On-line yields obtained with the ISOLDE RILIS

Abstract

The ISOLDE resonance ionization laser ion source (RILIS) allows to ionize efficiently and selectively many metallic elements. In recent yield surveys and online experiments with the ISOLDE RILIS we observed 23 (Submitted to Nuclear Instruments and Methods in Physics Research B) IntroductionThe resonance ionization laser ion source (RILIS) [1] provides an efficient, fast and selective way to ionize many metallic elements. The elements ionized with the ISOLDE RILIS were reviewed recently [2,3,4]. In this article we will discuss on-line results, i.e. release curves and yields measured in recent target tests, nuclear spectroscopy experiments and on-line collections.The measured release curves were fitted with the empiric 4-parameter-formula described in [5,6]. Table 1 shows a summary of the release parameters: t r the rise time, t f the fall time of the fast component, t s the fall time of the slow component and α the relative intensity of the fast component. Parameters which had to be fixed to obtain a stable fit are marked in parentheses.The release parameters were used to determine for each radio-isotope the fraction which is released before it decays. The on-line efficiency of the RILIS cannot be easily monitored as in the case of a plasma ion source where the support gas is injected at a well-defined flowrate. Still a rough estimate can be made by scaling the off-line measured efficiency with the laser power available in the on-line run. Also the ion yield of a longlived isotope with known production cross-section gives an indication of the ionization efficiency. Correcting the ion yields for the released fraction and the ionization efficiency allows to deduce the in-target production yield. In some of the following graphs both values are plotted: the ion yield, showing the presently available radioactive ion beam intensity for the user, and the in-target production yield showing the theoretical limit that could be obtained with an ideal target (no decay losses) of the same thickness and dimensions coupled to an ideal ion source (100 % efficiency). The ratio between both curves shows the overall efficiency of the present target and ion source unit.

Recoil-ion trapping for precision mass measurements

“…All such states studied in this work are given in table 2. Usually, with proton-induced fission, the high-spin isomeric state is more strongly populated than the ground state (see, e.g., [34,35] or [36] for far asymmetric fission). In the case of 62 Mn the spin assignment of the isomers is not known and therefore a careful analysis is needed.…”

Precise lattice location of substitutional and interstitial Mg in AlN

“…24. The only radioactive isotope of Mg suitable for emission channeling studies is the short-lived 27 Mg (t 1/2 =9.45 min).…”

“…All samples were implanted using an energy of 50 keV. After these low-fluence measurements, sample C was implanted with 1×10 15 cm −2 of stable 24 Mg, and the 27 Mg emission channeling measurements were then repeated for annealing temperatures up to 600 • C. For this high-fluence experiment, the Mg peak concentration is estimated to be ∼1.5×10 20 cm −3 , i.e. within the concentration regime reported for the electrical doping of AlN.…”

Decay of 185Tl, 185m+gHg, 189m+gPb and energy location of the 13/2+ isomeric states in 185Hg, 189Pb, 193Po and 197Rn

“…2.1). The Tl atoms are surface ionized in the hot cavity whereas the Pb atoms are selectively photo-ionized in a three-step resonant process using the Resonance Ionization Laser Ion Source, RILIS [36,37], of the ISOLDE facility. To ionize the lead atoms the laser beam wave length was: for the first excitation step, λ = 283.3 nm, for the second excitation step, λ = 600.2 nm and for the ionization step, λ = 511 and 578 nm [11,12].…”