Sadegh Ebrahimi

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ABSTRACT

We perform a detailed experimental study of resistive cooling of large ensembles of highly charged ions such as Ar13+ in a cryogenic Penning trap. Different from the measurements reported by Vogel et al. [M. Vogel et al., Phys. Rev. A 90, 043412 (2014)], we observe purely exponential cooling behavior when conditions are chosen to allow collisional thermalization of the ions. We provide evidence that in this situation resistive cooling time constants and final… Mehr anzeigen

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ABSTRACT

We perform a detailed experimental study of resistive cooling of large ensembles of highly charged ions such as Ar13+ in a cryogenic Penning trap. Different from the measurements reported by Vogel et al. [M. Vogel et al., Phys. Rev. A 90, 043412 (2014)], we observe purely exponential cooling behavior when conditions are chosen to allow collisional thermalization of the ions. We provide evidence that in this situation resistive cooling time constants and final temperatures are independent of the initial ion energy and that the cooling time constant of a thermalized ion ensemble is identical to the single-ion cooling time constant. For sufficiently high ion number densities, our measurements show discontinuities in the spectra of motional resonances which indicate a transition of the ion ensemble to a fluidlike state when cooled to temperatures below approximately 14 K. With the final ion temperature presently being 7.5 K, ions of the highest charge states are expected to form ion crystals by mere resistive cooling, in particular not requiring the use of laser cooling.

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An important aspect of precision measurements in a Penning trap is the ability to cool the confined particles to cryogenic temperatures, which reduces the measurement uncertainty. The ARTEMIS Penning trap, located at the HiTrap facility at GSI, is designed to measure the g−factor of heavy to medium highly charged ions, such as 40Ar13+ and 209Bi82+, using microwave-laser double resonance spectroscopy on a ppb level of accuracy. The foreseen measurement scheme involves spectroscopy of a large… Mehr anzeigen

An important aspect of precision measurements in a Penning trap is the ability to cool the confined particles to cryogenic temperatures, which reduces the measurement uncertainty. The ARTEMIS Penning trap, located at the HiTrap facility at GSI, is designed to measure the g−factor of heavy to medium highly charged ions, such as 40Ar13+ and 209Bi82+, using microwave-laser double resonance spectroscopy on a ppb level of accuracy. The foreseen measurement scheme involves spectroscopy of a large number of confined particles in the form of an ensemble, typically of the order of 105 ions. This thesis presents the development and upgrades of the non-destructive detection system of ARTEMIS, which is also used for resistive ion cooling through dissipative interaction with the effective resistance of the detection system. A theoretical treatment of resistive cooling of an ion ensemble created in the creation trap of ARTEMIS was performed and test with different ion ensembles. Weniger anzeigen

We have conceived, built, and operated a cryogenic Penning trap with an electrically conducting yet optically transparent solid electrode. The trap, dedicated to spectroscopy and imaging of confined particles under large solid angles, is of “half-open” design with one open endcap and one closed endcap that mainly consists of a glass window coated with a highly transparent conductive layer. This arrangement allows for the trapping of externally or internally produced particles and yields… Mehr anzeigen

We have conceived, built, and operated a cryogenic Penning trap with an electrically conducting yet optically transparent solid electrode. The trap, dedicated to spectroscopy and imaging of confined particles under large solid angles, is of “half-open” design with one open endcap and one closed endcap that mainly consists of a glass window coated with a highly transparent conductive layer. This arrangement allows for the trapping of externally or internally produced particles and yields flexible access for optical excitation and efficient light collection from the trapping region. At the same time, it is electrically closed and ensures long-term ion confinement under well-defined conditions. With its superior surface quality and its high as well as homogeneous optical transmission, the window electrode is an excellent replacement for partially transmissive electrodes that use holes, slits, metallic meshes, and the like. Weniger anzeigen

We present two Penning trap experiments concerned with different aspects of the physics of extreme electromagnetic fields, the ARTEMIS experiment designed for boundelectron magnetic moment measurements in the presence of the extremely strong fields close to the nucleus of highly charged ions, and the HILITE experiment, in which welldefined ion targets are to be subjected to high-intensity laser fields.

We have measured the characteristics of a superconducting radio-frequency resonator in an external magnetic field. The magnetic field strength has been varied with 10 mT resolution between zero and 6 T. The resonance frequency and the quality factor of the resonator have been found to change significantly as a function of the magnetic field strength. Both parameters show a hysteresis effect which is more pronounced for the resonance frequency. Quantitative knowledge of such behaviour is… Mehr anzeigen

We have measured the characteristics of a superconducting radio-frequency resonator in an external magnetic field. The magnetic field strength has been varied with 10 mT resolution between zero and 6 T. The resonance frequency and the quality factor of the resonator have been found to change significantly as a function of the magnetic field strength. Both parameters show a hysteresis effect which is more pronounced for the resonance frequency. Quantitative knowledge of such behaviour is particularly important when experiments require specific values of resonance frequency and quality factor or when the magnetic field is changed while the resonator is in the superconducting state. Weniger anzeigen

Highly charged ions offer the possibility to measure electronic fine structures and hyperfine structures with precisions of optical lasers. Microwave spectroscopy of transitions between Zeeman substates further yields magnetic moments (g-factors) of bound electrons, making tests of calculations in the framework of bound-state QED possible in the strong-field regime. We present the SPECTRAP and ARTEMIS experiments, which are currently being commissioned with highly charged ions in the framework… Mehr anzeigen

Highly charged ions offer the possibility to measure electronic fine structures and hyperfine structures with precisions of optical lasers. Microwave spectroscopy of transitions between Zeeman substates further yields magnetic moments (g-factors) of bound electrons, making tests of calculations in the framework of bound-state QED possible in the strong-field regime. We present the SPECTRAP and ARTEMIS experiments, which are currently being commissioned with highly charged ions in the framework of the HITRAP facility at GSI, Germany. We present the scientific outline, the experimental setups and first results with confined ions. Weniger anzeigen

We present two Penning trap experiments concerned with different aspects of the physics of extreme electromagnetic fields, the ARTEMIS experiment designed for boundelectron magnetic moment measurements in the presence of the extremely strong fields close to the nucleus of highly charged ions, and the HILITE experiment, in which welldefined ion targets are to be subjected to high-intensity laser fields.