Tunable coherent radiation in the soft x-ray and extreme ultraviolet spectral regions
- Lawrence Berkeley National Lab., CA (United States)
- Lawrence Berkeley National Lab., CA (United States); and others
Undulator radiation, generated by relativistic electrons traversing a periodic magnet structure, can provide a continuously tunable source of very bright and partially coherent radiation in the extreme ultraviolet (EUV), soft X-ray (SXR), and X-ray regions of the electromagnetic spectrum. Typically, 1--10 W are radiated within a 1/N relative spectral bandwidth, where N is of order 100. Monochromators are frequently used to narrow the spectral bandwidth and increase the longitudinal coherence length, albeit with a more than proportionate loss of power. Pinhole spatial filtering is employed to provide spatially coherent radiation at a power level determined by the wavelength, electron beam, and undulator parameters. In this paper, experiments are described in which broadly tunable, spatially coherent power is generated at EUV and soft X-ray wavelengths extending from about 3 to 16 nm (80--430-eV photon energies). Spatially coherent power of order 10 {micro}W is achieved in a relative spectral bandwidth of 9 {times} 10{sup {minus}4}, with 1.90-GeV electrons traversing an 8-cm period undulator of 55 periods. This radiation has been used in 13.4-nm interferometric tests that achieve an rms wavefront error (departure from sphericity) of {lambda}{sub euv}/330. These techniques scale in a straightforward manner to shorter soft X-ray wavelengths using 4--5-cm period undulators at 1.90 GeV and to X-ray wavelengths of order 0.1 nm using higher energy (6--8 GeV) electron beams at other facilities.
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Defense Advanced Research Projects Agency, Arlington, VA (United States); Department of the Air Force, Washington, DC (United States)
- OSTI ID:
- 343658
- Journal Information:
- IEEE Journal of Quantum Electronics, Journal Name: IEEE Journal of Quantum Electronics Journal Issue: 5 Vol. 35; ISSN 0018-9197; ISSN IEJQA7
- Country of Publication:
- United States
- Language:
- English
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