Abstract
Since 1984 INFN and University of Pisa scientists performing experiments at Fermilab have been running a two-month summer training program for Italian students at the lab. In 1984 the ...program involved only a few physics students from the University of Pisa, but it was later extended to other INFN groups and to engineering students. Since 2004 the program has been supported in part by the US Department of Energy (DOE) in the frame of an exchange agreement with INFN and has been run by the Cultural Association of Italians at Fermilab (CAIF). In 2007 the Sant’Anna School of Advanced Studies (Pisa) established an agreement with Fermilab to share the cost of four engineering students each year. In the almost 40 years of its history, the program has hosted at Fermilab approximately 550 Italian students from more than 20 Italian universities and from some non-Italian universities. In addition, in the years 2010-2019, with the support of the Italian National Institute of Astrophyics (INAF), the Italian Space Agency (ASI), and CAIF, 30 students were hosted in other US laboratories and universities. The Fermilab training programs spanned from data analysis to design and construction of particle detectors and accelerator components, R/D on superconductive elements, theory of accelerators, and analysis of astrophysical data. At the other US laboratories the offered training was on Space Science. In 2015 the University of Pisa endorsed the program as one of its own Summer Schools. The interns are enrolled as Pisa students for the duration of the internship. They are required to write summary reports published in the Fermilab and University of Pisa web pages. Upon positive evaluation by a University board, students are acknowledged 6 ECTS credits. The entire program is expected to expand further under CAIF management. An agreement has been signed between ASI and CAIF, for ASI to support yearly three two-months fellowships in US space science. In the following we inform on student recruiting, training programs, and final evaluation
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.
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.
Abstract
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.
The Mu2e calorimeter consists of 1348 undoped CsI crystals coupled to two large area UV-extended Silicon Photomultipliers (SiPMs). A modular and custom SiPM layout, a 3×2 matrix of 6×6 mm2 monolithic ...SiPMs, has been developed to satisfy the Mu2e requirements. As well as ensuring the performances needed for the muon-to-electron conversion search, these photosensors have to guarantee a good reliability while operating maintenance-free in the Mu2e hostile environment: any failure can only be replaced during a long technical shut-down scheduled once a year. After testing prototypes from different vendors, we selected Hamamatsu and the final production of about 4000 pieces is now ongoing. A detailed Quality Assurance (QA) program is then mandatory to minimize the risk of an unexpected further degradation in the performances. The QA process for each photosensor includes a first visual inspection and the subsequent characterization of each of its monolithic cells by means of an automatized test station, able to measure the breakdown voltage, the gain and the dark current. For each production batch (∼300 pieces), 5 devices are exposed to a neutron fluency up to ∼1.4×1011 1 MeV (Si) eq. n/cm2; others 15 devices are undergone an accelerated aging in order to verify the Mean Time To Failure (MTTF) of the batch. A summary of the QA and the results for the firsts 4 production batches are presented in the paper.
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.
High bAndwidth coMmercial digitizer for hostile EnvironmenT (HAMLET) Ciolini, R.; Donati, S.; Giusti, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
February 2023, 2023-02-00, Letnik:
1047
Journal Article
Recenzirano
The Mu2e collaboration has developed a digitizer board that samples up to 20 differential signals with a frequency of 200 MHz, 12 bits of resolution, and dynamic range 0–2 V. The digitizer has been ...qualified to operate in the hostile environment of Mu2E. The qualification levels are Total Ionizing Dose of 12 Krad and Neutron fluence of ∼10111 MeVneq/cm2, 1 T magnetic field, level of vacuum of 10−4 Torr. The digitizer has aroused considerable commercial interest, as there are currently no digitizers with similar characteristics on the market. The original Mu2e board cannot be used as is and requires both hardware and firmware changes before entering the market. INFN funded a technology transfer project called HAMLET to support this new design. Additionally, HAMLET collaboration developed also a demonstration application based on an array of SiPM coupled to a scintillating crystal and connected to the digitizer. The demonstrator constitutes a complete and scalable, radiation qualified hardware platform, that can be used in hostile environments.
The Mu2e experiment at Fermilab aims to search for the SM forbidden μ−→e− conversion in Al muonic atoms. The signal signature consists of 104.96 MeV electrons, identified by a straw-tube tracker and ...a crystal calorimeter, made of two annular disks. In order to calibrate the calorimeter disks with minimum ionizing particles (MIP) before the installation, we have realized a Cosmic Ray Tagger (CRT) at Laboratori Nazionali di Frascati (LNF) of INFN. The CRT consists of two planes of eight 2.5×1.5×160 cm3 plastic scintillator (EJ-200) bars, coupled to SiPMs on both edges, so as to estimate longitudinal hit positions from time differences. 3D MIP tracking is achieved by reconstructing hit positions in the two planes, placed above and below the disks, and allows to calibrate the energy response, to align the time offsets, and to study the detector performances dependence along the crystals axis.
The Mu2e experiment at Fermilab will search for the neutrino-less coherent conversion of a muon into an electron in the field of a nucleus. Mu2e detectors comprise a straw tracker, an electromagnetic ...calorimeter and a veto for cosmic rays. The calorimeter employs 1348 Cesium Iodide crystals readout by silicon photo-multipliers and fast front-end, and digitization electronics. The digitization board is named DiRAC (Digitizer ReAdout Controller) and 140 cards are needed for the readout of the full calorimeter. The DiRACs are hosted in crates located on the external surface of calorimeter disks, inside the detector solenoid cryostat and must sustain very high radiation and magnetic field so it was necessary to fully qualify it. Several version of prototypes were validated for operation in a high-vacuum (10−4 Torr) and under a 1T magnetic field. An extensive radiation hardness qualification campaign, carried out with photons, 14 MeV neutron beams, and 200 MeV protons, certified the DiRAC design to sustain doses up to 12 krad, neutron fluences up to ∼10111MeV neq/cm2, and very low occurrences of single-event effects. The qualification campaigns and quality assurance procedures will be reviewed.
The Mu2e calorimeter will employ Readout Units, each made of two Silicon Photomultipliers arrays and two Front End Electronics boards. To calibrate them, we have designed, assembled and put in ...operation an automated Quality Control (QC) station. Gain, collected charge and photon detection efficiency are evaluated for each unit. In this paper, the QC Station is presented, in its hardware and software aspects, summarizing also the tests performed on the ROUs and the first measurement results.
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