excimer lamp

Abstract

[The technical problem to be solved] In excimer lamps with an auxiliary discharge space for lighting and starting, lighting start-up performance and ultraviolet emission efficiency are improved. Technical means to solve the problem The discharge capacitor 15 forms a main discharge space S1 by fusing the end 20T of the outer tube 20 to the expanded diameter portion 31 of the large diameter portion 34 where the dielectric 30 is provided. Furthermore, an auxiliary discharge space S2 is formed along the lamp axis C by partially sealing the dielectric 30 and the inner electrode 40. Moreover, in the auxiliary discharge space S2, the distance D1 between the electrode and the dielectric 30 along the electrode width direction (Y direction) is smaller than the thickness (wall thickness) T10 (=T20) of the tubular portion 30G of the dielectric 30.

Description

Excimer lamp The present invention relates to an excimer lamp, and more particularly to an excimer lamp having an auxiliary discharge space. In an excimer lamp, a discharge gas is enclosed in a discharge space formed between a dielectric covering an inner electrode and an outer tube. Further, by applying a high-frequency voltage to the two electrodes, discharge and light emission are caused. In order to improve the lighting startability, an excimer lamp having an auxiliary discharge space is well known (see Patent Document 1). Here, a main discharge space is formed between a dielectric (inner tube) covering a foil-shaped inner electrode and an outer tube having an outer electrode provided on its outer surface, and a discharge space for assisting lighting start is formed between the inner electrode and the dielectric. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2022-182685 [Problems to be Solved by the Invention] In the auxiliary discharge space, when the distance intervals between both ends in the electrode width direction along the foil-shaped electrode and the inner surface of the dielectric surrounding the auxiliary discharge space are large, the lighting start voltage becomes high. Further, since the voltage applied to the auxiliary discharge space becomes high, the power consumed by the auxiliary discharge also becomes high, reducing the ultraviolet radiation efficiency of the main discharge. Therefore, in an excimer lamp having an auxiliary discharge space for lighting start, it is necessary to improve the lighting startability and the ultraviolet radiation efficiency. [Means for Solving the Problems] The excimer lamp of the present invention includes a dielectric covering a foil-shaped inner electrode arranged along the lamp axis direction; and a discharge container welded to the dielectric to form a main discharge space. The shape of the inner electrode is diverse. For example, the inner electrode can be configured such that the thicknesses at both ends in the width direction are thinner than the thickness at the central portion of the inner electrode. Further, the discharge container can also be configured as a tubular discharge container. The dielectric has, along the lamp axis direction, a sealing portion that seals the inner electrode, and a tubular portion that surrounds an auxiliary discharge space formed between the sealing portions. For example, a tubular portion can be formed in a partial section of the main discharge space along the lamp axis direction to include the central portion of the discharge container. In the present invention, in the auxiliary discharge space, the distance separating the widthwise ends of the inner electrode from the inner surface of the tubular portion is less than the thickness of the tubular portion along the widthwise direction of the inner electrode. Alternatively, the widthwise ends of the inner electrode contact the inner surface of the tubular portion. For example, the two widthwise ends of the inner electrode may be configured to be spaced apart from the inner surface of the tubular portion by a distance less than the thickness of the tubular portion along the widthwise direction of the electrode. Further, the distance by which one end of the inner electrode in the widthwise direction is spaced apart from the inner surface of the tubular portion is less than the thickness of the tubular portion in the widthwise direction of the electrode, and the other end of the inner electrode in the widthwise direction and the inner surface of the tubular portion may be configured to contact the inner surface of the tubular portion. The cross-sectional shape of the auxiliary discharge space follows the cross-sectional shape of the tubular portion, and considering the characteristics (including thickness, width, etc.) of the cross-sectional shape of the tubular portion, it can be determined from various variations so that the auxiliary discharge space has a desired cross-sectional shape. For example, in the auxiliary discharge space, the distance along the thickness direction of the electrode between the center in the widthwise direction of the inner electrode and the inner surface of the tubular portion may be configured to be greater than the thickness of the tubular portion. Regarding the cross-sectional shapes of the dielectric sealing portion and the tubular portion, they can be determined according to various cross-sectional variations along the lamp axis direction. For example, in the main discharge space, the diameter of the dielectric along the widthwise direction of the electrode may be substantially equal between the tubular portion and the sealing portion. Further, in the main discharge space, the distance along the widthwise direction of the electrode between the dielectric and the inner surface of the discharge vessel may be substantially equal between the tubular portion and the sealing portion. As the cross-sectional shape of the dielectric providing the above configuration, for example, the sealing portion may have an oval or oblong cross-section, and the tubular portion may have a hollow circular cross-section. The cross-sectional shape of the inner electrode can be determined according to the cross-sectional shape of the above dielectric. For example, the inner electrode may be configured to have a flat portion with a uniform thickness along the widthwise direction between the two widthwise ends, and become a sharp wedge shape between the widthwise ends and the flat portion. [Effects of the Invention] According to the present invention, in an excimer lamp having an auxiliary discharge space for assisting in lighting start-up, the lighting start-up property and the ultraviolet light emission efficiency can be improved. The excimer lamp of this embodiment will be described below with reference to the drawings. FIG. 1 is a cross-sectional schematic view of the excimer lamp of this embodiment. FIG. 2 is a cross-sectional schematic view of the excimer lamp along a direction perpendicular to the cross-sectional direction of FIG. 1. FIG. 3 is a cross-sectional schematic view of the excimer lamp along the III-III of FIG. 1. FIG. 4 is a cross-sectional schematic view of the excimer lamp along the IV-IV of FIG. 1. The excimer lamp 10 has a discharge vessel 15 made of a dielectric material such as quartz glass. The discharge vessel 15, which is a discharge tube (hereinafter referred to as the outer tube) 20 here, is formed by coaxially arranging the discharge tube 20 relative to the dielectric 30 and fusing it with the enlarged diameter portion 31 provided in the large diameter portion 34 of the dielectric 30. The outer tube 20, here, has a hollow circular cross-section in the tube diameter (lamp diameter) direction, and a cylindrical discharge space (hereinafter referred to as the main discharge space) S1 is formed between the outer tube 20 and the dielectric 30. In the main discharge space S, a rare gas such as xenon or a mixed gas thereof is enclosed as the discharge gas. The electrode covered by the dielectric 30 (hereinafter referred to as the inner electrode) 40 is a foil-shaped electrode extending along the tube axis (hereinafter also referred to as the lamp axis) C here. The inner electrode 40 is not exposed in the main discharge space S, and one end portion 40T along the lamp axis C direction is connected to the power supply rod (power supply wire) 70. The power supply rod 70 is connected to a power supply unit (not shown) provided outside. The electrode (hereinafter referred to as the outer electrode) 50 provided outside the discharge vessel 15 is a linear electrode portion made of a conductive metal here, and is arranged by winding around the outer surface of the outer tube 20 so as to be spirally wound along the lamp axis C and separated at a specified interval. The foil-shaped inner electrode 40 is coaxially arranged, and its center positions in the width direction and the thickness direction are aligned with the center position of the dielectric 30. In addition, the dielectric 30 is coaxially arranged relative to the outer tube 20. Therefore, the inner electrode 40 is arranged at a coaxial position opposite to the outer tube 20 and is symmetrically arranged with respect to the tube axis (lamp axis) C. Here, the width direction of the inner electrode 40 is set as the Y direction, and the direction perpendicular to it (thickness direction) is set as the X direction (refer to FIGS. 3 and 4). FIG. 1 shows a cross-sectional view along the electrode width direction of the foil-shaped inner electrode 40; FIG. 2 shows a cross-sectional view along the electrode thickness direction. In the discharge vessel 15, a main discharge space S1 and an auxiliary discharge space S2 formed along the lamp axis C direction are formed. Here, the auxiliary discharge space S2 is formed in a partial interval (hereinafter referred to as the auxiliary discharge space formation interval) CL including the lamp central portion in the electrode facing interval BL along the tube axis (lamp axis) C direction; in the electrode arrangement interval BL, the inner electrode 40 and the outer electrode 50 face each other in the tube diameter (lamp diameter) direction. The inner electrode 40 and the outer electrode 50 are an anode and a cathode in terms of polarity here. Moreover, a high frequency (for example, in the range of several kHz to several tens of MHz) and a high voltage (for example, in the range of several kV to more than ten kV) are supplied to the excimer lamp 10 through the power supply rod 70. Thereby, a dielectric barrier discharge is generated in the main discharge space S1, and excimer light of a predetermined spectrum (for example, wavelength 172 nm) is emitted from the main discharge space S1. The auxiliary discharge space S2 is in a reduced pressure state below atmospheric pressure, or is filled with a noble gas below atmospheric pressure that reduces the voltage at the time of lighting start-up. Therefore, when a high-frequency voltage is applied to the inner electrode 40 and the outer electrode 50, discharge first occurs in the auxiliary discharge space S2 through a lighting start-up voltage lower than that of the main discharge space S1. As shown in FIG. 3, in the portion outside the auxiliary discharge space formation section CL, the dielectric 30 is tightly attached (sealed) around the entire periphery of the inner electrode 40. On the other hand, in the auxiliary discharge space formation section CL, the dielectric 30 does not contact the inner electrode 40 except near both ends (see FIG. 4). In the manufacturing process of the lamp, by using a glass tube made of a material of the dielectric (inner tube) that allows the light (electromagnetic wave) emitted by the discharge formed in the auxiliary discharge space to penetrate, the entire circumference of the inner electrode 40 in the auxiliary discharge space formation section CL is not sealed, and the entire circumference of the inner electrode 40 is partially sealed along the lamp axis direction, thereby forming the auxiliary discharge space S2. The cross-sectional shape of the dielectric 30 in the auxiliary discharge space formation section CL is different from that in the portion outside it. As shown in FIG. 3, in the portion (hereinafter referred to as the sealed portion) 30F where the dielectric 30 is sealed with the inner electrode 40, its cross-section is an oblong or oval shape with different outer diameters in the electrode width direction and the electrode thickness direction. In other words, along the foil-shaped inner electrode 40, there is a surface portion in the electrode width direction (Y direction), and curved surface portions with a semi-elliptical or semi-circular cross-section are formed on both sides thereof, becoming a flat shape with respect to the electrode thickness direction (X direction). On the other hand, in the auxiliary discharge space formation section CL, the dielectric 30 is arranged as a tubular portion 30G (see FIG. 4). The tubular portion 30G is not a flat shape with respect to the electrode width direction (Y direction) and the electrode thickness direction (X direction), and its cross-section is formed as a hollow circle (ring shape). Therefore, in the auxiliary discharge space formation section CL, the distance interval D10 along the electrode width direction (Y direction) shown in FIG. 1 and the distance interval D20 along the electrode thickness direction (X direction) shown in FIG. 2 are approximately equal. Near both ends of the auxiliary discharge space formation section CL, that is, at the boundary portion between the sealed portion 30F and the tubular portion 30F of the dielectric 30, the cross-sectional shape of the dielectric 30 gradually becomes flat as shown in FIG. 3 and has a complex curved surface shape as shown in FIG. 4. As shown in FIG. 2, the inner surface 30H of the tubular portion 30G of the dielectric 30 expands in diameter away from the inner electrode at a sealing angle θ1, θ2 along the cross-section in the electrode thickness direction from near its root. Here, the sealing angles θ1, θ2 are set to be approximately in the range of 15° to 80°. FIG. 5 is an enlarged cross-sectional view of the dielectric and the inner electrode of FIG. 3. FIG. 6 is an enlarged cross-sectional view of the dielectric and the inner electrode of FIG. 4. The inner electrode 40, as shown in FIGS. 5 and 6, has a wedge-shaped portion 44 that tapers at the tip near the wide-direction ends E1 and E2 along the electrode width direction (Y direction), and a flat portion 42 with a constant thickness therebetween. However, it may also be a knife-edge shape that smoothly slopes from the center to the width-direction ends E1 and E2 along the electrode width direction. In addition, the inner electrode 40 may be configured to have a constant thickness along the electrode width direction. In this embodiment, in the auxiliary discharge space S2, two ends along the width direction of the inner electrode 40 (hereinafter referred to as the two width-direction ends) E1 and E2 are close to the inner surface 30H of the tubular portion 30G of the dielectric 30. In other words, the inner electrode 40 extends along the electrode width direction (Y direction) until near the inner surface 30H of the tubular portion 30G. Moreover, along the electrode width direction (Y direction), the distance interval (hereinafter referred to as the interval distance) D1 between the two width-direction ends E1 and E2 of the inner electrode 40 and the inner surface 30H of the tubular portion 30G is set to be shorter than the thickness T10 (=T20) of the tubular portion 30G (D1 < T10). In other words, the interval distance D1 is shorter than the wall thickness of the tubular portion 30G. In addition, in the auxiliary discharge space formation section CL, the interval distance D1 is shorter than the distance interval D10 between the outer surface of the tubular portion 30G and the inner surface 20H of the outer tube 20 in the main discharge space S1. Therefore, in the high-frequency voltage applied between the inner electrode and the outer electrode, the voltage applied between the interval distances D10 in the main discharge space S1 becomes more dominant than the voltage applied between the interval distances D1 in the auxiliary discharge space S2. Since power is supplied to the main discharge rather than the auxiliary discharge, the lighting startability and the ultraviolet irradiation efficiency can be improved. In the discharge vessel 15, the main discharge space S1 is formed as the dominant discharge space, and the auxiliary discharge space S2 is formed along the lamp axis C direction as the discharge space for forming a slight auxiliary discharge. In addition, as shown in FIGS. 5 and 6, in the cross-section along the electrode width direction of the dielectric 30, between the tubular portion 30G and the sealing portion 30F, their widths (outer diameters) are approximately equal (W10 ≒ W11), and there is no substantial difference in the outer diameter of the entire electrode arrangement section BL. Therefore, in the main discharge space S1, the interval distance D10 along the outer surface of the tubular portion 30G and the inner surface 20H of the outer tube 20 in the electrode width direction, and the interval distance D11 along the outer surface of the sealing portion 30F and the inner surface 20H of the outer tube 20 in the electrode width direction become almost constant in the entire electrode arrangement section BL along the lamp axis C direction, and a stable discharge state can be maintained. By forming the auxiliary discharge space S2, electrode wear of the inner electrode 40 can be suppressed. That is, the inner electrode 40 has pointed wedge-shaped portions 44 at both ends E1 and E2 in the width direction, whereby electric field concentration occurs at the time of lighting start-up. Further, by forming the auxiliary discharge space S2, discharge first occurs in the auxiliary discharge space S2, and then discharge occurs in the main discharge space S1. During the lamp lighting period, since the electric field intensity is strong near both ends E1 and E2 in the width direction of the inner electrode 40, both ends E1 and E2 in the width direction of the inner electrode 40 are liable to be worn due to the sputtering phenomenon. In particular, when the inner electrode 40 has a blade-edge shape that smoothly inclines from the center toward both ends E1 and E2 in the electrode width direction, since there are many portions with a relatively small thickness, the electrode is very liable to be worn due to the sputtering phenomenon. However, the inner electrode 40 has a flat portion 42 with a uniform thickness in the electrode width direction at the center between the width direction end E1 and the width direction end E2 along the electrode width direction (Y direction). Since the pointed wedge-shaped portions 44 are provided, the portions with a relatively small size are reduced, so that electrode wear in a short time can be suppressed. Therefore, it is possible to suppress the shielding of light (electromagnetic wave) including ultraviolet rays emitted to the main discharge space S1, and it is possible to use the auxiliary discharge for a long time to perform lamp lighting with high lighting start-up performance. In addition, as described above, since the interval distance in the electrode width direction (Y direction) along the main discharge space S1 is also substantially constant (D10 = D11) in the direction along the lamp axis C, the discharge state of the main discharge space S1 in the electrode width direction (Y direction) has no difference along the lamp axis C. Therefore, a stable discharge state can be maintained over the entire electrode arrangement section BL. As described above, in the sealing portion 30F, the dielectric 30 extends along the lamp axis C and has a flat oval or elliptical cross section in the electrode thickness direction (X direction). As shown in FIG. 5, the dielectric 30 is composed of a planar portion 32M whose cross-sectional contour line extends in the electrode width direction (Y direction) and is planar, and a curved surface portion 32E whose cross-sectional contour line is semi-elliptical or semi-circular. Since the dielectric 30 has a flat shape in the sealing portion 30F, the width (outer diameter) W21 (see FIG. 5) of the sealing portion 30F in the electrode thickness direction is smaller than the width (outer diameter) of the tubular portion 30G in the electrode thickness direction. On the other hand, the thickness T21 (see FIG. 5) of the sealing portion 30F covering the inner electrode 40 is larger than the thickness (tube wall thickness) T20 (= T10) of the tubular portion 30G in the electrode thickness direction. Moreover, the distance D2 between the center in the width direction of the inner electrode 40 and the inner surface 30H of the tubular portion 30G along the electrode thickness direction (X direction) is set to be longer than the thickness T20 of the tubular portion 30G (D2 > T20). In other words, the distance D2 is longer than the wall thickness of the tubular portion 30G. Thus, with respect to the electrode thickness direction (X direction), the thickness of the tubular portion 30G is suppressed, and by increasing the distance D2 from the inner electrode 40, the volume of the auxiliary discharge space S2 along the electrode thickness direction (X direction) can be ensured. Therefore, at the time of lighting start, electric field concentration can surely occur at both ends E1 and E2 in the width direction of the inner electrode 40. In addition, since the inner surface area of the auxiliary discharge space S2 along the electrode thickness direction (X direction) is ensured, even if the electrode material evaporated from the inner electrode diffuses outward in the electrode thickness direction (X direction) of the inner surface 30H of the tubular portion 30G to form a shielding film, it is possible to suppress the shielding of the light (electromagnetic wave) including ultraviolet light radiated into the main discharge space S1 by the electrode material, and it is possible to light a lamp with high lighting startability using auxiliary discharge for a long time. The excimer lamp 10 according to the present embodiment described above has a discharge vessel 15. By sealing the end portion 20T of the outer tube 20 to the enlarged diameter portion 31 provided in the large diameter portion 34 of the dielectric 30, the main discharge space S1 is formed. In addition, by partially sealing the dielectric 30 and the inner electrode 40, the auxiliary discharge space S2 facing the inner surface 30H of the dielectric 30 is formed in the auxiliary discharge space formation section CL along the lamp axis C. Moreover, in the auxiliary discharge space S2, the distance D1 from the dielectric 30 along the electrode width direction (Y direction) is shorter than the thickness (wall thickness) T10 (= T20) of the tubular portion 30G of the dielectric 30, and the distance D2 from the dielectric 30 along the electrode thickness direction (X direction) is longer than the thickness T10 (= T20) of the tubular portion 30G D. For example, when the excimer lamp 10 is a small excimer lamp, the size (diameter size) of the discharge vessel 15 is limited. When attempting to ensure the space of the main discharge space S1, for the dielectric 30 covering the inner electrode 40, while completely covering the foil-shaped inner electrode 40 extending in the electrode width direction (Y direction), it is necessary to confirm that the diameter size is suppressed as much as possible. Even under such limitations, a good lighting start auxiliary function can be obtained while suppressing the electrode wear of the inner electrode 40. In addition, since there is no difference in the deviation of the electric field strength along the electrode width direction (Y direction) along the lamp axis C, discharge occurs stably along the lamp axis C at the time of lighting start. Such an excimer lamp 10 can be manufactured, for example, by the manufacturing method described below. A dielectric 30 that is transparent to the light emitted from the discharge formed in the auxiliary space is used to form a glass tube (inner tube) with a cylindrical cross-section. The glass tube includes a small-diameter portion that covers the inner electrode (foil electrode) and a large-diameter portion that covers the power supply rod. After forming the glass tube, the power supply rod is connected to the inner electrode by impedance welding (resistance welding), and the inner electrode and the power supply rod are inserted into the bottomed cylindrical glass tube. After inserting the inner electrode and the power supply rod, the pressure (vacuum) inside the glass tube is reduced and sealed. At this time, the rare gas can be sealed inside the glass tube under a pressure lower than atmospheric pressure. While rotating the glass tube, heat it to deform the glass tube by softening and shrinking (reducing the diameter). At this time, only the two ends near the tube axis direction along the inner electrode are heated, and the range in the lamp axis direction corresponding to the auxiliary discharge space formation region is not heated, or by reducing the heating, the reduction in diameter caused by the softening of the glass tube is suppressed (stopped) to form an auxiliary discharge space. At this time, through heating adjustment, the volume of the auxiliary discharge space and the sealing angle θ between the inner surface of the glass tube and the inner electrode can be determined. An auxiliary discharge space is formed, and a cap-shaped enlarged diameter portion that protrudes in the diameter direction from one end of the glass tube is formed. In addition, without rotating the glass tube, only the portion of the glass tube corresponding to the edge of the foil electrode is heated and adhered along the axial direction. The end of the inner electrode in the length direction (tube axis direction) is buried in the glass tube by sealing the entire circumferential direction, and the end of the inner electrode is not exposed in the auxiliary discharge space. Regarding the outer tube, one end of a quartz tube that is transparent to the ultraviolet wavelength of the light emitted from the discharge forming the main discharge space is reduced in diameter, and an exhaust tube (wafer tube) with an opening is provided. On the other hand, an outer tube provided with an enlarged diameter portion and a welding insertion port of the inner tube is formed. Moreover, the inner tube is inserted into the outer tube and arranged coaxially, and the insertion port of the outer tube is heated and welded to the enlarged diameter portion to form a discharge tube. After that, the exhaust tube is used to evacuate to remove impurities, the discharge gas is sealed into the light-emitting tube, and the exhaust tube is hermetically sealed by heating and melting. After sealing, an outer electrode is provided on the outer surface of the outer tube. In this embodiment, although the width-direction ends E1 and E2 of the inner electrode 40 with sharp wedge-shaped edges are made to approach the inner surface 30H of the tubular portion 30G of the dielectric 30 to determine the interval distance D1, the width-direction ends E1 and E2 of the inner electrode 40 can also be made to contact the inner surface 30H of the tubular portion 30G. Alternatively, either one of the width-direction ends E1 and E2 of the inner electrode 40 can be made to approach the inner surface 30H of the tubular portion 30G of the dielectric 30 at an interval distance D1, and the other can be made to contact the inner surface 30H of the tubular portion 30G. The auxiliary discharge space formation section CL can be arbitrarily set within the range along the lamp axis C of the electrode arrangement section BL. For example, it can be specified that the auxiliary discharge space formation section CL includes the central portion of the lamp tube. Regarding the dielectric 30, it can be arranged with a circular cross-section throughout the electrode arrangement section BL. Alternatively, the tubular portion 30G can have an oval cross-section or an elliptical cross-section to match the flat shape of the sealing portion 30F of the dielectric 30. 10: Excimer lamp 15: Discharge vessel 20: Outer tube 20H: Inner surface of the outer tube 20T: End of the outer tube 30: Dielectric 30F: Sealing portion 30G: Tubular portion 30H: Inner surface of the tubular portion 31: Diameter-expanded portion 32E: Curved surface portion 32M: Planar portion 34: Large diameter portion 40: Inner electrode 40T: End of the inner electrode 50: Outer electrode 70: Power supply rod S1: Main discharge space S2: Auxiliary discharge space BL: Electrode arrangement section CL: Auxiliary discharge space formation section E1, E2: Wide-direction ends FIG. 1 is a schematic cross-sectional view of the excimer lamp of this embodiment. FIG. 2 is a schematic cross-sectional view of the excimer lamp along a direction perpendicular to the cross-sectional direction of FIG. 1. FIG. 3 is a schematic cross-sectional view of the excimer lamp along the III-III of FIG. 1. FIG. 4 is a schematic cross-sectional view of the excimer lamp along the IV-IV of FIG. 1. FIG. 5 is an enlarged cross-sectional view of the dielectric and the inner electrode of FIG. 3. FIG. 6 is an enlarged cross-sectional view of the dielectric and the inner electrode of FIG. 4. 10: Excimer lamp 15: Discharge vessel 20: Outer tube 20H: Inner surface of the outer tube 20T: End of the outer tube 30: Dielectric 30F: Sealing portion 30G: Tubular portion 30H: Inner surface of the tubular portion 31: Diameter-expanded portion 34: Large diameter portion 40: Inner electrode 40T: End of the inner electrode 50: Outer electrode 70: Power supply rod S1: Main discharge space S2: Auxiliary discharge space BL: Electrode arrangement section CL: Auxiliary discharge space formation section E1, E2: Wide-direction ends

Claims

1. An excimer lamp, comprising a dielectric material covering a foil-shaped inner electrode disposed along the lamp axis; a discharge capacitor fused to the dielectric material to form a main discharge space; the dielectric material having, along the lamp axis, a sealing portion sealing the inner electrode and a tubular portion surrounding an auxiliary discharge space formed between the sealing portions; the tubular portion having a hollow circular cross-section; in the auxiliary discharge space, the spacing between the width end of the inner electrode and the inner surface of the tubular portion is less than the thickness of the tubular portion along the width end of the inner electrode, or the width end of the inner electrode is exposed in the auxiliary discharge space and in contact with the hollow circular inner surface of the tubular portion.

2. The excimer lamp of claim 1, wherein, in the aforementioned auxiliary discharge space, along the electrode thickness direction, the distance between the center of the width direction of the aforementioned inner electrode and the inner surface of the aforementioned tubular portion is greater than the thickness of the aforementioned tubular portion.

3. The excimer lamp of claim 1, wherein in the aforementioned main discharge space, the diameter of the aforementioned dielectric along the electrode width direction is substantially equal between the aforementioned tubular portion and the aforementioned sealed portion.

4. The excimer lamp of claim 1, wherein in the aforementioned main discharge space, the spacing between the inner surfaces of the aforementioned dielectric and the aforementioned discharge capacitor along the electrode width direction is substantially equal between the aforementioned tubular portion and the aforementioned sealed portion.

5. An excimer lamp as claimed in any of claims 1 to 4, wherein the cross-section of the aforementioned sealing portion is an elongated ellipse or an oblong shape.

6. The excimer lamp of any one of claims 1 to 4, wherein the thickness of the width-direction end of the aforementioned inner electrode is thinner than the central portion of the aforementioned inner electrode.

7. An excimer lamp as claimed in any one of claims 1 to 4, wherein the aforementioned inner electrode has a flat portion of uniform thickness along the width direction at its center, and a sharp wedge is formed between the aforementioned end in the width direction and the aforementioned flat portion.

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