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ZnS:Ag PHOSPHOR POWDER

EJ-600

 

EJ-600

 

Silver activated zinc-sulfide, ZnS:Ag, is a free-flowing white fluorescent powder having exceedingly high scintillation efficiency. It is primarily used for alpha particle detection. The most common detector format is a thin flat plate of inert glass or plastic to which the ZnS:Ag is affixed in a thin uniform layer on one side. Such scintillating screens provide very high intrinsic detection efficiency for alpha particles while having very low sensitivity for beta particles and gamma rays.

 

PROPERTIES EJ-600
Phosphor Type Blue
Light Output (% Anthracene) 300
Wavelength of Maximum Emission (nm)
450
Decay Time (ns) 200
Density (g/cm3) 4.09
Refractive Index 2.356
Melting Point (°C) 1850
Typical Particle Size (μm, nominal) 8

 

 

EJ-600 Emission Spectrum

 

ALPHA/BETA DETECTION

EJ-444

 

 

EJ-444 consists of a thin piece of EJ-212 plastic scintillator with a layer of silver activated zinc sulfide phosphor (ZnS:Ag) applied to one side. The primary use of EJ-444 is the detection of alpha and beta particles in health physics instrumentation. A non-coated plastic scintillator may also be used for this purpose, but the amplitudes of the alpha and beta pulses are sufficiently similar to make it difficult to separate the two by simple counting electronics making use of counting windows. In contrast, the ZnS:Ag layer on the EJ-444 is made just thick enough to stop all common alpha particles while allowing many low energy betas to pass into the plastic scintillator layer for detection. C-14 betas may be detected with moderate efficiency.

The plastic scintillator component is usually kept quite thin in order to minimize gamma sensitivity. This allows even energetic betas, such as those from P-32 and SrY-90, generate pulses grouped in a fairly narrow amplitude region that is below the amplitudes of over 95% of the alpha pulses generated in the ZnS:Ag layer.  The standard thickness in EJ-444 is 0.25 mm, but it is also available in greater thicknesses of which 0.5 mm and 1 mm are typical. Thicknesses less than 0.25 mm are also available. The EJ-444 alpha detection efficiency is essentially the same as achieved with bare plastic scintillator.

To give an indication of the beta detection efficiencies of EJ-444, counting comparisons were made between bare 0.25 mm thick EJ-212 and EJ-444 made with an identical EJ-212 component. The bare plastic scintillator is considered to be a reliable reference for maximum detection of the radioactive particles investigated. The results are highly uniform from batch to batch, and typical values are presented below.

 

PROPERTIES EJ-212 ZnS:Ag
Light Output (% Anthracene) 65 300
Wavelength of Maximum Emission (nm)
423 450
Decay Time (ns) 2.4 200
Density (g/cm3) 1.023 -
Phosphor Density (mg/cm2)  - 3.25 ± 0.25

 

RADIATION TYPE RELATIVE EFFICIENCY
EJ-444 count ÷ EJ-212 count
C-14 Beta (Emax = 156 keV) 66%
Tc-99 Beta (Emax = 294 keV) 80%
SrY-90 Beta (Emax = 544 keV, 2.3 MeV) 96%

 

EJ-444 Emission Spectra

ALPHA DETECTION

EJ-440, EJ-442

 

EJ-440

 

These products consist of a very uniform deposit of blue-emitting P22 type silver activated zinc sulfide phosphor (ZnS:Ag) applied to one side of a backing material. They are specifically intended for alpha particle detection, and the phosphor layer density is sufficient to completely absorb common alpha particles such as those from 241Am. Batch to batch uniformity of alpha sensitivity is constant within a ± 1.5% range. The phosphor layer is smooth and sufficiently robust to withstand normal handling.

EJ-440 consists of ZnS:Ag phosphor applied to a clear polyester plastic sheet. The sheets are quite flexible and can easily be cut with scissors or a paper cutter.

EJ-442 consists of ZnS:Ag phosphor applied to one side of a thick, non-flexible support material. This product is custom-made to satisfy each customer's specific requirements. The most common support materials are acrylic plates, but metal support plates have also been used. These materials are very stable, and their shelf life at room temperature is at least two years.

 

 PROPERTIES EJ-440
EJ-442
 Light Output (% Anthracene) 300
 Wavelength of Maximum Emission (nm) 450
 Decay Time (ns) 200
 Phosphor Density (mg/cm2)  3.25 ± 0.25 
 EJ-440, Thickness of Polyester Film (mm) 0.25
 EJ-440, Density of Polyester Film (mg/cm2
36
 
Chemical Compatibility
The adhesive is soluble in common alcohols and other organic solvents. It is insoluble in water. 

  EJ-440 & EJ-442 Emission Spectrum

ZINC SULFIDE COATED

SHEETS AND DISCS

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Zinc Sulfide Coated Products

 

Eljen Technology offers three different zinc sulfide (ZnS:Ag) coated products for alpha or alpha/beta detection. EJ-440 and EJ-442 are products designed specifically for alpha detection. EJ-440 consists of a polyester sheet coated with ZnS:Ag while EJ-442 consists of a non-flexible support material coated with ZnS:Ag. EJ-444 is designed for alpha/beta detection and discrimination and consists of a thin sheet of EJ-212 plastic scintillator coated with ZnS:Ag.

 

ZINC SULFIDE COATED PRODUCTS

Material Description/Applicaton
Commercial
Equivalents
NE S-G
EJ-440 ZnS:Ag coated 0.25mm thick polyester sheets and discs - -
EJ-442 ZnS:Ag coated acrylic plastic or glass - -
EJ-444 ZnS:Ag coated EJ-212 plastic scintillator - -
EJ-600 ZnS:Ag phosphor powder - -

New Products

Plastic Fibers

Scintillation and Wavelength Shifting Plastic Fibers

Eljen Technology is proud to introduce our own brand of plastic fiber optics that are designed for applications needing fiber optics and flexibility. Our fibers are offered in plastic matrix bases of polyvinyl toluene (PVT) or polystyrene (PS) and in formulations based on standard Eljen scintillation and wavelength shifting plastics.

EJ-270

Lithium-6 Loaded PSD Plastic Scintillator
EJ-270

This new scintillator contains Lithium-6 and is formulated to provide pulse shape discrimination (PSD) to detect and identify fast neutrons, gammas, and thermal neutrons.

Non-Fogging Plastic

Non-Fogging Plastic Scintillators:
EJ-200NF and EJ-208NF

Designed specifically for outdoor detector systems, these scintillators can withstand the stresses of large temperature variations and moisture absorption that eventually lead to fogging and reduced detector performance in conventional plastic scintillators.

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