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- Adrich, P., et al.
(author)
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Production of antihydrogen atoms by 6 keV antiprotons through a positronium cloud
- 2023
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In: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 83:11
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Journal article (peer-reviewed)abstract
- We report on the first production of an antihydrogen beam by charge exchange of 6.1 keV antiprotons with a cloud of positronium in the GBAR experiment at CERN. The 100 keV antiproton beam delivered by the AD/ELENA facility was further decelerated with a pulsed drift tube. A 9 MeV electron beam from a linear accelerator produced a low energy positron beam. The positrons were accumulated in a set of two Penning-Malmberg traps. The positronium target cloud resulted from the conversion of the positrons extracted from the traps. The antiproton beam was steered onto this positronium cloud to produce the antiatoms. We observe an excess over background indicating antihydrogen production with a significance of 3-4 standard deviations.
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| 6. |
- Blumer, P., et al.
(author)
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Positron accumulation in the GBAR experiment
- 2022
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1040
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Journal article (peer-reviewed)abstract
- We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H¯+), which has been cooled to a low temperature, and observing the subsequent H¯ annihilation following free fall. To produce one H¯+ ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s.
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- Charlton, M., et al.
(author)
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Positron production using a 9 MeV electron linac for the GBAR experiment
- 2021
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 985
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Journal article (peer-reviewed)abstract
- For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN's Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5 x 10(7) slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux.
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- Husson, A., et al.
(author)
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A pulsed high-voltage decelerator system to deliver low-energy antiprotons
- 2021
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1002
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Journal article (peer-reviewed)abstract
- The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.
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- Kim, B. H., et al.
(author)
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Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment
- 2020
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In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 122-125
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Journal article (peer-reviewed)abstract
- We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment.
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- Lyons, A, et al.
(author)
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Outcomes of etravirine-based antiretroviral treatment in treatment-experienced children and adolescents living with HIV in Europe and Thailand
- 2022
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In: Antiviral therapy. - : SAGE Publications. - 2040-2058 .- 1359-6535. ; 27:3, s. 13596535221092182-
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Journal article (peer-reviewed)abstract
- Etravirine (ETR) is approved as a component of second or third-line antiretroviral treatment (ART) for children living with HIV. We assessed the outcomes of ETR-based ART in children in routine care in Europe and Thailand. Methods Data on children aged <18 years at ETR start were pooled from 17 observational cohorts. Characteristics at ETR start, immunological and virological outcomes at 12 months, discontinuations, adverse events (AEs) and serious adverse events (SAEs) were described. Follow-up was censored at ETR discontinuation, death or last visit. Results 177 children ever received ETR. At ETR start, median [IQR] age was 15 [12,16] years, CD4 count 480 [287, 713] cells/mm3, 70% had exposure to ≥3 ART classes and 20% had viral load (VL) <50 copies/mL. 95% received ETR in combination with ≥1 potent drug class, mostly protease inhibitor-based regimens. Median time on ETR was 24 [7, 48] months. Amongst those on ETR at 12 months ( n=141), 69% had VL<50 copies/mL. Median CD4 increase since ETR start ( n=83) was 147 [16, 267] cells/mm3. Overall, 81 (46%) discontinued ETR by last follow-up. Median time to discontinuation was 23 [8, 47] months. Common reasons for discontinuation were treatment simplification (19%), treatment failure (16%) and toxicity (12%). Eight children (5%) had AEs causally associated with ETR, all dermatological/hypersensitivity reactions. Two were SAEs, both Stevens–Johnson Syndrome in children on regimens containing ETR and darunavir and were causally related to either drugs; both resolved following ART discontinuation. Conclusion Children receiving ETR were predominantly highly treatment-experienced, over two-thirds were virally suppressed at 12 months.
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| 11. |
- Niang, S., et al.
(author)
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Accumulation of Positrons from a LINAC Based Source
- 2020
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In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 164-166
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Journal article (peer-reviewed)abstract
- The GBAR experiment aims to measure the gravitational acceleration of antihydrogen (H) over bar. It will use (H) over bar (+) ions formed by the interaction of antiprotons with a dense positronium cloud, which will require about 1010 positrons to produce one (H) over bar (+). We present the first results on the positron accumulation, reaching 3.8 +/- 0.4x10(8) e(+) collected in 560 s.
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| 12. |
- Nosach, L.V, et al.
(author)
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Gas-phase crosslinking of the lignin on the nanoscale fumed silica surface
- 2021
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In: PHYSICS AND CHEMISTRY OF SOLID STATE. - : Vasyl Stefanyk Precarpathian National University. - 1729-4428 .- 2309-8589. ; 22:4, s. 724-728
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Journal article (peer-reviewed)abstract
- A method for the polymerization modification of nanoscale fumed silica by crosslinking a lignin layer adsorbed on a nanosilica surface under a gas dispersion medium is described. A mixture of phenol and formaldehyde in the presence of HCl proved to be the most effective crosslinking agent. It has been suggested that the crosslinking of lignin molecules occurs by a mechanism similar to the production of phenol formaldehyde resins.
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| 14. |
- Karkin, A. E., et al.
(author)
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Monitoring an insulator-metal transition in icosahedral AlPdRe by neutron irradiation
- 2002
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:9
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Journal article (peer-reviewed)abstract
- The intrinsic disorder effect on the electrical resistivity and magnetoresistance (MR) of icosahedral AlPdRe is studied by use of high-energy neutron irradiation. The icosahedral phase is preserved under irradiation with a decrease of x-ray peak intensity and volume of the coherent icosahedral phase. An insulator-metal transition, as observed in the MR, can be driven by the irradiation and is monitored by the resistance ratio R[=rho(4.2 K)/rho(295 K)]. The relation of MR vs R was found to be similar for samples of a widely different history.
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| 15. |
- Murin, Yu., et al.
(author)
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A detector system for studying nuclear reactions relevant to Single Event Effects
- 2007
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 578:2, s. 385-398
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Journal article (peer-reviewed)abstract
- We describe a device to study reactions relevant for the Single Event Effect (SEE) in microelectronics by means of 200A and 300AMeV, inverse kinematics, Si + H and Si + D reactions. The work is focused on the possibility to measure Z = 2-14 projectile fragments as efficiently as possible. During commissioning and first experiments the fourth quadrant of the CELSIUS storage ring acted as a spectrometer to register fragments in two planes of Si strip detectors in the angular region 0 degrees-0.6 degrees. A combination of ring-structured and sector-structured Si strip detector planes operated at angles 0.6 degrees-1.1 degrees. For specific event tagging a Si+ phoswich scintillator wall operated in the range 3.9 degrees-11.7 degrees and Si Delta E-E telescopes of CHICSi type operated at large angles.
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| 16. |
- Voronin, A.Yu., et al.
(author)
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Resonance spectroscopy of gravitational states of antihydrogen
- 2014
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In: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 228:1-3, s. 133-139
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Journal article (peer-reviewed)abstract
- We study a method to induce resonant transitions between antihydrogen (H) quantum states above a material surface in the gravitational field of the Earth. The method consists in applying a gradient of magnetic field which is temporally oscillating with the frequency equal to a frequency of a transition between gravitational states of antihydrogen. Corresponding resonant change in a spatial density of antihydrogen atoms can be measured as a function of the frequency of applied field. We estimate an accuracy of measuring antihydrogen gravitational states spacing and show how a value of the gravitational mass of the H atom can be deduced from such a measurement.
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