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What Is an X-Ray Tube?

An X-ray tube is a type of X-ray generation tube that converts electrical input power to produce X-rays.

X-Ray Tubes are classified into two types according to the type of tube: sealed tubes, in which the inside of the tube is always kept in a vacuum, and open tubes, in which a vacuum pump is installed on the outside of the tube to create a high vacuum.

Sealed tubes are also known as anode tubes. They are further classified into two types: rotating anode tubes with a rotating anode and fixed anode tubes without a rotating anode. The fixed-anode tube has a rotating anode, which allows heat dispersion and increases the current flowing through the X-ray tube.

X-Ray Tubes are classified into microfocus and mini-focus (or millifocus) types, depending on the focal spot size. These X-ray tubes have a focal spot size on the order of microns and millimeters, respectively.

Uses of X-Ray Tubes

X-Ray Tubes are used as X-ray generators in various fields. X-rays are electromagnetic waves with a wavelength shorter than that of ultraviolet rays, and their high energy allows them to penetrate through materials.

The following are some of the applications that take advantage of this penetrating effect:

• Medical field
  General radiography, mammography, CT examinations, X-ray therapy used in cancer treatment, etc.
• Scientific and industrial fields
  X-ray diffraction, X-ray fluorescence analysis, nondestructive testing, thickness and other material testing, airport baggage inspection, etc.

Principle of X-Ray Tubes

An X-ray tube consists of an enclosure, a cathode, and an anode . When a high voltage is applied between the cathode and anode after the cathode filament is heated by an electric current, hot electrons are emitted from the filament and are directed to the anode target at high speed.

1. X-Ray Driven

The thermal electrons are attracted to the nucleus of the anode material, such as tungsten, and rapidly change direction, releasing energy. At this time, 99% of the energy is converted to thermal energy, but the remaining 1% is emitted as X-rays. These X-rays are called bremsstrahlung X-rays and are characterized by their continuous spectrum.

Where the thermal electrons pass in relation to the nucleus is not uniquely determined, and the X-ray intensity varies depending on where they pass. Therefore, bremsstrahlung has a continuous spectrum.

2. Characteristic X-Rays

Some thermal electrons rarely collide with electrons of the target atom. The collided electrons gain energy from the thermal electrons and are repelled, and then transition to the outer electron orbitals, but because they are unstable, they quickly return to their original orbitals.

The difference in the energy state of the electron orbital is emitted as X-rays. X-ray tubes produce mostly bremsstrahlung X-rays, which are extracted through a window made of beryllium or other material with low X-ray absorption in the tube’s enclosure.

Other Information on X-Ray Tubes

1. Tube Voltage and Tube Current

The intensity and energy of the X-ray tube depend on the tube voltage and current.

Tube voltage
The tube voltage is the voltage applied between the anode and cathode of the X-ray tube. The higher the tube voltage, the shorter wavelength X-ray tube produces. The tube voltage is a parameter that affects the intensity and energy.

Tube Current
The current that flows through the inside of the X-ray tube. The current is generated when thermal electrons generated at the cathode collide with the anode. In a rotating anode tube, the anode rotates to disperse the heat and increase the tube current.

There is a proportional relationship between the tube current and the total X-ray tube intensity. On the other hand, the X-ray energy does not change when the tube current is changed.

2.Transmission Properties of X-Rays

Since X-rays are electromagnetic waves with a very short wavelength, they have the property of transmitting through materials. The transmission rate varies depending on the material, and X-rays are attenuated during transmission.

The higher the energy of the X-ray, the greater its transmission ability.

What Is an Isolator?

Isolators are devices designed to separate or insulate components or systems. They play critical roles across various industries, including electrical and electronics, construction, and pharmaceuticals, by isolating analog signals, insulating buildings from earthquakes, and protecting against external contaminants.

Uses of Isolators

The application of isolators varies significantly by industry:

1. Electronics Industry

Used for surge voltage protection and signal separation, isolators in electronics ensure the integrity of signal-receiving equipment.

2. Construction Industry

In construction, isolators serve as earthquake-resistant supports under buildings, utilizing high-elasticity materials like rubber to dissipate vibrations.

3. Pharmaceutical Industry

Pharmaceutical isolators provide sterile environments for drug development and patient care, employing negative pressure systems and gas sterilization to prevent contamination.

Principle of Isolators

The operational mechanisms of isolators vary across different fields:

1. Electronics Industry

Electrical signal isolation involves amplifying and converting input signals for output, serving also as signal converters.

2. Construction Industry

Vibration-dissipating structures in construction use materials like seismic isolation rubber to reduce building movement during earthquakes.

3. Pharmaceutical Industry

Isolators in pharmaceuticals maintain sterile conditions through negative pressure and gas sterilization, similar to draft chambers.

Types of Isolators

Isolators are categorized into optical and digital types:

1. Optical Isolators

Using LEDs and light-receiving elements, optical isolators transmit signals via light, offering simple, reliable, and cost-effective solutions.

2. Digital Isolator

Digital isolators isolate using capacitors or coils to transmit digital signals, known for their long life and high performance but limited to digital applications.

How to Select Isolators

Selection depends on application requirements:

1. Optical Isolator

Chosen for their distance transmission capability, optical isolators suffer from efficiency drops at temperature variations.

2. Digital Isolator

Preferred for applications requiring high performance and longevity, digital isolators are evolving, with costs and variety being considerations. They are used in applications that are difficult to handle with photocouplers.

What Is an Enabling Switch?

Enabling switches, also known as enabling grip switches, 3-position enabling switches, or simply enable switches, are safety devices integrated into teaching pendants for industrial robots and other machinery.

These switches allow operations only when the operator demonstrates clear intent by holding the switch in the ON position, ensuring that industrial robots are manually operated under controlled and intentional circumstances. This feature is crucial for preventing accidental robot operations and ensuring worker safety.

Uses of Enabling Switches

Enabling switches are critical safety components mounted on teaching pendants, which are used to manually operate equipment like industrial robots. While safety measures usually prevent worker access to operational areas of production equipment, there are instances where operators need to bypass these measures, such as during startup or troubleshooting. Enabling switches ensures that machinery operates only when the operator intentionally engages the switch, thereby protecting them from unintended and potentially hazardous actions.

Structure of Enabling Switches

Unlike standard two-position “ON/OFF” switches, enabling switches operate on a three-position “OFF/ON/OFF” system, which is button-operated. The first position is a neutral state where no contact is made, and the machinery remains inactive regardless of any attempted operations. A light press transitions the switch to the second position, enabling operation as commands are executed. Releasing the button reverts it to the neutral state, allowing for immediate cessation of activity. A stronger press from the second position shifts it to the third, where the machinery stops upon receiving a stop command.

Principle of Enabling Switches

The design of enabling switches considers human reflexes in dangerous situations—whether releasing or gripping the object more tightly. This ensures immediate machine stoppage in both scenarios, thus protecting the operator during unexpected robot movements. The dual-stop mechanism accommodates the unpredictable nature of human reflexes, safeguarding the operator by halting operations whether the switch is released or pressed firmly.

How to Select Enabling Switches

When selecting enabling switches and systems, prioritize those with high safety standards suitable for hazardous areas. Opt for switches with dual contacts and systems designed with controllers capable of shutting down machinery and maintaining safety even if one contact fails. Such systems are engineered to detect faults only when the two contact signals are in agreement, enhancing operational safety.

What Is an Image Intensifier?

An image intensifier is a device that detects extremely weak light or X-rays and amplifies them thousands to tens of thousands of times to make them visible.

Image intensifiers intensify and express light rays. Among these devices are, “X-ray image intensifiers” which visualize X-rays, and “MCP image intensifiers” which visualize weak light such as fluorescence, etc.

Since fluorescence and nighttime light are extremely weak, they are converted to electrons and then electrically amplified to create a contrast that make them appear like an image.

Uses of Image Intensifiers

When you hear the word “X-ray,” you probably think of medical X-rays. Of course they are also used in this case. However, image intensifiers are often used because they can visualize X-rays in the form of an image by simply exposing the patient to very weak X-rays, and they can also view X-rays in real-time.

MCP image intensifiers are also used in fluorescence imaging equipment for fluorescent staining of cells.

Principle of Image Intensifiers

An image intensifier is a device, but what is its inner structure?

An image intensifier consists of three components: a photocathode, which receives light; a device, which amplifies electrons; and a fluorescent surface, which reflects the amplified electrons.

We will now explain the principle using an MCP image intensifier as an example.

Normally, when an MCP image intensifier detects light reflected on the photocathode, the light is converted into electrons. The electrons are then amplified in a microchannel plate, and the image produced when they hit the phosphor that serves as the screen is output as an image.

In the case of X-ray image intensifiers, the conversion from X-rays to electrons occurs at a photocathode. The electrons are further accelerated and focused by the focus electrode and anode power supply to obtain an image.

In this way, the conversion to electrons is performed by a device that matches the fluorescence and X-rays, and the human eye sees the amplified image as a visible image.

What Is a Gunn Diode?

A Gunn diode is a type of diode used in microwave band oscillators and other devices.

Gunn diodes are diodes that utilize the Gunn effect. N-type gallium arsenide (GaAs) is mainly used, and physicist J.B. Gunn discovered that when a DC electric field is applied to a GaAs crystal and exceeds a certain threshold value, oscillation occurs in the microwave region. For this reason, this phenomenon is called the Gunn effect.

Gunn diodes have a region of negative resistance, and this effect is used in microwave oscillators. Negative resistance here refers to the electrical characteristic that current decreases as voltage increases.

Uses of Gunn Diodes

Gunn diodes are commonly used in the microwave region for oscillator radar applications using the Gunn effect.

When a Gunn diode is mounted in a cavity or waveguide and a DC voltage is applied, it oscillates with an intrinsic vibration that depends on the thickness of the crystal. Although the structure is relatively simple, the frequency stability is not as good as that of the usual microwave control method using a VCO or PLL, so it is often used for speed sensors using the Doppler effect in addition to communications.

Familiar applications include speed guns for baseball and radar for speed enforcement.

Principle of Gunn Diodes

Gunn diodes take advantage of the microwave band oscillation phenomenon that occurs when electrons rapidly transition to the band with the higher energy level when a voltage exceeding the critical electric field is applied to a semiconductor crystal with two energy bands. When a graph of energy is drawn, it has two conduction bands with different bottom energies and wave numbers.

When voltage is applied, an electric current flows, and the electrons responsible for this current are those in the conduction band. Normally, more electrons exist in the conduction band with lower energy at the bottom, and as the voltage increases, more electrons are in the conduction band with higher energy. When a certain voltage is exceeded, electrons from the lower level conduction band move to the higher level conduction band, resulting in a decrease in mobility.

This phenomenon causes a decrease in the apparent mobility of electrons, or current, when the voltage is increased above a certain voltage, and thus has the characteristic of negative resistance. As the voltage is further increased, the electrons in the lower level conduction band are transferred to the higher level conduction band, and the current increases again.

At this point, an avalanche of rapid, high-speed electron transfer occurs in the microwave band, resulting in the oscillation phenomenon. While general VCOs (voltage-controlled oscillators) utilize a negative resistance that takes advantage of the impedance matching of transistors, Gunn diodes make good use of the inherent energy bands of semiconductor crystals.

Other Information on Gunn Diodes

1. Application to Speed Sensors

Velocity sensors, a typical application of Gunn diodes, generally use a physical phenomenon called the Doppler effect. The Doppler effect is the principle that the reflected wave of an electromagnetic wave irradiated onto an object moving at high speed is observed at a different apparent frequency than the original frequency of the irradiation.

The frequency of a Gunn diode in a GaAs crystal is about 10 GHz, and the speed of the irradiated object is calculated from the difference in frequency variation. Incidentally, this difference in frequency variation is described as a “whirr” in physical terms, and the variation relative to a frequency of 10 GHz is a very small percentage for speed measurements in the 100 km range for baseball speed guns and automobile speed measurements. 

2. Expansion to Sub-Terahertz Frequencies

Gunn diodes and similar diodes, as well as resonant tunneling diodes, are currently the focus of attention in research institutions as research materials for sub-terahertz frequency oscillators. 

What Is a Scintillator?

A scintillator is a general term for materials that emit light when exposed to charged particles or radiation.

They are classified into inorganic and organic scintillators. Inorganic scintillators, suitable for detecting gamma rays and X-rays, are made from crystals with high atomic numbers. They emit a large amount of light and have excellent energy resolution but respond slowly. Organic scintillators, including plastic and liquid types, are inexpensive, lightweight, and respond quickly, making them ideal for detecting alpha and beta rays.

Scintillators are used in various fields as part of scintillation detectors.

Uses of Scintillators

Scintillators convert radiation into light, ranging from ultraviolet to visible. This light is then transformed into electrical signals by photomultiplier tubes or opto-semiconductors, which are processed to generate images and other radiation-related information.

Applications include X-ray computed tomography (X-ray CT), positron emission tomography (PET), airport baggage screening, food inspection, non-destructive testing of electronic components, exploration of oil and mineral resources, nuclear reactor radiation monitoring, and research in particle, nuclear, and space physics.

Principle of Scintillators

The emission principle of scintillators varies between inorganic and organic types.

1. Inorganic Scintillators

In inorganic scintillators, charged particles or radiation excite electrons from the valence to the conduction band. The recombination of these electrons with holes in the valence band produces scintillation light, corresponding to the energy difference. Impurities in the crystal lattice create new energy levels, allowing the emission of visible light from these modified structures.

2. Organic Scintillators

Organic scintillators emit light through the excitation of individual molecules. Radiation excites electrons to higher energy states, predominantly to the first excited state, resulting in fluorescence. Some electrons may also transition to higher excited states before returning to the first excited state and eventually to the ground state, emitting phosphorescence or delayed fluorescence.

Structure of Scintillators

The structure of scintillators differs between inorganic and organic types.

1. Inorganic Scintillators

Examples include NaI:Tl, LSO:Ce, lead tungstate (PbWO₄), gadolinium silicate (GSO: Gd₂SiO₅ with Ce), and bismuth germanate (BGO: Bi₄Ge₃O₁₂). NaI:Tl, a commonly used scintillator, must be sealed to prevent degradation from moisture absorption.

LSO:Ce, an oxide-based scintillator, emits light via transitions in Ce³⁺ and offers faster response times compared to NaI:Tl.

2. Organic Scintillators

Organic scintillators include crystal, liquid, and plastic types. Liquid scintillators, such as naphthalene, are durable against strong irradiation. Organic molecules like anthracene and stilbene, with their pi-electronic structures, offer multiple excited states but are less commonly used due to their anisotropic response and processing challenges. Plastic scintillators, created by dissolving organic emitters in plastic, are user-friendly and suitable for detecting alpha and beta rays, though less effective for gamma rays.

What Is a Device Server?

A device server enables the connection of non-networkable devices to a network via serial interfaces or USB ports. This is essential for devices like older printers and scanners, which use RS-232C or USB connections and cannot directly connect to a network due to differing communication protocols. A device server acts as a bridge, converting these protocols to enable network connectivity.

This connectivity allows a single device to be accessible from multiple PCs, enhancing usability and flexibility.

Uses of Device Servers

Device servers are pivotal in networking devices that lack inherent network capabilities. By doing so, equipment such as legacy printers and scanners become accessible from multiple computers. Additionally, device servers facilitate the remote operation of computers via peripherals like keyboards and mice, overcoming the limitations imposed by physical proximity and cable length. Some device servers also support Internet connectivity, enabling the creation of large-scale systems and remote monitoring.

Principle of Device Servers

Device servers convert the communication method of serial devices to be compatible with Ethernet interfaces. This conversion can occur in three modes:

1. Real Com Mode

Creates a virtual COM port on the host computer, enabling data transfer and operational control through serial port line signals.

2. Socket Mode

Facilitates access to serial device servers on a TCP/IP network via standard sockets API, eliminating the need for additional drivers.

3. Port Sharing Mode

Allows multiple host computers to share a single device server’s port, enabling them to receive data from the same serial device concurrently.

Types of Device Servers

The choice of device server depends on the specific networking needs of USB or serial devices:

1. Embedded Device Server

These compact servers are integrated into devices, offering basic networking capabilities for small devices.

2. Serial Device Server

Suitable for networking devices with serial interfaces, often used in industrial settings for data collection and device control.

3. USB Device Server

Enables networking of USB devices within a small network, supporting high-speed data transfer for applications like USB audio and web cameras.

4. Internet Device Server

These servers support Internet connectivity for remote monitoring and management systems, offering a cost-effective solution without the need for dedicated lines.

What Is a Nickel Metal Hydride Battery?

A nickel metal hydride battery is a type of rechargeable battery that can be charged and discharged, using a hydrogen storage alloy for the negative electrode and nickel hydroxide for the positive electrode.

Nickel metal hydride batteries are expensive because they use a hydrogen storage alloy instead of cadmium, but can be charged and discharged using a large current and have a large capacity per unit mass.

In addition, compared to other rechargeable batteries, nickel-metal hydride batteries have a relatively small memory effect (the voltage drop that occurs during discharge when batteries are repeatedly recharged without being fully discharged), and can be used repeatedly without performance degradation.

Uses of Nickel Metal Hydride Batteries

Nickel metal hydride batteries are used to take advantage of their high performance and long life, and are used in automotive batteries, notebook PCs, dry cell batteries, and other applications requiring high output and reliability.

In recent years, lithium-ion batteries, which do not have memory effect or self-discharge and have a larger capacity per unit mass and higher operating voltage, have come to be used.

Principles of Nickel Metal Hydride Batteries

1. Composition of Nickel Metal Hydride Battery

Nickel metal hydride batteries consist of electrodes (positive electrode: nickel oxyhydroxide, negative electrode: hydrogen storage alloy), a separator made of olefin nonwoven fabric, and potassium hydroxide solution as electrolyte. In the case of a dry cell, the structure wound around these components is contained in a can. 

2. Charge-Discharge Reaction of Nickel Metal Hydride Battery

During discharge of a nickel metal hydride battery, at the positive electrode, nickel oxyhydroxide receives electrons in the presence of water, producing nickel hydroxide and hydroxide ions. At the anode, hydrogen ions and electrons are released from the hydrogen storage alloy in the presence of hydroxide ions to produce water.

During discharge, the reaction proceeds in the opposite direction: at the cathode, hydroxide ions react with nickel hydroxide to produce nickel oxyhydroxide, which releases electrons. At the anode, hydrogen is adsorbed by supplying electrons.

Figure 1. Charge-discharge reaction equation of a nickel-metal hydride battery

The charging and discharging of a nickel metal hydride battery occurs through a simple reaction that involves the adsorption of hydrogen and the production of water. For example, lead-acid batteries used in automobile batteries are charged and discharged through a precipitation-dissolution reaction of the electrodes, so repeated charging and discharging inevitably results in deterioration of the electrodes. A nickel metal hydride battery has no such degradation mode and can be used semi-permanently as long as the electrode itself does not deteriorate, making it a battery with a long service life. 

3. Electrodes of Nickel Metal Hydride Battery

Co-alloys have been mainly used for the negative electrode in the past in order to achieve high capacity, but there has been a move toward Co-free electrodes mainly due to cost considerations. However, the use of Co-fewer alloys has been progressing, mainly due to cost considerations. As for the cathode, nickel oxyhydroxide in the charged state is highly conductive, but nickel hydroxide in the discharged state is an insulator, which causes problems such as loss of electron paths during discharge. For this reason, cobalt oxyhydroxide or other materials are added to give conductivity.

Other Information on Nickel Metal Hydride Batteries

Nickel Metal Hydride Battery Characteristics

1. Battery Characteristics
The nominal voltage of nickel metal hydride battery is 1.2V, which is the same as that of a nickel-cadmium battery. This is because the reactions used for charging and discharging are similar. Since the nominal voltage of lead-acid batteries is 2.0 V and the rated voltage of lithium-ion batteries is 3.7 V, they are relatively low voltage batteries. Since these batteries can easily carry a large current, they are used in equipment that requires high output, such as hybrid cars.

Nickel metal hydride batteries have a memory effect (the voltage of the battery drops as it is repeatedly recharged, resulting in a decrease in usable capacity and an inerting effect. Therefore, understanding the characteristics of the battery when using it will maximize its service life.

Figure 2. Memory effect

2. Safety
Basically, battery explosions and fires are caused by the ignition of organic solvents, which are electrolyte solvents, by sparks created by short circuits.

The electrolyte solvent in nickel metal hydride batteries is water, so even if a spark should occur, it will not ignite. Therefore, the current and voltage control mechanisms do not need to be designed as rigorously as in lithium-ion batteries, thus lowering the manufacturing cost. This low cost is one of the reasons why nickel metal hydride batteries are still widely used in industry.

Figure 3. Comparison of lithium-ion and nickel-metal hydride batteries

3. Environmental Impact
Lithium-ion batteries, lead-acid batteries, and nickel-cadmium batteries contain hazardous substances with a high environmental impact (e.g., cadmium in nickel-cadmium batteries is a causative agent of Itai-itai disease, one of the four major pollution diseases). The electrolyte is also an environmentally friendly storage battery because it does not use organic solvents.

What Is a Halogen Lamp?

A halogen lamp is a type of incandescent lamp that contains trace amounts of halogen elements (iodine, bromine, etc.) in addition to inert gases such as nitrogen and argon.

Halogen lamps emit light in the same way as ordinary incandescent lamps, by passing electricity through a filament inside the bulb. The filament is a thin, thread-like metal wire, most often made of tungsten, which has the highest melting point of all metals (3,422°C).

Uses of Halogen Lamps

1. Lighting

Halogen lamps are used for spotlighting on product shelves, floodlighting, car headlights, studio and stage lighting, and other applications because of their compact size, high luminance, easily adjustable light distribution (light spread), and good color rendering properties (colors are close to those seen in sunlight). However, with the spread of LED light sources, opportunities for use in lighting applications are decreasing.

2. Projectors

Halogen lamps have been used as light sources for OHPs and slide projectors used in schools, etc. Today, LED and laser light sources are becoming the mainstream.

3. Light Source for Spectroscopic Analysis

Light sources for spectroscopic analysis are used because they have a constant brightness over a wide range of wavelengths and little fluctuation in intensity over time.

4. Heater

The fact that the majority of the energy radiated is infrared tells us that halogen lamps as light sources are inefficient but excellent heaters. Therefore, halogen lamps have applications in a variety of situations requiring localized heating, such as heat retention, heat treatment, drying, and high-temperature molding of food and materials, in addition to localized heating indoors and outdoors.

Principle of Halogen Lamps

The filament temperature of ordinary incandescent lamps ranges from 1,500 to 3,000°C, while that of halogen lamps is usually as high as 2,500 to 3,000°C, with special ones reaching as high as 3,300°C. Therefore, a small amount of tungsten is constantly evaporating on the surface of the filament.

Figure 1. Halogen Cycle

To suppress the blackening phenomenon, halogen lamps contain a small amount of halogen elements along with inert gas in the bulb. In this way, if conditions such as temperature and materials are appropriate, the blackening phenomenon will not occur due to the halogen cycle that occurs in the lamp.

The halogen cycle is a phenomenon that occurs in the following manner.

1. Tungsten atoms evaporate and diffuse from the hot filament during lighting.
2. Halogen gas reacts with the evaporated tungsten to form tungsten halide.
3. If the glass wall is hot enough (>170°C for iodine halogen), tungsten halide does not adhere to the glass wall.
4. When the tungsten halide moves near the hot filament, it decomposes and the tungsten atoms return to the filament.

The halogen cycle prevents filament wear and tungsten-induced blackening of the glass inner wall.

Structure of Halogen Lamps

Figure 2. Incandescent and Halogen Lamps

To achieve a halogen cycle, the encapsulated glass must be kept at a high temperature. When iodine is used as a halogen gas, the glass temperature must be 170°C or higher, and when bromine is used, the glass temperature must be 250°C or higher.

Therefore, quartz glass, which can withstand high temperatures, is usually used, and molybdenum foil is used to electrically connect the inside and outside of the halogen bulb so that the inside remains airtight even at high temperatures.

Other Information on Halogen Lamps

1. Disadvantages of Incandescent Bulbs

In ordinary incandescent bulbs, blackening occurs when evaporated tungsten adheres to the inner wall of the bulb’s glass. As the filament wears out, the luminous efficiency inevitably decreases.

This blackening phenomenon is an obstacle, making it difficult to miniaturize incandescent bulbs with high power consumption or to raise the filament temperature to higher levels to increase brightness and color temperature.

2. Characteristics of Light Emitted From Halogen Lamps

Figure 3. Filament Temperature and Intensity Distribution of Emission Spectrum

The light spectrum emitted from a halogen lamp is almost identical to the blackbody radiation spectrum, which corresponds to the temperature of the filament. Because the temperature of the filament is lower than that of the sun, the emitted light contains almost no ultraviolet light, and its visible light portion has a slightly higher red component, resulting in a warm white light appearance.

The peak of the radiation is in the near-infrared region with wavelengths of 900 to 1,000 nm, and the majority of the radiation is in the visible to near-infrared region with wavelengths of 500 to 3,000 nm.

3. Advantages of Halogen Lamps

Compared to ordinary incandescent lamps, halogen lamps allow a smaller distance between the filament and the encapsulated glass. Also, the temperature of the filament can be higher, which offers various advantages.

• Because of their small size, transportation costs can be significantly reduced.
• Since the blackening phenomenon does not occur, there is almost no decrease in brightness until the end of the life of the product.
• When used at the same filament temperature, the service life can be more than doubled.
• Brightness can be increased by about 30% for the same life setting.
• The use of quartz glass allows the surface temperature to be raised to approximately 900°C (twice as high).
• Quartz glass has high thermal shock resistance and does not break even when heated to 900°C and placed in cold water.

4. Advantages of Halogen Lamps

• Radiant Heat
  90% of the power consumption is radiant light that transfers energy directly to the object to be heated, making it suitable for rapid heating.
• Low Heat Loss
  Radiant light reaches the object to be heated without being affected by air currents or air temperature, and since the radiation source (filament) is inside the glass tube, it is hardly affected by its surroundings.
• Fast Start-Up
  Thermal radiation output reaches 90% of rated output within 1 second after energizing.
• High Energy Density
  Small-sized halogen lamps can maintain a heat generation density of 100 w/cm2 or higher, which allows them to heat objects to 1500°C or higher.
• High Thermal Shock Resistance
  The lamp will not be damaged even if water is splashed on it during use.
• Metal Heating
  Wavelengths of visible light to near-infrared rays are easily absorbed by metals, making them suitable for heating metals.
• Non-Contact Heating
  Does not contaminate the object being heated or the surrounding environment. Heating of a sample in a separate room is also possible through a glass window, etc.
• Optical Control
  A reflective mirror or similar device can be used to precisely spot-heat a targeted area.

What Is a Neon Lamp?

A neon lamp is a lighting device that emits light when a glow discharge occurs in a glass tube filled with neon gas.

The lamp can emit light in a variety of colors by combining it with argon gas or by using a transparent tube and a fluorescent tube. Two electrodes are mounted inside the glass tube, and glow discharge is generated by externally controlled voltage.

In recent years, LEDs have become the mainstream lighting device, and neon lamps are used in the same way. The advantages of neon lamps include low power consumption, long life, no heat generation, and resistance to shock.

Uses of Neon Lamps

Neon lamps are lamps that emit light by filling a glass tube with neon gas. They are used for various effects and lighting, with entertainment district lighting being a typical example. In recent years, neon lamps have also been used for interior decoration.

Another application is the neon light-emitting detector. This detector uses the current from a neon tube that flows through a human being to the ground. It has the advantage of not requiring batteries, but it should be noted that it cannot be used when wearing insulated gloves, and there is a risk of electric shock.

The glass tube itself, which is filled with gas, can be processed by bending and stretching to be used as a text expression. By adjusting the thickness of the glass tube, the luminous intensity of the neon tube can be adjusted. Because of their low power consumption and long life, neon tubes are sometimes used for long periods as all-night lights, indicator lights (pilot lamps), and other lighting applications.

It was one of the most popular lighting devices until the advent of LEDs and is still used in the situations described above.

Structure of Neon Lamps

It consists of a glass tube with two electrodes made of iron or nickel and filled with neon gas at a low pressure of about 10~15 mmHg. The glass tube may be transparent or coated with fluorescent paint on the inside.

Neon gas emits red light in transparent tubes and pink or orange light in tubes coated with fluorescent paint.

Other Information on Neon Lamps

1. Neon Lamp Emission

When voltage is applied between the electrodes, the electrons between the electrodes are accelerated by the electric field and collide with neon gas, ionizing it into positively charged cations and electrons.

The resulting cations collide with the cathode, which emits secondary electrons. The emitted secondary electrons move to the anode, causing a large electric current to flow. This phenomenon is glow discharge.

This current (flow of secondary electrons) has enough energy to excite the neon atoms in the glass tube. As the excited atoms return to their ground state, they emit light with a wavelength corresponding to the energy difference between the energy bands. In the case of neon atoms, this light is observed as red light.

2. Characteristics of Glow Discharge

When glow discharge begins, some of the gas is ionized and generates more electrons. When this is repeated, an electron avalanche causes a steady current of about 0.1~10 mA to flow between the electrodes. The sustained discharge in a low-pressure gas is a characteristic of glow discharge.

The glow discharge start voltage in neon lamps is about 70 V and the discharge end voltage is about 60 V. A stable voltage must be supplied to continue stable discharge. Therefore, like fluorescent lamps, neon lamps are generally used in combination with ballasts.

Further raising the voltage between the electrodes results in an arc discharge, which makes neon gas more unstable. The light observed at this point changes to a blue-white color. Arc discharges generate very high heat, as evidenced by their use in arc welding, so care must be taken.