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D. A. Fink et al.; 15 págs.; 17 figs.; 3 tabs.; Open Access funded by Creative Commons Atribution Licence 3.0 ; A Laser Ion Source and Trap (LIST) for a thick-target, isotope-separation on-line facility has been implemented at CERN ISOLDE for the production of pure, laser-ionized, radioactive ion beams. It offers two modes of operation, either as an ion guide, which performs similarly to the standard ISOLDE resonance ionization laser ion source (RILIS), or as a more selective ion source, where surface-ionized ions from the hot ion-source cavity are repelled by an electrode, while laser ionization is done within a radiofrequency quadrupole ion guide. The first physics application of the LIST enables the suppression of francium contamination in ion beams of neutron-rich polonium isotopes at ISOLDE by more than 1000 with a reduction in laser-ionization efficiency of only 20. Resonance ionization spectroscopy is performed directly inside the LIST device, allowing the study of the hyperfine structure and isotope shift of 217Po for the first time. Nuclear decay spectroscopy of 219Po is performed for the first time, revealing its half-life, α- to-β-decay branching ratio, and α-particle energy. This experiment demonstrates the applicability of the LIST at radioactive ion-beam facilities for the production and study of pure beams of exotic isotopes. Published by the American Physical Society ; This work was supported by the Bundesministerium für Bildung und Forschung (BMBF, Germany) within the Wolfgang- Gentner programme as well as through the consecutive project fundings of 06Mz9181I, 06Mz7177D, and 05P12UMCIA, by FWO-Vlaanderen (Belgium), by GOA/2010/010 (BOF-KULeuven), by the IUAP-Belgian State Belgian Science Policy (BRIX network P7/12), by the U.K. Science and Technology Facilities Council (STFC), by the European Union within FP7 (ENSAR No. 262010), by the Slovak Research and Development Agency (Contract No. APVV-0105-10), by the Slovak grant agency VEGA, and the Reimei Foundation of JAEA (Contract No. 1/0576/13). T. E. C. was supported by STFC Ernest Rutherford Grant No. ST/J004189/1. ; Peer Reviewed

This paper presents a comprehensive optimisation study to maximise the light collection efficiency of scintillating cube elements used in the SoLid detector. Very short baseline reactor experiments, like SoLid, look for active to sterile neutrino oscillation signatures in the anti-neutrino energy spectrum as a function of the distance to the core and energy. Performing a precise search requires high light yield of the scintillating elements and uniformity of the response in the detector volume. The SoLid experiment uses an innovative hybrid technology with two different scintillators: polyvinyltoluene scintillator cubes and (LiF)-Li-6:ZnS(Ag) screens. A precision test bench based on a Bi-207 calibration source has been developed to study improvements on the energy resolution and uniformity of the prompt scintillation signal of antineutrino interactions. A trigger system selecting the 1 MeV conversion electrons provides a Gaussian energy peak and allows for precise comparisons of the different detector configurations that were considered to improve the SoLid detector light collection. The light collection efficiency is influenced by the choice of wrapping material, the position of the 6LiF:ZnS(Ag) screen, the type of fibre, the number of optical fibres and the type of mirror at the end of the fibre. This study shows that large gains in light collection efficiency are possible compared to the SoLid SM1 prototype. The light yield for the SoLid detector is expected to be at least 52 +/- 2 photo-avalanches per MeV per cube, with a relative non-uniformity of 6 %, demonstrating that the required energy resolution of at least 14 % at 1 MeV can be achieved. ; Agence Nationale de la Recherche grant [ANR-16CE31001803]; Institut Carnot Mines; Region Pays de Loire in France; FWO-Vlaanderen; Vlaamse Herculesstichting in Belgium; Science&Technology Facilities Council (STFC); CNRS/IN2P3; Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme; European Research Council under the European Union's Horizon 2020 Programme (H2020-CoG)/ERC Grant [682474] ; This work was supported by the following funding agencies: Agence Nationale de la Recherche grant ANR-16CE31001803, Institut Carnot Mines, CNRS/IN2P3 and Region Pays de Loire in France and FWO-Vlaanderen and the Vlaamse Herculesstichting in Belgium. The United Kingdom groups acknowledge the support of the Science&Technology Facilities Council (STFC). We are grateful for the early support given by the sub-department of Particle Physics and Merton College at Oxford and High Energy Physics at Imperial College London. We thank also our colleagues, the administrative and technical staffs of the SCK center dot CEN for their invaluable support for this project. Individuals have received support from the FWO-Vlaanderen and the Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme. The STFC Rutherford Fellowship program and the European Research Council under the European Union's Horizon 2020 Programme (H2020-CoG)/ERC Grant Agreement n. 682474.

The SoLid collaboration has developed a new detector technology to detect electron anti-neutrinos at close proximity to the Belgian BR2 reactor at surface level. A 288 kg prototype detector was deployed in 2015 and collected data during the operational period of the reactor and during reactor shut-down. Dedicated calibration campaigns were also performed with gamma and neutron sources. This paper describes the construction of the prototype detector with a high control on its proton content and the stability of its operation over a period of several months after deployment at the BR2 reactor site. All detector cells provide sufficient light yields to achieve a target energy resolution of better than 20%/root E(MeV). The capability of the detector to track muons is exploited to equalize the light response of a large number of channels to a precision of 3% and to demonstrate the stability of the energy scale over time. Particle identification based on pulse-shape discrimination is demonstrated with calibration sources. Despite a lower neutron detection efficiency due to triggering constraints, the main backgrounds at the reactor site were determined and taken into account in the shielding strategy for the main experiment. The results obtained with this prototype proved essential in the design optimization of the final detector. ; Agence Nationale de la Recherche, France [ANR-16 - CE31 - 0018 - 03]; Institut Carnot Mines, France; CNRS/IN2P3 et Region Pays de Loire, France; FWO-Vlaanderen, Belgium; Vlaamse Herculesstichting, Belgium; Science AMP; Technology Facilities Council (STFC), United Kingdom; Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme; STFC Rutherford Fellowship program; European Research Council under the European Union's Horizon Programme (H-CoG)/ERC Grant [682474]; Merton College Oxford; FWO-Vlaanderen ; This work was supported by the following funding agencies: Agence Nationale de la Recherche grant ANR-16 - CE31 - 0018 - 03, Institut Carnot Mines, CNRS/IN2P3 et Region Pays de Loire, France; FWO-Vlaanderen and the Vlaamse Herculesstichting, Belgium; The U.K. groups acknowledge the support of the Science & Technology Facilities Council (STFC), United Kingdom; We are grateful for the early support given by the sub-department of Particle Physics at Oxford and High Energy Physics at Imperial College London. We thank also our colleagues, the administrative and technical staffs of the SCK . CEN for their invaluable support for this project. Individuals have received support from the FWO-Vlaanderen and the Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme; The STFC Rutherford Fellowship program and the European Research Council under the European Union's Horizon 2020 Programme (H2020-CoG)/ERC Grant Agreement n. 682474 (corresponding author); Merton College Oxford.

The next generation of very-short-baseline reactor experiments will require compact detectors operating at surface level and close to a nuclear reactor. This paper presents a new detector concept based on a composite solid scintillator technology. The detector target uses cubes of polyvinyltoluene interleaved with (LiF)-Li-6:ZnS(Ag) phosphor screens to detect the products of the inverse beta decay reaction. A multi-tonne detector system built from these individual cells can provide precise localisation of scintillation signals, making efficient use of the detector volume. Monte Carlo simulations indicate that a neutron capture efficiency of over 70% is achievable with a sufficient number of 6LiF: ZnS( Ag) screens per cube and that an appropriate segmentation enables a measurement of the positron energy which is not limited by gamma-ray leakage. First measurements of a single cell indicate that a very good neutron-gamma discrimination and high neutron detection efficiency can be obtained with adequate triggering techniques. The light yield from positron signals has been measured, showing that an energy resolution of 14%/root E(MeV) is achievable with high uniformity. A preliminary neutrino signal analysis has been developed, using selection criteria for pulse shape, energy, time structure and energy spatial distribution and showing that an antineutrino efficiency of 40% can be achieved. It also shows that the fine segmentation of the detector can be used to significantly decrease both correlated and accidental backgrounds. ; Agence Nationale de la Recherche grant [ANR-16-CE31-0018-03]; Institut Carnot Mines, France; CNRS/IN2P3 et Region Pays de Loire, France; FWO-Vlaanderen, Belgium; Vlaamse Herculesstichting, Belgium; Science AMP; Technology Facilities Council (STFC), United Kingdom; FWO-Vlaanderen; Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme; STFC Rutherford Fellowship program; European Research Council under the European Union's Horizon Programme (H-CoG) / ERC Grant [682474]; Merton College Oxford ; This work was supported by the following funding agencies: Agence Nationale de la Recherche grant ANR-16-CE31-0018-03, Institut Carnot Mines, CNRS/IN2P3 et Region Pays de Loire, France; FWO-Vlaanderen and the Vlaamse Herculesstichting, Belgium; The U.K. groups acknowledge the support of the Science & Technology Facilities Council (STFC), United Kingdom; We are grateful for the early support given by the sub-department of Particle Physics at Oxford and High Energy Physics at Imperial College London. We thank also our colleagues, the administrative and technical staffs of the SCK.CEN for their invaluable support for this project. Individuals have received support from the FWO-Vlaanderen and the Belgian Federal Science Policy Office (BelSpo) under the IUAP network programme; The STFC Rutherford Fellowship program and the European Research Council under the European Union's Horizon 2020 Programme (H2020-CoG) / ERC Grant Agreement n. 682474 (corresponding author); Merton College Oxford.