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The GAMMA-RAD5 is a powerful, portable instrument combining a complete NaI Scintillation Probe with a Digital Pulse Processor that provides high quality detection and spectroscopic information. To simplify its use, this detector system communicates and receives its power through the USB port. All that is needed is a laptop computer for control, display, and data storage. |
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Includes
Features
Detector
Standard Performance
Applications
Additional information |
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The GAMMA-RAD5 is a complete, integrated gamma-ray spectrometer. It includes a scintillator and PMT, a digital pulse processor based on Amptek’s DP5 called the DP5G, all the hardware and software necessary to control and communicate to a PC, and all power supplies. It is a single, integrated, portable module.
Several key innovations make this system ideal for field use. First, the scintillator and PMT are ruggedized to protect against mechanical shock and vibration. Second, the Ethernet interface permits operation over long distances: 100 m via Ethernet or, with Internet software, globally while the USB interface permits a single connection (power and data) to virtually any computer. Third, it has a flexible digital architecture so it can be easily tailored for specific applications. The GAMMA-RAD5 is ideally suited for a wide range of gamma-ray spectroscopy measurements, from lab applications to most harsh field homeland security applications.
Figure 2. GAMMA-RAD5 Architecture.
| Detector Properties | |||||||||||||||||||||||||||||||||||||
| Detector | The detector is a ruggedized scintillator and PMT. The 76 x 76 mm NaI(Tl) is considered standard, but many different configurations are possible. Contact Amptek for details. The detector performance (resolution, stopping power, photofraction, etc) are determined by the scintillation crystal. | ||||||||||||||||||||||||||||||||||||
Efficiency 76 and 152 mm NaI(Tl) |  Figure 3a. Efficiency of 76 x 76 mm NaI(Tl).
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| Pulse Processing Performance | |||||||||||||||||||||||||||||||||||||
| Gain Settings | Two software selectable coarse gain settings are available: 3 MeV full scale and 750 keV full scale. Fine gain is adjustable between 0.75 and 1.25. | ||||||||||||||||||||||||||||||||||||
| Pulse shape | Trapezoidal, typically set to 2.4 µs peaking time (equivalent to a 1 µs shaping time). Software commandable from 0.8 to 102.4 µs peaking time (0.3 to 40 µs equivalent shaping time). | ||||||||||||||||||||||||||||||||||||
| Gain stabilization | The gain from the NaI(Tl) and PMT is well known to vary with temperature. A gain stabilization algorithm runs in software to compensate. | ||||||||||||||||||||||||||||||||||||
| Maximum Count Rate, Dead Time, and Throughput | With the default configuration, the system operates to an input count rate of 150,000 sec-1 with a throughput >50% and good baseline stability and pile-up rejection. Configured for the shortest peaking time, 0.8 µs, it will sustain an input count rate of >300,00 sec-1 with throughput >50%. Unlike an analog system, there is no separate dead time for digitization and events can be processed when separated by less than a full pulse width, specifically by 1.25 times the peaking time. Pulse processing electronics have a cycle time of 1 µs so a 1 MHz periodic signal can be acquired. The fast channel (used for pile-up rejection and measuring the input count rate) has a 600 ns resolving time. | ||||||||||||||||||||||||||||||||||||
| Custom Configuration | The DP5 is set at the factory for either 20 MHz or 80 MHz clock. For NaI(Tl), the standard 20 MHz is standard, yielding the specifications listed above. The 80 MHz setting allows for peaking times down to 0.1 µs in the slow channel and 0.05 µs in the fast channel but draws about 50% more power. The 80 MHz setting is recommended for custom scintillator materials with faster decay times, fast pulse shape discrimination, or other unique requirements. | ||||||||||||||||||||||||||||||||||||
| MCA Performance | |||||||||||||||||||||||||||||||||||||
| Number of channels | Software commandable to 8k, 4k, 2k, 1k, 0.5k, or 0.25k channels. | ||||||||||||||||||||||||||||||||||||
| Minimum acquisition time | <10 ms | ||||||||||||||||||||||||||||||||||||
| Presets | Time, total counts, counts in an ROI, counts in a single channel | ||||||||||||||||||||||||||||||||||||
| External Connections | |||||||||||||||||||||||||||||||||||||
| USB | A standard USB interface, for USB 1.1 (2.0 compatible) at full-speed (12 mbps), is available. This provides both data and power for the entire GAMMA-RAD5. No external power is needed. | ||||||||||||||||||||||||||||||||||||
| Ethernet | 10Base-T or UDP, DHCP or fixed IP. External power must be used with this interface (AC adapter included). | ||||||||||||||||||||||||||||||||||||
| Aux 1 | This is a primary auxiliary input/output connector. It can be configured as (1) the analog output, (2) the AUX_OUT_1 digital output, or (3) the AUX_IN_1 digital input. AUX-1 can be used for diagnostic purposes by displaying analog outputs, e.g. shaped pulses or the ADC input. It can be used as a digital input, e.g. to count pulses from a 3He neutron monitor. It can be also be to display digital outputs, e.g. as an output count indicator. A software controlled switch selects between the DAC output and a bidrectional digital transceiver (SN74LVC1T45) with 50 Ohm series impedance and a 100 k pull-up resistor. It is a LEMO connector, P/N Lemo EPK 00.250.NTN. | ||||||||||||||||||||||||||||||||||||
| Aux 2 | This is a digital input/output connector. It can be configured as either (1) the AUX_OUT_2 digital output or (2) the AUX_IN_2 digital input. It is connected to a bidirectional transceiver (SN74LVC1T45) with a 50 Ohm series resistance and 100 k pull-up. It is a LEMO connector, P/N Lemo EPK 00.250.NTN. | ||||||||||||||||||||||||||||||||||||
| Aux 3 | This is a 15 socket D connector which includes (a) the lines for a serial RS232 interface, (b) the AUX_OUT_1 and AUX_OUT_2 digital input/output lines, and (c) the 8 SCA outputs. The RS232 lines connect to a MAX3227. The AUX_OUT lines connect to SN74LVC1T45. The SCA lines connect to an SN74LVC245. Amptek sells an optional breakout cable which mates with AUX-3.
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| Power Connector | A +5V AC adapter is provided. Only needed when using Ethernet or RS232. When using USB, the USB bus provides the power. If the Gamma-Rad5 is to be connected to an external power supply the connector information is below.
Molex 39-30-1020, Digi-Key WM1351-ND. | ||||||||||||||||||||||||||||||||||||
 Figure 4. Connectors. | |||||||||||||||||||||||||||||||||||||
| Power | |||||||||||||||||||||||||||||||||||||
| +5 V | Average current 150 mA USB, 350 mA Ethernet. When using the USB port, the entire Gamma-Rad5 can be powered from USB. Ethernet requires the use of the external DC supply. When the USB cable is plugged in and no Ethernet connetion is detected, the Gamma-Rad5 will automatically disable the Ethernet port to save power. | ||||||||||||||||||||||||||||||||||||
| Range | 3 to 6.4 V | ||||||||||||||||||||||||||||||||||||
| High Voltage | A stabilized, high efficiency Cockroft-Walton power supply provides PMT bias. The HV is software controlled. | ||||||||||||||||||||||||||||||||||||
| Physical | |||||||||||||||||||||||||||||||||||||
| Size | 31.5 cm x 9.2 cm (dia) | ||||||||||||||||||||||||||||||||||||
| Mass | 3.35 kg (76 x 76 mm NaI(Tl) with handles) 5 kg (76 x 152 mm NaI(Tl) with handles) | ||||||||||||||||||||||||||||||||||||
| Operating Temperature | -25 °C to + 65 °C. Maximum temperature gradient is 10 °C per hour. | ||||||||||||||||||||||||||||||||||||
| Interface Software | |||||||||||||||||||||||||||||||||||||
DPPMCA is a standard data acquisition and control package for use with all of Amptek’s digital processors and MCAs, including the GAMMA-RAD5. This package provides the capability to configure the GAMMA-RAD5 and acquire and save data. Amptek also provides a software developer kit (SDK) so that users can write their own interface software. Example routines, written in Visual Basic and Visual C++, are provided as examples. These can be tailored for specific uses. This includes an example code which implements the gain stabilization algorithm, using the 40K peak in the background spectrum. | |||||||||||||||||||||||||||||||||||||
Figure 5. GAMMA-RAD5 76 x 76 NaI(Tl) with handles.
Figure 6 shows an application that takes full advantage of the ruggedization of the GAMMA-RAD5. The GAMMA-RAD5 modules are mounted on the VeriSpreaderTM bar of the crane that lifts shipping containers. Radiation detection is carried out during routine handling so there is no delay in processing. The spectroscopy performance keeps the false positive rate at a very low level, which is a vital concern.
* VeriSpreaderTM is a trademark of VeriTainer Corporation U.S. Patent 6,768,421.
Presentation on this shipping container system.
Paper on this shipping container system.
Figure 6. Photo of VeriSpreader shipping container monitor.
An example program is provided with the GAMMA-RAD5 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 GAMMA-RAD5 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 below shows a background spectrum and measurements from natural UO3 and a lantern mantle containing natural thorium.
Figure 7.
The same software used for the environmental monitoring application can be used in a pedestrian or vehicle portal monitor using much shorter data acquisition intervals. The plot below shows the count rate, both total and in the 662 keV peak, when a pedestrian walked by the 76 X 76 mm detector at a distance of 10 feet with a 100 µCi 137Cs. A standard Geiger counter was unable to detect the source, since it registered a natural background of 0.02 mR/hr before and during the pedestrian incident, but the GAMMA-RAD5 clearly detected it and identified the energy.
Figure 8.
Figure 9. Optional 4" x 4" x 16" NaI(Tl). The resolution with this "bar" is 6.9% FWHM at 662 keV.
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With a custom detector, a single Gamma-Rad5 module can provide neutron detection while measuring the gamma-ray spectrum. The key is the use of a “Phoswich” detector, a sandwich of two scintillators mated to a single photomultiplier tube. A LiI(Eu) crystal is added to the standard NaI(Tl) scintillator. The NaI(Tl) measures the gamma-ray spectrum. The lithium is enriched in 6Li, providing for efficient detection of neutrons via the 6Li(n,a) reaction. The two scintillators produce different pulse shapes, so the DP5G’s pulse shape discrimination is used to distinguish between them.
Figure 12.
Figure 13. 60Co Spectrum
Figure 14. 137Cs Spectrum.
Figure 15. 22Na Spectrum.
Figure 16. 133Ba Spectrum.
Figure 17. 57Co Spectrum.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23. GAMMA-RAD5 76 x 76 mechanical dimensions. The NaI is surrounded by 1.5 mm thick aluminum from the front and side.
Figure 24. GAMMA-RAD5 Back Panel Connections. External power is only needed when using Ethernet. When using USB, the Gamma-Rad5 is powered by the USB.
The GAMMA-RAD has been replaced by the GAMMA-RAD5The GAMMA-RAD5 uses an enhanced digital processor, the DP5G, while the GAMMA-RAD used Amptek’s DP4.
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GAMMA-RAD5 Specifications PDF (810 k)
Gamma-Rad5 Frequently Asked Questions (FAQ) (50 k)
Application Note AN-GRD-001: How Sensitive is the Gamma-Rad5? (250 k)
Presentation on shipping container system.
Paper on shipping container system.
Glossary (100 k)
Revised November 28, 2011
