T. Kessler

Development of a laser ion source at IGISOL

FURIOS, the Fast Universal laser IOn Source, is under development at the IGISOL (Ion Guide Isotope Separator On-Line) mass separator facility in Jyvaskyla, Finland. This new laser ion source will combine a state-of-the-art solid state laser system together with a dye laser system, for the selective and efficient production of exotic radioactive species without compromising the universality and fast release inherent in the IGISOL system. The motivation for, and development of, this ion source is discussed in relation to the programme of research ongoing at this mass separator facility.

Off-line studies of the laser ionization of yttrium at the IGISOL facility

Abstract A laser ion source is under development at the IGISOL facility, Jyvaskyla, in order to address deficiencies in the ion guide technique. The key elements of interest are those of a refractory nature, whose isotopes and isomers are widely studied using both laser spectroscopic and high precision mass measurement techniques. Yttrium has been the first element of choice for the new laser ion source. In this work, we present a new coupled dye–Ti:Sapphire laser scheme and give a detailed discussion of the results obtained from laser ionization of yttrium atoms produced in an ion guide via resistive heating of a filament. The importance of not only gas purity, but indeed the baseline vacuum pressure in the environment outside the ion guide is discussed in light of the fast gas phase chemistry seen in the yttrium system. A single laser shot model is introduced and is compared to the experimental data in order to extract the level of impurities within the gas cell.

Mass measurements in the vicinity of the doubly magic waiting point {sup 56}Ni

Masses of {sup 56,57}Fe, {sup 53}Co{sup m}, {sup 53,56}Co, {sup 55,56,57}Ni, {sup 57,58}Cu, and {sup 59,60}Zn have been determined with the JYFLTRAP Penning trap mass spectrometer at the Ion-Guide Isotope Separator On-Line facility with a precision of {delta}m/m{<=}3x10{sup -8}. The Q{sub EC} values for {sup 53}Co, {sup 55}Ni, {sup 56}Ni, {sup 57}Cu, {sup 58}Cu, and {sup 59}Zn have been measured directly with a typical precision of better than 0.7 keV and Coulomb displacement energies have been determined. The Q values for proton captures on {sup 55}Co, {sup 56}Ni, {sup 58}Cu, and {sup 59}Cu have been measured directly. The precision of the proton-capture Q value for {sup 56}Ni(p,{gamma}){sup 57}Cu, Q{sub (p,{gamma})}=689.69(51) keV, crucial for astrophysical rp-process calculations, has been improved by a factor of 37. The excitation energy of the proton-emitting spin-gap isomer {sup 53}Co{sup m} has been measured precisely, E{sub x}=3 174.3(10) keV, and a Coulomb energy difference of 133.9(10) keV for the 19/2{sup -} state has been obtained. Except for {sup 53}Co, the mass values have been adjusted within a network of 17 frequency ratio measurements between 13 nuclides, which allowed also a determination of the reference masses {sup 55}Co, {sup 58}Ni, and {sup 59}Cu.

Electron-capture branch of {sup 100}Tc and tests of nuclear wave functions for double-{beta} decays.

We present a measurement of the electron-capture branch of {sup 100}Tc. Our value, B(EC) = (2.6 {+-} 0.4) x 10{sup -5}, implies that the {sup 100}Mo neutrino absorption cross section to the ground state of {sup 100}Tc is roughly 50% larger than previously thought. Disagreement between the experimental value and QRPA calculations relevant to double-{beta} decay matrix elements persists. We find agreement with previous measurements of the 539.5- and 590.8-keV {gamma}-ray intensities.

Nuclear spin determination of 100mY by collinear laser spectroscopy of optically pumped ions

The nuclear spin of the τ1/2 = 0.94 s isomer in 100Y has been determined by collinear laser spectroscopy of optically pumped yttrium fission fragments at the IGISOL facility, JYFL. The isotopes 96, 98, 99, 100Y were produced by the proton-induced fission of natural uranium, and studied on the 4d5s 3D2 (1045 cm−1) → 4d5p 3P1 (32 124 cm−1) transition at 321.67 nm. Enhancement of the population of the metastable 3D2 level was achieved by optically pumping the ground state population via the 5s2 1S0 → 4d5p 1P1 transition at 363.31 nm while the ions were stored in a linear Paul trap. These data, when combined with previous spectroscopic results, give sufficient information for the nuclear spin of 100mY to be determined unambiguously as I = 4. This spin assignment reveals that 100mY has an unexpectedly large dynamic contribution to its quadrupole deformation.

A hot cavity laser ion source at IGISOL

A development program is underway at the IGISOL (Ion Guide Isotope Separator On-Line) facility, University of Jyväskylä, to efficiently and selectively produce low-energy radioactive ion beams of silver isotopes and isomers, with a particular interest in N = Z94Ag . A hot cavity ion source has been installed, based on the FEBIAD (Forced Electron Beam Induced Arc Discharge) technique, combined with a titanium:sapphire laser system for selective laser ionization. The silver recoils produced via the heavy-ion fusion-evaporation reaction, 40Ca(58Ni, p3n)94Ag , are stopped in a graphite catcher, diffused, extracted and subsequently ionized using a three-step laser ionization scheme. The performance of the different components of the hot cavity laser ion source is discussed and initial results using stable 107, 109Ag are presented.

Ultra Trace Determination Scheme for 26 Al by High-Resolution Resonance Ionization Mass Spectrometry using a Pulsed Ti:Sapphire Laser

We propose an ultra trace analysis approach for 26Al by high-resolution Resonance Ionization Mass Spectrometry (RIMS) using a pulsed narrow band-width Ti:Sapphire laser. For ensuring efficient ionization and high isotopic selectivity in RIMS of Al, we developed an injection seeded pulsed Ti:Sapphire laser with high repetition rate operation at up to 10 kHz. The laser produced an output power of 2 W and a spectral band-width of ~20 MHz with a repetition rate of 7 kHz. A first demonstration of its performance was done by detecting stable 27Al using RIMS.

TAS measurements for reactor physics and nuclear structure

In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.

Mass and Q{sub EC} value of {sup 26}Si

The Q{sub EC} value of the superallowed {beta} emitter {sup 26}Si has been measured with the JYFLTRAP Penning trap facility to be 4840.85(10) keV which is ten times more precise than any previous measurement. This leaves only the branching ratio to be improved before the Ft value of {sup 26}Si can be used to test the conserved vector current hypothesis. As a consequence, the {sup 25}Al(p,{gamma}){sup 26}Si reaction Q-value (Q{sub p{gamma}}) was improved to be 5513.7(5) keV, limited now by the mass excess of {sup 25}Al. The new Q{sub p{gamma}} value changes the stellar production rate of {sup 26}Si in nova ignition temperatures by about 10%.

Applications of the total absorption technique to improve reactor decay heat calculations: study of the beta decay of 102,104,105Tc

The decay heat of the fission products plays an important role in predicting the heat‐up of nuclear fuel after reactor shutdown. This form of energy release is calculated as the sum of the energy‐weighted activities of all fission products P(t) = ΣEiλiNi(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy at t∼1000 s cooling time for some fuels. A possible explanation for this disagreement can been found in the work of Yoshida et al. [1], who demonstrated that an incomplete knowledge of the β‐decay of some Tc isotopes could be the source of the systematic discrepancy. Motivated by [1], we have recently measured the β‐decay process of some Tc isotopes using a total absorption spectrometer at the IGISOL facility in Jyvaskyla. The results of the measurements are discu...