Engineering Overview

SP121 Plastic Scintillators

SP121 Plastic Scintillator is an SP102 polystyrene-based scintillator coated with 4.5 mg/cm2 ZnS(Ag), designed for dual alpha and beta radiation measurement. The ZnS(Ag) coating detects alpha particles, while the SP102 substrate supports beta detection for surface contamination detector assemblies.

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SP121 Alpha Beta Plastic Scintillator for Surface Contamination Detection

SP121 Plastic Scintillator is a coated plastic scintillator designed for dual alpha and beta radiation measurement. It uses an SP102 polystyrene-based plastic scintillator as the substrate and a controlled ZnS(Ag) coating layer for alpha response. In this structure, the ZnS(Ag) coating is responsible for alpha detection, while the SP102 substrate supports beta-particle detection.

The standard SP121 coating thickness is 4.5 mg/cm2. Because alpha particles have a very short penetration range, coating density, surface uniformity, detector window and protective layer design must be reviewed carefully. The beta response depends on SP102 thickness, source energy, detector geometry, optical coupling, sensor sensitivity and electronics.

ATR Crystal supplies custom SP121 scintillator screens and panels for surface contamination detectors and alpha/beta monitoring instruments. Panel dimensions, active area, SP102 thickness, ZnS(Ag) coating, readout method, light-guide structure, wrapping, housing and inspection requirements can be reviewed according to your instrument design.

Applications of SP121 Plastic Scintillators

Alpha/beta surface contamination detectors

Portable radiation survey instruments

Radiological protection and contamination monitoring

Laboratory alpha/beta counting assemblies

Custom coated scintillator detector panels

Prototype detector modules requiring dual particle response

Advantages of SP121 Alpha Beta Scintillator Screens

Dual alpha/beta measurementThe ZnS(Ag) layer provides alpha response, while the SP102 plastic scintillator substrate supports beta detection.
Controlled ZnS(Ag) coatingThe 4.5 mg/cm2 coating is designed for alpha-particle absorption and scintillation response in surface contamination monitoring.
Fast SP102 substrateThe SP102 substrate provides a 423 nm emission peak and 2.4 ns decay time, supporting fast beta detection designs.
Good uniformityCoating uniformity and substrate quality can be specified to support consistent response over the active area.
Custom panel formatsCustom active area, substrate thickness, edge margin, panel shape and mounting features can be reviewed with drawings.
Detector integration supportSP121 can be reviewed with PMT, SiPM, photodiode, light-guide, reflector, wrapping and housing requirements.

SP121 Structure and Detection Function

SP121 is a layered alpha/beta scintillator structure. The coated side, detector window and optical readout must be defined clearly for practical detector design.

Layer / Item	Function	Design Notes
ZnS(Ag) coating	Alpha-sensitive scintillating layer	Standard coating surface density is 4.5 mg/cm2. The coated surface should face the alpha source unless the detector design specifies otherwise.
SP102 substrate	Beta-sensitive plastic scintillator base	SP102 supports beta-particle detection and provides mechanical backing for the coated screen.
Coated side	Defines alpha response direction	Alpha particles are easily stopped by thin materials, so any window, film or protective layer must be reviewed.
Optical readout	PMT, SiPM, photodiode or optical module	The sensor should match emission around 423 nm from SP102 and 450 nm from ZnS(Ag).
Signal handling	Instrument-level alpha/beta measurement	Electronics, threshold settings and calibration determine how alpha and beta signals are interpreted.
Panel format	Custom plate, screen or detector panel	Active area, total size, substrate thickness, mounting holes and edge margin should be defined in the drawing.

Properties of SP121 Plastic Scintillators

The following values are based on the original SP121 product data. Final specifications depend on substrate thickness, coating process, active area and inspection method.

Property	SP102 Substrate	ZnS(Ag) Coating
Material	SP102, polystyrene-based plastic scintillator	ZnS(Ag)
Density	1.023 g/cm3	4.1 g/cm3
Refractive index	1.58	Not specified
Light output relative to anthracene	64%	280%
Maximum emission wavelength	423 nm	450 nm
Scintillation decay time	2.4 ns	200 ns
Operating temperature	-40 to 55 C	-40 to 55 C
Coating thickness	Not applicable	4.5 mg/cm2
Detection role	Beta-particle detection	Alpha-particle detection

Alpha/Beta Detector Design Considerations

SP121 should be specified as part of the full detector assembly. For alpha detection, the ZnS(Ag) coated side must be exposed appropriately because alpha particles are stopped by very thin materials. For beta detection, the substrate thickness, beta energy, source distance, detector window and electronic threshold all affect the measured response.

SP121 is suitable for contamination monitoring and screening applications where alpha and beta sensitivity are required. If the instrument needs energy spectroscopy, isotope identification or high-efficiency gamma response, inorganic scintillators or specialized detector structures may be more appropriate.

SP121 vs. Related Plastic Scintillator Products

SP121 should be selected when a single coated screen is needed for alpha and beta surface contamination measurement. Other SP products target alpha-only screens, low-energy gamma response, beta detection, general plastic scintillation or optical coupling.

Product	Main Structure	Primary Use	Selection Notes
SP121 Plastic Scintillator	SP102 base with ZnS(Ag) coating, typically 4.5 mg/cm2	Alpha and beta radiation measurement	Choose for surface contamination detectors requiring dual alpha/beta response.
SP123 Plastic Scintillator	PMMA substrate with ZnS(Ag) coating, typically 4.5 mg/cm2	Alpha-ray detection	Choose for alpha-sensitive ZnS(Ag) screens and large-area alpha monitoring panels.
SP122 Plastic Scintillator	SP101 base with ZnS(Ag) coating, typically 8-10 mg/cm2	Low-energy gamma detection	Choose for low-energy gamma monitoring and portable radiation instruments.
SP102 Plastic Scintillator	Thin polystyrene-based plastic scintillator	Beta-ray and charged-particle detection	Choose for beta detection when no alpha-sensitive ZnS(Ag) layer is needed.
SP101 Plastic Scintillator	Blue-emitting plastic scintillator	Gamma-ray, X-ray and general ionizing radiation detection	Choose for uncoated plastic scintillator panels, blocks, bars and detector assemblies.
SPM100 Light Guide	Cast PMMA optical light guide	Light transfer and sensor coupling	Choose when optical coupling or geometry transition is needed, not as the active scintillator.

How to Specify SP121 Alpha Beta Scintillators

For an accurate SP121 quotation, define the total panel size, active area, SP102 substrate thickness, ZnS(Ag) coating surface density, coated side, coating uniformity, detector window, readout method, light-guide requirement, reflector, housing design and calibration plan.

If the detector is used for contamination monitoring, provide the target alpha and beta sources, expected energy range, response uniformity requirement, active area tolerance, mounting method and any instrument standard or inspection report requirement.

SP121 Plastic Scintillator RFQ Checklist

Providing the following information helps ATR Crystal review feasibility and quote more accurately.

RFQ Item	Information to Provide
Application	Surface contamination detector, alpha/beta survey instrument, laboratory counter or custom detector assembly.
Radiation target	Alpha source, beta source, energy range, threshold requirement and measurement geometry.
Panel geometry	Total size, active area, substrate thickness, shape, edge margin, mounting holes and drawing.
Material structure	SP102 substrate requirement, ZnS(Ag) coating thickness, coated side and coating area.
Optical readout	PMT, SiPM, photodiode, light guide, reflector, optical grease or coupling requirement.
Inspection requirement	Coating uniformity, visual inspection, alpha/beta response uniformity, reference source and report format if required.
Order information	Prototype quantity, batch quantity, packaging requirement and delivery schedule.

Frequently Asked Questions

What is SP121 Plastic Scintillator used for?

SP121 is used for alpha and beta surface contamination detection, portable survey instruments, laboratory alpha/beta counters and custom coated scintillator detector assemblies.

What is the structure of SP121?

SP121 uses an SP102 polystyrene-based plastic scintillator substrate coated with ZnS(Ag). The listed ZnS(Ag) coating thickness is 4.5 mg/cm2.

Which layer detects alpha particles?

The ZnS(Ag) coating is the alpha-sensitive scintillation layer. The coated side and detector window must be designed so alpha particles can reach the active surface.

Which layer detects beta particles?

The SP102 plastic scintillator substrate supports beta detection. Beta response depends on substrate thickness, beta energy, source geometry, optical coupling and electronics.

Is SP121 the same as SP123?

No. SP121 uses an SP102 base and is designed for alpha/beta measurement. SP123 uses a PMMA substrate with ZnS(Ag) coating and is mainly used for alpha detection.