Unidirectional spark

Mulhsouive 1000 Peak discharge currents from 5 to in excess of 500 A at time constants ranging from 8 to less than 1 ms. Sensitive and precise. Parameter selection allows wide variety of controlled unidirectional and oscillatory charges variable from arc-like 10 spark like in spectral excitation. 

Another method often employed is to minimize vaporization differences by using a spark-type of excitation which introduces the sample into the excitation zone by a sputtering process. At the Ames Laboratory, this second approach has been emphasized. Uniarc excitation, which is a combination of a spark and a unidirectional ac arc, has provided reliable analyses with adequate sensitivity for many impurities in most of the rare earth elements, and with a precision of better than 10%. A briquetted sample of one part rare earth oxide mixed with nine parts of pelleting graphite is used. The complex rare earth matrix spectra often causes spectral interference with the more sensitive spectral lines of impurity elements. For Pr and Nd, which have the most complex spectra, this problem is particularly serious, and alternate analytical approaches must be used if determinations at lower concentration levels are required. 

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