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A new multi-reflection time-of-flight mass spectrograph for nuclear mass measurements with high precision has been constructed at the SLOWRI facility at RIKEN-RIBF. We aim to couple this new device to a cryogenic gas cell operated at the BigRIPS facility of RIBF. It is part of the SLOWRI project for slowing down and stopping intense radioactive ion beams provided downstream of RIKEN’s superconducting ring cyclotron accelerator. In particular, this device is dedicated to be located at the end of the BigRIPS beam line to access ions that are presently guided to beam dumps during in-beam experiments. In this article the apparatus is described in detail.

Achieving the highest possible mass resolving power in a multi-reflection time-of-flight mass spectrometer requires very high-stability power supplies. To this end, we have developed a programmable high-voltage power supply that can achieve long-term stability on the order of parts-per-million. Herein we present the design of the stable high-voltage system and bench-top stability measurements up to 1~kV; the stabilization technique can, in principle, be applied up to 15~kV or more.. We demonstrate that in the $\le$1~Hz band the output stability is on the level of 1~part per million (ppm) during one hour, with only slightly more output variation across 3 days. We further demonstrate that the output is largely free of noise in the 1~Hz -- 200~Hz band. We also demonstrate settling to the ppm level within one minute following a 100~V step transition. Finally, we demonstrate that when these power supplies are used to bias the electrodes of a multi-reflection time-of-flight mass spectrograph the measured time-of-flight is stable on the ppm-level for at least one hour., Comment: 10 pages, 12 figures, Report of electronics development

We introduce a new concomitant referencing mode for operating a multi-reflection time-of-flight mass spectrograph (MRTOF-MS), wherein the reference and analyte ions are interleaved on a cycle by cycle bases. Using this mode, we demonstrate an improved technique for performing wide bandwidth mass measurements via MRTOF-MS. This new technique offers a simplified analysis and high-accuracy., 8 pages, 6 figures, follow-up for DOI:10.1016/j.ijms.2013.11.005

Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a 48Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.

In applied forms of time-of-flight mass spectrometry utilizing ion storage devices prior to an analysis device, a non instantaneous electric ejection pulse applied in the region of ion storage is used to accelerate ions into the time-of-flight analyzer. The calculated mass value of the ions from the time-of-flight is dependent on the duration of the field transition up to full strength. For novel applications dedicated to precision measurements, such as multi-reflection time-of-flight mass spectrometry of short-lived isotopes, the goal is to continuously decrease the measurement uncertainty while providing a mass accuracy on the same order. Even though dynamic-field models for time-of-flight mass spectrometry have been considered in the past for technological advances, it is important to study the accuracy of the measured mass in this context. Using a simplified linear model for the field transition, we provide a basic investigation of the scenario, and discuss the deviation from the classical "mass-over-charge" dependency of the ions' time-of-flight, which becomes violated. The emerging mass discrepancy depends on the distance between the mass of the ion used for calibration and that of the ion of interest and, in extreme cases, can increase to about one percent for systems with short times-of-flight. However, for typical conditions in single-reference multi-reflection time-of-flight mass spectrometry, mass deviations caused by this effect typically remain below the 1 ppm level. If a mass calibration using two or more ion species is possible during the measurement, the effect becomes negligible for appropriate choices of reference masses., 14 pages, 9 figures

The masses of ^{246}Es, ^{251}Fm, and the transfermium nuclei ^{249-252}Md and ^{254}No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed N=152 neutron shell closure, have been directly measured using a multireflection time-of-flight mass spectrograph. The masses of ^{246}Es and ^{249,250,252}Md were measured for the first time. Using the masses of ^{249,250}Md as anchor points for α decay chains, the masses of heavier nuclei, up to ^{261}Bh and ^{266}Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter δ_{2n} derived from three isotopic masses was updated with the new masses and corroborates the existence of the deformed N=152 neutron shell closure for Md and Lr.

The masses of the exotic isotopes $^{210\ensuremath{-}214}\mathrm{Ac}$ and $^{210\ensuremath{-}214}\mathrm{Ra}$ have been measured with a multireflection time-of-flight mass spectrograph. These isotopes were obtained in flight as fusion-evaporation products behind the gas-filled recoil ion separator GARIS-II at RIKEN. The new direct mass measurements serve as an independent and direct benchmark for existing $\ensuremath{\alpha}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy data in this mass region. Further, new mass anchor points are set for U and Np nuclei close to the $N=126$ shell closure for a future benchmark of the $Z=92$ subshell for neutron-deficient heavy isotopes. Our mass results are in general in good agreement with the previously indirectly determined mass values. Together with the measurement data, reasons for possible mass ambiguities from decay-data links between ground states are discussed.

Pharmaceutical residues on solid surfaces were determined in air at ambient pressure using ion mobility spectrometry (IMS) with electrospray ionization laser desorption (ELDI) methods. Substances were desorbed from surfaces with a pulsed Nd-YAG laser at 266 nm and ionized in an electrospray ion source. Ions derived from substances by ELDI were measured using ion mobility spectrometry. Substances with strong proton affinities produced ions which were mass-identified as MH+ and produced mobility spectra with a single, intense, product ion peak. Ablation rates were determined as 0.038 pg/s and sampling at a fixed location led to decreases in product ion intensity with complete removal of residue on the surface. A dependence of intensity on the substrate for five pharmaceuticals was observed and could be associated with substrate porosity. The area of sampling was 12 mm2 and linear resolution of a line of pharmaceuticals over 20 mm length demonstrated a capability to image residue by ELDI IMS.

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $\alpha$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, $^{204}$Fr-$^{204}$Rn-$^{204}$At-$^{204}$Po, $^{205}$Fr- $^{205}$Rn-$^{205}$At-$^{205}$Po-$^{205}$Bi, and $^{206}$Fr-$^{206}$Rn-$^{206}$At, were observed. Precision atomic mass values were determined for $^{204-206}$Fr, $^{204,205}$Rn, and $^{204,205}$At. Identifications of $^{205}$Bi, $^{204,205}$Po, $^{206}$Rn, and $^{206}$At were made with N$\leq$10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions., 多反射時間飛行質量分析装置を理化学研究所設置の気体充填型反跳分離装置-II型(GARIS-II)と連結したガスセルに配置し、$\alpha$崩壊連鎖を伴う重原子核の質量の直接測定を実施した。融合-蒸発反応で生成された原子核をGARIS-IIを用いて分離し、ヘリウムガスセルで止めて目的の原子核を捕集した。本実験で$^{204}$Fr-$^{204}$Rn-$^{204}$At-$^{204}$Po, $^{205}$Fr-$^{205}$Rn-$^{205}$At-$^{205}$Po-$^{205}$Bi及び$^{206}$Fr-$^{206}$Rn-$^{206}$Atの3つの同重体鎖の時間飛行スペクトルが観測された。その結果、$^{204-206}$Fr, $^{204,205}$Rn、そして$^{204,205}$Atの原子質量値が精密に決定された、今回の解析において、$^{205}$Bi, $^{204,205}$Po, $^{206}$Rn、そして$^{206}$Atの同定は10個以下という少量のイオン数でなされた。この成果は 次のステップとして実施する予定である(生成量が極少量の)超重元素イオンの質量分析につながる成果となる。

High-precision mass measurements of $^{63}$Cu, $^{64-66}$Zn, $^{65}$Ga, $^{65-67}$Ge, $^{67}$As, $^{78,81}$Br, $^{80}$Rb, and $^{79}$Sr were performed utilizing a multireflection time-of-flight mass spectrograph combined with the gas-filled recoil ion separator GARIS-II. In the case of $^{65}$Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of $\delta m / m = 3.5\times10^{-8}$, was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation. For $^{67}$Ge and $^{81}$Br, where masses were previously deduced through indirect measurements, discrepancies with literature values were found. The feasibility of using this device for mass measurements of nuclides more neutron-deficient side, which have significant impact on the $rp$-process pathway, is discussed., Comment: 15 pages, 6 figures, 1 table

A multi-reflection time-of-flight mass spectrograph (MRTOF-MS) has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei with half-lives down to ⩽10 ms. Such measurements are of particular interest for r-process nuclei and trans-Uranium nuclei. We provide a detailed description of the mechanical construction and electronics implementation of an MRTOF-MS at RIKEN. The resolving power is investigated by numerical simulation and these simulations are compared to experimental observations to understand the effects of voltage and thermal instabilities. The limits of precision and accuracy are investigated using offline ion sources, and the effects of non-isobaric contaminants are reported.

RATIONALE Mixtures of ions produced in sources at atmospheric pressure, including chemical ionization (APCI) and electrospray ionization (ESI) can be simplified at or near ambient pressure using ion mobility based filters. METHODS A low-mobility-pass filter (LMPF) based on a simple mechanical design and simple electronic control was designed, modeled and tested with vapors of 2-hexadecanone in an APCI source and with spray of peptide solutions in an ESI source. The LMPF geometry was planar and small (4 mm wide × 13 mm long) and electric control was through a symmetric waveform in low kHz with amplitude between 0 and 10 V. RESULTS Computational models established idealized performance for transmission efficiency of ions of several reduced mobility coefficients over the range of amplitudes and were matched by computed values from ion abundances in mass spectra. The filter exhibited a broad response function, equivalent to a Bode Plot in electronic filters, suggesting that ion filtering could be done in blocks ~50 m/z units wide. CONCLUSIONS The benefit of this concept is that discrimination against ions of high mobility is controlled by only a single parameter: waveform amplitude at fixed frequency. The effective removal of high mobility ions, those of low mass-to-charge, can be beneficial for applications with ion-trap-based mass spectrometers to remove excessive levels of solvent or matrix ions. Copyright © 2013 John Wiley & Sons, Ltd.

For trans-uranium elements, stable atomic isobars do not exist. In order to provide isobaric reference ions for the mass measurement of trans-uranium elements, an electrospray ion source (ESI) was combined with an rf-carpet to collect molecular ions efficiently. The rf-carpet allows for simplification of the pumping system to transport ions from the ESI to a precision mass analyzer. Molecular ions appropriate for isobaric references of trans-uranium elements were extracted from the rf-carpet and analyzed by a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) with a resolving power of R m ≳ 100, 000.

A compact isobar spectrometer and separator, based on the multi-pass-time-of-flight (MTOF) principle, is being developed by the University radioactive ion beam (UNIRIB) Consortium. It consists of two coaxial, grid-free electrostatic mirrors with auxiliary injection, focusing and extraction elements. Ions of different mass are reflected multiple times between the mirrors and separated longitudinally. Using an electron beam impact ion source and N2 as a sample gas, a mass resolving power of 110,000 (FWHM) has been achieved. In the near future, MTOF will be coupled to the on-line isotope separator UNISOR (University Isotope Separator – Oak Ridge) at Holifield radioactive ion beam facility using electrostatic beam deceleration, a radiofrequency beam cooler and a fast buncher. It will serve as a high resolution mass separator with a Bradbury–Nielsen gate, providing isotopically pure samples of exotic species in the 100Sn region and later, of neutron rich nuclei, for use in decay studies.

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission's main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula. To accomplish the very demanding objectives through all the different phases of the comet's activity, ROSINA has unprecedented capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N2 and 13C from 12CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature. ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor. To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns in our electron bombardment ion sources.

A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being build as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of de electric fields and inhomogeneous rf fields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV 8Li ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. Recently our first spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic ions of 10Be and 7Be from the RIPS were trapped and laser cooled in a linear rf trap and the specific mass shifts of these isotopes were measured for the first time.

Recently, much progress has been made with stored exotic nuclei at relativistic velocities ( v c = 0.7 ) . Fragments of 208Pb and 209Bi projectiles and fission products from 238U ions were produced, separated in flight with the fragment separator FRS, and injected into the storage-cooler ring ESR for precision measurements. 114 new masses of neutron-deficient isotopes in the lead region have been measured with time-resolved Schottky Mass Spectrometry (SMS). A new isospin dependence of the pairing energy was observed due to the improved mass accuracy of typically 1.5×10-7 (30 keV). New masses of short-lived neutron-rich fission fragments have been obtained with Isochronous Mass Spectrometry (IMS). An innovative field of spectroscopy has been opened up with lifetime measurements of stored bare and few-electron fragments after applying both stochastic and electron cooling.

In order to determine nuclear binding energies of short-lived nuclei we have developed a multi-pass time-of-flight mass spectrometer in which ions are repeatedly reflected between two coaxially arranged electrostatic ion mirrors. These ions are passed up to several hundred times between the ion mirrors. Within this system the overall ion flight time can be several milliseconds and the overall flight distance more than 100 m. There are no intensity losses in the grid-free ion mirrors and the transmission is limited only by angle scattering of the ions by residual gas atoms. The achieved mass resolving power exceeded m=Dm � 40 000. 2004 Elsevier B.V. All rights reserved.

A large area on the mass surface of neutron-deficient nuclides (36≤Z≤85) was measured with time-resolved Schottky mass spectrometry at the FRS-ESR facilities. The masses of 114 nuclides were obtained for the first time from which 43 were determined via known decay energies. The improved mass accuracy of 30 keV allowed to study the isospin dependence of nuclear pairing, to precisely locate the one-proton dripline for odd-Z isotopes from Tb to Pa and to make crucial tests of the predictive powers of modern mass models.

The half-lives of isomeric states of fully ionized 144Tb, 149Dy and 151Er have been measured. These nuclides were produced via fragmentation of about 900 MeV/u 209Bi projectiles, separated in flight with the fragment separator (FRS) and stored in the cooler ring (ESR). The decay times of the cooled fragments have been measured with time-resolved Schottky spectrometry. We observed for the first time drastic increases of the half-lives of bare isomers by factors of up to 30 compared to their neutral counterparts. This is due to the exclusion of the strong internal conversion and electron-capture channels in the radioactive decay of these bare nuclei. The experimental results are in good agreement with theoretical calculations.

Energy-isochronous time-of-flight mass spectrometers can achieve high mass resolving powers by using the same flight pass repeatedly and thus obtaining long overall flight distances. If such systems must achieve high transmission in addition to their isochronicity, they must be designed such that their lateral phase-space acceptance is larger than the corresponding emittance of the injected ion beam. It furthermore is advantageous to construct the system from matched unit cells, a technique also used in the design of accelerator storage rings. One such time-of-flight mass spectrometer has been built as a system in which ions are repeatedly reflected between two grid-free ion mirrors whose optic axes coincide. For a 0.4 m long system, through which ions were reflected 101 times, mass resolving powers of m /Δ m ≥18,000 have been achieved with a transmission of about 40%.

A gas-filled radio-frequency quadrupole has been developed, which acts as an interface between a time-of-flight mass spectrometer and an atmospheric-pressure ion source or a gas-filled ion beam stopping cell. It delivers cooled continuous or bunched beams to the mass analyzer. The radiofrequency quadrupole has been characterized and the longitudinal energy distributions, bunching efficiencies and beam losses as a function of storage time, and the duty cycle improvement have been measured. Using the bunch mode, the mass-resolving power of the time-of-flight mass spectrometer could be increased by a factor of about two and now amounts to 24 000 (full width at half maximum).

We present results from two methods of direct mass measurements of relativistic exotic nuclei stored in the storage ring ESR. Schottky Mass Spectrometry (SMS) with electron-cooled ions is well suited for long-lived nuclei ( T 1/2 ⩾10 s), and the Isochronous mass measurements (IMS) for hot fragments ( T 1/2 ⩾1 μs). In addition, SMS provides information on nuclear lifetime for bare and highly ionized atoms.

The masses of 64 short-lived neutron-deficient nuclides covering the element range from tungsten to uranium have been obtained for the first time. They have been evaluated by combining directly measured masses from Schottky mass spectrometry with linked experimental Q-values in α-decay chains. Based on these new mass data we have determined the one-proton and two-proton drip-lines as well as the size of the “littoral shallow” of the sea of instability. No evidence of a Thomas–Ehrman shift has been found in the region of the investigated heavy nuclides. A peculiar behavior of two-proton separation energies has been observed in the lead region. The predictive power of various mass models is investigated.

Low energy ions can be stored in “rings” of electrostatic sector fields or in systems of electrostatic mirrors between which the ions are reflected back and forth repeatedly. Because of the long flight path in such systems they very well can be used as precision time-of-flight mass spectrometers. This statement is trivial for monoenergetic ions but also holds for polyenergetic ions if the ion–optical system is designed such that it guides more energetic ions on appropriate detours that cause the overall ion-travel times to become energy independent. Since the number of reflections between the mirrors can be varied by changing the timing of the voltage pulses on the mirrors, either a long well resolved mass spectrum can be recorded or only a section of such a mass spectrum for which then the mass resolving power is increased proportional to the number of reflections.

A concept of an “ideal” orthogonal-injection time-of-flight (O-TOF) mass spectrometer is proposed and a new high-resolution O-TOF mass spectrometer with an electrospray ion source and a molecule-ion reactor is described. The instrument design was optimized for high resolution and sensitivity using the concept of an ideal O-TOF mass spectrometer. A mass resolving power of about 20,000 (full width at half maximum) and a mass measurement accuracy in the 10 ppm range is demonstrated.

Short-lived exotic nuclei can be produced and separated with the high-energy secondary nuclear beam facility FRS at GSI. These nuclides can be injected and stored in the storage ring ESR. The lower lifetime limit of the presently existing methods for mass measurements on these nuclides at the ESR is about a few seconds. We have developed and investigated an isochronous operational mode of the ESR, that makes mass measurements of nuclides with lifetimes down to a few ls feasible. It has been commissioned in experiments using long-lived nuclides with known masses. A mass resolving power of about 150 000 has been achieved in a "rst pilot experiment. A suitable detector system has been implemented and commissioned at the ESR that allows measurements of the revolution period of single particles within a few turns in the ESR. ( 2000 Elsevier Science B.V. All rights reserved.

Two experimental methods of measuring masses of exotic nuclei in the storage ring ESR are presented. Bismuth and nickel fragments were produced via projectile fragmentation, separated and investigated with the combination of the fragment separator FRS and the ESR: (i) Direct mass measurements of relativistic projectile fragments were performed using Schottky mass spectrometry (SMS), i.e., exotic nuclei were stored and cooled in the ESR. Applying electron cooling, the relative velocity spread of circulating low intensity beams can be reduced below 10−6. Under this condition a mass resolving power of up to m/Δm=6.5·105 (FWHM) was achieved in a recent measurement. Previously unknown masses of more than 100 neutron-deficient isotopes have been measured in the range of 60≤Z≤84. Using known Q α values the area of known masses could be extended to more exotic nuclei and to higher proton numbers. The results are compared with mass models and extrapolations of experimental values. In a second experiment with 209Bi projectiles the area of the measured masses was extended to lower proton numbers. Due to various improvements at the ESR the precision of the measurements could be raised. (ii) Exotic nuclei with half-lives shorter than the time needed for SMS (present limit: T 1/2 ≈ 5 sec) can be investigated by time-of-flight measurements whereby the ESR is operated in the isochronous mode. This novel experimental technique has been successfully applied in first measurements with nickel and neon fragments where a mass resolving power of m/Δm=1.5·105 (FWHM) was achieved.

A compact orthogonal ion source has been developed for the gas analysis in time-of-flight mass spectrometers with the goal to use such a system for the investigation of cometary gases. An extraordinary mass resolving power of m/Dm $ 10 000 and low detection limits have been obtained in a 1.3 m long instrument. (Int J Mass Spectrom 185/186/187 (1999) 221‐226) © 1999 Elsevier Science B.V.

Collisional focusing of low mass ions of 1–40 eV is investigated in a rf-only quadrupole. The final ion intensities and energies are monitored by an orthogonal-extracting time-of-flight mass spectrometer. It was found that in this energy range Na+ and K+ ions can be cooled and focused as well as Cs+ ions if the residual gas pressure in this “quadrupole beam cooler” is high enough that each ion undergoes several collisions.

Ion detection with good signal-to-noise ratio is required in TOF mass spectrometry for measurements over a wide range of masses. To reach high mass resolving powers it is also necessary to have detectors with good timing characteristics. We show some of our concepts to reach a detection system with such properties.

Recent results of mass measurements of exotic heavy nuclei using Schottky mass spectrometry are reported. The investigated nuclei were produced and separated by the fragment separator FRS, injected, stored and cooled in the experimental storage ring ESR. Their masses were determined from the frequency analysis of the beam noise. In the present experiment the masses of more than 150 proton-rich nuclei in the mass region A ∼- 200 have been determined for the first time. Representative results are given for proton-separation energies and shell corrections. For some elements the proton drip line can be determined.

Overall beam distortions in multistage static mass analyzers are compared as they arise from defects in manufacturing of different types of elements. Possibilities of a correction are shown to be limited by second-order effects.

A molecule ion reactor (MIR), i.e. a gas filled radio-frequency only quadrupole with a longitudinal electrical field (RFQLEF), is used as an atmospheric pressure ionization interface for an orthogonal time-of-flight mass spectrometer (O-TOFMS). A new phenomenon of selective ion 'heating' in a MIR near Mathieu's instability threshold was found and confirmed by computer simulation. The 'heating' in collisions with buffer gas molecules leads to ion decomposition. In the case of multicharged ions, fragments with an m/z value higher than that of the parent ion have a stable motion and can be analysed by an O-TOFMS. Fragmentation of bradykinin and beta-endorphin molecular ions having a selected charge state is demonstrated. The spectra show clear 'ladder' structure. The phenomenon may be used as an alternative to tandem mass spectrometry (MS/MS) for molecule structure analysis.

High-precision mass measurements of proton-rich isotopes in the range of 60{le}Z{le}84 were performed using the novel technique of Schottky spectrometry. Projectile fragments produced by {sup 209}Bi ions at 930{ital A} MeV were separated with the magnetic spectrometer FRS and stored and cooled in the experimental storage ring (ESR). A typical mass resolving power of 350000 and a precision of 100keV were achieved in the region A{approx}200 . Masses of members of {alpha} chains linked by precise Q{sub {alpha}} values but not yet connected to the known masses were determined. In this way it is concluded that {sup 201}Fr and {sup 197}At are proton unbound. {copyright} {ital 1997} {ital The American Physical Society}

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.

A new type of electron impact storage ion source has been designed for time-of-flight mass spectrometers with high mass resolving power and high sensitivity. We have worked out a set of computer programs to compute electrostatic potentials and ion trajectories. The dispersion of the flight time is about 2–3 nanoseconds, the most valuable result for the ion source. Both two-dimensional and quasi-three-dimensional maps for the configuration of the electrodes, equipotential lines and ion trajectories have been plotted. It is to be expected that the present research may be useful in designing high-performance ion sources for time-of-flight mass spectrometers.

In order to determine binding energies of short-lived nuclei we have developed a time-of-flight mass spectrometer of high mass resolving power m/Δm. This spectrometer achieves a very long ion flight path by repeatedly reflecting ions between two electrostatic ion mirrors. The nuclei to be investigated are produced in heavy ion fragmentations and separated in-flight by a fragment separator. These energetic ions are thermalized in a catcher gas cell injected into an RF ion-guide and then into an ion trap to be cooled, bunched and entered into the time-of-flight spectrometer. This technique should allow to determine the masses of short-lived nuclei with high efficiency. Using stable ions, the so far achieved mass resolving power m/Δm exceeded 65,000.

A multi-reflection time-of-flight mass spectrograph, competitive with Penning trap mass spectrometers, has been built at RIKEN. We have performed a first online mass measurement, using 8Li+ (T1/2 = 838 ms). A new analysis method has been realized, with which, using only 12C+ references, the mass excess of 8Li was accurately determined to be 20947.6(15)(34) keV (dm/m = 6.6 x 10-7). The speed, precision and accuracy of this first online measurement exemplifies the potential for using this new type of mass spectrograph for precision measurements of short-lived nuclei., Comment: 6 pages, 4 figures

We characterize the mass bandwidth of the a multi-reflection time-of-flight mass spectrograph, showing both the functional and useful mass bandwidth. We then demonstrate the use of a multi-reflection time-of-flight mass spectrograph to perform mass measurements in mass bands much wider than the mass bandwidth., Comment: 8 pages, 9 figures

A radiofrequency quadrupole ion trap system for use with a multi-reflection time-of-flight mass spectrograph (MRTOF) for short-lived nuclei has been developed. The trap system consists of two different parts, an asymmetric taper trap and a flat trap. The ions are cooled to a sufficient small bunch for precise mass measurement with MRTOF in only 2 ms cooling time in the flat trap, then orthogonally ejected to the MRTOF for mass analysis. A trapping efficiency of ~27% for 23Na+ and ~5.1% for 7Li+ has been achieved., Comment: 6 pages

The development of methods for analysis of triazines and their hydroxy metabolites in humic soil samples with combined chromatographic and mass spetrometric techniques is described. A two-way approach was used for separating interfering humic substances and for performing structural elucidation of the herbicide traces. Humic soil samples were extracted by supercritical fluid extraction and analysed both by HPLC—particle beam MS and a new MS—MS method. The new MS—MS unit is of the tandem-sector field-time-of-flight-MS type.

We plan to measure masses of exotic nuclei far from the valley of β-stability using the Experimental Storage Ring (ESR) at GSI, Darmstadt, as a time-of-flight (TOF), multi-turn mass spectrometer. For this purpose the ring must be tuned to an isochronous mode, so that the flight time per turn of an ion depends only on its mass-to-charge ratio and not on its velocity spread. For these measurements the timing detector is planned to be placed directly in the ESR to record each circulating ion.

In this paper, we present a novel non-Fourier transform multiplex means for sampling and frequency analyzing a signal consisting of a sum of exponentially damped sinusoids of different frequency. The method is illustrated by a hypothetical toroidal or linear reflective time-or-flight mass spectrometer in which ionic mass is related to the repetition frequency of pulse-injected analyte ions. Time-domain data is generated from the voltage recorded by each of two detector plates placed 180 o apart at opposite ends of the detector system, where it is advantageous to record successive maximal voltages from the two detectors alternately as positive and negative data vs time

The experimental set-up for relaxation spectroscopy with a newly constructed time-of-flight mass spectrometer (ToF-MS) is described. The response to single gas pulses is measured with the ToF-MS, which is equipped with a special storing ion source and an electrostatic ion reflector. The gas pulses, with rise and fall times of less than 2 ms, are generated by a solenoid valve in a differentially pumped system. Conventional ToF instruments with ionization by electron pulses detect only a small fraction of the incoming molecules. Therefore our instrument with the storing (integrating) ion source is more sensitive, typically by a factor of 1000. Pulses of deuterated acetic acid (AcOD) with a length of 20 ms are used to produce exposures of 1/1000 monolayer (ML) per pulse on a polycrystalline Pd foil. On clean Pd the formation of CO2 is observed. An activation energy of 0.78 eV and a preexponential factor of 3 × 108 s−1 are derived from the transients in the temperature range between 550 and 650 K. After a total dose of 1 ML of AcOD the CO2 signal ceases and the AcOD signal emerges, yielding an activation energy of 0.44 eV and a pre-exponential factor of 9 × 108 s−1. It is shown that even exposure to small doses of AcOD decreases the efficiency of CO2 formation. After a dose of 2 ML the CO2 formation is completely suppressed. To determine the energy and the pre-exponential factor for the investigated surface reaction, an exposure dose of less than 1/100 ML is sufficient.

RIKEN’s new RI-Beam Factory (RIBF) will provide unprecedented access to neutron-rich nuclei of importance to r-process nucleosynthesis. We are constructing an advanced multi-reflection time-of-flight mass spectrograph to perform precision mass measurements of these nuclei. We discuss the device and compare its performance to that of the well-known Penning trap mass spectrometer.

The time-of-flight mass spectrometer described here has been designed for ions with angle and energy spreads as produced in a real ion source. It performs both transverse and longitudinal focusing. These focusing properties are achieved simultaneously by the inhomogeneous electrostatic field of a rotationally symmetric grid-free ion reflector with conically shaped entrance electrodes. When used in combination with a newly developed longitudinally focusing electron impact ion source, high sensitivity and high mass resolving power are obtained.

Using grid-free ion mirrors of high optical quality one can construct laterally and longitudinally achromatic focusing time-of-flight mass spectrometers. Using several such systems in series the overall flight distance as well as the achievable mass resolving power can be considerably increased.

CH3CH2OD (deuterated ethanol) pulses (5 × 10−4 ML, 20 ms) are offered to polycrystalline ZnO under ultra high vacuum conditions. The reaction products are monitored with a rate of 1000 spectra per second by a time of flight mass spectrometer. D2O and CO2, both including lattice oxygen, are observed in desorption. The creation of surface oxygen vacancies destabilizes zinc atoms nearby which appear also in desorption. The rate constant ka (inverse relaxation time) increases below 900 K. Above this temperature ka decreases. The decrease may be due to bulk oxygen diffusing to the surface and refilling the surface oxygen vacancies.