J. Ärje

The first results with the new JYFL 14 GHz ECR ion source

Abstract A new 14 GHz ECR ion source has been built for the Accelerator Laboratory in the Department of Physics (JYFL), University of Jyvaskyla. This source belongs to the family of the LBNL AECR-U-based ECR ion sources. The operation during the first four months has shown that the new ion source performs well and is able to produce intensive highly charged ion beams. For example, 145 μA of O7+ ion beam was recorded. The production of iron and boron ion beams was tested using the MIVOC method. The 56Fe11+ ion beam current reached a value of 115 μA. The intensities of 11B3+ and 11B5+ ion beams were 235 and 52 μA, respectively. This iron beam intensity is the second highest and the boron beam intensities are the highest ever produced by an ECR ion source. In all the tests an extraction voltage of 10 kV was applied.

The ion guide isotope separator on-line, IGISOL

Abstract A new ISOL method, the IGISOL (Ion Guide Isotope Separator On-Line), permits thermalized primary recoil ions produced in nuclear reactions to be run directly through a mass separator without a conventional ion source. It allows a fast (≳ 100 μs) separation of various radioactive isotopes of both volatile and nonvolatile elements. The overall separation efficiencies measured for heavy nuclides produced in light ion induced reactions are up to 10%. The shortest-lived activity identified in an on-line separation is the 182 μs isomeric state of 207Bi.

Ion guide method for on-line isotope separation

Abstract A new ISOL technique, the ion guide method for isotope separation, has been developed. The method is based on thermalization of primary recoil ions from nuclear reactions in helium and on their transfer by helium flow through a differential pumping system into the accelerating stage of an isotope separator. With this approach, separation times in the submillisecond region are achievable for all elements. The ion guide has no ionizer but instead exploits charge exchange mechanisms related to nuclear reactions and recoil thermalization processes. Operation takes place at room temperature and the simple construction involves no components that can wear out. These properties ensure smooth and stable operating conditions. The overall separation efficiencies measured for heavy nuclides produced by light-ion reactions are up to 10%. The shortest-lived activity identified in an on-line separation is the 182-μs isomeric state of 207Bi. The production rate of the mass separated 440-μs isomeric state of 43Sc is ≈ 2 × 103 ions/μC.

Beta decay of Tz = −12 nuclides 51Fe and 55Ni: A new approach to on-line isotope separation

Abstract The mirror beta decays of 51 Fe (J π , T = 5 2 − , 1 2 ) and 55 Ni (J π , T = 7 2 − , 1 2 ) have been studied with the ion guide isotope separator on-line-system. The measured half-lives of 310 ± 5 ms for 51 Fe and 208 ± 5 ms for 55 Ni differ significantly from previouslreported values. In the case of 51 Fe, an allowed decay branch with a (5.0 ± 1.3)% intensity to the 7 2 − state at 237 keV in 51 Mn was observed. The deduced Gamow-Teller matrix elements are compared with values calculated using the empirical ( f 7 2 ) n shell model.

Separation of fission products by the ion guide fed isotope separator, IGISOL

Abstract The performance of the ion guide method in the on-line mass separation of fission products has been investigated. Activity was produced by bombarding nat. U targets with a beam of 20 MeV protons. All the mass chains from A = 95 through A = 120 have been scanned using conventional methods of nuclear spectroscopy. No chemical selectivity in the separation was observed; isotopes of highly nonvolatile elements from yttrium to palladium were produced with efficiencies equal to those for the more volatile ones. The boundary of known neutron-rich nuclides was reached throughout the mass region from A = 106 to A = 118. During the course of this preliminary study the new isotope 116 Rh was observed and its half-life measured to be (1.0±0.2)s. Several other unknown activities were also detected. A fraction of the order of 15% of Y, Zr and Nb activities were present as oxide ions.

Plasma breakdown diagnostics with the biased disc of electron cyclotron resonance ion source

The electron cyclotron resonance ion sources at the JYFL (University of Jyvaskyla, Department of Physics) accelerator laboratory have been operated in pulsed mode to study the time-resolved current signal from the biased discs of the ion sources. The purpose of the experiments is to gain an understanding of the ion source parameters affecting the time required for the transition from neutral gas to plasma. It was observed that the plasma breakdown time depends strongly on the neutral gas density, gas species and density of seed electrons. In particular, it was observed that a low power microwave signal at secondary frequency makes the breakdown time virtually independent of the neutral gas density. The results can be utilized for operation of ECR ion sources in the so-called preglow mode. A simple qualitative model, which is in good agreement with the experiments, has been developed to interpret the results.

The ion-guide isotope separator on-line at the Tohoku University Cyclotron

Abstract The status of the ion-guide isotope separator on-line at the Tohoku University Cyclotron is reported. The optimum ion-guide parameters were determined from test experiments using atomic and molecular ions ionized with an electric discharge inside the target chamber as well as using 64 Ga(T 1 2 = 2.6 m ) ions produced by the 64Zn(p, n) reaction. Using the present system together with a ΔE−E plastic counter telescope and a germanium detector we identified 16 short-lived nuclei including the first mass-separated nuclei 57Cu and 45V. The efficiency of mass separation for 64Ga was ϵ ∼ 1%, where ϵ is defined as the number of atoms collected at the end of the separator divided by that recoiling from the target. Application of IGISOL to nuclear physics is being performed for nuclei in the f 7 2 -P 3 2 shell regions and medium-mass neutron-rich nuclei produced by the proton-induced fission reaction with a uranium target.

Production of titanium ion beams in an ECR ion source

Abstract Intensive highly charged Ti ion beams were successfully produced in the 14 GHz ECR ion source at the Accelerator Laboratory, University of Jyvaskyla (JYFL). The Ti beams were produced using the MIVOC technique, i.e. by allowing the vapor of an organic compound containing titanium to diffuse into the ion source at room temperature. After optimizing the source parameters the intensity of the 48 Ti 11+ ion beam reached a value of 45 μA.

Production of highly charged metal ion beams from organic metal compounds at RIKEN 18 GHz ECRIS

Abstract Intense beams of highly charged metal ions (e.g., 80 μA for Fe13+) are successfully extracted from the 18 GHz ECR Ion Source at RIKEN by feeding vapors of organic metal compounds at room temperature into the ECR plasma chamber: by MIVOC method. The beam intensity of particular metal ion is strongly dependent on the microwave power and served compounds.

A study of a helium-jet ion guide for an on-line isotope separator

Abstract A new method based on helium-jet techniques permits primary recoil ions, produced in radioactive decay or in nuclear reactions to be run directly through a mass separator. Results obtained with a 227 Ac source promise qualities complementary with those obtained with conventional ion sources and indicate an overall efficiency of the order of 10%. Preliminary results with 20 Na recoils from the 20 Ne(p,n)-reaction indicate that most of the ionic species transported out from the target chamber are negatively charged.