The authors have presented the motivations in gathering doubly polarized data in the quasi-elastic, resonance and DIS domains. These data were used to calculate the extended GDH integral. The comparison of this quantity with the spin dependent forward Compton amplitude {bar S}{sub 1} is of particular importance for the unification of the two strong interaction descriptions (nucleonic/hadronic vs. partonic) because {bar S}{sub 1} is the first quantity theoretically calculable in the full Q{sup 2} domain of the strong interaction. Such a data taking was made possible because of three major technical achievements: (1) the beam of high duty cycle (100%), high current (up to 70 {micro}A) and high polarization (70%); (2) the {sup 3}He target of high density (above 10 atm) with a polarization of 35% and a length of 40 cm; and (3) the large acceptance (6 msr) and high resolution ({Delta}P/P {approx_equal} 10{sup {minus}4}) spectrometers. These features, available at Jefferson Lab, enabled them to achieve the highest luminosity in the world (about 10{sup 36} s{sup {minus}1} cm{sup {minus}2} with a current of 15 {micro}A) as far as polarized {sup 3}He targets are concerned. Consequently they were able to gather, in a rather short period of time (3 months), …

A stable carbon arc operated in controlled atmosphere is described. The arc was designed to serve as a light source during lifetime studies of the B/sup 2/ SIGMA state of the CN molecule. The CN radiation from the plasma of the arc was investigated and found to have a brightness temperature of 5500 icient laborato K at lambda 3883 A. This is considerably higher than an estimate of the value required for lifetime measurements. The stability of the carbon arc under various conditions is discussed. For successful lifetime measurements, the light source employed must have a high brightness temperature (intensity). A method for the determination of the brightness temperature of a light source at a specific wave length is described. The method was used for determining the brightness temperatures of some available light sources. Sodium, thallium, and mercury discharge lamps, a medium-pressure mercury arc lamp, and the carbon arc were studied. (auth)