Neutron position sensitive detector

ITEP,Moscow

Goryachev V.S., Chernishov O.A., Kirin D.Yu.,Mikhailov K.R.,Polozov P.A., Prokudin M.S., Romanov D.V., Sharkov G.B., Stavinskiy A.V., Stolin V.L.,Zhigareva N.M.

Nantes 2014 1

p Λ - 0 0 + n -

p X X X X X X XX X X

Λ X X X X X XX X X

- X X X X XX X X

X X X XX X X

0 X X X X+X X+X

0 X X X+X X+X

+ XX X X

n X X

- X

only tracking ---photon------neutron-- 10 18(13) 18(13) photon + neutron (4) photon or neutron (5)

(2) Baryon femtoscopy matrix

Physical motivation for neutron detector

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(1) Phase diagram for nuclear matter

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Neutron detectors(1)

LANDLarge area detector for high-energy neutronsΔTn/Tn = 5.3% for neutrons of Tn = 1 GeVangular resolution: 0.2° for a flight path of 15 mεn ~100% for neutrons of Tn= 1 GeVεn ~60% for neutrons of Tn= 0.2 GeV 400 photomultipliers/n(!)

!

ELENS

Neutron energy range of 100 keV to 10 MeVangular resolution of less than 1 degreeεn =25% for neutrons of Tn=500 keVεn =40% for neutrons of Tn=1 MeVFlight path 1-2 mTime resolution 840 psPosition resolution ~7,5 сmNeutron energy is determined using ToF tecniqueVery good light-collection efficiency is required for the detection of these small signals, so a proper wrapping material and the tight fitting of the foil onto the plastic were important criteria for ensuring a sufficiently high-quality light connection.

Wrapping procedure let reduce energy threshold Foil (VM2000) has a good reflection coefficient of R > 97% for ≥ 400 nm and R = (98.5 ± 0.3)% at 430 nm

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Neutron detectors(2)

εn =20-30% for neutrons of Tn=60-250MeV Time resolution ~ 250psecLiquid scintillator-> different signal shape for n/γ Large total volume V ~ 50 dm3 and small sensitive volume V ~ 4 dm3

[Tilquin I. et al., Nucl. Instrum. Methods A365, 1995,p.446 ] 5

Neutron detectors(3)

Cross-TalksIf the same neutron is registered in two or more detectors –the cross-talk effect occurs.Cross-talk: simulates registered of two or more neutrons in neighbor module leadingto a strong spurious correlation. In case of one-particle distributionthe cross-talk effects are usually small, but in femtoscopy measurementsthis effect is quite important and dangerous.

Cross-Talks

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Required features for new created detector

• Neutron energy range of 3 MeV to 250 MeV

• Time resolution ~ 300 psec

(For L~2m->accuracy for neutron momentum 15-25 MeV/c)

• Position resolution one order better than module size (~ 1 cm)

• Modular structure of detector for corelation measurements

• Module shape acceptable for germetic installation -> to create germetic large acceptance detector

• Compact module(to be able to use it as a part of universal detectors within magnets)

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Neutron detector (first prototype)-ITEP

Plastic Scintillator 96 * 96 * 128 mm3

Fiber: KYRARAY,Y-11,d =1mm,

wavelength shift

4 SiPM & Amplifier - CPTA(Golovin)

Efficiency (estimate) 15%

Beam tests of first prototypeDC1

Beam ofProtons

p=3GeV/c

DC2

Ndet

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Amplitude spectrum

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Neutron detector (first prototype)-ITEP

d (cm)R

=A

4/A

2space resolution for the first prototype ~ 2.5 cm

180cm

20cm

Distance from the target 240cm;Detector thickness 20cm

Fiber + SiPM

Neutron detector supermodule (78 detectors)

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Neutron detector (second prototype)-ITEP

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Front Side Back

Neutron detector (second prototype)-ITEP

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Neutron Beam test of prototype@Nuclotron

Td= 4 GeV/nucleon

( )d C pn X

Calibration of neutron detector

Purpose of simulation – estimation difference between neutron coordinate and recoil proton coordinate.

In framework Geant4 n+detector interaction for different neutron energy was simulated. H/C ~ BC400 (1.103). 105 neutrons for each energy. Neutrons shoot to detector centre. Event selection criteria: one proton realize after first interaction.

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Principal restriction for neutron coordinate resolution

Distribution of secondary protons

150MeV 300MeV

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Simulation neutron detector (second prototype)-ITEP

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Dependence of maximum deviation protons from deposit energies(neutron energy 150 MeV)

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Back wall events and collision with nucleus events

Dependence of maximum deviation protons from deposit energies

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Main events

Dependence of maximum deviation protons from deposit energies

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Neutron energy, MeV

50 100 150 200 300

% selected events

18,8 18,0 17,4 17,6 18,2

mean deviation end of protons track, mm

1,2 4,7 9,5 14,9 24,3

maximum deviation protons, mm

5,7 25,3 50,2 80,2 90,0

Results of the simulations

Next step

Conclusions 1. Principal restriction for spatial resolution for detector

< 1 cm at neutron energy < 150 MeV. 2. Expected spatial resolution for created module of

detector less than 1,5cm.

LANS(LINP-1980) large acceptance neutron spectrometerV.N.Baturin et al., LINP-594,1980 V(LxLyLz)=200x200x1000mm3

στ=2nsecεn =35% for neutrons of Tn=300MeV2 neutrons in 1 module register like 1 neutronPosition resolution – module size

Neutron detectors(1)

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1.scintillator 2.lightguide3.photomultipliers 4.photodiodes5. voltage divider6.magnetic screen 7. spring