In News:

The Tamil Nadu State Department of Archaeology (TNSDA) has sent 23 charcoal samples from seven archaeological excavation sites to the Beta Analytic Laboratory in the United States for Accelerator Mass Spectrometry (AMS) dating, aiming to establish an accurate chronology of the cultural deposits unearthed during the 2024–25 excavation season.

Key Discoveries:

• Keeladi: Over 500 antiquities, 100 inscribed potsherds, including red-slipped ware with fish motifs.
• Porpanaikkottai: From 11 trenches, 1,792 antiquities such as pottery, glass beads, and bangles were found.
• Tirumalapuram: A stone slab chamber with urn burials—a first in Tamil Nadu’s megalithic excavation record.

What is AMS Dating?

• A high-precision radiocarbon dating technique that measures the Carbon-14 (C-14) content in archaeological samples.
• Unlike conventional radiometric methods, AMS counts individual atoms of C-14, not their radioactive decay.

How It Works:

• Sample Preparation: Organic samples like charcoal are chemically treated and converted to graphite.
• Ion Generation: A cesium beam bombards the graphite, generating negatively charged carbon ions.
• Acceleration: Ions are propelled by a tandem electrostatic accelerator to high kinetic energies.
• Stripping & Detection:
  • Ions pass through a stripping chamber to become positively charged.
  • Magnetic fields separate C-12, C-13, and C-14 isotopes based on mass.
  • C-14 atoms are counted to calculate the sample’s age.

Advantages of AMS Dating:

Applications of AMS:

• Archaeology: Dating of charcoal, wood, bones, pottery layers.
• Climate Science: Carbon mapping in marine and sediment systems.
• Geology/Oceanography: Sediment and core dating.
• Biomedical Research: Drug microdosing, tracing labeled compounds.