MEASUREMENTS OF X-RAY-EMISSION FROM ZINC AND MOLYBDENUM TRANSITION RADIATORS

This article describes the measurements of x-ray power, spatial and sp ectral distributions from transition radiators whose spectra are narro wed by the foil material's K-shell photoabsorption edge. We used two f oil stacks, one composed of 15 foils of 3-mum-thick Zn and the other c omposed of 15 foils of 4-mum-thick Mo. At low average currents, the x- ray spectrum produced by transition radiation was measured by pulse he ight analysis to be between 5 and 9.7 keV for the Zn radiator and betw een 10 and 20.0 keV for the Mo radiator. These measurements compared w ell with calculations. The x-ray spatial distribution from the Zn radi ator was measured using a silicon linear diode array. The x rays gener ated by the Zn radiator were found to be emitted in a forward-directed cone with half angle of approximately 1.9 mrad with the center of the expected annulus filled. The power density in the peak of the annulus was found to be 50 mW/(mA cm2). At a high average electron-beam curre nt of 12.5 muA, the x-ray power produced by a stack of ten Zn foils wa s measured in the spectral range between 5 and 9.66 keV to be 1.54 mW with the peak power in the 1 mus macropulse to be 8.5 W. Electron-beam energies between 249 and 282 MeV were used in these experiments.