In situ synchrotron based x-ray techniques as monitoring tools for atomic layer deposition

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γ‐ray diagnostics of α slowing in inertial confinement fusion targets

For large inertial confinement fusion deuterium-tritium targets, a way to diagnose alpha slowing might be via capture reaction gamma rays. Calculations are presented for two such methods: one uses the alpha+T direct capture gamma rays, the other is based on a series of resonant alpha-capture reactions. For small targets (rhoR less-than-or-equal-to 0.02 g/cm2), the total alpha+T gamma-ray yield relative to the DT neutron yield is temperature independent and proportional to the rhoR value. For large targets (rhoR greater-than-or-equal-to 0.2 g/cm2), this quantity becomes temperature dependent and rhoR independent. Some experimental aspects are discussed

A secondary reaction pathway for the alumina atomic layer deposition process with trimethylaluminum and water, revealed by full-range, time-resolved in situ mass spectrometry

A method to obtain full mass over charge (m/z), time-resolved quadruple mass spectrometry (QMS) spectra of an atomic layer deposition (ALD) cycle is proposed. This method allows one to circumvent the limitations of traditional approaches for obtaining QMS information in ALD as all m/z values can be simultaneously screened for the formation of reaction products in an efficient way. As a proof of concept, this method was applied to the trimethylaluminum (TMA)-water process. This process has been studied extensively over the past decades. Besides the expected formation of CH4, formation of gaseous HOAI(CH3)(2) during the water pulse is observed, revealing a secondary reaction pathway for the water. The reaction energy and Gibbs free energy for different reactions are investigated computationally using density functional theory calculations and confirm that the secondary reaction pathway is thermodynamically allowed for certain surface conditions

ICF burn-history measurments using 17-MeV fusion gamma rays

Fusion reaction rate for inertial-confinement fusion (ICF) experiments at the Nova Laser Facility is measured with 30-ps resolution using a high-speed neutron detector. We are investigating a measurement technique based on the 16.7-MeV gamma rays that are released in deuterium-tritium fusion. Our concept is to convert gamma-ray energy into a fast burst of Cerenkov light that can be recorded with a high-speed optical detector. We have detected fusion gamma rays in preliminary experiments conducted at Nova where we used a tungsten/aerogel converter to generate Cerenkov light and an optical streak camera to record the signal

Measurement of the half-life of the T=12\frac{1}{2} mirror decay of 19^{19}Ne and its implication on physics beyond the standard model

The $\frac{1}{2}^+ \rightarrow \frac{1}{2}^+$ superallowed mixed mirror decay of $^{19}$Ne to $^{19}$F is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be $T_{1/2}$ = $17.2832 \pm 0.0051_{(stat)}$ $\pm 0.0066_{(sys)}$ s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed.Comment: 5 pages, 3 figures, 1 tabl

Intruder bands and configuration mixing in the lead isotopes

A three-configuration mixing calculation is performed in the context of the interacting boson model with the aim to describe recently observed collective bands built on low-lying $0^+$ states in neutron-deficient lead isotopes. The configurations that are included correspond to the regular, spherical states as well as two-particle two-hole and four-particle four-hole excitations across the Z=82 shell gap.Comment: 20 pages, 4 figures, accepted by PRC, reference added for section 1 in this revised versio

Collinear laser spectroscopy of radioisotopes of zirconium

Isotope shifts and hyperfine structures have been measured for radioisotopes of ionic zirconium using on-line laser spectroscopy at the IGISOL facility in Jyväskylä, where the installation of an ion beam cooler/buncher has significantly improved the experimental sensitivity. Measurements have been made on all the neutron-deficient isotopes from 87Zr to 90Zr, including the isomers 87m,89mZr, and the neutron-rich isotopes from 96Zr to 102Zr. The change in mean square charge radii between the isotopes and the nuclear moments of the odd isotopes have been extracted. The data show a sudden increase in the mean square charge radius at mass A = 100, consistent with an onset of nuclear deformation which has been observed in the gamma ray spectroscopy of isotope chains in this region of the nuclear chart.</p

Precision of the PET activity range during irradiation with ¹⁰C, ¹¹C, and ¹²C beams

Objective. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable 12C ions, the positron emitters 10,11C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam. Approach. An experiment studying the precision of the measurement of ranges of positron-emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner. Main results. High-quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes 11C and 10C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6 × 107 ions in 4 spills for a total duration of 19.2 s, the PET activity range uncertainty for 10C, 11C and 12C is 0.04 mm, 0.7 mm and 1.3 mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from 11C to 10C than when going from 12C to 11C. The much better precision for 10C is due to its much shorter half-life, which, contrary to the case of 11C, also enables to include the in-spill data in the image formation. Significance. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics.</p