High-order harmonic suppression by a glass capillary array

A glass capillary array with a rectangular cross-section of each individual capillary has been tested as a high-harmonic suppressor for synchrotron radiation beamlines. Using double reflection in the capillary, the high harmonics of a double-crystal Si (1 1 1) monochromator were reduced by a factor of 10−4–10−5 from their initial value. The beam spread due to glass surface roughness was measured to be ∼30 arcsec. A first harmonic transmission efficiency of 35% was measured at 7500 eV.