Agilent Technologies NovoCyte Quanteon Operator's Manual page 39

Introduction
During sampling, do not obstruct the moving SIP. Do not place your hand on
WARNING
the test tube.
The sample injection probe directly contacts biological samples which may
WARNING
be biohazardous. Wear gloves when handling the sample injection probe.
Driving pumps
A sheath pump is used to drive the sheath fluid at a constant flow rate (e.g. 6.5
mL/min). A high precision syringe pump is used to drive the sample.
Flow Cell
When the sample flows into the flow cell, it will be hydrodynamically focused by
the sheath fluid to align it with the interrogation point of the laser beam.
Sampling Method and Sample Flow Rate Control
Agilent flow cytometer uses a high-precision syringe pump to aspirate the sample
and drive it into the flow cell for analysis. This sampling method can precisely
control the volume of the sample for accurate volumetric counting results.
During sampling, a certain volume of the sample set by the user in the
NovoExpress software, plus an additional overhead volume, is first aspirated by
the syringe pump from the sample tube through the sample injection probe. Then
the syringe pump will push the aspirated sample into the flow cell to be analyzed.
The sample is hydrodynamically focused by the sheath fluid to form a small
stream inside the flow cell.
The diameter of the focused sample stream (called Core Diameter) is determined
by the ratio between the sample flow rate and the sheath flow rate. When the
sheath flow rate remains constant, the lower the sample flow rate, the smaller the
core diameter, as illustrated in Figure 13.
NovoCyte Quanteon Flow Cytometer Operator's Guide 39