A Study of KF3- Attenuation in an RFQ Gas Cell for 41Ca AMS

Abstract

Guided by simulations using SIMION 8.1, a series of modifications were made to an experimental version of an Isobar Separator for Anions (ISA). The resulting improved version of the ISA provides a means of re-energizing the ions after they are cooled by gas collisions as they pass through the gas-filled radiofrequency quadrupoles (RFQ), and also provides higher transmission efficiencies. Reinvestigation of the separation of CaF 3  and KF 3  with this refined apparatus resulted in a better balance between isobar suppression and analyte transmission. KF 3  was attenuated at eV energies by 4 orders of magnitude while 40% transmission of CaF 3  was retained, for a 20keV CaF 3  beam of 2mm and ±12mr. These results advance the possibility of an efficient small ISA-AMS system for both cosmogenic and medical applications of 41 Ca.

On‐line HfF5−/WF5− separation in an O2‐filled radiofrequency quadrupole gas cell

“…Other system details and experimental procedures were identical to those described earlier. [13][14][15][16] RESULTS AND DISCUSSION Figure 2 shows the Hf and W beams transmitted through the test isobar separator containing varying concentrations of NO 2 gas. NO 2 is both an electronegative gas and a radical.…”

“…Detailed descriptions of the experimental apparatus and the ion energy evaluation procedures by SIMION simulations are given elsewhere. [16] A simulation with the actual experimental conditions used for the HfF 5 À /WF 5 À studies is shown in Fig. 1.…”

“…It is the first such integrated ISAMS setup, and it has been successfully used to demonstrate large separations of a number of isobar pairs. [13][14][15][16] Various configurations of the original isobar separator have also been investigated to study the ion transport efficiency and to provide some ion energy control, which led to a temporary test configuration of the isobar separator [16] used in this work. To minimize losses of the fragile analyte anions by electron detachment or collisional fragmentation, it is an objective to prepare the anions captured by the RFQ ion guide with a small average energy and also a small energy spread, prior to significant gas collisions.…”

“…1 were measured one at a time as a function of gas pressure inside the gas cell. [16] Each data point was obtained using the final detectors (Faraday cup or ionization chamber Beam: m/z 275, 2 mm diameter, 12 mRad, 6999.25 eV Lab Ground Figure 1. Simulation of the transport of the beam specified at the upper left and the prepared ion energy probability distribution prior to the onset of gas collisions in the test isobar separator used.…”

“…In recent years, this experimental device with various configurations has been shown to have great power for separating isobars for AMS measurement of 36 Cl, [12][13][14] 90 Sr and 135 Cs, [15] and recently 41 Ca. [16] In this report, following a brief description of the particular setup used for these initial HfF 5 À /WF 5 À studies, the preliminary results obtained using two different gases, NO 2 and O 2 , will be presented, as these results have relevance to the further development of such apparatus for the detection of 'live' 182 Hf in nature.…”