3″x3″ NaI(Tl) Scintillation Detector
3-Inch x 3-Inch NaI(Tl) Scintillation Detector for Gamma Spectroscopy
The NAI3/3P3 detector combines a 3-inch diameter x 3-inch long NaI(Tl) scintillation crystal with a matched 3-inch photomultiplier tube in an integrated, light-tight detector assembly. This established detector size provides a practical balance of gamma-ray detection efficiency, energy resolution, availability, and system cost for laboratory and OEM instruments.
A typical energy-resolution target is 7.5% FWHM or better at the 662 keV photopeak of Cs-137 under defined measurement conditions. Final performance depends on the NaI(Tl) crystal, PMT, optical coupling, high-voltage stability, signal processing, source geometry, shielding, and calibration method. The required housing, connector, voltage divider, magnetic shield, preamplifier, and high-voltage interface should be confirmed before production.
For crystal-only requirements, review the NaI(Tl) scintillation crystal page. For other assembled detector formats, visit the scintillation detector category.
Typical Applications
Gamma-ray spectroscopy and isotope identification
Laboratory counting and nuclear measurement systems
Environmental and field radiation monitoring
Educational and research detector setups
Industrial process and contamination monitoring
OEM multichannel-analyzer and survey instruments
Detector Configuration
The following configuration describes the standard NAI3/3P3 starting point. Connector layout, electronics, shielding, housing dimensions, and acceptance tests must be confirmed for the final order.
| Item | Typical Configuration / Requirement |
|---|---|
| Detector model | NAI3/3P3 |
| Scintillator material | Thallium-doped sodium iodide, NaI(Tl) |
| Crystal size | 3-inch diameter x 3-inch length |
| Photosensor | Matched 3-inch photomultiplier tube |
| Detector format | Hermetically encapsulated crystal, optical coupling, PMT, and light-tight housing |
| Energy resolution | Typical target: ≤7.5% FWHM at Cs-137, 662 keV, subject to agreed test conditions |
| Signal output | Raw PMT pulse or preamplified output, depending on the confirmed configuration |
| High voltage | External or integrated HV arrangement can be reviewed with the selected PMT base |
| Connector | BNC, SHV, LEMO, or drawing-defined connector by review |
| Optional components | Voltage-divider base, magnetic/light shield, preamplifier, HVPS, cable, and mounting interface |
NaI(Tl) Material Reference Data
These are commonly cited reference values for NaI(Tl). They are not an unconditional guarantee for the complete detector. Final acceptance limits must be stated together with detector size, PMT, electronics, source, geometry, temperature, and test method.
| Material Parameter | Typical Reference Value |
|---|---|
| Chemical formula | NaI(Tl) |
| Density | Approximately 3.67 g/cm3 |
| Emission peak | Approximately 415 nm |
| Primary decay time | Approximately 250 ns |
| Hygroscopicity | Highly hygroscopic; reliable hermetic encapsulation is required |
| Crystal structure | Cubic |
| Typical strength | High light output and mature gamma-spectroscopy performance |
| Design limitation | Moisture sensitivity and slower timing than fast cerium-doped scintillators |
What Determines Detector Performance?
- Crystal quality and dimensionsLight collection, full-energy efficiency, and resolution depend on crystal uniformity, optical quality, and detector geometry.
- Hermetic encapsulationNaI(Tl) is highly hygroscopic, so the housing and optical window must protect the crystal from moisture throughout handling and operation.
- PMT spectral and geometric matchThe photocathode area and spectral response should be matched to the crystal emission and optical exit area.
- Optical coupling and reflectorCoupling material, reflector, window, and interface quality affect light collection and pulse-height uniformity.
- High voltage and electronicsPMT gain, divider design, preamplifier, shaping time, MCA settings, and grounding can change measured resolution and stability.
- Test conditionsSource position, collimation, count rate, shielding, temperature, acquisition time, and fitting method must be controlled when performance is accepted.
3×3 NaI(Tl) Detector Compared with Related Options
| Detector Option | Typical Strength | Important Limitation | Common Fit |
|---|---|---|---|
| 3×3 NaI(Tl) detector | Mature spectroscopy performance, high light output, established detector size | Hygroscopic crystal; slower than LaBr3(Ce) | Gamma spectroscopy, isotope identification, laboratory counting |
| 2×2 NaI(Tl) detector | Smaller, lighter, and generally lower-cost assembly | Lower full-energy efficiency than a comparable 3×3 detector | Portable instruments and compact laboratory systems |
| LaBr3(Ce) detector | Better energy resolution and much faster decay | Higher cost, hygroscopicity, and intrinsic background | High-resolution and high-count-rate spectroscopy |
| BGO detector | High density and strong gamma stopping power | Lower light output and poorer spectroscopy resolution than NaI(Tl) | Compact high-energy gamma detection and shielding assemblies |
| Well-type NaI(Tl) | High counting efficiency for small samples placed inside the well | Application-specific geometry and sample-size constraints | Sample counting and low-activity laboratory measurement |
For a broader material comparison, read the NaI(Tl) gamma-spectroscopy selection guide.
Photomultiplier Tube Reference Specifications
The following PMT values are retained from the original product data. Confirm the exact PMT model and approved datasheet before placing an order.
| Photomultiplier Tube Specifications | ||
| Spectral Response Range | 300-650 nm | |
| Peak Wavelength | 420 nm | |
| Photocathode Minimum Effective Area | 70 mm | |
| Photocathode Material | Bialkali | |
| Window Material | Borosilicate glass | |
| Dynode Structure / Stages | Box-and-grid / 8 | |
| Cathode Luminous Sensitivity | Min. | 80 µA/lm |
| Typ. | 110 µA/lm | |
| Cathode Blue Sensitivity | Min. | 10 µA/lm |
| Typ. | 12 µA/lm | |
| Anode Luminous Sensitivity | Min. | 3 A/lm at 1000 V |
| Typ. | 30 A/lm at 1000 V | |
| Anode Dark Current | Typ. | 2 nA at 1000 V |
| Max. | 10 nA at 1000 V | |
| Anode Gain, Typical | 2.73 x 105 | |
| Anode-to-Cathode Voltage (DC) | Max. | 1500 V |
| Rise Time | Typ. | 8 ns |
| Operating Ambient Temperature | -30 to +50°C | |
| Suitable Socket | E678-14W | |
Inspection and Acceptance
Acceptance requirements should be written into the quotation or drawing before production. A practical inspection plan may include the following items.
- Mechanical inspectionOverall dimensions, connector layout, housing condition, mounting interface, and label information.
- Electrical inspectionPMT operating voltage, dark current or background behavior, polarity, connector continuity, and signal-output verification.
- Spectroscopy checkEnergy resolution at Cs-137 662 keV with the agreed source geometry, electronics, shaping time, count rate, and fitting method.
- Light-tightness checkVerification that ambient light does not produce abnormal output under the agreed operating setup.
- DocumentationInspection record, spectrum screenshot, dimensional report, interface description, or other agreed documents.
Information Required for a Quotation
| RFQ Item | Information to Provide |
|---|---|
| Application | Gamma spectroscopy, isotope identification, monitoring, education, research, or OEM instrument |
| Detector quantity | Prototype quantity and expected repeat quantity |
| Resolution target | Required FWHM at 662 keV and complete acceptance-test conditions |
| Signal interface | Raw PMT pulse or preamplified output; connector and polarity |
| High-voltage arrangement | External HV, integrated HV base, voltage range, connector, and control requirement |
| Mechanical requirements | Maximum envelope, mounting holes, cable direction, shielding, and drawing |
| Electronics compatibility | MCA, preamplifier, shaping amplifier, HVPS, or existing instrument model |
| Documentation | Inspection report, spectrum, interface description, country-of-origin documents, and packing requirement |
