| 1. |
- Akram, Nadeem, 1980-, et al.
(författare)
-
Imaging of ion transmission through glass capillaries
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present a technique which is successfully used to directly observe the charge patches formed on a single glass capillary walls. This is done by imaging the emitted visible photons emitted from 4.5 keV Ar1+-ions -interaction with the inner capillary walls, using a high resolution digital camera. Simultaneously, the ions transmitted through the capillary are detected. The number of emitted photons decreases with the increase in the tilt angle of the capillary. The time evolution of emitted photons has revealed that the charge patches formed by charging-up the capillary walls change their location during ion transmission.
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| 2. |
- Akram, Nadeem, 1980-, et al.
(författare)
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Transmission of highly charged ions through phlogopite-mica nanocapillaries of rectangular cross-section
-
Ingår i: Journal of Physics B. - 0953-4075 .- 1361-6455.
-
Tidskriftsartikel (refereegranskat)abstract
- We measured the transmission of Ne7+ ions through nanocapillaries of rectangular cross-section produced by chemical etching of ion tracks in phlogopite mica. The two dimensional transmitted profiles are rhombic for tilt angles within the geometrical opening angle given by the aspect ratio of the short side of the rectangular cross section of the capillaries. The transmission depends on the incident charge indicating that the rhombic shape is due to the image charge of uncharged rectangular capillaries. Above a critical charge deposition, the rhombic shape tends to be smeared out. Ions are also transmitted at angles larger than the geometrical opening angle giving evidence for the guiding effect.
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| 3. |
- Akram, Nadeem, 1980-
(författare)
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Transmission of slow highly charged ions through nano-structures
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on experimental investigations of transmitting slow highly charged ions through nano-structures of various cross-sections. Transmission through rhombic and rectangular nanocapillaries in muscovite and phlogopite mica, respectively, is used to study the guiding and shaping of highly charged ion beams. The two-dimensional angular distributions of the transmitted ions reveal that slow highly charged ion beams are tailored into rectangular and rhombic shapes after passing through the capillaries of rhombic and rectangular cross-sections, respectively. These transmission profiles are maintained for tilt angles within the geometrical opening angle of the capillaries. The ‘incident charge-dependent’ time evolution of the transmission profiles indicates that the tailored shape comes from the image force experienced by the traversing ions and the deposited charge by the incident ions moves the transmission profiles towards higher observation angles with respect to the beam direction. Transmission is also observed for tilt angles larger than the geometrical opening of the capillaries and evidence of charging-up of capillary walls was seen. Other incident charge-dependent features including the increase in angular width and shift of transmitted angular distributions were also observed. Starting from initially charged capillaries, it was found that the deposited charge must be distributed uniformly along the capillary walls to maintain the tailored rhombic shape through rectangular capillaries. In this thesis, a technique is presented which is successfully employed to investigate directly the formation of charge patches on the walls of a glass capillary by imaging the visible photons emitted due to impact of ions on the walls. These tapered glass capillaries were applied in biological studies of cell damage by ion impact and the technique provides a new way to directly observe the development of ion-guiding in these capillaries. With the help of this technique the mechanism of ion-guiding can be controlled and optimized. We also review the transmission characteristics of slow highly charged ions through nanometer thick foils and present the results of transmission of slow highly charged ions through ultra-thin carbon nano-sheets of molecular layer thickness. The observed energy loss is smaller than the calculated one using SRIM and agrees rather well with the Firsov model. The transmitted ions also keep their initial charge state up to 98% in a complete contradiction to the electron capture rate predicted by the classical over-the-barrier model. The results suggest that the energy loss of slow highly charged ions in such thin sheets is due to the electronic excitations, without charge exchange inside the target.
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| 4. |
- Akram, Nadeem, et al.
(författare)
-
Transmission of slow highly charged ions through rectangular nanocapillaries
- 2014
-
Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP).
-
Konferensbidrag (refereegranskat)abstract
- Transmission of slow highly charged ions through rectangular nanocapillaries in phlogopite mica is studied. The transmission profiles have rhombic pattern at tilt angles within the geometrical opening angle of the capillaries. The time evolution of ion transmission reveals certain features contributing to the tailored transmission profiles.
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| 5. |
- Akram, Nadeem, 1980-, et al.
(författare)
-
Transmission of slow highly charged ions through ultra-thin carbon nano-sheets
- 2011
-
Ingår i: Proceedings of 3<sup>rd</sup> Int. Conf. on “Current developments in Atomic, Molecular, Optical and Nano Physics”.
-
Konferensbidrag (refereegranskat)abstract
- Transmission properties of slow highly charged ions through nanometer thick foils are discussed. We also report on the measurement of the energy loss and the charge states of 46.2 keV Ne10+-ions and 11.7 keV Ne3+-ions transmitted through ultra-thin carbon nano-sheets. The sheets had a thickness of 1.2 nm (single molecular layer) and 3.6 nm (three molecular layers). The measured energy loss of the transmitted ions is considerably smaller than the calculated energy loss by SRIM but it is in agreement with energy loss calculated using the Firsov model. The majority of the transmitted ions retain their initial charge state (up to 98%) contrary to prediction by the classical over-the-barrier model. The results suggest that the energy loss of slow highly charged ions in such thin sheets is only due to the electronic excitations, without charge exchange inside the target.
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| 6. |
- Ali, Mona, et al.
(författare)
-
Measuring the nonlinear optical properties of indium tin oxide thin film using femtosecond laser pulses
- 2020
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 37:11, s. A139-A146
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the nonlinear optical properties of indium tin oxide (ITO) thin film coated on soda-lime glass substrate using the z-scan technique. With 100 fs laser pulses, the nonlinear absorption coefficient and nonlinear refractive index are measured at different excitation wavelengths and at different incident intensities. The nonlinear optical absorption shows a competition between saturable absorption and reverse saturable absorption at the different excitation wavelengths and incident intensities. A transition from saturable to reverse saturable absorption was observed with increasing excitation wavelengths. The measured nonlinear refractive index was found to be dependent on wavelength with a maximum value of 5.34 x 10(-12) cm(2)/W at wavelength of 900 nm.
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| 7. |
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| 8. |
- Ali, Safdar, 1982-
(författare)
-
Electron - Ion Recombination Data for Plasma Applications : Results from Electron Beam Ion Trap and Ion Storage Ring
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contains results of electron-ion recombination processes in atomic ions relevant for plasma applications. The measurements were performed at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) and at the CRYRING heavy-ion storage ring. Dielectronic recombination (DR) cross sections, resonant strengths, rate coefficients and energy peak positions in H-like and He-like S are obtained for the first time from the EBIT measurements. Furthermore, the experimentally obtained DR resonant strengths are used to check the behaviour of a scaling formula for low Z, H-and He-like iso-electronic sequences and to update the fitting parameters. KLL DR peak positions for initially He- to B-like Ar ions are obtained experimentally from the EBIT measurements. Both the results from highly charged sulfur and argon are compared with the calculations performed with a distorted wave approximation.Absolute recombination rate coefficients of B-like C, B-like Ne and Be-like F ions are obtained for the first time with high energy resolution from storage ring measurements. The experimental results are compared with the intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients of each of these ions are obtained by convoluting the energy dependent recombination spectra with a Maxwell-Boltzmann energy distribution in the temperature range of 103-106 K. The resulting plasma rate coefficients are presented and compared with the calculated data available in literature.
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| 9. |
- Ali, Safdar, et al.
(författare)
-
Electron-ion recombination of H- and He-like sulfur
- 2011
-
Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 44:22, s. 225203-
-
Tidskriftsartikel (refereegranskat)abstract
- Electron-ion recombination of sulfur ions with electrons in the energy range of 1.6-3 keV was studied at the Stockholm Refrigerated Electron Beam Ion Trap. We obtained the KLn dielectronic recombination (DR) cross sections up to n = 5 for H-like and He-like sulfur ions by observing the x-rays from the trapped ions. A fully relativistic distorted wave approximation method was used for calculating the DR cross sections, while the resonance energies were obtained with a multiconfiguration Dirac-Fock approach using the GRASP II code. The calculations agree with the experimental results within the experimental error bars. Additionally, the obtained total DR resonance strengths were used to check the behaviour of a scaling formula for low-Z, He-like iso-electronic sequence (Watanabe et al 2001 J. Phys. B: At. Mol. Opt. Phys. 34 5095).
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| 10. |
- Ali, Safdar, et al.
(författare)
-
Electron-ion recombination rate coefficients for C II forming C I
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:2, s. 132-
-
Tidskriftsartikel (refereegranskat)abstract
- We have determined absolute dielectronic recombination rate coefficients for C II, using the CRYRING heavy-ions storage ring. The resonances due to 2s-2p (∆n = 0) core excitations are detected in the center-of-mass energy range of 0-15 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients are obtained from the DR spectrum by convoluting it with a Maxwell-Boltzmann energy distribution for temperatures in the range of 103-106 K. The derived temperature dependent plasma recombination rate coefficients are presented graphically to compare with the theoretical data available in literature and parameterized by using a fit formula for convenient use in plasma modelling codes. In the temperature range of 103-2×104 K, our experimental results show that previous calculations severely underestimate the plasma rate coefficients and also our AUTOSTRUCTURE calculation does not reproduce the experimental plasma rate coefficients well. Above 2×104 K the agreement between the experimental and theoretical rate coefficients is much better, and the deviations are smaller than the estimated uncertainties.
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| 11. |
- Ali, Safdar, et al.
(författare)
-
Experimental rate coefficients of F5+ recombining into F4
- 2013
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 557
-
Tidskriftsartikel (refereegranskat)abstract
- Recombination spectra of F5+ producing F4+ have been investigated with high-energy resolution, using the CRYRING heavy-ion storage ring. The absolute recombination rate coefficients are derived in the centre-of-mass energy range of 0-25 eV. The experimental results are compared with intermediate-coupling AUTOSTRUCTURE calculations for 2s-2p (Delta n = 0) core excitation and show very good agreement in the resonance energy positions and intensities. Trielectronic recombination with 2s(2)-2p(2) transitions are clearly identified in the spectrum. Contributions from F5+ ions in an initial metastable state are also considered. The energy-dependent recombination spectra are convoluted with Maxwell-Boltzmann energy distribution in the 10(3)-10(6) K temperature range. The resulting temperature-dependent rate coefficients are compared with theoretical results from the literature. In the 10(3)-10(4) K range, the calculated data significantly underestimates the plasma recombination rate coefficients. Above 8 x 10(4) K, our AUTOSTRUCTURE results and plasma rate coefficients from elsewhere show agreement that is better than 25% with the experimental results.
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| 12. |
- Ali, Safdar, et al.
(författare)
-
Experimental recombination rate coefficients of Be-like Frecombining into B-like F
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recombination spectra of F VI forming F V have been investigated with high-energy resolution, using the CRYRING heavy-ion storage ring. The absolute recombination rate coefficients are derived in the center-of-mass energy range of 0-25 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations for 2s-2p (∆n=0) core excitation and show a very good agreement in the resonance energy positions and intensities. Trielectronic recombination with 2s2-2p2 transitions are clearly identified in the spectrum. Metastable ion contributions are considered and found negligible. The energy dependent recombination spectra are convoluted with Maxwell-Boltzmann energy distribution in the 10-106 K temperature range. The resulting temperature dependent rate coefficients are compared with theoretical results from literature. In the 103-104 K range the calculated data significantly underestimates the plasma recombination rate coefficients. Above ~105 K, our AUTOSTRUCTURE results and plasma rate coefficients from Colgan et al. (2003) show an agreement better than 20% with the experimental results.
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| 13. |
- Ali, Safdar, et al.
(författare)
-
Photo-recombination studies at R-EBIT with a Labview control and data = quisition system
- 2011
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 6, s. C01016-
-
Tidskriftsartikel (refereegranskat)abstract
- Equipment at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) was developed for photo-recombination studies. A LabView-based event mode data acquisition and R-EBIT control system was implemented. The energies of KLL dielectronic recombination resonances in Li- to C-like argon ions were determined and compared with theoretical calculations performed using a distorted wave approximation. The theoretical and experimental peak positions for Li-, Be-, and C-like argon ions agree within the error bars. For B-like argon we observe an energy shift of 9 eV between the experimentally obtained peak position and the calculated result.
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| 14. |
- Bergström, I, et al.
(författare)
-
High-precision Mass Measurements of Hydrogen-Like 24Mg11+ and 26Mg11+ ions in a Pening Trap
- 2002
-
Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 22:1, s. 41-45
-
Tidskriftsartikel (refereegranskat)abstract
- For the determination of the bound-electron g factor in hydrogen-like heavy ions the mass of the ion is needed at a relative uncertainty of at least 1 ppb. With the SMILETRAP Penning trap mass spectrometer at the Manne Siegbahn Laboratory in Stockholm several mass measurements of ions with even-even nuclei at this level of precision have been performed so far, exploiting the fact that the mass precision increases linearly with the ion charge. Measurements of masses of the hydrogen-like ions of the two Mg-isotopes 24Mg and 26Mg are reported. The masses of the hydrogen-like ions are 23.979011054(14) u and 25.976562354(34) u, corresponding to the atomic masses 23.985041690(14) u and 25.982592986(34) u, respectively. The possibility to use these two isotopes for the first observation of an isotope effect in the bound-electron g factor in hydrogen-like heavy ions is discussed.
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| 15. |
|
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| 16. |
- Böhm, Sebastian, et al.
(författare)
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First results from the Stockholm Electron Beam Ion Trap
- 2007
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 58:303, s. 303-306
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Tidskriftsartikel (refereegranskat)abstract
- A new laboratory for highly charged ions is being built up at Stockholm university. An electron beam ion trap (EBIT) (3T magnet,≤30 keV electron beam) was installed. It is used for spectroscopic studies, precision mass measurements, electron ion collisions, and highlycharged ion surface studies. Here we report about a fast ion-extraction scheme from ebit and first results using a time-of-flight detection as well as a labview based operational system of ebit.
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| 17. |
- Cariatore, N. D., et al.
(författare)
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Water fragmentation induced by ion impact : Fragment-ion-energy determination at different Z(P)/v regimes
- 2017
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 408, s. 198-202
-
Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the energy distributions of positive water ionic fragments produced by ion impact at MeV impact energies. An improved Coulomb explosion model coupled to a classical trajectory Monte Carlo simulation is used to provide energy centroids of the fragments for the dissociation channels resulting from the removal of two to five electrons from the water molecule. This model explicitly includes the post-collisional interaction of the projectile with the resulting ionic fragments affecting their kinetic energy release spectra especially at low impact energies. Theoretical data are benchmarked against recent data collected for 220 keV Xe22+ + H2O collisions which corresponds to a large Zp/v collision parameter. To extend our tests to the low Zp/v regime, fragment species as a function of emission energy and time-of-flight were recorded in 3 MeV Li3+ collisions by using an electrostatic spectrometer and a time-of-flight mass spectrometer, respectively. Present experimental data reveals the existence of multiple-ionization processes leading to charge state up to 4+.
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| 18. |
- Fogle, Jr., Michael, 1974-
(författare)
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Recombination and ionization of astrophysically abundant ions
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The electron-ion recombination and electron-impact ionization of several astrophysically abundant C, N, O, and Ni ions have been investigated using the synchrotron storage ring CRYRING. The recombination rate coefficients predominanty used in the analyses of emission line spectra and for ionization balance calculations are determined from isoelectronic fits and extrapolations of theoretical and limited experimental results available from the literature. The rate coefficients reported by various authors differ by an order of magnitude for various ion species. For low temperature plasmas(<104 K), the available information on resonant recombination rate coefficients is even more limitied and, unfortunately, most available data has been determined from LS coupling calculations, which can have adverse effects on recombination rates due to the mistreatment of autoionizing states. For ions of C, N, and O, the production of metastable states complicates the experimental rate coefficient determinations. Some attempts have been made in this work to utilize both recombination and electron-impact ionization in estimating the metastable ion beam fractions present. Other metastable fractions have been determined by comparing the experimental recombination spectra to intermediate coupling calculations. Some of the absolute recombination rate coefficients reported in this work are given for the first time while many others vastly improve the spectral resolution of previous experiments, allowing for a more detailed study of the low energy resonances which contribute to the resonant recombination rate coefficient at low plasma electron temperatures. This increased resolution has also lead to the observation of trielectronic recombination resonances which greatly influence low temperature recombinaion rates in some ions.
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| 19. |
- Fogle, M, et al.
(författare)
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Electron-ion recombination of Be-like C, N, and O
- 2005
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 442:2, s. 757-766
-
Tidskriftsartikel (refereegranskat)abstract
- The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of N3+ and O4+. Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of O4+, the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.
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| 20. |
- Fritioff, Tomas, et al.
(författare)
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Precise measurements of ionic masses for QED tests
- 2006
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 251:2-3, s. 281-285
-
Tidskriftsartikel (refereegranskat)abstract
- The Penning trap mass spectrometer SMILETRAP is designed for precision mass measurements using the merits of highly charged ions. In this paper we describe the feature of SMILETRAP and give examples of mass measurements involving , , and ions. These emphasize the importance of accurate masses of hydrogen-like and lithium-like ions that are required in the evaluation of g-factor measurements of electrons bound to even–even nuclei and test of QED effects. Highly precise mass measurements can also be used for testing atomic structure calculations and determining atomic binding energies. Relevance of such measurements throughout the periodic system is discussed.
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| 21. |
- Fritioff, Tomas, 1971-
(författare)
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Precision Improvements of Penning Trap Mass Measurements Using Highly Charged Ions : Applications to solving current problems in fundamental physics
- 2002
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In my thesis I describe the improvements of the Penning trap mass spectrometer SMILETRAP. The objective of these improvements have been to increase the reliability and the accuracy with which an atomic mass can be measured using highly charged ions. The improvements have been achieved by stabilizing both the electric and magnetic fields of the trap and by improving the technical performance of the trap system. As a result it has been possible to measure accurately the mass of several atoms ranging from hydrogen to mercury using charge states from 1+ to 52+. It was only possible to use the highest charge states after applying a successful cooling of these ions with Helium during the charge breeding.The technical improvements made a number of interesting accurate mass measurements possible. The measurements of the 3H, 3He, and 4He masses showed that the previously values were wrong. The mass difference between 3H and 3He which is the Q-value of the tritium beta decay has been determined to 18.588(3) keV. The Q-value of the double β-decay of 76Ge was measured at an accuracy of 50 eV. This value is indispensable for the evaluation the Heidelberg-Moscow experiment which aims at finding a possible neutrino-less decay which if present would be a violation of the standard model. The mass ratio of mCs/mp is used to determine the fine structure constant independent of QED calculations. The two decades old anomaly in the mass values of Hg was solved by the mass determination of 198Hg and 204Hg. The mass of 24Mg was measured at an uncertatinty of 0.6 ppb and will be used in the determination of the g-factor of a bound electron in a hydrogen like ions.
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| 22. |
- Grieser, M., et al.
(författare)
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Storage ring at HIE-ISOLDE Technical design report
- 2012
-
Ingår i: The European Physical Journal Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 207:1, s. 1-117
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Forskningsöversikt (refereegranskat)abstract
- We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.
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| 23. |
- Gudmundsson, Magnus, et al.
(författare)
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Angular scattering in fast ion-atom electron transfer collisions : projectile wave diffraction and Thomas mechanisms
- 2010
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:18, s. 185209-
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental angular differential cross sections for double-electron capture in He2+ + He collisions and single-electron capture in H+ + He collisions for the 1.3-12.5 MeV kinetic energy range. In all cases, the total cross sections are dominated by forward scattering peaks in d sigma/d Omega. The shapes and widths (but not the magnitudes) of these peaks are very similar for all energies and for capture of one or two electrons corresponding also to our measured linear increases in the transverse momentum transfers with increasing projectile velocities. These observations may be ascribed to diffraction limitations which are connected to electron transfer probabilities P(b) which are significant in limited regions of b only. For the H+ + He single-electron capture we observe two additional maxima in the angular differential cross sections. We conclude that while the secondary maxima at similar to 0.5 mrad probably have large contributions from the Thomas proton-electron-nucleus scattering mechanism, the third maxima at similar to 0.75 mrad are most likely mainly due to projectile de Broglie wave diffraction.
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| 24. |
- Gumberidze, Alexandre, et al.
(författare)
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Angular Distribution of Characteristic Radiation Following the Excitation of He-Like Uranium in Relativistic Collisions
- 2021
-
Ingår i: Atoms. - : MDPI AG. - 2218-2004. ; 9:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present an experimental and theoretical study of excitation processes for the heaviest stable helium-like ion, that is, He-like uranium occurring in relativistic collisions with hydrogen and argon targets. In particular, we concentrate on angular distributions of the characteristic K alpha radiation following the K -> L excitation of He-like uranium. We pay special attention to the magnetic sub-level population of the excited 1s2l(j) states, which is directly related to the angular distribution of the characteristic K alpha radiation. We show that the experimental data can be well described by calculations taking into account the excitation by the target nucleus as well as by the target electrons. Moreover, we demonstrate for the first time an important influence of the electron-impact excitation process on the angular distributions of the K alpha radiation produced by excitation of He-like uranium in collisions with different targets.
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| 25. |
- Gumberidze, A., et al.
(författare)
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Electron- and proton-impact excitation of heliumlike uranium in relativistic collisions
- 2019
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 99:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the K-shell excitation of He-like uranium (U90+) in relativistic collisions with hydrogen and argon atoms. Performing measurements with different targets, as well as with different collision energies, enabled us to explore the proton- (nucleus-) impact excitation as well as the electron-impact excitation process for the heaviest He-like ion. The large fine-structure splitting in uranium allowed us to partially resolve excitation into different L-shell levels. State-of-the-art relativistic calculations which include excitation mechanisms due to the interaction with both protons (nucleus) and electrons are in good agreement with the experimental findings. Moreover, our experimental data clearly demonstrate the importance of including the generalized Breit interaction in the treatment of the electron-impact excitation process.
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| 26. |
- Herdrich, M. O., et al.
(författare)
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Application of a metallic-magnetic calorimeter for high-resolution x-ray spectroscopy of Fe at an EBIT
- 2024
-
Ingår i: Journal of Physics B. - 0953-4075 .- 1361-6455. ; 57:8
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present an experiment conducted at the S-EBIT-I ion trap of GSI. It involved the study of ion-electron collisions of Fe and Ba ions in various charge states with the electron beam. Characteristic x-ray radiation emitted during the continuous interaction was recorded utilizing an energy-dispersive maXs-30 detector based on metallic-magnetic calorimeter (MMC) technology. Optimizations to the applied sensitivity-drift correction and energy calibration procedures significantly improved the achieved energy resolution compared to previous applications of a similar detector. This made it possible to individually resolve and identify overlapping x-ray lines of iron and barium in a wide spectral range. As a demonstration of the outstanding detector performance, we used the recorded spectral data to extract an estimate of the charge state distribution of Fe ions in the trap. This experiment campaign marks an important milestone in the ongoing effort to enable the deployment of MMC detectors for future high-precision measurements in fundamental physics experiments.
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| 27. |
- Hobein, Matthias, et al.
(författare)
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A compact time-resolving pepperpot emittance meter for low-energy highly charged ions
- 2011
-
Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T144, s. 014062-
-
Tidskriftsartikel (refereegranskat)abstract
- An emittance meter for pulsed, low-energy ion beams was developed. Based on the pepperpot method, the device is compact and portable. It has been installed at the S-EBIT Laboratory at AlbaNova, Stockholm University, to measure the emittance of highly charged ions extracted from the electron beam ion trap R-EBIT and the cooling trap of the high-precision Penning trap mass spectrometer SMILETRAP II. Using a fast delay-line anode detector, the emittance and time-of-flight of the extracted ions can be measured simultaneously. In this paper, design and data processing system are described and preliminary results are presented.
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| 28. |
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| 29. |
- Hobein, Matthias, et al.
(författare)
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Evaporative Cooling and Coherent Axial Oscillations of Highly Charged Ions in a Penning Trap
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:1, s. 013002-
-
Tidskriftsartikel (refereegranskat)abstract
- Externally, in an electron beam ion trap, generated Ar16+ ions were retrapped in a Penning trap and evaporatively cooled in their axial motion. The cooling was observed by a novel extraction technique based on the excitation of a coherent axial oscillation which yields short ion bunches of well-defined energies. The initial temperature of the ion cloud was decreased by a factor of more than 140 within 1 s, while the phase-space density of the coldest extracted ion pulses was increased by a factor of up to about 9.
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| 30. |
- Hobein, Matthias, 1981-, et al.
(författare)
-
Optimization of the Stockholm R-EBIT for the production and extraction of highly charged ions
- 2010
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 5:C11003
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a refrigerated EBIT (R-EBIT) commissioned at the AlbaNova Research Center at Stockholm University. As an innovative solution, the superconducting magnet and the trapping drift tubes of the R-EBIT are cooled to a temperature of 4 K by a set of two cooling heads connected to helium compressors. This dry, i.e. liquid helium and liquid nitrogen free, system is easily operated and creates highly charged ions at a fraction of the cost of traditional liquid-cooled systems. A pulsed and continuous gas injection system was developed to feed neutral particles into the electron beam in the trap region. This improves significantly the highly charged ion production and R-EBIT performance. Fast extraction of ions from the R-EBIT yields very short ( < 100 ns), charge-separated ion bunches which can be either analysed using a straight time-of-flight section or sent to experimental beam lines following selection in a bending magnet. An emittance meter was used to measure the emittance of the ions extracted from the R-EBIT. The extracted ions were also re-trapped in a cylindrical Penning trap and properties of the re-trapped ions have been measured using the emittance meter. Results of these measurements are reported in this publication.
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| 31. |
- Hobein, Matthias, et al.
(författare)
-
Re-trapping and cooling of highly-charged
- 2009
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 163, s. 012109-
-
Tidskriftsartikel (refereegranskat)abstract
- Presently, a trapping system for cooling highly-charged ions (HCI) is being set up at AlbaNova at Stockholm University. The experiment aims at production of low temperature (emittance) HCI at very low energy. HCI are extracted from the new Stockholm EBIT (S-EBIT) before evaporative cooling is applied in a Penning trap. In the future the cooled ions will be injected into the precision trap of the high-precision mass spectrometer SMILETRAP II. In first tests the emittance of trapped ions was measured and it was shown that highly and low-charged ions could be simultaneously stored
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| 32. |
- Hobein, Matthias, 1981-, et al.
(författare)
-
SMILETRAP II
- 2011
-
Ingår i: Hyperfine Interactions. - : Springer Netherlands. - 0304-3843 .- 1572-9540. ; 199:1-3, s. 141-150
-
Tidskriftsartikel (refereegranskat)abstract
- The new Penning trap mass spectrometer SMILETRAP II has been set up at the AlbaNova Research Center, Stockholm. Based on the former spectrometer SMILETRAP I, it uses the merits of highly-charged ions to achieve high precision in the mass measurements. Various improvements over the SMILETRAP I setup will allow to routinely perform mass measurements with relative uncertainties of 10−10 and below. In this paper we will discuss the limitations of SMILETRAP I and present the corresponding improvements of SMILETRAP II. An overview on the SMILETRAP II setup is given.
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| 33. |
- Hobein, Matthias, 1981-
(författare)
-
The Penning trap mass spectrometer SMILETRAP II and evaporative cooling of highly-charged ions
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accurate mass values have wide-ranging applications in physics and metrology, allowing, for example, to test quantum electrodynamics and fundamental symmetries, to determine fundamental constants, and to establish weight standards. This thesis describes the new high-precision double-Penning trap mass spectrometer SMILETRAP II which aims at relative uncertainties in the mass determination of 10-10 and below. SMILETRAP II exploits the merits of highly-charged ions as the relative precision in the mass determination with Penning traps is directly proportional to the charge state of the ion. The spectrometer was therefore connected to the electron beam ion trap S-EBIT which is designed to produce bare ions of practically any element up to uranium. Technical and experimental developments were realized to overcome limitations that restricted the achievable precision at the former spectrometer SMILETRAP I. The technical developments include, for example, an ion detection setup with close to 100% efficiency and an extremely stable temperature-regulation system. Temperature fluctuations constitute a main limitation for the attainable precision. Cold ions are a prerequisite to reach high precision in experiments with Penning traps. This makes cooling of the ions from the ion sources necessary. Ion temperature measurement and cooling experiments were performed. The transverse temperature of the trapped ions was determined via the emittance of extracted ions. A pepperpot emittance meter was designed to meet the requirements of low-energy, low-intensity beams. To measure the axial temperature and assess the ions’ longitudinal phase-space density, a coherent extraction method was developed. The evaporative cooling technique was successfully implemented. In particular, evaporative cooling of highly-charged ions in a Penning trap could be observed for the first time.
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| 34. |
- Hoshino, Masamitsu, et al.
(författare)
-
Multielectron processes in close collisions of slow Neq+ (q=1-9) ions with Ar atoms
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:3, s. 32722-
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the multielectron processes in close collisions between slow Neq+ ions (q=1-9, energies of 5 and 14 keV) and Ar atoms through measurements of the charge-state correlations between 27 degrees scattered and 70 degrees recoiling ions. At the selected scattering angle, the internuclear distance of the closest approach at 35 keV is comparable to the L-shell radius of Ar atoms. A drastic difference between low-charged (q=1-3) and highly charged (q=7-9) Ne ions was found. For example, the most probable channel for the Ne7+ projectile is three-electron capture accompanied with two-electron loss whereas for the Ne+ projectile pure double ionization was found most probable. As a general trend, the mean charges of the both ions and the mean number of captured electrons increase almost linearly with incident charge q, while the mean number of ejected electrons from the system is independent of q at both 5 and 14 keV. We also measured the charge state distributions of the Ar recoil ions as function of the Neq+ (q=3, 5, and 7) energies between 5 and 63 keV, which corresponds to distances of closest approach between 0.6 a.u. and 0.17 a.u. We found that the charge of the Ar ions increases at internuclear distances less than 0.32 a.u.
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| 35. |
- Jenei, Zsolt, 1978-
(författare)
-
Experimental investigation of molecular solids and vanadium at high pressure and temperature
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Understanding high pressure effects on simple molecular system is of great interest for condensed matter science and geophysics. Accessing the static pressure and temperature regions found in planetary interiors is made possible by the development of the Diamond Anvil Cell technique. We developed a double sided resistive heating method for the membrane DAC operating in low pressure (<0.5 mTorr) pressure environment requiring only 175 W input power to reach sample temperatures up to 1300 K. We applied this technique successfully to study molecular solids at high temperatures, such as H2, N2 and CO2. We made an attempt to determine the melting line of hydrogen and present data up to 26 GPa in agreement with literature. Raman spectroscopy of Nitrogen indicates a high stability of the ε molecular phase, while θ phase is only accessible via certain P, T paths. Studies of solid CO2 at high pressure and temperature lead to the discovery of a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO2-II above 50 GPa at 530-650 K, or by isobaric heating of CO2-III above 55 GPa. From our X-ray diffraction experiment on isothermally compressed H2O we report a coexistence of ice VII and symmetric ice X from the start of the transition pressure 40GPa to just below 100 GPa and a volume change of 4% across the transition. Vanadium, a transition metal undergoes a phase transition upon compression unlike other elements (Nb, Ta) from its group. We confirm the bcc phase transition to rhombohedral structure at 62 GPa under quasi hydrostatic compression in Ne pressure medium. Compression without pressure medium results in a much lower 30 GPa transition pressure at room temperature and 37 GPa at 425 K, pointing to a positive phase line between the bcc and rhombohedral crystalline phases.
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| 36. |
- Lestinsky, M., et al.
(författare)
-
Physics book: CRYRING@ESR
- 2016
-
Ingår i: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 225:5, s. 797-882
-
Forskningsöversikt (refereegranskat)abstract
- The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).
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| 37. |
- Li, P. F., et al.
(författare)
-
Dynamics of low energy electrons transmitting throughstraight glass capillary: Tilt angle dependence br
- 2022
-
Ingår i: Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 71:8
-
Tidskriftsartikel (refereegranskat)abstract
- It is a hot topic that using glass capillary to focus and shape the charged particle beam, for it isinexpensive and simple. There are the cases that single glass capillaries are used to make the microbeam of thepositive ions. When it comes to electrons, their transmitting through insulating capillaries is complex and theattempt to use the glass capillary to produce electron beams in the size of micrometer needs further exploring.In this paper, the charging-up process of the 900-eV electrons transmitting through a glass capillary withthe grounded conductive-coated outer surface is reported. Two-dimensional angular distributions of thetransmitted electrons and their time evolutions are measured for the cases of various tilt angles of glass tube. Itis found that there are a considerable number of transmitted electrons at the tilt angle exceeding thegeometrical opening angle (1 degrees) of the glass tube. The intensity of transmitted electrons for large tilt angle (i.e. -1.15 degrees)can be considered as first falling to zero, then keeping zero for a long time, finally rising to a certain stablevalue. Correspondingly, the angular distribution center experiences moving towards negative-positive-negative-settled. The energy losses are measured for various tilt angles. The larger the tilt angles, the larger the energyloss of transmitted electrons is. To better understand the physics behind the observed phenomena, thesimulations of the energy loss for transmitted electrons at various tilt angles are performed by the Monte Carlomethod. The comparation between the simulated energy losses and the measured energy losses shows that theexperimental results are well explained by multiple deflections from the wall.
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| 38. |
- Li, P. F., et al.
(författare)
-
Stable transmission of low energy electrons in glass tube with outer surface grounded conductively shielding
- 2022
-
Ingår i: Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 71:7
-
Tidskriftsartikel (refereegranskat)abstract
- The electron microbeam is useful for modifying certain fragments of biomolecule. It is successful to applythe guiding effect to making the microbeam of positively charged particles by using single glass capillary.However, the mechanism for the electron transport through insulating capillaries is unclear. Meanwhile,previous researches show that there are oscillations of the transmission intensity of electrons with time in theglass capillaries with outer serface having no grounded conductive shielding, So, the application of glasscapillary to making the microbeam of electrons is limited. In this paper, the transmission of 1.5 and 0.9 keV electrons through the glass capillary without/with thegrounded conductive-coated outer surface are investigated, respectively. This study aims to understand themechanism for low energy electron transport in the glass capillaries, and find the conditions for the steadytransport of the electrons. Two-dimensional angular distribution of the transported electrons and its timeevolution are measured. It is found that the intensity of the transported electrons with the incident energythrough the glass capillaries for the glass capillaries without and with the grounded conductive-coated outersurface show the typical geometrical transmission characteristics. The time evolution of the 1.5- keV electrontransport presents an extremely complex variation for the glass capillary without the grounded conductive-coated outer surface. The intensity first falls, then rises and finally oscillates around a certain mean value.Correspondingly, the angular distribution center experiences moving towards positive-negative-settlement. Incomparison, the charge-up process of the 0.9 keV electron transport through the glass capillary with thegrounded conductive-coated outer surface shows a relatively simple behavior. At first, the intensity declines rapidly with time. Then, it slowly rises till a certain value and stays steady subsequently. The angulardistribution of transported electrons follows the intensity distribution in general, but with some delay. It quicklymoves to negative direction then comes back to positive direction. Finally, it regresses extremely slowly andends up around the tilt angle. To better understand the physics behind the observed phenomena, the simulationfor the interaction of the electrons with SiO2 material is performed to obtain the possible deposited chargedistribution by the CASINO code. Based on the analysis of the experimental results and the simulated chargedeposition, the conditions for stabilizing the electron transport through glass capillary arepresented.
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| 39. |
- Lindroth, Eva, et al.
(författare)
-
Electron-impact recombination and excitation rates for charge-state-selected highly charged Si ions
- 2020
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 101:6
-
Tidskriftsartikel (refereegranskat)abstract
- Charge-state selective recombination rate coefficients were measured by time of flight (TOF) analyzed highly charged Si ions extracted from an electron-beam ion trap. Additionally, the combination of simultaneous TOF and x-ray measurements and a separation of the dielectronic recombination contribution in the x-ray spectra is used for extracting electron-impact excitation rate coefficients for several overlaying charge states. Experimentally derived dielectronic recombination spectra for XIII and XIV Si are compared and found in excellent agreement with the results of relativistic many-body perturbation theory calculations.
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| 40. |
- Lindroth, Eva, et al.
(författare)
-
QED effects in Cu-like Pb recombination resonances near threshold
- 2001
-
Ingår i: Physical Review Letters. - 0031-9007. ; 86:22, s. 5027-5030
-
Tidskriftsartikel (refereegranskat)abstract
- In an electron-ion recombination study with Pb53+ dielectronic recombination resonances are found for as low as similar to 10(-3)-10(-4) eV relative energy. The resonances have been calculated by relativistic many-body perturbation theory and through comparison with experiment the Pb53+(4p(1/2)-4s(1/2)) energy splitting of similar to 118 eV is determined with an accuracy comparable to the position of the first few resonances, i.e., similar to 10(-3) eV. Such a precision provides a test of QED in a many-body environment at a level which can still not be reached in calculations.
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| 41. |
- Liu, Yuwen, et al.
(författare)
-
Improved temperature regulation of Penning trap mass spectrometers
- 2010
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 294:1, s. 28-32
-
Tidskriftsartikel (refereegranskat)abstract
- In order to reach relative uncertainties in mass measurements with Penning traps of 10-10 or better, the temperature variation of the trap and surrounding materials must be kept below 10 mK. Temperature variations induce a shift in the measured ion cyclotron frequency because of non-zero, temperature dependent magnetic susceptibilities of the construction materials. In this paper we report of a new temperature regulation system recently installed at SMILETRAP II that manages to keep the temperature fixed at the set point with a standard deviation of only 2.6 mK. −10 or better, the temperature variation of the trap and surrounding.
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| 42. |
- Mahmood, Sultan, 1969-
(författare)
-
Interaction of atomic ions with electrons : Recombination rate coefficients for C1+, F5+, Ne5+, S14+,S15
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concentrates on electron-ion interaction studies, in particular focusing on dielectronic recombination (DR) of highly charged ions relevant to astrophysics and plasma physics. The measurements were performed at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) and at the CRYRING heavy-ion storage ring. For the R-EBIT measurements a newly developed time-of-flight (TOF) technique for separation of ions and detecting the charge state distribution was utilized. By using ion intensities derived from the TOF spectra as input parameters in the rate equations, energy dependent DR rate coefficients for S15+ and S14+ ions were obtained for the first time. Resonance energies and cross sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. In addition to the TOF spectra, the x-ray spectra have been also collected. The combination of these two measurements allows us to separate the photo-recombination and the excitation spectra, from which the excitation rate coefficients for S15+ and S14+ ions were extracted.From the storage ring measurements absolute recombination rate coefficients for C1+, F5+, and Ne5+ions as a function of electron-ion collision energy were obtained. These were reported for the first time with high energy resolution. The experimental results were compared with results obtained from AUTOSTRUCTURE calculations. Temperature dependent rate coefficients have been also derived for the studied ions and compared with calculations available in the literature.
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| 43. |
- Mahmood, Sultan, 1969-, et al.
(författare)
-
Recombination and electron impact excitation rate coefficients for S XV AND S XVI
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 754:2, s. 86-
-
Tidskriftsartikel (refereegranskat)abstract
- Recombination and electron impact excitation of S14+ and S15+ ions was measured at the Stockholm refrigerated electron beam ion trap. The collision energy range was 1.4-3 keV, where we covered the KLL, KLM, KLN, and KLO dielectronic recombination resonances resulting in S13+ and S14+ ions. The recombination rates were obtained by detecting the charge state distribution with a newly developed time-of-flight technique. Resonance energies and cross sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. The temperature dependent rate coefficients have been extracted from the measured rates and compared with calculations from literature used for studies of collisionally ionized astrophysical plasmas. A good agreement for S15+ was obtained, while the plasma rates for S14+ were 23% lower than the so far published values. In addition to the time-of-flight spectra, the x-ray spectra, produced mainly by photo-recombination and excitation, have been also collected. The combination of these two measurements allowed us to separate the photo-recombination and the excitation spectra, and the excitation rate coefficients for summed intensities with known fractions of S14+ and S15+ ions were extracted.
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| 44. |
- Mahmood, Sultan, et al.
(författare)
-
RECOMBINATION RATE COEFFICIENTS OF BORON-LIKE Ne
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 771:2, s. 78-
-
Tidskriftsartikel (refereegranskat)abstract
- Recombination of Ne5+ was measured in a merged-beam type experiment at the heavy-ion storage ring CRYRING. In the collision energy range 0-110 eV resonances due to 2s(2)2p -> 2s2p(2) (Delta n=0) and 2s(2)2p -> 2s(2)3l (Delta n=1), core excitations were observed. The experimentally derived rate coefficients agree well with the calculations obtained using AUTOSTRUCTURE. At low energies, recombination is dominated by resonances belonging to the spin-forbidden 2s2p(2)(P-4(J))nl series. The energy-dependent rate coefficients were convoluted with a Maxwell-Boltzmann electron energy distribution to obtain plasma recombination rate coefficients. The data from the literature deviate from the measured results at low temperature.
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| 45. |
- Misra, Deepankar, et al.
(författare)
-
Two-Center Double-Capture Interference in Fast He2++H2 Collisions
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:15, s. 153201-
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first observation of Young-type interference effects in a two-electron transfer process. These effects change strongly as the projectile velocity changes in fast (1.2 and 2.0 MeV) He^{2+}-H_2 collisions as manifested in strong variations of the double-electron capture rates with the H_2 orientation. This is consistent with fully quantum mechanical calculations, which ignore sequential electron transfer, and a simple projectile de Broglie wave picture assuming that two-electron transfer probabilities are higher in collisions where the projectile passes close to either one of the H_2 nuclei.
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| 46. |
- Mohamed, Tarek, et al.
(författare)
-
A linear optical trap with active medium for experiments with high power laser pulses
- 2015
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 86:2
-
Tidskriftsartikel (refereegranskat)abstract
- A linear optical trap for circulating high power laser pulses and tuning these pulses to high repetition frequency of several tens of MHz has been developed. A ns excimer pumped dye laser pulse has been injected with help of a Wollaston prism and a synchronized Pockels cell into an optical trap formed by two highly reflecting mirrors in a linear configuration. The test was done at lambda = 580 nm, but the optical trap can be used without limitations in a broad band of optical wavelengths (400-700 nm). Power considerations give an increase of the efficiency of the optical trap of about 7 times compared to single passage of the laser pulse through the experimental section. The time structure of the trapped laser pulses can be controlled by changing the distance between the two high reflecting mirrors. The efficiency of the optical trap strongly depends upon optical losses. To compensate the optical losses, an amplifying cell was introduced, and the efficiency was about 60 times higher than that by single passage of the laser pulse through the experimental section.
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| 47. |
- Mohamed, Tarek, et al.
(författare)
-
A seeded dye laser cavity for intracavity experiments
- 2015
-
Ingår i: Laser physics. - 1054-660X .- 1555-6611. ; 25:9
-
Tidskriftsartikel (refereegranskat)abstract
- A seeded dye laser cavity, synchronously pumped by the 2nd harmonic of the Nd:YAG laser has been designed and experimentally tested. The used seed signal was the well defined narrow linewidth output laser signal (Delta lambda = 0.013 nm) from the excimer-dye laser system. Energy considerations showed that the intracavity laser energy, that can be used for an experimental section inside the cavity, can reach an efficiency of 20% of the pumping energy. The wavelength and linewidth are fully controlled by the wavelength and linewidth of the seeding laser.
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| 48. |
- Mohamed, T., et al.
(författare)
-
Effects of polarization on laser-induced electron-ion recombination
- 2011
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 83:3, s. 032702-
-
Tidskriftsartikel (refereegranskat)abstract
- The polarization dependence of laser-induced radiative recombination (LIR) to D(+) ions was investigated in the electron cooler of the CRYRING storage ring. The LIR gain as a function of wavelength into n = 3 principal quantum states of deuterium was measured at laser beam polarization angles of 0 degrees and 90 degrees with respect to the direction of the motional electric field in the interaction region. For the case of the polarization vector parallel to the external field, there is a double-peak structure in the gain curve that indicates a polarization effect in the LIR process. The two polarization directions also reveal a different width for the respective gain curves, giving additional evidence for the polarization effect, clearly seen by the behavior of a defined polarization parameter. The obtained polarization effect indicates a high sensitivity in recombination processes to external fields.
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| 49. |
- Mohamed, Tarek, et al.
(författare)
-
Nonlinear Optical Properties of Zinc Oxide Nanoparticle Colloids Prepared by Pulsed Laser Ablation in Distilled Water
- 2022
-
Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:23
-
Tidskriftsartikel (refereegranskat)abstract
- The nonlinear optical properties of zinc oxide nanoparticles (ZnONPs) in distilled water were measured using a femtosecond laser and the Z-scan technique. The ZnONPs colloids were created by the ablation of zinc bulk in distilled water with a 532 nm Nd: YAG laser. Transmission electron microscopy, an ultraviolet-visible spectrophotometer, and atomic absorption spectrophotometry were used to determine the size, shape, absorption spectra, and concentration of the ZnONPs colloids. The nonlinear absorption coefficient and nonlinear refractive index were measured at different excitation wavelengths and intensities. The nonlinear absorption coefficient of the ZnONPs colloids was found to be positive, caused by reverse saturable absorption, whereas the nonlinear refractive index was found to be negative due to self-defocusing in the ZnONPs. Both laser parameters, such as excitation wavelength and input intensity, and nanoparticle features, such as concentration and size, were found to influence the nonlinear optical properties of the ZnONPs.
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| 50. |
- Nagy, Szilárd, 1978-
(författare)
-
New atomic masses related to fundamental physics measured with SMILETRAP
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the recent improvements of the SMILETRAP Penning trap mass spectrometer and a number of interesting high precision mass measurements, which have been performed using the improved apparatus, and are relevant in todays fundamental physics problems. The mass of the hydrogen-like 24,26Mg ions as well as the masses of the hydrogen- and lithium-like 40Ca ions are presented in this work that are indispensable input values when evaluating g-factor measurements of the bound electron. In both cases the uncertainty in the masses was improved by one order of magnitude compared to the literature values known so far. The mass of 7Li has been measured and a new mass value has been obtained with an unprecedented relative uncertainty of 6.3x10-10. A large deviation of 1.1 μu (160ppb) compared to the literature value has been observed. In order to find the reason of this large deviation and to look for possible systematics we have measured the mass of 4He and 6Li and concluded that the 6Li(n,γ)7Li reaction Q-value used in the literature when calculating the 7Li mass is wrong by about 1 keV. The mass difference between 3He and 3H (Δ m (3H -3He)) is the Q-value of the tritium β-decay. An accurate knowledge of the tritium Q-value is of importance in the search for a finite rest mass of the electron neutrino. By adding a measurement of the mass of 3He1+ to previous mass measurement of 3H1+ and 3He2+ we have improved our previous Q-value by a factor of 2. At the moment our Q-value is the most accurate and more importantly it is based on the correct atomic mass values.
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