Study of electron/hadron discrimination with the NEUCAL detector M. Bongi (on behalf of R. D’Alessandro) nTOF Collaboration Meeting – Athens 17th December 2009

The NEUCAL working group O. Adriani1,2, L. Bonechi1,2, M. Bongi2, S. Bottai2, M. Calamai4,2, G. Castellini3, R. D’Alessandro1,2, M. Grandi2, P. Papini2,S. Ricciarini2, G. Sguazzoni2, G. Sorichetti1, P. Sona1,2, P. Spillantini1,2, E. Vannuccini2, A. Viciani2 University of Florence INFN Section of Florence IFAC – CNR, Florence University of Siena

e/hadron discrimination in HEP Common requirement for HEP experiments particularly important for those devoted to Astroparticle Physics Electromagnetic calorimeters very good discrimination capability in a wide energy range Two events detected by the PAMELA space experiment 18 GeV/c electron 36 GeV/c proton SILICON TRACKER MAGNET TRIG. SCINTI. E.M. CALO 3

The situation at high energy protons with energy beyond few hundreds GeV interacting in the first layers of the calorimeter can be tagged as electrons due to similar energy release similar shower development It is not possible, especially for space experiments, to increase too much the calorimeter depth strong limitation in weight and power consumption 4

The use of a neutron counter in PAMELA Neutron production: Protons: hadronic interaction, nuclear excitation Electrons: only through the Giant Resonance Different yield in neutron production is expected for e.m. or hadronic showers New idea in PAMELA: use a neutron counter as the final stage of the apparatus (beyond calorimeter) 18 GeV/c electron 36 GeV/c proton 5

Detection of neutrons produced inside the calorimeter: the NEUCAL concept PAMELA: Moderation of neutrons by means of passive moderator (polyethylene layers) 3He proportional tubes to absorb thermal neutrons and detect signals due to the ionization of products inside gas: n + 3He  3H + p (Q = 0.764 MeV) New idea in NEUCAL: Study of the moderation phase using an active moderator Standard plastic scintillators are rich in hydrogen and thus suitable as moderators (Eljen EJ-230  [CH2CH(C6H4CH3)]n ) Detection of: signals due to neutron elastic/inelastic scattering signals due to absorption of neutrons by 3He (proportional tubes) n PMT or Si-PMT SCINT 3He tube

Simulation of the detector First results based on FLUKA (now implementing GEANT4 simulation, too) Detector geometry has been dimensioned for application together with a 30 X0 calorimeter (CALET experiment) NEUCAL is placed downstream a 30 X0 deep homogeneous BGO calorimeter 11 scintillator layers BGO tiles 30 X0 NEUCAL 3He Tubes (1 cm diam.)

CALET FLUKA SIMULATION 1 TeV protons 400 GeV electrons the average energy release of 1 TeV protons and 400 GeV electrons in the calorimeter is almost the same

Distribution of number of neutrons 400 GeV electrons 1 TeV protons in case of hadronic showers the neutron yield is more than a factor 30 higher

arrival time vs neutron energy 1 TeV protons 1 keV 1 MeV 1 GeV Arrival time (Log(t(s)/1s) 1 s 100 ns 10 ns Outgoing neutron energy Log (E(GeV)/1GeV) maximum in the MeV energy region (nuclear excitation) many neutrons undergo moderation before escaping, and their energy is degraded some neutrons are produced promptly in the hadronic interactions along the shower core the highest energy neutrons arrive close in time with respect to the charged component of the shower, while the low energy component arrives with a delay which ranges from 10 to 1000 ns

11 cm of plastic scintillators ENERGY RELEASE IN THE SCINTILLATORS FLUKA based simulation, Degree Thesis by G. Sorichetti 1H(n,)2H E = 2.2 MeV Neutrons up to few MeV kinetic energy are moderated and detected with high efficiency. At 10 MeV 70% of neutrons gives detectable signals. Only 10% are fully moderated to be detectable by the 3He Tubes 1000 neutrons, E=100 keV 1000 neutrons, E=1 MeV 1000 neutrons, E=10 MeV 1000 neutrons, E=100 MeV

Time distribution of signals in two scintillators for 1000 neutrons, E=100 keV radiative capture of neutrons +  emission 10 keV energy threshold 100 ns 10 μs

3He Tubes: time distribution of the signals 1000 neutrons, E=100 keV 1000 neutrons, E=1 MeV 1000 neutrons, E=10 MeV 100 μs

The prototype detector

Production of scintillators Scintillator material: Eljen Technology, type EJ-230 (PVT, equivalent to BC-408) Dimensions: 8.5 cm×25 cm×1 cm Light guides: simple plexiglas One side covered with aluminized tape

Production of prototype detecting modules PMT Hamamatsu R5946 Optical grease: Saint Gobain BC-630

Production of the first module 3He proportional counter tube: Canberra 12NH25/1 1 cm diameter

3x3 matrix of scintillator modules + 5 3He proportional counter tubes Prototype assembly 3x3 matrix of scintillator modules + 5 3He proportional counter tubes 1 cm diameter 3He tubes PMT light guide scintillator

Test beam at CERN SPS (August 2009)

Integration of the NEUCAL prototype with a 16 X0 tungsten calorimeter (25 July 2009)

CALORIMETER

Beam test details CERN SPS, line H4 (one week test) Beam type - energy - # of events: Pions 350 GeV ( 230000 events) electrons 100 GeV ( 240000 events) electrons 150 GeV ( 50000 events) muons 150 GeV (130000 events) Data collected in different configurations scan of detector (beam impact point) different working parameters PMTs and tubes voltages Digitizer boards parameters (thresholds, data compression…)

Detectors configuration Next slides report a comparison of data with GEANT4 simul. for electron and pion events taken in the following configurations: NEU CAL 16 X0 W CALO ELECTRON beam Total thickness upstream NEUCAL: 16 X0 NEU CAL 16 X0 W CALO PION beam 9 X0 Pb 2.25 X0 PbWO4` 30 Total thickness upstream NEUCAL: (16+13) X0

How to find neutron signals? Digitalization of scint. output for a long time interval (1ms) Look for signals which are not in time with other signals on other channels: Avoid the prompt signals due to charged particles coming directly from the shower Avoid single charged particles giving signals on more than one scintillator Trigger Prompt signal Particle signal ? Scint. A time Prompt signal Particle signal Scint. B time t=0 t10ns t=1ms

Digitalization of one muon event Trigger signals UPSTREAM t ~700ns 1 2 3 t = 0 4 5 Bounces are due to additional filters on the digitizer inputs to solve a problem of firmware (loss of fast signals) DOWNSTREAM Scintillators 3He tubes

Digitalization of one electron event Trigger signals UPSTREAM 1 2 3 All signals rise at t = 0 (prompt shower secondaries) 4 5 DOWNSTREAM Scintillators 3He tubes

Digitalization of pion events (1) Trigger signals UPSTREAM 1 2 3 t ~34 s 4 5 t ~100 s DOWNSTREAM Scintillators 3He tubes

Digitalization of pion events (2) Trigger signals UPSTREAM 1 2 3 t ~46.8s t ~28.5s 5 4 t ~250s DOWNSTREAM Scintillators 3He tubes

Digitalization of pion events (3) Trigger signals UPSTREAM t ~14.6s t ~170s 1 2 3 t ~250s 4 5 t ~12.6s DOWNSTREAM Scintillators 3He tubes

Data/MC comparison: energy distribution in the scintillators 33000 ELECTRON events, E=100 GeV GEANT4 PRELIMINARY 75000 PION events, E=350 GeV GEANT4 PRELIMINARY

Comparison data/MC: time distribution 33000 ELECTRON events, E=100 GeV GEANT4 PRELIMINARY 75000 PION events, E=350 GeV GEANT4

Test at nTOF facility 2 weeks at end of October Many thanks to the nTOF Collaboration!!! Proton beam Neutrons Neucal Target ~ 200 meters Very intense p beam (20 GeV, 1012 p/spill) Neutrons are produced in the target with different energies Neutrons travel along the 200 m line The energy of the neutron is inferred from the arrival time on the Neucal detector

Basic Idea Study the detector response to neutrons as a function of the neutron energy By knowing the neutron spectrum (both in shape and absolute normalization) we can measure the neutron detection efficiency

Signals on scintillators

Signals on 3He

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