High Resolution Mass Separator Research Articles

Neutron capture studies on unstableCs135for nucleosynthesis and transmutation

The neutron capture cross section of the unstable isotope $^{135}\mathrm{Cs}$ was measured relative to that of gold by means of the activation method. The sample was produced by ion implantation in a high resolution mass separator and irradiated with quasimonoenergetic neutrons at $30\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $500\phantom{\rule{0.3em}{0ex}}\text{keV}$, using the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}$ reaction. An additional irradiation with thermal neutrons has been carried out for defining the sample mass and for measuring the half-life of $^{136}\mathrm{Cs}$. The neutron capture cross sections were determined as $164\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.3em}{0ex}}\text{mb}$ and $34.8\ifmmode\pm\else\textpm\fi{}3.0\phantom{\rule{0.3em}{0ex}}\text{mb}$ at $30\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $500\phantom{\rule{0.3em}{0ex}}\text{keV}$, respectively, and were used to normalize the theoretically derived cross section shape. Based on these data, refined statistical model calculations were performed to obtain the $(n,\ensuremath{\gamma})$ cross sections of the short-lived isotopes $^{134}\mathrm{Cs}$ and $^{136}\mathrm{Cs}$ as well. Updated Maxwellian-averaged capture cross sections of all unstable Cs isotopes were calculated for a range of thermal energies characteristic of helium burning scenarios for an improved $s$-process analysis of the Xe-Cs-Ba region.

Magnetic moment of 17Ne using β-NMR and tilted foil polarization

We report on the measurement of the magnetic moment of the ground state of 17Ne. Radioactive 17Ne nuclei were delivered from the high resolution mass separator at ISOLDE onto a high voltage platform at −200 kV and were polarized using the tilted foil polarization method. The polarized nuclei were implanted into a Pt stopper situated in a liquid-helium cooled β-NMR apparatus and the asymmetry destruction of the ensuing β rays was monitored as a function of the rf frequency applied to the polarized nuclei. The measured value of μ = 0.74 ± 0.03 affirms the nature of the ground state of 17Ne and is compared to shell model calculations.

TRIUMF-ISAC target station and mass separator commissioning

The ISAC facility includes: a new building with 5000 m 2 of floor space, a beam line with adequate shielding for up to 100 μA protons at 500 MeV from the TRIUMF H − cyclotron, two target stations, remote handling facilities for target services, a high resolution mass separator and a linear accelerator. The first radioactive ion beams were produced in the fall of 1998 and now the experimental program has started. A novel approach for the target station permits the operation of the ISOL target up to 100 μA. Furthermore, several diagnostics tools were developed for the mass separator helping considerably the RIB tuning.

The stellar (n,γ) cross section of the unstable 135Cs

The (n,γ) cross sections of the unstable isotope 135Cs has been measured relative to that of gold by means of the activation method. The sample was produced by ion implantation in a high resolution mass separator and irradiated in a quasi-stellar neutron spectrum for kT = 25 keV using the 7Li(p,n) 7Be reaction near threshold. The ∼ 8 % uncertainty of the resulting stellar cross sections is dominated by the thermal (n,γ) cross section used for sample definition.

The ISOL exotic beam facility at LNS: the EXCYT project

The aim of the EXCYT project (EXotics with CYclotron and Tandem) is the development of a facility for producing and accelerating exotic beams from 0.2 up to 8 MeV/amu. EXCYT is based on the “two accelerators” method. A K = 800 Superconducting Cyclotron (CS), axially injected by the ECR ion source SERSE, will deliver the primary beam. Such a beam will produce the required nuclear species in a modified ISOLDE type target-source complex. When required, a 15 MV Tandem Van der Graaff will accelerate the secondary beams. Both accelerators are existing and operational at Laboratorio Nazionale del Sud (LNS). Concerning the status of the project, progress has been made in most of the key issues of the project, like the construction of SERSE, cyclotron upgrading, modification of the existing building, high resolution mass separator, and diagnostic equipment for low energy, low intensity beams.

High-resolution mass separator and 60 m beam transport line for the radioactive nuclear beam facility at INS

A high-resolution on-line isotope separator (ISOL) followed by a long beam transport line is under testing at INS, as a pilot radioactive beam facility for the E-arena of the Japanese Hadron Project. The ISOL has a unique feature in its high-voltage potential configuration; it has two separation stages and both are electrically insulated from the ground. This feature is effective to eliminate impurities as well as to perform high-resolution mass separation while keeping the injection beam velocity to the post accelerator constant. The design concept and present status of performance tests are reported.

Concept of a high-resolution online mass separator for the Munich fission fragment accelerator

A fission fragment accelerator combined with the Munich high-flux reactor FRM-II is under design for the delivery of intense beams of mass separated very neutron-rich fission fragments with energies at the Coulomb barrier. They can be used to produce very heavy neutron-rich nuclei in fusion reactions. The large neutron excess will result in much longer lifetimes of the produced heavy elements, compared to neutron-deficient ones produced in reactions with stable nuclear beams. Thus fast α-chains can no longer be used to identify the heavy reaction products. A new separator will be used consisting of a velocity filter, an ion guide system (IGISOL) and a Penning trap. The velocity filter separates the primary beam and results in a strong background suppression. The IGISOL system improves the emittance and enriches the 1 + ions in the beam, which will then be efficiently transferred into a Penning trap. In the Penning trap the ions are bunched, stopped and mass separated with high resolving power ( R ≈ 10 5).

Ion-optical design of the high-resolution mass separator for the Japanese Hadron Project

An ion-optical design of the JHP-ISOL is presented. This separator consists of a beam guidance system, a main magnetic separator stage and an electrostatic energy focusing stage. This separator is to be coupled with a heavy-ion linac for post-acceleration of mass separated ions up to 6.5 MeV/u. The design goal of the separator is to realize a mass resolving power of R M = 20000 (basal) at a transmission approaching 100% with the initial phase space of ± 0.2 mm × ± 20 mrad.