The drift cell is shown below. It is made of copper
and has a drift length of 4 cm with a diameter of 1.52 cm. The entrance
and exit plates are made of molybdenum with orifice diameters of 0.1 cm.
The electric field is produced by a voltage difference between the two
ends of the cell. This field is kept uniform throughout the cell by supplying
the appropriate intermediate voltages to a series of 8 guard rings via
a chain of resistors. Field strengths can be varied from 5-25 V/cm.
The temperature of the cell can be varied from
80-600 K by controlling the flow rate of cooled or warmed nitrogen through
passages surrounding the cell. The nitrogen is cooled by flowing the gas
through two sets of coils immersed in liquid nitrogen. The temperature
can be routinely maintained at ± 2 K by controlling the flow rate.
The nitrogen is heated by two 200 W in-line heaters. Temperature maintenance
by this method is usually ± 1 K.
For more details concerning this drift cell and
the optics involved with it, see P.
R. Kemper, M. T. Bowers; J. Am. Soc. Mass Spectrom. 1990,