High-resolution Magnetic Spectrometer Research Articles

Overview of the neutron diagnostic systems for the SPARC tokamak.

Neutron measurement is the primary tool in the SPARC tokamak for fusion power (Pfus) monitoring, research on the physics of burning plasmas, validation of the neutronics simulation workflows, and providing feedback for machine protection. A demanding target uncertainty (10% for Pfus) and coverage of a wide dynamic range (>8 orders of magnitude going up to 5 × 1019 n/s), coupled with a fast-track timeline for design and deployment, make the development of the SPARC neutron diagnostics challenging. Four subsystems are under design that exploit the high flux of direct DT and DD plasma neutrons emanating from a shielded opening in a midplane diagnostic port. The systems comprise a set of ∼15 flux monitors, mainly ionization chambers and proportional counters for measurement of the neutron yield rate, two independent foil activation systems for measurement of the neutron fluence, a spectrometric radial neutron camera for poloidal profiling of the plasma emissivity, and a high-resolution magnetic proton recoil spectrometer for measurement of the core neutron spectrum. Together, the four systems ensure redundancy of sensors and methods and aim to provide high resolutions of time (10ms), space (∼7cm), and energy (<2% at 14MeV). This paper presents the broader objectives behind the preliminary design of the SPARC neutron diagnostics and discusses the ongoing studies on neutronics, detector comparisons, prototyping, and integration with the unique infrastructure of SPARC. Engineering details of the four subsystems and the concepts for in situ neutron calibration are also highlighted.

Design and simulated performance of a high-resolution magnetic proton recoil spectrometer for deuterium–tritium neutrons

Neutron emission energy and time spectra of deuterium–tritium plasma contain abundant information about the fusion yield, ion temperature, and nuclear burn history. Magnetic recoil spectrometers have been employed in measuring time-integrated energy spectra in inertial confinement fusion (ICF) experiments. As the fusion yield increases, time-resolved neutron diagnostics is urgently desired for understanding complex fusion physics. Herein, we design a compact magnetic proton recoil (MPR) spectrometer based on a 90 degree permanent magnet. The entrance and exit of the magnet are second-order shapes to eliminate two major second-order aberrations. The energy resolution and time resolution for 14MeV neutrons achieve 97keV and 1.6ns, respectively, under the detection efficiency of 7.4×10−8cm2. A quadratic relation is found between detection efficiency and energy resolution when configurations are optimal. Monte Carlo simulations are accomplished to study the performance in measuring time-integrated energy spectra, emission time spectra, and time-resolved energy spectra, demonstrating the potential of high-resolution MPR spectrometers in future high-yield ICF experiments.

The structure of low-lying 1− states in 90,94Zr from (α,α′γ) and (p,p′γ) reactions

The low-lying dipole strength was investigated in 90,94 Zr via the (p,p′γ) reaction at 80 MeV and via the (α,α′γ) reaction at 130 MeV. These experiments were performed at the Research Center for Nuclear Physics (Osaka University) and made combined use of the high-resolution magnetic spectrometer Grand Raiden and the CAGRA HPGe gamma array. The comparison of our results with existing (γ,γ′) reaction data shows differences in the excitation patterns. In the present experimental conditions, in fact, both α and p probes are exciting the investigated 1− states mainly through the short-range nuclear force, expected to favour the population of surface excitations. Distorted Wave Born Approximation (DWBA) calculations were made using form factors built assuming specific transition densities, characterized by a strong neutron component at the nuclear surface and based on Random Phase Approximation (RPA). A combined analysis of the (α,α′γ) and (p,p′γ) data was performed to investigate the isoscalar character of the 1− states in 90,94Zr. Although an overall general consistency was obtained in the studied energy intervals, not all (p,p′γ) cross sections were well reproduced using the isoscalar strength deduced from (α,α′γ) data. This might suggest that the mixing of isoscalar and isovector components and the degree of collectivity are not the same for all the 1− states studied.

Theoretical study of isotope production in the peripheral heavy-ion collision 136Xe + Pb at 1 GeV/nucleon

We have studied the fragment yields emitted from the fragmentation of excited projectile nuclei in peripheral collisions of X136e+Pb at 1 GeV/nucleon, and measured with the high-resolution magnetic spectrometer, the Fragment Separator (FRS) of GSI. The mass, charge and isotope distributions of nuclear fragments formed in the reactions were calculated within a statistical ensemble approach and compared to the experimental data. The ensemble of excited projectilelike source nuclei were created in the framework of a previous analysis of similar reactions performed at 600 MeV/nucleon (ALADIN-experiments, GSI). In addition, the ensemble of the low-excited compound nuclei is involved in the analysis. The overall agreement between theory and experiment was very satisfactory in reproducing the experimental data of isotope yields measured in the heavy-ion collisions. It is confirmed that a broad range of elements can be reproduced within a universal statistical disintegration of the excited projectile residues.

New data acquisition system of the Lintott magnetic spectrometer at the S-DALINAC

A new data acquisition system for the high-resolution magnetic spectrometer Lintott at the superconducting Darmstadt electron linear accelerator S-DALINAC was developed. It allows inclusive and coincidence electron scattering experiments with event rates up to 10 kHz.

Speciation and determination of iron in aqueous solution and river water by high-resolution electrospray ionization mass spectrometry

Characterization and determination of Fe2+ co-existing with Fe3+ using a simple method of electrospray ionization mass spectrometry (ESI-MS) is employed. We attempted to characterize Fe2+ species in aqueous solution in combination with various inorganic salts of iron, such as chloride, sulfate, and cyanide salts, using two kinds of detection systems (a quadrupole mass spectrometer and a high-resolution magnetic mass spectrometer), to establish the stability of the complexes formed. The study further extended to the determination of Fe2+ concentration, and we expect that ESI-MS will be a new method to determine Fe2+. Among the inorganic salts studied, 1,10-Phenanthroline forms stable tetrahedral complexes with Fe2+ in the gas phase of ESI-MS which is observed in a high-m/z region and are well separated. The method is extended for determining Fe2+ concentration in natural river water samples by measuring the peak intensity of [Fe(phen)2]2+ (m/z 208) and obtaining a calibration curve (R2 = 0.9992) of the peak intensity determined by HR-ESI-MS. The Fe2+ concentrations in Tama River samples were obtained by the standard addition method (Fe2+ 0.23 μmol/L, R2 = 0.9998), and total concentration of iron in Tama River sample was 0.59 μmol/L (ICP-MS), thus about 40% of iron is present as Fe2+.

Reexamination of isoscalar giant resonances inC12andNb93throughLi6scattering

Inelastic ${}^{6}$Li scattering at 100 MeV/u on ${}^{12}$C and ${}^{93}$Nb have been measured with the high-resolution magnetic spectrometer Grand Raiden. The magnetic-rigidity settings of the spectrometer covered excitation energies from 10 to 40 MeV and scattering angles in the range $0^\circ < \theta_{\text{lab.}}< 2^\circ$. The isoscalar giant monopole resonance was selectively excited in the present data. Measurements free of instrumental background and the very favorable resonance-to-continuum ratio of ${}^{6}$Li scattering allowed for precise determination of the $E0$ strengths in ${}^{12}$C and ${}^{93}$Nb. It was found that the monopole strength in ${}^{12}$C exhausts $52 \pm 3^\text{(stat.)} \pm 8 ^\text{(sys.)}$\% of the energy-weighted sum rule (EWSR), which is considerably higher than results from previous $\alpha$-scattering experiments. The monopole strength in ${}^{93}$Nb exhausts $92 \pm 4^\text{(stat.)} \pm 10 ^\text{(sys.)}$\% of the EWSR, and it is consistent with measurements of nuclei with mass number of $A\approx90$. Such comparison indicates that the isoscalar giant monopole resonance distributions in these nuclei are very similar, and no influence due to nuclear structure was observed.

Neutron transfer in reaction 18O + 181Ta with formation of neutron-rich oxygen isotopes

Differential cross sections for the formation of oxygen isotopes in the reaction 18O + 181Ta have been measured at projectile nucleus energy 10 A⋅MeV on the high-resolution magnetic spectrometer MAVR. Theoretical analysis of product yields has been performed in the finite-range distorted-wave Born approximation formalism using the FRESCO code under the assumption of sequential neutron transfer mechanism. The results of calculations are in good agreement with experimental data.

Differential Production Cross Sections for Isotopes of Light Nuclei in the $$\boldsymbol{{}^{18}\textrm{O}+^{181}}$$Ta Reaction

The results of experiments performed at a high-resolution magnetic spectrometer (MAVR) are presented. The differential production cross sections for oxygen isotopes in the $${}^{18}\textrm{O}+^{181}$$ Ta reaction at the projectile energy of 10 MeV per nucleon were measured at the MAVR facility. The yield of reaction products is analyzed theoretically in the finite-range distorted-wave Born approximation (FR-DWBA method) by means of the FRESCO code. The theoretical differential cross sections are calculated for sequential neutron transfer. The contributions of the mechanisms of sequential neutron transfer and dineutron-cluster transfer to the production cross sections for the neutron-rich oxygen isotopes $${}^{20,22,24}$$ O are studied.

Excitation and $ \gamma$-decay coincidence measurements at the GRAF beamline for studies of pygmy and giant dipole resonances

Physical studies of electric dipole excitations in atomic nuclei e.g. the structure of pygmy dipole resonances and isovector giant dipole resonances are attracting much attention recently. In this article, we describe a technical development in the coincidence measurement of the excitation processes with the Grand Raiden high-resolution magnetic spectrometer and the $ \gamma$-decay processes by the CAGRA and SC$ \gamma$ LLA efficient $ \gamma$-detector arrays at the Research Center for Nuclear Physics at Osaka University. Specifically, we describe how we developed a new beamline (GRAF), for $ \gamma$ detection at the target position by placing the spectrometer at an angle of $ 4.5-19.0^\circ$ and by transporting the primary beam to a well-shielded beam dump. Experimental conditions and representative data are shown for each of the two $ \gamma$-detector arrays.

Charged Particle Trajectories in the MAVR High-Resolution Magnetic Spectrometer

Charged-particle trajectories in the MAVR high-resolution magnetic spectrometer [1] are simulated. The latter has been constructed at the U400 accelerator for purifying the incident beam and identifying the products of nuclear reactions induced by the beams of stable and radioactive nuclei. In this paper we present the MAVRPC software package, aimed at reconstructing the spectrometer focal plane, optimizing the fields of quadrupole and dipole magnets, and estimating the solid-angle acceptance for secondary particles.

Evaluation of multiple alternative instrument platforms for targeted and non-targeted dioxin and furan analysis.

The use of gas chromatography coupled to high-resolution magnetic sector mass spectrometers (GC-HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC-HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API-MS/MS, 1 traditional EI-MS/MS, an API-quadrupole time of flight mass spectrometer (API-QTOF), and a EI-high-resolution TOF (EI-HRTOF). This study compared these 5 instruments to a GC-HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API-MS/MS instruments provide the greatest overall improvement in MDL value over the GC-HRMS with a 1.5 to 2-fold improvement. The API-QTOF and EI-TOF demonstrate slight increases in MDL value as compared with the GC-HRMS with a 1.5-fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC-HRMS. All 5 instruments offer a viable alternative to GC-HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.

Differential cross section measurement of the 12C(e,e’pp)10Beg.s. reaction

The differential cross section was measured for the 12C(e,e’pp)10Beg.s. reaction at energy and momentum transfers of 163MeV and 198MeV/c, respectively. The measurement was performed at the Mainz Microtron by using two high-resolution magnetic spectrometers of the A1 Collaboration and a newly developed silicon detector telescope. The overall resolution of the detector system was sufficient to distinguish the ground state from the first excited state in 10 Be. We chose a super-parallel geometry that minimizes the effect of two-body currents and emphasizes the effect of nucleon-nucleon correlations. The obtained differential cross section is compared to the theoretical results of the Pavia reaction code in which different processes leading to two-nucleon knockout are accounted for microscopically. The comparison shows a strong sensitivity to nuclear-structure input and the measured cross section is seen to be dominated by the interplay between long- and short-range nucleon-nucleon correlations. Microscopic calculations based on the ab initio self-consistent Green’s function method give a reasonable description of the experimental cross section.

System on chip (SoC) microcontrollers (μC) as digitisers for ion beam analysis (IBA) instruments

Data digitisation of the analogue signals from detectors to digital data is an essential process in ion beam analysis (IBA). The low-cost, easy availability and development environments that have a low learning threshold makes system-on-chip (SoC) microcontrollers (μC) attractive for this task. These μC combine, on one die, analogue and digital inputs and outputs with serial USB interfaces, which opens up simple implementation of tailor-made interfaces for specific IBA measurement systems. We have investigated the design and performance limitations based on development of three different digitisation interfaces for IBA. These were a two-channel nuclear instrumentation module (NIM) ADC event mode interface (EMI) for a high-resolution magnetic RBS spectrometer, a simple headless-multi-channel analyser (MCA) and a combined dual channel headless MCA and EMI. It is shown that SoC μC based interfaces for digitisation of analogue spectroscopy pulses in IBA systems can be implemented for material costs less than 100€. The performance of the SoC devices for many IBA applications is close to what can be achieved with state-of-the-art instruments. The simple pulse spectroscopy interface circuit and software are included in the auxiliary archive.

Ground-state binding energy of [formula omitted] from high-resolution decay-pion spectroscopy

A systematic study on the Λ ground state binding energy of hyperhydrogen HΛ4 measured at the Mainz Microtron MAMI is presented. The energy was deduced from the spectroscopy of mono-energetic pions from the two-body decays of hyperfragments, which were produced and stopped in a 9Be target. First data, taken in the year 2012 with a high resolution magnetic spectrometer, demonstrated an almost one order of magnitude higher precision than emulsion data, while being limited by systematic uncertainties. In 2014 an extended measurement campaign was performed with improved control over systematic effects, increasing the yield of hypernuclei and confirming the observation with two independent spectrometers and two targets of different thicknesses. The analysis of these data is in agreement with the previously published value for the HΛ4 binding energy as well as with a consistent re-analysis of the 2012 data. When compared to the HeΛ4 binding energy from emulsion data, a large charge symmetry breaking effect in the A=4 hypernuclear system is confirmed.

Development of a new RFQ beam cooler and buncher for the CANREB project at TRIUMF

A new radiofrequency quadrupole (RFQ) based ion beam cooler and buncher is under development for the CANadian Rare-isotope facility with Electron Beam ion source (CANREB) project at TRIUMF. The CANREB project requires an RFQ buncher that will efficiently accept continuous beams of rare isotopes from either the Advanced Rare IsotopE Laboratory (ARIEL) or Isotope Separator and ACcelerator (ISAC) target by way of a high resolution magnetic spectrometer, with energies up to 60keV and deliver bunched beams to an electron beam ion source (EBIS) for charge breeding. The energy of the bunched beam delivered to the EBIS will be adjustable to match the requirements of the existing post acceleration infrastructure. The CANREB RFQ incorporates design considerations to facilitate ease of use over a wide range of ion masses, and is intended to accommodate incident beam rates as high as 108pps, delivering beam bunches at 100Hz. An overview of the CANREB RFQ design concept will be presented, informed by results from both ion optical simulations as well as commissioning efforts with other beam cooler and buncher devices. Simulation results indicate that the design is well suited to deliver high quality bunched beams with high efficiency with as many as 106 ions per bunch.

Spectroscopy of low lying states in 136Cs

The low-lying excited states in 136Cs relevant to the double beta decay of 136Xe were studied via a 138Ba(d, α)136Cs transfer reaction with a high resolution magnetic spectrometer. Preliminary results from the experiment are presented.

Experimental investigations of the hypernucleusΛ4H

Negatively charged pions from two-body decays of stopped _Lambda^4H hypernuclei were studied in 2012 at the Mainz Microtron MAMI, Germany. The momenta of the decay-pions were measured with unprecedented precision by using high-resolution magnetic spectrometers. A challenge of the experiment was the tagging of kaons from associated K^+∧ production off a Be target at very forward angles. In the year 2014, this experiment was continued with a better control of the systematic uncertainties, with better suppression of coincident and random background, improved particle identification, and with higher luminosities. Another key point of the progress was the improvement in the absolute momentum calibration of the magnetic spectrometers.

A new Time-of-Flight mass measurement project for exotic nuclei and ultra-high precision detector development

The time-of-flight (TOF) mass spectrometry (MS), a high-resolution magnetic spectrometer equipped with a fast particle tracking system, is well recognized by its ability in weighing the most exotic nuclei. Currently such TOF-MS can achieve a mass resolution power of about 2×10−4 . We show that the mass resolution can be further improved by one order of magnitude with augmented timing and position detectors. We report the progress in developing ultra-fast detectors to be used in TOF-MS.

High-precision three-dimensional field mapping of a high resolution magnetic spectrometer for hypernuclear spectroscopy at JLab

The High Resolution Kaon Spectrometer (HKS), which consists of two quadrupole magnets and one dipole magnet, was designed and constructed for high-resolution spectroscopy of hypernuclei using the (e,e′K+) reaction in Hall C, Jefferson Lab (JLab). It was used to analyze momenta of around 1.2GeV/cK+ s with a resolution of 2 ×10−4 (FWHM). To achieve the target resolution, a full three-dimensional magnetic field measurement of each magnet was successfully performed, and a full three-dimensional magnetic field map of the HKS magnets was reconstructed. Using the measured field map, the initial reconstruction function was generated. The target resolution would be achieved via careful tuning of the reconstruction function of HKS with the p(e,e′K+)Λ,Σ0 and 12C (e,e′K+)12Λ Bg.s. reactions. After tuning of the initial reconstruction function generated from the measured map, the estimated HKS momentum resolution was 2.2×10−4 (FWHM).