. The Canadian field-naturalist. 122 The Canadian Field-Naturalist Vol. 97. Figure 2. FIG irradiation tower photographed in 1973, showing the 20 m tower, tower supports, beam stop, plantation, service road, and mixed boreal forest. branches of Balsam Fir, Jack Pine, Paper Birch and Trembling Aspen were studied in detail. Present were 518 species in 111 families. A new aphid species, Man- sonaphispinawae, was first described from specimens found on Labrador Tea growing in FIG (Robinson 1973). FIG Irradiator The irradiator, designed and built at WNRE, is located in the center of the FIG area. It
. The Canadian field-naturalist. 122 The Canadian Field-Naturalist Vol. 97. Figure 2. FIG irradiation tower photographed in 1973, showing the 20 m tower, tower supports, beam stop, plantation, service road, and mixed boreal forest. branches of Balsam Fir, Jack Pine, Paper Birch and Trembling Aspen were studied in detail. Present were 518 species in 111 families. A new aphid species, Man- sonaphispinawae, was first described from specimens found on Labrador Tea growing in FIG (Robinson 1973). FIG Irradiator The irradiator, designed and built at WNRE, is located in the center of the FIG area. It consists of a 20 m tower mounted between two supports (Figure 2) containing equipment such as an air compressor and a radiation sensor. A lead shield (castle) for the source is attached at the lower end of the tower. The tower can be tipped between its supports to lower it for mainte- nance. A triple-encapsulated '"Cs source provides the gamma radiation field. Its effective source strength was 370 TBq. (10 000 Ci) when the irradiator was placed in service in March 1973. Compressed air lifts the source from its castle to either of two irradiator positions,ponorawzc ox: beam, where it is held by an electromagnet at 20 m or 2 m heights above ground level. In the panoramic posi- tion, the '"Cs source is at the top of the tower and the entire FIG area is irradiated. In the beam position, a collimated beam of gamma radiation is directed along a trolley track into a beam stop (Figure 2). The beam position may be used for acute irradiation of flats of plants or cages of small animals placed on moveable trolleys on the track. The source is returned to its castle by switching off the electrical supply to the electromagnet at the control building, allowing the source to descend on a cushion of air. In the event of a malfunction when the source is in the beam or pano-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for
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