Problem raith SNF 2005-02-15 17:24:20: 20 um aperture scatter when blanked is above spec.

jwc at jwc at
Tue Feb 15 17:24:21 PST 2005

Today I made further measurements of the blanked emission value or scatter coming down the column. 
EHT I values at 10 kV 20 um aperture, 5 mm WD.
EHT I values with beam centered in faraday cup at 600X mag.
Both RAITH and LEO Blanked: 
min 0.0003  max 0.0006 nA  typically  0.0005 nA
(up from 0.0003 nA observed in past.
Raith blanked and LEO unblanked:
min 0.0019 - 0.0021 typically 0.0020 nA
Raith unblanked and LEO unblanked 0.0693 nA and stable.
This is ~2.88% level when the specification is less than 0.5% emmision when blanked of the Beam I total value unblanked.
JWC 02152005:17:25:00

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