High-resolution Mass Separation Research Articles

PIPERADE: A double Penning trap for mass separation and mass spectrometry at DESIR/SPIRAL2

A double Penning trap is being commissioned at CENBG Bordeaux for the future DESIR/SPIRAL2 facility of GANIL. The setup is designed to perform both high-resolution mass separation of the ion beam for trap-assisted spectroscopy, and high-accuracy mass spectrometry of short-lived nuclides. In this paper, the technical details of the new device are described. First offline tests with the purification trap are also presented, showing a mass resolving power of about 105.

High-resolution mass separation between helium and deuterium with conventional quadrupole mass spectrometer by using varied ionization energy

A new effective and reliable method is developed to monitor deuterium and helium by a conventional quadrupole mass spectrometer RGA200. The measurement of atomic mass unit (AMU) = 4 is obtained at the ionization energies set of 40 eV and 70 eV instead of 25 eV and 70 eV on RGA200. By this method, not only the minimum deuterium pressure lower limit is widened to ∼10−7 Pa, but also the detection ratio of deuterium to helium is extended to 1–100%. Likewise, it is applied to helium measurement. The calculation error of deuterium mainly depends on the ratio of deuterium to the sum of deuterium and helium. Most of the deuterium calculation errors are modified in the range of 2%–16%. The errors of the calculation results are within the acceptable range of the experiments in the EAST tokamak. It has been successfully applied in EAST 2019 campaign, during helium discharge cleaning process. It provides a viable method which can achieve high-resolution mass separation between helium and deuterium by RGA200 using varied ionization energy.

β decay of Cd127 and excited states in In127

A dedicated spectroscopic study of the β decay of 127Cd was conducted at the IGISOL facility at the University of Jyvaskyla. Following high-resolution mass separation in a Penning trap, β-γ-γ coincidences were used to considerably extend the decay scheme of 127In. The β-decaying 3/2+ and 11/2- states in 127Cd have been identified with the 127Cd ground state and the 283-keV isomer. Their respective half-lives have been measured to 0.45(+12-8)s and 0.36(4) s. The experimentally observed β feeding to excited states of 127In and the decay scheme of 127In are discussed in conjunction with large-scale shell-model calculations.

In-depth study of in-trap high-resolution mass separation by transversal ion ejection from a multi-reflection time-of-flight device.

The recently introduced method of ion separation by transversal ejection of unwanted species in electrostatic ion-beam traps and multi-reflection time-of-flight devices has been further studied in detail. As this separation is performed during the ion storage itself, there is no need for additional external devices such as ion gates or traps for either pre- or postselection of the ions of interest. The ejection of unwanted contaminant ions is performed by appropriate pulses of the potentials of deflector electrodes. These segmented ring electrodes are located off-center in the trap, i.e., between one of the two ion mirrors and the central drift tube, which also serves as a potential lift for capturing incoming ions and axially ejecting ions of interest after their selection. The various parameters affecting the selection effectivity and resolving power are illustrated with tin-cluster measurements, where isotopologue ion species provide mass differences down to a single atomic mass unit at ion masses of several hundred. Symmetric deflection voltages of only 10 V were found sufficient for the transversal ejection of ion species with as few as three deflection pulses. The duty cycle, i.e., the pulse duration with respect to the period of ion revolution, has been varied, resulting in resolving powers of up to several tens of thousands for this selection technique.

Isobar Separation in a Multiple-Reflection Time-of-Flight Mass Spectrometer by Mass-Selective Re-Trapping.

A novel method for (ultra-)high-resolution spatial mass separation in time-of-flight mass spectrometers is presented. Ions are injected into a time-of-flight analyzer from a radio frequency (rf) trap, dispersed in time-of-flight according to their mass-to-charge ratios and then re-trapped dynamically in the same rf trap. This re-trapping technique is highly mass-selective and after sufficiently long flight times can provide even isobaric separation. A theoretical treatment of the method is presented and the conditions for optimum performance of the method are derived. The method has been implemented in a multiple-reflection time-of-flight mass spectrometer and mass separation powers (FWHM) in excess of 70,000, and re-trapping efficiencies of up to 35% have been obtained for the protonated molecular ion of caffeine. The isobars glutamine and lysine (relative mass difference of 1/4000) have been separated after a flight time of 0.2ms only. Higher mass separation powers can be achieved using longer flight times. The method will have important applications, including isobar separation in nuclear physics and (ultra-)high-resolution precursor ion selection in multiple-stage tandem mass spectrometry. Graphical Abstract ᅟ.

Possibility of operating quadrupole mass filter at high resolution

A new possibility of improving the resolving power of quadrupole mass filters has been studied theoretically in this work. The results show that with the use of two AC excitations, in addition to the main RF supply, it is possible to modify the first stability diagram for mass filtering by creating a narrow and long band of stability along the X boundary near the tip of first stability region. These newly developed stability regions (the X-band) are similar to higher stability regions, and offer high mass resolution and fast mass separation features. This approach overcomes the many limitations of the normal operation of quadrupole analyzers, while retaining the advantages of using the first stability region. The new operation mode could achieve up to 10,000 mass resolving power with the ion residence time of only 100 RF cycles. In addition, the ion transmission efficiency with the use of the X-band is not only compromised, but is greater than in the normal operation mode. Furthermore, the new mode features one-dimensional mass filtering (in the X direction only) that is not sensitive to nonlinear field distortions, which are particularly problematic for quadrupole mass filters which built with circular rods. Faster mass separation has been confirmed in simulations and theoretical computations of the exponential increment of the trajectory instability. Due to the location of the X-band near the tip of the first stability region, the new operation mode can still have the benefits of traditional techniques (delayed DC ramp) for overcoming the negative effects of fringe fields and improving the ion transmission efficiency. The theoretical simulations show that the method of improving the performance of quadrupole mass filters does not require any modifications of mechanical structures, and only needs different and a little more sophisticated method of electric applications.

High-resolution mass separation by phase splitting and fast centering of ion motion in a Penning trap

A new technique for fast and effective mass separation of isobaric-contaminant ions is presented based on the continuous control of the phase and magnetron radius of ions orbiting in a Penning trap. Inspired by two techniques: Phase imaging ion cyclotron resonance (PI-ICR) (Eliseev et al., 2013) and magnetron-orbit manipulation (Mortensen et al., 2013), this method does not require ion cooling. First, isobaric species are separated in the radial plane by mass-selective excitations. A radial, position-selective dipole excitation pulse is then applied to re-center only the ions of interest. This paper presents the theoretical analysis of the process with detailed simulations. Results are compared to another buffer-gas free technique: SImultaneous Magnetron and resonant COnversion (SIMCO) excitation (Rosenbusch et al., 2012). Despite a lower maximum resolving power, the new process is twice as fast as SIMCO.

Experimental study of theβ-γandβ-nγdecay of the neutron-rich nucleus85Ga

The β-decay properties of neutron-rich 85Ga produced in proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Data consisted of β−γ and β−γ−γ coincidences were collected at the Low-energy Radioactive Ion Beam Spectroscopy Station after high-resolution on-line mass separation. For the first time, the excited states in the N=53 isotone 85Ge were established from β-delayed γ decay of 85Ga. The level scheme of the N=52 isotone 84Ge was improved and includes now 0+, 2+, (2)+, 4+, and (0)+ states populated in the β-delayed-neutron-γ decay of 85Ga. Advanced shell-model calculations were used to analyze experimental data on 85Ge and 84Ge.Received 12 August 2013DOI:https://doi.org/10.1103/PhysRevC.88.044330©2013 American Physical Society

β-γandβ-delayed neutron-γdecay of neutron-rich copper isotopes

The$\ensuremath{\beta}$-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of ${}^{238}$U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy methods. An improved decay scheme of $N=49$ ${}^{78}$Cu and the first observation of $N=50$ ${}^{79}$Cu $\ensuremath{\beta}$-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5${}^{\ensuremath{-}}$) are deduced for ${}^{78gs}$Cu. The $\ensuremath{\beta}$-delayed neutron branching ratios (${P}_{\ensuremath{\beta}n}$) for the ${}^{77}$Cu and ${}^{79}$Cu precursors are analyzed with the help of nuclear structure models.

Largeβ-Delayed Neutron Emission Probabilities in theNi78Region

The beta-delayed neutron branching ratios (P{betan}) for nuclei near doubly magic 78Ni have been directly measured using a new method combining high-resolution mass separation, reacceleration, and digital beta-gamma spectroscopy of 238U fission products. The P{betan} values for the very neutron-rich isotopes ;{76-78}Cu and 83Ga were found to be much higher than previously reported and predicted. Revised calculations of the betan process, accounting for new mass measurements and an inversion of the pi2p{3/2} and pi1f{5/2} orbitals, are in better agreement with these new experimental results.

The ion circus: A novel circular Paul trap to resolve isobaric contamination

The ion circus is a miniature storage ring formed by a segmented radiofrequency mass filter bent into a circle. The primary goal of this unique device is to perform high-resolution mass separation with small transmission loss since the resolving power is increased while the orbiting ions cool in the ring. Contrary to its linear brother, this circular Paul trap is designed to cool and mass separate the ions over a much longer flight path, thus requiring lower buffer gas pressure. Ions can be accumulated in the ring and extracted either in tangential or perpendicular directions. This way, the trap also serves as a versatile beam distribution device. Design principles are presented and the prototype instrument, under test in Orsay, is described.

Molecular Formula Analysis by an MS/MS/MS Technique To Expedite Dereplication of Natural Products

A facile and sensitive mass spectrometric method has been developed for the dereplication of natural products. The method provides information about the molecular formula and substructure of a precursor molecule and its fragments, which are invaluable aids in dereplication of natural products at their early stages of purification and characterization. Collision-induced MS/MS technique is used to fragment a precursor ion into several product ions, and individual product ions are selected and subjected to collision-induced MS/MS/MS analysis. This method enables the identification of the fragmentation pathway of a precursor molecule from its first-generation fragments (MS/MS), through to the nth generation product ions (MSn). It also allows for the identification of the corresponding neutral products released (neutral losses). Elements used in the molecular formula analysis include C, H, N, O, and S, as most natural products are constituted by these five elements. High-resolution mass separation and accurate mass measurements afforded the unique identification of molecular formula of small neutral products. Through sequential add-up of the molecular formulas of the small neutral products, the molecular formula of the precursor ion and its productions were uniquely determined. The molecular formula of the precursor molecule was then reversely used to identify or confirm the molecular formula of the neutral products and that of the productions. The molecular formula of the neutral fragments allowed for the identification of substructures, leading to a rapid and efficient characterization of precursor natural product. The method was applied to paclitaxel (C47H51NO14; 853 amu) to identify its molecular formula and its substructures, and to characterize its potential fragmentation pathways. The method was further validated by correctly identifying the molecular formula of minocycline (C23H27N3O7; 457 amu) and piperacillin (C23H27N5O7S; 517 amu).

Towards cooling of high-intensity ion beams

Buffer gas beam coolers may become excellent beam preparation devices for high-resolution mass separation. The small beam emittance provided makes efficient isobar resolution a realistic goal. In order to fulfill the needs of future facilities providing high-intensity beams of rare isotopes, it is desirable to increase the beam intensity limit of such devices from typically several tens of nanoamperes to microamperes. This requires the usage of high-voltage radiofrequencies in a low-pressure gas environment. A buffer gas beam cooler, dedicated to this purpose, is under development at the NSCL. The study of voltage breakdowns under such conditions and the design of an electrode system minimizing them is mandatory.

Isobar separation at FRS-ESR – a development towards pure isomeric stored beams

One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.

Future Aspects of Psychoneuroimmunology – Lymphocyte Peptides Reflecting Psychiatric Disorders Studied by Mass Spectrometry

We have investigated whether cytoplasmatic and nuclear extracts of human peripheral blood lymphocytes contain arginine vasopressin (AVP), of importance for memory functions, in samples from healthy controls and patients diagnosed as depressed. It is the first time as AVP, AVP-fragments and chemically modified AVP-forms have been demonstrated in lymphocyte/nuclear extracts. This was performed by an HPLC-purification step, followed by a second immunoprecipitation step before identification by mass spectrometry. We are developing new methods using a combination of high-resolution mass spectrometry and separation techniques such as capillary electrophoresis and nano liquid chromatography. We have named this methodological approach when studying endogenous peptides -Peptidomics.

The significance of monoisotopic and carbon-13 isobars for the identification of a 19-component dodecapeptide library by positive ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

Harnessing the ultra high resolution capabilities of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and positive ion electrospray, we have demonstrated the significance and utility of cumulative mass defect high resolution mass separation stable isotope distribution, exact mass measurement and elemental formula as a means of simultaneously identifying 19 components of the dodecapeptide library Ac-ANKISYQS[X]STE-NH(2). With an instrument resolution of 275 000 (average), isobaric multiplets attributed to monoisotopic and carbon-13 components of peptides: Ac approximately SLS approximately NH(2); Ac approximately SNS approximately NH(2); Ac approximately SOS approximately NH(2); Ac approximately SDS approximately NH(2); within the mass window of 1380-1385 Da, and Ac approximately SQS approximately NH(2); Ac approximately SKS approximately NH(2); Ac approximately SES approximately NH(2); Ac approximately SMS approximately NH(2), within the mass window 1395-1400 Da, were mass resolved, accurately mass measured and identified from the computed molecular formulas. This experimental procedure enabled the separation of monoisotopic and carbon-13 isobars yielding enhanced selectivity and specificity and serves to illustrate the significance of monoisotopic and carbon-13 isobars in final product analysis. Chromatographic separation (HPLC) was of limited utility except for monitoring the overall extent of reaction and apparent product distribution. Positive ion electrospray-FTICR-MS and fast atom bombardment (FAB) MS were used to assess final product quality and apparent component distribution.

High-resolution mass separator and 60 m beam transport line for the radioactive nuclear beam facility at INS

A high-resolution on-line isotope separator (ISOL) followed by a long beam transport line is under testing at INS, as a pilot radioactive beam facility for the E-arena of the Japanese Hadron Project. The ISOL has a unique feature in its high-voltage potential configuration; it has two separation stages and both are electrically insulated from the ground. This feature is effective to eliminate impurities as well as to perform high-resolution mass separation while keeping the injection beam velocity to the post accelerator constant. The design concept and present status of performance tests are reported.

Elliptical reflector low-pass energy filter for a liquid metal ion source cluster deposition system

We describe the design, construction, and implementation of a low-pass energy filter for use with a liquid metal ion source (LMIS) cluster deposition system. When combined with deceleration of cluster ions to a surface for landing, this filter provides bandpass energy selectivity for high resolution mass separation of clusters produced by the LMIS. We also present results of our initial testing, which shows the filter has an experimental relative energy resolution of less than 0.3%.