The applied voltages on the ion optical and reflectron system were predicted by ion optical simulations and are taken as an initial set for the further voltage optimisation procedure controlled by a dedicated and self-written code based on an adaptive swarm algorithm. The signals generated in the MCP are collected by four concentric anode rings. The ions arrive at the MCP detector in sequence, at times proportional to the square root of their mass-to-charge ratio (m/q).
Samples are placed on a sample holder mounted on a XYZ micro-translational stage and are positioned at a fixed distance (~1 mm) from the entrance (grounded) plate.
The laser fluence iscontrolled by use of a polarisation-sensitive attenuator, and laser irradiance in the range 0.1–1 GW/cm2 is usually used (ablation mode).
The laser system initiates the experimental cycle and triggers the data acquisition. The spectra are recorded with two dual–channel, 8-bit PCIe/PCI high-speed digitizer with on-board signal processing ADC card. In single-channel mode acqusiition a sampling rate of 4 GS/s with an analogue bandwidth of 1.5 GHz is possible. Typically, the spectra are recorded in the mass range 0–250 amu/q,which corresponds to flight times up to ~14 μs .