Study of electron/hadron discrimination with the NEUCAL detector

Study of electron/hadron discrimination with

the NEUCAL detector

M. Bongi (on behalf of R. D’Alessandro)

nTOF Collaboration Meeting – Athens17th December 2009

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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

1) University of Florence2) INFN Section of Florence3) IFAC – CNR, Florence4) University of Siena

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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

18 GeV/celectron

36 GeV/cproton

Two events detected by the PAMELA space experiment

SILICON TRACKER

MAGNET

TRIG. SCINTI.

E.M. CALO

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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

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The use of a neutron counter in PAMELA• Neutron productionNeutron production:

– Protons: hadronic interaction, nuclear excitation– Electrons: only through the Giant Resonance

• DifferentDifferent yield in neutron productionyield in neutron production is expected for e.m. or hadronic showers

• New idea in PAMELANew idea in PAMELA: use a neutron counter as the final stage of the apparatus (beyond calorimeter)

18 GeV/celectron

36 GeV/cproton

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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)

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)

SCINTPMT orSi-PMT

3He tube

n

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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

3He Tubes (1 cm diam.)

30 X0

NEUCAL

BGOtiles

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CALET FLUKA SIMULATION

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

1 TeV protons 400 GeV electrons

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Distribution of number of neutrons

400 GeV electrons400 GeV electrons1 TeV protons1 TeV protons

in case of hadronic showers the neutron yield is more than a factor 30 higher

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arrival time vs neutron energy

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

Outgoing neutron energy Log (E(GeV)/1GeV)

Arr

iva

l tim

e (L

og

(t(s

)/1

s)

1 G

eV

1 M

eV

100 ns

1 s

1 ke

V 10 ns

1 TeV protons

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11 cm of plastic scintillators

FLUKA based simulation,Degree Thesis byG. Sorichetti

1000 neutrons, E=100 keV

1000 neutrons, E=1 MeV

1000 neutrons, E=10 MeV

1000 neutrons, E=100 MeV

ENERGY RELEASE IN THE SCINTILLATORS

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

1H(n,)2H

E = 2.2 MeV

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Time distribution of signals in two scintillatorsfor 1000 neutrons, E=100 keV

10 keV energythreshold

100 ns

10 μs

radiative capture of neutrons

+ emission

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3He Tubes: time distribution of the signals

1000 neutrons, E=100 keV

1000 neutrons, E=1 MeV

1000 neutrons, E=10 MeV100 μs

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The prototype detector

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Production of scintillators

One side covered with aluminized tape

Scintillator material:Eljen Technology, type EJ-230 (PVT, equivalent to BC-408)

Light guides: simple plexiglas

Dimensions: 8.5 cm×25 cm×1 cm

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Production of prototype detecting modules

Optical grease: Saint Gobain BC-630Saint Gobain BC-630

PMT Hamamatsu Hamamatsu

R5946R5946

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Production of the first module

3He proportional counter tube: Canberra 12NH25/1Canberra 12NH25/1

1 cm diameter1 cm diameter

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Prototype assembly3x3 matrix of scintillator modules + 5 3He proportional counter tubes

1 cm diameter3He tubes

scintillatorlight guide

PMT

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Test beam at CERN SPS (August 2009)

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

NEUCALNEUCAL

CALORIMETER

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CALORIMETER

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Beam test details

• CERN SPSCERN SPS, line H4H4 (one week test)• Beam type - energy - # of events:

– PionsPions 350 GeV ( 230000 events)– electronselectrons 100 GeV ( 240000 events)– electronselectrons 150 GeV ( 50000 events)– muonsmuons 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…)

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• Next slides report a comparison of data with GEANT4 simul. for electron and pion events taken in the following configurations:

Detectors configuration

ELECTRON

beam

PION

beam

Total thickness upstream NEUCAL: 16 X0

Total thickness upstream NEUCAL: (16+13) X0

NEU

CAL

16 X0

WCALO

NEU

CAL

16 X0

WCALO

9 X9 X 00

PbPb2.

25 X

2.25

X 00Pb

WO

PbW

O 4`4`

30

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• 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

How to find neutron signals?

Trigger

PromptsignalScint.

A

Particlesignal

t=0 t=1ms

Promptsignal

t10ns

Scint.

B

Particlesignal

?time

time

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Digitalization of one muon event

ScintillatorsScintillators 3He tubes3He tubes

11 22

44 55

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DOWNSTREAMDOWNSTREAM

UPSTREAMUPSTREAM Trigger signalsTrigger signals

t = 0

t ~700ns

Bounces are due to additional filters on the digitizer inputs to solve a problem of firmware (loss of fast signals)

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Digitalization of one electron event

ScintillatorsScintillators 3He tubes3He tubes

11 22

44 55

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DOWNSTREAMDOWNSTREAM

UPSTREAMUPSTREAM Trigger signalsTrigger signals

All signals rise at t = 0 (prompt shower secondaries)

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Digitalization of pion events (1)

ScintillatorsScintillators 3He tubes3He tubes

11 22

44 55

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DOWNSTREAMDOWNSTREAM

UPSTREAMUPSTREAM Trigger signalsTrigger signals

t ~34 s

t ~100 s

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Digitalization of pion events (2)

ScintillatorsScintillators 3He tubes3He tubes

11 22

44 55

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DOWNSTREAMDOWNSTREAM

UPSTREAMUPSTREAM Trigger signalsTrigger signals

t ~28.5s t ~46.8s

t ~250s

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Digitalization of pion events (3)

ScintillatorsScintillators 3He tubes3He tubes

11 22

44 55

33

DOWNSTREAMDOWNSTREAM

UPSTREAMUPSTREAM Trigger signalsTrigger signals

t ~14.6s t ~170s

t ~12.6s

t ~250s

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Data/MC comparison: energy distribution in the scintillators

33000 ELECTRON events, E=100 GeV

75000 PION events,E=350 GeV

GEANT4

GEANT4

PRELIMINARY

PRELIMINARY

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Comparison data/MC: time distribution

GEANT4

GEANT4

PRELIMINARY

33000 ELECTRON events, E=100 GeV

75000 PION events,E=350 GeV

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Test at nTOF facility

Proton beam

Target

~ 200 meters

Neucal

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

2 weeks at end of OctoberMany thanks to the nTOF Collaboration!!!

Neutrons

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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

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Signals on scintillators

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Signals on 3He

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