Wha is Ultra-violet Radiation

 

Ultra-violet Radiation    

Ultraviolet radiation is electromagnetic radiation with wavelengths between 10 and 400 nm that is invisible to the human eye. In the electromagnetic spectrum, ultraviolet is located between visible light and X-rays. The therapeutic portion of the ultraviolet spectrum can be categorized into the following categories for descriptive purposes:
UVB (280-315 nm) 
UVA (315-400 nm)
UVC (under 280 nm)
Ultraviolet radiation from the sun can frequently cause skin damage like sunburns, but it can also be utilized therapeutically when used in conjunction with a generator.

Ultra-violet generators

These often take the shape of lamps that use a high- or low-pressure tube to pass current across.

Mercury vapor and high pressure burner

This is frequently fashioned like a U to function essentially as a point source. Quartz, which is used to make the burner, has a low coefficient of expansion, can tolerate extremely high temperatures, and permits the passage of ultraviolet light. Low pressure argon gas is enclosed in a tube because low pressure significantly lowers electrical resistance. An electrode is sealed into each end of the tube, which also contains a small amount of mercury. Two metal caps surround the ends, and argon is ionized by applying a high potential difference across them.

Argon Ionization for Current Generation:

Since argon has a complete outer shell of electrons, it is generally very stable and inert; therefore, ionizing the argon atoms is necessary to send a current down the tube. The atom's outer shell loses one electron, resulting in the production of a positive ion (the portion of the argon atom that still has an excess of positive protons) and a negative particle (the electron). To ionize the argon, a significant amount of energy is needed, which is applied for a brief period of time via the metal caps at either end of the tube to create an extremely high potential difference of 400 volts.

Ionization Process in Gas Lamps:

In actual use, this is achieved by pushing the lamp's "Start" button, which steps up the mains voltage to 400 volts by introducing an auto-transformer into the circuit. Following argon ionization, the positive and negative particles flow through the burner due to a standard mains voltage between the electrodes, creating an electric current. After moving around the circuit to the positive terminal, the electrons pick up an electron by the positive ions moving to the negative terminal. In general, the quantity of electrons that exit the burner at the positive terminal and enter at the negative terminal is exactly equal. Collisions between moving ions and neutral argon atoms during the two-way movement of charged particles further ionize the particles, resulting in a continual creation of ionized particles that support the current flow across the tube. As with any electrical current, this current flow can be visualized as a glow discharge, and it produces a significant amount of heat as well (Joule's law). The mercury inside the tube eventually evaporates due to the production of enough heat, and the mercury vapour itself ionizes.

Mercury Vapor Lamp Emission Process:

When excited electrons in mercury atoms return from a higher-energy quantum shell to their regular shell, photons are emitted, resulting in the production of ultraviolet radiation. This process also releases energy. However, concurrently visible and infra-red 4). Ultraviolet only makes up a small percentage of the overall output at the generated

the entire vaporization, recombination, and argon ionization process. It takes a while for ionization to occur; five minutes pass between lighting the burner and the peak of the ultraviolet emission. When the lamp is switched off, the mercury and argon ions switch places, bringing everything back to their initial neutral state inside the tube. But a lot of heat has been produced, which increases the electrical resistance across the tube. As a result, it takes some time for the tube to cool down before striking the arc once more.

Tridymite formation

Tridymite, a different type of silica, is sadly created when part of the quartz is heated up inside the burner. Since tridymite is opaque to ultraviolet light, as the percentage of tridymite grows, the lamp's overall output progressively decreases. In an extremely basic form of compensation, the burner circuit has a variable resistance. When the quartz transforms into tridymite, the resistance decreases, increasing the intensity of current across the tube (according to Ohm's law). This increases the production of ultraviolet light, but output remains constant when the quartz transmits less light.

In order to facilitate the reduction of the stabilizing resistance at the designated intervals (about every 100 hours), the 'burning time' is documented in a book or on an integrated meter within the apparatus. The burner tube needs to be replaced in its entirety since so much tridymite has formed after 1000 hours of burning. If contaminants etch onto the quartz tube, output may be further decreased. This can be caused by allowing dust from the atmosphere to collect on the tube or by touching the cold burner with your fingers and leaving grease on it.

Cooling

The high-pressure burner produces a significant amount of infrared light, which the body absorbs and transforms into heat. As a result, if the lamp is air-cooled, the patient can only be positioned 50 centimeters away from it without risk of burns. Typically, the burner is contained in a parabolic reflector that can be tilted using a stand.

Ozone formation

Ozone is created by the photochemical reaction of UV energy with a wavelength less than 250 nm on atmospheric oxygen (01).

The Kromayer lamp

By using a water-cooled mercury vapour lamp, the Kromayer lamp removes the risk of an infrared burn. Its advantage is that it can be applied directly onto tissues or, with the appropriate applicator, can be used to irradiate within a bodily cavity or sinus.

Construction

The high-pressure mercury vapour burner that powers the Kromayer lamp operates similarly to the previously discussed air-cooled light. It is, nevertheless, totally encased in a jacket of distilled water that is constantly moving in order to absorb infrared radiation. To cool the water, a pump and cooling fan are built inside the Kromayer lamp's body.

Once the burner is turned off, the water circulation should be left running for five minutes to allow the lamp to cool.
The ultra-violet light emerges from the water that flows between two quartz windows at the front of the Kromayer head. An applicator of quartz is attached to this window with a particular attachment in order to cure sinuses. These applicators use total internal reflection to transfer ultraviolet light to their tip, but because they are frequently long, some ultraviolet light will undoubtedly be absorbed, necessitating the administration of a noticeably longer dose.

High-pressure mercury vapor burner spectrum:

Electromagnetic waves in the visible, infrared, and ultraviolet range are produced by mercury vapour lamps. The majority of the output is UVA (315-400 nm) and UVB (280-315 nm), with only a small percentage being (wavelength <280 nm). The UVC penetration depth of these three categories of UV radiation. A phototube calibrated for a specific wavelength, such as 365 nm, can be used to measure the burner's output. The tube absorbs the wavelength and generates an electric current, which can be measured with an ammeter.

At this wavelength, the amount of UV light increases with current. When radiation impacts thermal connections and generates an electric current proportionate to the overall amount of ultraviolet light rather than any particular wavelength, a thermopile may be employed.

Fluorescent tubes for the production of ultra-violet

The fact that the mercury lamp emits a certain amount of short UV radiation is one of its main issues. Several kinds of fluorescent tubes have been developed since long-wave ultraviolet light is frequently used in modern treatment regimens rather than short-wave light.

Every tube has a different spectrum depending on the kind of phosphor coating. Each tube is around 120 centimeters long and composed of a glass type that permits the passage of long-wave ultraviolet light. A unique phosphor is applied to the inside of the tube.

An ionization process akin to that of the mercury vapour tube creates a low-pressure arc inside the tube between its ends. Although short-wavelength ultraviolet light is generated, it is absorbed by phosphor and reemitted with a longer wavelength. The output of the tube can be fully UVA (360-400 nm) or partially UVB and part UVA (280-400 nm), as in PUVA apparatus, depending on the specific phosphor utilized. Accurate control over the emitted wavelength is achievable, though.

Theraktin tunnel

Theraktin tunnel consists of a semi-cylindrical structure with four fluorescent lamps fixed within. Every tube is positioned within its own reflector to ensure that the patient receives a uniform dose of radiation, enabling treatment of both half of the body. Fluorescent tubes with a 280–400 nm spectrum are typically utilized.

PUVA apparatus

Special fluorescent tubes that are set in a vertical battery on a wall or on all four sides of a box completely enclosing the patient can be used to perform UVA-only radiation. Typically, the patient receives this type of ultra violet therapy two hours after taking a medication like psoralen.