XIA UltraLo-1800 User Manual page 70

Anode\Guard Baseline
Baseline Noise Event
Noise Noise Event
Negative Charge Neg. Charge Event
Alpha-like Further Analysis
Table II: Table of anode and guard trace classification pairings and the resulting event classification. Anode classifications are shown
in red, Guard in blue.

Trace pairs that require Level One analysis:
o Alpha: If an event is classified as an alpha that means that, to our best ability to
discriminate, it was caused by an alpha particle emission from the sample area under
the anode electrode.
o Midair: Midairs are events whose risetime is too short to be an alpha, but too long to be
a ceiling. They are caused by interactions in the bulk of the counting gas, mostly from
radon but also from cosmic rays.
o Round: Rounds are events whose peak is too rounded to be caused by alpha particle.
These are the result of particles that can cause longer ionization tracks, most likely
cosmic rays.
o Ceiling: An alpha decay emanating from the electrode.
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