Charged Particle and Neutron Detection Facilities for Experiments with SCC

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Charged Particle and Neutron Detection Facilities
for Experiments with SCC

• Kaushik Banerjee
• Variable Energy Cyclotron Centre

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Content

• Physics Motivation
• Charged Particle Detector Array
• Description and Recent Development
• Neutron Detector Array
• Description and Recent Development
• Summary

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Physics Motivation
?
Temp?
Detectors
Size?
Lifetime?
Shape?
Formation and decay of hot nuclei Multi particle
correlation studies Understanding of
multifragmentation Liquid-to-Gas phase
transition
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E lt 2 MeV/nucl Compound nucleus decay channel
(evaporation and fission)
Intermediate energy collision
E gt 2 MeV/nucl Simultaneous break-up in many
fragments
To detect all the particles, require higher solid
angle coverage gt
Array of detectors
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Two Particle correlation function
N12 coincidence yield N1N2 uncorrelated yield
product of singles P1,P2 Momentum of two
particles q Relative momentum of two particle
Detector should have good angular and energy
resolution.
Two particle correlation function at small
relative momenta contain information about the
space time characteristics of the emitting system.
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Nuclear Temperature
Slope Parameter P, d, t, ?
Slope of the K.E. spectra of LCP Slope
Thermometer
Isotopic Composition (3He/4He)/(6Li/7Li)
Relative isotopic yield of products Double
Isotope Thermometer
Detectors should have good isotopic resolution.
Internal Excitation 5Li16.66/5Ligs
Relative population of states Excited State
Thermometer
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• Ideally a 4? detector should provide following
  information on event by event basis
• Number of particle in the event
• Identity (Z,A)
• Energy
• Emission angles (?, ?)

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Schematic view of CPDA
Forward part
Backward part
Extreme forward part
Beam direction

• good geometrical efficiency
• very low energy threshold
• 3. fragments identification (Z,M)
• 4. high granularity

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Forward part of the Array
No. of Telescopes 24 Angular coverage 70
lt ? lt 450
Isotopic (Z A) up to Z 10. Particle
Identification ?E -E
Typical Eth Proton 2 MeV
Alpha 2 MeV/A Oxygen 4 MeV/A
Distance from target 20 cm (radially,
av.) Angular Res. lt 10
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Backward part of the array
Detector CsI(Tl) No. of Dets.
300 Angular coverage 450 lt q lt 1700
Distance from target 15 cm Particle
Identification PSD
Extreme Forward part of the array
Detector Slow (100 mm)/fast (200mm)
Plastic No. of Dets. 32 (20mm x 20
mm) Angular coverage 30 lt q lt
70
Distance from target 40 cm Particle
Identification PSD
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Proto type testing
Experimental Set Up
Telescope
Pre amplifiers
VME ADC
Amplifiers
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145MeV 20Ne on 12C
Slope parameter exp(-E/T)
T2.9 0.5 MeV
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d - ? correlation
? -? correlation
C(q)
C(q)
Excited State Thermometer
T 2.6 0.4 MeV
T 2.2 0.5 MeV

T(double isotope method) 2.6 0.2
Communicated to PRC
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Present Status of CPDA

• Simulation with HIPSE generator
• Prototype testing
• VME-DAQ development
• Analysis packages on ROOTS
• Detector procurement (first batch (10
  telescopes) )

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Neutron Detectors

• TOF type neutron detector
• Neutron multiplicity detector

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Contour diagram of neutron multiplicity Vs light
charged particle multiplicity for 209Bi 136Xe
Reaction at 62 MeV/nucleon. Neutron multiplicity
is higher than light charged particle
multiplicity.

• Neutron Multiplicity ? Excitation Energy ?
  Impact Parameter
• Neutron Multiplicity ? Distinguish Coulomb
  fission from Nuclear fission
• Pre scission neutron multiplicity ? Time scale
  of Fusion Fission reaction.

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TOF type array for neutron energy and
multiplicity measurements

• Energy Measurement Time of Flight
  Method
• Neutron gamma discrimination
• Zero Cross Over Method
• Charge integration Method

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Nitrogen flushing
Liquid chamber
Photo-multiplier tube
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Technical Details Liquid Scintillator
BC501A Photo-multiplier tube 9823B (5, 14
stage) Liquid sealing 6mm Pyrex
glass Reflection coating Teflon
Smaller the size of detector, better will be M
value.
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Efficiency Measurement Associated particle
technique START from MWPC and STOP from Neutron
detector
Measured value
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Efficiency of TOF type neutron detector
CECIL calculation
Detector should have reasonable efficiency and
reasonable figure of merit ? Dimension has to be
fixed accordingly
Higher the size of detector better the efficiency.
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ToF Array Array of 50 detectors Combination of 5?
? 5? and 7? ? 5?
To cover a large solid angle and to achieve a
good time resolution we need large number of
detectors.
HOW MANY ?
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One Example DEMON
No. of Detectors 96 Solid angle coverage 5
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Neutron
Multiplicity Detector Motivation Neutron
Multiplicity Measurement with very high efficiency
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in Gd loaded liquid scintillator
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Efficiency of the detector
1mt
DENIS Simulation
4? solid angle coverage ? very high
efficiency Slow Detector ? (50-100)?s
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Capture Site Distribution
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Prototype Development Detector 13cm
dia, 60cm long SS cylinder Liquid used
BC521(0.5 Gd), BC525(0.2) PMT used 5"
PMT (9823B of Electron Tube)
For Liquid Testing ? Concentration of Gd ?
Capture Time Distribution
In small size detector ?- rays are not fully
absorbed in the detector medium We have used an
indirect method to obtain capture signal using
BaF2 detectors.
No Capture Signal
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Test Setup
14 BaF2 detectors of size (3.5cm x 3.5cm and
35cm long) have been used. 4 on the top used in
coincidence with liquid as start 5 on both
sides of liquid in coincidence with liquid as
stop.
? Rays produced after the neutron capture in Gd
were detected by the BaF2 detectors surrounding
the liquid detector. Pb sheet above the liquid
was used to stop the direct ?- rays from the
source.
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Results
Experimental result
Simulation result
Experimental results matches well with that of
simulated results obtained using DENIS code. More
the Gd percentage less will be the time require
to complete the capture process.
NIM A 580 (2007) 1383
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500 Litre Capacity
Technical Details Liquid Scintillator 0.5 Gd
loaded liquid Scintillator BC521 5
photo-multiplier tubes five per section
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Current Status of Neutron Multiplicity Detector
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Summary

• Detail description of charged particle and
  neutron detector array have been presented.
• The charged particle array is highly granular,
  with good angular and energy resolution, will be
  best suited for particle particle co-relation
  type of experiments.
• With neutron TOF array one can measure neutron
  energy and multiplicity but difficult to achieve
  high efficiency.
• With 4p neutron multiplicity detector one can
  obtain neutron multiplicity with very high
  efficiency but energy measurement is difficult.
• All the above mentioned facilities will be used
  for Nuclear Physics Research using
  Super-Conducting Cyclotron Beam. 

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OUR TEAM
S. Bhattacharya, C. Bhattacharya, S. Kundu, T.K.
Rana, T. K. Ghosh G. Mukherjee, J. K. Meena, A.
Dey, D. Gupta, P. Mali, D. Pandit, S.
Mukhopadhyay, S. R. Banerjee, A. Roy, P. Dhara
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Thank You
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General Purpose scattering chamber
Size 2.2mt long, 1mt diameter, 3sector all
movable Vacuum system 2turbo, 2cryo, 4 scroll
pump for backing, automatic PLC controlled Vacuum
10-7 mb typical.