Study on space charge effect in an electrostatic ion analyzer applied to measure laser produced ions.
The abundance of different ions produced by laser ion sources is usually analyzed by an electrostatic ion analyzer (EIA). Ion current intensities in the range of several mA/cm(2) at the position of the EIA have been achieved from the laser ion source developed by the Institute of Modern Physics; this indicates that a noticeable influence of space charge effect during the ion transmission will occur. Hence, while the parameters of the EIA or the beams are changed, such as ion species, current intensity, the ions' transmission efficiency through the EIA is different, which will result in an uncertainty in the estimation of the ions' yields. Special attention is focused on this issue in this paper. Ion's transmissions through the EIA under different circumstances are studied with simulations and experiments, the results of which are consistent with each other.
Absolute energy distributions of Al, Cu, and Ta ions produced by nanosecond laser-generated plasmas at 1013 W cm−2
The charge state and energy distributions of ions produced by a pulsed 1 J, 9 ns Nd:YAG laser focused onto solid aluminum,copper, and tantalum targets were measured with an electrostatic analyzer coupled with a windowless electron multiplier detector. Special attention was paid to the detector response function measurements and to the determination of the analyzer transmission. Space charge effects are shown to strongly affect this transmission. Measured absolute energy distributions are presented for several charge states. They follow Boltzmann-like functions characterized by an effective ion temperature and an equivalent accelerating voltage. These parameters exhibit power laws as a function of I λ2 which open the possibility to predict the expected shape of the relative energy distributions of ions on a large range of laser intensities (106–1016 W cm−2 μm2).
A multichannel ion mass spectrometer in laser‐produced plasma studies
The theory and operation of a time‐of‐flight mass spectrometer employing a multichannel electrostatic analyzer are discussed with emphasis placed on laser‐produced plasma studies. It is shown that the finite length of the analyzer leads to enhanced mass resolution. A method of in situ calibration of the analyzer channels is described, and measurements of the resolution and beam divergence are presented. Use of the mass spectrometer to calibrate ion‐collecting probes for mass and kinetic energy measurements is also considered.