Natochii, A. et al, & Marinas, C. (2023). Measured and projected beam backgrounds in the Belle II experiment at the SuperKEKB collider. Nucl. Instrum. Methods Phys. Res. A, 1055, 168550–21pp.
Abstract: The Belle II experiment at the SuperKEKB electron-positron collider aims to collect an unprecedented data set of 50 ab-1 to study CP-violation in the B-meson system and to search for Physics beyond the Standard Model. SuperKEKB is already the world's highest-luminosity collider. In order to collect the planned data set within approximately one decade, the target is to reach a peak luminosity of 6 x 1035 cm-2 s-1by further increasing the beam currents and reducing the beam size at the interaction point by squeezing the betatron function down to betay* = 0.3 mm. To ensure detector longevity and maintain good reconstruction performance, beam backgrounds must remain well controlled. We report on current background rates in Belle II and compare these against simulation. We find that a number of recent refinements have significantly improved the background simulation accuracy. Finally, we estimate the safety margins going forward. We predict that backgrounds should remain high but acceptable until a luminosity of at least 2.8 x 1035 cm-2 s-1is reached for betay* = 0.6 mm. At this point, the most vulnerable Belle II detectors, the Time-of-Propagation (TOP) particle identification system and the Central Drift Chamber (CDC), have predicted background hit rates from single-beam and luminosity backgrounds that add up to approximately half of the maximum acceptable rates.
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HAWC Collaboration(Abeysekara, A. U. et al), & Salesa Greus, F. (2023). The High-Altitude Water Cherenkov (HAWC) observatory in Mexico: The primary detector. Nucl. Instrum. Methods Phys. Res. A, 1052, 168253–18pp.
Abstract: The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in Mexico at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware.
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AGATA Collaboration(Valiente-Dobon, J. J. et al), Perez-Vidal, R. M., Blasco Miquel, J., Civera, J. V., & Gadea, A. (2023). Conceptual design of the AGATA 2 pi array at LNL. Nucl. Instrum. Methods Phys. Res. A, 1049, 168040–14pp.
Abstract: The Advanced GAmma Tracking Array (AGATA) has been installed at Laboratori Nazionali di Legnaro (LNL), Italy. In this installation, AGATA will consist, at the beginning, of 13 AGATA triple clusters (ATCs) with an angular coverage of 1n,and progressively the number of ATCs will increase up to a 2 pi angular coverage. This setup will exploit both stable and radioactive ion beams delivered by the Tandem-PIAVE-ALPI accelerator complex and the SPES facility. The new implementation of AGATA at LNL will be used in two different configurations, firstly one coupled to the PRISMA large-acceptance magnetic spectrometer and lately a second one at Zero Degrees, along the beam line. These two configurations will allow us to cover a broad physics program, using different reaction mechanisms, such as Coulomb excitation, fusion-evaporation, transfer and fission at energies close to the Coulomb barrier. These setups have been designed to be coupled with a large variety of complementary detectors such as charged particle detectors, neutron detectors, heavy-ion detectors, high-energy gamma-ray arrays, cryogenic and gasjet targets and the plunger device for lifetime measurements. We present in this paper the conceptual design, characteristics and performance figures of this implementation of AGATA at LNL.
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Mendoza, E., Alcayne, V., Cano-Ott, D., Gonzalez-Romero, E., Martinez, T., de Rada, A. P., et al. (2023). Neutron capture measurements with high efficiency detectors and the Pulse Height Weighting Technique. Nucl. Instrum. Methods Phys. Res. A, 1047, 167894–16pp.
Abstract: Neutron capture cross section measurements in time-of-flight facilities are usually performed by detecting the prompt 7-rays emitted in the capture reactions. One of the difficulties to be addressed in these measurements is that the emitted 7-rays may change with the neutron energy, and therefore also the detection efficiency. To deal with this situation, many measurements use the so called Total Energy Detection (TED) technique, usually in combination with the Pulse Height Weighting Technique (PHWT). With it, it is sought that the detection efficiency depends only on the total energy of the 7-ray cascade, which does not vary much with the neutron energy. This technique was developed in the 1960s and has been used in many neutron capture experiments to date. One of the requirements of the technique is that 7-ray detectors have a low efficiency. This has meant that the PHWT has been used with experimental setups with low detection efficiencies. However, this condition does not have to be fulfilled by the experimental system as a whole. The main goal of this work is to show that it is possible to measure with a high efficiency detection system that uses the PHWT, and how to analyze the measured data.
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An, L., Auffray, E., Betti, F., Dall'Omo, F., Gascon, D., Golutvin, A., et al. (2023). Performance of a spaghetti calorimeter prototype with tungsten absorber and garnet crystal fibres. Nucl. Instrum. Methods Phys. Res. A, 1045, 167629–7pp.
Abstract: A spaghetti calorimeter (SPACAL) prototype with scintillating crystal fibres was assembled and tested with electron beams of energy from 1 to 5 GeV. The prototype comprised radiation-hard Cerium-doped Gd3Al2Ga3O12 (GAGG:Ce) and Y3Al5O12 (YAG:Ce) embedded in a pure tungsten absorber. The energy resolution root was studied as a function of the incidence angle of the beam and found to be of the order of 10%/ E a 1%, in line with the LHCb Shashlik technology. The time resolution was measured with metal channel dynode photomultipliers placed in contact with the fibres or coupled via a light guide, additionally testing an optical tape to glue the components. Time resolution of a few tens of picosecond was achieved for all the energies reaching down to (18.5 +/- 0.2) ps at 5 GeV.
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