Page 93 - High Power Laser Handbook

62 G a s , C h e m i c a l , a n d F r e e - E l e c t r o n L a s e r s Chemical Lasers 63

Pulsed HF and DF Lasers
Both HF and DF pulsed devices have been constructed. Typically, when
H (D ) and F are used, they rely on premixing with inhibitor gases,
2
2
2
which are present to suppress premature reaction. A chain reaction is
initiated via electrical production of either an electric discharge or a
photolytic source. As Table 3.1 suggests, once one decides to use electrical
initiation of the reaction, a wealth of alternatives are available for
reactants. For laboratory applications, these alternatives (e.g., SF ) may be
6
much more attractive than the more conventional, efficient, but poten-
tially more hazardous, reactants. When high average power is desired, an
added difficulty arises. In this case, it is necessary to achieve a suitably
high repetition rate. In practice, as the repetition rate and pressure increase,
there is another challenging flow problem associated with quickly remov-
ing the previous pulse reaction products and heat. In the frequently used
continuous-flow systems, one must either waste reactants or cope with
some pressure feedback effects from the previous pulse.
3.3.7 HF and DF Laser Performance
The development of high-power HF and DF lasers began in the early
1970s and continued throughout the 1980s and 1990s, with the devel-
opment of several multihundred kilowatt- to megawatt-class lasers.
These included the Baseline Demonstration Laser (BDL) and the Navy-
ARPA (Advanced Research Projects Agency) Chemical Laser (NACL),
both built in the late 1970s; the MIRACL built in the early 1980s
(Fig. 3.17); and the Alpha laser, developed by the U.S. Air Force in the

Figure 3.17 Mid-Infrared Advanced Chemical Laser.