Isotope separator, on-line

Isolde is known throughout the world as the on-line isotope separator at the 600 MeV synchrocyclotron at CERE, Geneva. Work has been going on there since 1967 on many topics includino nuclear physics, solid state, atomic physics, etc. There have been great improvements made over the years but it became clear that the physics output could only be increased if there were to be an expansion of the facility. It was decided to build a second on-line separator to be used alternately with the existing Isolde, thus doubling the potential. The new separator is under construction, called Isolde 3, and is scheduled for first operation next year. 

The Tandem Accelerator Superconducting Cyclotron facility at Chalk River, which is nearing completion of phase 1, will be capable of accelerating all ions to at least 10 HeV/u. Together with the on-line isotope separator it will provide a powerful means of studying exotic nuclei ... 

As of early September, 1985, the facility is being commissioned. Carbon, nitrogen and oxygen beams from the tandem have reached the interim target locations via the bypass line, and an iodine beam has been injected into the cyclotron. First attempts to accelerate iodine in the cyclotron are imminent Some experimental equipment, including the on-line isotope separator [SCH81J, is already set up and undergoing tests with tandem beams. 

Like most other on-line isotope separators (ISOLs), the Chalk River device was previously operated with its ion source essentially in line with the primary accelerator beam so that nuclei produced by reactions in a target would recoil directly into the ISOL ion source. We used a FEBIAD ion source [KIR/6], which was characterized by long cathode lifetime and good efficiency for a wide variety of elements. 

Developing an Accelerated Radioactive Beams Facility Using an On-Line Isotope Separator as an Injector... 

High yields of separated, radioactive ions (up to 1010 atoms/sec yA of incident protons at on-line isotope separators (ISOL), e.g. 

This offers the great advantage of optical resonance with the whole ensemble of atoms and yields an extremely high sensitivity, if the fluorescence is detected with a large solid angle. This advantage, and the fact that on-line isotope separators deliver many radioactive nuclides in the form of ion beams, have played the decisive role for the success of this technique in studies of atomic isotope shifts and hyperfine structures. On the other hand, the high-resolution spectroscopy on ions has been provided with a powerful experimental tool. 

It may be surprising to find the most extensive application of collinear laser fast-beam spectroscopy in a field that a priori has little connection with the special features of this technique. Neither the Doppler shift nor the accessibility of ionic spectra plays a decisive role for the on-line experiments on radioactive isotopes from nuclear reactions. However, most of the problems encountered in the preparation of a sample of free atoms (cf. Part B, Chapter 17 by H.-J. Kluge) are solved by a combination of the fast-beam technique with the well-established concept of on-line isotope separation. The isotope separators (with ISOLDE at CERN as an outstanding example) provide the unstable species in the form of ion beams whose phase-space volume is well matched to the requirements of collinear spectroscopy. 

Nitschke, J.M. OASIS the SuperlDLAC on-line isotope separator. Nucl. Instrum. Methods... 

Behr et al. 1997). In the experiment, ions of and produced at the on-line isotope separators at TRIUMF in Canada were converted to neutral potassium atoms by stopping in a Zn foil. Next, the rethermalized low-energy atoms were captured by one MOT and, finally, transferred by a laser push beam and magnetooptical funnels into a second MOT, free of the large number of nonlocalized atoms. The overall capture... 

Hansen, P. G., Hornshoej, P.. Nielsen, H. L., and others. Decay Characteristics of Short-Lived Radionuclides Studied by On-Line Isotope Separation Techniques. Phys. Lett. 28B. 415 (1969). 23 21307... 

Instrumental developments (e.g., of sector field instruments with multiple ion collection, introduced in 1992, or the insertion of collision and reaction cells in order to reduce disturbing isobaric interferences), the progress in applications for ultratrace analysis, also in combination with on line hyphenated separation techniques (HPLC, CE), especially routine capability as well as decreasing price and user friendly maintenance mean that sales are increasing by 10 % every year. To improve the analytical performance of ICP mass spectrometers for precise isotope ratio measurements (e.g., for geochronology or for the study of fine isotope variation in nature) powerful instrumentation with high mass dispersion and multiple ion collector systems instead of single ion collection are commercially available on the analytical market. 

Hollenbach et al. captured "Tc from standards or soil sample digestates on a TEVA-Resin column for on-line purification and preconcentration prior to ICP-MS determination.49 A wash solution of 0.5 M HN03 was used to remove interferences prior to elution with 8 M HN03 solution. A Re isotope, which behaves similarly to pertechnetate on TEVA-Resin, was used as an internal standard. Recoveries from the column varied from 97 to 99.5%, and columns could be reused over a hundred times. The use of the on-line column separation reduced detection limits by 10-fold and alleviated matrix and isobaric interferences compared to direct sample injection. This pioneering study adapted FIAS-200 and FIAS-400 FI systems to perform sample injection and extraction-chromatographic separations upstream from the ICP-MS. 

Most data on ground state properties of nuclei far from stability have been obtained at the on-line mass separator ISOLDE at CERN, where the isotopes of over 60 elements are available with high yields (up to 10 atoms per sec and mass number) and half lives down to 10 sec. [CER85]. Fig. 1 shows the chart of nuclei and indicates those regions where optical spectroscopy has been performed in long isotopic chains. Similar systematics of mass measurements have been restricted until now to the isotopes of the alkaline elements [AUD84]. 

The magnet of an on-line mass separator will generally assure the selectivity in respect to different isotopes. Hence, the isobaric selectivity of laser ion sources is of primary interest, although isotopic selectivity might also be achieved by RIS using the HFS and IS, which differ from isotope to isotope. 

Nuclear properties (spins, moments, charge radii) revealed by the analysis of hyperfine structure and isotope shift of atomic levels have been obtained in decades of experiments. Since 1975 with the introduction of tunable dye laser, the rebirth of the methods, some already known since 1930, had led to many on line experiments on short lived isotopes not investigated before. I report here a sample of the experiments done by the Orsay, Mainz groups at CERN. Although experiments have been carried out by the Orsay group using the proton beam of the CERN Proton Synchrotron, most of the experiments have been done at Isolde, the on - line mass separator at CERN, whose radioactive beams are essential to the success of these experiments [RAV 84]. 

The rest of the apparatus is the same as when operated at the Proton Synchrotron. First tested on cesium [ HUB 78 ], [ THI 81 ] the apparatus was used to uncover the resonance lines of francium for which no optical transition had ever been observed. The CERN on line mass separator, Isolde, makes available a source of more than 10 atoms/sec of chemically and isotopically pure 213 Fr isotope. Such an amount is more than needed for a laser atomic beam spectroscopy. The first step is obviously to locate the resonance line at low resolution, using a broad band laser excitation. In a second step, once the line is located, a high resolution study is undertaken, [ LIB 80] and [ BEN 84]. The observed signal is displayed (fig 3a) at low resolution and(3 b)at high resolution. 

A He-jet coupled on-line mass separator, used in conjunction with a target chamber placed in the LAMPF main beam, offers an especially attractive approach for the study of nuclei far from stability. Such a facility would provide access to isotopes of a number of elements that cannot be efficiently extracted for study at any other type of on-line separator system, and the use of a long capillary transport line would allow the separator ion source to be located outside the accelerator beam-line shielding, greatly reducing the installation cost. The He-jet technique requires thin targets in order for the reaction products to escape, and to produce a sufficient yield of radioisotopes far from stability for detailed nuclear studies, a beam intensity comparable to that available at LAMPF is needed. 

Off-line dicarbamate solvent extraction and ICP-MS analysis [317] provided part-per-trillion detection limits Cd (0.2 ppt), Co (0.3 ppt), Cu (3 ppt), Fe (21 ppt), Ni (2 ppt), Pb (0.5 ppt), and Zn (2 ppt). Off-line matrix removal and preconcentration using cellulose-immobilized ethylenediaminetetraacetic acid (EDTA) have also been reported [318]. Transition metals and rare earth elements were preconcentrated and separated from the matrix using on-line ion chromatography with a NTA chelating resin [319]. Isotope-dilution-based concentration measurement has also been used after matrix separation with a Chelex ion-exchange resin [320]. The pH, flow rate, resin volume, elution volume, and time required for isotope equilibration were optimized. A controlled-pore glass immobilized iminodiacetate based automated on-line matrix separation system has also been described [321]. Recoveries for most metals were between 62% and 113%. 

Ohtsuka et al. used a combination of on-line column separation and ICP-IDMS for the rapid determination of plutonium in environmental samples [66]. After leaching of plutonium from soil or sediment samples with 8 mol 1 HNO3, followed by chromatographic separation, the plutonium isotopes Pu (T54 = 2.4 x lO years) and Pu (T = 6550 years) were determined using a quadmpole-based ICP-MS instrument and a Pu (Tj = 3.8 x 10 years) spike, providing absolute LODs of 9.2 and 4.3 fg, respectively. The accuracy of the results was demonstrated by the good agreement between the sums of the Pu and contents as... 

In a seminal study, Gunther-Leopold et al. [10] used an on-line chromatographic separation system combined with MC-ICP-MS for determination of Pu isotope... 

An impressive illustration of the sensitivity of this technique is the measurement of nuclear charge radii and nuclear moments of stable and radioactive instable isotopes through the resolution of optical hfs splittings and isotope shifts performed by several groups [10.7-11]. Even spurious concentrations of short-lived radioactive isotopes could be measured in combination with an on-line mass separator. 

S.L. Kaufman, H. Lochmann, G. Moruzzi, R, Neugart, E.-W. Otten, J. Bonn, L. von Reisky, K.P.C. Spath, J. Steinacher, D. Wes-kott, Collinear Laser S ectroscopy of Neutron-Rich Cs Isotopes at an On-Line Mass Separator, Phys. Lett. 79B 209 (1978) C. 

---