The STAR TPC nominally operates with P10 (90% Ar, 10% methane by volume) at ~2 mbar above the ambient atmospheric pressure with an electric field of ~148 V/cm and a temperature of ~75F=23.9C. The tables below give some idea of the effect of small deviations from a perfect mixture.
The tables below were calculated by Roy Bossingham using Magboltz 2, V3.1 (Biagi, 2000) for parameters relevant to STAR: T=23.9C and P=760 Torr, with B and E parallel and concentrated near common values. Magboltz 2 uses Monte Carlo methods, with the statistics determined by the collisions parameter. The tables were calculated with statistics corresponding to collisions=120, or higher, giving a precision of at least 0.04% in drift velocity and 1.6% in diffusion.
Drift velocity vs E for P9, P10 and P11 at P=760 Torr, with E parallel to B.
Transverse diffusion vs E for P9, P10 and P11 at B=5 kG and P=760 Torr, with E parallel to B.
E (V/cm) |
E/P (V/cm-Torr) |
V (cm/us) |
Sigma_L (um/sqrt(cm)) |
Sigma_T(B=5 kG) (um/sqrt(cm)) |
||||||
P9 | P10 | P11 | P9 | P10 | P11 | P9 | P10 | P11 | ||
100 | 0.1316 | 5.119 | 5.239 | 5.322 | 426 | 427 | 423 | 200 | 191 | 184 |
118 | 0.1553 | 5.246 | 5.434 | 5.568 | 393 | 395 | 391 | 220 | 209 | 197 |
128 | 0.1684 | 5.271 | 5.477 | 5.648 | 371 | 379 | 374 | 227 | 218 | 207 |
138 | 0.1816 | 5.250 | 5.487 | 5.685 | 373 | 363 | 362 | 239 | 227 | 221 |
148 | 0.1947 | 5.230 | 5.472 | 5.692 | 357 | 356 | 357 | 249 | 240 | 224 |
158 | 0.2079 | 5.183 | 5.453 | 5.685 | 352 | 341 | 350 | 261 | 250 | 233 |
168 | 0.2211 | 5.102 | 5.393 | 5.639 | 344 | 330 | 333 | 273 | 255 | 243 |
178 | 0.2342 | 5.049 | 5.348 | 5.602 | 325 | 330 | 332 | 279 | 260 | 253 |
188 | 0.2474 | 4.978 | 5.348 | 5.539 | 336 | 339 | 327 | 297 | 270 | 263 |
200 | 0.2632 | 4.880 | 5.189 | 5.469 | 319 | 323 | 321 | 296 | 289 | 269 |
Calculated drift velocity and diffusion in P9, P10 and P11
as a function
of E/P for parallel E and B at P=760 Torr and T=23.9C .
Drift velocity vs methane fraction at E=148 V/cm and P=760 Torr, with E parallel to B.
Transverse diffusion vs methane fraction at B=5 kG and P=760 Torr, with E parallel to B.
F (% CH4) |
V (cm/us) |
Sigma_L (um/sqrt(cm)) |
Sigma_T(B) (um/sqrt(cm)) |
||
B=5.0 kG | B=2.5 kG | B=0.0 kG | |||
6.0 | 4.201 | 377 | 311 | ||
7.0 | 4.593 | 377 | 287 | ||
8.0 | 4.935 | 364 | 270 | 379 | 614 |
9.0 | 5.230 | 357 | 249 | 363 | 594 |
10.0 | 5.472 | 356 | 240 | 346 | 575 |
11.0 | 5.692 | 357 | 224 | 335 | 556 |
12.0 | 5.876 | 353 | 217 | 324 | 530 |
13.0 | 6.040 | 349 | 211 | ||
14.0 | 6.147 | 350 | 203 |
Calculated drift velocity and diffusion as a function of methane content F
(100%-F argon) for parallel E and B at E=148 V/cm, P=760 Torr and T=23.9C .
Page created by Roy Bossingham;
maintained by .
Last modified on June 29, 2000 .