Heavy-Ion Rutherford Backscattering Spectrometry : A Comparison of ¹¹B with ⁴He Ions

The Rutherford backscattering spectrometry was examined with ¹¹B and ⁴He ions. Backscattering spectra improve in the mass resolution, the depth resolution and the channeling minimum yield when 6 MeV ¹¹B ions are used instead of 2 MeV ⁴He ions, which have been used commonly. Then the terminal voltage of a 1.7 MV tandem Cockcroft-Walton accelerator was calibrated by means of a combination of the ²⁷Al(p, γ)²⁸Si resonance method and a new iterative method using ¹H and ⁴He ions. The true terminal voltage of the accelerator is lower than the corresponding nominal values, and the deviation quadratically increases with increasing voltage

New Accelerating Tube for 4 MV Van de Graaff Accelerator

The accelerating tube with diametrically magnetized ring magnets for the bending of backstreaming electrons was constructed for the 4 MV Van de Graaff accelerator of Kyoto University. The X-ray yield due to the electron loading was reduced to a factor of about 100 ; and the ion beam current was increased by a factor of about five compared with that of the old tube which had plane electrodes with small accelerating apertures. Characteristics of evacuation, beam convergence and accelerator operation are described ; and typical results of ion analysis are given for hydrogen, helium, nitrogen, neon and argon

Molecular Dynamics of XFEL-Induced Photo-Dissociation, Revealed by Ion-Ion Coincidence Measurements

X-ray free electron lasers (XFELs) providing ultrashort intense pulses of X-rays have proven to be excellent tools to investigate the dynamics of radiation-induced dissociation and charge redistribution in molecules and nanoparticles. Coincidence techniques, in particular multi-ion time-of-flight (TOF) coincident experiments, can provide detailed information on the photoabsorption, charge generation, and Coulomb explosion events. Here we review several such recent experiments performed at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan, with iodomethane, diiodomethane, and 5-iodouracil as targets. We demonstrate how to utilize the momentum-resolving capabilities of the ion TOF spectrometers to resolve and filter the coincidence data and extract various information essential in understanding the time evolution of the processes induced by the XFEL pulses

An External Beam Method for Multi-Elemental Analysis of Heavy Metals in Stream Water

An improvement has been made on a liquid target preparation for an external proton beam PIXE which is regarded as an excellent technique for multi-elemental analysis. A 2 MeV proton beam taken out to the atmosphere through an exit Kapton foil bombards an acidic solution target directly. Such direct bombardment enables the direct comparison of X-ray yields of a liquid sample with those of the standard solution so that one can determine the elemental concentration in a liquid sample more precisely and easily. An example is given for the analysis of heavy metals in stream water

Anatomical consideration for safe pericardiocentesis assessed by three-dimensional computed tomography: Should an anterior or posterior approach be used?

AbstractBackgroundThe efficacy of epicardial catheter ablation for ventricular tachycardia has been reported. However, the safest anatomical method for pericardial puncture has not been determined.MethodsThirty patients who underwent 3-dimensional computed tomography (3D-CT) preceding catheter ablations for atrial fibrillation were enrolled in this study. We used the skin surface 1cm below the xiphisternum as the puncture site. For the anterior approach, the attainment site was the pericardium of the mid portion of right ventricular anterior site, and for the posterior approach it was the pericardium of the inferior ventricular site. The distance and the angle between the 2 sites were measured using 3D-CT.ResultsFor the anterior approach, the distance was 54±11mm and the needle angle was 37±11° toward the left scapula and 34±12° towards the back of the body. For the posterior approach, the distance was 56±10mm and the corresponding needle angles were 60±9° and 86±13°. The distance correlated with BMI for the anterior and posterior approaches (anterior approach: r2=0.43, P<0.001; posterior approach: r2=0.49, P<0.001). Liver existed along the pathway of the posterior approach in 11 (37%) of 30 patients, and through in 2 (18%) of 11 patients. The liver and lung were not located along the pathway of the anterior approach in any patients.ConclusionsPerforming subxiphoid pericardiocentesis is anatomically safer via the anterior approach than via the posterior approach

Topographic variability of the left atrium and pulmonary veins assessed by 3D-CT predicts the recurrence of atrial fibrillation after catheter ablation

AbstractBackgroundCatheter ablation (CA) is an established therapy for atrial fibrillation (AF). However, the assessment of anatomical information and predictors of AF recurrence remain unclear. We investigated the relationship between anatomical information on the left atrium (LA) and pulmonary veins (PVs) from three-dimensional computed tomography images and the recurrence of AF after CA.MethodsSixty-seven consecutive AF patients (mean age: 62±10 years, median AF history: 42 (12; 60) months, mean LA size: 41±7mm, paroxysmal: 56%) underwent CA and were followed for 19±10 months. The segmented surface areas (antral, posterior, septal, and lateral) and dimensions (between the anterior and posterior walls, the right inferior PV and mitral annulus [MA], the right superior PV and MA, the left superior PV and MA, and the mitral isthmus) of the LA were evaluated three dimensionally using the NavX system. The cross-sectional areas of the PVs were also evaluated.ResultsAfter the follow-up period, 49 patients (73%) remained free from AF. A multivariate analysis showed that the diameter of the mitral isthmus and cross-sectional area of the right upper PV were associated with AF recurrence (odds ratio: 1.070, CI: 1.02–1.12, p=0.001; odds ratio: 0.41, CI: 0.21–0.77, p=0.006).ConclusionEnlargement of the mitral isthmus and a smaller right superior PV cross-sectional area were associated with AF recurrence

Evidence for Efficient Pathway to Produce Slow Electrons by Ground-state Dication in Clusters

We present an experimental evidence for a so-far unobserved, but potentially very important step relaxation cascades following inner-shell ionization of a composite system: Multiply charged ionic states created after Auger decay may be neutralized by electron transfer from a neighboring species, producing at the same time a low-energy free electron. This electron transfer-mediated decay (ETMD) called process is effective even after Auger decay into the dicationic ground state. Here, we report the ETMD of Ne2+ produced after Ne 1s photoionization in Ne-Kr mixed clusters

Application of Matched-Filter Concepts to Unbiased Selection of Data in Pump-Probe Experiments with Free Electron Lasers

Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid, scans of the pump-probe delay is preferable to a single long-lasting scan. The limited availability of beamtime makes it impractical to repeat measurements indiscriminately, and the large, rapid flow of single-shot data that need to be processed and aggregated into a dataset, makes it difficult to assess the quality of a measurement in real time. In post-analysis it is then necessary to devise unbiased criteria to select or reject datasets, and to assign the weight with which they enter the analysis. One such case was the measurement of the lifetime of Intermolecular Coulombic Decay in the weakly-bound neon dimer. We report on the method we used to accomplish this goal for the pump-probe delay scans that constitute the core of the measurement; namely we report on the use of simple auto- and cross-correlation techniques based on the general concept of “matched filter”. We are able to unambiguously assess the signal-to-noise ratio (SNR) of each scan, which then becomes the weight with which a scan enters the average of multiple scans. We also observe a clear gap in the values of SNR, and we discard all the scans below a SNR of 0.45. We are able to generate an average delay scan profile, suitable for further analysis: in our previous work we used it for comparison with theory. Here we argue that the method is sufficiently simple and devoid of human action to be applicable not only in post-analysis, but also for the real-time assessment of the quality of a dataset