Page 81 - bukuneutron

allow the measurement of the other platinum group el-
ements in nanogram concentration.

NAA is used to monitor the level or electrically con-
ducting impurities such as Au, Na, Cu, As, Ca and W in
silicon ingots and wafers. Many other elements, bots
impurities and dopants have been analyzed in silicon
and other materials used in semiconductor manufac-
turing.

3.5.8 Applications in Forensic

INAA and RNAA have been succesfully applied to in-
vertigate samples from forensic laboratores. In most
cases trace elent concentration patterns are being used
to establish whether there is a link between a suspect
and physical evidence found at the scene of a crime.
For instance, it can be determined wheter s asuspect
has fired a weapon recently by searching for Ba and
Sb in gunshot residues on the hands. Lead bullets or
shotshell pellets can be fingerprinted by their content
of deliberately added Sb and their pattern of As, Cu,
Ag and other trace elements. But the sample variesty
may be much large than gunshot residues:glass, paint,
hair, metal, paper etc. Not only does each of therese
materials present its own difficulty and concern in anal-
ysis, but also it should be noted that sometimes only
very small amounts of materials are available which
alsi have to be kept intact to serve as a court evidence.

68