INAA

1
INAA

• Roy Adams
• Sara Ehlers
• Jared Gillen
• Dan Kolb
• Andrew Pritchard
• Christina St.James
• Lisa Yang

2
How It Works

• Sample is irradiated.
• The elements within the sample begin to decay
• During decay, radiation is given off.
• Time type and quantity of radiation is measured
• Based on measurements, quantity of element can be
  determined.

3
Irradiation

• Incident neutron collides with the target
  nucleus.
• Compound nucleus forms, very high activity.
• Compound nucleus settles into a less active state
  (decay)
• Gives off radiation, specific to its element.

4
Detection Limits

• About two - ten percent accuracy depending on the
  sample.
• There are almost no limits as to what can be
  measured.

Preparation

• Little to no preparation is required
• When comparing various samples it is suggested
  that samples be ground to the same or similar
  volume.
• This is in no way necessary.

5
Sources of error

• Counting statistic error
• Unresolved interference
• Self-shielding phenomenon

6
Unresolved Interference

• High concentration of an element could mess up
  the amount of arsenic in the soil

7
Counting Statistic Error

• When the Arsenic is irradiated, other elements
  around it are also irradiated.
• The measurements sometimes pick up on these
  levels. The measurements are inaccurate because
  of the other elements.

8
Self-Shielding

• An element with high concentration could block
  the gamma-ray which would cause the element to
  not radiate.