TOPAZ-HR Compact High-Resolution Digital MCA

1Overview / Introduction

The TOPAZ-HR is a compact, stand-alone digital Multi-Channel Analyzer (MCA) designed to perform Pulse Height Analysis (PHA) of signals produced by high-resolution gamma-ray semiconductor detectors, including Hyper Pure Germanium detectors (HPGe). It is equally capable with scintillator detectors such as NaI(Tl), LaBr3, and CeBr3, making it a genuinely multi-purpose instrument.

High-resolution gamma-ray spectrometry is a core technique in advanced radio-analytical laboratories and in comprehensive nuclear analytical methods. The TOPAZ-HR brings together the digital signal processing depth of a laboratory-grade MCA in a form factor that fits a briefcase. A 14-bit flash ADC running at 50 Ms/s feeds a 100 MHz DSP and a 200 MHz CPU, giving the instrument the processing headroom to handle even demanding HPGe spectroscopy conditions cleanly.

Out of the box, the TOPAZ-HR ships with a basic software package for device control, data acquisition, and spectrum visualization. That package includes an automatic "discovery" function that finds all BrightSpec MCAs connected to the PC or reachable on the local network. For facilities that require a complete analytical workflow, the instrument integrates with bGamma, Berkeley Nucleonics' full-featured gamma-ray spectrometry software. Within bGamma, users perform data acquisition, spectrum analysis, energy calibration, and radioactivity quantification per radionuclide, all in a single environment.

Programming libraries for Windows and Linux are available, allowing the TOPAZ-HR to be embedded in larger radiation measurement systems or custom software stacks. A bare PCB variant is available for OEM integration.

2Key Features

3Description

Digital Signal Processing Architecture

At the heart of the TOPAZ-HR is a 14-bit high-quality fast flash ADC running at 50 Ms/s, paired with a 100 MHz DSP processor and a 200 MHz CPU. This architecture enables accurate, low-noise digitization of the shaped pulses from high-resolution detectors, where precise peak centroiding determines the ultimate energy resolution delivered to the user.

The trapezoidal pulse shaper is fully configurable. Rise time and flat-top width are independently adjustable over wide ranges, allowing the instrument to be optimized for the specific detector type and counting rate environment. At high count rates, the pile-up rejector (PUR) and digital base line restorer (BLR) work together to maintain spectral quality. Poles/zero cancellation is analog and adjustable, with fine-tuning of dead time correction also available.

Acquisition Modes

Four acquisition modes cover most laboratory and field scenarios. PHA is the standard mode for energy spectrometry, filling the spectral histogram channel by channel. MCS (Multi-Channel Scaling) sweeps through channels sequentially in time, useful for counting rate versus time measurements. LIST mode records individual events in sequence without time stamps. TLIST mode adds a time stamp to every event with better than 30 ns resolution, enabling coincidence measurements, half-life determinations, and time-correlated spectroscopy.

Preset acquisition stops are flexible. Measurements can be terminated by preset real time, live time, count total in a region of interest (ROI), external control signal, or any combination of these conditions. Preset times range from 0.005 seconds to approximately 0.65 years.

High-Voltage and Preamplifier Supply

The integrated high-voltage module supplies 0 to 6000 V at 350 µA, with automatic voltage ramping on power-up and an external inhibit control line. Dual polarity is available but is set at the factory at order time. The separate preamplifier supply provides ±24 V at 125 mA and ±12 V at 250 mA through a DB9 connector on the back panel. Both RC-feedback and pulse-reset preamplifier topologies are supported, with automatic detection of the reset pulse in the latter case.

Connectivity and Physical Design

Data transfer to the host PC uses USB 2.0 at up to 480 Mbit/s. The front panel carries a DC barrel power input and a USB mini-B port. The back panel provides an SHV connector for the high-voltage output, three BNC connectors for signal input and GPIO, and the DB9 preamplifier power connector.

Four front-panel LEDs give immediate status at a glance: red for detector high-voltage status, yellow for incoming count rate, green for power and communications, and blue for HV inhibit active. A second blue LED on the power switch confirms power-on. The unit is powered by an included external low-noise AC/DC adapter (9 to 24 V, 15 W maximum).

Software Ecosystem

The included basic software handles device control, spectrum acquisition, and visualization. The automatic discovery function locates all BrightSpec-family MCAs connected via USB or on the local network, simplifying multi-instrument lab setups. For complete analytical capability, the TOPAZ-HR integrates with bGamma, which adds spectrum analysis, nuclide library matching, energy and efficiency calibration, and quantitative activity reporting. Programming libraries for Windows and Linux allow the MCA to be embedded in custom systems; the device is also available as a bare PCB for OEM applications.

4Technical Specifications

Device

Data Acquisition

MCS Mode

Digital Signal Processing Settings

Power Supply

GPIO

Data Communication

Physical

Connectors

Status Indicators

Software and Libraries

5Applications

The TOPAZ-HR is suited wherever high-resolution or moderate-resolution gamma-ray spectrometry is required in a compact, laboratory-grade package. Primary use cases include:

• HPGe Spectrometry: The design target. Processes the semi-Gaussian pulses from hyper-pure germanium detectors with full digital shaping flexibility.
• Scintillator Spectroscopy: Compatible with NaI(Tl), CeBr3, LaBr3, and other scintillator detectors, covering a wide resolution range in a single instrument.
• Nuclear Analytical Laboratories: Radiochemical assay, environmental sample analysis, isotopic ratio measurements, and activation analysis workflows.
• Radioactivity Quantification: Combined with bGamma, supports per-nuclide activity quantification and full reporting, including calibration against reference standards.
• Coincidence and Time-Correlated Measurements: TLIST mode with sub-30 ns time resolution supports coincidence counting, angular correlation, and half-life measurements.
• Counting Rate Studies: MCS mode enables time-resolved count rate measurements for short-lived isotopes or pulsed-beam experiments.
• OEM and Custom Radiation Systems: PCB-only availability and SDK libraries allow tight integration into portal monitors, in-line assay systems, and automated laboratory instruments.
• University and Research Physics: An affordable, full-featured digital MCA for teaching laboratories and research groups requiring scripted or automated data collection.

6Ordering & Contact

The TOPAZ-HR is available as a complete boxed unit including the MCA, AC/DC power adapter, 3-meter USB cable, and basic acquisition software. Optional configurations are available at order time.