I'll mail you some fine Si powder if you send me your address. My best guess is that you have a relatively big lump of Si in your sample that happens to be lined up to make a bright spot from the bremstrahlung part of the spectrum. It happens to meet some Si Bragg reflection condition for some wavelength in the brems. spectrum.
^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~ Peter W. Stephens Professor, Department of Physics and Astronomy Stony Brook University Stony Brook, NY 11794-3800 fax 631-632-8176
