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.
Laser Ablation Plasma with Solenoid Field Confinement
A Laser Ion Source (LIS) can produce high charge state and high intensity ion beams (~emA), especially refractory metallic ion beams, which makes it a promising candidate as an ion source for heavy ion cancer therapy facilities and future accelerator complexes, where pulsed high intensity and high charged heavy ion beams are required. However, it is difficult for LIS to obtain a long pulse width while ensuring high current intensity, thus limiting the application of LIS. To solve the conflict, magnetic fields are proposed to confine the expansion of the laser produced plasma. With a solenoid along the normal direction to the target surface, the lateral adiabatic expansion of the laser ablation plasma is suppressed which extends the pulse width of the ion beam effectively.
Chemical, biological, and immunological characterization of mono- and diiodothyrotropin releasing factor.
Abstract Iodination of thyrotropin releasing factor (TRF) with chloramine-T and NaI at pH 7.5 produces both mono- and diiodo-TRF as well as unreacted TRF and I − . The four compounds can be separated by ion-exchange chromatography on SP-Sephadex C-25, using a stepwise gradient of 0.01 m MH 4 OAc at pH 3.5, 5.2 and 7.2. The monoiodo-TRF was characterized by nuclear magnetic resonance, mass spectra, and elemental analysis as [Im-5-iodo-His 2 ]-TRF while the diiodo-TRF was similarly characterized as [Im-2,5-diiodo-His 2 ]-TRF. Both iodination products showed no thyrotropin releasing activity at doses up to 1 μg in the in vivo mouse bioassay. The specific binding of mono- and diiodo-TRF was measured against three different TRF antisera. In the absence of TRF, antisera A and C bound more diiodo-TRF than monoiodo-TRF while antiserum B seemed to bind both tracers equally. In all cases steeper curves were produced when diiodo-TRF was displaced by synthetic TRF.