NaI(Tl) Scintillation Crystal
NaI(Tl) Scintillation Crystal for Gamma Spectroscopy
NaI(Tl) scintillation crystal, or thallium-doped sodium iodide crystal, is a widely used inorganic scintillator for gamma spectroscopy, radiation monitoring, nuclear medicine, well logging, and security detection. It offers high light yield, good energy resolution, and an emission peak around 415 nm that matches standard bialkali PMTs.
ATR Crystal supplies NaI(Tl) crystals in hermetically sealed assemblies, including standard cylinders, rectangular blocks, end-well formats, X-ray type designs, and PMT-coupled detector modules. Because NaI(Tl) is highly hygroscopic, encapsulation, reflector selection, optical window design, and sealing quality are important for long-term detector performance.
For related products, review our scintillation crystals, encapsulated NaI(Tl) scintillator, 2×2 NaI(Tl) scintillation detector, 3×3 NaI(Tl) detector, and CsI(Tl) scintillation crystal.
Applications of NaI(Tl) Crystal
Gamma-ray spectroscopy and isotope identification
Environmental radiation monitoring instruments
Well logging and geological exploration tools
Gamma cameras and nuclear medicine systems
Security inspection and portal monitor detectors
Health physics survey meters and counting systems
Advantages of NaI(Tl) Scintillation Crystal
- High light yieldNaI(Tl) typically provides about 38,000 photons/MeV, giving useful signal strength for gamma counting and spectroscopy.
- Good energy resolutionTypical energy resolution is about 6-7% at 662 keV, depending on crystal size, encapsulation, PMT, electronics, and test conditions.
- PMT-compatible emissionThe 415 nm emission peak is well matched to common bialkali photomultiplier tubes.
- Mature detector materialNaI(Tl) is widely used in established gamma spectroscopy, monitoring, and detector systems.
- Custom encapsulationAluminum or stainless-steel housing, optical glass or quartz windows, and reflector options can be reviewed according to the application.
- Multiple geometriesStandard round crystals, rectangular blocks, end-well designs, X-ray type NaI(Tl), and integrated detector assemblies can be discussed.
Specifications of NaI(Tl) Crystal
The following table summarizes typical NaI(Tl) scintillation crystal properties for detector design review.
| Parameter | Typical Value |
|---|---|
| Chemical formula | NaI(Tl) |
| Crystal structure | Cubic |
| Density | 3.67 g/cm3 |
| Melting point | 651 C |
| Mohs hardness | 2.1 |
| Cleavage plane | (100) |
| Hygroscopicity | Highly hygroscopic; hermetic sealing required |
| Light yield | Approx. 38,000 photons/MeV |
| Decay time | Approx. 250 ns |
| Emission peak | Approx. 415 nm |
| Refractive index | Approx. 1.85 at emission peak |
| Energy resolution | Approx. 6-7% at 662 keV |
Available NaI(Tl) crystal geometries and encapsulation options.
| Format | Details |
|---|---|
| Standard cylinders | 1 inch x 1 inch, 2 inch x 2 inch, 3 inch x 3 inch, and custom diameters |
| Rectangular blocks | Customized dimensions for portal monitors, arrays, and area detector layouts |
| End-well detectors | Machined well designs for high-efficiency sample counting |
| X-ray type NaI(Tl) | Thin crystal and window options for low-energy X-ray detection |
| Encapsulation material | Aluminum or stainless-steel housing |
| Optical windows | Optical glass, quartz, or customized transparent windows |
| Reflector options | PTFE tape, alumina powder, or project-specific reflector design |
| Detector assembly | Crystal, housing, optical window, PMT, divider, and connector can be integrated on request |
NaI(Tl) vs. CsI(Tl) vs. BGO
NaI(Tl) is often selected for gamma spectroscopy because it balances high light yield, good energy resolution, PMT compatibility, and mature encapsulated detector design. CsI(Tl) and BGO may be preferred when photodiode readout, higher density, or non-hygroscopic handling is more important.
| Property | NaI(Tl) | CsI(Tl) | BGO |
|---|---|---|---|
| Light yield | Approx. 38,000 photons/MeV | Approx. 54,000 photons/MeV | Approx. 8,500 photons/MeV |
| Energy resolution at 662 keV | Approx. 6-7% | Approx. 7% | Approx. 12% |
| Decay time | Approx. 250 ns | Approx. 1000 ns | Approx. 300 ns |
| Density | 3.67 g/cm3 | 4.51 g/cm3 | 7.13 g/cm3 |
| Emission peak | 415 nm; PMT matched | 550 nm; photodiode matched | 480 nm |
| Hygroscopicity | Highly hygroscopic; sealing required | Slightly hygroscopic | Non-hygroscopic |
| Typical selection reason | Gamma spectroscopy and cost-effective large-volume detectors | Photodiode readout and rugged detector designs | High density and compact stopping power |
NaI(Tl) Product Formats and Related Detector Options
NaI(Tl) products are usually selected by geometry, entrance window, sample position, optical readout, and whether the crystal should be supplied as a bare encapsulated crystal or as an integrated scintillation detector assembly.
| Format | Best Fit | Key Design Point |
|---|---|---|
| General encapsulated NaI(Tl) | Standard gamma spectroscopy and counting | Hermetic housing protects hygroscopic NaI(Tl) |
| Square or rectangular NaI(Tl) | Tiled detector layouts and area coverage | Flat geometry improves packing and module layout |
| X-ray type NaI(Tl) | Low-energy X-ray detection | Thin crystal and window design improve low-energy response |
| End-well NaI(Tl) | Sample counting | Well geometry surrounds the sample for higher counting efficiency |
| 2×2 / 3×3 NaI(Tl) detector | Integrated gamma detector modules | Crystal, PMT, housing, and connector are supplied as an assembly |
Customization and Quality Control
- Drawing reviewDimensions, tolerance, window material, housing, optical coupling, and connector requirements can be reviewed before quotation.
- Hermetic sealingNaI(Tl) must be protected from moisture; sealing structure and window design should match the detector environment.
- Optical matchingEmission wavelength, window material, reflector, PMT or photodetector, and optical grease requirements can be discussed.
- Visual inspectionSurface quality, housing appearance, window condition, and assembly cleanliness can be inspected according to agreed criteria.
- Performance-related testingLight output, energy resolution, or detector response can be discussed when test conditions and electronics are defined.
- Prototype and batch supportSample evaluation and repeat supply can be supported depending on geometry, material availability, and processing complexity.
Pure NaI Crystal and NaI(Tl) Encapsulation Note
For gamma spectroscopy, the standard scintillation material is NaI(Tl), or thallium-activated sodium iodide. If your RFQ uses the term pure NaI crystal scintillator, please confirm whether you mean a high-purity NaI(Tl) scintillation crystal, a bare NaI(Tl) crystal for your own encapsulation, or a sealed NaI(Tl) scintillator assembly.
NaI(Tl) is highly hygroscopic, so most detector projects require hermetic encapsulation with an optical window and reflector structure. For a complete selection explanation, see our NaI(Tl) scintillation crystal selection guide, or review the encapsulated NaI(Tl) scintillator page if you need a sealed crystal package.
