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An ion optical design of a high resolution multi-turn time-of-flight mass analyzer (MT-TOF MA) is presented. The analyzer has rotationally symmetric main electrodes with additional mirror symmetry about a mid-plane orthogonal to the axis of symmetry. Rotational symmetry allows a higher density of turns in the azimuthal (drift) direction compared to MT-TOF MAs that are linearly extended in the drift direction. Mirror symmetry about a mid-plane helps to achieve a high spatial isochronicity of the ions’ motion. The analyzer comprises a pair of polar-toroidal sectors S₁ and S₃, a pair of polar (trans-axial) lenses, and a pair of conical lenses for longitudinal and lateral focusing. A toroidal sector S₂ located at the mid-plane of the analyzer has a set of embedded drift focusing segments providing focusing and spatial isochronicity in the drift direction. The ions’ drift in the azimuthal direction can be reversed by using dedicated reversing deflectors. This gives the possibility of several operational modes with different numbers of turns and passes in the drift direction. According to numerical simulations, the mass resolving power of the analyzer ranges from $\sim$40 k (fwhm) at small (typically below ten) numbers of turns to $\sim$450 k (fwhm) at 96 turns.

Wire meshes commonly used as transmission grids in ion optical configurations has certain unavoidable disadvantages. Apart from the loss in transmission, there are small angle deflections while the ions are passing close to the wires. This is important for high resolution time-of-flight mass spectrometry as this effect impairs both the dynamic range and the resolution. The amount of deflection from various commercially available grids are determined from simulation calculations on representative wire grids. Gridless designs of ion optics are becoming more popular in recent times for sophisticated and sensitive measurements. Here we report such a device for time of flight mass spectrometer that also assists in perpendicular ionization. This ion optics together with a gridless ion reflector gives a high time resolution of more than 40000.

A novel dual time-of-flight imaging analyzer has been developed for studies of gas phase reactions and the scattering or desorption of ions and molecules from surfaces. The analyzer is capable of experimentally selecting a two-dimensional slice of particles from a three-dimensional flux without the necessity for deconvolution of the resulting velocity images by the Abel transform. The analyzer operates through ionization of the scattered species and their subsequent flight through a field-free region. This initial flight allows a dispersion according to the species natural velocity distribution. The second time of flight deflects the ions through a right angle and through a flight tube allowing dispersion according to mass or charge before detection. The analyzer offers two modes of operation — the first of these produces a mass spectrum of the desorbing species, the second produces a two-dimensional velocity map of the desorbing species. Trial results using an effusive beam source and acetone as a test gas have demonstrated the operation of the analyzer. The operation of the analyzer has been simulated and optimized to reduce ion flight aberrations. A set of orthogonal two-dimensional polynomial functions have been derived to reduce residual aberrations across a broad range of operating conditions. An upper limit to the temporal resolution of the analyzer has been established and a set of working parameters for low distortion electron beam ionization have been presented.

Industrial equipment can be exposed to various types of damage during their long exploitation in harsh environments which might lead to corrosion cracking. Typically, a hidden crack is very dangerous since it is difficult to be detected by Non-Destructive Testing (NDT) techniques. Moreover, the integrity requirements of metallic structures cannot be satisfied by simply detecting the existence of cracks. However, the quantitative description of the cracks is still an issue that should be solved. This paper introduces a new approach to estimate the dimensions of hidden cracks inside a stainless steel plate based on Shear Vertical (SV) waves generated by an Electromagnetic Acoustic Transducer (EMAT). The Finite Elements Method (FEM) has been used to model the acquired signal by EMAT. Then, the characterization of hidden cracks is carried out by combining two methods; Time-of-Flight (ToF) technique that has been used to evaluate the crack height, and the Partial Least Square Regression (PLSR) method that has been used to estimate the crack width. The obtained results demonstrate the efficiency and the reliability of the adopted approach concerning the quantitative evaluation of the crack dimensions.

Beta-delayed neutrons emitted from the decay of fission fragments play an important role in the r-process and nuclear reactor physics. Neutron energy spectra provide information necessary to accurately reconstruct a level scheme that reflects nuclear structure. Decay cascades where neutron emission populate excited states in the (N-1) daughter complicate level scheme construction. These excited states in the (N-1) daughter often emit gamma-rays. These situations necessitate measurement of three-fold coincidence between the beta, neutron and gamma-ray. However, there is a scarcity of measurements providing these data.

To address this need, we designed the Versatile Array of Neutron Detectors at Low Energy (VANDLE), which measures neutron energies via the time-of-flight technique. VANDLE is instrumented with a digital data acquisition system. The digital system provides a neutron detection threshold as low as 70 keV and time resolutions better than 1 ns. A high-efficiency gamma-ray detection system enables complete calorimetry of the decay by detecting gamma-rays that follow neutron emission. High purity Ge clovers present isotope identification, but suffer from poor geometric efficiency. A high efficiency array of NaI and LaBr₃ detectors boost neutron-gamma coincidences.

The Time-Of-Flight (TOF) detector of the ALICE experiment is optimized to provide charged-hadron identification to study Pb–Pb collisions ( per nucleon pair) at the LHC. The apparatus, a large 80-ps-resolution cylindrical array, has been installed and commissioned and it is currently fully operative. Cosmic-ray data collected in 2008 have already shown the very good performance of the detector which is collecting more data for accurate timing calibrations. An overview of the system and its present status will be reported as well as the results obtained with cosmic-ray data and the expected performance at the LHC startup.

The recently commissioned Versatile Array of Neutron Detectors at Low Energy (VANDLE)¹ was designed to measure neutron energies from nuclear excited states populated through beta decay or transfer reactions. Because the neutron energy is determined by the time-of-flight technique, a time resolution better than 1 ns is necessary. Another important design requirement was a low amplitude detection threshold needed to measure neutron energies as low as 100 keV.

A fully digital data acquisition system has been developed using XIAs DGF Pixie-16 hardware. These goals have been met via essential technical developments: an algorithm for the extraction of sub-sample time information from digitized waveforms and a new triggering scheme. Both of these advancements were critical to achieve the design goals for VANDLE.