The Model 642-1 generates soft x-rays between 100eV and 1500eV. In principle this source is identical to the Model 642. The exception to this is that a carousel providing six targets (anodes) allows for selection of radiation while under vacuum. This unit also provides two filter holders, one at each x-ray emission port, each with four positions.
The source of x-rays is a spot about 500 microns in diameter. The anode carousel is rotated by a 3:1 reduction gear set within the vacuum, and the rotary feedthrough has an external drive linkage which provides a direct external readout of the anode cap carousel position.