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Differentiation of Bullets by Spark Source Mass Spectrometry (CAT#: STEM-ST-0267-LJX)

Introduction

Matching of evidence bullets with a particular suspect is most frequently accomplished by comparing the striations on the evidence bullets with those on test bullets fired from the suspect's gun. This method cannot be used, of course, when the striations are obliterated or when the gun is not available for test-firing. In this case, if unspent bullets are found in possession of the suspect, they may be chemically compared with the evidence bullets. Identical elemental composition is usually taken as evidence that the bullets may have the same origin; that is, they may have come from the same box or lot.




Principle

By using vacuum spark discharge, the energy accumulated in a small volume can make the material in the volume suddenly evaporate and ionize, so as to obtain the characteristic ion current information.

Applications

(1) Solid spark source mass spectrometry: impurity analysis of high-purity materials, which can be applied to semiconductor materials, non-ferrous metals, and building materials industries;
(2) Gas isotope mass spectrometry: determination of stable isotopes C, H, N, O, S and radioactive isotopes Rb, Sr, U, Pb, K, Ar, which can be applied to geology, petroleum, medicine, environmental protection and agriculture.

Procedure

(1) An electric field is applied between the electrodes to ionize part of the carrier gas (such as argon) in the electric field;
(2) The "cathode ray" or "anode ray" generated by ionization accelerates in the direction of the opposite polarity in the residual gas, bombards the anode or cathode, and vaporizes a part of the substance to be measured on the plate;
(3) Part of the atoms of the vaporized substance are ionized in the subsequent discharge process.

Materials

• Sample Type:
Bullets

Notes

Before starting the machine, check whether the water (water cooler), electricity, gas (argon/nitrogen), temperature, humidity, and exhaust air of the instrument are normal.