The near detector ND280 of the long baseline neutrino experiment T2K (JPARC, Japan) will contain three large 5m3 time projection chambers (TPC) for charged particles tracking and identification. ...These TPCs will be the first large TPCs readout by micro pattern gaseous detectors (MPGD). The bulk-Micromegas MPGD is a micro mesh gaseous structure (MicroMeGaS) in which the woven micromesh is embedded on top of the segmented anode plane of the MPGD by use of standard photolithographic techniques. This MPGD was chosen for its performances in terms of gas gain uniformity, energy resolution and space point resolution, and for its capability to efficiently pave large readout surfaces with minimized dead zones. We developed and improved the bulk-micromegas production methods to be suitable for a uniform, cheap and high quality mass production of 34×36cm2 bulk-micromegas modules of 1726 pads. Production of 72 bulk-micromegas modules, for an equivalent total readout surface of 9m2, began in may 2008 at CERN. After the description of a module and its production, we report on the pad per pad calibration with a strong 55Fe X-ray source of the 32 bulk-micromegas produced so far. Gas gain and 5.9keV energy resolution are presented to illustrate their good uniformity within the whole surface of each module (2.8% and 6% r.m.s dispersion, respectively) and their good reproducibility from one module to another (8% and 3% r.m.s, respectively).
The long baseline neutrino experiment T2K has launched the upgrade project of its near detector ND280, crucial to reduce the systematic uncertainty to less than 4%. An essential component of this ...upgrade consists of two new High-Angle TPCs (HA-TPCs), for 3D track reconstruction, momentum measurement and particle identification. These TPCs will be equipped with 32 resistive bulk-micromegas modules. The field cage will be realized with laminated composite panels covered with a kapton foil with copper strips for electric field shaping. The 34x42 cm2 micromegas will use a ∼0.5 MΩ/square Diamond-Like Carbon (DLC) foil to spread the charge over the pad plane, each pad being ∼1 cm2. In summer 2018, we have tested a resistive bulk-micromegas prototype on the Harp TPC cage with the CERN/PS beam with excellent results both for the space point resolution and for dE/dx resolution. We report on the design of the HA-TPCs and the preliminary results of the prototype performances with 0.8 GeV/c particles.
The one-neutron knockout from 52Ca in inverse kinematics onto a proton target was performed at ∼230 MeV/nucleon combined with prompt γ spectroscopy. Exclusive quasifree scattering cross sections to ...bound states in 51Ca and the momentum distributions corresponding to the removal of 1f7/2 and 2p3/2 neutrons were measured. The cross sections, interpreted within the distorted-wave impulse approximation reaction framework, are consistent with a shell closure at the neutron number N=32, found as strong as at N=28 and N=34 in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 1f7/2 and 2p3/2 orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the 2p3/2 orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.
Time projection chambers for the T2K near detectors Abgrall, N.; Andrieu, B.; Baron, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
637, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector ...located 295
km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280
m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator–bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker are used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/NOMAD dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system.
► First large scale time projection chambers with micropattern gas detectors. ► Incorporates new ASIC for electronic readout. ► Includes a pressure equalizing gas system and a photoelectron calibration system. ► Specifications achieved as deduced from neutrino, cosmic, and calibration tests. ► Will play an important role in T2K to measure neutrino oscillations.
Detailed γ-ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. ...Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for 28Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N=20 and N=28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Neutrino oscillation experiments require a precise measurement of the neutrino energy. However, the kinematic detection of the final-state neutron in the neutrino interaction is missing in current ...neutrino oscillation experiments. The missing neutron kinematic detection results in a smaller detected neutrino energy than the true neutrino energy. A novel 3D-projection scintillator tracker, which consists of roughly ten million active cubes covered with an optical reflector, is capable of measuring the neutron kinetic energy and direction on an event-by-event basis using the time-of-flight technique thanks to the fast timing, fine granularity, and high light yield. The $\overline{v}$μ interactions tend to produce neutrons in the final state. By measuring the neutron kinetic energy, the $\overline{v}$μ energy can be reconstructed better, allowing a tighter incoming neutrino flux constraint. This article shows the detector's ability to reconstruct neutron kinetic energy and the $\overline{v}$μ flux constraint achieved by selecting the charged-current interactions without mesons or protons in the final state.
The dineutron correlation is systematically studied in three different Borromean nuclei near the neutron dripline, 11Li, 14Be and 17B, via the (p,pn) knockout reaction measured at the RIBF facility ...in RIKEN. For the three nuclei, the correlation angle between the valence neutrons is found to be largest in the same range of intrinsic momenta, which can be associated to the nuclear surface. This result reinforces the prediction that the formation of the dineutron is universal in environments with low neutron density, such as the surface of neutron-rich Borromean nuclei.
For measuring gamma rays from low energy to high energy and cover the gap between 1 MeV and 300 MeV in space measurements, Time Projection Chambers (TPC) are a promising solution. In order to read ...the data out of these TPCs, one needs a dedicated electronics to be flexible to cover a wide range of detectors types, with a good resolution over a large dynamic range of incoming charges. The ASTRE chip, a radiation tolerant chip for these applications is described in this article. This Application Specified Integrated Circuit (ASIC) permits the amplification, filtering, triggering and analog storage of 512 samples at a flexible sampling frequency up to 100 MHz. The power consumption is less than 10 mW/channel, with 64 channels per ASIC. The charge range of ASTRE is from 120 fC to 10 pC with 4 programmable gains. The filtering supports 16 peaking times (from 60 ns to 8μs). The ASIC can read negative or positive signals and return a multiplicity signal for triggering and selective readout. In addition it has a programmable internal trigger readable with Low Differential Voltage Signal (LVDS) outputs. The chip was fabricated in August 2016 and is under test. The results of this ASIC to Single Event Latchups, made at the Universite Catholique de Louvain (UCL) are detailed below.
MINOS is a new apparatus dedicated to in-beam nuclear structure experiments with low-intensity exotic beams in inverse kinematics at intermediate energies above 150MeV/nucleon. The device is composed ...of a thick liquid-hydrogen target coupled to a compact time projection chamber (TPC) serving as a vertex tracker. Either used for in-beam gamma spectroscopy of bound excited states or invariant-mass spectroscopy of unbound states, MINOS aims at improving the luminosity by a very significant factor compared to standard solid-target material experiments while improving experimental resolutions.
Proton inelastic scattering of 72,74Ni and 76,80Zn ions at energies around 235 MeV/nucleon was performed at the Radioactive Isotope Beam Factory and studied using γ -ray spectroscopy. Angular ...integrated cross sections for direct inelastic scattering to the 2+ 1 and 4+ 1 states were measured. The Jeukenne-Lejeune-Mahaux folding model, extended beyond 200 MeV, was used together with neutron and proton densities stemming from quasiparticle random-phase approximation (QRPA) calculations to interpret the experimental cross sections and to infer neutron to proton matrix element ratios. In addition, coupled-channels calculations with a phenomenological potential were used to determine deformation lengths. For the Ni isotopes, correlations favor neutron excitations, thus conserving the Z = 28 gap. A dominance of proton excitation, on the other hand, is observed in the Zn isotopes, pointing to the conservation of the N = 50 gap approaching 78Ni. These results are in agreement with QRPA and large-scale shell-model calculations.
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