Photon shield for atomic hydrogen plasma sources

Atomic hydrogen sources are usually strong photon emitters. To produce an a tomic hydrogen beam and suppress the undesired photon flux, a small but eff ective light blocking device has been developed which fits into the quartz tube of a hydrogen plasma source. The device is made of stainless steel and uses angled passages and offset throughholes to absorb plasma generated ph otons while permitting hydrogen atoms and molecules to pass. The photon flu x was reduced by a factor of at least 10(4), whereas an attenuation of the H atom flux was not observed. By measuring the average velocity of the H at oms passing through the light blocker it has been shown that this device in the microwave plasma tube produces a room temperature thermalized atomic h ydrogen beam. (C) 1999 American Vacuum Society. [S0734-2101(99)02302-7].