JP2020053127A - Ultraviolet light radiation short arc type flash lamp - Google Patents

Abstract

To provide a short arc type flash lamp which is hard to be clouded in white or blackened and of which the lifetime is prolonged.SOLUTION: In a flash lamp 101, three trigger wires 109 are radially disposed at an interval of 120°. The multiple trigger wires are radially and uniformly disposed in an outer circumference of a bulb 7, such that multiple bent main discharges in the vicinity of an inner wall of a luminous tube along the trigger wires occur. Therefore, in comparison with the case of one bent main discharge in the vicinity of the inner wall of the luminous tube, the flash lamp is easily quickly shifted by the straight main discharge between tip ends of electrodes. Thus, even when emitting light about at 210 J, the flash lamp is hard to be clouded in white. When light is emitted with 3 Hz even about at 50 J, the electrodes are sputtered and blackening is easy to occur. The flash lamp is quickly shifted by the straight main discharge between the tip ends of electrodes, thereby suppressing the sputter.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a trigger wire type ultraviolet light emitting short arc type flash lamp, and more particularly to extending the life of a flash lamp.

  Patent Document 1 discloses a trigger probe type short arc flash lamp. The trigger probe is a starting electrode, and when a high voltage is applied, a preliminary discharge is performed. In this state, the energy stored in the capacitor is instantaneously supplied between the main electrodes to emit ultraviolet light.

  The short arc flash lamp of the trigger probe type has the following two problems. Since the starting electrode needs to be provided in the quartz glass arc tube in addition to the main electrode, the manufacturing process is complicated. Further, since the trigger probe is located between the main electrodes, it is necessary to avoid melting of the tip of the trigger probe in order to increase the output.

  Then, the inventor examined whether or not it is possible to perform preliminary light emission of the ultraviolet light emitting short arc type flash lamp by the trigger wire provided along the envelope.

JP 2016-152183 A

  However, when the pre-emission is performed by the trigger wire, when the output is increased, the pre-discharge along the tube wall may cause the envelope to become cloudy. Such cloudiness will reduce the life of the lamp. Further, when the light emission cycle is shortened, the sealing body may be blackened along the tube wall.

  An object of the present invention is to solve the above-mentioned problems and to provide a long-life ultraviolet light-emitting short-arc type flash lamp.

  1) An ultraviolet light-emitting short-arc flash lamp according to the present invention includes a sealed envelope, a rare gas enclosed in the envelope, a cathode and an anode disposed to face the interior of the envelope, An ultraviolet light-emitting short-arc flash lamp, comprising: a trigger wire for starting stretched between a cathode and an anode outside the body; and applying electric voltage charged to a capacitor by applying a high voltage to the trigger wire. A plurality of the trigger wires are radially arranged so that a starting discharge along the envelope occurs in a plurality of parallel paths. Therefore, the discharge along the trigger wire shifts faster due to the straight main discharge between the electrode tips. As a result, it is possible to supply an ultraviolet light emitting short arc type flash lamp having a longer life.

  2) In the ultraviolet light emitting short arc type flash lamp according to the present invention, the trigger wire is constituted by three or more wires. Thus, the discharge along the trigger wire transitions faster to a straight main discharge between the electrode tips.

  3) In the ultraviolet light emitting short arc type flash lamp according to the present invention, the number of the trigger wires is six or more. Therefore, the discharge along the trigger wire shifts faster due to the straight main discharge between the electrode tips.

  4) In the ultraviolet light emitting short arc type flash lamp according to the present invention, the energy per pulse for charging the capacitor is 50 J or more. Therefore, it is possible to provide a long-life, high-output ultraviolet light radiation short arc type flash lamp.

  5) In the ultraviolet light emitting short arc type flash lamp according to the present invention, the energy per pulse for charging the capacitor is 200 J or more. Therefore, it is possible to provide a long-life, high-output ultraviolet light radiation short arc type flash lamp.

  6) In the ultraviolet light emitting short arc type flash lamp according to the present invention, the charging voltage in the main discharge is 500 V or more, and the peak current is 3000 A or more. Therefore, it is possible to provide a long-life, high-output ultraviolet light radiation short arc type flash lamp.

1 is an external view of a short arc type flash lamp 1. FIG. FIG. 2 is a circuit diagram for lighting a short arc flash lamp 1. FIG. 3 is a diagram showing various parameters of the short arc type flash lamp 1. It is a figure which shows the electric current and optical waveform about Examples 1-3. It is a figure which shows the result of lighting property and cloudiness when changing parameter D and PL / V. FIG. 6 is a diagram showing the relationship between the results of FIG. 5 when the parameter D is plotted on the vertical axis and PL / V is plotted on the horizontal axis. FIG. 7 is a diagram illustrating conditions when a charging voltage is changed. FIG. 14 is a diagram showing a current / light waveform for Example 5. FIG. 14 is a diagram showing a current / light waveform for Example 6. It is an external view of the short arc type flash lamp from which a bulb shape differs. 1 is an external view of a short arc type flash lamp 101. FIG. 12A is a sectional view taken along line AA of FIG. FIG. 12B is a cross-sectional view when the number of trigger wires is six. It is a figure which shows the relationship between the number of shots and the radiation intensity maintenance rate when the number of trigger wires is changed. It is a figure which shows the relationship between a spectral distribution and radiation intensity when the number of trigger wires is changed. It is a figure which shows the photocurrent waveform at the time of the number of one and three trigger wires. It is a figure which shows the photocurrent waveform in case the number of trigger wires is three and six. It is a figure which shows the relationship between the number of shots and the radiation intensity maintenance rate when the number of trigger wires is changed. It is a figure which shows the relationship between a spectral distribution and radiation intensity when the number of trigger wires is changed. It is a figure which shows the photocurrent waveform at the time of the number of one and three trigger wires. It is a figure which shows the photocurrent waveform in case the number of trigger wires is three and six.

(1. Lamp structure)
FIG. 1 shows a short arc flash lamp 1 according to the present invention. The short arc type flash lamp 1 includes a bulb (sealing body) 7 made of transparent quartz glass and having a substantially elliptical shape, a cathode 3, an anode 5 opposed to the cathode 3, a trigger wire 9, and a base 11.

  The bulb 7 can be selected from transparent quartz glass having high heat resistance as appropriate. However, since the inside of the bulb is exposed to high-temperature plasma, it is desirable to use quartz glass having high heat resistance and high softening temperature. Xe is sealed in the valve 7 as an inert gas at a predetermined pressure.

  The respective lead rods of the cathode 3 and the anode 5 are hermetically sealed at both ends of the bulb by a step-sealing method.

  The tip shapes of the cathode 3 and the anode 5 are conical with sharp tips. This is to ensure that the plasma arc of the main discharge is accurately located at the center of the electrode. The tip angle was 132 degrees. This is to withstand a large current, and may be an obtuse angle of about 90 to 150 degrees.

  The trigger wire 9 is fixed by stretching a joint between the bulb 7 and the side tube so as to be in close contact with the outside of the quartz glass. The material of the trigger wire 9 is preferably a metal wire that does not easily oxidize and has high heat resistance and high conductivity. In the present embodiment, a nickel wire is used, but a nichrome wire or a Kanthal wire may be used.

(2. Lighting mechanism)
A lighting mechanism of the short arc type flash lamp 1 will be described. The short arc type flash lamp 1 is connected to a lighting device, and two circuits of a lamp lighting circuit 91 and a trigger circuit 93 are configured as shown in FIG.

  A predetermined voltage is applied to the lamp lighting circuit 91 from a DC high-voltage power supply, and the capacitor 98 is charged with energy. The trigger circuit 93 applies a high voltage to the trigger wire 97 stretched along the envelope outside the lamp by the trigger coil 95. As a result, the gas inside the short arc type flash lamp 1 is broken down, and a spark streamer is generated between the electrodes inside the short arc type flash lamp 1 along the trigger wire 97. When insulation breakdown occurs inside the short arc type flash lamp 1, the energy charged in the capacitor 98 is supplied to the short arc type flash lamp 1.

  When the charged energy is supplied to the capacitor 98, the main discharge is started, and electrons and ions increase with time. As a result, the plasma flow grows greatly, and the discharge current also increases rapidly. At this time, the electrode is also gradually heated under a certain condition, and the emission of thermoelectrons from the cathode tip and the emission of electrons from the cathode tip due to the photoelectric effect start, and at some point near the inner wall of the arc tube along the trigger wire 97. Is transformed into a straight main discharge between the electrode tips.

Here, the temperature of the plasma flow has a correlation with the discharge current, and when the discharge current exceeds 3000 A, the plasma temperature increases accordingly. The solid quartz glass evaporates as SiO ₂ (gas), SiO (gas), O (gas), and O ₂ (gas), and the various gas species that have evaporated recombine immediately upon exiting the high-temperature plasma region. SiO ₂ fine particles having a diameter of μm are generated and adhere to the inner wall of the quartz glass again. A large number of attached SiO ₂ fine particles scatter light. Further, the high-temperature plasma reduces the quartz glass as SiO ₂ → Si + O ₂ (2O) and lowers the transmittance in the UV region. As a result, the UV radiation intensity is reduced, and the life of the UV discharge lamp is shortened.

(3. About parameter Y = PLD / V)
The inventor has determined that Y is a certain range with respect to Y = (P · LD · / V) using discharge lamp dimensions (D), electrode spacing (L), charged gas pressure (P), and charging voltage (V) as variables. It was thought that the above problem could be avoided if it was within. The reason is as follows.

  The parameter PL / V has the following significance. According to Paschen's law, the discharge starting voltage in the discharge tube decreases as the product PL of the gas pressure P (Pa) and the distance L (cm) between the electrodes decreases, and increases as the product PL increases. If the discharge starting voltage is low, spontaneous ignition is liable to occur, while if the discharge starting voltage is high, non-lighting is liable to occur. Further, the lower the charging voltage is, the more difficult it is to discharge. Therefore, the value of parameter PL / V is a parameter indicating the likelihood of occurrence of main discharge.

  The distance D of the trigger wire discharge type short arc flash lamp is a parameter related to the ease of lighting and the cloudiness of the envelope. This is because, as described above, the light emission mechanism of the short-arc flash lamp of the trigger wire type is a spark streamer discharge path having a small electric resistance, that is, the trigger wire 97 that extends between the electrode side close to the trigger wire and the outside of the arc tube. This is because the curved main discharge near the inner wall of the arc tube along the line shifts to a straight main discharge between the electrode tips.

  Hereinafter, the relationship between the two will be described.

(4. Example)
(Example 1)
A hydrated synthetic quartz glass tube having an outer diameter of 11 mm and an inner diameter of 8 mm was swelled with a oxyhydrogen burner into an ellipsoid having a short axis of 11 mm and a long axis of 20 mm with a thickness of 1.5 mm to form a valve. The shapes of the cathode and the anode were cylindrical with a diameter of 6 mm and a length of 6 mm, and each tip was cut into a cone at an angle of 130 degrees. The anode material is 2% lanthanum oxide-doped tungsten, and the cathode is a pressed sintered electrode obtained by mixing Ba ₃ WO ₆ powder and tungsten powder, press-molding, and sintering at 2000 ° C. for 3 hours at a high temperature.

  A tungsten core wire having a diameter of 2 mm was press-fitted into both electrodes and joined. Step joining was performed with one glass.

  At this time, the distance L between the electrodes is 0.97 cm, and the dimension D of the discharge lamp is 0.95 cm. The filling gas is Xe, and the filling pressure is 59959 Pa. In this embodiment, Y = 55.3 under the condition of a charging voltage of 1000 V.

  FIG. 4A shows current / light waveforms for 1000 V-280 μF lighting of the first embodiment. The vertical axis in FIG. 4 represents the current value (kA), and the horizontal axis represents the elapsed time. According to the figure, the current and the optical output rise almost at the same time, a step in the optical waveform appears in about 5 μs (the current at this point is about 2000 A), and then rapidly rises again in about 3 μs. The discharge along the tube wall was about 1300 A, and no white turbidity was generated even with long-term operation at 1000 V-280 μF-1 Hz-10000 shots.

  As described above, the output value of the 254 nm light rises almost at the same time as the rise of the discharge current, and when the plasma curved along the trigger wire moves as straight plasma to both electrode tips during the time when the discharge current reaches the peak value. Then, a step occurs in the rising light output waveform, and after a time period of several microseconds, the light output starts to increase again. Such an optical output waveform preferably has a step at a low intensity. In this example, it can be said that the optical output waveform has good characteristics at 3000 A or less.

(Example 2)
Example 1 is the same as Example 1 except that the distance L between the electrodes is doubled (2.06 cm). In this embodiment, Y = 117.4 under the condition of a charging voltage of 1000 V.

  FIG. 4B shows a current / light waveform. It reached 8700 A in about 17 μs from the rise of the current and the light waveform, a step in the light waveform occurred, and then rapidly rose again in about 8 μs. The current corresponding to the change of the optical waveform reaches 3000 A after about 7 μs, but the time until 17 μs at which the step of the optical waveform occurs is as short as 10 μs, and the quartz glass is not heated to a temperature at which the quartz glass evaporates. No white turbidity was generated even with long-term lighting of 1000 V-280 μF-1 Hz-10000 shots.

  As described above, the output value of the 254 nm light rises almost at the same time as the rise of the discharge current, and when the plasma curved along the trigger wire moves as straight plasma to both electrode tips during the time when the discharge current reaches the peak value. It can be seen that a step occurs in the rising light output waveform, and the light output starts to increase again after a time period of several microseconds.

(Example 3)
Example 2 is the same as Example 1 except that the distance L between the electrodes was further increased (3.02 cm) and the sealing pressure P was further increased (73327 Pa).

  In the present embodiment, Y = 210.4 under the condition of a charging voltage of 1000 V. In this case, as shown in FIG. 4C, the optical waveform draws a gentle curve without any steps from the rising to the peak. It can be seen that the current reaches 3000 A 5 μs after the rise, gradually increases, passes through a peak current of about 10,000 A, turns down, and becomes less than 3000 A after about 40 μs. Also, it can be seen that discharge along the tube wall occurs for about 20 μs until the current value becomes 9200 A. In the lighting test at 1000 V-280 μF-1 Hz, cloudiness occurred at about 5000 shots.

  As described above, when the plasma does not shift from the tube wall to the tips of the two electrodes from the rising of the discharge current to the peak, the emission intensity has a gentle upwardly convex curved shape without a step.

  The measuring method in the present embodiment will be described. In the present embodiment, the discharge current waveform was measured using a Rogowski current meter (RCTi / 3000 / 2.5 / 300) manufactured by PEM. In addition, a bandpass filter that passes light of 254 nm manufactured by Asahi Spectroscopy was attached to the optical sensor DET10A manufactured by Thorlab, and the optical waveform was measured. As the light receiving intensity of the light waveform, a relative output value between an arbitrary position and light captured by the aperture may be adopted.

  At the time of measurement, a semiconductor for blocking a reverse current was inserted into the discharge circuit. As a result, the discharge current waveform becomes a gentle upward convex curve. On the other hand, the 254 nm light waveform has a unique waveform shape due to a curved discharge along the tube wall and a straight discharge between the electrode tips.

(Example 4)
Example 2 is the same as Example 1 except that the distance L between the electrodes is smaller than that of Example 1 (0.32 cm). In this case, since the distance between the electrodes is short, almost no discharge occurs along the tube wall, and the discharge becomes straight in a short time, so that there is almost no problem of cloudiness. However, the peak current value increases as the distance between the electrodes becomes shorter, so that if the charging voltage is high, the electrode tip may be melted. In the case of Example 4, when the charging voltage was 1000 V, Y = 18.2, and the tip of the electrode was dissolved. When the charging voltage was 800 V, Y = 22.8, and when the charging voltage was 600 V, Y = 30.4. In any case, the electrode tip did not dissolve.

(5. Parameter PLD / V)
The inventor conducted an additional experiment in order to investigate the effective range of the correlation between the discharge lamp dimension D and the parameter PL / V regarding the transparency and lighting properties.

  FIG. 5 shows the discharge lamp dimension D, the respective values when the parameter PL / V is sequentially changed, and the relationship between lighting properties and cloudiness in that case. FIG. 6 is a list of results when the respective data of FIG. 5 are arranged in a matrix.

  In FIG. 6, を indicates that the transparency is 80% or more, no spontaneous ignition and no non-lighting, Δ indicates that the transparency is 60 to 80%, almost no spontaneous ignition and almost no non-lighting, and 60% or less of transparency. , And spontaneous ignition and non-lighting were rated as x.

  The spontaneous ignition means that the discharge lamp is spontaneously discharged by charging the capacitor without applying a high voltage to the trigger.

  When the cloudiness of the inner wall of the arc tube progresses, the light is scattered, and the light amount of the photo sensor decreases.

  Transparency may be measured as “light amount after life / initial light amount × 100 (%)”. In the present embodiment, the amount of light after life was measured when lighting was performed at 200 W and lighting was performed for 10,000 shots at a power amount of 2 kWh.

  From FIG. 6, it can be seen that when the parameter PL / V on the horizontal axis increases, the discharge lamp dimension D on the vertical axis does not satisfy both the lighting properties and the prevention of white turbidity unless the discharge lamp dimension D decreases. Also, it can be seen that if the discharge lamp dimension D on the ordinate increases, the parameter PL / V on the abscissa does not decrease unless both the lighting properties and the prevention of white turbidity are satisfied. Therefore, it can be seen that if the product Y of the discharge lamp dimension D and the parameter PL / V is within a certain range, the above conflicting requirements are satisfied. In this example, 20 <Y <200.

  In the present embodiment, as the combination of the parameters PL / V, P = 100,000 Pa, L = 0.5 cm, P = 70,000 Pa, L = 1.0 cm, P = 40,000 Pa, L = 1.5 cm With respect to the three types, lighting experiments in which the charging voltage V was arbitrarily varied were performed.

  For example, in FIG. 5, when PL / V = 100 and D = 0.3, Y = 30, and the plasma constantly approached the tube wall and was discharged and became cloudy. When PL / V = 20 and D = 1, Y = 20, and spontaneous firing occurred frequently. In the case of PL / V = 60 and D = 1, Y = 60, and the transition to the discharge at the electrode tip was completed in a short time, and both the transparency and the lighting property were good. In the case of PL / V = 160 and D = 1, Y = 160, and the transparency was good at 80% or more, but rarely turned off. When PL / V = 100 and D = 2, Y = 200, and the lighting was frequently turned off. When PL / V = 20 and D = 2.8, Y = 56, and spontaneous firing occurred frequently.

  That is, only the range of the parameter Y does not satisfy the conditions satisfying both the transparency and the lighting property. The inventors have considered that there is an appropriate range for each of the parameters D, P, L, and V.

  The sealed gas pressure P (Pa) is preferably 20,000 <P <200,000 (Pa), and more preferably 40,000 <P <100,000. When the filling gas pressure P is 20,000 Pa or less, the discharge (spontaneous ignition) occurs only by charging the capacitor without applying a high voltage by a trigger, and the filling gas pressure P becomes 200,000 Pa or more. In this case, even if a high voltage is applied by a trigger, the light is not turned on.

  Further, the charging voltage V to the capacitor is preferably 300 <V <3,000 (V), and more preferably 500 <V <1,500. When the charging voltage V is 300 V or less, it becomes difficult to light even when the charged pressure is as low as 20,000 Pa. When the charging voltage V is 3,000 V or more, the cathode is heated by repeated lighting and spontaneously ignites. It is because you will be.

  The distance L (cm) between the electrodes is preferably 0.3 <L <5 (cm), and more preferably 0.3 <L <1.5. If the distance L between the electrodes is 0.3 cm or less, spontaneous ignition will occur even if the filled gas pressure P is as high as 200,000 Pa. If the distance L between the electrodes is 5 cm or more, the main discharge will follow the tube wall. This is because they do not shift to a straight discharge between the electrodes.

  The discharge lamp dimension D is preferably 0.3 <D <2 (cm), and more preferably 0.5 <D <1.5. When the discharge lamp dimension D is 0.3 cm or less, the tube wall is too close to the electrodes, and even if the main discharge moves between the electrodes, the tube walls are exposed to high-temperature plasma and become cloudy. On the other hand, if the dimension D of the discharge lamp is 2 cm or more, the electrode and the tube wall are too far apart, and the lamp does not light.

  As described above, when the parameters D, P, L, V and the parameter Y are in the above ranges, the main discharge starts in a curved plasma shape from both electrode sides through the spark streamer discharge path. When the plasma grows while being curved and the discharge current increases, the plasma shifts to a straight plasma shape from both electrode tips. Note that this transition may be performed by simultaneously measuring the discharge current waveform and the 254 nm emission waveform indirectly.

  The inventor has found that when the plasma current in the vicinity of quartz glass exceeds about 3000 A and the time of exposure to high-temperature plasma of 3000 A or more becomes 20 μsec or more, the quartz glass evaporates intensely, and the evaporated Si + O, SiO2 causes Thought cloudy. If the value of Y is within the above range, the transition occurs within 20 μs after reaching 3000 A, and as a result, the discharge lamp has a long life.

(6. Other embodiments)
The inventor further conducted an experiment in which the capacity of the capacitor and the charging voltage were changed.

First, experiments were performed on Examples 1 to 3 when the charging voltage was changed. The results are shown in FIG. 7A. Thus, it can be seen that there is no problem even if the charging voltage is changed as long as Y is within the range.

  Further, an experiment was performed in which the capacitance of the capacitor was changed. The results are shown in FIG. 7B. In Example 5, the distance L between the electrodes was 1.14 cm, and the dimension D of the discharge lamp was 0.87 cm. The filling gas is Xe, the filling pressure is 73327 Pa, the capacitor capacity is 420 μF, and the charging voltage is 600, 800 and 1000 (V). In this case, if the charging voltage is 1000 V, Y = 72.7, if the charging voltage is 800 V, Y = 90.9, and if the charging voltage is 600 V, Y = 121.2.

  FIG. 8 shows the measurement results of the fifth embodiment. Thus, the discharge along the tube wall is 3000 A or less, and the plasma is in contact with the tube wall for a short time, so that the life is long.

  Example 6 is slightly different from Example 5 in the distance L between the electrodes (1.17 cm). In this case, if the charging voltage is 1000 V, Y = 74.6, if the charging voltage is 800 V, Y = 93.3, and if the charging voltage is 600 V, Y = 124.4.

  In each case, no white turbidity was generated even with long-term lighting of 1 Hz to 10,000 shots. Also, there was no problem in lighting properties.

  FIG. 9 shows the measurement results of the sixth embodiment. As described above, since the time when the plasma is in contact with the tube wall is short, the life is long.

  Thus, it can be seen that the capacitance of the capacitor has little effect.

  In the present embodiment, the case where the elliptical valve is employed has been described. However, the bubble shape is not limited to this. For example, even if the most inflated portion of the bubble is a straight tube as shown in FIG. Alternatively, it may be constituted by a curve having a larger diameter.

  Further, as for the type of gas, the case where xenon is adopted has been described, but other inert gas may be used.

(7. Regarding the embodiment in which the number of trigger wires is changed)
7.1 Prevention of white turbidity Various experiments were conducted on the short arc type flash lamp in order to realize a lamp with a longer life. As a result, the inventor has found that by increasing the number of trigger wires, the cloudiness is less likely to occur even under severe lighting conditions.

  FIG. 11 shows a short arc flash lamp 101 according to a seventh embodiment. FIG. 12A shows an AA cross section of FIG. As described above, the short arc type flash lamp 101 has three trigger wires 109 radially connected in parallel at 120 degrees. By arranging a plurality of trigger wires radially and evenly on the outer periphery of the bulb 7, a plurality of curved main discharges near the inner wall of the arc tube along the trigger wires are generated. Therefore, compared with the case where the number of curved main discharges near the inner wall of the arc tube is one, the transition is quicker due to the straight main discharge between the electrode tips. Thereby, cloudiness is less likely to occur.

  Note that, as shown in FIG. 12B, six trigger wires 109 may be arranged in parallel at 60 degrees.

  This becomes more noticeable by increasing the number of trigger wires. For example, as will be described later, when six trigger wires are employed, there is almost no curved main discharge near the inner wall of the arc tube, and there is a transition to a straight main discharge between the electrode tips.

  An experiment was performed when the number of trigger wires was changed to one, three, or six. The conditions other than the number of trigger wires were as follows: the distance L between the electrodes was 1.14 cm, the discharge lamp dimension D was 0.87 cm, the filling gas was Xe, and the filling pressure was 73327 Pa (550 Torr). Lighting was performed in a lighting mode of 0.5 Hz with a charging voltage of 1000 V, a capacitor capacity of 420 μF, and an input energy per pulse of 210 J. In this lamp, Y = 72.7 under the condition of a charging voltage of 1000 V.

  In the case of the lamp having one trigger wire, the number of shots was slightly less than 1,000 shots, and cloudiness was generally observed. In the case of the three lamps, the clouding was slightly observed in about 4,000 shots. Furthermore, with the six lamps, there was almost no change from the initial state even at 24,000 shots.

  FIG. 13 shows changes in the long-term emission radiation intensity when the number of trigger wires is one, three, and six. In the case of a single trigger wire, in the entire wavelength region of 200 to 800 nm, the radiation intensity maintenance ratio is 76% at 1,000 shots, and the radiation intensity maintenance ratio is 65% at 2,000 shots. The radiant intensity maintenance ratio was 62% for shots and 43% for 2,000 shots.

  On the other hand, when the number of trigger wires is three, in the entire wavelength range of 200 to 800 nm, the radiation intensity maintenance ratio is 90% at 2,000 shots, and the radiation intensity maintenance ratio is 85% at 4,000 shots, In the wavelength range of 200 to 300 nm, the radiation intensity maintenance ratio was 78% at 2,000 shots and 63% at 4,000 shots.

  Further, when the number of trigger wires is 6, in the entire wavelength region of 200 to 800 nm, the radiation intensity maintenance ratio is 93% at 10,000 shots and 90% even at 24,000 shots. The radiation intensity maintenance rate was 90% at 10,000 shots, and 73% at 24,000 shots.

  FIG. 14 shows a comparison of spectral distributions. FIG. 14A is a comparison between the initial state and the state after 2,000 shots when the number of trigger wires is one. After 2,000 shots, the radiation intensity is generally ／ or less in the wavelength range of 200 to 300 nm.

On the other hand, as shown in FIG. 14B, when the number of trigger wires increases to three, even after 4,000 shots, the decrease in the radiation intensity in the wavelength range of 200 to 300 nm is small. Further, as shown in FIG. 14C, when the number of trigger wires is increased to six, even after 24,000 shots, the radiation intensity hardly decreases in the wavelength range of 200 to 300 nm.

When the input energy per pulse is repeatedly turned on at 210 J, the emission intensity is reduced in the spectral data in the entire wavelength region of 200 to 800 nm, particularly in the region of 200 to 300 nm. This is considered to be due to the fact that a structural defect of the glass was generated when the lamp was lit with high input energy and emitted ultraviolet light. When defects occur in the glass, the transmittance of the glass decreases particularly in the region of 200 to 300 nm. Further, SiO ₂ fine particles generated by the high-temperature plasma when the lamp is turned on adhere to the inner wall of the arc tube, causing cloudiness of the sealing body, and lowering the transmittance of quartz glass in the UV region. Due to these factors, the UV radiation intensity is particularly reduced in the entire wavelength range. From the graphs of FIGS. 13 and 14, it is understood that cloudiness is less likely to occur as the number of trigger wires increases.

  FIG. 15 shows a photocurrent waveform when the number of trigger wires is changed to one and three (FIG. 15A shows a case of one wire, and FIG. 15B shows a case of three wires). Note that, in each case, the distance L between the electrodes is 1.87 cm, and the sealing pressure is 73327 Pa, except that it is the same as the sixth embodiment. In this lamp, Y = 119.3 under the condition of a charging voltage of 1000 V.

  As is clear from FIG. 15, when the number of the trigger wires is reduced from one to three, the step of the light waveform is generated at a low intensity, and the time during which the curved main discharge near the inner wall of the arc tube is generated becomes short. In the case of a single trigger wire, a step in the optical waveform occurs when the current waveform is around 7500 A, and the time required to reach 7500 A from 3000 A is about 8 μs. On the other hand, when there are three trigger wires, a step in the optical waveform occurs when the current waveform is around 6000 A, and the time required to reach 6000 A from 3000 A is about 5 μs. With three trigger wires, the time for plasma to grow along the inner wall of the arc tube is shorter and the temperature is lower, so that the trigger wire is not heated to the temperature at which the glass evaporates, and the progress of cloudiness is suppressed. Can be.

  FIG. 16 shows a photocurrent waveform when the number of trigger wires is changed from three to six (FIG. 16A shows a case where there are three, and FIG. 16B shows a case where there are six). In each case, the distance L between the electrodes is 1.14 cm, and the sealing pressure is 73327 Pa, except that it is the same as the sixth embodiment. In this lamp, Y = 72.7 under the condition of a charging voltage of 1000 V.

  As is clear from FIG. 16, when the number of the trigger wires is changed from three to six, the step of the optical waveform is generated at a low intensity, and the time during which the curved main discharge near the inner wall of the arc tube is generated is shortened. When there are three trigger wires, a step in the optical waveform occurs when the current waveform is around 5500 A, and the time required to reach 5500 A from 3000 A is about 4 μs. On the other hand, when there are six trigger wires, a step in the optical waveform occurs when the current waveform is around 4500 A, and the time required to reach 4500 A from 3000 A is about 2 μs. When the number of the trigger wires is six, the growth time of the plasma along the inner wall of the arc tube is shorter and the temperature is lower.

  In this way, by arranging a plurality of trigger wires radially, it is possible to suppress the high-temperature plasma from touching the tube wall and reduce the clouding.

7.2 Prevention of Blackening Next, a description will be given of a case where light emission conditions under which blackening easily occurs are set.

  The lamp in this experiment is the same as in the case of the above cloudiness, but the lighting conditions and the lighting mode are different as follows. In the present embodiment, lighting was performed in a lighting mode of 3 Hz with a charging voltage of 500 V, a capacitor capacity of 420 μF, and an input energy per pulse of 52.5 J.

  In the case of a lamp having one trigger wire, blackening was observed in 2,000 shots as a whole, and in the case of three lamps, blackening was observed in about 4,000 shots. Further, with the six lamps, there was almost no change from the initial state even after 30,000 shots.

  In general, the life of a flash lamp greatly depends on the input energy per pulse, and the life is determined to have reached the lamp life when the maintenance ratio falls below 50% in the radiation intensity change.

  FIG. 17 shows changes in the long-term lighting radiation intensity when the number of trigger wires is one, three, and six. In the case of a single trigger wire, in the entire wavelength region of 200 to 800 nm, the radiation intensity maintenance ratio was 77% at 2,000 shots, and the radiation intensity maintenance ratio was 60% at 4,000 shots.

  On the other hand, when the number of trigger wires is three, in the entire wavelength range of 200 to 800 nm, the radiation intensity maintenance ratio is 92% at 2,000 shots, the radiation intensity maintenance ratio is 84% at 4,000 shots, and the radiation intensity maintenance ratio is 6,000 at 6,000 shots. The radiation intensity maintenance ratio was 76%.

  When the number of trigger wires was 6, in the entire wavelength region of 200 to 800 nm, the radiation intensity retention rate was 95% for 10,000 shots, 77% for 50,000 shots, and 49% for 200,000 shots.

  FIG. 18 shows a comparison of the spectral distribution when the charging voltage is set to 600 V for the lamp used in the experiment of FIG. FIG. 18A is a comparison between the initial state and the state after 2,000 shots when the number of trigger wires is one. When the number of trigger wires is one, the emission intensity is considerably reduced over the entire wavelength range (200 to 800 nm) at 2,000 shots.

  FIG. 18B is a comparison between the initial state and the state after 6,000 shots when the number of trigger wires is three. In this case, it can be seen that the degree of reduction is almost the same as in FIG. 18A at 6,000 shots.

  As shown in FIG. 18C, when the number of trigger wires becomes six, even at the time of 40,000 shots, the radiation intensity is not lower than that at the time of 6,000 shots when three trigger wires are used, and three trigger wires are used. Is almost the same as in the case of 160,000 shots.

  When the input energy per pulse is 52.5 J and the lamp is repeatedly turned on at 3 Hz, it can be determined that the entire wavelength range of 200 to 800 nm is lowered due to abnormal discharge or blackening due to sputtering. From the graphs of FIGS. 17 and 18, it can be seen that as the number of trigger wires increases, blackening hardly occurs.

  FIG. 19 shows a comparison of the photocurrent waveforms when the number of trigger wires is changed to one and three (FIG. 19A shows the case of one wire and FIG. 19B shows the case of three wires). In each case, the distance L between the electrodes was 0.89 cm, the sealing pressure was 73327 Pa, and the capacitance of the capacitor was 280 μF. In this lamp, Y = 94.6 under the condition of a charging voltage of 600 V, and Y = 56.8 under the condition of a charging voltage of 1000 V.

  From FIG. 19, it can be said that when the number of trigger wires is three, the current changes from a curved main discharge along the tube wall to a straight main discharge between the electrodes at a lower current than that of one. The trigger wire is wound circumferentially at the rear end of the arc tube for fixing. However, since the distance between the rear end of the electrode and the trigger wire is short, abnormal discharge is likely to occur. The discharge between the electrode tips is at a distance from the arc tube, but the abnormal discharge from the rear end of the electrode is close to the arc tube. If the abnormal discharge occurs repeatedly, the wall of the tube is easily blackened. The occurrence of abnormal discharge can be suppressed by increasing the number of trigger wires and quickly shifting to discharge between the electrodes. As a result, it is less likely that the electrode constituent material is sputtered and adheres to the tube wall of the arc tube. Therefore, spatter on the electrode is reduced, and the occurrence of blackening can be suppressed.

  FIG. 20 shows a comparison of the photocurrent waveforms when the number of trigger wires is changed from three to six (FIG. 20A shows three cases and FIG. 20B shows six cases).

  Both are the same as the sixth embodiment except that the distance L between the electrodes is 1.14 cm. In this lamp, Y = 121.2 under the condition of a charging voltage of 600V.

  Also in this case, when the number of trigger wires is six, the step of the optical waveform is generated at a lower intensity than in the case of three trigger wires, and the time during which a curved main discharge near the inner wall of the arc tube is generated is shortened. When there are three trigger wires, a step in the optical waveform occurs near the current waveform of 2500 A, and when there are six trigger wires, a step occurs near 1500 A. Further, when the lamp is turned on under the condition that the input energy is low, the discharge along the tube wall occurs at 3000 A or less, and the temperature does not reach the temperature at which the glass evaporates. When the number of trigger wires is six rather than three, the time for plasma to grow along the tube wall is short, and the material constituting the electrode is less likely to be sputtered and adhered to the tube wall. be able to.

  In the present embodiment, the curved main discharge near the inner wall of the arc tube is quickly shifted by the straight main discharge between the electrode tips because the trigger wires are arranged radially and evenly. As a result, even when light is repeatedly emitted with a discharge energy of about 210 J, turbidity hardly occurs. In addition, even when the discharge energy is about 50 J or the light is repeatedly emitted at about 3 Hz, blackening is less likely to occur due to the quick transition due to the straight main discharge between the electrode tips.

  The inventor thought that the cause of the blackening was abnormal discharge, spatter, and evaporation of the electron-emitting substance. This will be described below.

  In order to fix the trigger wire, the trigger wire is wound circumferentially at the rear end of the arc tube. Here, since the distance between the rear end of the electrode and the trigger wire is short, abnormal discharge is likely to occur. Thereby, the tube wall at the arc tube end is blackened.

  In addition, since the flash lamp is turned on with a high repetition cycle and high input energy, the electron-emitting substance contained in the electrode evaporates and turns black. For example, as described above, when the discharge energy per pulse is higher than 200 J, and repeatedly turned on, the temperature rise of the electrode, lanthanum from the anode, Ba-emitter of the pressed sintered electrode from the cathode, etc. The substance evaporates and the tube wall near the electrode darkens.

  In addition, the cathode is sputtered and scattered by the material constituting the electrode due to the collision of cations when the discharge is generated.

  Thus, it was considered that the spatter was apt to occur due to abnormal discharge and emitter evaporation, and the tube wall near the electrode was blackened.

  Further, in the present embodiment, the case of one, three, and six was compared. However, if there are two or more, the transition can be made earlier due to a straight main discharge between the electrode tips.

  In this embodiment, the case where three and six trigger wires are provided is described, but the number is not limited to this.

  In the above embodiment, the experiment was performed under the condition of 20 <((P · L · D) / V) <200. However, even in the case where the range is exceeded, the number of trigger wires is increased radially. Needless to say, clouding and blackening can be effectively prevented.

1 Short-arc flash lamp 3 Cathode 5 Anode 7 Bulb 9 Trigger wire 109 Trigger wire

Claims (6)

Sealed envelope,
A rare gas enclosed in the envelope,
A cathode and an anode disposed opposite to each other inside the envelope,
Trigger wire for starting stretched between the negative anode outside the envelope,
An ultraviolet light radiating short arc type flash lamp which starts the electric energy charged in the capacitor by applying a high voltage to the trigger wire,
A plurality of the trigger wires are radially arranged such that a starting discharge along the envelope occurs in a plurality of parallel paths,
A short arc flash lamp that emits ultraviolet light. The ultraviolet light short arc flash lamp according to claim 1,
The trigger wire is composed of three or more wires,
A short arc flash lamp that emits ultraviolet light. The ultraviolet light short arc flash lamp according to claim 2,
The trigger wire is composed of six or more wires,
A short arc flash lamp that emits ultraviolet light. The ultraviolet light radiation short arc type flash lamp according to any one of claims 1 to 3,
The energy per pulse for charging the capacitor is 50 J or more;
A short arc type flash lamp characterized by the following. The ultraviolet light short arc type flash lamp according to claim 4,
The energy per pulse for charging the capacitor is 200 J or more;
A short arc type flash lamp characterized by the following. A short arc type flash lamp that emits ultraviolet light according to any one of claims 1 to 5,
Charge voltage in main discharge is 500 V or more, peak current is 3000 A or more,
A short arc type flash lamp characterized by the following.

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