The trigger conditions are presented for a scheme in which heavy ions or macroparticle impact are used to ignite a laser compressed cold fuel. The value of this scheme, in the framework of energy production, is favourable when compared with the conventional one, where ignition is provided by a central hot spot formed by the implosion process itself. In fact, the gain in this new scheme is, in principle, high enough to make the present solid state laser efficiencies nearly adequate for target compression (not repetition rate). The values of trigger energy have been deduced by extensive theoretical and computational investigations. As an example, to ignite a 200 g/cm3 DT fuel a 40 kJ ion beam burst (15 GeV bismuth) or a 12 kJ gold macroparticle (0.97 mu g, with a velocity of 5*108 cm/s) is found sufficient. These studies allow the dimensioning of possible new trigger drivers required for these applications. As the laser energy used for compression is much larger than the trigger energy, it is possible to adopt triggering drivers much less efficient than the lasers used for fuel compression, yet satisfying the reactor loop conditions