NEC began building AMS systems over 30 years ago and is one of the premier manufacturers of AMS systems in the world. Of the more than 55 AMS systems provided to customers, over half are dedicated to radiocarbon measurements in the fields of Archaeology, Geology, Groundwater analysis, Metabolite profiling, Microdosing, Atmospheric sciences, Oceanography, Nuclear waste management, Toxicology, Cosmogenic study, Astrophysics, Pharmacokinetics, and many more.
NEC offers the Single Stage Accelerator Mass Spectrometry (SSAMS) and Carbon Accelerator Mass Spectrometry (CAMS) systems for carbon-based AMS. The NEC SSAMS is based around a 250 kV high voltage deck for beam energies around 285 keV. The NEC CAMS is based around a 0.500 MV tandem Pelletron for beam energies around 1 MeV.
Both systems are optimized for world-class precision, superb throughput, and low background of radioisotope samples. The NEC carbon-based AMS Systems are complete systems with all necessary hardware and software for both on-line and off-line radiocarbon isotope measurements.
The following design elements are true of both the NEC SSAMS and CAMS systems.
Once a sample has been appropriately processed and inserted into the ion source (either as graphite or CO2), the sample is converted to negative ions and is accelerated through the first bending magnet. This first mass spectrometer has a biased chamber to allow sequential injection of the negative ions of interest, allowing low energy 12C- and 13C- to be measured in offset Faraday cups. As the negative ions exit the magnet, they accelerate to higher potential energy (around 285 keV for the SSAMS, around 0.500 MeV for the CAMS) into a gas stripper that breaks up negative molecules and converts the resulting single nuclei ions to positive such ions as 12CH-, 12CH2-, 13CH-, and others are converted to single nuclei ions, 12C+, 13C+, and 14C+. This eliminates interferences that might be caused by molecular ions when counting 14C+ ions later in the system.
In the SSAMS, the higher energy ions pass through the second spectrometer, resulting in an improved mass separation, allowing the abundant isotopes 12C+ and 13C+ to be measured with high precision current integrators. In the CAMS, the positive ions are then accelerated again to ground potential to the entrance of the second mass spectrometer, resulting in an improved mass separation, allowing the abundant isotopes 12C+ and 13C+ to be measured with high precision current integrators.
The rare isotope 14C+ continues through a 90° electrostatic spherical analyzer (ESA) which removes any outstanding interferences and the beam is measured in a solid state particle detector. NEC AMS systems include full computer control with AMS analysis software to provide chronological ages, carbon content in dpm/gm, or pMC (percent modern carbon) values.
NEC AMS systems can support several configurations from a single, 40 sample source, to dual 134 sample sources for a maximum throughput of 2,000 samples to 2% precision per week. Sample wheel loading takes less than 30 minutes with full 40 sample wheels typically measured to precision within about 24 hours. NEC ion sources have no noticeable memory effects and are extremely reliable. NEC has provided more than 125 MC-SNICS sources around the world.
The carbon AMS systems proceed automatically to switch from sample to sample as the required precisions, time constraints, or other criteria are met. The system can be monitored remotely and is fully interlocked in case of power, water, or air failure to protect personnel and precious samples.
The CAMS is a higher energy system, with higher filtering capabilities. The CAMS has a better background and can analyze a sample in as soon as 10-15 minutes. The SSAMS, in comparison, has lower beam currents and has an analysis range of 15-30 minutes. Additional specifications are featured below.
SSAMS |
CAMS |
|
| HV Deck | ||
| Voltage Range: | to 250 kV @ 1ma | Model 1.5SDH-1: to 0.500 MV |
| Single Charged Energy Range: | to 285 keV | Model 1.5SDH-1: to 1.000 MeV |
| Voltage Stability | 0.01% per hour after 1/2 hour warmup | Better than 1 kV |
| Primary Components | ||
| Beamline Height: | 1.4 m (40 MC-SNICS) or 1.5 m (134 MC-SNICS) | 1.5 m |
| Pumps: | Turbo molecular pumps, rough backing pumps | Turbo molecular pumps, rough backing pumps |
| Vacuum System Base: | 5e-7 Torr, or better (without beam) | 5e-7 Torr, or better (without beam) |
| Ion Source(s)/Injector: | Injection voltage, ~30-40 keV
40 or 134 MC-SNICS (carbon) |
Injection voltage, ~50 keV
40 or 134 MC-SNICS (carbon) |
| Acceptance Test Values | ||
| Carbon, Terminal Potential: | 250 kV | 0.5 MV |
| 12C- (Pulsed Beam): | Current > 40 µA | Current > 40 µA |
| Beam Transmission: | > 40% | > 40% |
| 14C/12C (abundant ratio 1e -12) | Precision < 0.2% |
| 13C/12C (abundant) | Precision < 0.2% |
| 14C/12C (background) | Ratio < 1e-15 |
| 14C/12C (CO2 abundant) | Precision < 0.8% |
| 14C/12C (CO2 background) | Ratio < 8e-15 |
| 14C/12C (abundant ratio 1e -12) | Precision < 0.2% |
| 13C/12C (abundant) | Precision < 0.2% |
| 14C/12C (background) | Ratio < 7e-16 |
| 14C/12C (CO2 abundant) | Precision < 0.8% |
| 14C/12C (CO2 background) | Ratio < 8e-15 |
For pricing inquires for NEC carbon-based AMS Systems, contact us.
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