Design report of the KISS-II facility for exploring the origin of uranium

One of the critical longstanding issues in nuclear physics is the origin of the heavy elements such as platinum and uranium. The r-process hypothesis is generally supported as the process through which heavy elements are formed via explosive rapid neutron capture. Many of the nuclei involved in heavy-element synthesis are unidentified, short-lived, neutron-rich nuclei, and experimental data on their masses, half-lives, excited states, decay modes, and reaction rates with neutron etc., are incredibly scarce. The ultimate goal is to understand the origin of uranium. The nuclei along the pathway to uranium in the r-process are in "Terra Incognita". In principle, as many of these nuclides have more neutrons than 238U, this region is inaccessible via the in-flight fragmentation reactions and in-flight fission reactions used at the present major facilities worldwide. Therefore, the multi-nucleon transfer (MNT) reaction, which has been studied at the KEK Isotope Separation System (KISS), is attracting attention. However, in contrast to in-flight fission and fragmentation, the nuclei produced by the MNT reaction have characteristic kinematics with broad angular distribution and relatively low energies which makes them non-amenable to in-flight separation techniques. KISS-II would be the first facility to effectively connect production, separation, and analysis of nuclides along the r-process path leading to uranium. This will be accomplished by the use of a large solenoid to collect MNT products while rejecting the intense primary beam, a large helium gas catcher to thermalize the MNT products, and an MRTOF mass spectrograph to perform mass analysis and isobaric purification of subsequent spectroscopic studies. The facility will finally allow us to explore the neutron-rich nuclides in this Terra Incognita.Comment: Editors: Yutaka Watanabe and Yoshikazu Hirayam

Macroscopic dynamics of a Bose-Einstein condensate containing a vortex lattice

Starting from the equations of rotational hydrodynamics we study the macroscopic behaviour of a trapped Bose-Einstein condensate containing a large number of vortices. The stationary configurations of the system, the frequencies of the collective excitations and the expansion of the condensate are investigated as a function of the angular velocity of the vortex lattice. The time evolution of the condensate and of the lattice geometry induced by a sudden deformation of the trap is also discussed and compared with the recent experimental results of P. Engels et al., Phys. Rev. Lett. 89, 100403 (2002).Comment: 4 pages, 4 figure

Follicular fluid content and oocyte quality: from single biochemical markers to metabolomics

The assessment of oocyte quality in human in vitro fertilization (IVF) is getting increasing attention from embryologists. Oocyte selection and the identification of the best oocytes, in fact, would help to limit embryo overproduction and to improve the results of oocyte cryostorage programs. Follicular fluid (FF) is easily available during oocyte pick-up and theorically represents an optimal source on non-invasive biochemical predictors of oocyte quality. Unfortunately, however, the studies aiming to find a good molecular predictor of oocyte quality in FF were not able to identify substances that could be used as reliable markers of oocyte competence to fertilization, embryo development and pregnancy. In the last years, a well definite trend toward passing from the research of single molecular markers to more complex techniques that study all metabolites of FF has been observed. The metabolomic approach is a powerful tool to study biochemical predictors of oocyte quality in FF, but its application in this area is still at the beginning. This review provides an overview of the current knowledge about the biochemical predictors of oocyte quality in FF, describing both the results coming from studies on single biochemical markers and those deriving from the most recent studies of metabolomic

Development of new ion-separation techniques for short-lived nuclides and the first mass measurements of 52,53K

In this thesis, the first on-line mass measurements of the isotopes 52,53K have been performed. These measurements by multi-reflection time-of-flight mass spectrometry with the ISOLTRAP setup at ISOLDE/CERN are linked to previously measured masses of exotic Ca isotopes, which had shown an unexpected large neutron-shell gap at the neutron number N = 32 for the magic proton core Z = 20. The new measurements provide the first exploration of the N = 32 neutron-shell closure below the proton number Z = 20. With a measured empirical two-neutron shell gap of about 3MeV for 51K, the N = 32 gap is smaller as compared to that of 52Ca, which measures about 4MeV, but is still significantly present. This confirms that the nuclear shell effect measured for calcium isotopes is not a phenomenon purely raised by its closed-proton-shell configuration, but is also present in potassium isotopes that possess an open proton shell and an unpaired proton. The second main objective of this thesis was the development of new techniques for efficient mass separation in Penning traps and multi-reflection devices, because the success of nuclear mass measurements with high precision depends crucially on the purity of the ion ensemble. The two main difficulties that have been addressed are, first, when the masses of the ions of interest and the masses of contaminant ions are very similar, and second, when the contaminant ions are predominantly present in the beam from ISOLDE. For the removal of contaminant ions in a high-vacuum Penning trap with high resolving power, a new technique for mass separation has been developed. A simultaneous application of a dipolar radio-frequency field at the magnetron frequency of all ions (mass independent at leading order) and a quadrupolar radio-frequency field at the cyclotron frequency (highly mass dependent) of a chosen ion species provides a new way of ion purification. The result is that the magnetron radius of all ions is increased by the effect of the dipolar excitation, and, at the same time, the quadrupolar excitation leads to a conversion of the radial eigenmotions for the chosen species. The consequence of this simultaneous process is that the wanted ions move back to the trap axes while all other ions are radially ejected from the trap. The advantage of the new method is the simultaneous ejection of all unwanted species in a high vacuum, which otherwise have to be addressed by a dipolar excitation at different frequencies, or by use of complex waveforms if a broadband ejection is required. A comparable (general) broadband ejection as achieved by the new method was previously only achieved in buffer-gas filled Penning traps. Further technical developments were performed with ISOLTRAP’s multi-reflection time-of-flight mass separator. The goal was to improve on situations when dealing with highly contaminated beams from ISOLDE during on-line Penning-trap measurements. In such cases, the number of events obtained in a limited time can be very low for the reason that only a limited number of ions, which predominantly consist of contaminant ions, can be stored and separated in the multi-reflection device at a given time to avoid non-negligible Coulomb interactions between the ions. The situation at ISOLTRAP has been significantly improved by a more efficient use of the separation cycle of the multi-reflection device. The mass-separation cycle is by far shorter (on the order of 10 ms) than a Penning-trap mass measurement (on the order of seconds). Thus, the separation in the multi-reflection device has been decoupled from the Penning-trap mass measurement and is repeated rapidly, while the purified ions are accumulated, stored, and cooled in the preparation Penning trap of ISOLTRAP. The collected ions of interest can then be transferred to the precision-measurement trap. This method increases the possible ratio of the number of contaminant ions to ions of interest by up to two orders of magnitude, i.e. the ratio of the corresponding process durations. Additionally, space-charge problems in multi-reflection devices have been investigated by setting up an off-line apparatus at Greifswald. The dynamical effects of ions in multi-reflection devices under non-negligible Coulomb interactions have been investigated in order to search for possibilities for improvements on such situations. This resulted in a new method of manipulating the ion densities in the device. The ions move in a cloud with large spatial extend for the major part of the trapping time and can later be compressed to small bunches for high-resolution mass separation. Proof-of-principle measurement have been performed with a low number of stored ions, where successful isobar separation has been demonstrated.In dieser Arbeit wurden die ersten Massenmessungen an den Isotopen 52,53K durchgeführt. Diese Messungen wurden mittels Multireflexions-Flugzeitmassenspektroskopie an der ISOLTRAP Apparatur in der ISOLDE Einrichtung am CERN ausgeführt und sind mit Resultaten vorheriger Massenmessungen an exotischen Calciumnukliden verknüpft. Diese zeigten eine unerwartet große Energielücke bei der Neutronenzahl N=32, welche auf einen Neutronenschalenabschluss hindeutet. Die neuen Messungen liefern die erste Untersuchung des Neutronenschalenabschlusses bei N=32 unterhalb der Protonenzahl Z=20. Mit einer gemessenen empirischen Zwei-Neutronen Energielücke von in etwa 3MeV für 51K, ist diese kleiner als bei 52Ca, welche etwa 4MeV beträgt, aber dennoch signifikant. Dies bestätigt, dass der Kernschaleneffekt der für Calcium gemessen wurde, kein reiner Effekt aufgrund der geschlossenen Protonenschale ist, sondern ebenso in Kalium Isotopen erkennbar ist, welche eine offene Protonenschale und ein ungepaartes Proton besitzen. Das zweite Hauptziel dieser Arbeit war die Entwicklung neuer Techniken zur effizienten Massenseparation in Penningfallen und Multireflexionsmassenseparatoren, denn der Erfolg von hochpräzisen Kennmassenbestimmungen hängt stark von der Reinheit der Ionenensembles ab. Die zwei maßgeblichen Probleme sind zum einen, wenn die Massen der gewünschten und der kontaminierten Ionen sehr dicht beieinander liegen und zum anderen, wenn die kontaminierenden Ionen eine dominante Präsenz im Ionenstrahl der ISOLDE Einrichtung haben. Zur Entfernung von unerwünschten Ionen aus einer Hochvakuumpenningfalle mit hoher Massenauflösung wurde eine neue Technik entwickelt. Die simultane Einstrahlung eines dipolförmigen Radiofrequenzfeldes mit der Magnetronfrequenz aller Ionen (in erster Näherung massenunabhängig) und eines quadrupolförmigen Radiofrequenzfeldes mit der Zyklotronfrequenz (hochgradig massenabhängig) der gewünschten Ionenspezies liefert eine neue Methode zur Reinigung von Ionenensembles. Der Magnetronradius aller Ionen vergrößert sich durch die Dipolanregung und die gleichzeitige Quadrupolanregung für die ausgewählte Spezies bewirkt eine Konversion der beiden radialen Eigenbewegungen ineinander. Durch den simultanen Prozess bewegen sich die gewünschten Ionen zur Fallenmitte, während alle anderen Ionen radial aus der Falle getrieben werden. Der Vorteil der neuen Methode liegt in der gleichzeitigen Entfernung aller unerwünschten Ionen in einer Hochvakuumumgebung, welche anderenfalls durch Dipolanregungen auf verschiedenen Frequenzen adressiert werden müssen oder durch eine komplexe Wellenform, wenn eine breitbandige Entfernung benötigt wird. Eine vergleichbare generelle breitbandige Entfernung, die durch die neue Methode erreicht wird, war zuvor nur mit Hilfe von Puffergas in der Penningfalle möglich. Weitere technische Entwicklungen wurden für den Multireflexionsflugzeitmassenseparator von ISOLTRAP durchgeführt. Das angestrebte Ziel war eine Verbesserung für Situationen in denen ein stark kontaminierter Ionenstrahl von der ISOLDE Einrichtung für eine Penningfallenmessung geliefert wird. In solchen Fällen kann die Anzahl an gemessenen (erwünschten) Events in einer begrenzten Zeit sehr niedrig sein, weil, zum geringhalten der störenden Coulomb Kräfte zwischen den Ionen, nur eine begrenzte Anzahl an Ionen im Multireflexionsseparator gleichzeitig separiert werden können und diese Ionen fast ausschließlich aus kontaminierenden Spezies bestehen. Durch einen effizienteren Separationszyklus des Multireflexionsseparators konnte die Situation bei ISOLTRAP erheblich verbessert werden. Die Dauer des Separationsprozesses ist deutlich kürzer (in der Größenordnung von 10 ms) als die einer Penningfallenmassenmessung (in der Größenordnung von Sekunden). Deshalb wurde der Separationszyklus von der Massenmessung entkoppelt und wird mehrfach wiederholt während die gereinigten Ionen in der Präparationspenningfalle von ISOLTRAP akkumuliert, gespeichert und gekühlt werden. Die akkumulierten Ionen können dann gemeinsam zur Präzisionspenningfalle transferiert werden. Diese Methode erhöht das behandelbare Verhältnis von kontaminierenden zu gewünschten Ionen um bis zu zwei Größenordnungen, was dem Verhältnis der korrespondierenden Prozessdauern entspricht. Weiterhin wurden Raumladungsprobleme in Multireflexionsmassenseparatoren durch den Aufbau einer offline Apparatur in Greifswald untersucht. Die dynamischen Effekte von Ionen unter dem nicht vernachlässigbaren Einfluss der Coulomb Wechselwirkung wurde mit dem Ziel nach möglichen Verbesserungen in solchen Situationen zu forschen, untersucht. Daraus wurde eine neue Methode zur Manipulation von Ionendichten in der Apparatur entwickelt. Für den Großteil der Speicherzeit bewegen sich die Ionen in einer räumlich ausgedehnten Formation und können später für die hochauflösende Massensperation verdichtet werden. Für eine kleine Anzahl von Ionen konnte bereits eine erfolgreiche Trennung von isobaren Spezies demonstriert werden

Scissors mode of a rotating Bose-Einstein condensate

A scissors mode of a rotating Bose-Einstein condensate is investigated both theoretically and experimentally. The condensate is confined in an axi-symmetric harmonic trap, superimposed with a small rotating deformation. For angular velocities larger than $\omega_\perp/\sqrt2$, where $\omega_\perp$ is the radial trap frequency, the frequency of the scissors mode is predicted to vanish like the square root of the deformation, due to the tendency of the system to exhibit spontaneous rotational symmetry breaking. Measurements of the frequency confirm the predictions of theory. Accompanying characteristic oscillations of the internal shape of the condensate are also calculated and observed experimentally

Fluorescence detection as a new diagnostics tool for electrostatic ion beam traps

In the development towards the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS), an optical detection region for the observation of fluorescent light is added to an electrostatic ion beam trap (EIBT). In addition to its use for highly sensitive collinear laser spectroscopy, this fluorescence detection is introduced as a diagnostics tool for the study of the ion dynamics inside an EIBT. First measurements of collision-induced fluorescence in an EIBT demonstrate the technique’s diagnostics power by tracking the evolution of an ion bunch’s temporal width over its storage time inside the ion trap. Thereby, the time-focus point of the ion bunch can be determined and the influence of space-charge effects in the EIBT can be investigated. Good qualitative agreement is obtained between the measured trend of temporal widths and the simulations of the ions’ trajectories in the trap. Particularly, the observation of self-bunching on the ion-bunch structure for many simultaneously stored ions is reproduced

First steps in the development of the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy

Collinear laser spectroscopy (CLS) has been combined with the multi-reflection time-of-flight (MR-ToF) technique. To this end, a photodetection system has been implemented at the drift region of a MR-ToF apparatus and a laser beam has been sent along the path of the ions that are stored between the two ion-optical mirrors. The main goal of the present proof-of-principle (PoP) experiments, is the confirmation of the expected increase in sensitivity compared to conventional fluorescence-based CLS due to the repeated probing of the trapped ion bunches. The novel method will be used for the precise measurement of nuclear ground- and isomeric-state properties of exotic nuclei with low production yields at radioactive ion-beam facilities. A significant sensitivity improvement of CLS is expected, depending on the half-life and mass of the nuclide of interest. The status of the PoP setup and future improvements are discussed.Collinear laser spectroscopy (CLS) has been combined with the multi-reflection time-of-flight (MR-ToF) technique. To this end, a photodetection system has been implemented at the drift region of a MR-ToF apparatus and a laser beam has been sent along the path of the ions that are stored between the two ion-optical mirrors. The main goal of the present proof-of-principle (PoP) experiments, is the confirmation of the expected increase in sensitivity compared to conventional fluorescence-based CLS due to the repeated probing of the trapped ion bunches. The novel method will be used for the precise measurement of nuclear ground- and isomeric-state properties of exotic nuclei with low production yields at radioactive ion-beam facilities. A significant sensitivity improvement of CLS is expected, depending on the half-life and mass of the nuclide of interest. The status of the PoP setup and future improvements are discussed