Physics and Engineering of Radiation Detection

228 Chapter 4. Liquid Filled Detectors

Figure 4.1.7: Variation of electron drift velocity with elec-

tric field strength for liquefied argon (T=87K) with addi-

tions ethane in concentrations of 5. 5 × 1019 cm−^3 (circles),

8. 7 × 1019 cm−^3 (filled squares), and 5× 1020 cm−^3 (empty

squares). Solid line represents pure argon (32).

Table 4.1.2: Electron mobilitiesμeand saturation velocitiesvsof the three liquefied
noble gases that are commonly used in radiation detectors at different absolute
temperatures (32).

Liquid T(K) μe(cm^2 V−^1 s−^1 ) vs(cm s−^1 )

Liquid Argon 87 400 ± 50 6. 4 × 105

85 475 7. 5 × 105

Liquid Krypton 120 1200 ± 150 4. 5 × 105

117 1800 3. 8 × 105

Liquid Xenon 165 2000 ± 200 2. 6 × 105

163 1900 2. 9 × 105

As in case of gases, in liquids too the drift velocity is proportional to the applied
electric field, that is

vd=μionE, (4.1.3)