Inficon Transpector CPM User Manual

5–29
Transpector CPM Operating Manual
Ionization probability factors can be approximated by substituting the relative ion
gauge sensitivities for various gases. Table 5-9 lists relative ion gauge sensitivities
for some common gases.
NOTE: Table 5-9 lists relative ionization gauge sensitivities for selected
molecules. The data was compiled from Empirical Observations on the
Sensitivity of Hot Cathode Ionization Type Vacuum Gauges by R. L.
Summers (NASA Technical Note NASA TN D5285, published in 1969).
Similar, although more limited, lists of ionization sensitivities can be found
in the books by O’Hanlon, and Drinkwine and Lichtman. (See Chapter 12,
Bibliography.)
HINT: Actual ionization probabilities vary significantly depending especially on the
ionizer and the electron energy. For best accuracy, measure the relative
ionization probability using a hot cathode ionization gauge (calibrated for
nitrogen) to monitor a known pressure of the substance of interest. The
ratio of the gauge reading to the known true pressure is the relative
ionization probability. To determine the true pressure, use a gauge which is
gas species independent (e.g., a capacitance manometer) or a gauge with
a known sensitivity factor (e.g., a spinning rotor gauge).
Table 5-9 Ionization Probabilities For Some Common Substances
Substance Formula Relative
Ionization
Gauge
Sensitivity
Substance Formula Relative
Ionization
Gauge
Sensitivity
acetone (CH
3
)
2
CO 3.6 hydrogen chloride HCl 1.6
air 1.0 hydrogen fluoride HF 1.4
ammonia NH
3
1.3 hydrogen iodide HI 3.1
argon Ar 1.2 hydrogen sulfide H
2
S2.2
benzene C
6
H
6
5.9 krypton Kr 1.7
benzoic acid C
6
H
5
COOH 5.5 lithium Li 1.9
bromine Br
2
3.8 methane CH
4
1.6
butane C
4
H
10
4.9 methanol CH
3
OH 1.8
carbon dioxide CO
2
1.4 neon Ne 0.23
carbon disulfide CS
2
4.8 nitrogen N
2
1.0
carbon monoxide CO 1.05 nitric oxide NO 1.2
carbon tetrachloride CCl
4
6.0 nitrous oxide N
2
O1.7
chlorobenzene C
6
H
5
Cl 7.0 oxygen O
2
1.0
chloroethane C
2
H
5
Cl 4.0 n-pentane C
5
H
12
6.0
chloroform CHCl
3
4.8 phenol C
6
H
5
OH 6.2
chloromethane CH
3
Cl 3.1 phosphine PH
3
2.6

Inficon Transpector CPM Specifications

General

Brand	Inficon
Model	Transpector CPM
Category	Industrial Equipment
Language	English