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.
Status of the laser ion source at IMP.
A laser (Nd:YAG laser, 3 J, 1064 nm, 8-10 ns) ion source has been built and under development at IMP to provide pulsed high-charge-state heavy ion beams to a radio frequency quadrupole (RFQ) for upgrading the IMP accelerators with a new low-energy beam injector. The laser ion source currently operates in a direct plasma injection scheme to inject the high charge state ions produced from a solid target into the RFQ. The maximum power density on the target was about 8.4 × 10(12) W∕cm(2). The preliminary experimental results will be presented and discussed in this paper.
Ion energy analyser for laser-produced plasma
The theory and design of an ion energy analyser is described which is suitable for the measurement of energy distributions of ions expanding into vacuum from pulsed plasmas of short duration and small size. The analyser is capable of providing the energy distributions of all the ions streaming from the plasma when such a plasma is produced only once. The energy of the ions is obtained from their time of flight to a detector plate and the separation of the mixture of ions into separate beams for each species present is accomplished with an electrostatic field which varies in time and which directs each ion type on to a single collector continuously and independently of the ion energy. The performance of the analyser is demonstrated with a laser-produced carbon plasma giving C+, C2+, C3+ and C4+ ions with energies in the range 500 eV to 2 keV. The influence of self-space-charge is included.