Transcript Study of e/p discrimination with the NEUCAL detector

11th ICATPP - Conference on Astroparticle, Particle, Space
Physics, Detectors and Medical Physics Applications
5-9 October 2009, Villa Olmo (Co), Italy
Preliminary study of electron/hadron
discrimination with the NEUCAL
detector
Lorenzo Bonechi
University and INFN – Florence (Italy)
The NEUCAL working group
O. Adriani1,2, L. Bonechi1,2, M. Bongi2, S. Bottai2,
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 Florence
2) INFN Section of Florence
3) IFAC – CNR, Florence
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Outline of this presentation
• Basic ideas
– e/hadrons discrimination with e.m. calorimeters
– Use of neutron detectors (PAMELA experiment)
– The new NEUCAL concept
• Simulations
• The prototype detector
– Description of apparatus and assembling
• Test beam at CERN SPS (August 2009)
– Event show and first preliminary comparison with the GEANT4
simulation
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PART 1
Basic ideas
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e/hadrons 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
SILICON
TRACKER
18 GeV/c
electron
36 GeV/c
proton
MAGNET
TRIG.
SCINTI.
E.M.
CALO
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The situation at higher energy
• Interacting protons with energy beyond few
hundreds GeV can be tagged as electrons due to
– similar energy release in calorimeter than electrons
– similar shower development than electrons
• It is not possible, especially for space experiments,
to increase too much the calorimeter depth
– strong limitation in weight and power consumption
• Complementary detectors, like trackers, cannot help
easily at these energies
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The use of a neutron counter in PAMELA
• Neutron production:
– Protons: nuclear excitation, hadronic interaction and Giant Resonance
– Electrons: only through the Giant Resonance
• Different yield in neutron production are 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
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36 GeV/c
proton
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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 then suitable as
moderators (Eljen EJ-230  [CH2CH(C6H4CH3)]n )
• Detection of:
– signals due to neutron elastic/inelastic scattering
– signals due to absorption of neutrons
PMT or
3He (proportional tubes)
Si-PMT
SCINT
3He
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n
by
tube
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PART 2
Simulation
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Few details and results
• First results based on FLUKA, now implementing also
GEANT4 simulation
• 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
12
scintillator
layers
BGO
tiles
30 X0
NEUCAL
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3He
Tubes
(1 cm diam.)
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Distribution of number of neutrons
Note: energy release inside the BGO calorimeter is almost the same for
1TeV protons and 400 GeV electrons.
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1 TeV protons
400 GeV electrons
FLUKA
FLUKA
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Scatter plot: arrival time vs neutron energy
1 GeV
1 s
1 MeV
1 keV
Arrival time (seconds)
Almost all neutrons exit from the calorimeter within a few microseconds,
but thermalization inside neucal can take hundreds microseconds
100 ns
10 ns
Outgoing neutron energy Log (E(GeV)/1GeV)
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Expected performance (comparison FLUKA/GEANT4)
FLUKA simulated energy release inside one scintillator layer
See also: S.Bottai et al., at Frontier Detector for Frontier Physics, La Biodola (Elba), 24-30 May 2009
ENTRIES
Neutrons up to few
MeV kinetic energy
are
moderated
and detected with
high efficiency.
1 MeV neutrons
ENTRIES
At 10 MeV 70% of
neutrons
gives
detectable signals.
Only 10% are fully
moderated to be
detectable by the
3He Tubes
10 MeV neutrons
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PART 3
The prototype detector
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Production of scintillators
Scintillator material:
Eljen Technology, type EJ-230 (PVT, equivalent to BC-408)
Light guides: simple plexiglas
One side covered with aluminized tape
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Production of prototype detecting modules
PMT
Hamamatsu
R5946
Optical grease: Saint Gobain BC-630
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Production of the first module
3He
proportional counter tube: Canberra 12NH25/1
1 cm diameter
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Prototype assembly
3x3 matrix of scintillator modules with 5 3He proportional counter tubes
integrated
1 cm diameter
3He tubes
PMT
light guide
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scintillator
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Digitalization electronics
CAEN V1731 board
 VME standard
 8 ch, 500MS/s
 8 bit ADC
 2MB/ch memory (few ms digitization)
 16 ns jitter
 On-board data compression (Zero Suppression Encoding)
CAEN V1720 board
 VME standard
 8 ch, 250MS/s
 12 bit ADC
 2MB/ch memory (few ms digitization)
 32 ns jitter
 On-board data compression (Zero Suppression Encoding)
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PART 4
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)
CALORIMETER
NEUCAL
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CALORIMETER
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Beam test details
• CERN SPS, line H4 (one week test)
• Beam type – energy - # of events:
–
–
–
–
Pions
electrons
electrons
muons
350 GeV
100 GeV
150 GeV
150 GeV
( 230000 events)
( 240000 events)
( 50000 events)
(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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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
30
beam
Total thickness upstream NEUCAL: (16+13) X0
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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 then one scintillator (non interacting
hadrons entering the detector
Trigger
Prompt
signal
Scint.
Particle
signal
?
A
time
Particle
signal
Prompt
signal
Scint.
time
B
t=0
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t10us
t=1ms
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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
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Scintillators
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3He tubes
26
Digitalization of one electron event
Trigger signals
UPSTREAM
1
2
3
All signals rise at t = 0
(prompt shower secondaries)
4
DOWNSTREAM
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Scintillators
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3He tubes
27
Digitalization of pion events (1)
Trigger signals
UPSTREAM
1
2
3
t ~34 s
4
5
t ~100 s
DOWNSTREAM
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Scintillators
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3He tubes
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Digitalization of pion events (2)
Trigger signals
UPSTREAM
1
2
t ~46.8s
t ~28.5s
4
3
5
t ~250s
DOWNSTREAM
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Scintillators
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3He tubes
29
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
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Scintillators
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3He tubes
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First preliminary comparison data/MC
33000 events
100 GeV ELECTRONS
- “single” signals
- one single central PMT
GEANT4
ENERGY
Instrumental
effect
?
data
Spurious
particles
ARRIVAL TIME
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First preliminary comparison data/MC
75000 events
350 GeV PIONS
- “single” signals
- one single central PMT
GEANT4
ENERGY
data
?
Spurious
particles
ARRIVAL TIME
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Comparison data/MC: signal energy distribution
33000 ELECTRON events
GEANT4
75000 PION events
GEANT4
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Comparison data/MC: time distribution
33000 ELECTRON events
GEANT4
75000 PION events
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GEANT4
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Conclusions
• A new neutron detector, NEUCAL, is under study for particle
identification purposes
• Its aim is to help e.m. calorimeters in e/hadron separation at H.E.
• New idea: use an active moderator (plastic scintillator) to moderate
the neutrons and detect their signals simoultaneously
• A prototype has been developed e tested with charged particles
during a beam test at CERN SPS (August 2009)
• First very preliminary comparison between data and GEANT4
simulation shows substantial agreement, even if some effects is not
yet understood (instrumental effect?)
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Backup slides
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Expected performance
Simulated energy release inside NEUCAL (12 scintillator layers detector)
S.Bottai et al., at Frontier Detector for Frontier Physics,
La Biodola (Elba), 24-30 May 2009
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
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Filter
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