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Scintillation Radiation Detector Assemblies
The proper scintillation detector packaging and integration of scintillation crystals is a science combining advanced design and engineering skills with proven assembly techniques and materials to produce stable, high-resolution radiation detectors. Offering a variety of standard detector designs to fulfill most radiation counting applications: a packaged scintillator, a scintillator integrated (permanent or demountable) with a light-sensing device, and a detector with low energy entrance window.
Light sensor options included PMT, position-sensitive PMT and SiPM selected for low-background, premium resolution, fixed high voltage use, or gain matching.
Each of those standard detector configurations can be designed with one or more custom options* or add integrated or plug-on voltage divider, preamplifier, high voltage power supply and multi-channel analyzer.
*Custom designs can incorporate special flanges, mounting fixtures, low background packaging options, harsh environments to operate outside a standard laboratory environment (extreme cold, vacuum, elevated temperatures, underwater, severe mechanical shock and vibration) or other modifications can be requested.
Scintillation Detectors with Integrated Light Sensor
In this configuration, an integrally mounted light sensing device, such as a photomultiplier tube (PMT) and silicone photomultiplier (SiPM), is optically coupled directly to the scintillator. The scintillator and light sensor are assembled in a light-tight, compact and hermetic package for optimal performance.
End-well and through-well geometries are available.
View our Standard Scintillation Product List for sales drawings.
Features/Benefits
- Direct light sensor-to-crystal mounting
- Compact package
- Light sensor is matched and tested with scintillator
- Consistent, superior energy resolution
Popular Configurations
- Solid detectors (2M2/2) are commonly used for gamma-ray spectroscopy, radon canister counting, thyroid uptake measurements, and health physics applications.
- The end well (2MW2/2) configuration is the most efficient and is used for radioimmunoassay, wipes and sample counting.
Detectors can be built with a wide range of well sizes. - Through-side well detectors (2MWS2/2) are ideal when space is limited and is the second most efficient configuration, and are ideal for radioimmunoassay and fuel rod monitoring.
Scintillation Detectors with Demountable Light Sensor
The demountable designs are made with hermetic seals to optical windows that allow the removal of the light sensor(s) without disturbing the scintillator hermetic package. This configuration is well-suited for applications requiring the use of a crystal larger than 4” diameter or multiple light sensors.
Features/Benefits
- Light sensor may be removed without disturbing the scintillation crystal's hermetic package
- Large scintillator volumes can be accommodated
- Detector performance can be guaranteed for energy and/or timing resolutions
Design Notes
- Large detectors may require multiple PMTs
- For a multiple PMT assembly, the PMTs are matched for gain and balanced. This makes it possible to sum the output of all PMTs and obtain one uniform signal with optimum energy resolution. Records for each detector in our database allow us to supply replacement PMTs.
- Scintillator areas not viewed by PMTs are covered with a reflector for optimum light collection.
Popular Configurations
- The solid detector with a single PMT is a general-purpose detector and is used in material assay, activation analysis and other higher energy counting applications.
- Side well and end well-configured detectors are highly efficient for measuring activity of small-sized sources and in higher energy emitting isotope measurements.
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Scintillation Detectors with Square or Rectangular Cross-Sections
Scintillation detectors with square or rectangular cross-sections are a cost-effective alternative to the standard right circular cylinder. A square scintillator provides a 27% increase in volume over a cylindrical scintillator of the same diameter and length. This increases detector efficiency while keeping package size and shielding requirements down. It also allows for stacking of detectors in arrays. Various lengths are available, depending on the scintillator choice, with 16” being a common size. Excellent uniformity can be achieved for long square or rectangular detectors. Up to 1m lengths have been designed and assembled. The stopping power is sufficient for high energy gammas. Common applications include aerial survey, whole body scanning, pulse gamma neutron activation analysis (PGNAA) and portal monitors.
Features/Benefits
- Increased crystal volume
- Reduced number of light sensors for large coverage area
- Easily stacked in arrays for increased efficiency
- Excellent energy resolution and uniformity
Popular Configurations
- The most common sizes are 2"x4"x16", 3"x5"x16" and 4"x4"x16" assemblies. PMT sizes include 2", 3" and 3.5". Aluminum or stainless steel housings are common.
- Applications include aerial survey, whole body counting, security portal monitoring and medium and high energy physics.
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Standard Packaged Scintillators
The scintillation crystal is hermetically packaged with a metal container, an optical window incorporated on one end, and reflector material between the scintillator and the container walls. A wide variety of shapes (including rectangular) and sizes can be produced. These detectors require user-supplied, externally-coupled light sensors.
View our Standard Scintillation Product List for sales drawings.
Features/Benefits
- Reliable hermetically package
- Stable reflector systems
- Flexible configurations
Design Notes
- Detectors made with non-hygroscopic scintillators can be assembled without the optical window, e.g., BGO, CdWO4.
- Detectors are hermetically sealed when hygroscopic scintillators, e.g., NaI(Tl) are used.
- You can temporarily mount a PMT by using optical coupling compound and black tape to make a light seal. Optical coupling materials are available, details on the assembly materials page.
Popular Configurations
- Solid detectors are commonly used for simple spectroscopy; general purpose for energies greater than 15 keV.
- End well detectors are the most efficient (typically greater than 80%) because the scintillator surrounds the sample; ideal for radioimmunoassay applications.
- Through-side well detectors are ideal when space is limited; they are the second most efficient configuration and are ideal for radioimmunoassay and fuel rod scanning applications.
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Detectors For Low Energy Gamma and X-ray Detection
Our X-ray detectors and probes are used in various low-energy and X-ray detection applications. These detectors come in three types of assemblies: Packaged X-ray crystals, Integral X-ray detectors and X-ray probes. All use a thin 1mm or 2mm NaI(Tl) crystal — usually 25mm (1"), 38mm (1.5") or 51mm (2") in diameter — and a radiation entrance window selected to provide the appropriate transmission for the energy of interest. The typical energy range for an assembly with a beryllium entrance window is 3 to 100 keV and 10 to 200 keV for an assembly with an aluminum entrance window.
View our Standard Scintillation Product List for sales drawings.
Features/Benefits
- Thin entrance window allows measurements down to 3 keV
- Thin crystal reduces sensitivity to background radiation
Popular Configurations
- X-ray packaged crystals are used in X-ray diffraction, X-ray fluorescence, Mossbauer studies and gauging
- 1mm thick NaI(Tl) crystal mounted in an aluminum container with a radiation entrance window on one end and a glass or quartz optical window on the other. The assembly is hermetically sealed.
- X-ray integral assemblies are used in health physics applications
- 1mm thick NaI(Tl) crystal mounted in an aluminum container with a radiation entrance window, and optically coupled directly to a photomultiplier tube with an external mu-metal magnetic light shield. The PMT terminates in a 12- or 14-pin phenolic base, depending on whether a 1.5" or 2" PMT is used. The scintillator container and light shield form a continuous, hermetically-sealed, light-tight housing for the detector.
- The fixed collimator makes the X-ray probe ideal when a constant area of exposure is needed.
- Consists of a packaged crystal detector model 1XR.040/B mounted in an aluminum container with a removable brass collimator, and optically coupled to a photomultiplier tube with mu-metal magnetic light shield. The PMT is connected to a built-in, low-noise voltage divider that terminates with cables for signal and high voltage. The scintillator container and light shield form a continuous, lighttight housing for the detector.
Gain Stabilization Methods
Gain stabilization techniques are used to prevent loss of resolution due to gain drifts in PMTs and system electronics when making measurements over long time periods. Depending upon your requirements, we can supply detectors incorporating any of the following types of stabilization techniques:
Techniques
- Electronic Based Gain Stabilization method, the detector firmware automatically adjusts the relevant parameters, such as integration time and pile-up rejection as a function of temperature. A built-in temperature-compensated LED provides a reference light pulse that is used to ensure gain stability over time and temperature. Once a detector has been calibrated and gain stabilization enabled, the autopilot routine within the detector firmware takes over and maintains the gain while adjusting the parameters in order to ensure optimum detector performance (stability of ±5% between -20°C and +50°C). The routine preserves the energy window of interest while ensuring a near-constant pulse height resolution.
- Simulating Scintillation Pulses with an LED (Light Emitting Diode). A special type of diode that emits light when an electric current flows through it can be used to simulate a scintillation pulse to test the electronic circuits in the measurement system. To use LEDs as a gain stabilizing method, external electronics are needed. These systems have internal feedback loops to control the stability of the light output.
- Radioactive Sources (241Am, 137Cs) are used as a reference light source incorporated into the detector assembly. These light sources produce a peak in the spectrum outside the region of interest. The system adjusts the gain to keep this peak’s position constant in the measured spectrum. A very small 241Am source (<1000 Bq) can be mounted inside a scintillation detector. The α-particles emitted by the 241Am cause scintillation events in the crystal that are detected by the PMT of the detector. For NaI(Tl), the α-peak appears at an equivalent γ-ray energy of 2.6 MeV. The Gamma Equivalent Energy (G.E.E.) can be adjusted upon request. Standard count rates are 50, 200 and 1000 cps. The position of the pulser peak is used as a reference to compensate for the previously mentioned variations in detector response.
Design Parameters |
Electronics Based | LED | Radioactive Sources |
|---|---|---|---|
| Lowest background contribution | x | x | |
| “On/Off” switch performance | x | x | |
| Minimal mechanical design interface | x | x | |
| Minimum drift with temperature | x | x | |
| Space-qualified | x | x | x |
| Radiation license | x | ||
| Turnkey solution | x | ||
| Cost | $ | $$ | $$$ |