text: The initial laser systems used during the development of laser peening were large research lasers providing high-energy pulses at very low pulse frequencies. Since the mid-late 1990s, lasers designed specifically for laser peening featured steadily smaller size and higher pulse frequencies, both of these more desirable for production environments. The laser peening systems include both rod laser systems and a slab laser system. The rod laser systems can be separated roughly into three primary groups, recognizing that there is some overlap between them: (1) high-energy low-repetition rate lasers operating typically at 10–40 J per pulse with 8–25 ns pulse length at nominally 0.5–1 Hz rep rate, nominal spot sizes of 2 to 8 mm; (2) intermediate energy, intermediate repetition rate lasers operating at 3–10 J with 10–20 ns pulse width at 10 Hz rep rate, nominal spot sizes of 1–4 mm; (3) low-energy, high-repetition rate lasers operating at  per pulse with ≤10 ns pulse length at 60+ Hz rep rate,  spot size. The slab laser system operates in the range of 10–25 J per pulse with 8–25 ns pulse duration at 3–5 Hz rep rate, nominal spot sizes of 2–5 mm. The commercial systems include rod lasers represented by all three groups and the slab laser system.
  For each laser peening system the output beam from the laser is directed into a laser peening cell containing the work pieces or parts to be processed. The peening cell contains the parts handling system and provides the safe environment necessary for efficient commercial laser peening. The parts to be processed are usually introduced into the cell in batches. The parts are then picked and placed in the beam path by robots or other customized parts handling systems. Within the work cell, the beam is directed to the surface of the work piece via an optical chain of mirrors and/or lenses. If tape is used, it is applied before the part enters the work cell, whereas water or RapidCoater overlays are applied within the cell individually for each spot. The workpiece, or sometimes the laser beam, is repositioned for each shot as necessary via a robot or other parts handling system. When the selected areas on each part have been processed, the batch is replaced in the work cell by another.