JPS6034222B2 - metal vapor discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal vapor discharge lamp in which the electron emitting material (emitter) sealed in the arc tube is changed.

For example, metal halide lamps use thorium (Th) or thorium oxide (Tho2) as the emitter to facilitate starting from the time voltage is applied to the start-up.
The thorium is then mixed into or applied to the electrodes and sealed inside the arc tube, and the electrons generated by the Q decay of thorium are used as seeds to start the discharge.

That is, a conventional metal halide lamp, for example 400
The W-shaped one has thorium oxide coated on the electrode. It is known that thorium has a half-life T of 1.4×10 years, and the number of thorium atoms in thorium oxide 2 underground is approximately 4.54×1×9, which is the total number of thorium atoms. Since the decay constant is 1.6×10-18 sec-1, it is thought that about 72 pieces of thorium in 20 thorium oxides decay on average every second. 1 per Q particle
Assuming that 1 electrons are created, the initial number Q of thorium electrons per second in 9 of 20 will be approximately 72.

On the other hand, the average starting time y from when a voltage is applied to the lamp until it starts is the probabilistic average time when the initial electrons are emitted until the start of discharge. The initial number of electrons Q per second emitted from
and the probability P that one emitted electron starts a discharge, 7: Point...(1') is given.

Therefore, Q in 9 of 20 sodium oxide is 72
Since P is generally considered to be about 0.5, in this type of lamp, ↑=0.02 parent sand, and discharge starts instantly after voltage is applied.

On the other hand, in the case of lamps that do not use thorium at all, the only source that supplies the initial number of electrons per second, Q, is natural radiation such as cosmic rays, and the initial number of electrons per second, Q, is only generated once every few seconds, which is Q30.1. This results in a total of 722 existing sand.

In other words, the average starting time for lamps that do not use thorium is about 2 hours, which means that you have to wait about 2 hours after voltage is applied before starting. There is an approximately 5% chance that the engine will not start for more than a minute. moreover,
In particular, lamps with a high discharge starting voltage require a pulse voltage at the time of starting, and since such lamps have a probability P of starting discharge only while the pulse voltage is applied, thorium is not used in such lamps. For those that do not, the average is about P30.01, so ↑2100M
It will reach around 2 seconds, on average 2 powders after voltage application,
In some cases, discharge may not start for nearly an hour. In this way, the use of thorium facilitates the initiation of discharge and contributes to shortening the starting time, but as mentioned above, thorium has a relatively long half-life of 1.4 x 10 years; For example, even at the end of the lamp's life after 5 years, it is desirable to emit at least one electron during one cycle in order to promote reliable starting, so even after 5 years, the number of decays per second will be 50. ~6% or more is required, and therefore, when encapsulating in the form of thorium oxide, an amount of at least about 20 mg is required.

However, thorium reacts with the halogen of the metal halide sealed in the arc tube to form thorium halide, which emits light and suppresses the light emission of other highly efficient fillers. This causes the east to drop. Moreover, the thorium halide vapor causes an increase in lamp voltage during its life. In this way, thorium reacts with halogen and disappears during its life, so if you want to keep this type of lamp reliably and smoothly started even at the end of its life, say 1,000 lights, an even larger amount of oxidation is required. Although sodium is required, increasing the amount of thorium oxide has the problem of further decreasing the light output. For this reason, we focused on using a radioactive material as an emitter instead of thorium, which has a shorter half-life than thorium.

However, due to their short half-life, radioactive substances tend to have a negative effect on the human body, and require great care when handling them. In other words, if radioactive materials come into contact with the human body, they will cause radiation damage, and for this reason, it is necessary to treat them as sealed radiation sources that do not allow radioactive materials to scatter. This invention was made based on the above-mentioned circumstances, and its purpose is to provide high safety by sealing L radioactive material as a sealed radiation source in the arc tube, and to improve startability3. The present invention aims to provide a metal vapor discharge lamp.

In the present invention, sealing means that the radiation source does not peel off in a smear test, that is, when the radiation source is wiped with monkey paper and examined with a counter or the like to see if radiation is emitted from the surface of the paper, no radiation is detected. This means that it is not detected, and that radioactive substances do not migrate from the radiation source to the paper.

An embodiment of the present invention will be described below based on the drawings.

In the figure, 1 is the outer tube of the metal halide lamp.

A stem 2 is sealed at one end of the outer tube 1, and a base 3 is attached thereto. Reference numeral 4 denotes an arc tube made of quartz glass or the like, and is provided at the center of the outer tube 1 via a support 5.6.

Main electrodes 7 and 8 are attached within the arc tube 4, and an auxiliary starting electrode 9 is arranged adjacent to one of the main electrodes 7. The main electrode 7 is connected to one support 5,
This support 5 has an introduction wire 10 that is sealed through the stem 2.
It is connected to the base 3 through. The other main electrode 8 is I
It is connected to another lead-in wire 12 via a J-cord wire 11, and this lead-in wire 12 passes through the stem 2 and is connected to the eyelet terminal 3a of the base 3. Further, the auxiliary starting electrode 9 is connected to the lead-in line 12 via an auxiliary starting resistor 13 and a normally closed bimetal switch 14 as a thermally responsive switch. A glow lighting tube 18 is connected between the starting auxiliary resistor (or current limiting resistor) 13 and the support 5 to perform a pulse generation function.

The arc tube 4 is filled with mercury as a buffer metal, metal halides as luminescent metals such as scandium iodide (Scl) and sodium iodide (Nal), and krypton gas as a starting rare gas. be.

Also inside this arc tube 4 is a sealed source 1 of radioactive material.
5 is accommodated. As shown in FIG. 2, this sealed radiation source 15 has a radioactive substance 16 dispersed and sealed in a ceramic body 17. Such a sealed radiation source 15 is introduced through the exhaust pipe of the arc tube 4 before the exhaust pipe is sealed. Therefore, the radioactive substance sealed source 15 is formed smaller than the inner diameter of the exhaust pipe. The ceramic body 17 is made of nonmetallic oxides such as silicon oxide (Sj02), aluminum oxide (N203), sodium oxide (Na20), magnesium oxide (Mg0), aluminum oxide (technical circle), titanium oxide (Tj0), Metal oxides such as calcium (Ca○), metal carbides such as aluminum carbide (AI4C3), sodium carbide (Na2C2), calcium carbide (CaC2), aluminum nitride (NN), sodium nitride (Na3N), magnesium nitride (M&N2) Metal nitrides such as these can be used.

Further, it is desirable that the radioactive substance dispersed and sealed in such a ceramic body 17 has a relatively short half-life, and preferably has a half-life of 0.5 to 1 year. For example, carbon-14 (14C), sodium-22 (basic Na)
, Calcium 45 (45Ca), Iron 55 (fan Fe), Cobalt 60 (60Co), Nickel 63 (spotted Ni), Zinc 65 (65Zn), Manganese 54 (54Mn), Strontium 90 (9 ozr), Ruthenium 106 ( 106
Ru), silver 110 (110Ag), antimony 125 (
125Sb), cesium 134 (134Cs), cesium 137 (137Cs), barium 133 (133 mother)
, Cerium 144 (MCe), Promethium 147 (1
47Pm), europyram 154 (154Eu), europium 155 (155Eu), gold 195 (M5Au)
, thallium 2 and others (2MTI), actium 227 (2M
Ac), Americium 241 (241Am), Curium 242 (2nd birth Cm), Curium 244 (244Cm)
), californium 252 (252Cf), plexus 6210
(21oPb), radium-226 (already 6Ra), radium-228 (2 spots Ra), thorium-228 (22oPb), etc., is selected and adopted.

Furthermore, the radioactive substance 16 is sealed with the amount of radioactivity regulated to 100 microcuries or less per lamp. In a metal halide lamp having such a configuration, when a voltage is applied through a ballast (not shown), the bimetal switch 14 is closed, so that the bimetal switch 14, the starting auxiliary resistor 13, the glow tube 18 and Current flows and the glow lighting tube 18 operates.

When the bimetal contacts of the glow lamp tube 18 are turned on and off, a pulse voltage is generated by the choking coefficient of the ballast (not shown). Auxiliary discharge is started between one main electrode 7 and the starting auxiliary electrode 9. This auxiliary discharge develops into a main discharge between the main electrodes 7 and 8, and starts a main arc discharge. After starting, the metal halide sealed in the arc tube 4 evaporates and emits light. Further, as the metal halide evaporates, the arc tube voltage increases and the temperature of the arc tube 4 rises, so the bimetal switch 14 is opened in response to this heat. Therefore, when the lamp reaches stable lighting, no current flows through the auxiliary starting resistor 13, and the bimetal contact of the lighting tube 18 closes, so the auxiliary starting electrode 9 and the adjacent main electrode 7 are kept at the same potential, and both Since no potential is applied through the quartz arc tube during the process, problems such as recrystallization and cracks due to quartz ions do not occur.
However, since the above-mentioned lamp has a radioactive substance 16 sealed in the arc tube 4, the initial electrons that become the seeds of the discharge are emitted from the radioactive substance 16, so that it can be started quickly. The starting voltage is also lower.

That is, the initial electrons emitted from the radioactive substance 16 promote discharge, thereby improving the starting characteristics. Since the radioactive substance 16 is dispersed and sealed in the ceramic body 17, it does not easily peel off from the ceramic body 17 and does not come off in a so-called smear test, so there is no risk of it adhering to the human body, and it is difficult to handle. It is also safe. Particularly when it is enclosed in the arc tube 4, it can be formed smaller than the exhaust pipe of the arc tube 4, so it is easy to insert it into the arc tube 4. Note that when the sealed radiation source 15 is sealed through the exhaust pipe, it may be sealed either before or during the exhaust, and there is no waste that affects the exhaust process. Therefore, the half-life of the radioactive substance 16 is more than 0.3 days1
State the reason why it is less than 20 years old. Generally, the lifespan of metal vapor discharge lamps, including metal halide lamps, is about 1,000 lamps, and assuming that they are lit and used for about 5 hours a day, they need to operate normally for about 6 years.

From this, if a radioactive substance has a half-life of 0.3 days or more, after 6 years it will be (1'2)2 x 6 = (1/2) 1232.
Since it is 4×10-4, the attenuation of the radioactivity does not end completely, and the starting function can be maintained. On the other hand, if the radioactive substance has a half-life of less than 0.5 years, the decay will be rapid, and the decay will be completed during the life of the lamp, resulting in a significant drop in starting performance at the end of the life of the lamp. On the other hand, if the half-life is too long, it will take time for the radiation to decay, and less radiation will be emitted in a short period of time, resulting in poor starting performance. It becomes necessary to increase the release probability. However, if too much radioactive material is encapsulated, it will chemically react and cause problems such as luminescence. Desirably, the total number of atoms of the radioactive substance sealed must be kept to 10-3 times or less the total number of atoms evaporated when the luminescent metal sealed in the arc tube is evaporated, and this amount is It is less than 10-years long, and its half-life is approximately 1 year or less. Furthermore, in consideration of further safety of radioactive substances for humankind, it is desirable that the radioactive substances decay relatively quickly, and it is even more desirable that the radioactive substances have a half-life of about 0.5 to 10 years. Furthermore, even if radioactive materials are handled in the form of a sealed source, the law requires that the amount of radiation be less than 100 microcuries, so the amount of radioactivity per arc tube must be less than 100 microcuries. .

As mentioned above, assuming that at least one radiation is emitted during one cycle of the power supply at startup, 50 to 6 solid decays are required per second, and taking into account the safety factor, ion decay per second is required. Assuming that a solid decay is necessary, in the case of a radioactive element with a half-life of 0.8, it will require the decay of ION solids every second even after 6 years, which is the lamp life, and the amount of elements will decrease after 6 years. However, 2.3 x 1 element is required, and a total amount of about 1 x 1 and 3 elements is required at the time of initial packaging.Also, radioactive elements with a half-life of 1 year are required. In this case, in order to cause 100 decays per second after 6 years, the number of elements will be 4.5 x 1 and 4, and the number of elements will be 4.5 x 1 and 4 at the beginning of the enclosure. The number of these elements is higher than the conventional thorium2
The number of elements in 9 of 0 is 4.54xlol9 compared to 10-
The amount is reduced by 5 to 10-7 times, and this shows that the amount of the radioactive substance in the above example can be reduced. In addition, in the case of a 400W metal halide lamp, the total amount of Sc and Na iodides as luminescent metals is 3
Sc and N in this weight
The number of elements in a is approximately 1 pipidarah.

According to experiments by the present inventors, if the number of elements in the radioactive material is regulated to 103 or less relative to the number of elements in the luminescent metal, the chemical reaction of the radioactive element, that is, the formation of halides, can be ignored, resulting in blackening and light It is known that it is possible to reduce the decrease in
Therefore, if a radioactive element has a half-life of 0.3 mm or more and 1 mm or less, the amount of encapsulation is small, so that no reactants with halogen are produced. Note that as an example of a method for producing the sealed radiation source 15 by supporting the radioactive substance 16 on the ceramic body 17, the following method is possible.

That is, first, aluminum oxide (AI203), silicon oxide (Si02), and sodium oxide (Na203)
) are thoroughly mixed, molded and solidified at 2000°C to produce a ceramic body.

Here, if the mixed molecular ratio of these oxides is x:y:z, then the ceramic body is xA1203・ySi02・zNa
It is 203. Part or all of the Na atoms in the ceramic body are replaced with promethium (Pm) atoms by an ion exchange method. That is, the above ceramic body was immersed in ammonium chloride (NH4CI) solution to form XA12Q.
ySi02.z(NH4)20 and then xN203.ySi02.zH20 by deammonia treatment. Then hydrogen (H) and promethium are substituted to form XA12.
03.ySi02.zHPmO, and by finally sintering this at a temperature of 1200 qo, the desired radioactive element-sealed ceramic can be obtained. Next, specific examples of the present invention will be described.

[Example 1] A 400W arc tube made of quartz glass with a distance between electrodes of 42 willow and an inner diameter of 20 willow, mercury of 50 willow, scandium-sodium iodide of 30:9, and krypton gas of 8 Pr
r, and N20 formed by the ion replacement method.
3. Seal nine pieces of the radioactive element sealed source 50 of Sj02.Pm○.

The radiation dose of this sealed source is 25 microcuries. This lamp has a power supply voltage of 180V AC and a pulse voltage of 15V.
When 00V and a pulse width of 1 microsecond are applied, it starts up instantly. Lamps that do not contain the sealed source require an average of more than two minutes to start. [Example 2] In a 100W arc tube with a distance between electrodes of 12 degrees and an inner diameter of 10 degrees, 5 parts of mercury and 5 parts of scandium-sodium iodide were placed.
, argon gas 8 morr, AI203・Si02・P
The lamp containing a sealed radiation source 1 of m○ (0.5 microcuries) has a power supply voltage of 150 V AC and a pulse voltage of 5
It starts with a waiting time of 0 seconds by applying a pulse voltage of 00V and a pulse width of 0.5 microseconds.

Those that do not use a sealed source require an average of one cavity. [
Example 3 Silicon oxide (Si02), calcium oxide (Ca○),
Magnesium oxide (Mg○) powders are mixed and bonded to form a pellet-shaped ceramic body, and some of the calcium and magnesium ions are replaced with pine Na to disperse and seal 22Na in the ceramic body.

This ceramic sealed radiation source has an inter-electrode distance of 80 mm and an inner diameter of 29 mm.
Mercury, iodides of cerium (Ce), samarium (Sm), and sodium (Na) and argon gas of 5 orr are sealed in the IkW arc tube of the sail.

This lamp has a power supply voltage of 170V AC and a pulse voltage of 500V.
When started by applying a pulse voltage of V and a pulse width of 0.5 microseconds, it starts instantly. Lamps without the ceramic-sealed source require a maximum start-up time of 5 minutes, with an average of 2 sands. [Example 4] A trace amount of carbon (C) is mixed and melted in silicon oxide (Si02), that is, a quartz piece containing carbon is irradiated with a neutron source.

Silicon (Si) contains 92.24% 28Si, 4.67% phantom Si, and 3.10% 3oSi, which suppresses S
i and neutrons react to form 31Si. 31Si has a half-life of 2.6 hours and decays rapidly.

On the other hand, carbon (C) contains 1.11% 13C, which reacts with neutrons to become 14C, which has a half-life of 560th place, and undergoes electronic decay. Therefore, if a quartz piece containing carbon is irradiated with neutrons as described above, and then left to cool for about a week, 31Si, which has a short half-life, will decay and become almost undetectable, and only 14C electrons will be present. emits. One microcurie of the quartz piece thus obtained as a sealed source of radioactive material was placed in an IkW-type arc tube with an electrode distance of 8 m and an inner diameter of 2 m. It is sealed with 80 rr of Benning gas consisting of earth, scandium metal 2:9, and neon-krypton. This metal halide lamp has a power supply voltage of 160V AC and a pulse voltage of 50V.
It starts instantly with 0V and a pulse width of 1 microsecond. Lamps without quartz chips require an average of 25 seconds to start. The present invention is not limited to metal halide lamps, but can also be applied to high-pressure sodium lamps, high-pressure mercury lamps, poppy lamps, light lamps, and the like.

As explained above, according to the present invention, the radioactive material is sealed and dispersed in the ceramic body in the arc tube, so the radiation emitted from the radioactive material triggers the discharge and starts the arc tube. performance becomes extremely good. Moreover, since the radioactive material is dispersed and sealed in the ceramic body, it is easy to handle and there is no risk of it coming into contact with the human body, improving safety.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view of a metal halide lamp, and FIG. 2 is a perspective view of a sealed radioactive source. 1... Outer tube, 4... Arc tube, 7, 8...
・Main electrode, 15... sealed radiation source, 16... radioactive material, 17... ceramic body, 18...
・Light tube. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A metal vapor emitting device characterized in that a radioactive substance with a half-life of about 0.5 years or more and about 10^4 years or less is dispersed and sealed in a ceramic body, and the ceramic body is enclosed in an arc tube. electric light. 2. The metal vapor discharge lamp according to claim 1, wherein the ceramic body contains aluminum oxide as a main component. 3 As radioactive substances ^1^4C, ^2^2Na
, ^4^5Ca, ^5^5Fe, ^6^0Co, ^6^
3Ni, ^6^5Zn, ^5^4Mn, ^9^0Sr,
^1^0^6Ru, ^1^1^0Ag, ^1^2^5S
b, ^1^3^4Cs, ^1^3^7Cs, ^1^3^
3Ba, ^1^4^4Ce, ^1^4^7Pm, ^1^
5^4Eu,^1^5^5Eu,^1^9^5Au,^
2^0^4Tl, ^2^2^7Ac, ^2^4^1Am
,^2^4^2Cm,^2^4^4Cm,^2^5^2
Cf, ^2^1^0Pb,^2^2^6Ra,^2^2
The metal vapor discharge lamp according to claim 1, characterized in that at least one of ^8Ra and ^2^2^8Th is used.