DE1040687B - Electric high pressure gas discharge lamp - Google Patents

Description

GERMAN

They are electric high pressure gas discharge lamps became known with a filling made of krypton or xenon. These lamps, their internal pressure during operation usually several atmospheres, even over 20 atmospheres, have proven particularly useful when filled with xenon because of the excellent light color, which comes close to natural daylight, and because of the achievable high luminance introduced. Due to the high electrical conductivity of the noble gases with atomic weights over 39 in the conditions present in high pressure discharges and the resulting low voltage drop per unit length of the discharge arc can result in greater power consumption at these lamps for a given Arc length can only be achieved by relatively very high currents. So have z. B. those already in the trade xenon high pressure lamps for projection purposes with burning voltages between 20 and 25 volts Amperages from 45 to 80 amps.

The necessary high amperage with at the same time low voltage consumption has disadvantages insofar as than once the vacuum-tight power supply to the electrodes inside the lamp is difficult to establish are and become quite extensive and, on the other hand, that the additional devices are extensive and become expensive, since normal mains voltages of mostly 220 volts are generally assumed.

It has now become known that the excitation in a discharge lamp to emit radiation heavy noble gases add lighter gases with an atomic weight equal to or less than 21.

However, it has been avoided in particular here to add significant amounts of such gases because because of the higher thermal conductivity of the gases in question, such as helium or Hydrogen, had to fear that it would immediately have a significant adverse effect on the yield Radiation, especially visible radiation, should have. That is why you have the share these lighter gases are limited to 5%.

It has now been determined by extensive measurements that the radiation yield of the heavy Noble gases with the addition of lighter gases takes a surprisingly different course than previously assumed. This means that much higher proportions of lighter gases can be added without a noticeable one Deterioration of the radiation yield, in particular light yield, to have to accept, in such a way, that the increased proportion of the lighter gases now really results in a considerable increase in the voltage gradient. The electric high pressure gas discharge lamp according to the invention, which are excited to radiation heavy noble gases of atomic weight over 39 and besides others, as a result of larger electric high pressure gas discharge lamps

Applicant:

Patent Trust Company

for electric light bulbs m.b.H.,

Munich 2, Windenmacherstr. 6th

ig Dipl.-Ing. Dr. Arnold Bauer, Augsburg,

and Dr. Paul Schulz, Karlsruhe,
have been named as inventors

Excitation and ionization voltage, lighter gases of atomic weight that are not excited to form radiation contains below 21, is characterized according to the invention in that such is not excited to radiation Gases are added, whose cross sections against electrons in the speed range of 0.5 to 1.0 electron volts are at least twice as large as those excited to radiation heavier noble gases, with the proviso that the relative content of the lighter gases, measured by the partial pressure, is more than 5 to 20% of the content of the heavier noble gases excited to radiation. The cross-section of the added lighter gases considered here is primarily Line around the cross-section for momentum exchange, which is slightly smaller than the one discussed below "Cross-section according to Ramsauer" can, however, be replaced by this for estimations can.

It succeeds in this way, for example by adding helium with a partial pressure of up to 20% of the xenon pressure, the voltage gradient of a xenon high-pressure gas discharge lamp by up to 20% without any measurable reduction in light yield. Such a one Accordingly, the lamp has a noticeably higher voltage drop and, accordingly, the same Power consumption a significantly lower power consumption. This works in favor of the one hand Power supplies from and, on the other hand, also in favor of the necessary ballasts.

The high electrical conductivity of the xenon (or krypton or argon) high pressure column is now based

S09 657/201

on the fact that the electron mobility is extremely high at the temperatures occurring here. It is known that in xenon (or krypton or argon) high pressure plasma temperatures of around 6000 to 8000 ° C prevail. The relative velocities of noble gas ions and electrons have under these circumstances values that correspond approximately to an energy of 1 electron volt (corresponds to 1 electron volt a temperature of 7700 ° C). In this area, the effective cross-sections have the values given above Noble gases just pronounced minima (Ramsauer effect), so that from it a very high electron mobility and thus a high electrical conductivity results. For illustration are in Fig. 1 the known effective cross-sections according to Ramsauer as a function of the relative kinetic energy plotted in electron volts for xenon, krypton and argon. The narrow range of 0.5 to 1.0 electron volts, who is particularly interested in high pressure discharge lamps is particularly marked on the abscissa axis.

There are now other gases whose cross-sections in relation to electrons are in the speed range in question are large, e.g. B. the atomic cross-sections of mercury are many times larger, however, a noticeable addition of mercury would fundamentally change the discharge properties, since this has a lower excitation and ionization voltage than the above-mentioned noble gases and es thus immediately becomes the carrier of the optical and electrical processes in the plasma. But a gas is added with excitation and ionization voltages that are noticeably higher than those of xenon (or krypton or argon), these gases take part in the electrical and optical processes directly do not have a share and only influence the discharge insofar as they are due to their different effective cross-sections can change electron mobility and heat conduction. If you choose such in particular Gases with high excitation and ionization voltages, the cross-sections of which are in the speed range in question opposite to the electrons are large compared to those of the above-mentioned noble gases, the electron mobility is reduced and thus the voltage drop per unit length of the arc increases, d. H. ultimately with the same Amperage increases the specific power conversion.

Of the permanent gases, helium and hydrogen meet the requirements

a) high excitation and ionization voltage and

b) large effective cross-sections with respect to electrons in the speed range accordingly 0.5 to 1.0 electron volts.

The latter gas is practically completely dissociated at the high temperatures of the high pressure plasma, so that only the properties of atomic hydrogen have to be taken into account at this point to need. As an example, FIG. 1 shows the atomic cross-section of helium as a function of the relative speed drawn. As you can see, the speed range is around the Ramsauer minimum of the gases xenon, krypton, argon, the atomic cross-section of helium compared to electrons is quite considerable greater; the same is true for hydrogen.

The fact that the light gases like helium and hydrogen have a much higher thermal conductivity possess appears to be a disadvantage at first, since a dissipation of the heat of the discharge arc leads to a

ίο Decrease in the radiation or light yield of the discharge arc can lead. Extensive measurements, the results of which are shown in Figs. 2 to 5, but prove that these fears are actually not being fulfilled, at least in certain areas. This fact can be attributed to the fact that with constant current strength the specific power conversion per unit volume of the plasma increased; because, as with pure xenon (resp. Krypton or argon) high pressure discharge lamps are already known, the light yield increases considerably with increasing specific output. Figures 2 and 3 show the rise in the gradient a xenon discharge as a function of the partial pressure of the added helium gas. Fig. 4 and FIG. 5 show the light yield of a xenon discharge as a function of the partial pressure of the admixed Helium gas. Finally, FIG. 6 shows another example of a high-pressure gas discharge lamp shown schematically according to the invention.

The values shown graphically in FIGS. 2 and 4 were obtained using a xenon high-pressure discharge lamp with admixtures of helium with partial pressure values pn _e of 1 to 3 atm. measured while the xenon partial pressure p _Xe 28 Atm. fraud. The following table contains the numerical values for p _Be , Pne'-Pxe ^and the voltage drop A U.

Table 1

Increase in the voltage drop AU as a function of the He partial pressure pfj _e or the mixing ratio

Pb, -Px, (Pxe = 28 Atm.)

p _He (atm.) 1.0 1.5 2.0 2.5 3.0

pHe-Pxe «1: 28 1: 19 1: 14 1: 11 1: 9.5

AU (V) 4.4 7.7 10.1 12.2 15.5

AU (»/ <,) 4.7 8.3 10.9 13.1 16.7

The increase in the voltage drop increases approximately linearly with the helium partial pressure and amounts to at 3 atm. Helium, d. H. 11% of the xenon partial pressure, around 17%. According to FIG. 4, the associated luminous efficiency is independent of the helium partial pressure. she only takes place at helium partial pressure values above 6 atm. noticeably off.

3 relates to a discharge lamp with a basic filling of 39 atm. Xenon and admixtures from 300 to 900 torr of helium. Here, too, the gradient increases almost linearly with the helium partial pressure at. The following table gives the numerical values.

Table 2

Increase in the voltage drop Δ U as a function of the He partial pressure p _He or the mixing ratio p _He : p _Xe (p _Xe = 39 Atm.)

p _He (Torr) 300

PHe'PXe ~
AU (V)
AU (· !,)

1: 99

1.8

1.6

400

1:74

2.7

2.4

500
1: 59
3.6
3.2

600
1:49
3.7
3.3

700

1:42

5.0

4.4

800
1:37

4.4
3.9

900
1:33
5.6
4.9

The light output with this lamp remains in the entire range of the measured helium partial pressures constant, as FIG. 5 shows.

Because of the high mechanical temperature stress on the discharge vessels of such high-pressure gas discharge lamps Quartz glass is usually used as the material. Since now the hot quartz glass for Gases with a small atomic radius such as helium or hydrogen are permeable, these gases diffuse in the operating state out of the vessel. This can be countered by around the actual discharge vessel around it an additional envelope made of a glass that is not permeable to these gases is provided, which in turn, because of the larger diameter, no higher thermal Subject to stress. Therefore normal glass, possibly hard glass, can be used for this. It the envelope vessel can then be filled with the additional gas in question, i.e. helium or hydrogen, and with such a pressure that corresponds to the partial pressure of this gas in the interior of the discharge vessel. Even the actual xenon discharge tube can initially be used without any helium or Hydrogen additives are completed, since the equilibrium of the in operation after a few hours Adjusts the helium or hydrogen partial pressure in the inner and outer vessels. The filling of the Enveloping vessel with the light gases still has the pleasant consequence, a cooling of the quartz glass of the actual To effect discharge vessel.

Claims (4)

Patent claims: 1. Electric high-pressure gas discharge lamp, which emits heavy noble gases when excited of atomic weight over 39 as well as others, as a result of greater excitation and ionization voltage Contains lighter gases not excited to radiation with an atomic weight of less than 21, characterized in that, that such gases not excited to radiation are added, their cross-sections compared to electrons in the speed range from 0.5 to 1.0 electron volts at least twice are as large as those of the heavier noble gases excited to radiation, with the proviso, that the relative content of the lighter gases, measured by the partial pressure, is more than 5 to 20 per cent the content of the heavier noble gases excited to radiation. 2. Electric high-pressure gas discharge lamp according to claim 1, characterized in that at Use of krypton or xenon as the excited gas, helium or hydrogen as the non-excited gas Gas are added. 3. Electric high-pressure gas discharge lamp according to claim 2, characterized in that at Use of xenon as the excited gas helium with a partial pressure of about 11% of the Xenon pressure is added. 4. Electric high-pressure gas discharge lamp according to claim 1 to 3 with a discharge vessel made of a material that is permeable to the gases not excited to radiation during operation, thereby characterized in that the actual discharge vessel is surrounded by an envelope vessel which is used for the gases in question is impermeable and contains these gases at such a pressure that their Partial pressure corresponds to the interior of the discharge vessel. Considered publications:
Swiss Patent No. 297 983;
U.S. Patent No. 2,721,285. 1 sheet of drawings © β »657/201 9.58