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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
Multi-pulsed Systems
● A few laser systems can generate a high number of pulses each second, which may contain ‘sub-pulses’. These are known as a ‘train’ of pulses.
● Most IPL systems also produce trains of pulses although the suppliers rarely discuss it. This is due to the inherent problems with keeping the IPL’s flashlamps at the proper operating temperature. If flashlamps exceed this temperature they may stop operating properly leading to failure.
● Hence it is important to keep control of the flashlamp temperature by limiting the time they are active. This is achieved by flashing them briefly, leaving a suitable period of time (to cool), then flashing them again.
  Pulse train
Max Energy
pulsewidth             delay time
                                         Figure 36: Anatomy of a laser pulse with sub-pulses
• The outcome of clinical treatments may be strongly influenced by the timing of the pulse trains. If excessively long gaps occur between the energy sub-pulses, then too much cooling can result in the target tissues, as the heat energy conducts away.
• For this reason, the pulse train may need to be ‘altered’ to improve clinical results. This can be tricky – some devices will allow this kind of access; others will not!
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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Pulse energy (Joules)

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