13
Light sources: The argon laser is the standard light source of laser-based flow cytometers.
The large research instruments employ water-cooled lasers with a nominal output, that is, total
power of all emission lines combined, of 2 to 5 W. These lasers can be tuned so as to emit
at any of the emission wavelengths shown in Fig. 4A, although tuning to the lines in the UV,
i.e. around 350 nm, may require some optional equipment. These lasers typically have a
ripple below 1 % and good long term stability. However, they are expensive to buy and run.
They consume 10 to 15 kW of electrical power and 2 to 4 gal/min of cooling water. With a
plasma tube of about one meter in length they are susceptible to mechanical shock and
vibration. Much smaller, air-cooled argon lasers are used in analytical instruments which are
intended primarily for measurement of fluorescence conjugated antibodies on leucocytes and
other mammalian cells (FACSscan, Becton Dickinson, San Jose, California, and Profile,
Coulter Electronics, Inc., Hialeah, Florida). The lower emission power of these lasers, i.e.
typically 10 to 50 mW, is partly compensated by the use of closed flow chambers and
til
til
C
CIl
- C
-
A
B
300
350
435
405
546
400
L,50
500
550
600
Wavelength (nm)
Figure 4. The emission lines of a tunable argon laser (A) and the emission spectrum of a high pressure mercury
arc lamp (B). The scale of intensity is not the same in the two panels. The wavelengths of some of the most
prominent lines are noted.
Light sources: The argon laser is the standard light source of laser-based flow cytometers.
The large research instruments employ water-cooled lasers with a nominal output, that is, total
power of all emission lines combined, of 2 to 5 W. These lasers can be tuned so as to emit
at any of the emission wavelengths shown in Fig. 4A, although tuning to the lines in the UV,
i.e. around 350 nm, may require some optional equipment. These lasers typically have a
ripple below 1 % and good long term stability. However, they are expensive to buy and run.
They consume 10 to 15 kW of electrical power and 2 to 4 gal/min of cooling water. With a
plasma tube of about one meter in length they are susceptible to mechanical shock and
vibration. Much smaller, air-cooled argon lasers are used in analytical instruments which are
intended primarily for measurement of fluorescence conjugated antibodies on leucocytes and
other mammalian cells (FACSscan, Becton Dickinson, San Jose, California, and Profile,
Coulter Electronics, Inc., Hialeah, Florida). The lower emission power of these lasers, i.e.
typically 10 to 50 mW, is partly compensated by the use of closed flow chambers and
til
til
C
CIl
- C
-
A
B
300
350
435
405
546
400
L,50
500
550
600
Wavelength (nm)
Figure 4. The emission lines of a tunable argon laser (A) and the emission spectrum of a high pressure mercury
arc lamp (B). The scale of intensity is not the same in the two panels. The wavelengths of some of the most
prominent lines are noted.