Fast atom-trap analysis of 39Ar with isotope pre-enrichment.

We demonstrate fast analysis of 39Ar/Ar at the 10-16 level using a mass spectrometer for isotope pre-enrichment and an atom trap for counting. An argon gas sample first passes through a dipole mass separator that reduces the dominant isotope 40Ar by two orders of magnitude while preserving both the rare tracer isotope 39Ar and a minor stable isotope 38Ar for control purposes. Measurements of both natural and enriched samples with atom trap trace analysis demonstrate that the 39Ar/38Ar ratios change less than 10%, while the overall count rates of 39Ar are increased by one order of magnitude. By overcoming the analysis-speed bottleneck, this advance will benefit large-scale applications of 39Ar dating in the earth sciences, particularly for mapping ocean circulation.

An all permanent magnet electron cyclotron resonance ion source for heavy ion therapy.

A high charge state all permanent Electron Cyclotron Resonance ion source, Lanzhou All Permanent ECR ion source no. 3-LAPECR3, has been successfully built at IMP in 2012, which will serve as the ion injector of the Heavy Ion Medical Machine (HIMM) project. As a commercial device, LAPECR3 features a compact structure, small size, and low cost. According to HIMM scenario more than 100 eµA of C(5+) ion beam should be extracted from the ion source, and the beam emittance better than 75 π*mm*mrad. In recent commissioning, about 120 eµA of C(5+) ion beam was got when work gas was CH4 while about 262 eµA of C(5+) ion beam was obtained when work gas was C2H2 gas. The design and construction of the ion source and its low-energy transportation beam line, and the preliminary commissioning results will be presented in detail in this paper.

The study of helicon plasma source.

Helicon plasma source is known as efficient generator of uniform and high density plasma. A helicon plasma source was developed for investigation of plasma neutralization and plasma lens in the Institute of Modern Physics in China. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high argon plasma density up to 3.9x10(13) cm(-3) have been achieved with the Nagoya type III antenna at the conditions of the magnetic intensity of 200 G, working gas pressure of 2.8x10(-3) Pa, and rf power of 1200 W with a frequency of 27.12 MHz. In the experiment, the important phenomena have been found: for a given magnetic induction intensity, the plasma density became greater with the increase in rf power and tended to saturation, and the helicon mode appeared at the rf power between 200 and 400 W.