CLLBC Dual-Mode Scintillation Detectors

1 Overview

CLLBC (Cs₂LiLaBr_4.8Cl_1.2:Ce) is a cerium-doped elpasolite crystal that delivers properties closely comparable to LaBr₃:Ce while adding a second, distinct capability: thermal neutron detection. The crystal contains lithium enriched to 95 % in ⁶Li, which generates a sharp thermal neutron peak at 3.1–3.2 MeV. That peak sits well clear of the gamma continuum, making CLLBC one of the very few materials that can perform high-resolution gamma spectroscopy and neutron counting at the same time, in a single detector element.

Energy resolution around 3.2 % FWHM at 662 keV is standard, roughly half the figure for NaI(Tl). At higher energies the advantage grows: CLLBC achieves 2.3 % at 1332 keV (Co-60) and 1.8 % at 2600 keV (Th-228). That resolution level supports isotope identification in real-world mixed-radiation environments without the complexity and cost of a separate neutron detector module.

Choose CLLBC when an application demands both radiation types in a compact package: radiation portal monitors, handheld RIID instruments, field-deployed nuclear identifiers, or physics setups where neutron/gamma pulse-shape discrimination (PSD) is required. For pure gamma spectroscopy without the neutron channel, CeBr₃ or LaBr₃:Ce may offer a simpler path. CLLBC is the material when both channels matter.

2 Specifications

3 Energy Resolution Performance

The table below compares CLLBC typical resolution figures against CeBr₃ and NaI(Tl) across six reference energies. Values are FWHM percentages. CLLBC leads at every energy point listed; the advantage is most pronounced in the mid-range (662 keV) and at higher energies where separation of closely spaced photopeaks is critical.

The resolution advantage at 662 keV (3.2 % vs. 7 % for NaI(Tl)) directly translates to cleaner separation of nearby isotope lines in field RIID instruments and portal monitors. At 1332 keV the gap widens further, supporting reliable identification of man-made radionuclides against natural background.

At low and intermediate gamma energies the photopeak remains sharp and clearly separated from the Compton continuum. The Co-57 spectrum above, measured on a 38x38 mm crystal, shows the 122 keV line resolved at approximately 6.4 % FWHM.

At high energy the resolution advantage is most pronounced. The Th-228 spectrum above reaches 1.8 % FWHM at the 2.6 MeV line, supporting reliable separation of closely spaced high-energy photopeaks that NaI(Tl) cannot resolve.

4 Dual-Mode Neutron Detection

The 95 % ⁶Li enrichment gives CLLBC a sharp thermal neutron peak between 3.1–3.2 MeV equivalent energy, well clear of the gamma continuum. The spectrum above, measured on a 38x38 mm crystal exposed to a Cf-252 neutron source and Cs-137, shows the thermal neutron peak isolated near channel 810. This separation is what lets a single CLLBC element count neutrons and resolve gamma photopeaks at the same time.

CLLBC additionally offers excellent neutron/gamma discrimination using pulse-shape discrimination (PSD), allowing the two event types to be distinguished by pulse timing in addition to the spatial separation of the neutron peak.

The background spectrum above characterizes the intrinsic and ambient response of CLLBC in a radiology setting, useful for establishing baseline counts before field deployment.

5 Typical Applications

CLLBC is selected wherever simultaneous neutron and gamma detection is required in a single compact crystal, or where high-resolution gamma spectroscopy must operate alongside a neutron channel without adding detector size or complexity.

• Radiation isotope identification devices (RIID): handheld and backpack instruments for field identification of nuclear and radiological threats. CLLBC resolves closely spaced gamma lines while flagging neutron presence via PSD, removing the need for a separate He-3 or ⁶Li neutron tube.
• Nuclear material detection and interdiction: border security portals and chokepoint monitors where accurate isotope ID must be maintained at high throughput.
• Homeland security and radiological defense: mobile survey instruments and fixed monitoring systems where both gamma identification and neutron detection capability are mandatory requirements.
• Physics research: experiments requiring neutron/gamma PSD, mixed-field characterization, or high-resolution spectroscopy with a dual-mode detector.
• Nuclear non-proliferation monitoring: treaty verification and safeguards instruments where material-specific spectral signatures must be resolved in field conditions.
• Environmental and emergency response: rapid field assessment of mixed radiation environments following incidents, where both radiation types must be characterized.

6 Available Configurations

Berkeley Nucleonics supplies CLLBC detectors in custom configurations matched to the application. Because CLLBC is hygroscopic, all crystals ship hermetically sealed. Standard options are summarized below; contact Berkeley Nucleonics to confirm availability and lead times for a specific geometry.

Crystal Sizes

CLLBC is available in cylindrical and rectangular crystal forms. Specific maximum dimensions are not published in the current datasheet; mark as verify. Common RIID and physics configurations range from small-volume units (for handheld detectors) through medium cylindrical formats for stationary instruments. Request a quote for your target size.

Readout Options

Housing and Sealing

CLLBC crystals require hermetic encapsulation due to hygroscopicity. Berkeley Nucleonics supplies assembled detectors with hermetically sealed aluminum or stainless steel housings, optical coupling compound, and a borosilicate or UV-glass window matched to the readout device. Teflon reflector and mu-metal shielding are available as options (verify specific configurations at order time).

Complementary Electronics

Pair a CLLBC detector with the Berkeley Nucleonics ScintIQ readout and analysis electronics, including the bMCA multi-channel analyzer and TOPAZ-HR high-resolution spectroscopy module, to complete the detection chain. See the separate electronics datasheets for specifications.