Proposed Flash X-Ray System for X-Ray Diffraction With Submicrosecond Exposure Time

Abstract

X-ray diffraction studies have generally used low current, low voltage X-ray tubes (e.g., 50 mA, 50 kV). Consequently, exposure times ranging from seconds to hours have been required, limiting X-ray diffraction techniques to the study of essentially static situations. Using such an X-ray source with a very high speed detector, R. E. Green was able to reduce the exposure time for laue patterns of aluminum crystals to a minimum of 0.003 sec. Nanosecond exposure and pulse timing are required for certain events, e.g., X-ray diffraction study of material under shock compression. Q. Johnson achieved this by using a low voltage, very high current flash X-ray source (approximately 50kV, 50kA, 30 nsec). However, such a system is difficult to build and to synchronize, and is not commercially available.Published X-ray yield data, particularly the recent work of J. W. Motz, indicate that both continuum and characteristic X-ray yields increase rapidly with electron energy, reaching a maximum for an electron energy ranging from 150 keV for titanium to 300 keV for copper to nearly 1 MeV for molybdenum.To take advantage of this property, a 300 kVp, 30 nsec pulse, 5 nsec jitter flash X-ray system has been built which appears to meet the intensity and timing requirements for single pulse laue or Bragg diffraction studies. System design, calculated output and initial tests are represented.