b that communicates with the gas injection part 15 and introduces an inert gas. The soaking tube 14 is formed of stainless steel when the fixed point metal M is any of In, Sn, Zn, and Al, and is formed of Inconel when the fixed point metal M is Ag or Cu metal. Use the same thing.

  The gas injection part 15 is a gas introduction pipe made of the same material as the soaking pipe 14 for injecting an inert gas from the back side of the fixed point crucible 11 (that is, the closed part 11e side of the inner cylinder 11b in the fixed point crucible 11), It is integrally formed on the back side of the soaking tube 14.

  In order to make it possible to replace the fixed point crucible 11 accommodated in the soaking tube 14, the holding unit 16 is not fixed to the soaking tube 14 by heating of the panel heater 30, for example, an alumina front side pressing unit 16a and a back side pressing unit 16b. It is composed of a pair of cap members. And the front side holding | suppressing part 16a is mounted | worn so that the front side of the heat equalizing tube 14 may be capped, and the through-hole 16c connected with the opening part 14a of the heat equalizing tube 14 is formed. Moreover, the back side holding | suppressing part 16b is mounted | worn so that the back side of the soaking | uniform-heating tube 14 may be capped, and the insertion hole 16d by which the gas injection part 15 integrally formed in the soaking | uniform-heating tube 14 is penetrated is formed.

  The heat insulating material 20 is a heat insulating member in which ceramic fibers are hardened with an adhesive or the like, and includes a front surface heat insulating material 21 and a back surface heat insulating material 22. The front-side heat insulating material 21 is divided into a plurality of pieces (three in the example of FIG. 3) and is provided on the front side of the fixed-point crucible unit 10 to form a through-hole 21a communicating with the measurement opening 11f of the fixed-point crucible unit 10. Has been. The through-hole 21a forms a part of the measurement cavity and is formed so as to gradually increase in diameter from the measurement opening 11f of the fixed crucible unit 10 toward the opening window 51a of the temperature calibration device 50.

  Further, in the through hole 21 a of the front surface heat insulating material 21, a recess 21 b for receiving a fixed point metal leaking from the fixed point crucible 11 is formed. The recesses 21b are formed at a plurality of locations in the length direction of the through holes 21a. Thereby, the fixed point metal M leaking from the fixed point crucible 11 is prevented from leaking outside from the opening window 51a of the temperature calibration device 50.

  The back-side heat insulating material 22 is provided on the back side of the fixed point crucible unit 10 and has an insertion hole 22a through which the gas injection part 15 is inserted. In addition, in this example, although the heat insulating material 20 is comprised by the two front side heat insulating materials 21 and the one back side heat insulating material 22, the number of the structures is not limited.

  The panel heater 30 includes a first heat insulating member 31 made of a ceramic fiber having a cylindrical shape (for example, Khao wool (registered trademark), which is an inorganic refractory fiber having a basic composition of alumina and silica), and an inner periphery of the heat insulating member. A heater 32 longer than the length of the heat equalizing tube 15 in the longitudinal direction is integrally formed on the surface, and a second heat insulating member 33 made of woven fabric made of glass fiber is wound around the outer periphery of the first heat insulating member 31. The panel heater 30 is accommodated in the accommodating member 40 in a state where the panel heater 30 is sandwiched between the front-side heat insulating material 21 and the back-side heat insulating material 22 with the fixed point crucible unit 10 as the center.

  Further, in the fixed point blackbody furnace 1 of this example, the through hole 12c of the front side protection member 12a, the through hole 13c of the front side unit heat insulating material 13a, the through hole 14a of the soaking tube 14, the through hole 16c of the pressing portion 16, the front surface It is formed so as to gradually increase in diameter toward the opening window 51a of the temperature calibration device 50 in the order of the through hole 21a of the side heat insulating material 21, and starts from the measurement opening 11f of the inner cylinder 11b in the fixed point crucible 11. The through holes 12a, 13c, 14a, 16c and 21a constitute a measurement cavity.

  When the radiation thermometer 100 as the thermometer to be calibrated is calibrated using the temperature calibration device 50 containing the fixed point blackbody furnace 1 having the above-described configuration, it is separated from the opening window 51a of the temperature calibration device 50 by a predetermined distance. The radiation thermometer 100 is installed at a position on the measurement axis, and the temperature calibration is performed by measuring the latent heat in the black body cavity of the fixed point crucible 11 through the measurement cavity.

  As described above, according to the fixed-point blackbody furnace 1 of the present example, the following effects can be obtained.

  The fixed-point blackbody furnace 1 of this example is sandwiched from the outside of both end faces of the fixed-point crucible 11 in the order of the pair of protective members 12 and the pair of heat insulating materials 13 in the soaking tube 14 around the fixed-point crucible 11. The pair of protective members 12 and the pair of heat insulating materials 13 are accommodated in alignment on the center line of the fixed point crucible 11, and the fixed point crucibles mounted so as to cap the pressing parts 16 made of alumina at both ends of the heat equalizing tube 14. Since the unit 10 is configured, the fixed point crucible 11 accommodated in the soaking tube 14 can be easily replaced without the pressing member 16 being fixed by the heating of the panel heater 30 accompanying the operation of the fixed point blackbody furnace 1. Can do. Moreover, it is not necessary to prepare the temperature calibration device 50 for each fixed point crucible 11 containing different types of fixed point metals M.

  Further, a heat insulating material 21 having a recess 21b for receiving the fixed point metal M leaking from the fixed point crucible 11 in the through hole 21a communicating with the measurement opening 11f of the fixed point crucible 11 is arranged on the front side of the measurement opening 11f. Due to the construction, the molten fixed point metal M leaking from the fixed point crucible 11 is received at a position close to the measurement opening 11 f side in the fixed point blackbody furnace 1, and the fixed point metal M is removed from the fixed point blackbody furnace 1 outside the temperature calibration device 50. Can be prevented from leaking. And since the fixed-point metal M is received by the recessed part 21b of the heat insulating material 21 which is a component of the fixed-point blackbody furnace 1, a part for receiving the fixed-point metal M does not protrude outside the temperature calibration device 50, and the appearance is improved. It doesn't impair the appearance of.

  Furthermore, since the diameter of the through hole 21a of the heat insulating material 21 is increased as the distance from the measurement opening 11f of the fixed point crucible 11 increases, the fixed point metal M leaking from the fixed point crucible 11 does not return to the measurement opening 11f side. Can be guided to the side and received.

  Moreover, since it is the structure which has the recessed part 21b in the multiple places of the length direction of the through-hole 21a of the heat insulating material 21, more molten fixed point metals M can be received by the recessed part 21b. Then, due to a synergistic effect with the structure in which the diameter of the through hole 21a of the heat insulating material 21 is increased as the distance from the measurement opening 11f of the fixed point crucible 11 is increased, the molten fixed point metal M leaking from the fixed point crucible 11 is measured. Can be received step by step from a position close to.

  Furthermore, since the gas inflow part 11g which inflows an inert gas toward the measurement opening part 11f side from the closed part 11e side of the fixed point crucible 11 is formed in a part of the outer periphery at both ends of the outer cylinder 11a, it is inactive. The gas can be sent to the measurement opening 11f side of the fixed point crucible 11, and the life of the fixed point crucible 11 can be extended by suppressing oxidation on the measurement opening 11f side.

  Further, the front side protection member in which the gas guide recess 12d for guiding the inert gas flowing into the measurement opening 11f from the gas inflow portion 11g of the fixed point crucible 11 toward the center of the measurement opening 11f is formed. Since 12a is arranged in front of the measurement opening 11f, the inert gas can be sufficiently introduced to the center of the measurement opening 11f, and the life of the fixed crucible 11 can be further extended.

  Furthermore, since the narrowed portion 11h having a smaller diameter hole than the measurement opening portion 11f of the fixed point crucible 11 is detachably provided in the opening portion 11d of the inner cylinder 11b, the size and size of the shrinkage can be reduced or deteriorated due to oxidation. Corresponding to the change, it can be replaced with the optimum head portion 11f.

DESCRIPTION OF SYMBOLS 1 ... Fixed point blackbody furnace 10 ... Fixed point crucible unit 11 ... Fixed point crucible (11a ... Outer cylinder, 11b ... Inner cylinder, 11c ... Cover member, 11d ... Opening part, 11e ... Closure part, 11f ... Opening part for measurement, 11g ... Gas inflow part, 11h ... squeezing part)
12 ... Protection member (12a ... Front side protection member, 12b ... Back side protection member, 12c ... Through hole, 12d ... Gas guide recess, 12e ... Guide hole)
13 ... Unit insulation (13a ... Front side unit insulation, 13b ... Back side unit insulation, 13c, 13d ... Through hole)
14 ... Soaking tube (14a, 14b ... through hole)
DESCRIPTION OF SYMBOLS 15 ... Gas injection part 16 ... Holding part (16a ... Front side pressing part, 16b ... Back side pressing part, 16c ... Through-hole, 16d ... Insertion hole)
20 ... heat insulating material 21 ... front side heat insulating material (21a ... through hole, 21b ... concave)
22 ... Back side insulation (22a ... Insertion hole)
30 ... Panel heater (31 ... 1st heat insulation member, 32 ... Heater, 33 ... 2nd heat insulation member)
DESCRIPTION OF SYMBOLS 40 ... Housing member 41 ... Opening part 42 ... Receiving member 50 ... Temperature calibration apparatus 51 ... Outer housing | casing (51a ... Opening window)
100 ... Radiation thermometer

Claims (3)

An outer cylinder for storing a fixed-point metal, a mortar-shaped closed portion at one end, and a measurement opening for measuring a temperature fixed point which is a phase equilibrium state of the fixed-point metal at the other end; In a fixed point crucible including an inner cylinder that is housed in a black body cavity,
In part of the outer periphery at both end portions of the outer cylinder, a gas inflow portion is formed for flowing an inert gas from the closed portion side toward the measurement opening portion side ,
A protective member formed with a gas guide recess for guiding the inert gas flowing from the gas inflow portion into the measurement opening toward the center of the measurement opening is provided on the front surface of the measurement opening. Fixed point crucible characterized by being placed in . 2. The fixed point crucible according to claim 1, wherein a narrowed portion having a narrowed hole having a diameter smaller than that of the measurement opening is detachably attached to the inner cylinder . A fixed-point blackbody furnace comprising the fixed-point crucible according to claim 1 or 2.

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