A comment on `A new ray-tracing program RIGTRACE for X-ray optical systems' 
[J. Synchrotron Rad. (2001), 8, 1047-1050]

L. Alianelli, M. Sanchez del Rio, M. Khan and F. Cerrina

Some points concerning the characteristics of the X-ray simulation code 
SHADOW [Welnak et al. (1994). Nucl. Instrum. Methods, A347, 344-347] are 
clarified which are not correctly mentioned by Yamada et al. [J. Synchrotron 
Rad. (2001), 8, 1047-1050]. It is shown that, contrary to the authors' 
statement, some functionality of their new program is not original. In 
particular, we show that SHADOW can deal correctly with crystal monochromators.

Keywords: ray-tracing; X-ray optics.