Czochralski growth and spectroscopic investigations of Yb3+, La3+:Na2SO4(I) and Nd3+:Na2SO4(I)

Ln3+-stabilized Na2SO4 (phase I) single crystals were grown by the Czochralski method. Differential thermal analysis revealed the influence of the ionic radius of Ln3+ on the stabilization of Na2SO4(I). Distribution coefficients (∼0.8-1.1) were measured by the inductively coupled plasma optical emission spectroscopy method and x-ray fluorescence spectroscopy. Spectroscopic investigations yielded absorption cross sections of 0.6 × 10−20 cm2 (π-polarized, 928.5 nm) and 1.5 × 10−20 cm2 (π-polarized, 797.3 nm) for Yb3+, La3+:Na2SO4 and Nd3+:Na2SO4, respectively. Crystal growth of Gd3+-stabilized Na2SO4(I) provides an interesting new material for stimulated Raman scattering experiment

Spherical codes with prescribed signed permutation automorphisms inside shells of low-dimensional integer lattices

Let $\textrm{S}(n,t,k)$ be the maximum size of a code containing only vectors of the $k$th shell of the integer lattice $\mathbb{Z}^n$ such that the inner product between distinct vectors does not exceed $t$. In this paper we compute lower bounds for $\textrm{S}(n,t,k)$ for small values of $n$, $t$ and $k$ by carrying out computer searches for codes with prescribed automorphisms. We prescribe groups of signed permutation automorphisms acting transitively on the pairs of coordinates and coordinate values as well as other closely related groups of automorphisms. Several of the constructed codes lead to improved lower bounds for spherical codes

Interferometer-based high-accuracy white light measurement of neutral rubidium density and gradient at AWAKE

The AWAKE experiment requires an automated online rubidium (Rb) plasma density and gradient diagnostic for densities between 1 and 10$\cdot$10$^{14}$ cm$^{-3}$. A linear density gradient along the plasma source at the percent level may be useful to improve the electron acceleration process. Because of full laser ionization of Rb vapor to Rb$^{+}$ within a radius of 1 mm, the plasma density equals the vapor density. We measure the Rb vapor densities at both ends of the source, with high precision using, white light interferometry. At either source end, broadband laser light passes a remotely controlled Mach-Zehnder interferometer built out of single mode fibers. The resulting interference signal, influenced by dispersion in the vicinity of the Rb D1 and D2 transitions, is dispersed in wavelength by a spectrograph. Fully automated Fourier-based signal conditioning and a fit algorithm yield the density with an uncertainty between the measurements at both ends of 0.11 to 0.46 $\%$ over the entire density range. These densities used to operate the plasma source are displayed live in the control room.Comment: 5 pages, 8 figures, EAAC2017 conference proceedin

Predicting the Trajectory of a Relativistic Electron Beam for External Injection in Plasma Wakefields

We use beam position measurements over the first part of the AWAKE electron beamline, together with beamline modeling, to deduce the beam average momentum and to predict the beam position in the second part of the beamline. Results show that using only the first five beam position monitors leads to much larger differences between predicted and measured positions at the last two monitors than when using the first eight beam position monitors. These last two positions can in principle be used with ballistic calculations to predict the parameters of closest approach of the electron bunch with the proton beam. In external injection experiments of the electron bunch into plasma wakefields driven by the proton bunch, only the first five beam position monitors measurements remain un-affected by the presence of the much higher charge proton bunch. Results with eight beam position monitors show the prediction method works in principle to determine electron and proton beams closest approach within the wakefields width ($<$1\,mm), corresponding to injection of electrons into the wakefields. Using five beam position monitors is not sufficient.Comment: seven pages, five figures, submitted for EAAC 2019 Proceeding

Ambidentate coordination in hydrogen bonded dimethyl sulfoxide, (CH3)2SOH3O+, and in dichlorobis(dimethyl sulfoxide) palladium(II) and platinum(II) solid solvates, by vibrational and sulfur K-edge X-ray absorption spectroscopy

The strongly hydrogen bonded species (CH3)(2)SO center dot center dot center dot H3O+ formed in concentrated hydrochloric acid displays a new low energy feature in its sulfur K-edge X-ray absorption near edge structure (XANES) spectrum. Density Functional Theory-Transition Potential (DFT-TP) calculations reveal that the strong hydrogen bonding decreases the energy of the transition S(1s) -> LUMO, which has antibonding sigma*(S-O) character, with about 0.8 eV. Normal coordinate force. field analyses of the vibrational spectra show that the SO stretching force constant decreases from 4.72 N cm(-1) in neat liquid dimethyl sulfoxide to 3.73 N cm(-1) for the hydrogen bonded (CH3)(2)SO center dot center dot center dot H3O+ species. The effects of sulfur coordination on the ambidentate dimethyl sulfoxide molecule were investigated for the trans-Pd((CH3)(2)SO)(2)Cl-2, trans-Pd((CD3)(2)SO)(2)Cl-2 and cis-Pt((CH3)(2)SO)(2)Cl-2 complexes with square planar coordination of the chlorine and sulfur atoms. The XANES spectra again showed shifts toward low energy for the transition S(1 s) -> LUMO, now with antibonding sigma*(M-Cl, M-S) character, with a larger shift for M = Pt than Pd. DFT-TP calculations indicated that the differences between the XANES spectra of the geometrical cis and trans isomers of the M((CH3)(2)SO)(2)Cl-2 complexes are expected to be too small to allow experimental distinction. The vibrational spectra of the palladium(II) and platinum(II) complexes were recorded and complete assignments of the fundamentals were achieved. Even though the M-S bond distances are quite similar the high covalency especially of the Pt-S bonds induces significant increases in the S-O stretching force constants, 6.79 and 7.18 N cm(-1), respectively

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure &lt; 100 mmHg (n = 1127), estimated glomerular filtration rate &lt; 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Czochralski growth and spectroscopic investigations of Yb3+, La3+:Na2SO4(I) and Nd3+:Na2SO4(I)

Ln3+-stabilized Na2SO4 (phase I) single crystals were grown by the Czochralski method. Differential thermal analysis revealed the influence of the ionic radius of Ln3+ on the stabilization of Na2SO4(I). Distribution coefficients (∼0.8–1.1) were measured by the inductively coupled plasma optical emission spectroscopy method and x-ray fluorescence spectroscopy. Spectroscopic investigations yielded absorption cross sections of 0.6 × 10−20 cm2 (π-polarized, 928.5 nm) and 1.5 × 10−20 cm2 (π-polarized, 797.3 nm) for Yb3+, La3+:Na2SO4 and Nd3+:Na2SO4, respectively. Crystal growth of Gd3+-stabilized Na2SO4(I) provides an interesting new material for stimulated Raman scattering experiments

SrB₄O₇ : Sm²⁺: crystal chemistry, Czochralski growth and optical hole burning

The crystal chemistry of the Sm3z to Sm2z reduction in tetraborate lattices was investigated. In crystalline SrB4O7 in air it is mainly Sm2z that is incorporated from a melt or glass containing predominantly Sm3z. For the process in air, a reduction and pick-up mechanism is assumed to take place at the crystal/nutrient interface. Stabilization of Sm2z in SrB4O7 at high temperature and in an oxidizing atmosphere seems to be a particular property of the system, because no Sm2z inclusion could be observed along the series MB4O7 (M~Ca, Ba, Cd, Pb), if similar reaction conditions were applied. So far, there is only one other oxide lattice (BaB8O13) known where at high temperatures significant amounts of Sm2z are obtained for reactions in the air. Single crystals of SrB4O7 : Sm2z were grown by the Czochralski method (keff for Sm is 0.5). Optical hole burning experiments for the transition 5D1±7F0 were performed at 80 K. A hole with a width of 0.21 cm21 and a depth of 5.25% was formed for the first time for Sm2z in a borate crystal excited by the beam of a single frequency dye laser. A rather small inhomogeneous linewidth of 0.28 cm21 allowed the burning of a single hole only

Generation and delivery of an ultraviolet laser beam for the RF-photoinjector of the AWAKE electron beam

In the AWAKE experiment, the electron beam is used to probe the proton-driven wakefield acceleration in plasma. Electron bunches are produced using an rf-gun equipped with a Cs$_2$Te photocathode illuminated by an ultraviolet (UV) laser pulse. To generate the UV laser beam a fraction of the infrared (IR) laser beam used for production of rubidium plasma is extracted from the laser system, time-compressed to a picosecond scale and frequency tripled using nonlinear crystals. The optical line for transporting the laser beam over the 24 m distance was built using rigid supports for mirrors and air-evacuated tube to minimize beam-pointing instabilities. Construction of the UV beam optical system enables appropriate beam shaping and control of its size and position on the cathode, as well as time delay with respect to the IR pulse seeding the plasma wakefield

Integration of a Terawatt Laser at the CERN SPS Beam for the AWAKE Experiment on Proton-Driven Plasma Wake Acceleration

In the AWAKE experiment a high-power laser pulse ionizes rubidium atoms inside a 10 m long vapor cell thus creating a plasma for proton-driven wakefield acceleration of electrons. Propagating co-axial with the SPS proton beam the laser pulse seeds the self-modulation instability within the proton bunch on the front of plasma creation. The same laser will also generate UV-pulses for production of a witness electron beam using an RF-photoinjector. The experimental area formerly occupied by CNGS facility is being modified to accommodate the AWAKE experiment. A completely new laser laboratory was built, taking into account specific considerations related to underground work. The requirements for AWAKE laser installation have been fulfilled and vacuum beam lines for delivery of laser beams to the plasma cell and RF-photoinjector have been constructed. First results of laser beam hardware commissioning tests following the laser installation will be presented