Power parameters short duration pulses

There are more advanced experiments such as DEPT (Chapter 7) that observe 13 C and use the decoupler to supply high power, short duration ( hard ) pulses at the XH frequency. This requires full power from the decoupler, but the parameters dpwr andpll7 are avoided for these pulses. Setting decoupler power to the maximum might lead to disastrous mistakes because the decoupler can only deliver full power for short ( 10 pis) periods of time without burning up the decoupler, the probe, and the sample. Instead, the parameters pp (Varian) and p3 (Bruker) are used for the 90° pulse width for decoupler hard pulses and pplvl (Varian) and pl2 (Bruker) indicate the power level for short-duration high-power decoupler pulses. 

Further important laser parameters are the pulse duration and the laser repetition rate. A short pulse duration maximizes the peak power and can reduce the thermal conduction to the surrounding material. The repetition rate can also influence the thermal impact on the material. If it is too low, the energy loss by heat conduction dominates and all of the energy not used for ablation will leave the ablation zone. Higher repetition rates lead to an increase of the average surface temperature AT which can be estimated by solving the one-dimensional heat equation for a rectangular laser pulse (Equation 8.1) [4]. 

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