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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Electron beam test of the large area Mu2e calorimeter prototype

The Mu2e calorimeter consists of 1348 pure CsI crystals coupled to two large area UV-extended Silicon Photomultipliers (SiPMs) organized in two separate annular disks. An intense R&D phase has been pursued to check if this configuration satisfies the Mu2e requirements. In May 2017, a dedicated test has been performed at the Beam Test Facility (BTF) in Frascati (Italy) where the large calorimeter prototype (Module-0) has been exposed to an electron beam in the energy range between 60 and 120 MeV. The prototype consists of 51 crystals, each one readout by two Mu2e SiPMs. We present results for timing and energy resolution both for electrons at normal incidence (0°) and at a grazing impact angle (50°) more similar to the experiment configuration. At 100 MeV, an energy resolution of 5.4% (7.4%) at normal (grazing) incidence has been achieved in good agreement with Monte Carlo expectation. In the same energy range, a time resolution of ~XX ps (~YY ps) has been measured at normal incidence with 1 GHz (250 MHz) sampling rate. Dependence of time and energy resolutions as a function of beam energy and impinging angle are also presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Towards the construction of the Mu2e electromagnetic calorimeter at Fermilab

Mu2e will search for the Charge Lepton Flavor Violating (CLFV) conversion of a muon into an electron in the field of a nucleus. A clean discovery signature is provided by the mono-energetic conversion electron (E e = 104.96 MeV). If no events are observed, Mu2e will set a limit on the ratio between the conversion and the nuclear capture rate below 3 × 10$^{-17}$ (at 90% C.L.). In order to confirm that the observed candidate is an electron, the calorimeter resolution requirements are to provide E res < 10%, T res < 500 ps for 100 MeV electrons while working in vacuum and in a high radiation environment and high magnetic field. The calorimeter is made of two annular aluminum disks, each one filled with 674 pure CsI crystals read out by SiPMs. A sophisticated mechanics and cooling system has been developed to support the crystals and cool the sensors. Radiation hard analog and fast digital electronics have been developed. In this paper the QC tests performed on the produced components and the construction status are reported, as well as the results obtained on the large size prototype with test beam data and at a cosmic ray test stand.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

COHERENT Experiment: current status

The COHERENT Collaboration is realizing a long term neutrino physics research program. The main goals of the program are to detect and study elastic neutrino-nucleus scattering (CEνNS). This process is predicted by Standard Model but it has never been observed experimentally because of the very low energy of the recoil nucleus. COHERENT is using different detector technologies: CsI[Na] and NaI scintillator crystals, a single-phase liquid Ar and a Ge detectors. The placement of all the detector setups is in the basement of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The current status of the COHERENT experimental program is presented.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Design, status and test of the Mu2e crystal calorimeter

The Mu2e experiment at Fermilab searches for the charged-lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. The dynamics of such a process is well modeled by a two-body decay, resulting in a monoenergetic electron with an energy slightly below the muon rest mass (104.967 MeV). The calorimeter of this experiment plays an important role to provide excellent particle identification capabilities and an online trigger filter while aiding the track reconstruction capabilities. The baseline calorimeter configuration consists of two disks each made with ~700 undoped CsI crystals read out by two large area UV-extended Silicon Photomultipliers. Furthermore, these crystals match the requirements for stability of response, high resolution and radiation hardness. In this paper we present the final calorimeter design.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

The calorimeter of the Mu2e experiment at Fermilab

Here, the Mu2e experiment at Fermilab looks for Charged Lepton Flavor Violation (CLFV) improving by 4 orders of magnitude the current experimental sensitivity for the muon to electron conversion in a muonic atom. A positive signal could not be explained in the framework of the current Standard Model of particle interactions and therefore would be a clear indication of new physics. In 3 years of data taking, Mu2e is expected to observe less than one background event mimicking the electron coming from muon conversion. Achieving such a level of background suppression requires a deep knowledge of the experimental apparatus: a straw tube tracker, measuring the electron momentum and time, a cosmic ray veto system rejecting most of cosmic ray background and a pure CsI crystal calorimeter, that will measure time of flight, energy and impact position of the converted electron. The calorimeter has to operate in a harsh radiation environment, in a 10 -4 Torr vacuum and inside a 1 T magnetic field. The results of the first qualification tests of the calorimeter components are reported together with the energy and time performances expected from the simulation and measured in beam tests of a small scale prototype.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Components Qualification for a Possible use in the Mu2e Calorimeter Waveform Digitizer

The Mu2e experiment at Fermilab searches for the charged flavor violating conversion of a muon into an electron in the Coulomb field of a nucleus. The detector consists of a straw tube tracker and a CSI crystal electromagnetic calorimeter, both housed in a superconducting solenoid. Both the front-end and the digital electronics, located inside the cryostat, will be operated in vacuum under a 1 T magnetic field, having to sustain the high flux of neutrons and ionizing particles coming from the muons stopping target. These harsh experimental conditions make the design of the calorimeter waveform digitizer quite challenging. All the selected commercial devices must be tested individually and qualified for radiation hardness and operation in high magnetic field. At the moment the expected particles flux and spectra at the digitizers location are not completely simulated and we are using initial rough estimates to select the components for the first prototype. We are gaining experience in the qualification procedures using the selected components but the choice will be frozen only when dose and neutron flux simulations will be completed. The experimental results of the first qualification campaign are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

The Mu2e crystal calorimeter

The Mu2e Experiment at Fermilab will search for coherent, neutrino-less conversion of negative muons into electrons in the field of an Aluminum nucleus, μ - + Al → e - +Al. Data collection start is planned for the end of 2021. The dynamics of such charged lepton flavour violating (CLFV) process is well modelled by a two-body decay, resulting in a mono-energetic electron with an energy slightly below the muon rest mass. If no events are observed in three years of running, Mu2e will set an upper limit on the ratio between the conversion and the capture rates R μe = μ - + A(Z,N) → e - +A(Z,N)/μ - + A(Z,N) → ν μ - +A(Z-1,N) of ≤ 6 ×10 -17 (@ 90% C.L.). This will improve the current limit of four order of magnitudes with respect to the previous best experiment. Mu2e complements and extends the current search for μ → e γ decay at MEG as well as the direct searches for new physics at the LHC . The observation of such CLFV process could be clear evidence for New Physics beyond the Standard Model. Given its sensitivity, Mu2e will be able to probe New Physics at a scale inaccessible to direct searches at either present or planned high energy colliders. To search for the muon conversion process, a very intense pulsed beam of negative muons (~ 10 10 μ/ sec) is stopped on an Aluminum target inside a very long solenoid where the detector is also located. The Mu2e detector is composed of a straw tube tracker and a CsI crystals electromagnetic calorimeter. An external veto for cosmic rays surrounds the detector solenoid. In 2016, Mu2e has passed the final approval stage from DOE and has started its construction phase. As a result, an overview of the physics motivations for Mu2e, the current status of the experiment and the required performances and design details of the calorimeter are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Construction status of the Mu2e crystal calorimeter

The Mu2e experiment at Fermilab will search for the charged-lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities and a fast online trigger filter, while aiding the track reconstruction capabilities. Calorimeter requirements are to provide a large acceptance for 0~10 MeV electrons and reach: i) a time resolution better than 0.5 ns; ii) an energy resolution better than 10%; and iii) a position resolution of 1 cm. The calorimeter consists of two disks, each one made of 674 pure CsI crystals. Each crystal is readout by two large area 2×3 arrays of UV-extended SiPMs of 6×6 mm2 dimensions. A large scale prototype (Module-0) has been tested at an electron beam. We report here the tests done to finalize the calorimeter design, the results obtained with Module-0 and the status of production. At this time, the performance characteristics of 85% of the crystals and all of the SiPMs have been measured. The calorimeter engineering drawings have been completed and the large mechanical components are under fabrication. Analog and digital electronics have been prototyped and tested with irradiation dose. Their serial production is being organized. The calorimeter assembly phase is planned for mid-2020.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Development, construction and tests of the Mu2e electromagnetic calorimeter mechanical structures

The “muon-to-electron conversion” (Mu2e) experiment at Fermilab will search for the charged lepton flavour violating neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the unambiguous evidence of the existence of physics beyond the standard model. Mu2e detectors comprise a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. In particular, the calorimeter provides excellent electron identification, a fast calorimetric online trigger, and complementary information to aid pattern recognition and track reconstruction. The detector has been designed as a state-of-the-art crystal calorimeter and employs 1348 pure Cesium Iodide (CsI) crystals readout by UV-extended silicon photosensors and fast front-end and digitization electronics. A design consisting of two identical annular matrices (named “disks”) positioned at the relative distance of 70 cm downstream the aluminum target along the muon beamline satisfies the Mu2e physics requirements. The hostile Mu2e operational conditions, in terms of radiation levels (total expected ionizing dose of 12 krad and a neutron fluence of 5 × 10$^{10}$ n/cm$^{2}$ @ 1 MeV$_{eq}$ (Si)/y), magnetic field intensity (1 T) and vacuum level (10$^{-4}$ Torr) have posed tight constraints on scintillating materials, sensors, electronics and on the design of the detector mechanical structures and material choice. The support structure of each 674 crystal matrix is composed of an aluminum hollow ring and parts made of open-cell vacuum-compatible carbon fiber. The photosensors and front-end electronics for the readout of each crystal are inserted in a machined copper holder and make a unique mechanical unit. The resulting 674 mechanical units are supported by a machined plate of vacuum-compatible plastic material. The plate also integrates the cooling system made of a network of copper lines flowing a low temperature radiation-hard fluid and placed in thermal contact with the copper holders to constitute a low resistance thermal bridge. The data acquisition electronics are hosted in aluminum custom crates positioned on the external lateral surface of the disks. The crates also integrate the electronics cooling system as lines running in parallel to the front-end system. In this paper we report on the calorimeter mechanical structure design, the mechanical and thermal simulations that have determined the design technological choices, and the status of component production, quality assurance tests and plans for assembly at Fermilab.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Monitoring the SNS basement neutron background with the MARS detector

Here, we present the analysis and results of the first dataset collected with the MARS neutron detector deployed at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) for the purpose of monitoring and characterizing the beam-related neutron (BRN) background for the COHERENT collaboration. MARS was positioned next to the COH-CsI coherent elastic neutrino-nucleus scattering detector in the SNS basement corridor. This is the basement location of closest proximity to the SNS target and thus, of highest neutrino flux, but it is also well shielded from the BRN flux by infill concrete and gravel. Furthermore, these data show the detector registered roughly one BRN per day. Using MARS' measured detection efficiency, the incoming BRN flux is estimated to be 1.20 ± 0.56 neutrons/m 2 /MWh for neutron energies above ~3.5 MeV and up to a few tens of MeV. We compare our results with previous BRN measurements in the SNS basement corridor reported by other neutron detectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Development and construction status of the Mu2e electromagnetic calorimeter mechanical structures

Abstract The Mu2e experiment at Fermilab will search for the CLFV neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the evidence of physics beyond the Standard Model. Mu2e comprises a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter provides electron identification, a fast trigger and aids track reconstruction. It is a state-of-the-art crystal calorimeter and employs 1340 pure CsI crystals readout by UV-extended SiPM and fast electronics. The design consists of two identical annular disks positioned at the relative distance of 70 cm downstream the target.The hostile Mu2e conditions (total ionizing dose of 12 krad and a neutron fluence of 5 × 10 10 n/cm 2 @ 1 MeVeq (Si)/y, 1 T magnetic field and vacuum level of 10 −4 Torr) posed tight constraints on the mechanical structures and materials choice. The support structure of the two crystal matrices employs two aluminum hollow rings and parts made of open-cell vacuum-compatible carbon fiber. SiPMs and front-end electronics for each crystal are assembled in one mechanical unit inserted in a machined copper holder. The units are supported by a plate made of vacuum-compatible material. The plate integrates the cooling system made of a network of copper lines flowing a low temperature fluid and placed in thermal contact with the copper holders. The DAQ is hosted in aluminum crates positioned on the lateral surface of the disks. The crates also integrate the DAQ electronics cooling system. We review the constraints on the calorimeter structures design, the development of all the structural components, including the simulations that have determined the materials and technological choices and the specifications of the cooling station, components production and quality assurance tests, the procedures for detector assembly, transportation and installation in the experimental area.

Instruments & Instrumentation↗
DOE OSTI2025

Identification of Prompt Proton Emission in $N = Z - 1$ 61 Ga: Isospin Symmetry at the Limit of Nuclear Binding

Excited states in the proton drip line nucleus 61 Ga were populated via the fusion-evaporation reaction 24 Mg ⁢( 40 Ca, 𝑝⁢2⁢𝑛)⁢ 61 Ga. The experimental setup at Argonne National Laboratory comprised a novel combination of the Gammasphere array with two CD-shaped double-sided Si-strip detectors inside the Microball CsI(Tl) charged-particle detection array, as well as the Neutron-Shell liquid scintillators and the Fragment Mass Analyzer. Owing to the setup’s unprecedented in-beam proton spectroscopy and tracking capabilities, a coincidence between a 957.6(5)-keV 𝛾 ray and a 1.876(24)-MeV proton line was observed, which identifies the quasibound proton 𝜋⁢𝑔 9/2 single-particle state in 61 Ga at 𝐸 𝑥 = 2150⁢(34) keV. This probes isospin symmetry at the limit of nuclear binding by providing a unique challenge for the shell-model interpretation of mirror nuclei beyond doubly magic 56 Ni .

Hrabar, Yuliia [Lund Univ. (Sweden)] (ORCID:000000↗
DOE OSTI2025

3 He +𝛼 resonances in 7 Be

Resonances in 7 Be which decay into the 3 He+α exit channel have been measured with improved precision using preexisting data sets. The energy and width of the J π =7/2 - state have been extracted from an invariant-mass study of projectile-breakup products originating from interactions of an E/A=10.7-MeV 10 C beam on Be and C targets. The excitation energy of this state (from the pole of the S-matrix) is determined to be E*=4.545(6)~MeV, a factor of 8 improvement in precision as compared to the ENSDF value. This improvement is enabled by fine tuning the detector calibrations using calibration resonances in 6 Li, 7 Li, 6 Be, 9 B, and 12 C whose decay energies are known to high precision. The J π =7/2- resonance in 7 Be can now itself be used as a calibration resonance in invariant-mass experiments. This utility is particularly helpful for 3 He energy calibrations of CsI(Tl) detectors which are often used in detector arrays employed for measurements with fast beams. This utility is demonstrated with a data set associated with E/A=70 MeV 7 Be beams which are inelastically excited to the 7/2 - and 5/2 - 1 resonances. Again using the pole of the S-matrix as the definition of the resonance parameters, the fitted excitation energy of the 5/2 - 1 resonance is 6.376(17) MeV, approximately 300 keV lower than the ENSDF value. Finally, its width of 565(4) keV is roughly half of the ENSDF value.

energy levels↗
DOE OSTI2026

High-spin states in 60 Cu and implications for states in the mirror nucleus 60 Ga

High-spin states in 60 Cu are investigated on the basis of reaction-channel-selected 𝛾-ray spectroscopy. Data stem from three experiments that used the same fusion-evaporation reaction at similar beam energies. The Gammasphere 𝛾-ray spectrometer was combined with the Microball CsI(Tl) detector array and sets of liquid-scintillator neutron detectors which allowed us to identify and tag on evaporated light charged particles and neutrons, respectively. A level scheme is proposed which comprises more than 300 𝛾-ray transitions connecting more than 100 excited states. Predictions from cranked Nilsson-Strutinsky calculations describe the observed high-spin collective structures in 60 Cu. Predictions of shell-model calculations are probed with a suite of low- to medium-spin states of both parities. Taking into account isospin-symmetry-breaking terms in these calculations, a case study of the yrast line of the weakly bound mirror nucleus 60 Ga is presented.

Rudolph, Dirk [Lund University (Sweden)] (ORCID:00↗
DOE OSTI2020

Onset of high-spin rotational bands in the $N = Z$ nucleus 62 Ga

The fusion-evaporation reaction 28 Si + 40 Ca at 122 MeV beam energy was used to populate high-spin states in the odd-odd $N = Z$ nucleus 62 Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array the decay scheme of 62 Ga was extended beyond 10 MeV excitation energy. The onset of band structures was observed. These high-spin rotational states are interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Relative population of states in 21 Mg from few-nucleon removal reactions

Nuclear reactions with intermediate-energy beams in which three, four, and five nucleons are removed are expected to proceed through a combination of nondissipative and statistical processes. In an experiment at the National Superconducting Cyclotron Laboratory, in-beam γ-ray spectroscopy was utilized to study few-nucleon removal reactions from incoming beams of 24 Mg, 25 Al, and 26 Si projectiles to the same reaction product, 21 Mg. Here, new γ-ray transitions and γ-γ coincidences in 21 Mg were established using the CsI(Na) array CAESAR and the inclusive cross section for three-neutron removal from 24 Mg was measured. Significant differences in the relative population of states in 21 Mg from 25 Al compared to 26 Si were observed and found to be correlated with the spins of the 21 Mg states. As a result, this intermediate regime between direct and statistical nucleon removal may have potential as a tool to deliver unique patterns of level populations in fast-beam experiments and alter isomer to ground state ratios in the production of exotic beams.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗