The ornamental design for a portableplasmagenerator, as shown and described.
1. Portable plasma generator
1.1: Perspective
1.2: Front
1.3: Back
1.4: Left
1.5: Right
1.6: Top
1.7: Bottom
Figure 1.1 represents the overall shape of the design; figure 1.2 represents the front of this design; figure 1.3 represents the rear side of this design; figure 1.4 represents the left side of this design; figure 1.5 represents the right side of this design. figure 1.6 represents the plane of this design in an enlarged scale; figure 1.7 represents the bottom of this design in an enlarged scale. The portions of the portable plasma generator shown in broken lines form no part of the claimed design.