Quadrupole Doublet Research Articles

Testing of the First of Series Quadrupole Doublet Module for the SIS100 Synchrotron

Testing of the First of Series Quadrupole Doublet Module for the SIS100 Synchrotron

Synthesis and Characterization of Symmetrically versus Unsymmetrically Proton-Bridged Hexa-Iron Clusters.

Syntheses and magnetic and structural characterization of hexa-iron complexes of derivatized salicylaldoximes are discussed. Complexation of Fe(BF4)2·6H2O with each ligand (H2L1 and H4L2) in a methanolic-pyridine solution resulted in hexa-iron compounds (C1 and C2, respectively), which each contain two near-parallel metal triangles of [Fe3–μ3-O], linked by six fluoride bridges and stabilized by a hydrogen-bonded proton between the μ3-O groups. Within each metal triangle of C2, Fe(III) ions are connected via the amine “straps” of (H4L2-2H). Variable-temperature magnetic susceptibility and Mössbauer data of C1 and C2 indicate the presence of dominant antiferromagnetic interactions between the high-spin (S = 5/2) Fe(III) centers. For C1, two quadrupole doublets are observed at room temperature and 5 K, consistent with structural data from which discrete but disordered [Fe3–μ3-O] and [Fe3–μ3-OH] species were inferred. For C2, a single sharp quadrupole doublet with splitting intermediate between those determined for C1 was observed, consistent with the symmetric [Fe3–μ3-O···H···μ3-O–Fe3] species inferred crystallographically from the very short μ3-O···μ3-O separation. The differences in the physical properties of the complexes, as seen in the Mössbauer, X-ray, and magnetic data, are attributed to the conformational flexibility imparted by the nature of the linkages between the closely related ligands.

Structural Energy Distribution and Particle Phase Stability Study of Longitudinal Dynamics of a Simple Linear Proton Accelerator

This paper presents the study of longitudinal beam dynamics of a simple linear proton accelerator and simulation results for a model linear accelerator (LINAC) using MATLAB. The study part of the transition energy, particle acceleration, transit time factor, RF factor, and momentum compaction are discussed. For the simulation, the model LINAC is built using unit cells and the unit cell consists of Quadrupole doublet and acceleration cavity. Model LINAC’s basic setup is present and the simulation is based on the single-particle analysis. The robustness of the model LINAC tested to operate varying different parameters like initial arrival phase and input energy. The criteria to measure the robustness of the model LINAC are to check the kinetic energy at the end of the LINAC and the transverse stability of the transfer matrices of each cell. The paper also presents the theoretical analysis of phase stability at both below and above transition energy. The stability of small and larger amplitude oscillations are present and simulation results for different particles each starting with different amplitudes observed, where the large amplitude oscillation falls outside of the separatrix.

Variable temperature Mössbauer investigation of Co0.1Fe0.9S2 nanoparticles

ABSTRACT Co0.1Fe0.9S2 nanoparticles were synthesized by solvothermal method and studied by Mössbauer spectroscopy in the cooling process. Magnetic phase transition can be testified by Mössbauer investigation. The spectrum recorded at room temperature consists of a simple quadrupole doublet, the values of isomer shift and quadrupole splitting of doublet increase gradually with the decrease of temperature. However, the spectrum consists of a sextet when the temperature drops further to 25 K, indicating that the sample changed from paramagnetism to ferromagnetism. The magnetic field at low temperature is probably super-transferred field from the magnetically ordered cobalt atoms through a super-exchange mechanism.

Failure mode studies of the RAON superconducting linear accelerator

The driver accelerator of the RAON is a superconducting linear accelerator consisting of low beta cavities. Studies of various failure modes are performed through extensive machine imperfection studies. It is found that the linac is tolerant of any single superconducting cavity loss except the first nine upstream QWR cavities. Studies also find that the linac design is tolerant of 10% upstream-section cavity failure with the design-beta cavities. It is also found that in case of 10% cavity failure, orbit correction becomes indispensable. On the other hand, if cavity betas of the HWR and the SSR2 increase by 4% from the design values, the linac beam loss starts to increase rapidly, when 10% upstream-section cavities become inoperable. This paper shows quantitatively that significant beam losses can be caused in case of cavity faults, when the exit energy of the upstream section is not high enough. In case of a quadrupole doublet failure in the QWR section, beam loss of about 70 W/m is generated in the immediate downstream and beam operation is not feasible.

Structural and magnetic study of the iron cores in iron(III)-polymaltose pharmaceutical ferritin analogue Ferrifol®

Iron(III)-polymaltose pharmaceutical ferritin analogue Ferrifol® was investigated by high resolution transmission electron microscopy (HRTEM), X-ray diffraction, thermogravimetry, electron magnetic resonance (EMR) spectroscopy, direct current magnetization measurements and 57Fe Mössbauer spectroscopy to get novel information about the structural arrangement of the iron core. The Ferrifol® Mössbauer spectra measured in the range from 295 K to 90 K demonstrated non-Lorentzian two-peak pattern. These spectra were better fitted using a superposition of 5 quadrupole doublets with the same line width. The obtained Mössbauer parameters were different and an unusual line broadening with temperature decrease was observed. Measurements of the Ferrifol® Mössbauer spectra from 60 K to 20 K demonstrated a slow decrease of magnetic relaxation in the iron core. Zero-field-cooled and field-cooled magnetization measurements revealed a blocking temperature at ~33 K and a paramagnetic state of the Ferrifol® iron core at higher temperatures. Isothermal magnetization measurements at 5 K show that the saturation magnetic moment is ~0.31 emu/g. X-band EMR spectroscopy measurements revealed the presence of different magnetic species in the sample. Transmission electron microscopy demonstrated that the size of the iron cores in Ferrifol® is in the range 2–6 nm. The lattice periodicity in these iron cores, measured on the HRTEM images, vary in the range 2.2–2.7 Å. This can be best understood as sets of close packed O(OH) layers in ferrihydrite cores without long range correlation.

2 H QUOSY 2D-NMR Experiments in Weakly Aligning Systems: From the Conventional to the Ultrafast Approach.

We describe three anisotropic ultrafast (UF) QUadrupolar Ordered SpectroscopY (QUOSY) 2D-NMR experiments (referred to as ADUF 2D NMR spectroscopy) designed for recording the 2 H homonuclear 2D spectra of weakly aligned (deuterated) solutes in sub-second experiment times. These new ADUF 2D experiments derive from the Q-COSY, Q-resolved and Q-DQ 2D pulse sequences (J. Am. Chem. Soc. 1999, 121, 5249) and allow the correlation between the two components of each quadrupolar doublet, and then their assignment on the basis of 2 H chemical shifts. The UF 2D pulse sequences are analyzed by using the Cartesian spin-operator formalism for spin I=1 nuclei with a small quadrupolar moment. The optimal experimental/practical conditions as well as the resolution, sensitivity and quantification issues of these ADUF 2D experiments are discussed on comparison to their conventional 2D counterparts and their analytical potentialities. Illustrative ADUF 2D experiments using deuterated achiral/prochiral/chiral solutes in poly-γ-benzyl-L-glutamate based chiral liquid crystals are presented, as well as the first examples of natural abundance deuterium (ANADUF) 2D spectrum using 14.1 T magnetic field and a basic gradient unit (53 G.cm-1 ) in oriented solvents.

Zero-Dimensional Graphene and Its Behavior under Mechanochemical Activation with Zinc Ferrite Nanoparticles

ABSTRACTEquimolar mixtures of zero-dimensional graphene (SkySpring Nanomaterials, 1-5 nm particle size) and zinc ferrite nanoparticles (Alfa Aesar, 50 nm particle size) were exposed to mechanochemical activation by high-energy ball milling for time intervals of 0-12 hours. Their structural and magnetic properties were analyzed by Mӧssbauer spectroscopy and magnetic measurements. The spectra of zinc ferrite milled without graphene were fitted with one quadrupole-split doublet (quadrupole splitting 0.5 mm/s, isomer shift 0.23 mm/s) and indicated that zinc ferrite was superparamagnetic. The line width of the doublet increased from 0.41 to 0.64 mm/s, which correlates with a reduction in particle size as effect of the ball milling processing performed. When graphene was added to the milling powders, the Mӧssbauer spectra showed the appearance of another quadrupole doublet, with a quadrupole splitting of 0.84 mm/s and an isomer shift of -0.38 mm/s. Its abundance to the spectrum remained constant to 4.48% while the milling time was increased. This second doublet could be related to carbon atoms occupying neighborhoods in the proximity of iron atoms. Hysteresis loops were recorded in an applied magnetic field of 5 T at a temperature of 5 K. A change in the approach to saturation of the loop was observed, with saturation being achieved for the sample milled for 12 hours with graphene. Zero-field-cooling-field-cooling (ZFC-FC) was performed on all samples between 5-300 K with an applied magnetic field of 200 Oe. Graphene was found to stabilize the magnetic properties of the milled system of powders to a blocking temperature of about 90 K.

The effect of particle size on structural and magnetic properties of Sm3+ ion substituted Zn-Mn nanoferrites synthesized by glycol-thermal method

Zn0.5Mn0.5SmxFe2-xO4 (0 ≤ x 0.05) fine powders with average crystallite sizes in the range 12–17 nm were synthesized by glycol-thermal reaction. The as-prepared compounds were subjected to thermal annealing process at 1100 °C, after which the crystallite sizes increased to about 60 nm. XRD analysis confirmed a single-phase cubic spinel structure in all the compounds investigated. TEM images showed nearly spherical particles with uniform particle size distributions. SEM and FTIR have been used to study morphology and confirm phase formation, respectively. The Mössbauer spectrum for Zn0.5Mn0.5Fe2O4 (x = 0) at room temperature may be resolved into two quadrupole doublets indicative of paramagnetic spin state. Sm3+ substituted compounds showed weak sextets in addition to broad doublets attributed to some particle magnetic moments in ordered magnetic phase. The Mössbauer spectra of the compounds annealed at 1100 °C exhibit magnetic split sextets indicative of ordered magnetic phase. The compounds have small coercive fields and high saturation magnetization (40 emu/g to 60 emu/g) which reduce with increasing Sm3+ content due to the paramagnetic nature of Sm3+ ions. Magnetic measurements as a function of field and temperature in as-prepared particles showed superparamagnetic behaviour with average moment of about ≈104μB. The average particle size obtained from the magnetic data corresponds well with that estimated from XRD analysis.

Effect of molybdenum doping on the structural and magnetic properties of MnFe2O4 magnetic nanoparticles

Magnetic nanoparticles MnFe2-xMoxO4 (x = 0.00, 0.04, 0.08 and 0.10) have been prepared by wet coprecipitation method at calcination temperature 673 K. X-ray powder diffraction (XRD) was used to study the structural properties of the prepared samples, whereas the vibrating sample magnetometer (VSM) and Mossbauer spectrometry measurements (at T = 300 K and T = 77 K) were used to investigate the magnetic properties. The single-phase cubic spinel structure of the ferrites samples was confirmed by the XRD patterns, and a nonlinear variation in the crystalline size was revealed. VSM hysteresis loops confirmed the ferromagnetic behavior in all the samples with an increase in saturation magnetization with the molybdenum doping. Mossbauer spectra at 300 K showed a mixture of the magnetic sextet and central quadrupole doublet with enhancement in the magnetic sextet in the Mo-doped samples. Moreover, Mossbauer spectra at 77 K revealed the disappearance of the quadrupole doublet in all samples, indicating the enhancement of magnetic properties of manganese ferrites nanoparticles due to Mo-doping.

SAFIIRA: A heavy-ion multi-purpose irradiation facility in Brazil

This work describes the new facility for applied nuclear physics at the University of Sao Paulo, mainly for irradiation of electronic devices. It is a setup composed of a quadrupole doublet for beam focusing/defocusing plus multiple scattering through gold foils to produce low intensity, large-area, and high-uniformity heavy-ion beams from 1H to 107Ag. Beam intensities can be easily adjusted from 102 particles cm2/s to hundreds of nA for an area as large as 2.0 cm2 and uniformity better than 90%. Its irradiation chamber has a high-precision motorized stage, and the system is controlled by a LabViewTM environment, allowing measurement automation. Design considerations and examples of use are presented.

Cryogenic testing of fast ramping superconducting magnets for the SIS100 synchrotron

The international Facility for Antiproton and Ion Research FAIR is currently under construction at GSI, in Darmstadt, Germany. The core component of FAIR, the superconducting SIS100 synchrotron will operate with a high repetition rate of up to 1 Hz. The SIS100 ring with a circumference of 1083 m contains 108 main dipole magnets with a maximal field of 1.9 T. The ion-optical lattice of SIS100 contains also 166 main quadrupoles and 137 corrector magnets. The quadrupole and corrector magnets are assembled in the quadrupole units that are pair-wise integrated in quadrupole doublet modules. All superconducting magnets will be tested at liquid helium temperature to assure their compliancy with the specification. The main dipole modules are being tested at the magnet test facility at GSI. Cold testing of the quadrupole doublet modules is split in the testing of the quadrupole units at JINR, Russia and in testing of fully assembled quadrupole doublet modules at INFN, Italy. The cold testing program includes dynamic AC loss measurements and hydraulic adjustment of the parallel cooling channels of SIS100 next to the training, magnetic field measurements and other tests. We present the scope of cold testing of different types of magnet modules as well as the test results.

Development of a magnetic quadrupole lens for low energy heavy ion beam transport

A magnetic quadrupole lens system coupled to a 30° bending deflection magnet was designed and constructed to realize a beam focusing of Xe+ ions with the energy less than 200 eV. Compared to a triplet electrostatic quadrupole lens system, the quadrupole doublet magnetic lens system showed a larger beam transmission, indicating the mitigation of the space charge in the beam transport region free of the electrostatic field. The misalignment of the magnetic field axis was observed probably due to a slow change in magnetization of magnetic materials to construct the magnetic circuit of the quadrupole lens. A countermeasure to realign the beam axis by coupling the permanent magnets to trim coil electromagnets is proposed.

Multi-Ribbon Profile Monitor for high power proton beam at J-PARC MR Abort Line

Japan Proton Accelerator Research Complex (J-PARC) Main Ring (MR), the world-class high intensity proton synchrotron, provides proton beam to two experimental facilities with two extraction modes: Fast extraction (FX) and Slow extraction (SX). The number of protons per pulse (ppp) in MR recorded the world highest value of 2.7 × 1014 in the FX mode. Now we are planning to increase the ppp further up to 3.3 × 1014 in near future. The beam profile is one of the most important parameters to discuss the high intensity beam dynamics in MR. Monitors using multi-wires /ribbons are effective to measure the beam profile with good accuracy and wide dynamic range. However, they cause significant beam losses by interactions with high-intensity circulating beam in synchrotrons. Recently, we installed new multi-ribbon profile monitor (MRPM) in an abort line in MR. The abort line is one of the extracted beam lines of the FX system. It has a quadrupole doublet which is called Abort Q and transports extracted beam to a beam dump. The FX system can extract the circulating beam in MR with an arbitrary energy. Performing the single-pass measurement with MRPM and changing the transfer matrix by sweeping field strength of Abort Q, the emittance of the extracted beam can be measured. In this paper, we present the design, manufacturing, and results of the first beam test of newly installed MRPM system.

Mössbauer Spectral Study of the Low-Temperature Electronic and Magnetic Properties of α-FePO4 and the Mixed Valence Iron(II/III) Phosphate SrFe3(PO4)3.

The Mössbauer spectra of trigonal α-FePO4, measured between 4.2 and 300 K, exhibit hyperfine parameters characteristic of high-spin iron(III) in a pseudotetrahedral oxygen environment. Between 24.5 and 300 K, the spectra show a paramagnetic quadrupole doublet and at 24.0 K the spectrum reveals the onset of antiferromagnetic exchange. At 4.2 and 16 K, a single magnetic sextet is observed with hyperfine fields of 51.36(1) and 42.74(1) T, respectively, with an angle, θ, of 90° between the principal axis of the electric field gradient tensor in the basal plane of the trigonal unit cell and the hyperfine field along the c axis. The spectra obtained between 21 and 18 K have been fitted with two equal-area magnetic sextets with θ angles of 25 and 85°, angles which indicate that the iron(III) magnetic moments are canted away from the c axis. The reduced hyperfine field versus reduced temperature plot indicates a departure from a Brillouin S = 5/2 behavior, as a result of some magnetostriction at the Néel temperature. The Mössbauer spectra of class 1 mixed-valence SrFe3(PO4)3, measured between 4.2 and 300 K, exhibit hyperfine parameters characteristic of two high-spin iron(II) ions and one high-spin iron(III) ion in a pseudooctahedral oxygen environment. At and above 40 K, the spectra show two paramagnetic quadrupole doublets, whereas at 39.0 K the spectrum reveals the onset of ferrimagnetic exchange. Between 4.2 and 30 K, the spectra have been fitted with two magnetic sextets with θ angles of 85 and 10° for the iron(II) and iron(III) sites, respectively. The reduced hyperfine field versus reduced temperature plots for the iron(II) and iron(III) sites show a distinct departure from Brillouin S = 2 and S = 5/2 behavior, respectively, a departure that suggests a first-order magnetic transition at 39.5(5) K with differing magnetostrictions at the iron(II) and iron(III) sites.

Mössbauer studies of mixed-valence manganite Pb3(Mn0.965Fe0.035)7O15

Pb3Mn7O15 manganite with mixed valence (Mn3+/Mn4+) was studied by Mossbauer effect on 57Fe impurity atoms in the temperature range of 80–673 K. The experimental spectra consisted of two main quadrupole doublets corresponding to trivalent Fe atoms replacing Mn atoms in different positions in the crystal lattice. Identification of the doublets was made on the basis of calculations of quadrupole splitting within the point charges model and taking possible polarization of oxygen ions into account. In two temperature ranges: T ≈ 370–510 K, corresponding to the structural phase transition, and at T ≈ 140–230 K, where strong anomalies of the magnetic and electrical properties were observed, the sharp changes in the hyperfine quadrupole splitting were observed. It is assumed that these changes are caused by changes in the valence of manganese ions and structural deformations.

Can Density Functional Theory Predict Mössbauer Spectra in Pyrolyzed Fe-N-C Catalysts?

57Fe Mössbauer spectroscopy, based on the recoil-free emission and resonant absorption of γ-rays, allows an easier separation of the signals arising from the different Fe environments. This is in the basis of the growing interest of using 57Mössbauer spectroscopy for identification of Fe-based species present in pyrolyzed Fe-N-C catalysts. Because of their high temperature synthesis, these catalysts often comprise different coordinations of atomically-dispersed Fe ions covalently bound to the nitrogen-doped carbon matrix (FeNxCy moieties), but also metallic iron and iron carbides with long-range order.1-3 In the 57Fe Mössbauer spectra (recorded in the absence of a strong external magnetic field) metallic iron and iron carbides result in sextets (except for the paramagnetic γ-Fe structure, leading to singlet spectral component) while the fingerprint of FeNxCy moieties is a doublet spectral component. Precise interpretation of the doublets (often labeled as D1 and D2) allowing to distinguish between iron coordination geometries, spin- and oxidation state remains however challenging and has so far lacked strong theoretical or experimental reference basis for their unambiguous assignments. D1 doublet has an isomer value ranging from 0.33 to 0.4 mm/s and quadrupole splitting (QS) ranging from 0.7 to 1.2 mm/s, which is usually attributed to Fe-N4 defects with Fe2+ in its low spin state. The assignment of the D2 doublet with isomer shifts ranging from 0.36 to 0.52 mm/s and with quadrupole splitting ranging from 2.4 to 2.7 mm/s is more ambiguous. It is attributed to Fe-N4 defects similar to iron phthalocyanine with Fe2+ in its intermediate spin state or to a Fe-N2+2 defect in which Fe binds to four pyridinic nitrogen atoms from two adjacent nitrogen-doped graphene layers. However, these assignments have been based on experimental records of carbon-supported FeN4 macrocycles, which differ greatly from the case in which the Fe-Nx moieties are integrated into the graphene matrix. It appears, therefore, obvious that theoretical Mössbauer spectra should be highly beneficial to rationally assign the D1 and D2 spectra of Fe-N-C materials. Theoretical studies (mostly obtained with density-functional-theory, DFT, based approaches) of 57Fe Mössbauer spectra, have evidenced that the choice of the exchange-correlation functional and atomic basis sets has a strong impact on the accuracy of QS values, in particular for intermediate and high spin iron complexes. It is therefore necessary to examine for every new class of Fe-containing compounds the variation of QS with the DFT functional and other computational details. Theoretical 57Fe Mössbauer spectra in pyrolyzed Fe-N-C catalysts have not yet been made available, which prompted us toward the present DFT study of the quadrupole splitting energies in Fe-N4 defects that are identified as the active sites in the pyrolyzed Fe-N-C materials. Extensive computations of QS in Fe-N4 models with Fe in various coordinations and with different oxidation/spin states have been carried out. The use of several DFT exchange-correlation functionals and basis sets in cluster and periodic approaches are compared and will be reported. The analysis of the DFT calculated values in comparison with experimental data are used to interpret quadrupole doublets ubiquitous in the Mössbauer spectra of pyrolyzed Fe-N-C catalysts. Acknowledgement: This work is supported by the LabEx CheMISyst ANR-10-LABX-05-01.

Flattening of isothermal magnetic entropy change versus temperature curve in amorphous Fe–Mn–Mo–B ribbons

Microstructure, Curie temperature and isothermal magnetic entropy change of the amorphous Fe70Mn10Mo5B15 alloy in the as-quenched state and after annealing within the amorphous state at Ta1=723K and after the accumulative annealing at Ta1=723K and then at Ta2=753K for 0.5 h have been studied. The transmission Mössbauer spectra recorded at 300K are typical of a paramagnetic amorphous alloy and do not reveal distinct changes on annealing. The spectra in all cases are decomposed into a set of symmetric quadrupole doublets ascribed to the amorphous phase and a single line stemming from medium range ordered (MRO) regions which are paramagnetic at room temperature. The volume fraction of such MRO regions is small and increases only slightly on annealing. The Curie temperature of the amorphous phase decreases from 298 K in the as-quenched state to 268 K after the annealing at Ta1 and then increases to 282 K after the accumulative heat treatment at Ta1 and Ta2 due to invar effect. The isothermal magnetic entropy change of the alloy exhibits the “caret like” behavior with the peak values near the Curie points of the amorphous phase. The composites consisted of two adherent ribbons with different mass fraction (α) subjected to the annealing and made of two ribbons in the as-quenched state and after the heat treatment at Ta1 show the flat maxima of the magnetic entropy change in the temperature spans 14K and 34K for α=0.7 and α=0.5 in the former and latter composite, respectively. Parameter α denotes the mass fraction of the ribbon annealed at Ta1 in the composites. The flat maximum of the magnetic entropy change is obtained for the composite made of two ribbons with the same chemical composition but different thermal history. The refrigerant capacity (RC) of the amorphous Fe70Mn10Mo5B15 alloy is about 115 J/kg in the as-quenched state and decreases slightly on annealing. RC is enhanced for the composites in comparison with their components.

The new Sumy nuclear microprobe with single-stage quintuplet lens system

The new Sumy nuclear microprobe for high resolution applications has the same beam line with the present microprobe and uses the same object and aperture collimators. The new probe-forming system is based on five magnetic quadrupole lenses of integrated design with four independent power supplies. It consists of quadrupole doublet of the present microprobe and quadrupole triplet which is allocated after the target chamber of the present microprobe. The electrostatic scanning system of a dog-leg type is located before the triplet. The new target chamber of rectangular design has an optical microscope, secondary electron detector, charged particle detector, target stage and possibility to equip additional devices. Such configuration allows one to install two microprobes for different applications at one beam line, that significantly reduces the cost of the new facility. The present paper describes the status of the new Sumy microprobe, its beam optics and design.

Deposits of iron oxides in the human globus pallidus

Abstract Samples taken from the human brain (Globus Pallidus) have been investigated by physical techniques such as light microscopy, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and SQUID magnetometry. SEM-EDX/TEM investigation reveals multielemental composition of hematite and magnetite nanocrystals with sizes ranging from 40 nm to 100 nm and hematite microcrystals from 3 μm to 7 μm. Room temperature Mössbauer spectra show quadrupole doublets assigning to hematite and ferrihydrite. SQUID measurements of temperature dependence of the mass magnetic susceptibility between T = 2 – 300 K at DC field B 0 = 0.1 T, the field dependence of the mass magnetization taken at the fixed temperature T 0 = 2.0 and 4.6 K and the zero-field cooled and field cooled magnetization experiments (ZFCM/FCM) confirm a presence of ferrimagnetic phases such as maghemite and/or magnetite with hysteresis loops surviving until the room temperature. Differences between these measurements from the point of view of iron oxides detected can indicate important processes in human brain and interactions between ferritin as a physiological source of iron and surrounding environment.