Photo-sensors for a Multi-PMT optical module in KM3NeT Kavatsyuk, O.; Dorosti-Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2011, Letnik:
626
Journal Article
Recenzirano
A deep-sea Neutrino Telescope of at least 1
km
3 size (KM3NeT) is being designed to search for high-energy (1–1000
TeV) neutrinos originating from galactic and extragalactic sources. The detection ...principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter surrounding the telescope. An optical module containing an array of 31 3-in. diameter photomultiplier tubes is a promising alternative to an optical module containing one 10-in. diameter phototube. The single photo-electron response of 3-in. diameter phototubes (Photonis XP53B20 and ETEL 9822B) has been investigated. Phototube characteristics such as the collection efficiency, transit-time spread and peak-to-valley ratio were determined at various positions across the photocathode surface in a remote-controlled 2D scanning system. Results of these investigations are reported and the perspectives to employ the investigated phototube types in the Multi-PMT optical module of the future KM3NeT detector are discussed.
We have used an organic radio-fluorogenic gel to make fixed fluorescent images of the track of an 80 MeV proton pencil beam NB this is not a scintillation effect; rather a small fraction of the ...molecules of the medium are converted permanently from a non-emissive to an emissive form. The spatial resolution of the images is better than 0.1 mm and the cuboid form of the gels allows the track to be viewed along the direction of the beam or transverse to it. The fluorescence diverges and increases in intensity with increasing depth up to the Bragg peak with 80a20% post-peak fall-off in 1.4+/-0.1 mm. From the effect of interposed polystyrene sheets on the proton range in the gel, its water equivalent thickness is determined to be 0.91.
The first 2+ states in 134Ce and 136Nd and the second 2+ state in 136Nd were populated by Coulomb excitation at relativistic energies, and γ-rays were measured using the RISING setup at GSI. For ...134Ce an indication of the excitation to the second 2+ state was observed. This experiment performed for the first time Coulomb excitation to second 2+ states with rare isotope beams at relativistic energies. For 136Nd the B(E2;21+→0+), B(E2;22+→0+), and B(E2;22+→21+) values relative to the previously known B(E2;21+→0+) value for 134Ce are determined as 81(10), 11(3) and 180(92) W.u., respectively. The results are discussed in the framework of geometrical models that indicate pronounced γ-softness in these nuclei.
Multi-PMT optical module for the KM3NeT neutrino telescope Kavatsyuk, O.; Dorosti-Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Letnik:
695
Journal Article
Recenzirano
The future cubic kilometre scale neutrino telescope KM3NeT will employ a novel type of a Digital Optical Module (DOM), developed during the recent FP6 Design Study. A pressure-resistant glass sphere ...hosts 31 photomultiplier tubes (PMTs) of 3-in. diameter, together with all the electronics for high-voltage generation and signal readout. The optical module forms a complete stand-alone detector that is connected to the outside world via a single optical fibre and two copper conductors providing electrical power. The advantages of using multiple small PMTs in the same DOM are the higher quantum efficiency (>30% expected), smaller transit time spread, better two-photon separation capability and directional sensitivity. Moreover, a longer operating lifetime is expected than for large PMTs due to the accumulation of less charge on the anode. In addition, small PMTs are insensitive to the Earth's magnetic field and do not require μ-metal shielding. In order to maximise the detector sensitivity, each PMT will be surrounded by an expansion cone collecting photons that would normally miss the photocathode. Such an expansion cone consists of an aluminium ring filled with silicone gel. An increase in the overall sensitivity, integrated over all angles of incidence, was estimated to be about 27%. Monte-Carlo simulations have shown that a detector configuration with multi-PMT DOMs requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs. Prototype DOMs are currently being built by the KM3NeT consortium.
The first excited 2+ state of 36Ca has been identified by its γ-decay, exploiting the two-step fragmentation technique at the FRS-RISING setup at GSI. This is the heaviest Tz=−2 nucleus in the Segré ...chart in which a γ-decay of an excited state has been observed. A stable beam of 40Ca at 420AMeV impinged on a primary 9Be target. Out of the secondary beam of fragmentation products, 37Ca was separated by the FRS and struck on a second 9Be target at the final focus of the FRS. The energy for the 21+ decay of 36Ca was determined to be 3015(16) keV, which is 276 keV lower than in its T=2 mirror 36S. This mirror energy difference (MED) is discussed in the framework of shell model calculations using a 16O core, the sd shell isospin symmetric interaction USD and experimental single-particle energies from 17O and 17F. The results show that the MED within the sd shell provide a sensitive test for the evolution of the N, Z=14,16 subshell gaps towards the driplines. Especially the N, Z=16 gap is determined by Thomas–Ehrman shift in the A=17, T=1/2 isospin doublet, while Coulomb effects are found to have marginal influence.
The first excited 2+ states in 54,56,58Cr were populated by Coulomb excitation at relativistic energies and γ rays were measured using the RISING setup at GSI. For 56Cr and 58Cr the B(E2,21+→0+) ...values relative to the previously known B(E2) value for 54Cr are determined as 8.7(3.0) and 14.8(4.2) W.u., respectively. The results are consistent with a subshell closure at neutron number N=32 which was already indicated by the higher energy of the 21+ state in 56Cr. Recent large-scale shell model calculations using effective interactions reproduce the trend in the excitation energies, but fail to account for the minimum in the B(E2) values at N=32.
PDF
