The Micro Argon Detector
A diagram of the micro argon detector sensor is shown in figure 29. This sensor is designed to have a very small "effective" sensing volume to facilitate its use with capillary columns where the flow rate may be as low as 0.1 ml/min or less. In the micro argon detector sensor, the anode is withdrawn into a small cavity about 2.5 mm in diameter. This ensures that the electrons can only reach the anode along a restricted path and the electric field around the electrode resides within a few diameters of the anode tip. The anode is tubular in form and the capillary column can slide up inside the anode until it is within a millimeter or so of the electric field. Metastable argon atoms are formed as a cloud of around the anode tip and any solute molecules eluted from the column immediately pass through this cloud and are ionized.
Figure 29 The Micro Argon Detector
