???????????? ???????? Fast Neutron Detection in Unstable Nuclei Reaction Experiment

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????????????????????Fast Neutron Detection
inUnstable Nuclei Reaction Experiment
Ryuki Tanaka Tokyo Institute of Technology
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Background
17Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne 34Ne
17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F
13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O 26O 28O
12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N
9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 22C
8B 10B 11B 12B 13B 14B 15B 17B 19B
7Be 9Be 10Be 11Be 12Be 14Be
6Li 7Li 8Li 9Li 11Li
3He 4He 6He 8He
1H 2H 3H
Proton-rich
Oxygen Anomaly
proton number
11Li
Neutron Halo (11Li, 14Be, 22C, etc.)
Stable
Neutron-rich
neutron number
Breakup reactions of extreme neutron-rich nuclei
at Intermediate energies ? Invariant Mass
Spectroscopy involving Detection of Fast Neutrons
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Invariant Mass Spectroscopy
"Mass" measurement of 26O (Unbound) for study of
the Oxygen Anomaly
E
26O
Erel(relative energy)
24Onn
Neutron Measurement
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1. Development of the large acceptance neutron
detector "NEBULA"
3. Development of next generation neutron
detector "HIME"
2. Evaluation of newly developed simulator
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5
Momentum of Neutron
Photomultiplier Tube
tl
Plastic scintillator
target
(r1, t1)
10 m
(r0, t0)
beam
nC, nH ? charged particles (p, a, etc.)
Time of Flight (TOF), Position ? E, p
t1 ? tl tr x1 ? tl - tr y1,z1geo.
tr
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Development of NEBULA
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Neutron Detector "NEBULA"
NEutron-detection system for Breakup of
Unstable-nuclei with Large Acceptance
? Key Component of spectrometer SAMURAI_at_RIKEN
x 120 modules
SAMURAI Commissioning Experiment in March 2012
? evaluation of NEBULA
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SAMURAI Commissioning Experiment 1
Quasi-monoenergetic Single Neutron Cross
Section is well known ? TOF Resolution, Efficiency
7Li(p,n)7Be(g.s.0.43 MeV)
SAMURAI Magnet Bmax3T, superconducting
natLi
200 MeV (250 MeV)
NEBULA
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Time of Flight Resolution
Threshold level 6 MeVee ?lab lt 40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
sTOF335(5) ps
Counts
total
7Be other excited states scattered
neutrons
6Li(p,n)6Be (4.4)
All effects not related to NEBULA taken into
account
TOF(measured) - TOF(calculate) (ns)
Intrinsic Resolution sTOF263(6) ps
cf.) 300 ps (design value)
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Efficiency
Threshold level 6 MeVee ?lab lt 40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
32.3(4)
Counts
total
6Li(p,n)6Be (4.4)
7Be other excited states scattered
neutrons
6 correction for neutron flux loss, etc.
Intrinsic Efficiency 34.70.4(stat.)1.0(syst.)
En (MeV)
cf.) 37 Geant4 with INCLXX 40 DEMONS
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SAMURAI Commissioning Experiment 2
C(14Be,12Benn)
2-neutron event ? cross-talk rejection
SAMURAI Magnet Bmax3T, superconducting
C
220 MeV/A
NEBULA
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2-neutron event and Cross-talk event
wall2
ß12
wall1
NEUT
VETO
Cross-talk event
ß02
cross-talk event satisfy ß12 lt ß01
ß01
? ß12 gt ß01 can only be 2-neutron event
2-neutron event selection ß01/ß12 lt 1
2-neutron
1-neutron
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1-Neutron Event Pb(15C,14Cn)
2-Neutron Event C(14Be,12Benn)
fake 2-neutron
Crosstalk
2-neutron
Crosstalk ( 2-neutron)
Counts
Counts
43 (2 is fake)
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? 1/20 contribution
ß01/ß12
ß01/ß12
(0 MeV lt Erel lt1 MeV)
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C(14Be,12Benn)
87(5) keV (1s)
preliminary
Counts
ß01/ß12
projection to x axis
Erel (MeV)
T. Sugimoto et al., Phys. Lett. B 654, 160 (2007)
En68 MeV/A
100 keV (1s)
14Be (2)
ß01/ß12 lt 1
is valid cross-talk rejection procedure !!
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Development of Simulator
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Development of Simulator
? Simulation is Needed for Analysis and
Development of Neutron Detector response
function acceptance efficiency
etc.
? Simulator for neutron detector array is Not
established for En 250 MeV neutron ?
developed new simulator with Geant4
compare with SAMURAI commissioning data
7Li(p,n)7Be(g.s.0.43 MeV)
(En200 MeV)
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Evaluation of Simulator
compare three physics models for nplastic
scintilator BERT (intranuclear cascade model)
INCLXX (intranuclear cascade model) MENATE_R
(treat each reaction channel)
Z. Kohley et al., Nucl. Instr. and Meths. A 682,
59 (2012).
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Evaluation of Simulator
compare three physics models for nplastic
scintilator BERT (intranuclear cascade model)
INCLXX (intranuclear cascade model) MENATE_R
(treat each reaction channel)
Z. Kohley et al., Nucl. Instr. and Meths. A 682,
59 (2012).
w/o 12C(n,p)12B
MENATER
MENATER
MENATER
Efficiency ()
Efficiency(sim.) / Efficiency(exp.)
Experiment
BERT
INCLXX
BERT
INCLXX
Light Output Threshold (MeVee)
Light Output Threshold (MeVee)
INCLXX gives best agreement
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Development of HIME
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Neutron Detector "HIME"
HIgh resolution detector array for Multi-neutron
Events
NEBULA sy5cm, sxsz3.5cm, st0.2ns DErel84
keV (1s) _at_1MeV
10cm
40cm
1.7m
40cm
HIME sxsy1.2cm, sz0.6cm, st0.1ns DErel40
keV (1s) _at_1MeV
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Cross-talk Rejection Method
NEBULA ß01/ß12 lt 1 ? lose about half of
2-neutron event
NEBULA e4n0.01
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Cross-talk Rejection Method
HIME tracking of recoiled proton
calculate the scattered neutron kinematics
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Cross-talk Rejection Method
Geant4 Simulation
z
Cross-talk event
2-neutron
1-neutron
signal position of one event
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Cross-talk Rejection Method
Geant4 Simulation
z
assume np elastic
signal position of one event
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Cross-talk Rejection Method
Geant4 Simulation
z
Cross-talk event
1-neutron
signal position of one event
HIME e4n1 (goal)
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conclusions
? large acceptance neutron detector NEBULA ?
TOF Resolution 263(6) ps (En200 MeV) ?
achieved the design value 300 ps Efficiency
34.70.4(stat.)1.0(syst.) (En200 MeV) ?
good agreement with newly developed simulator
37 Cross-talk rejection ß01/ß12 lt 1
1/20 contribution of cross-talk for 14Be
measurement
? Simulation ? New simulation code reproduce
SAMURAI experiment
? next generation neutron detector HIME ?
Relative Energy Resolution 40 keV at Erel1
MeV 2-neutron event selection method is
established
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backup
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Analysis of NEBULA
7Li(p,n)7Be(g.s.0.43 MeV)
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Time of Flight Resolution
En 200 MeV Threshold level 6 MeVee ?lab lt
40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
sTOF335(5) ps
Counts
total
7Be other excited states scattered
neutrons
6Li(p,n)6Be (4.4)
subtract fluctuation of beam velocity time of
neutron origin
TOF(measured) - TOF(calculate) (ns)
sTOF263(6) ps (En 200 MeV) sTOF257(8) ps (En
250 MeV)
NEBULA's contribution to TOF resolution
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Energy Resolution
En 200 MeV Threshold level 6 MeVee ?lab lt
40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
sE2.59(4) MeV
Counts / 0.1 ns
total
7Be other excited states scattered
neutrons
6Li(p,n)6Be (4.4)
subtract fluctuation of neutron velocity time
of neutron origin
Energy (MeV)
sE2.03(5) MeV (En 200 MeV) sE3.00(8) MeV (En
250 MeV)
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Efficiency
En 200 MeV Threshold level 6 MeVee ?lab lt
40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
32.3(4)
Counts
total
7Be other excited states scattered
neutrons
6Li(p,n)6Be (4.4)
according to simulation 6-7 correction need
En (MeV)
34.7(4) (En 200 MeV) 34.3(7) (En 250 MeV)
NEBULA's intrinsic efficiency
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26.0(7) mbar/sr _at_ 200 MeV ? 2.7
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Efficiency
En 200 MeV Threshold level 6 MeVee ?lab lt
40 mrad
7Li(p,n)7Be(g.s.0.43MeV)
32.3(4)
Counts
total
7Be other excited states scattered
neutrons
6Li(p,n)6Be (4.4)
count right part of energy dist. ? 20508
counts full fit procedure ? 20191 counts
En (MeV)
1.5 difference (FWHM)
NEBULA's intrinsic efficiency
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TOF resolution correction
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Efficiency correction
6-7 correction neutron flux loss by
materials - Li target - neutron window -
air between neutron window and NEBULA
scattered neutrons
3
3
6.9 (En 200 MeV) 6.2 (En 250 MeV)
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One-Neutron Event Pb(15C,14Cn)
Two-Neutron Event C(14Be,12Benn)
ß01/ß12
ß01/ß12
Erel (MeV)
Erel (MeV)
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One-Neutron Event Pb(15C,14Cn)
Two-Neutron Event C(14Be,12Benn)
Counts
Counts
ß01/ß12
ß01/ß12
(0 MeV lt Erel lt 100 MeV)
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MENATE_R (treat each reaction channel)
MENATE_R is ported code of neutron detector
simulator MENATE written in FORTRAN
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BERT, INCLXX (Geant4 built in class) BERT
Bertini Intranuclear Cascade Model (Bertini H.
W. Bertini) - M. P. Guthrie, R. G.
Alsmiller and H. W. Bertini, Nucl. Instr. Meth,
66, 1968, 29. - widely used INCLXX
INCL ? c version of INCL INCL Liege
Intranuclear Cascade Model (Liege the Belgian
city) - developed and validated against
recent data - typical users are from the
nuclear physics community studying spallation
processes
(Journal of Physics Conference Series 119
(2008) 032024)
Nuclear Instruments and Methods in Physics
Research A 491 (2002) 492506
model limit 200 MeV lt Ein lt 10 GeV
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DEMONS
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A. Del Guerra, Nucl. Instr. and Meths. 135, 337
(1976).
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A. Del Guerra, Nucl. Instr. and Meths. 135, 337
(1976).
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Efficiency(sim.) / Efficiency(exp.)
6 MeVee
Threshold (MeVee)
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Detection Method
NEBULA
HIME
classical detection technic
tracking detection
? reconstruct momentum by a signal from one
module
? reconstruct momentum by a track of
recoiled proton
? efficient cross-talk rejection for
multi-neutron detection
NEBULA e4n0.01
HIME e4n1 (goal)
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Cross-talk Rejection
Geant4 Simulation
2n event
Cross-talk event
p
p
p
n
p
n
n
n
further simulation is ongoing
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Time Resolution
ordinary event
tracked event (ngt3)
Energy dependence of timing resolution
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Efficiency and Erel Resolution
ordinary event
Geant4 Simulation
tracked event (ngt3)
42 keV
40 keV
Relative Energy Resolution (keV)
Efficiency ()
improve only 5
En (MeV)
Relative Energy (MeV)
optimization of timing calculation HIME is to
small time resolution is already high (100 ps)
(En 250 MeV, 10 m, A100)
High Resolution is already obtained
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Simulated Example
12B ?10Li(1,2)?9Lin
(RIBF exp. Planned _at_250MeV/nucleon)
Two p-wave states ( p (p3/2)x n(p1/2) ? 1,
2) should be there! But not yet clarified .
(Myo et al. TOSM)
HIME
NEBULA
10Li (1 and 2)
10Li (1 and 2)
2
1
Erel(9Lin)
Erel(9Lin)
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Experimental Setup-I
1. Event-by-event setup Low event rate(380
events/h, Beam 5x105 cps) Use of T0 Detector
Accurate beam rate Better T Resolution
( lt0.1ns)
Measure Timing Resolution, and Absolute
Detection Efficiency _at_Ein250MeV
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Experimental Setup-II
2. High-Intensity Setup High event rate (T0
detector Removed) Lower accuracy for beam
rate Long TOF (Better E spectrum)
Measure Relative Efficiency _at_Ein100/ 250 MeV
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test with cosmic ray is ongoing (will be
presented by T. Nakashima)
test exp. will be performed at RCNP