Contents lists available atScienceDirect
Radiation Physics and Chemistry
journal homepage:www.elsevier.com/locate/radphyschemIrradiation aging of the CMS Drift Tube muon detector
D.D. Redondo Ferrero
b,∗, G. Abbiendi
a, J. Alcaraz Maestre
b, A. Álvarez Fernández
b,
B. Álvarez González
c, N. Amapane
d,e, I. Bachiller
b, J.M. Barcala
b, L. Barcellan
f, C. Battilana
a,g,
M. Bellato
f, G. Bencze
h, M. Benettoni
f, N. Beni
i, A. Benvenuti
a,1, L.C. Blanco Ramos
b, A. Boletti
f,
A. Bragagnolo
f, J.A. Brochero Cifuentes
b, V. Cafaro
a, A. Calderon
j, E. Calvo
b, A. Cappati
d,e,
R. Carlin
f, C.A. Carrillo Montoya
b, S. Caturan
f, F.R. Cavallo
a, J.M. Cela Ruiz
b, M. Cepeda
b,
M. Cerrada
b, B. Chazin Quero
j, P. Checchia
f, L. Ciano
f, N. Colino
b, D. Corti
f, G. Cotto
d,e,
J. Cuevas
c, M. Cu
ffiani
a,g, G.M. Dallavalle
a, D. Dattola
d, B. De La Cruz
b, P. De Remigis
d,
J.F. de Trocóniz
k, C. Erice Cid
c, C.F. Bedoya
b, F. Fabbri
a, A. Fanfani
a,g, D. Fasanella
a,g,p,
P. Fernandez Manteca
j, J. Fernández Menéndez
c, J.P. Fernández Ramos
b, S. Folgueras
c,
M.C. Fouz
b, D. Francia Ferrero
b, J. García Romero
b, F. Gasparini
f, U. Gasparini
f, V. Giordano
a,
F. Gomez Casademunt
j, F. Gonella
f, I. González Caballero
c, J.R. González Fernández
c,
O. González López
b, S. Gosh
l, S. Goy López
b, A. Gozzelino
f, A. Griggio
f, G. Grosso
f, C. Guandalini
a,
L. Guiducci
a,g, M. Gulmini
e,m, T. Hebbeker
l, C. Heidemann
l, J.M. Hernández
b, K. Hoepfner
l,
F. Iemmi
a,g, R. Isocrate
f, M.I. Josa
b, B. Kiani
d,e, S. Lacaprara
f, S. Lo Meo
a,o, S. Marcellini
a,
M. Margoni
f, J. Marín
b, C. Mariotti
d, I. Martín Martín
b, J.J. Martínez Morales
b,
C. Martínez Rivero
j, S. Maselli
d, G. Masetti
a, A.T. Meneguzzo
f, M. Merschmeyer
l, G. Mocellin
l,
L. Modenese
f, A. Molinero
b, J. Molnar
i, F. Montecassiano
f, D. Moran
b, J.J. Navarrete
b,
F. Navarria
a,g, Á. Navarro Tobar
b, J.C. Oller
b, M. Passaseo
f, J. Pazzini
f, M. Pegoraro
f,
J. Puerta Pelayo
b, M. Pelliccioni
d, B. Philipps
l, J. Piedra Gomez
j, G.L. Pinna Angioni
d,e,
N. Pozzobon
f, M. Presilla
f, C. Prieels
j, F. Primavera
a,g, J.C. Puras Sánchez
b, I. Redondo
b,
H. Reithler
l, T. Rodrigo
j, V. Rodríguez Bouza
c, J. Roemer
l, P. Ronchese
f, R. Rossin
f, F. Rotondo
d,
T. Rovelli
a,g, S.Sánchez Cruz
c, S.Sánchez Navas
b, J. Sastre
b, L. Scodellaro
j, F. Simonetto
f,
M.S. Soares
b, A. Staiano
d, Z. Szillasi
i, D.F. Teyssier
i, N. Toniolo
e,m, E. Torassa
f, D. Trocino
d,
B. Ujvari
n, S. Ventura
f, R. Vilar Cortabitarte
j, J. Vizan Garcia
j, M. Zanetti
f, F.P. Zantis
l, G. Zilizi
n,
P. Zotto
faINFN Sezione di Bologna, Italy
bCentro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain
cUniversidad de Oviedo, Instituto Universitario de Ciencias y Tecnologías Espaciales de Asturias (ICTEA), Spain dINFN Sezione di Torino, Italy
eUniversità di Torino, Italy
fINFN Sezione di Padova, Università di Padova, Italy gUniversità di Bologna, Italy
hWigner Research Centre for Physics, Hungary iInstitute of Nuclear Research ATOMKI, Hungary
jInstituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Spain kUniversidad Autónoma de Madrid (UAM), Spain
lRWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany mLaboratori Nazionali di Legnaro dell’INFN, Italy
nInstitute of Physics, University of Debrecen, Hungary
oItalian National Agency for New Technologies, Energy and Sustainable Economic development, Bologna, Italy pCERN, Switzerland
https://doi.org/10.1016/j.radphyschem.2020.108747
Received 5 August 2019; Received in revised form 7 January 2020; Accepted 1 February 2020
∗Corresponding author.
E-mail address:daviddaniel.redondo@ciemat.es(D.D.R. Ferrero).
1Deceased.
Available online 04 February 2020
0969-806X/ © 2020 Elsevier Ltd. All rights reserved.
A R T I C L E I N F O Keywords: Particle physics Accelerator physics Instrumentation Colliders Muon detectors
Radiation dose measurements LHC HL-LHC upgrade CMS DT Radiation aging A B S T R A C T
During the High Luminosity LHC, the Drift Tube chambers installed in the CMS detector need to operate with an integrated dose ten times higher than expected at the LHC due to the increase in integrated luminosity from 300 fb-1to 3000 fb-1. Irradiations have been performed to assess the performance of the detector under such
conditions and to characterize the radiation aging of the detector. The presented analysis focuses on the be-haviour of the high voltage currents and the dose measurements needed to extrapolate the results to High Luminosity conditions, using data from the photon irradiation campaign at GIF++ in 2016 as well as the efficiency analysis from the irradiation campaign started in 2017. Although the single-wire loss of high voltage gain observed of 70% is very high, the muon reconstruction efficiency is expected to decrease less than 20% during the full duration of High Luminosity LHC in the areas under highest irradiation.
1. Introduction
With the approval of the High Luminosity LHC (HL-LHC) project (Apollinari et al., 2015), the CMS detectors need to plan for operation until 2035 with ten times the integrated dose expected for LHC. In order to study the performance of these detectors under such an integrated dose, tests are being conducted at the Gamma Irradiation Facility (GIF ++) at CERN (Guida, 2016).
1.1. Effects of radiation on gaseous detectors
As can be seen in the literature, performance decrease in gaseous detectors has been observed under conditions of irradiation (Sauli, 2014). The electron avalanche conditions, together with the ionizing radiation, enable the formation of deposits on the surface of the anode wire. The degradation of the detector is typically caused by a poly-merization process that produces a hydrocarbon and silicon deposit on the anode, the origin of these materials is expected to be the gas mix-ture and the elements used to build the drift cell. This deposit, which can be observed in Fig. 1after one of the irradiation campaigns de-scribed in this paper, increases the diameter of the wire with an in-sulated coating that reduces the amount of electrons that are generated due to amplification, what is known as gain of the detector. The speed at which the detector loses performance is known to be proportional to the gain.
1.2. The Drift Tube chamber
The Drift Tube (DT) chamber (The CMS Collaboration, 1997) is a gas detector designed to identify, trigger and measure with precision (240μm per wire for perpendicular tracks) the trajectory of muons that are generated in LHC collisions in the barrel region of the CMS detector. The basic detector element is a rectangular drift cell delimited by alu-minium beams on the sides where cathodes are located and alualu-minium plates on the top and bottom, it has a transversal size of 4.2 cm × 1.3 cm and a variable length between 2 and 4 m, depending on the position in CMS. Aluminium strip electrodes shape the electric field to achieve almost constant drift velocity along the cell as shown in Fig. 2. Inside each of these cells there is a gold-plated 50μm steel wire that acts as the anode and they arefilled with an 85/15% Ar/CO2 gas mixture at 3 mbar higher than ambient pressure. The standard oper-ating voltage for the anode, cathode and strips are +3600 V,−1200 V and +1800 V respectively. These conditions give a nominal gain with an order of magnitude of 105and an expected detection efficiency above
90%, although, since it is a redundant system, detection efficiencies in the order of 70% provide still good muon reconstruction.
The cells are grouped in layers, sharing the power distribution. Each DT chamber is divided in three superlayers (SL1, SL2 and SL3) which
contain four layers each (L1, L2, L3 and L4), staggered by half a cell to allow better muon track reconstruction.
The DT chambers have been built out of materials that were tested for outgassing pollutants (Conti, 2001). They were considered safe for LHC operation radiation levels. In view of operation under HL-LHC, further tests need to be performed.
The central part of CMS, called the Yoke Barrel (YB), is divided in five wheels, ranging from +2 to −2 as can be seen inFig. 3. Each of these wheels is subdivided in 12 azimuthal divisions called sectors, with 4 chambers each at increasing radius and separated among them by the steel of the magnet return yoke. Each of these layers of chambers is named MB (Muon Barrel) from MB1 to MB4. The maximum dose during LHC collisions is measured in the MB1 station of the±2 wheels, thus the studies are done for that station. A further description can be found in (The CMS Collaboration, 1997).
1.3. The Gamma Irradiation Facility (GIF++)
The GIF++ (Guida, 2016) facility is used to irradiate the DT chambers, as well as other muon detectors, and assess the effects of the ionizing radiation on the detector performance. The facility provides a high activity 137 Cs source emitting 662 keV photons and a high energy muon beam coming from the CERN Super Proton Synchrotron (SPS).
The dose rate received by the chamber is regulated by a series of attenuationfilters that can be controlled remotely. The high intensity of the GIF++ source allows to perform accelerated irradiation tests,
Fig. 1. Microscopy analysis of an irradiated gold-plated steel wire with deposit (left) after an irradiation campaign, with diameter 65μm and a clean wire (right), of diameter 56μm. The deposit layer is thus about 4.5 μm thick. (For interpretation of the references to colour in thisfigure legend, the reader is referred to the Web version of this article.)
however, to minimize the extrapolation factors, the intensity of the source was regulated to not surpass more than ten times the dose rate expected at HL-LHC. Under these conditions the HL-LHC dose would be obtained after 138 days of irradiation at the chamber location in the GIF++ bunker.
The muon beam allows the characterization of the detection e ffi-ciency with and without background irradiation provided by the source, being quite a good model of HL-LHC conditions. Scintillators provide trigger on the beam muons, while the chamber has also auto-trigger capability, which is used for cosmic muons data-taking during periods without beam.
A DT chamber was placed in the D4 position depicted inFig. 4 to-gether with the simulation of the photonflux inside the GIF++ bunker (Pfeiffer et al., 2017). The chamber was provided with all the necessary services for operation: gas with the same conditions as CMS, cooling and high voltage. A real-time monitoring system was set to record the values of the current in the anode and the dose absorbed by the chamber.
The results from two irradiation campaigns will be presented. The first campaign started in 2016 and lasted 15 days with the detector
completely switched on. During the 2017 campaign a new chamber was installed at GIF++, this time only two layers of the DT chamber were on during irradiation, while the rest were off, so the aging would only affect a small part of the detector. The layers that were not irradiated were used as a scope to reconstruct the muon tracks and characterize the detection efficiency. This campaign lasted two years with 172 days of total irradiation.
2. Dose measurements
One of the critical parameters to obtain during an irradiation campaign is a precise measurement of the dose rate and of the in-tegrated dose, since this is the variable that would be used to extra-polate to the expected integrated luminosity values for the HL-LHC. The reference for the extrapolation will be the chambers installed in the external wheels in the station closest to the interaction point (YB±2 MB1).
The characterization of the dose deposited on the chamber has been performed using different devices with the intention of cross-checking the measurements:
•
A RADMON (Fernandez-Hernando et al., 2004) radiation sensing transistor.•
The proportional chambers RAMSES (Segura Millan et al., 2005) and REMUS (Ledeul et al., 2015).•
A Geiger-Müller tube portable dosimeter (Automess 6150 AD) (Automation und Messtechni, 2008).The proportional chambers and the portable dosimeter had con-sistent measurements throughout the campaign, the RADMON mea-surements were ultimately not conclusive and were not used in the analysis.
The majority of dose measuring devices are designed with radi-ological protection in mind and therefore measure equivalent dose (Sv), which quantifies the health effects on the human body. The system under study is not biological in nature so, in order to correlate with other studies and measurements, a conversion to absorbed dose (mGy) is needed.
With simulation data of the photon energy distribution from (Pfeiffer et al., 2017) we can calculate the percentage of total flux distribution for energy intervals between 0 and 662 keV. Multiplying the conversion factors issued by the ICRP (Publication 74 and Conv, 1996) for each energy bin with the percentage of photonflux irra-diating the D4 position in the bunker, a conversion factor of 1.34 Sv/Gy can be estimated for the total of the irradiation spectra (Table 1).
Further corrections need to be applied in order to get a precise measurement of the dose. There are two factors that affect the dose characterization, the distance between the sensor and the chamber and the inhomogeneous irradiationfield due to other detectors placed be-tween the source and the chamber.
The sensor used for recording the dose as function of time for the whole irradiation was not in the same position as the chamber. Using a Fig. 2. Lateral cut of a DT layer.
Fig. 3. Locations of DT chambers in the CMS detector.
Fig. 4. Irradiationflux simulation inside the GIF++ bunker (Pfeiffer et al., 2017).
portable dosimeter, a correction factor was calculated to extrapolate the values from the sensor to the position of the chamber.
A set of measurements were made using a dosimeter placed on an automated platform to get a two-dimensional distribution of the dose rate in the chamber. The results are shown inFig. 5.
The areas with low dose rate correspond to two trapezoidal detec-tors installed by other users of the facility between the radiation source and the DT chamber, as can be seen inFig. 6.
3. Results
3.1. Conversion of dose to integrated luminosity
The actual variable of interest to compare with the expectations of the DT chambers at CMS is the integrated luminosity. To achieve that, a conversion factor of 0.42 mGy/fb-1is applied to the integrated dose to get the equivalent integrated luminosity. This conversion factor calcu-lated from simulation (Huhtinen, 1996) was found to be consistent with the one measured from the gain at GIF++ and CMS comparing the current/dose rate before aging and the slopes of high voltage current vs instantaneous luminosity (Table 3.1 in (The CMS Collaboration, 2017)). The fact that the two methods provide same results on the dose con-version factor minimizes its uncertainty. Nevertheless, a safety factor of 2 has been used in order to extrapolate the results to HL-LHC condi-tions.
3.2. Gain loss measurement
One parameter of great interest for the study is the gain of the de-tector, in the case of the DT chambers it can not be measured directly, because the front end electronics discrimante the signal and we lack information of the charge received, so an estimation was made using a previous study in one of the prototypes (Conti, 2002) that involved the use of linear charge amplifiers to read the charge collected from the cells after earch ionization. The fourth Quadruplet DT prototype (Q4) described in (Cerrada et al., 2002), consisting of four 16-wire layers with comparable functionality of a DT superlayer, was used for the normalization of the initial gain of the DT chambers under irradiation for this study.
The high voltage of the anode was set to 3550 to test the behaviour under lower voltage settings. InFig. 7the evolution of the gain eval-uated as a function of the integrated luminosity is shown. In order to extrapolate the values for the HL-LHC, the gain was fitted with the following function, where L is the Luminosity:
= + ⋅ Gain a b c Ld = ⋅ ± ⋅ = ± a 5.5 105 5 104 b 1.654 0.002 = ± = ± c 0.0369 0.0003 d 0.743 0.001
During thefirst 750 fb-1the gain was reduced to a third of its initial
value and a tendency towards a stable value can be appreciated. It can be observed that 30% of the initial gain is lost in thefirst 100 fb-1. This
suggests that the polymerization process responsible for the loss of gain happens faster when the wire has less coating and it saturates at higher values of integrated dose. This saturation in the aging suggests that when the full wire is covered with coating the deposition slows down. Moreover, the drop of gain itself slows down the generation of radicals to be deposited.
3.3. Efficiency study
During the 2017–2019 irradiation campaign the hit detection effi-ciency was measured in great detail using both muon beam data and cosmics data-taking.
The hit efficiency with cosmics was measured weekly during several months of chamber irradiation, broken in two periods, to accumulate roughly twice the equivalent HL-LHC dose. Only 2 out of the 12 layers (layers 1 and 4) of the chamber were switched on during the irradia-tion, and thus those were the layers in which the gain decrease was observed and the hit detection efficiency loss was measured. The chambers under test have been operated with a high voltage of 3550 V and Front End Threshold settings (FEth) of 20 or 30 mV, to check the effect of different settings on the hit efficiency.
During cosmic muon data-taking the source was off while all the chamber layers were switched on. The layers that were off during ir-radiation, therefore not showing signs of aging, acted as probes for the verification of the cells under study. The position of expected hits was determined using reconstructed tracks from at least 4 non-aged layers in SL3 and at least one layer in SL1. The intersection of these segments with the layer under study determined the cell where a hit was ex-pected. The cell was considered efficient if a hit was found within it. The hit efficiency of a layer was defined as the ratio between the number of detected and expected hits that were determined using the non-aged layers. Each of the data-taking runs consisted of over 50000 events.
InFig. 8the hit efficiency for cosmic muons as a function of the equivalent integrated luminosity expected for the most exposed chambers (YB±2MB1) at CMS is shown. Each of the points corresponds to one of the weekly data-taking runs with variable high voltage and no background radiation, the dotted blue lines indicate the different multiples of the integrated luminosity to be used as a safety factor. The loss of efficiency observed for two times the expected integrated Table 1
Conversion factors between equivalent dose (Sv) and absorbed dose (Gy) for the energy spectra and theflux distribution expected at GIF++. Conversion factors are weighted in relation with the percentage of totalflux at each energy bin.
Energy bins (keV) Percentage of total flux H*(10)/Ka (Sv/ Gy) Conversion factor 0–20 0 0 0 20–40 0.08 0.61 0.0005 40–60 0.49 1.47 0.0072 60–80 1.44 1.74 0.0251 80–100 2.03 1.72 0.0349 100–200 19.26 1.65 0.3178 200–300 10.16 1.4 0.1422 300–400 5.95 1.31 0.0779 400–500 5.60 1.26 0.0706 500–600 5.95 1.23 0.0732 600–662 49.03 1.21 0.5933 total 1.3427
Fig. 5. Two-dimensional dose rate distribution on the DT chamber installed at GIF++.
luminosity for HL-LHC is around 10%.
A common feature of gas drift chambers is the reduction of the ef-fective gain with the increase of the hit rate in the detector, this effect has higher impact on aged detectors due to the lower base gain. The presence of background radiation increases the occupancy in the de-tector and has a negative effect on the detection efficiency. To char-acterize the response of the layers under study with background ra-diation a muon beam was used. During this data-taking the trigger was provided by a set of scintillators placed before and after the chamber in the trajectory of the beam. The highest trigger rate observed was around 300 Hz, which was within the data acquisition parameters. The facility allowed to take several runs with different dose rate while triggering on the muons coming from the beam.
InFig. 9the hit efficiency for beam muons as a function of the in-stantaneous luminosity expected in the most exposed chambers (YB±2 MB1) is shown. The data was taken after irradiating the chamber with the integrated dose equivalent to a HL-LHC integrated luminosity of 3600 fb-1. The hit efficiency of the layers that have been irradiated degrades less than 20% when in presence of background radiation equivalent to HL-LHC. While the layers that have not been irradiated before barely present any variation in their hit efficiency under the same background conditions.
4. Conclusions
The irradiation campaigns have provided critical information about the behaviour of the chamber during a long irradiation period. The gain shows a 30% loss during thefirst stages of the irradiation, confirming that the speed of the degradation is proportional to the gain itself. This effect is being minimized for the chambers installed in CMS by lowering the operating high voltage of the detector anode to 3550 V, a value in which the accumulated charge is minimized (and thus the speed of gain loss) while the hit efficiency performance remains the same.
The results from the analysis show a potential decrease of the hit efficiency as the accumulated charge increases. The results have been extrapolated to the conditions expected in the most exposed chambers, therefore the rest of the detector will show less signs of aging due to radiation. Simulations considering the expected loss of efficiency show that overall the DT system is expected to operate satisfactorily during HL-LHC.
Nevertheless, to maximize detector efficiency, several mitigating actions are being taken. The gas system has been modified to operate in open loop configuration in order to stop the redistribution of compo-nents that could promote the formation of coating on the wires. Also, a Fig. 6. CMS DT spare chamber (rectangular detector with green outline)
pla-cement in the GIF++ bunker, shadowed by a CSC chamber (red outline). (For interpretation of the references to colour in thisfigure legend, the reader is referred to the Web version of this article.)
Fig. 7. Gain (ratio of the number of electrons for each incident electron) as a function of equivalent integrated luminosity for the most exposed chambers (YB ±2 MB1) (The CMS Collaboration, 2017) during the 2016 irradiation.
Fig. 8. Efficiency for cosmic muons as a function of equivalent integrated lu-minosity for the most exposed chambers (YB ±2 MB1).
Fig. 9. Efficiency for beam muons as a function of expected instantaneous lu-minosity for the most exposed chambers (YB ±2 MB1).
lead and borated polyethylene shielding has been installed to reduce the radiation that reaches the detector.
Finally, since the degradation is produced by hydrocarbon deposits on the anode wires, studying the possibility of removing the coating through the addition of a different gas mixture will be an interesting new effort in order to reduce, or even revert, the effects of the radiation aging on the wires.
CRediT authorship contribution statement
D.D. Redondo Ferrero: Resources, Software, Validation, Writing -original draft, Investigation, Data curation.G. Abbiendi: Resources. J. Alcaraz Maestre: Resources. A. Álvarez Fernández: Resources. B. Álvarez González: Resources, Software, Writing - review & editing. N. Amapane: Resources. I. Bachiller: Resources. J.M. Barcala: Resources. L. Barcellan: Resources. C. Battilana: Resources, Formal analysis.M. Bellato: Resources. G. Bencze: Resources. M. Benettoni: Resources. N. Beni: Resources. A. Benvenuti: Resources, Conceptualization. L.C. Blanco Ramos: Resources. A. Boletti: Resources. A. Bragagnolo: Resources. J.A. Brochero Cifuentes: Resources. V. Cafaro: Resources. A. Calderon: Resources. E. Calvo: Resources.A. Cappati: Resources. R. Carlin: Resources. C.A. Carrillo Montoya: Resources. S. Caturan: Resources. F.R. Cavallo: Resources, Formal analysis.J.M. Cela Ruiz: Resources. M. Cepeda: Resources. M. Cerrada: Resources. B. Chazin Quero: Resources. P. Checchia: Resources. L. Ciano: Resources. N. Colino: Resources. D. Corti: Resources. G. Cotto: Resources. J. Cuevas: Resources. M. Cuffiani: Resources.G.M. Dallavalle: Resources. D. Dattola: Resources. B. De La Cruz: Resources. P. De Remigis: Resources. J.F. de Trocóniz: Resources.C. Erice Cid: Resources. C.F. Bedoya: Resources, Writing -review & editing, Supervision, Project administration. F. Fabbri: Resources. A. Fanfani: Resources. D. Fasanella: Resources, Investigation. P. Fernandez Manteca: Resources. J. Fernández Menéndez: Resources. J.P. Fernández Ramos: Resources. S. Folgueras: Resources, Formal analysis. M.C. Fouz: Resources, Formal analysis.D. Francia Ferrero: Resources. J. García Romero: Resources. F. Gasparini: Resources, Conceptualization, Methodology. U. Gasparini: Resources. V. Giordano: Resources. F. Gomez Casademunt: Resources. F. Gonella: Resources, Software. I. González Caballero: Resources, Software, Writing - review & editing, Supervision. J.R. González Fernández: Resources, Software. O. González López: Resources, Software. S. Gosh: Resources. S. Goy López: Resources. A. Gozzelino: Resources. A. Griggio: Resources. G. Grosso: Resources. C. Guandalini: Resources. L. Guiducci: Resources, Formal analysis.M. Gulmini: Resources. T. Hebbeker: Resources. C. Heidemann: Resources, Software. J.M. Hernández: Resources. K. Hoepfner: Resources. F. Iemmi: Resources. R. Isocrate: Resources. M.I. Josa: Resources. B. Kiani: Resources, Investigation. S. Lacaprara: Resources. S. Lo Meo: Resources. S. Marcellini: Resources. M. Margoni: Resources. J. Marín: Resources. C. Mariotti: Resources. I. Martín Martín: Resources. C. Martínez Rivero: Resources. S. Maselli: Resources, Funding acquisition.G. Masetti: Resources, Investigation. A.T. Meneguzzo: Resources, Software, Conceptualization, Supervision. M. Merschmeyer: Resources. G. Mocellin: Resources. L. Modenese: Resources.A. Molinero: Resources. J. Molnar: Resources, Resources. F. Montecassiano: Resources. D. Moran: Resources. J.J. Navarrete: Resources.F. Navarria: Resources. Á. Navarro Tobar: Resources. J.C. Oller: Resources. M. Passaseo: Resources. J. Pazzini: Resources, Investigation, Supervision.M. Pegoraro: Resources. J. Puerta Pelayo:
Resources, Resources, Investigation, Validation. M. Pelliccioni: Resources, Formal analysis.B. Philipps: Resources. J. Piedra Gomez: Resources.G.L. Pinna Angioni: Resources. N. Pozzobon: Resources. M. Presilla: Resources. C. Prieels: Resources. F. Primavera: Resources. J.C. Puras Sánchez: Resources. I. Redondo: Resources, Writing - review & editing, Supervision, Project administration, Methodology.H. Reithler: Resources, Conceptualization. T. Rodrigo: Resources. V. Rodríguez Bouza: Resources, Software. J. Roemer: Resources.P. Ronchese: Resources. R. Rossin: Resources. F. Rotondo: Resources. T. Rovelli: Resources. S.Sánchez Cruz: Resources. S.Sánchez Navas: Resources, Investigation. J. Sastre: Resources. L. Scodellaro: Resources. F. Simonetto: Resources. M.S. Soares: Resources.A. Staiano: Resources. Z. Szillasi: Resources. D.F. Teyssier: Resources, Investigation. N. Toniolo: Resources. E. Torassa: Resources.D. Trocino: Resources. B. Ujvari: Resources. S. Ventura: Resources. R. Vilar Cortabitarte: Resources. J. Vizan Garcia: Resources.M. Zanetti: Resources. F.P. Zantis: Resources. G. Zilizi: Resources.P. Zotto: Resources.
Declaration of competing interest
The authors declare that they have no known competingfinancial interests or personal relationships that could have appeared to in flu-ence the work reported in this paper.
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