How to Choose a Scintillator for Gamma Spectroscopy

How to Choose a Scintillator for Gamma Spectroscopy

Scintillator crystals are widely used in gamma spectroscopy, homeland security, X-ray imaging, radiation monitoring, nuclear research, and portable detectors.
Selecting the right scintillator depends on energy resolution, density, decay time, light yield, hygroscopicity, size needs, and cost.

This guide summarizes the most commonly used scintillators and how to choose the right one for your experimental or commercial application.

Key Parameters When Choosing a Scintillator

1. Energy Resolution (FWHM at 662 keV)

Better resolution → ability to distinguish close gamma peaks
Typical values:

Crystal Resolution
LaBr₃(Ce) 2.6–3% (best)
NaI(Tl) ~6–7%
CsI(Tl) ~6%
LYSO 8–10%
BGO 10–12%

2. Density & Effective Z

Determines detection efficiency.

Crystal Density (g/cm³) Notes
BGO 7.13 Very high efficiency
LYSO 7.1 High efficiency + fast decay
NaI(Tl) 3.67 Medium
CsI(Tl) 4.51 Medium-high

3. Light Yield (photons/MeV)

Higher → better resolution, lower noise.

Crystal Light Yield
CsI(Tl) 54,000
NaI(Tl) 38,000–42,000
LaBr₃ 63,000
LYSO 26,000–33,000
BGO 8,000

4. Decay Time

Important for fast counting or coincidence detection.

Crystal Decay Time
LYSO 40–45 ns (fastest common scintillator)
LaBr₃ 16–20 ns
NaI(Tl) 230 ns
CsI(Tl) 1,000 ns
BGO 300 ns

5. Hygroscopicity

Crystal Moisture Sensitivity
NaI(Tl) Highly hygroscopic
LaBr₃ Slightly hygroscopic
CsI(Tl) Slight hygroscopicity
LYSO Non-hygroscopic
BGO Non-hygroscopic

Summary of Each Crystal Type

NaI(Tl) — The Most Common Spectroscopy Crystal

  • Excellent light yield
  • Good resolution (~6–7%)
  • Low cost
  • Hygroscopic → requires hermetic package

Best for:
General gamma spectroscopy, teaching labs, environmental monitoring.

CsI(Tl) — High Light Yield, Rugged, Slightly Hygroscopic

  • Very high light output
  • Resolution comparable to NaI(Tl) (~6%)
  • Mechanically stronger
  • Lower cost for large volumes
  • Can be machined/shaped
  • Available in many geometries

Best for:
Portable radiation detectors, ruggedized devices, high-light applications.

LYSO — Non-Hygroscopic, Fast, High Density

  • High density → high gamma efficiency
  • Extremely fast decay (~40 ns)
  • Non-hygroscopic
  • Moderate resolution (8–10%)

Best for:
High count-rate applications, PET, coincidence detection, compact detectors.

BGO — Very High Density but Low Light Yield

  • One of the densest scintillators available
  • Low light output → poorer resolution
  • Excellent for high-energy gamma
  • Non-hygroscopic

Best for:
High-energy gamma detection, limited-space detectors, high-Z applications.

LaBr₃(Ce) — Premium, Best Resolution

  • Best resolution of any bulk scintillator (2.6–3%)
  • Fast decay
  • High light yield
  • Slightly hygroscopic
  • Expensive

Best for:
High-end spectroscopy, nuclear physics experiments.

Application-Based Selection Guide

  • General gamma spectroscopy → NaI(Tl)
  • Portable detectors → CsI(Tl) or LYSO
  • High-resolution spectroscopy → LaBr₃(Ce)
  • High-energy gamma → BGO
  • Fast timing → LYSO or LaBr₃
  • Low-cost, large-area detectors → CsI(Tl)

Frequently Asked Questions

Q1. What is the best scintillator for gamma spectroscopy?

LaBr₃(Ce) (best resolution) or NaI(Tl) (best cost-performance).

Q2. Is CsI(Tl) good for spectroscopy?

Yes — resolution ~6% at 662 keV, very high light yield.

Q3. Which scintillator is best for portable detectors?

CsI(Tl) or LYSO.

Q4. Which scintillator has the fastest decay time?

LYSO (40 ns) and LaBr₃ (~20 ns).

Q5. Which scintillator is non-hygroscopic?

LYSO and BGO.

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