TB-5 Digital Tube Base for Scintillator and PMT

Nuclear Safeguard or Environmental Monitor

An example program is provided to aid in long term monitoring where weak sources are present. This program automatically saves a spectrum at user defined intervals, it provides gain stabilization using the 40K background peak, and it provides a simple ROI analysis capability to verify if suspect counts are present above preset thresholds. This software can run on a laptop, connected to the system by a USB cable. It can also run over an Ethernet link and the Internet, and be monitored on the other side of the world. The plot on the right shows a background spectrum and measurements from natural UO3 and a lantern mantle containing natural thorium.

Simultaneous Neutron Detection with Gamma-Ray Spectrum

The pulse shape discrimination capability of the Digital Tube Base enables one to detect thermal neutrons and measure a gamma-ray spectrum, simultaneously, with a single module. The key is the use of a “Phoswich” detector, a sandwich of two scintillators (with different time constants) mated to a single photomultiplier tube. At Amptek, we used a unit containing a LiI(Eu) crystal coupled to a NaI(Tl) crystal. The lithium is enriched in 6Li, providing efficienct detection of thermal neutrons via the 6Li(n,a) reaction. The two scintillators produce different pulse shapes so the pulse shape discrimination logic distinguished between them, counting the neutron events while measuring the gamma-ray spectrum.

Fast Neutron Detection

A fast neutron detector was fabricated, using an EJ-410 phosphor (zinc sulfide phosphor embedded in a plastic matrix) coupled to a 5” PMT. Fast neutrons undergo proton recoil interactions in the strongly hydrogenous polymer, producing a large optical signal. Gamma-ray interactions are eliminated by setting an appropriate threshold. This is a counting system, rather than a spectroscopy system, but uses pulse height analysis to discriminate between the species. The compact digital tube base with its PoE interface and software environment make implementation of a complete system straightforward.

TB-5 Specifications

Specifications subject to change without notice.

View our TB-5 Digital Tube Base specifications in PDF

Networking and interconnection of radiation detectors frequent poses problems for system integrators. Amptek’s TB-5 digital tube base makes it easy to interface with custom scintillators and also makes it easy to connect large and complicated systems, spread over a large geographic area and involving many different types of radiation detectors.

The TB-5 can easily interface with many scintillators: conventional gamma-ray spectrometers such as NaI(Tl), CsI(Na), BGO, lanthanum halides, and others are straightforward to use. A user can obtain the scintillator and PMT in whatever geometry is best for the specific application. With the TB-5, a single interface to the computer (USB or Ethernet) provides control, data acquisition,and all power supplies. But the TB-5 can be used with other materials. Thermal neutron and fast neutron detectors utilizing scintillators or phosphors and PMTs can be connected to the TB-5. Although these are counting systems and do not necessarily need the high performance signal processing electronics required for spectroscopy, the standard power supplies, communications interfaces, and application software of the TB-5 make operation straightforward. Most systems requiring a 14 pin PMT base can use the TB-5.

The TB-5 uses the same communications protocols and interface software as Amptek’s other digital pulse processors. This includes the PX5-HPGe (for use with high purity germanium detectors in high resolution gamma-ray spectroscopy), the GammaRad-5 (for ruggedized scintillation applications), the PX5 (a general purpose processor which can be used with CdTe or coplanar grid semiconductors), and the DP5 (a board designed for embedded applications). A single computer can easily interface to a network of dissimilar radiation detectors. The drawing below illustrates just a few concepts for interconnecting radiation detectors using Amptek’s digital processing technology.

Using Ethernet, a very large area detector network can easily be established. A single computer can interface to dozens of radiation detectors, spread throughout a building, over many buildings, or across the globe. In a large facility, one can network gamma-ray spectrometers, neutron counters, and even high purity germanium detectors to a central location. Using PoE, a single connection is needed, allowing fast and easy reconfiguration of detector networks. One can locate monitors in many different cities even and, using the globally available Internet, read them from one office.

The USB interface is ideal for smaller networks, with the 3 meter (max) cable. This works very well in research or operational laboratories. A single laptop can interface with multiple radiation detectors, for example high purity germanium detectors in a counting lab combined with gamma-ray and neutron scintillators used for radiation safety. The auxiliary connectors on all of the processors permit easy integration with external electronics, e.g. using gate signals to do coincidence measurements, to do beam—on versus beam-off measurements, and so on.

The RS232 interface is well suited to embedded systems, avoiding the overhead of USB and Ethernet. In a handheld radioisotope identifier, the RS232 interface to the TB-5 is straightforward to implement. One can even use multiple sensors, e.g. combining a DP5 processor to read out a semiconductor detector with the TB-5 mated to a scintillator. In addition, one can use commercially available RS232 adapter modules for other communication protocols: RS232 to Bluetooth, RS232 to WiFi, and others are available.

In short, the TB-5 is a powerful tool, providing a standard and flexible tool for connecting scintillation based radiation detector systems.