JP7175109B2 - short arc discharge lamp - Google Patents

Description

The present invention relates to discharge lamps, and more particularly to electrode structures for short arc discharge lamps.

Short-arc discharge lamps, which are used as light sources for projectors and exposure equipment, place a pair of electrodes within the arc tube at a very short distance (for example, several millimeters), and have electrodes integrated with the arc tube at both ends of the arc tube. Connected sealing tubes are formed respectively. Mercury, halogen, and a rare gas are enclosed in the arc tube. Arc discharge is generated by applying a voltage to the electrode pair, and the pressure inside the arc tube becomes high (for example, 100 atmospheres or more). Light emitted from the discharge is guided in a predetermined direction.

A so-called coil melting electrode is generally used in such a short-arc discharge lamp. A coil fusion electrode is formed by winding a coil around an electrode core rod and heating and melting the electrode tip side with a laser or the like. The melted portion is formed in a bowl shape, hemispherical shape, or the like to constitute the tip of the electrode, while the unmelted coil portion is integrally formed with the tip.

In a discharge lamp, when arc discharge becomes unstable, arc discharge may occur in areas other than the tip of the electrode. In particular, immediately after lighting, the temperature of the electrode is low, there is little evaporation of the enclosed material, and the gas pressure inside the arc tube is low. An arc discharge occurs with the (coil portion) as a starting point.

When arc discharge occurs on the rear end side of the electrode, the origin of the arc discharge is close to the arc tube, which deforms the arc tube and causes devitrification. In order to prevent this, an electrode shape is known in which the entire surface of the rear end portion of the coil portion is rounded (see Patent Document 1). As a result, the arc discharge originating from the rear end of the electrode after the start of lighting is prevented from continuing, and the origin of the arc discharge is shifted toward the protrusion of the electrode tip.

JP-A-2004-362861

When arc discharge occurs near the electrode core rod, the arc discharge approaches the electrode core rod, or the arc discharge starting point moves to the electrode core rod or its vicinity, and the electrode core rod is consumed by the heat of the arc discharge. . Repeated lighting of the lamp may damage the electrode core rod.

Therefore, in the coil melting electrode, it is required to prevent the arc discharge from affecting the electrode core rod.

A short-arc discharge lamp of the present invention comprises an arc tube and a pair of electrodes facing each other inside the arc tube. The electrode has a melting front end portion whose diameter decreases toward the electrode front end side, a coil portion in which a plurality of coils are formed in layers around the electrode core rod on the electrode rear end side of the melting front end portion, and a A cover member is provided on the rear end side of the electrode and covers at least a portion of the electrode core rod over the entire circumferential direction. For example, 0.15 mg/mm ³ or more of mercury, a rare gas, and a range of 1×10 ⁻⁶ to 1×10 ⁻² μmol/mm ³ of halogen are enclosed in the arc tube, and the distance between the pair of electrodes is A spacing is defined to be 2 mm or less.

The cover member can be configured by a coil member, a tubular member, or the like. For example, the cover member is a coiled member, and the outer diameter of the coil wire of the cover member can be smaller than the outer diameter of the coil wire of the coil portion. The cover member can be configured to cover part or all of the electrode core rod along the axis of the electrode core rod. At the end of the coil portion, a flat surface having an edge portion as a boundary may be formed over the entire circumference of the electrode core rod.

The electrode rear end side end of the cover member can be configured to be embedded in the sealing tube. Further, it is also possible that the electrode tip end of the cover member is located closer to the electrode tip than the electrode rear end of the coil portion along the electrode axis. is configured to cover the In this case, the cover member may be integrally connected with the fusion tip.

On the other hand, it is also possible to configure so that the coil portion is in contact with the electrode core rod and the cover member is provided on the electrode rear end side from the coil portion. The electrode tip end of the cover member may be in contact with the electrode rear end of the coil, and the electrode tip end of the cover member and the electrode rear end of the coil are aligned in the axial direction of the electrode. may be separated by a predetermined distance along the . In this case, the predetermined distance should be half or less of the wire outer diameter of the coil that is in contact with the electrode core rod in the coil portion.

According to the present invention, stable arc discharge can be achieved in a short arc discharge lamp.

1 is a schematic configuration diagram of a short arc discharge lamp according to a first embodiment; FIG. It is a top view of an electrode. 3 is a cross-sectional view of the electrode of FIG. 2 along the electrode axis; FIG. FIG. 4 is a plan view of an electrode according to a second embodiment; 5 is a cross-sectional view along the electrode axis of the electrode of FIG. 4; FIG. FIG. 10 is a plan view of a modification of the electrode of the second embodiment; FIG. 10 is a plan view of an electrode according to a third embodiment; 8 is a cross-sectional view along the electrode axis of the electrode of FIG. 7; FIG. FIG. 9 is an enlarged view of a part of the electrode of FIG. 8; It is the figure which showed the modification of the electrode of 3rd Embodiment.

Embodiments of the present invention are described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a short arc discharge lamp according to the first embodiment.

A short arc discharge lamp (hereinafter referred to as a discharge lamp) 10 is a discharge lamp that can be used in an exposure apparatus or the like, and includes a substantially spherical arc tube 12 made of transparent quartz glass. A pair of electrodes 20 and 30 are arranged in the arc tube 12 so as to face each other with a predetermined distance (here, 2 mm or less). On both sides of the arc tube 12, sealing tubes 14A and 14B made of quartz glass are connected to the arc tube 12 and integrally formed.

A discharge space S in the arc tube 12 is filled with mercury, halogen, and a rare gas such as argon gas. Here, 0.15 mg/mm ³ or more of mercury, rare gas, and 1×10 ⁻⁶ to 1×10 ⁻² μmol/mm ³ of halogen are enclosed. Halogens are encapsulated as compounds with mercury and other substances.

The discharge lamp 10 is an AC lighting lamp supplied with a predetermined rated power (for example, 100 to 500 W) here, and when voltage is applied to a pair of electrodes 20 and 30, arc discharge occurs between the electrodes, Light is emitted to the outside of arc tube 12 and guided in a predetermined direction by a reflecting mirror (not shown). Since an alternating voltage is applied to the pair of electrodes 20, 30, the polarity (cathode, anode) alternates.

FIG. 2 is a plan view of the electrode 30. FIG. FIG. 3 is a cross-sectional view along the electrode axis of electrode 30 of FIG. The configuration of the electrode 30 will be described with reference to FIGS. Incidentally, the electrode 20 also has the same configuration.

The electrode 30 is formed by winding a coil around an electrode core rod 32 and melting the tip of the electrode (hereinafter referred to as a coil melting electrode). That is, by winding a coil around the electrode core rod 32 and then melting the electrode tip side by laser melting or the like, the external shape of the electrode 30 shown in FIG. 2 is formed. The electrode 30 is made of tungsten here including the electrode core rod 32 .

The electrode 30 includes a substantially hemispherical electrode tip portion (hereinafter referred to as a fused tip portion) 40 and an unfused coil portion 50 . The fusion front end 40 corresponds to a portion where the coil is melted, and the surface 40S of the fusion front end 40 is a smooth curved surface that tapers toward the tip of the electrode. Further, the melting tip portion 40 is integrated with the electrode core rod 32 by melting. A bowl-shaped protrusion 42 is formed at the end of the melting tip 40 to serve as a starting point for arc discharge.

As shown in FIG. 3 , the coil portion 50 is formed in layers by winding a plurality of coils around the electrode core rod 32 . The coil portion 50 here includes an inner coil layer 52 with a circular cross section in contact with the electrode core rod 32 and an outer coil layer 54 with a circular cross section located radially outside the electrode core rod 32 from the inner coil layer 52 . It consists of two layers. The inner coil layer 52 and the outer coil layer 54 are not welded together, and the outer diameter of the inner coil layer 52 is smaller than the outer coil layer 54 . However, the inner coil layer 52 and the outer coil layer 54 may have the same outer diameter.

The outer coil layer 54 has a cut surface 54S perpendicular to its coil axis. On the other hand, the end portion 52E of the inner coil layer 52 is partially cut (disconnected). Specifically, a flat end surface (flat surface, cut surface) 52S having an edge portion 52D as a boundary is formed along the direction perpendicular to the electrode axis X over the entire circumference. An end portion 52E of the inner coil layer 52 is located on the electrode rear side along the electrode axis X relative to an end portion 54E of the outer coil layer 54 .

By providing the cut surface (flat surface) 52S with the edge portion 52D, the end portion 52E of the inner coil layer 52 is not curved (tubular) as the end portion 54E of the outer coil layer 54 but is curved. and a flat surface (cut surface 52S). Since the edge portion 52D exists on the flat surface boundary, the curved surface portion and the cut surface 52S are not smooth (continuous). In addition, unlike the end 54E of the outer coil layer 54, the position of the end 52E of the inner coil layer 52 along the electrode axis X is substantially the same in the circumferential direction. Furthermore, by cutting the end portion 52E of the inner coil layer 52 along the entire circumference in the direction perpendicular to the electrode axis X, a part of the edge portion 52D always becomes an acute edge.

A part of the electrode core rod 32 is covered with a cover member 60 . The coil portion 50 is located radially outside the cover member 60 , and the electrode tip end portion 60E1 of the cover member 60 is integrally connected to the melting tip portion 40 . In addition, the cover member 60 extends along the electrode axis X from the melting tip portion 40 to the vicinity of the end portion 32E of the electrode core rod 32, and a part thereof including the electrode rear end side end portion 60E2 extends inside the sealing tube 14B. (see Figure 1). The cover member 60 covers the electrode core rod 32 over the entire circumferential direction and is in contact with the electrode core rod 32 .

The cover member 60 is configured by a coil having a circular cross section here, and has a coil shape wound while being in close contact with each other. Here, the outer diameter (wire outer diameter) of the coil cross section of the cover member 60 is smaller than the outer diameter (wire outer diameter) of the coil cross sections of the inner coil layer 52 and the outer coil layer 54 .

By applying an AC voltage to such electrodes 20 and 30, lighting is started as described below.

Immediately after lighting, the electrode temperature is low, the enclosed material evaporates little, and the gas pressure is low, so arc discharge occurs outside the protrusion 42 . The inner coil layer 52 differs from the outer coil layer 54 in that a cut surface 52S having an edge portion 52D is formed at an end portion 52E of the inner coil layer 52 . Therefore, the electric field concentrates on the edge portion 52D of the cut surface 52S, especially on the acute-angled portion of the edge portion 52D. As a result, arc discharge is inevitably generated starting from the end portion 52E (edge portion 52D) regardless of the presence or absence of minute projections due to laser melting of the coil portion 50. FIG.

As described above, since the inner coil layer 52 is not welded to the outer coil layer 54, they are not integrally connected and their surfaces are partially in contact with each other. Therefore, the heat of the inner coil layer 52 is less likely to propagate to the outer coil layer 54 . On the other hand, the inner coil layer 52 is welded to and integral with the fusion tip 40 . Therefore, heat from the inner coil layer 52 is more easily transferred to the fusion tip 40 than to the outer coil layer 54 .

When the discharge lamp 10 is arranged so that the lamp axis is horizontal, the electrode temperature immediately after the lamp is turned off is higher on the electrode upper side. On the other hand, since the cut surface 52S is formed over the entire circumferential direction, the arc is generated at the end 52E of the inner coil layer 52 regardless of the rotational position (position in the direction around the axis) when the discharge lamp 10 is installed. Discharge is reliably generated, and arc discharge is suppressed from being generated at the end portion 54E of the outer coil layer 54 and minute projections generated on the surface of the outer coil layer 54 by laser melting.

On the other hand, since the cover member 60 covers the electrode core rod 32 , the arc discharge generated at the end portion 52</b>E of the inner coil layer 52 does not come into contact with the electrode core rod 32 . In particular, even if the arc bright spot moves from the electrode radially outer end portion to the radially inner end portion of the flat cut surface 52S, the presence of the cover member 60 causes the arc discharge to come into contact with the electrode core rod 32 or cause the arc discharge to occur. is prevented from moving to the electrode core rod 32 . On the other hand, since the cover member 60 is wrapped in the coil portion 50, arc discharge does not occur at the tip of the cover member 60 on the electrode side.

Furthermore, since the electrode rear end portion 60E2 of the cover member 60 is embedded in the sealing tube 14B, arc discharge does not occur in the vicinity of the electrode rear end portion 60E2 of the cover member 60, thereby sealing. There is no fear of breakage of the tube 14B. In addition, since the coil cross-sectional outer diameter (wire outer diameter) of the cover member 60 is smaller than the coil cross-sectional outer diameter (wire outer diameter) of the coil portion 50, an increase in the volume of the entire electrode is suppressed, and the halogen cycle is less affected. does not occur. In addition, since the amount of thermal expansion of the cover member is also suppressed, the difference in thermal expansion between the electrode rear end side end portion 60E2 embedded in the sealing tube and the sealing tube is suppressed, and cracks are not generated in the sealing tube. There is no

From the above, the heat generated by the arc discharge generated at the cut surface 52S (edge portion 52D) of the end portion 52E of the inner coil layer 52 propagates not to the outer coil layer 54 but to the fusion front end portion 40, resulting in , the melt tip 40 is hotter than the outer coil layer 54 . Since arc discharge generally tends to occur (easily move) at high temperature locations, the starting point of the arc discharge generated at the end 52E of the inner coil layer 52 is the outer surface of the outer coil layer 54, that is, the side surface of the coil portion 50. It moves quickly to the melting tip 40 without moving to the bottom.

In this way, the arc discharge is first generated at the cut surface 52S of the inner coil layer 52, and the heat is propagated along the electrode core rod 32 through the inner coil layer 52 to the melting tip portion 40, whereby a rapid arc is generated. Discharge transfer can be performed. Also, since arc discharge does not occur from the side surface of the coil portion 50 toward the arc tube 12 and the electrode core rod 32, deformation and devitrification of the arc tube 12 and the electrode core rod 32 can be suppressed.

The electrode 30 described above can be manufactured by various manufacturing methods. For example, a coil serving as a cover member is press-fitted into the electrode core rod. At this time, spot welding is performed by sandwiching the entire coil between spot electrodes with respect to the electrode core rod. Next, the coiling (wound) inner coil layer having a cut surface formed in advance is press-fitted onto the electrode core rod, and then the outer coil layer is press-fitted. Then, by laser-melting the tip end of the electrode, an electrode composed of the melted tip and the coil portion is formed. In the sealing step, the coil is sealed so as to be embedded in the sealing tube. The cut surface can be formed by laser, grinding, or the like. By forming a flat cut surface on the coil portion, the edge portion is formed along the periphery of the electrode core rod without providing a special process.

As described above, according to the present embodiment, in the short arc discharge lamp 10 including the electrode 30 (electrode 20) including the melting tip portion 40 and the coil portion 50, the edge portion 52E of the inner coil layer 52 has an edge. A cut surface 52S is formed along the periphery of the electrode core rod 32 so that there is a . At the same time, a cover member 60 covering the electrode core rod 32 extends from the melting tip portion 40 to the sealing tube side, and the coil portion 50 is provided outside thereof.

The cut surface 52</b>S may not be entirely perpendicular to the electrode axis X, and may be formed along the circumferential direction around the electrode core rod 32 . Also, it may be a part of the circumference instead of the whole circumference. For example, when the electrode 30 is horizontally arranged, arc discharge is likely to occur on the upper side of the inner coil layer 52 . Therefore, by arranging the electrodes so that the cut surface 52S is formed over half of the circumferential direction and the cut surface 52S is located above the cut surface 52S, it can be reliably generated at the end 52E of the inner coil layer 52. Furthermore, if the state of the electrode arrangement and the location of the high temperature state can be grasped to some extent, it is also possible to form the cut surface in a smaller range along the circumferential direction, and the flat surface can be formed in the circumferential length of that range. good too. In addition, instead of forming the edge portion 52D on the entire boundary between the cut surface 52S and the curved surface portion, the edge portion may be formed so that the edge exists partially. By forming it, arc discharge can be more reliably generated at the end portion 52E.

The coil part 50 can be formed of a layered coil other than two layers. Alternatively, the electrode structure may be one in which the inner coil layer and the outer coil layer are not formed of separate coils, but a single coil is wound around the electrode core rod. Even in this case, while the innermost coil layer is integrally connected to the fusion tip side, the outer coil layer is connected through the fusion tip, so the fusion tip is heated first and arc discharge occurs. Move along the electrode core rod.

As for the cover member 60, instead of being a coil-shaped member along the electrode axis X, it is also possible to form rings densely arranged along the electrode axis direction, a tubular member, a foil member, or the like. . A member having an axial length that partially or wholly covers the electrode core rod on the rear end side of the electrode from the coil portion can be used.

Next, a short arc discharge lamp according to a second embodiment will be described with reference to FIGS. In the second embodiment, the coil portion is in contact with the electrode core rod, and the cover member is provided closer to the rear end of the electrode than the coil portion.

FIG. 4 is a plan view of the electrode of the second embodiment. 5 is a cross-sectional view of the electrode of FIG. 4 along the electrode axis.

The electrode 30 ′ includes a melting tip 40 and a coil portion 150 , and the coil portion 150 covers the electrode core rod 32 while being in contact with the electrode core rod 32 . A coiled cover member 160 covers the electrode core rod 32 . A portion of the cover member 160 is embedded in the sealing tube 14B, as in the first embodiment.

The electrode tip end portion 160E1 of the cover member 160 is separated from the cut surface 152S of the inner coil layer 152 of the coil portion 150 by a predetermined distance L along the electrode axis X. As shown in FIG. Here, the predetermined distance L is set to 1/2 or less of the coil cross-sectional outer diameter (wire outer diameter) K of the inner coil layer 152 . The arc discharge generated at the edge portion 152D of the cut surface (flat surface) 152S is generated in an arc (see R in FIG. 5). By setting the distance between the portion 160E1, that is, the distance at which the electrode core rod 32 is exposed to the discharge space S to be equal to or less than the predetermined distance L, the arc discharge is exposed to the discharge space S of the electrode core rod 32 by the cover member 60. contact with the contact portion), and wear of the electrode core rod 32 can be suppressed.

FIG. 6 is a plan view of a modification of the electrodes of the second embodiment. A cover member 160 ′ of the electrode 30 ′ is in contact with the cut surface 152</b>S of the coil portion 150 . This can more reliably prevent the arc from contacting the electrode core rod 32 . In addition, it is possible to suppress the movement of the arc from the radially outer end portion to the radially inner end portion of the cut surface 152S.

Any manufacturing method can be applied to the electrodes of the second embodiment, and the electrodes can be manufactured according to the manufacturing method described in the first embodiment.

Next, a third embodiment will be described with reference to FIGS. 7 and 8. FIG. In a third embodiment, the cover member is constructed by an annular member.

FIG. 7 is a plan view of the electrodes of the discharge lamp of the third embodiment. 8 is a cross-sectional view of the electrode of FIG. 7 along the electrode axis.

The electrode 30″ of the short arc discharge lamp comprises a melting tip 40 and a coil portion 150. The coil portion 150 is constructed in the same manner as in the second embodiment. is an annular member (hereinafter referred to as an annular member 260 ), which is in contact with the electrode core rod 32 and the coil portion 150 .

FIG. 9 is an enlarged view of a part of the electrodes in FIG. The annular member 260 is a ring-shaped member having a substantially circular cross section, and its cross-sectional outer diameter (wire outer diameter) W is larger than the coil cross-sectional outer diameter (wire outer diameter) W1 of the inner coil layer 152 . On the other hand, the ring cross-sectional outer diameter W of the annular member 260 is smaller than the maximum distance A between the electrode core rod 32 and the outer coil layer 154 along the electrode core rod radial direction. That is, the outer diameter of the annular member 260 is larger than the outer diameter of the inner coil layer 152 and smaller than the outer diameter of the outer coil layer. Annular member 260 contacts cut surface 152 S of inner coil layer 152 . The edge portion 152</b>D is exposed to the discharge space S by the annular member 260 contacting the inner coil layer 152 at the cut surface 152</b>S other than the radially outer edge portion 152</b>D. For example, the edge portion 152D can be exposed to the discharge space S by making the cross-sectional radius (line radius) T of the annular member smaller than the coil cross-sectional outer diameter W1 of the inner coil layer 152 as shown in FIG.

By providing such a ring-shaped annular member 260 , arc discharge is likely to occur at the edge portion 152</b>D of the radially outer portion of the inner coil layer 152 . The arc discharge generated at the edge portion 152D does not occur toward the sealing tube side or the electrode core rod side because the annular member 260 becomes an obstacle. Further, the contact between the annular member 260 and the cutting surface 152S suppresses arcing or movement to the radially inner edge portion 152D'. In addition, since the surface of the annular member 260, particularly the surface on the electrode tip side, is curved and does not form an edge portion or the like, the arc discharge does not move to the annular member, and is generated at the edge portion 152D. Since the arc discharge contacts (approaches) the surface of the annular member 260 on the electrode tip side, it is possible to suppress the wear of the annular member 260 due to the heat of the arc discharge.

The electrode 30″ described above can be manufactured by various manufacturing methods. For example, the inner coil and the outer coil are press-fitted, and the annular member 260 is press-fitted. Good, and melt the electrode tip.

FIG. 10 is a diagram showing a modification of the electrodes of the third embodiment. The cover member 260' has a flat end face 260'S perpendicular to the electrode axis X on the electrode rear end side. By providing such an end face 260'S, the volume of the annular member 260' is reduced, and the influence of the increase in volume on the discharge can be suppressed. Furthermore, by providing the flat end face 260'S so that the edge portion 260'D of the flat end face 260'S has an obtuse angle, the arc discharge is more reliably generated at the edge portion 152D' having an acute-angled portion. , arcing can be prevented from occurring on the flat end face 260'S.

Thus, according to the third embodiment, in a short arc discharge lamp comprising an electrode 30″ with a melting tip 40 and a coiled portion 150, an edge is present at the end 152E of the inner coil layer 152. A cut surface 152S is formed along the circumference of the electrode core rod 32 so as to cover the electrode core rod 32. At the same time, an annular cover member 260 covering the electrode core rod 32 is provided in contact with the cut surface 152S of the coil portion 150. ing.

The annular member 260 does not cover the surface of the electrode core rod 32 as much as possible like the cover member of the first and second embodiments, but is brought into contact with the cut surface 152S of the coil portion 150 so that the arc discharge can occur in the sealed tube. It is possible to prevent it from occurring toward the side or the electrode core rod side. Therefore, the annular member 260 need not have a large length in the axial direction of the electrode, and may have a cross-sectional outer diameter larger than the winding diameter of the inner coil layer.

The annular member does not need to cover the entire circumferential direction of the electrode core rod, and may be configured by an annular member having a partially notched C-shaped washer shape or the like. In addition, it is not necessary to provide flat surfaces at the ends of the coil portion.

REFERENCE SIGNS LIST 10 discharge lamp 20, 30 electrode 40 melting tip 50 coil portion 52 inner coil layer 52E end portion 52S cut surface (flat surface)
54 outer coil layer 60 cover member 150 coil portion 260 cover member (annular member)
260'S end face

Claims (8)

an arc tube;
a pair of electrodes arranged facing each other in the arc tube,
the electrode is
a melting front end portion whose diameter is reduced toward the tip end of the electrode;
a coil portion in which a plurality of coils are formed in layers around the electrode core rod on the electrode rear end side of the melting tip portion;
a cover member provided closer to the rear end of the electrode than the melting front end and covering at least a portion of the electrode core rod over the entire circumferential direction;
A short arc discharge lamp, wherein an electrode tip end of the cover member is located closer to the electrode tip than an electrode rear end of the coil portion along the electrode axis. 2. The short arc discharge lamp according to claim 1, wherein the electrode rear end portion of the cover member is embedded in the sealing tube. 3. A flat surface having an edge on a boundary with the coil curved surface portion is formed along at least a part of the entire circumferential direction of the electrode core rod at the end portion of the coil portion. 2. The short arc discharge lamp according to 1. 2. The short arc discharge lamp according to claim 1, wherein said coil portion covers said cover member. 5. The short arc discharge lamp of claim 1, wherein the cover member is integrally connected to the fusion tip. The short arc discharge according to any one of claims 1 to 5 , wherein the cover member is a coil-shaped member, and the outer diameter of the coil wire of the cover member is smaller than the outer diameter of the coil wire of the coil portion. lamp. an arc tube;
a pair of electrodes arranged facing each other in the arc tube,
the electrode is
a melting front end portion whose diameter is reduced toward the tip end of the electrode;
a coil portion in which a plurality of coils are formed in layers around the electrode core rod on the electrode rear end side of the melting tip portion;
a cover member provided closer to the rear end of the electrode than the melting front end and covering at least a portion of the electrode core rod over the entire circumferential direction;
A short arc discharge lamp, wherein a flat surface having an edge portion as a boundary is formed at an end portion of the coil portion over the entire circumference of the electrode core rod. Mercury at 0.15 mg/mm ³ or more, rare gas, and halogen in the range from 1×10 ⁻⁶ to 1×10 ⁻² μmol/mm ³ are enclosed in the arc tube,
8. The short arc discharge lamp according to claim 1 , wherein the distance between said pair of electrodes is 2 mm or less.

Images