How to Choose an Isotope Identifier

Start with the mission, not the spec sheet

A radioisotope identification device, or RIID, does one essential job. It tells a user not just that radiation is present, but which isotope is producing it. That single answer drives everything that follows: whether a flagged container holds harmless ceramic tile glaze, a medical patient who recently had a thallium scan, or special nuclear material that demands an immediate response. Choosing the right instrument starts with the people who will carry it and the decisions they need to make in the field.

Before comparing detectors and resolution figures, write down the operational picture. Who is the operator, a trained health physicist or a first responder in a HAZMAT suit? How far does the source need to be detected, and is the search static or moving? Does the answer have to survive expert review, or is a fast field call enough to act on? The sections below walk each decision in turn, then close with a checklist you can take into a procurement conversation.

Form factor: match the platform to the search

Form factor is usually the first hard constraint, because it follows directly from how the instrument is deployed. Berkeley Nucleonics builds the line around four broad platforms, and most procurement decisions land on one of them quickly.

Handheld RIID. The classic choice for inspection, adjudication, and one-hand field use. The SAM 940+, SAM 945, and SAM 950 are purpose-built handhelds. The SAM 940+ is the re-engineered next-generation unit with an internal detector and onboard camera. The SAM 945 leverages smartphone technology and the PeakAbout app for an all-in-one design. The SAM 950 is the ruggedized, water- and shock-resistant model built to meet ANSI N42.34. Pick a handheld when an operator walks up to a target, makes a call, and moves on.

Backpack. When the operator needs both hands free and wants to search discreetly while walking, a backpack system fits. The SAMpack 120 (RD-120) is a human-portable backpack for clandestine gamma and neutron monitoring, with an optional Rad-Compass directional feature and reachback built in. It reconfigures to stanchion or doorway use, so the same hardware covers a moving sweep and a fixed choke point.

Vehicle and mobile. For wide-area coverage at speed, a vehicle system trades portability for sensitivity. The SAMmobile 150 (RD-150) is a plug-and-play vehicle-mounted detection system that scales to multiple large NaI modules, with GPS color-contour mapping for freeway monitoring, choke points, and covert surveillance. Marine, aerial, and crane variants extend the same architecture beyond the road.

Personal radiation detector. A PRD is a small, always-on alarming device worn on the belt, sized for nontechnical personnel rather than spectroscopic analysis. The Model 951 nukeALERT and the PM1703GNA-II MBT fill this role. A PRD tells a wearer that radiation is present so a RIID can then identify it. Many programs pair the two: PRDs for broad coverage, a handheld RIID for the follow-up.

Detector material: resolution versus cost and ruggedness

The scintillator crystal sets how cleanly the instrument can separate one isotope from another. Energy resolution, expressed as full width at half maximum (FWHM) at the 662 keV cesium-137 line, is the headline number. Lower is better. A coarse detector blurs neighboring peaks together; a sharp one resolves them, which matters most when a real threat hides behind a naturally occurring background.

NaI(Tl) sodium iodide is the field workhorse, with roughly 7 percent FWHM, high light output, and a favorable cost. It handles the great majority of identification tasks. LaBr3 lanthanum bromide and CeBr3 cerium bromide deliver high resolution, near 3 to 4 percent, for cleaner separation of closely spaced lines and better confidence on special nuclear material. They carry a higher cost, and LaBr3 has a small internal background that CeBr3 largely avoids. The SAM 950 offers NaI, LaBr3, and CeBr3 options; the SAM 940+ offers NaI alongside CLYC and CLLBC dual-mode crystals. For the full tradeoff, see the companion note, NaI vs LaBr3 vs CeBr3 Detectors.

Crystal size matters too. A larger volume, such as a 3 by 3 inch NaI, gathers more counts and improves sensitivity at distance, at the expense of weight. The SAM 950 spans 1.5 by 1.5, 2 by 2, and 3 by 3 inch options so the same platform can be tuned toward portability or reach.

Neutron capability: do you need to find shielded SNM?

Gamma identification answers most field questions, but a determined adversary can shield a gamma source heavily. Neutrons pass through that shielding far more readily, so a neutron channel is the practical way to interdict shielded special nuclear material such as plutonium. If your mission includes counter-smuggling, border security, or SNM safeguards, neutron detection moves from optional to essential.

Across the line, the SAM 940+ integrates a solid-state neutron detector, the SAM 945 and SAM 950 offer optional neutron detection, and the SAMpack 120 and SAMmobile 150 support gamma and neutron together. The neutron decision interacts with the detector choice: CLYC and CLLBC crystals on the SAM 940+ detect neutrons and gammas in one crystal. The companion note Neutron Detection Explained covers the methods and tradeoffs in depth.

Library breadth and standards

An identifier is only as good as the library it matches against. A broad, well-curated library covers special nuclear material (SNM), industrial sources (IND), medical isotopes (MED), and naturally occurring radioactive material (NORM), and lets an analyst expand or edit entries. The SAM 945 ships with 115 isotopes and expands to 393 through the PeakAbout app. Larger libraries reduce unknown results, but the categorization and confidence reporting matter as much as raw count.

ANSI N42.34 is the U.S. performance standard for handheld radionuclide identifiers, and many programs require compliance. The SAM 950 is built specifically to meet it, and the SAM 940+ meets all ANSI N42.34 requirements. Confirm the exact standard, type, and any IEC or ITRAP testing that your program mandates against the current datasheet for the configuration you intend to buy (verify).

Reachback: getting an expert on the spectrum

Field operators are rarely spectroscopy experts, and they should not have to be. Reachback connects a captured spectrum to a remote analyst who can confirm or overturn a field call within minutes. The standardized ANSI N42.42 data format makes that transfer interoperable. Several models support RadResponder, the FEMA network used for reporting, and the SAM 945 uses the PeakAbout app for data management and reporting. If your operation answers to a command center or a national lab, prioritize one-click reachback and confirm the destination network is supported (verify).

Decision checklist

Run these questions before you request a quote. Each one narrows the field, and together they point to a specific configuration.

Talk to a BNC specialist

The fastest path to the right configuration is a short conversation about your mission. A Berkeley Nucleonics specialist can map your operational picture to a specific platform, detector, and option set, and flag any standard or reachback requirement before you commit. Reach the team at info@berkeleynucleonics.com or 800-234-7858.

To compare every model in the line, browse the Isotope ID & Radiation Detection documentation index, then dig into the two companion technical notes on detector materials and neutron detection.