Mercury vapor lamp
A mercury vapor lamp is a gas discharge lamp with a mercury vapor filling. In addition to mercury , which is partly in gaseous form due to the low vapor pressure even at room temperature , it always contains a noble gas (usually argon ) to facilitate ignition.
history
The mercury vapor lamp was invented in 1892 by the Berlin physicist Leo Arons (hence the rarer name Arons tube ). The first commercially produced mercury vapor discharge lamps were the (medium pressure) mercury vapor lamps developed from 1923 to 1932 and sold from 1933. High pressure mercury vapor lamps have also been available since 1934 . The earlier lamps produced a blue-green light, now they are also available with corrected white light. The red component missing in the mercury spectrum is generated by a fluorescent substance on the inside of the outer bulb or by a filament in the outer bulb.
From April 2015, high-pressure mercury vapor lamps must achieve certain energy efficiency classes, otherwise they may no longer be traded. A possible replacement, for example in the field of street lighting, is the use of metal halide lamps or LED lamps .
Types and uses
The different types of construction and output are mostly characterized by the ILCOS lamp designation system and are described in more detail there.
Low pressure lamps
Low pressure lamps have low internal pressures of up to about 10 mbar. Without luminescent material, they have a small amount of visible light, but a high proportion of ultraviolet radiation and are suitable as an ultraviolet source under the name quartz lamp , they have a quartz glass bulb for this purpose . They are used to erase EPROMs and for disinfection purposes , since low-pressure lamps have a primary peak at 254 nm. If synthetic quartz is used, the transparency of the lamp for short-wave light can be further increased and an emission line at 185 nm is obtained. Such a lamp can be used for cleaning and modifying surfaces.
Fluorescent lamps are also low-pressure lamps , but they have a fluorescent phosphor on the inner glass surface . They are used for lighting and have a longer service life and higher light output compared to incandescent lamps (but lower than modern LEDs) . Except for lamps for solariums , UV emission is undesirable, which is why special types of glass are used.
“ Black light lamps ” often have a filter glass bulb that absorbs the remaining visible portion. They use special fluorescent substances that emit in the UV-A and are used to examine minerals or to check banknotes, they are also common for "disco light".
Tubes in the illuminated advertising are - except also used neon tubes - low-pressure mercury lamps with phosphors of the corresponding color. However, it is mostly cold cathode tubes , i. In other words , they have no hot cathodes , but rather cold electrodes , which - with reduced efficiency - the service life is much longer than that of fluorescent lamps. For a long time, the backlighting of laptop displays and flat screens was carried out with such cold cathode tubes, which were increasingly replaced by LED technology from the 2010s onwards .
Medium pressure lamps
This type of construction is used in industrial applications for curing special UV-reactive lacquers, adhesives and printing inks. Depending on the lacquer requirements, the lamps emit mainly in UV-A around 400 nm to UV-C around 250 nm. UV-curable lacquers, paints and adhesives are usually solvent-free or low-solvent and are complete after exposure to UV radiation networked and therefore very durable. Compared to oven-drying paint systems, UV curing saves space and energy. UV-C lamps with a main emission at 250 nm are used to disinfect z. B. water or fish ponds are used.
Important spectral lines of mercury have the wavelengths 313 nm (nanometers), 365 nm (i-line), 405 nm (h-line), 436 nm (g-line), 546 nm (e-line) as well as 577 nm and 579 nm (orange double line). Since these values are precisely known, mercury vapor lamps are often used for teaching purposes to demonstrate the photoelectric effect .
Gas fillings doped with metal halides or gallium and indium are available; they supplement the emission spectrum with UV-A and blue in order to avoid the absorption of UV radiation of shorter wavelengths by color pigments. The excitation of the mercury plasma takes place conventionally via electrodes or without electrodes with microwaves . Lamps shorter than 0.5 m in length are operated with chokes at 400 V, longer lamps (up to 2.3 m) with resonance stray field transformers .
High pressure lamps
These lamps have an operating pressure of up to around 1 MPa (corresponds to 10 bar), which they reach after a few minutes of heating. The arc constricts to 2 to 3 mm and there is already a slight pressure broadening of the emission lines.
High pressure mercury vapor lamps are often used for street and industrial lighting. You need a ballast , but not an ignition device, because the discharge vessels ("burners") have an ignition electrode that is fed via a small built-in cold-conductive series resistor (see picture).
The lamps have a good light output and a blue-green light color. After starting, they emit almost no light until a significant amount of mercury has evaporated and the internal pressure has risen.
Lamps without fluorescent material have a pronounced line spectrum with a sensitive lack of red and therefore a poor color rendering index . The discharge vessels made of silica glass are installed in a hard glass bulb that is partially evacuated for thermal insulation and that can have a fluorescent substance inside to improve color rendering. The protective glass bulb absorbs the ultraviolet radiation even if it does not carry a fluorescent material.
The color rendering index (Ra) of standard high-pressure mercury lamps is around 50. They are available in different color temperatures , depending on the area of application. The company Signify sold under the name "HPL 4 Pro" mercury vapor lamps with a color rendering index of just under 60 (standard fluorescent lamp is usually over 80, bulb to 100).
Features of various high pressure mercury vapor lamps:
- Classic design (all manufacturers): 4200 K color temperature, Ra at around 45. neutral white light
- DeLuxe version (Osram): 3400 K color temperature, Ra at around 54. " Warmer " light and more light output
- HPL-4 version neutral white (Philips): 4200 K color temperature, Ra just under 60. Good luminous efficiency, " cool " light
- HPL-4 version warm white (Philips): 3500 K color temperature, Ra just under 60. Good luminous efficacy, a little “warmer” than neutral white
- SuperDeLuxe version (Osram): 3200 K color temperature, Ra just over 60. Moderate light output, but “warm” light
By adding other elements (other metals and halogens) to the mercury, metal halide lamps with even better color rendering are obtained.
Special forms
Mixed light lamp
In addition to the quartz or ceramic burner, a filament is housed in mixed light lamps. This is connected in series with the burner within the lamp and, in addition to generating light, also serves to limit the current.
Therefore mixed light lamps - and only these - can be operated directly on 230 V without a ballast. The color rendering is slightly better than that of the pure mercury vapor lamps. However, due to the filament, the service life is limited to about 4000 hours and the efficiency is lower at 10 to 25 lm / W.
Mixed light lamps are available in the power classes 100, 160, 250 and 500 watts. One advantage is the immediate (50 percent) emission of light. After a few minutes, the color is similar to daylight.
Therapeutic lamps
The mountain sun and the Kromayer lamp consist of high pressure mercury vapor burners without an evacuated protective glass bulb; the latter is water-cooled. Their short-wave radiation was used to treat skin diseases and vitamin D deficiency.
High pressure lamps
Extremely high pressure lamps have an operating pressure of up to 10 MPa (100 bar), which only builds up slowly after ignition, when the lamp has reached its operating temperature. Therefore, in the first few seconds of operation, it shows a line spectrum that gradually changes into a strong continuum due to pressure broadening , whereby the color reproduction is considerably improved; They have a very high luminance, are made of thick silica glass without an additional bulb and serve as an intense ultraviolet source in photolithography (g-, h- and i-line light sources). Their conversion efficiency from electrical to radiant energy in the visible and ultraviolet is up to 60%, the rest is given off as heat in the form of radiation as well as via thermal conduction of the electrodes. The frequently used g-, h- and i-lines achieve almost 30% electro-optical efficiency with outputs of typically 50 W to 12 kW.
These lamps have massive electrodes made of tungsten, sometimes very large amounts of mercury and mostly screw terminals as connections. The operating location is prescribed. The electrode spacing of these lamps is only a few millimeters and the brightest point is directly on the cathode, which is why they are also known as short-arc lamps. In addition to mercury, high-pressure lamps are also available filled with xenon (see xenon high-pressure lamp ); they are used as illuminants in motor vehicle headlights ( xenon light ) and cinema projectors .
These lamps are dangerous to handle - protective measures must be taken during handling, installation and operation to prevent explosion. In addition to the electrical safety precautions, protection from the harsh ultraviolet radiation and the ozone generated by it from atmospheric oxygen is required. The typical service life is between 2000 and 3000 operating hours.
Emission spectrum
The emission spectrum of a mercury vapor lamp is a line spectrum, the spectral lines of which are widely used in science and technology. In the following, the wavelengths of intense main lines of a neutral mercury atom are listed together with application examples. The exact position (decimal places in the nanometer range) of the lines is also dependent on the mercury isotope of the emitting atom. The isotope ratio has an influence on the mean position and the bandwidth of the spectral lines.
| Spectral range | wavelength | alternatively | Applications | |
|---|---|---|---|---|
|
ultra- violet |
Far: UV-C |
184.95 nm | ||
| 248.3 nm | Main emission line | |||
| 253.65 nm | Main emission line | |||
| 280.4 nm | ||||
| Middle: UV-B |
296.73 nm | Main emission line | ||
| 312.56 nm | ||||
| Near: UV-A |
334.15 nm | Main emission line | ||
| 365.01 nm | i line | Main emission line, photolithography |
||
|
Visible bares light |
violet | 404.66 nm | h-line | Double line |
| violet | 407.78 nm | h-line | ||
| blue | 435.83 nm | g line | Main emission line, photolithography |
|
| cyan | 491.60 nm | |||
| green | 546.07 nm | e line | ||
| orange | 576.96 nm | orange colored. Double line 577/579 nm |
Main emission line | |
| orange | 579.07 nm | |||
| red | 614.95 nm | |||
|
infra- red |
Near: IR-A |
1013.97 nm | t line | |
| Near: IR-B |
1529.88 nm | |||
| 1970.09 nm | ||||
| 2325.4 nm | ||||
Light pollution from outside light
Conventional industrial and street lighting as well as exterior lighting of buildings with metal halide, halogen and fluorescent lamps result in a clear brightening of the atmosphere, which is noticeable as " light pollution ". In addition to the worsening of the observation of the night sky in astronomy , this affects people, for example in their sleep rhythm. Nocturnal insects , birds, bats and amphibians are primarily affected, and moths are particularly affected among the insects . Their eyes react strongly to the UV radiation from high pressure lamps. Building and street lamps are flown around for hours until the animals grow tired or die exhausted. For Germany there are estimates for around 180 billion insect corpses every year. These missing animals have serious consequences for the food chain of other animal species.
Recent developments in medium and high pressure mercury lamps have lower UV light. This is not enough to solve the recognized environmental problem. With the increasing use of suitable LED lights and sodium vapor lamps , which do not contain any UV or IR components in the light, the objected effect on moths could be reduced.
costs
Mercury vapor lamps with the common household E27 base are available in stores for 230 volt connections in versions of 50, 80 and 125 watts with a light output of around 50 lumens per watt for around 6 €. With the E40 socket for 230 volt connection, there are versions in 250 watts (approx. 9 €), 400 watts (approx. 15 €), 700 watts (approx. 45 €) and 1000 watts (60 to 70 €) .
literature
- Hans R. Ris: Lighting technology for the practitioner. Basics - lamps - luminaires - planning - measurement. 2nd, expanded edition. VDE-Verlags GmbH, Berlin et al. 1997, ISBN 3-8007-2163-5
- Günter Springer: Electrical engineering expertise (= European teaching aid 30318). 18th, completely revised and expanded edition. Verlag Europa-Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9
Web links
Individual evidence
- ↑ W. Heering: ( Page no longer available , search in web archives: Lichttechnisches Institut Universität Karlsruhe )
- ↑ Answers to frequently asked questions on the subject of “light” , German Federal Environment Agency, queried on October 16, 2010
- ↑ Examples can be found in the technical report on IEC 1231 ( Memento of the original of February 22, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. of the ZVEI
- ↑ Crystec Technology Trading GmbH: Surface cleaning with UV light . Retrieved January 31, 2011.
- ^ Katrin Sedlmaier - seminar lecture at the TU Berlin. Retrieved March 17, 2018 .
- ↑ Oliver Starzmann: System technology for UV curing ( Memento from September 28, 2007 in the Internet Archive )
- ^ Heraeus - High Pressure Mercury Lamps. (No longer available online.) In: HNG OAO9E / 10.14 / wsp. Heraeus Noblelight GmbH, 2015, archived from the original on June 26, 2016 ; accessed on June 26, 2016 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Osram 12,000 W microlithography lamp. OSRAM GmbH, 2016, accessed on June 26, 2016 .
- ↑ a b David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Line spectra of the elements, pp. 10-46.
- ↑ Line spectra of mercury and helium ( Memento of the original from August 29, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Thomas Posch: The end of the night. Light pollution problems . Wiley, 2009 (book summary)
