1. Metal reinforcing screens are used to reduce exposure time and reduce the influence of scattered radiation. The amplifying effect of metal screens is based on the exposure of the film to secondary electrons knocked out by photons from the thin foil of the metal screen. Since the range of these electrons is very short, they are almost completely absorbed by the film, thereby increasing its darkening density. Due to the short range of electrons, image blurring does not occur, i.e. enhancing the image image is not accompanied by a loss of its quality. In addition to reducing exposure time, lead intensifying screens significantly reduce the negative effect of scattered radiation on image quality.
The gain factor of lead screens is in the range of 1.5-3 (the gain factor of screens is understood as a value showing how many times the exposure of transillumination is reduced when using a given screen). Metal screens are made of lead or lead-tin alloys in accordance with GOST 18394-73 and GOST 9559-75. The thickness of metal screens is selected depending on the application. A table with recommendations for choosing the thickness of screens is contained in Table 6-13 of the educational manual “Radiographic testing of welded joints”
2. Fluorescent intensifying screens are also used to reduce exposure time. The amplifying effect of fluorescent screens is based on their conversion of part of the x-ray radiation into an optical layer of phosphor. The gain of fluorescent screens is significantly higher than that of lead screens and is in the range of 20-30. The downside to the significant reduction in exposure when using fluorescent screens is a significant loss in contrast sensitivity, i.e. quality of control. The reason for this is the very large grain size of the phosphor. So, if the average grain size for screenless X-ray film is no more than 0.5 microns, for screen film - 1-1.5 microns, then for screens it is about 10 microns. Adding lead screens to fluorescent screens always increases the contrast of the X-ray image, but at the same time increases the exposure time.
This type of screen is usually used with films that have increased sensitivity in the visible region of the spectrum such as Fuji IX 100HD, AGFA F8, KODAK HS800. Fluorescent screens are made of plastic or cardboard, on one side of which a layer of phosphor is applied. The compounds used as phosphors are ZnS, CdS, PbSO4, CaWO4, BaSO4, etc. Due to the reduced resolution of radiographic images obtained using fluorescent screens, their use is not permitted in radiographic inspection of highly critical welds, for example, in nuclear power.
3. Fluorometallic intensifying screens. Currently, fluorometallic intensifying screens, which are a unique combination of the two types described above, are becoming increasingly widespread. Fluorometallic screens are made in the form of a lead substrate with a layer of phosphor applied to it. These screens have a higher gain than metal ones, while providing better sensitivity compared to fluorescent ones. Modern fluorometallic intensifying screens include, for example, AGFA RCF and SMP-1
Agfa NDT reinforcing screens are used for testing thick-walled products, allowing to significantly reduce inspection time and increase the service life of pulsed devices. Agfa NDT screens include the high-speed fluorescent screen NDT 1200 and the fluorometallic screen RCF.
Agfa intensifying screens are made using calcium tungstate (CaW04), which fluoresces blue when exposed to ionizing radiation. The flexibility of the screens greatly simplifies the radiography of curved objects. Additional protection from external influences is provided thanks to a special coating.
Agfa NDT screens are usually supplied in pairs, 30x40cm or other formats. Screens can be cut to obtain the required formats. Upon request, it is possible to supply screens for roll film. Agfa RCF and NDT-1200 intensifying screens are recommended for use with Agfa F8 radiographic film. The use of these screens with RT-1 radiographic film, or the use of Russian-made screens with F8 film, does not allow effective reduction of exposure due to the inconsistency between the emission spectrum of the screens and the absorption spectra of the films.
Features and properties of the AGFA 1200 intensifying screen. The AGFA NDT 1200 fluorescent screen has extremely high absorption capacity combined with acceptable image detail visibility. The AGFA F8 or F6 film combination is particularly suitable for applications where high radiation energies are required, for example for the inspection of heavy metal or concrete structures. The AGFA NDT 1200 screen is also effective for monitoring with pulsed devices and for microfocus technology, when radiation doses are very low.
Features and properties of the AGFA RCF intensifying screen. The AGFA RCF screen has a built-in lead oxide filter for scattered radiation. With standard use of AGFA NDT RCF screens in combination with AGFA NDT F8 film, significant time savings are achieved. The AGFA RCF fluorescent screen is the optimal compromise between detail visibility and operating speed. The protective coating (EBC/Elektron-BeamCured) and the polyester base make the screen especially durable. AGFA RCF reinforcing screens can be used, among other things, for inspection of offshore pipelines.
Storage and operating conditions. AGFA NDT screens must be protected from dampness, high temperatures and ultraviolet radiation. Dust and stains should be removed from the screen with a special cleaner. A cleaner containing an antistatic agent not only cleans the screen, but also prevents dirt and dust caused by static electricity from sticking to the screen.
Relative exposure factor. When exhibiting using fluorescent screens, it is important to consider the influence of temperature, radiation energy and exposure time. Thus, the effectiveness of the screens decreases as the ambient temperature increases. As the radiation energy increases, the absorption of fluorescent screens decreases and, as a result, the amplification effect decreases. Due to the effect characteristic of fluorescent screens, the enhancing effect of the latter, compared to lead screens, decreases with increasing exposure time. The relative exposure factors of intensifying screens are presented in the following table
| Power/radiation source | Screen type | Agfa film type | ||
| F8 | F6 | D7 | ||
| 100 kB | NDT 1200 | 0.010 | 0.049 | |
| RCF | 0.030 | 0.174 | ||
| Without screen | 1.000 | |||
| 300 kB | NDT 1200 + Pb | 0.008 | 0.042 | |
| RCF | 0.022 | 0.132 | ||
| Pb | 1.000 | |||
| Iridium 192 | NDT 1200 + Pb | 0.007 | 0.063 | |
| RCF | 0.035 | 0.389 | ||
| Pb | 1.000 | |||
| Cobalt 192 | NDT 1200 + Pb | 0.006 | 0.096 | |
| RCF | 0.040 | 0.562 | ||
| Pb | 1.000 | |||
Reinforcing screens RENEX UPV are used to reduce exposure time and reduce the influence of scattered radiation. RENEX screens are manufactured in Russia and are adapted to work in the temperature range from - 30° C to + 50° C without loss of photographic and mechanical properties. In the production of screens, a flexible polyester substrate and a durable protective coating are used. When watering screens, the best X-ray phosphors from the world's leading manufacturers are used.
The following types of Renex intensifying screens are currently available:
- RENEX UPV-1 PRS—Fluorescent screens with increased resolution. The screens are made of highly efficient fine-grained x-ray phosphor - calcium tungstate using a special dye that effectively absorbs scattered light radiation formed in the phosphor layer. Thanks to this technology, the screen resolution is increased to 6.00-8.00 line pairs/mm (depending on radiography conditions)
- RENEX UPV-1, RENEX UPV-2— fluorescent screens for general purposes. Standard intensifying screens for flaw detection, produced since 2002. They have proven themselves to be excellent in various fields of application and are made of highly efficient fine-grained X-ray phosphor - calcium tungstate with the addition of terbium-activated yttrium oxysulfide (UPV-2).
- RENEX UPV-3 VU— fluorescent screens of high gain and increased brightness. The screens are made of ultra-efficient fine-grained x-ray phosphor - barium fluorobromide, activated by europium. In terms of amplification, resolution, and detailed sensitivity, RENEX UPV-3 VU screens are 100% analogous to screens from foreign manufacturers: KYOKKO SUPER SPECIAL.
Renex intensifying screens are available in the following formats - 30x40cm, 8x30cm, 8x40cm, 10x30cm, 10x40cm. Screens of any format (length up to 5 m, width up to 40 cm) are manufactured upon special order. The technical characteristics declared by the manufacturer of Renex intensifying screens are given in the table.
| Characteristic | Marking | Resolution, line pairs/mm | Sensitivity of the combination of fluorescent screens with films RT-1, HS800, in R-1 | Exposure conversion factor when moving from RT-1 film (HS800) to a combination of fluorescent screens with RT-1 film | ||
| front screen | back screen | |||||
| Fluorescent screens with increased resolution have no foreign analogues. | RENEX UPV-1 PRS | 6.00 - 8.00 | 100 | 30 | 40-45 | 40-45 |
| General purpose fluorescent screens that have no foreign analogues. | RENEX UPV-1 | 3.50-4.00 | 350 | 100 | 45-50 | 45-50 |
| High gain and high brightness fluorescent screens | RENEX UPV-2 | 3.00-3.50 | 620 | 180 | 65-70 | 65-70 |
| Analog – KyokkoHighPlus | 3.00-3.50 | 650 | 200 | 45-50 | 65-70 | |
| RENEXUPV-3 VU | 3.20-3.80 | 1200 | 350 | 50-60 | 50-60 | |
| analogueKyokko Super special | 3.20-3.80 | 1200 | 350 | 50-60 | 50-60 |
All measurements of the characteristics of fluorescent screens were carried out under the following exposure conditions:
- voltage on the X-ray machine tube is 220 kV;
- additional filter 25 mm Fe + 2 mm Cu;
- focus - 3 mm;
- focal length -100 cm.
- The current and exposure time were selected to ensure a film blackening density of 2.00 D.
To determine the resolution, lead mira, type L 659037, 80 μm thick, was used. S. The sensitivity of technical radiographic films of the RT-1, HS800 type (according to TsNIITMASH) is 3.3-3.5 R-1. Fluorescent screens for industrial flaw detection RENEX UPV are intended for joint use with technical radiographic films, the sensitization of the emulsion layer allows the use of intensifying screens with emission in the ultraviolet, violet and blue regions of the spectrum. Today such films are: RT-1; RT-1V; RT -1TN; Kodak HS 800; Agfa F8.
Metal (lead) reinforcing screens are used to reduce exposure time and reduce the influence of scattered radiation. The amplifying effect of metal screens is based on the exposure of the film to secondary electrons knocked out by photons from the thin foil of the metal screen. Since the range of these electrons is very short, they are almost completely absorbed by the film, thereby increasing its darkening density. Due to the short range of electrons, image blurring does not occur, i.e. enhancing the image image is not accompanied by a loss of its quality. In addition to reducing exposure time, lead intensifying screens significantly reduce the negative effect of scattered radiation on image quality.The gain factor of lead screens is in the range of 1.5-3 (the gain factor of screens is understood as a value showing how many times the exposure of transillumination is reduced when using a given screen). Metal screens are made of lead or lead-tin alloys in accordance with GOST 18394-73 and GOST 9559-75. The thickness of the metal screens is selected depending on the source of ionizing radiation used and the voltage on the X-ray tube.
The thickness of metal reinforcements is selected in accordance with the table
| Radiation source | Screen thickness, mm | |
| recommended | acceptable | |
| X-ray machine with X-ray tube voltage up to 100 kV | up to 0.02 | 0,02-0,09 |
| X-ray machine with X-ray tube voltage from 100 kV to 300 kV | 0,05-0,09 | |
| X-ray machine with X-ray tube voltage over 300 kV | 0,09 | |
| Thulium - 170 | 0,09 | 0,02-0,09 |
| Selenium - 75 | 0,09-0,20 | 0,05-0,02 |
| Iridium - 192 | 0,20-0,30 | 0,05-0,30 |
| Cesium | 0,30-0,50 | 0,09-0,50 |
| Cobalt - 60 | 0,30-0,50 | 0,20-0,50 |
1. To prevent sample movement.
2. To increase the contrast of the subject.
- Used as a compensator.
- To protect the film from scattered radiation.
33. The use of metal screens (foil) reduces exposure time due to:
1. Fluorescence foil.
2. Absorption of scattered radiation.
3. Absorption of backscattered radiation.
- Converting an X-ray (gamma) image into an electronic one, recorded by film, is more efficient than the original one.
34. Reinforcing metal screens reduce exposure time. In addition they:
1. Reduce the amount of geometric blur.
2. Radiation scattered by the controlled product is filtered.
3. Reduce the graininess of the image.
- Increase the intensity of radiation.
35. Metal reinforcing screens:
1. Reduce exposure time.
2. Reduce the amount of scattered radiation reaching the film.
3. Simultaneously both 1) and 2).
4. Neither 1), nor 2).
36. In industrial radiography, fluorescent screens are used for:
1. Improved clarity of radiographic images.
2. Improvements in radiographic image contrast.
3. Reducing exposure time.
- All of the above are true.
37. A fluorescent screen in film radiography is used in conjunction with:
1. With extra fine-grained radiographic film.
2. With any radiographic film.
3. With color radiographic film.
4. With sensitized radiographic film.
38. The blurring of an image, the magnitude of which depends on the focal spot of the source, the focal length and the distance between the sample and the film cassette, is called:
1. Dynamic blur.
2. Geometric blur.
3. Claessens effect.
4. Own blur.
39. Geometric blur of a radiographic image:
1. Proportional to the distance between the subject and the film and inversely proportional to the size of the focal spot.
2. Proportional to the size of the focal spot and the distance between the subject and the film.
3. Inversely proportional to the distance between the subject and the film and directly proportional to the focal length.
4. Inversely proportional to the size of the focal spot and the distance between the subject and the film.
40. To reduce the contrast of a photo, you must:
1. Increase the distance between the source and the controlled object.
2. Reduce the distance between the object and the film.
3. Use a source with harder radiation.
- Use a source with soft radiation.
41. A condition for obtaining clear images should be considered:
1. The focal spot of the radiation source should be as small as possible.
2. The focal length should be as long as possible.
3. The film cassette must be located close to the product being tested.
- All of the above are true.
42. The reason for the blurred image may be:
1. Long focal length.
2. Long exposure time.
3. Depletion of fixer.
4. Use of fluorescent screens to reduce exposure time.
- All of the above are true.
43. During radiographic testing, exposure time:
1. Depends exponentially on focal length.
2. Directly proportional to focal length.
3. Proportional to the square root of the focal length.
4. Proportional to the square of the focal length.
44. You can increase the contrast of the image image:
1. Increasing focal length.
2. Reducing the X-ray tube current.
3. By lowering the accelerating voltage on the X-ray tube.
- Increasing the size of the focal length.
45. The exposure time depends on the value of the anode current of the X-ray tube:
1. Directly proportional.
2. Inversely proportional.
3. Inversely proportional to the square of the anode current.
4. Doesn't depend.
46. Exposure time depends on:
1. A type of radiographic film.
2. Charging circuits for cassettes.
3. Focal length.
4. Exposure dose rates.
5. All of the above are true.
The sensitivity of the image obtained using X-rays turned out to be worse than required by regulatory documentation for assessing the quality of an X-rayed product. How can you increase the sensitivity of a photo?
1. Using fluorescent screens.
2. Using radiographic film that is more sensitive to radiation.
3. Using a more contrasting film.
4. By lowering the anode voltage on the X-ray tube.
- Structure and characteristics of the intensifying screen
- Screen-film combination
- Structure and characteristics of radiographic film
- Screening grid
- Developing machine
- Dark room and X-ray viewer
- Image Options
Introduction to the basics and elements of the radiographic system
A layer of material placed close to the film in conventional radiography to:
Convert incident X-rays into radiation that is better perceived by the X-ray film emulsion ( ren. rays light photons)
Reduce patient exposure required to achieve a given level of film blackening
Reduce exposure time and X-ray generator power (price reduction)
Increase photoelectric effect better utilization of radiant energy (imaging)
Base (mostly polyester used)
- Chemically neutral, x-ray resistant, flexible, very smooth
Reflective layer (titanium dioxide - TiO2)
- Crystalline compound that reflects photons to the film emulsion
Luminescent layer (polymer)
- Crystals located in a suspension of plastic material
Protective covering
- Colorless thin film that protects the luminescent layer when using the screen
Luminescent layer
Luminescent layer (luminophore crystals) should:
- absorb x-rays as much as possible
- convert x-rays into light
- match the emission spectrum of the film sensitivity
Material type:
- Calcium tungstate (CaWO4) (before 1972)
- rare earth elements (since 1970) (LaOBr:Tm) (Gd2O2S:Tb) more sensitive and effective than (CaWO4)
UV
UV(Gain Factor): ratio of exposures that produce the same optical density with and without a screen
CEP(Quantum Absorption Efficiency): the fraction of photons absorbed by the screen
- 40% for CaWO4
(Conversion factor): ratio of the energy of light rays to the absorbed energy of x-rays (%)
- 3% for CaWO4
C (Absorbance Coefficient): Ratio of energy absorbed by film to luminous energy (%)
- C maximum for screens with an emission spectrum in the ultraviolet region 90%
Gain factor: the ratio of exposures that produce the same optical density with and without a screen
Sensitivity blackening density
Sensitivity(screen-film): Quotient of K0/Ka, where K0 = 1 mGy and Ka is KERMA in air for blackening density D = 1.0, measured in the film plane
Screen-film system: A specific intensifying screen with a specific type of film
Sensitivity class: a certain range of sensitivity values for the screen-film system
Single-sided emulsion film: film coated on one side, used with one screen
Double-sided emulsion film: film coated on both sides, used with two screens
Screen film contrast quantum noise
Spatial resolution
Spatial resolution: the ability of a screen-film combination to make nearby objects visible in the image. Resolution can be assessed using world: periodic structures (pairs of lines) with different frequencies
Modulation transfer function(FPM): characteristic of the dependence of the image contrast of a sinusoidal structure on frequency during X-ray optical conversion
Noise spectrum: noise component due to the amplification system (screen-film)
- Quantum noise, screen noise, grain.
Quantum absorption efficiency(CEP): fraction of x-ray photons absorbed by the screen-film system
Depending on the requirements for resolution and sensitivity, different types of screens are used (different grain size and photographic effect)
Poor contact between screen and film
- loss of spatial resolution
- blurry image
Image clarity
Resolution depends on crystal size and screen thickness
The resolution of radiography on film without screens is better, but requires approximately 40 times the radiation dose
Without screen - ~50 p.l./mm, conventional screens ~10 p.l./mm, “fast” screens ~6 p.l./mm, mammography systems ~15 p.l./mm
Protective layer (outer surface)
Sensitive layer (~20 µm)
Base (transparency and mechanical strength) (~170µm)
Bonding layer
Sensitivity characteristics
Protective coating – protects against scratches
The basis
- is relatively thick and gives the film hardness and flexibility
- is almost transparent
Emulsion
- image layer, consists of gelatin and silver halogen (Br, I)
- Sensitivity, contrast and resolution depend on the composition of the emulsion
A latent (invisible) image formed by the interaction of photons of light with halogen ions in the crystal, which:
- lose electrons
- electrons go to silver ions
- neutral silver atoms appear in the crystal
Manifestation
Manifestation
- Converts a hidden image into a visible image by turning silver ions into metallic silver
Fixing
- Dissolves unexposed silver halogen crystals, leaving only metallic silver, forming a permanent image
Changing film sensitivity depending on light
Orthochromatic film is usually sensitive to blue or blue-green light
The screen glows blue (calcium tungstate) or green (rare earth) light
“Safe” light should not illuminate the film.
In a film with a double-sided emulsion, the screen light can illuminate the emulsion on the opposite side
This phenomenon reduces image resolution
To limit the internal transition, a light-absorbing layer is applied
The straight part of the characteristic curve is difficult to determine, so the average gradient is measured between OD=0.25 and 2.0
OD 2.0 is used because only 1% of the light passes through at this level, and the image will still be visible when using a X-ray viewer
OD 0.25 is used because at this density the eyes can still distinguish 10% contrast, and at a lower density this contrast no longer differs
Contrast is usually measured as the average gradient
You can also measure the slope of a line drawn between points OD = 1.2, i.e. net OD=1.0 (without base and veil) and
OD = 2
Base+veil
Base+veil: Film OD resulting from incomplete transparency of the base and the action of the developer on non-irradiated film; usually 0.15 -0.25.
Sensitivity (speed): the reciprocal of the exposure required to achieve net OD =1.0
Gamma (contrast): gradient of the straight section of the characteristic curve
Latitude: The steepness of the characteristic curve, which determines the range of doses at which an image of acceptable quality is formed
Radiation leaving the patient's body
- primary beam: forms an image
- scattered radiation: reaches the detector, but reduces contrast and increases patient dose
The grid (between the patient and the film) filters out most of the scattered radiation
Stationary grille
Movable grid (best performance)
Focused grating
Potter-Bucca system
Lattice ratio
Lattice ratio
- Ratio of the height of the plates to the width of the spaces near the center line
Contrast enhancement ratio
- Ratio of primary and total radiation passing through the grating
Exposure factor
- Ratio of total radiation dose rates at a certain point with and without a grating
Number of plates
Number of plates
- Number of absorbing plates (lamellas) per 1 cm
Grille focal length
- The distance between the line in which the extensions of the planes of the absorbing plates converge and the surface of the raster (grating) directed towards the emitter
Constant temperature
Constant temperature
Constant processing time
Automatic chemical replenishment
Film drying
Can cause artifacts
The most important attributes of QC:
The most important attributes of QC:
- proper storage of films
- Caring for the cassette and screen
- Chemical control
- sensitometry
- artifacts
- CPU cleaning
Sensitometer and densitometer required
It is essential to keep film processing under daily control
Main parameters for control:
- base + veil
- speed
- gradient (gamma)
- contrast
Use a sensitometer to expose the film to light through a special stepped wedge
Make sure that the side of the emulsion film (for single-sided coating) is facing the light source
Select the correct light (green, blue) for sensitometry and expose the film to a special signal
Develop the film immediately
Before measuring step filter optical densities, the reference strips should be visually inspected to ensure that there are no errors in the procedure, such as exposure to different colors or exposure from the base side instead of the emulsion.
Mark the optical densities of the wedge steps on graph paper
The values of fog, maximum density, sensitivity and average gradient can be determined based on the characteristic curve (dependence of optical density on light exposure)
There are many medical facilities where X-ray film is processed manually in open tanks, sometimes under very poor conditions.
Manual processing can be effective, BUT it can cause many problems with image quality
Film processing stages:
Film processing stages:
- manifestation
- rinsing in water
- fixation (fastening)
- rinsing in water
Washing in water is very important to remove chemical residues and get good pictures.
Temperature – constant and optimal
Processing time control
Developer activity (chemical state) – fresh and unoxidized
Developer temperature should be around 20oC (or as recommended by the manufacturer)
Use a thermometer regularly to check your temperature
If the developer is too cold, the film will not develop.
If the developer is too warm, processing will be too fast and poorly controlled.
container with water(as heat protection)
Ideally, the developer and fixer containers should be surrounded by container with water(as heat protection)
Container with water must be heated (or cooled) to 20oC
It's best to use a thermostat
However, hot or cold water can be added to the container to maintain the desired temperature
These requirements are sometimes impossible to meet (in Africa, Asia,...)
If the developer temperature is constant and known, then the standard development time should be used
Ideally it is about 3 minutes
The exact time must be determined from the time-temperature graph
A large clock visible in low light should be used
An experienced operator can determine development time by looking at the films under "safe" light towards the end of processing.
- However, at the same time the density of the veil increases
"Safe" light
"Safe" light
- quantity (smallest), distance from the table
- filter type and color
- color of the bulb (red or adapted to the film)
- power (
Protection from external light
Hydrometry (30 - 60%)
Room temperature
Film storage conditions
Density
Density
Contrast
Permission
Blur
Distortion
MTF (modulation transfer function)
The main components of the radiographic system and their purpose are explained:
- Characteristics of conventional film and screen-film combinations
- Necessary conditions for film processing, dark room and viewing images on a X-ray viewer
Intensifying screens are used to increase the sensitivity of films to X-ray radiation and, accordingly, reduce the transillumination time.
There are two types of intensifying screens - metal and fluorescent (fluorescent).
The amplifying effect of metal screens is based on exposure of the film to secondary electrons knocked out of the thin foil (lead or lead-tin) of the screen by x-ray photons. Due to the very short range, these electrons are almost completely absorbed by the film, which increases the density of its darkening. In this case, image enhancement does not lead to loss of its quality in the form of blurring.
Depending on the X-ray energy, the gain of metal screens can reach 2-2.5. Screens (a pair) are used together with x-ray film, placing them on both sides of it, which doubles their impact.
At the Rentgenservice company you can buy lead intensifying screens of the following standard thicknesses: 0.05 mm; 0.1 mm; 0.2 mm.
In turn, the main difference between fluorescent screens and metal ones is the use of a special substance - a phosphor, which converts part of the x-ray radiation into the optical substance of the screen. While the film absorbs about 1% of the X-ray radiation that reaches it, the screen has a significantly higher absorption capacity (up to 20%), and the glow that occurs in it is almost completely absorbed by the film. Therefore, the gain factors of fluorescent screens are very high (several tens or more). However, along with a significant reduction in exposure, there are no less significant losses in contrast sensitivity due to the very large grain size of the phosphor (about 10 microns, while the average grain size of screenless X-ray film is no more than 0.5 microns, screen film - 1- 1.5).
Like metal ones, fluorescent screens are used in a set of two screens (front and rear) in the closest possible contact with the film. The thickness of the rear screen is usually greater than the thickness of the front screen, due to the fact that its glow directed towards the film is less attenuated by its own absorption. In this case, as a rule, fluorescent screens are used with types of films specially designed for them.
You can buy fluorescent intensifying screens from the following brands: (Russia), (Japan), (Japan).
In recent years, a type of screen has appeared that is a kind of hybrid of the two described above. These are fluorometallic screens that combine a layer of lead foil and a layer of phosphor. The advantage of such screens is that they provide a significant reduction in exposure during monitoring and at the same time do not degrade (or slightly reduce) the image quality. Such screens were first produced in Japan in the 80s under the name, and some time later by Agfa-Gevaert under the name RCF. The latter also released two types of films specifically designed to work with this screen −
The Non-Destructive Control company offers a wide range of intensifying screens made in Russia and abroad.
Metal screens
In most cases, metal screens are made of lead, less often - of copper, tungsten or tantalum. Compared to fluorescent screens, metal screens require longer exposure times, but at the same time increase image quality by increasing contrast. The effectiveness of a metal screen depends on the thickness and exposure radiation, as well as on the properties of the photographic material with which it is used. The highest gain is observed when using metal screens with coarse-grained materials.
Lead reinforcement screens, Germany. Use with non-sensitized films (D2, D3, D4, D5, D7 and D8). Thickness range from 0.02 to 0.16 mm. The thickness of the screen is selected depending on the required gain. Screens of the series are supplied in sheets or in packages.
Fluorescent screens
Fluorescent screens consist of a substrate and a phosphor layer, due to which they acquire high absorption capacity (the proportion of absorbed energy reaches 20%) and significantly reduce exposure time. At the same time, the sharpness of the image is lower than that of metal screens. Fluorescent screens are produced as a set of front and rear screens, with the rear being thicker than the front.
UPV series screens on a flexible polyester substrate using a fine-grained phosphor. The series includes standard intensifying screens UPV-1 and UPV-2, as well as the UPV-3 VU model with increased brightness. Manufactured formats: 30x40 cm, 8x30 cm, 8x40 cm, 10x30 cm and 10x40 cm. All screens are recommended for use with technical films of the RT-1 type.
Agfa NDT 1200. Screens on a plastic base with calcium tungstate phosphor. NDT 1200 is used when inspecting thick-walled structures or concrete structures. Exposure time is reduced by up to 150 times. NDT 1200 screens are recommended for use with Agfa F8 films.
Metal fluorescent screens
Metal fluorescent screens appeared relatively recently (in the eighties) and combine the advantages of metal and fluorescent screens. They include a layer of phosphor and a layer of lead foil, which makes it possible to reduce exposure time without compromising image quality.
ScreensKyokko on a plastic basis are used to control welded joints and metal products. The screen format is 30x40 cm. All screens are recommended for use with technical films of the Agfa F8 type.
Agfa NDT RCF. Screens on a plastic base with calcium tungstate phosphor and a protective coating. NDT RCF is used for testing thick-walled structures. Also, due to their flexibility, they can be used when inspecting pipelines and curved parts. Exposure time is reduced by up to 40 times. NDT 1200 screens are recommended for use with Agfa NDT F8 and Agfa NDT F6 films. RCF screens are available in 10x24 cm, 10x48 cm and 30x40 cm formats.
SMP series screens based on a highly reflective polymer base, they are used for inspecting pipe surfaces at subzero temperatures. Lead foil in the screens provides high contrast and sharpness of the image. SMP screens are used with both pulsed X-ray devices and constant potential devices. The series screens are recommended for use with Agfa F8 and R8F films.
Sales consultants will help you select an intensifying screen suitable for your tasks and control objects.
We will deliver to all cities of Russia, as well as to the CIS countries and the Customs Union (Kazakhstan, Belarus, Ukraine, Tajikistan, the Republic of Moldova, Kyrgyzstan).