High Resolution Electrostatic Analyzer Research Articles

New Data on Autoionizing States of Ne Induced by Low-Energy Electrons from 45 to 64 eV

The lowest single and doubly excited autoionizing states of neon have been studied using a non-monochromatic electron beam and a high-resolution electrostatic analyzer at incident electron energies from 43.37 to 202 (±0.4) eV at three ejection angles, 40°, 90° and 130°. The 2s2p63s(3,1S) and 2s2p63p(3,1P) as well as the 2p43s3p doubly excited states have been observed and their energy determined. The influence of the PCI effect in the energy region of the 2s2p63s(3,1S) states has been investigated. New features in the ejected electron spectra in the low kinetic energy region 3–20 eV at 202 eV incident energy have been observed and assigned.

The M4,5-NN Auger and M2,3-M4,5N Coster-Kronig spectra of krypton induced by electron impact

The Kr M4,5-NN Auger transitions are studied in the kinetic energy region 24 - 59 eV by using non-monochromatic electron beam and a high resolution electrostatic analyzer. Among the sixty four features observed, fifty five are assigned, while nine stay unassigned. The post-collision interaction (PCI) effects in the M5-N1N1(1S0) and M5-N2,3N2,3(1S0) Auger peaks are studied as a function of electron incident energy approaching the M5 edge (95.04 eV). The PCI shifts are found to be well represented by an exponential function of the excess energy with exponents β = (-0.99±0.05 and -3.08±0.05) for the N2,3N2,3(1S0) and N1N1(1S0) peaks, respectively. The M2,3-M4,5N Coster-Kronig transitions are studied in kinetic energy region 65 - 110 eV and at incident energies from 120 to 2019 eV. Owing to a high resolution twelve well resolved satellites in the region bellow 90 eV are observed, while in the region 90 - 110 eV two broad features are assigned to the M2,3-M4,5N2,3 C-K peaks with intensity ratio (M3/M2 = 2.37) are observed. Comparison is made with available data from literature.

The Auger spectra in argon induced by electron impact – new measurements with high resolution

The Auger spectrum of argon in the kinetic energy region (135–235 eV) has been measured using a non-monochromatic electron beam (incident energy from 313 to 2019 eV) at two ejection angles of 60° and 90° with a high resolution electrostatic analyzer. The electron impact energies of 313 and 323 eV have been used in order to disentangle the contribution of the ionization and decay of the 2s state. The systematic analysis of the measured spectra shows the dominance of the Coster-Kronig transitions from the 2s ionization in the energy region 135–159 eV and 208–235 eV, while the Auger transitions from the 2p ionization are dominant in the energy region 160–208 eV. The high resolution of the present work led to the observation of a certain number of new features in two energy regions 135–159 and 208–235 eV, respectively. Recent literature data on the cascade Auger processes and threshold formation of Ar2+ satellite states allow the assignment of some of them, while other have been left without assignments. The influence of the PCI effect on the line-shape, width and energy position of the features in the kinetic energy region 200–208 eV has been also investigated and the PCI shift versus excess energy above threshold compared with previous data and theoretical predictions.

Interaction of molecular beam with thin layer graphene foils**Project supported by the National Natural Science Foundation of China (Grant No. 11575121) and the National Magnetic Confinement Fusion Program of China (Grant No. 2014GB125004).

The interaction of MeV molecular ions with thin layer graphene and graphite foils was studied by using a high-resolution electrostatic analyzer. A large number of fragment protons were observed at zero degree (along the beam direction) when the beam was passing through the monolayer graphene foil, which indicates that the electron of the molecular ions can be stripped easily even by the monolayer graphene foil. More trailing than leading protons were found in the energy spectrum, which means significant wake effect was observed in the monolayer graphene foil. The ratio of the numbers of trailing protons over leading protons first increased with the thickness for the much thinner graphene foils, and then decreased with the thickness for the much thicker graphite foils, which indicates that the bending effect of the wake field on the trailing proton varied with the foil thickness.

VERA, an AMS facility for “all” isotopes

VERA, the Vienna Environmental Research Accelerator, was equipped from the start in 1996 with magnets strong enough to bend all known isotopic species. However, considerable improvements were needed to allow AMS analysis of nuclides above mass 150, leading to an almost complete rebuild of the high-energy analyzer. After the analyzer magnet, a new high-resolution electrostatic analyzer (ESA) was installed. First measurements of 182Hf, 236U and 244Pu were successfully performed. The higher background suppression has brought along a significant improvement for 26Al measurements, where a background of 26Al/27Al of ∼6×10−16 is reached.

Comparison between simulations and calibrations of a high resolution electrostatic analyzer

The ion beam spectrometer (IBS) is one of the three spectrometers in the Cassini plasma spectrometer instrument aboard the Cassini/Huygens spacecraft. The IBS is a very high energy resolution hemispherical electrostatic analyzer. The design values of the IBS are analyzer gap 2.5 mm, and middle radius 100 mm. Because of the high energy resolution required, special care had to be used in the design and manufacturing of the instrument. A simulation was developed in order to aid the designing process. Here we show that the best fit to the laboratory calibration of the IBS flight model is obtained using the simulation model, where the inner hemisphere is misaligned by about 20 μm, where a maximum asymmetry of 75 μm is included in the inner hemisphere, and where the analyzer gap is increased from the design value by about 0.1 mm. We show here that geometric factors postulated in the theoretical model resulted in a better agreement between calibrations and simulations than the geometric factors calculated from calibration data alone. We find a value of (2.5±0.1)×10−4 cm2 sr for the geometric factor of the flight model. Finally, we also show that the energy and angle responses of the IBS are somewhat lower than the values calculated directly from the calibration data: (2.0±0.1)% is the value of the full width at half maximum (FWHM) of the energy distribution, and (3.1±0.1)° is the value of the FWHM of the azimuth angle distribution.

Structure, reactivity, and energetics of covalently bound carbon cluster ions, C5+ to C11+: experiment and theory

Laser ablation from a rotating, translating graphite rod is used to create a broad distribution of internally energized carbon cluster ions C{sub n}{sup +}. These energized clusters are accelerated, size selected by a magnet, and allowed to undergo unimolecular decay in a field-free region. The decay products are mass and energy analyzed by a high-resolution electrostatic analyzer. In this work they are interested in clusters in the range 5 {<=} n {<=} 11. The shapes of the kinetic energy distributions strongly suggest there are no energy barriers along the reaction coordinates. A detailed analysis of the kinetic energy distributions and metastable branching ratios was accomplished using the transition-state switching form of statistical phase space theory. The analysis yielded binding energies for each of the fragmentations observed. In general these are in excellent agreement with the ab initio calculations of Raghavachari and Binkley. It is also unambiguously shown for parent cluster ions with 5 {<=} n {<=} 10 that the observed fragmentation are due to linear clusters decaying to linear products. A cyclic parent ion structure for C{sub 11}{sup +} could not be ruled out. Excellent agreement between experiment and theory is obtained in those cases where more than one productmore » channel is observed.« less

A high-resolution electrostatic analyzer for accelerator mass spectrometry

Accelerator mass spectrometry (AMS) has the potential of unparalleled sensitivities for elemental impurity analysis in materials. To fully exploit the capabilities of AMS, a high-resolution electrostatic analyzer (ESA) is shown to be a necessary part of the detection system. An ESA with a resolution of E ΔE > 700 for ions with energies up to E q = 4.8 MeV has been designed and constructed. The system utilizes a 45° deflection in the ion's trajectory with a radius of curvature of 1.2 m. The field is of toroidal geometry, which produces astigmatic focusing of the ion beam, so as to compensate for the lack of vertical focusing in the magnetic spectrometer.

Determination of carbon in EFG silicon ribbons by nuclear techniques and SIMS

The edge defined process (EFG) for preparing silicon crystalline sheets is a promising approach to obtain directly the low cost material needed for manufacturing solar cells. The shape of these ribbons is defined by a graphite die, in contact with the molten silicon. Here, we investigated the contamination introduced by graphite by using three different ion beam techniques: (a) SIMS gives the relative evolution of the various elements as a function of depth, but cannot be calibrated in absolute scale; (b) the 12C( 3He, p) 14N resonance at 2.47 MeV allowed us to evaluate the absolute concentration of carbon, as well as its lattice location by using channelling techniques: no dip was visible for carbon; (c) Rutherford backscattering performed with a high resolution electrostatic analyzer showed that the silicon surface peak width (90 Å) is the same as on a high quality standard prepared in the same way. Therefore, no supplementary amorphous layer exists on the surface.

Range parameters of heavy ions at 10 and 35 keV in silicon

Projected ranges and range straggling of Ge- and As-ions with LSS-energies of ϵ < 0.2 have been measured with backscattering techniques using a high resolution electrostatic analyzer.