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This is the second in a series of publications to examine the feasibility of tests for gunshot residue based on volatile or volatilizable organic constituents (VOC), either present in the original smokeless powder formulation or produced during firing.

A quick, convenient, and reliable test for detecting gunshot residue is needed to cope with the increasing number of crimes involving handguns. Chemical color tests for nitrates [1] and for antimony, barium, and lead [2] have been used, but these methods lack the required sensitivity and specificity for forensic purposes. Two instrumental techniques, neutron activation analysis and atomic absorption, have found some acceptance by crime laboratories. Neutron activation analysis has been used to detect antimony and barium in hand samples [3], but it suffers from the drawbacks that samples must be sent out for analysis and that it is insensitive to lead. Atomic absorption has been used to detect lead by flame atomization [4], and antimony and barium have been detected with a flameless atomizer [5]. This approach has extended the availability of gunshot residue analysis. However, the costs still limit the number of laboratories with the required equipment. Perhaps a more serious limitation of any technique that is based on the bulk amounts of antimony, barium, or lead on a person's hands is the possibility of environmental or occupational sources of these elements on the hands. This limitation requires setting a threshold often higher than the amount deposited by firing. Furthermore, the amount of residue on the hand declines very rapidly with time.

A high-speed squirrel-cage induction machine requires a totally different design compared to the traditional squirrel cage industrial motor because of the mechanical limitations caused by the high speed. This results in a more complicated rotor construction and expensive material selection, and sets higher standards for the manufacturing precision. The objective of this paper is to demonstrate the design aspects, material selection, and manufacturing of a squirrel cage rotor for high-speed applications. In this paper, the rotor dimensioning approach based on equations and data analysis is presented. Rotor material selection and construction topology influence on the electrical machine design are discussed. The results are illustrated with the design of a 6 kW, 120 000 rpm induction machine for a turbo-circulator. The rotor parameters' influence on the electromagnetic performance of the designed machine is demonstrated. Mechanical stresses for different topologies are studied with Finite Element Method (FEM) analysis. Several manufacturing methods for producing a high precision rotor are described and compared. The presented rotor design approach, which enables high electromagnetic performance and robust construction, is verified by the testing of a prototype.

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