On a cryogenic noble gas ion catcher

In-situ purification of the gas used as stopping medium in a noble gas ion catcher by operating the device at low temperatures of 60 to 150 K was investigated. Alpha-decay recoil ions from a 223Ra source served as energetic probes. The combined ion survival and transport efficiencies for 219Rn ions saturated below about 90 K, reaching 28.7(17) % in helium, 22.1(13) % in neon, and 17.0(10) % in argon. These values may well reflect the charge exchange and stripping cross sections during the slowing down of the ions, and thus represent a fundamental upper limit for the efficiency of noble gas ion catcher devices. We suggest the cryogenic noble gas ion catcher as a technically simpler alternative to the ultra-high purity noble gas ion catcher operating at room temperature.Comment: Submitted to Nucl. Instrum. Meth. Phys. Res.

Production of Zero-Energy Radioactive Nuclear Beams through Extraction from the Liquid-Vapour Interface of Superfluid Helium

A new approach has been investigated to create an ultra-cold radioactive beam from high-energy ions. A 223Ra alpha-decay recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling 219Rn ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface has been possible thanks to the high sensitivity of radioactive ion detection. An efficiency of 36 % has been obtained for the ion extraction out of liquid helium.</p

Precision measurement of the half-life and the decay branches of 62Ga

In an experiment performed at the Accelerator Laboratory of the University of Jyvaskyla, the beta-decay half-life of 62Ga has been studied with high precision using the IGISOL technique. A half-life of T1/2 = 116.09(17)ms was measured. Using beta-gamma coincidences, the gamma intensity of the 954keV transition and an upper limit of the beta-decay feeding of the 0+_2 state have been extracted. The present experimental results are compared to previous measurements and their impact on our understanding of the weak interaction is discussed.Comment: 7 pages, 7 figures, submitted to EPJ

Aspects of Cooling at the TRIμ\muP Facility

The Tri$\mu$P facility at KVI is dedicated to provide short lived radioactive isotopes at low kinetic energies to users. It comprised different cooling schemes for a variety of energy ranges, from GeV down to the neV scale. The isotopes are produced using beam of the AGOR cyclotron at KVI. They are separated from the primary beam by a magnetic separator. A crucial part of such a facility is the ability to stop and extract isotopes into a low energy beamline which guides them to the experiment. In particular we are investigating stopping in matter and buffer gases. After the extraction the isotopes can be stored in neutral atoms or ion traps for experiments. Our research includes precision studies of nuclear $\beta$-decay through $\beta$-$\nu$ momentum correlations as well as searches for permanent electric dipole moments in heavy atomic systems like radium. Such experiments offer a large potential for discovering new physics.Comment: COOL05 Workshop, Galena, Il, USA, 18-23. Sept. 2005, 5 pages, 3 figure

Study of adaptation mechanism of deep sea bacterium Shewanella piezotolerans WP3 to extreme environment--the role and regulation of fatty acid system and deep sea phage SW1 in various environments

深海是一个特殊的生态环境,这里有着永久的低温、高压和黑暗。生活在这些环境下的极端微生物必然有特殊的生理代谢途径来适应这种极端环境。对深海微生物的研究不仅有助于了解生命的起源,而且可以了解各种极端微生物的生活特性,有助于对深海微生物资源的开发利用。极端条件下的生命和生态现象研究将可能揭示生命适应逆境、演化自身的能力，为人类健康开辟新的途径。 本文所研究的深海细菌分离自西太平洋1914米的深海沉积物中。菌种鉴定为ShewanellapiezotoleransWP3,它既是耐压菌，又是低温菌，现在已经完成其全基因组序列的测定，是研究极端微生物适应极端环境的理想材料。本文用WP3作为实验材料，通过模...Deep-sea is a special ecosystem for its permanent coldness, high pressure and darkness. The study towards the deep-sea microbes will be helpful to the understanding of the origin of life, the character of biodiversity and to the exploitation of microbial resources in deep sea. The metabolic and ecological study of life on extreme conditions will give some insights on evolution and adaptation mech...学位：理学硕士院系专业：生命科学学院生物学系_生物化学与分子生物学学号：2012005130212

Production of ²³⁵Np, ²³⁶Pu and ²³⁷Pu via nuclear reactions on ^235,236,238U and ²³⁷Np targets

A summary of methods for cyclotron production of 235Np (396.1d), 236Pu (2.858y) and 237Pu (45.2d) via nuclear reactions with protons and 3He-ions on 235,236,238U and 237Np targets in wide energy ranges is given. Methods for the chemical separation and purification of these nuclides from the irradiated uranium and neptunium targets are described. Cross sections, yields and radionuclidic purities of 235Np, 236Pu and 237Pu are presented and compared with literature data on the nuclear reactions leading to these radionuclides. The nuclear reactions with the so far highest known yields of 235Np, 236Pu and 237Pu are determined: 236U(p, 2n)235Np, 237Np(p, 2n + pnβ-)236Pu and 237Np(p, n) 237Pu, respectively. The highest radionuclidic purity of 235Np, 236Pu and 237Pu tracers can be reached with the 236U(p, 2n)235Np, 236U(p, nβ -)236Pu and 237Np(3He, t) 237Pu reactions, respectively. In addition new cross sections and yield data of the 236U(3He, p3n)235Np reaction in the energy range 42.4-60 MeV are given.</p

Decay of [Formula Presented] to [Formula Presented]

The decay of on-line mass-separated [Formula Presented] has been studied by [Formula Presented] spectroscopy. A definite odd parity and a probable [Formula Presented] are deduced for the high-spin [Formula Presented]-decaying level. The 1116 keV and 1392 keV levels in the [Formula Presented] daughter nucleus are candidates for the bottom of the [Formula Presented] band. There is no support for a previously reported very-low-lying [Formula Presented] level at 871 keV. A [Formula Presented] band built on the new level at 1639 keV is proposed. The lowest-lying two-quasiparticle levels in [Formula Presented] are calculated in the framework of the quantum Monte Carlo pairing model using deformed shell model states. The lowest configurations are associated with an oblate minimum of the potential energy.</p

Production of Radioactive Nuclides in Inverse Reaction Kinematics

Efficient production of short-lived radioactive isotopes in inverse reaction kinematics is an important technique for various applications. It is particularly interesting when the isotope of interest is only a few nucleons away from a stable isotope. In this article production via charge exchange and stripping reactions in combination with a magnetic separator is explored. The relation between the separator transmission efficiency, the production yield, and the choice of beam energy is discussed. The results of some exploratory experiments will be presented.Comment: 10 pages, 4 figures, to be submitted to Nucl. Instr. and Met

ICF burn-history measurments using 17-MeV fusion gamma rays

Fusion reaction rate for inertial-confinement fusion (ICF) experiments at the Nova Laser Facility is measured with 30-ps resolution using a high-speed neutron detector. We are investigating a measurement technique based on the 16.7-MeV gamma rays that are released in deuterium-tritium fusion. Our concept is to convert gamma-ray energy into a fast burst of Cerenkov light that can be recorded with a high-speed optical detector. We have detected fusion gamma rays in preliminary experiments conducted at Nova where we used a tungsten/aerogel converter to generate Cerenkov light and an optical streak camera to record the signal

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

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 joule 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.Comment: 18 pages submitted to NIM