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NaI(Tl) Scintillators for Well-logging Applications

Fundamental Properties of Na(Tl) Crystals

General Introduction of NaI(Tl) Scintillator

Transmission rate, ease of access to large-size crystals, and a large light output proportionate to input radiations are crucial characteristics of scintillation materials to support a suitable detector. Excellent detection capabilities are rare in materials.

Thallium Doped NaI, or NaI(Tl) ) Crystal is an excellent kind of scintillator. Thallium Doped Sodium Scintillator Iodide has the highest photon yield, which is regarded as the standard of photon-electron yield. Its emission wavelength of 415nm is well-matched to the PMT tube. Furthermore, NaI(Tl) also exhibits high energy resolution which is a critical factor affecting energy spectrum analysis. NaI(Tl) scintillators have been extensively utilized in various fields including industrial, medical, nuclear, and high-energy physics, assigned to X-Ray, Gamma-ray, and neutron detection. NaI(Tl) are prone to deliquescence, so it is routinely sealed in Al housing encapsulation.

Geological prospecting and oil field well-logging use gamma radiations as a detecting method. In the operation, detectors usually need to be put 400 meters underground. Due to the harsh environment of high temperatures (150℃-200℃), high pressure, and vigorous vibration, manufacturing capable detectors becomes a big challenge. Hangzhou Shalom EO selects the top-rate NaI(Tl) scintillators combined with an anti-vibration design realized via a robust shock-proof structure. Our product utilizes titanium compound metal as the external housing material, and sapphire as the optical window material, both of which are high-strength materials. The detectors operate well under harsh environments and are well suited to well-logging applications.

Working Principle of NaI(Tl) Detection

Each scintillator-based detector works on the same fundamental tenet: when radiation hits the scintillator, it causes it to emit photons of visible light (the scintillation component). The light enters the second section of the detector, known as a photo-multiplier tube （PMT）, after passing through the crystal and striking a small piece of metal foil called a photocathode.

An electron will be emitted when the photon reaches the photocathode. A series of metal cups with voltage attached to them (often several hundred to thousand volts) is located right behind the photocathode. The applied voltage accelerates the electron, and it impacts the cup with enough force to release several more electrons. Each of them is then propelled towards the next metal cup, where each of the "new" electrons releases a swarm of fresh ones. When the process is finished, the output signal is about of a million times the magnitude of the initial signal.

In the case of using a NaI(Tl) scintillator for gamma-ray detection, each time a gamma particle hits the crystal it starts this whole process that culminates in a pulse of electrons arriving at the far end of the detector.

Specifications of Well-logging NaI(Tl) Crystals

Operating Temperature: 25°C -175°C
Vibration： Acceleration 20g
Frequency: 20-1000Hz
Shock：400g@1ms

Example of the NaI(Tl) Scintillators From Shalom EO

This is one high-temperature anti-vibration detector. It consists a diameter of 39×258mm NaI(Tl) crystal, it is an anti-vibration design and the steel alloy used as housing materials can suit well-logging applications.

Hangzhou Shalom EO is a matured manufacturer and supplier of Thallium Doped Sodium Iodide/NaI(Tl) Scintillation Crystals, with a substantial domestic business scale. We also export NaI(Tl) products to the international market at an annual quantity of 200-300 pieces (In consideration of commercial confidentiality, please understand that we do not disclose the name list of these clients).

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