Soft X-ray laser spectroscopy on trapped highly charged ions at FLASH

Institut für Experimentalphysik, University of Hamburg, Hamburg, Hamburg, Germany
Physical Review Letters (Impact Factor: 7.51). 06/2007; 98(18):183001. DOI: 10.1103/PhysRevLett.98.183001
Source: PubMed

ABSTRACT In a proof-of-principle experiment, we demonstrate high-resolution resonant laser excitation in the soft x-ray region at 48.6 eV of the 2 (2)S(1/2) to 2 (2)P(1/2) transition of Li-like Fe23+ ions trapped in an electron beam ion trap by using ultrabrilliant light from Free Electron Laser in Hamburg (FLASH). High precision spectroscopic studies of highly charged ions at this and upcoming x-ray lasers with an expected accuracy gain up to a factor of a thousand, become possible with our technique, thus potentially yielding fundamental insights, e.g., into basic aspects of QED.

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    • "The experiments, which benefit from high integrated flux are, e.g., spectroscopy of highly charged ions and cold molecular ions, produced with low concentration in the ion traps [1] [2]; spectroscopy of low Z elements [3], and studies of low populated mass selected clusters [6]. High integrated photon flux is greatly appreciated by the photon-induced materials processing applications. "
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    ABSTRACT: Keywords: free electron laser, linear accelerator, vacuum ultraviolet (VUV) source. The fabulous properties of the coherent radiation generated with the free electron lasers (FEL) gained broader perspective on the experimental capabilities in physics, chemistry, biology and medicine. They raise from the nanometer-ranged wavelength, femtosecond-ranged pulse duration and brightness in the range of 10 29 photons/(s·mrad 2 ·mm 2 ·0.1% bandwidth) accompanied by up to megahertz repetition frequency. Such a light source extends experimental capabilities in spectroscopy, photon counting, imagining, photo-induced material processing and warm dense plasma creation. We propose to settle a high average power VUV FEL facility POLFEL at the Andrzej Soltan Institute for Nuclear Studies in Świerk. POLFEL is planned as a node of the EuroFEL network of complementary facilities, recommended by ESFRI. The great weight of the synchrotron radiation studies in modern science and technology makes us recognize the next, fourth generation light source facility as an instrument which will effectively improve the impact of research being run in Poland. Presented concept benefits from the long and wide experience of Polish scientists and engineers involved in the FEL activities world wide. Here we present an the overview of the general layout of the planned facility, paying a special attention to its novel solutions. The ground breaking feature of POLFEL is a continuous wave (cw) or near-cw operation. It will be achieved with a linear superconducting (sc) accelerator fed with a low emittance sc-electron injector furnished with the thin film sc lead photocathode. There are three outstanding characteristics of the VUV radiation emitted by FEL, which are often named as its fundamental advantages: femtosecond pulse duration, huge peak brilliance and high average intensity. As the first two of them are adequately accounted in the existing facilities or those being in the advanced phase of construction: FLASH, FERMI and LCLS, we turn our efforts towards the last of mentioned parameters – the average power. The principal goal, which dictates that approach, is to enable experiments requiring maximization of the time integrated number of interacting photons. They are experiments dealing with diluted samples and/or processes occurring with a low probability [1-3]. For those experiments, the significant improvement of experimental capabilities can be achieved when the recent progress in reduction of detectors readout time [4] goes together with the higher repetition rate of the light source. POLFEL will operate basing on the SASE (Self-Amplified Spontaneous Emission) principle [5] and will generate the light as displayed in Table 1.
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    ABSTRACT: Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique “fingerprint”. Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10−5 to below 10−8 for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an A_dvanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10−9 can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e.g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility. Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner. The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with β-delayed neutron detection) has been achieved with rates of only a few atoms per second. This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively.
    The European Physical Journal Special Topics · 1.76 Impact Factor
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    ABSTRACT: We report wavelength measurements of H-like and He-like ions obtained with a novel x-ray spectrometer at the Heidelberg Electron Beam Ion Trap. The experimental uncertainty for the Lyman-alpha1 wavelength in Cl16+ is reduced by a factor of 3 and, as expected, excellent agreement with theory is maintained. For the resonance line in He-like Ar16+, an uncertainty of only deltalambda/lambda=2x10(-6) was achieved. This is the most precise x-ray wavelength reported for highly charged ions to date, and allows to test recent predictions on QED two-electron and two-photon radiative corrections for He-like ions. The results also point to the advantages of establishing absolute x-ray wavelength standards using Lyman-alpha transitions (in the present case Ar17+ Lyman-alpha1) to supersede the current ones.
    Physical Review Letters 10/2007; 99(11):113001. DOI:10.1103/PHYSREVLETT.99.113001 · 7.51 Impact Factor
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