New High Resolution Neutron Detector for the Studies of Exotic Nuclei
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New High Resolution Neutron Detector for the Studies
of Exotic Nuclei
DOE DE-NA0003899
Beta-delayed Neutron Spectroscopy of Exotic Nuclei 06/2019-06/2022
Neutron dEtector PI: Robert Grzywacz
with xn Tracking(
University of Tennessee
Department of Physics and Astronomy
Robert Grzywacz
Lawrence Heilbronn
Supported:
Miguel Madurga
University of Tennessee Dr. Cory Thornsberry (until October 2019)
Mustafa Rajabali Dr. Kevin Siegl (from January 2020)
Tennessee Technological University Graduate students:
Joe Heideman (NEXT) current
DOE DE-NA0002934 Shree Neupane (NEXT) (until Sep 2019)
06.2016-06.2019 Andrew Keeler (VANDLE) current
presentations given at conferences and meetings
R. G. Erice/Mazurian Lakes/LECM
Neupane (3)/Heideman (3) 1
SSAP 2020 R. Grzywacz
New accomplishments: 2019-2020
●
Proof of principle measurements at U. Kentucky with tritium target
●
Published NIM manuscript: proof of concept and the prototype performance
●
Six prototype modules
●
Optimization of the detector manufacturing
●
Measurements at Ohio University with (d,n)
(efficiency, thin target)
●
More complete Monte Carlo (Geant4) model including
realistic timing algorithm, focus on array, UTK large scale
computing infrastructure
●
Measurement at ANL CARIBU (this week) with refractory βn-precursors
●
J. Heideman dissertation nearly complete
●
A larger array of 40-50 detectors funded through NSF MRI
2
SSAP 2020 R. Grzywacz
Beta-delayed neutron emission
Composite decay mode of neutron-rich nuclei
Far from stability decay energy Qβ increases and neutron separation energy Sn decreases.
●
Delayed neutron emission becomes dominant decay mode
●
Neutron energy carries the information about excited states in the emitter.
Experimental challenge: reconstruct complete decay pattern with best possible resolution.
βn β2n β3+n
Exp. (NNDC)
Delayed neutron spectroscopy – relatively unexplored field with
vast discovery potential.
Neutron array will be an essential part of FRIB Decay Station.
3
SSAP 2020 R. Grzywacz
Beta-delayed neutron emission
Strong 1n emission from 2n unbound states observed in decays
of N>50 gallium isotopes.
Direct measurement of neutron and gamma-emission probabilities.
R. Yokoyama et al.
Phys. Rev. C 100,
031302(R) (2019).
NEXT for direct reactions (α,n), (d,n):
neutron energies and angular distributions.
4
SSAP 2020 R. Grzywacz
TOF-based neutron detectors
What determines the energy resolution ?
Stop
ΔTL
L
Start Stop
Δ E 2 ΔT 2 2Δ L 2
Energy
resolution: ( ) ( ) (
E
=
T
+
L ) VANDLE array
Timing Detector
resolution Thickness
Efficiency ~ ΔTL ΔTT~1 ns ΔTL~ 3 cm
T~ 100 ns L~ 100 cm
Efficiency and resolution are in conflict.
Solution: localization of interaction in a thick detector !
5
SSAP 2020 R. Grzywacz
Neutron dEtector with Tracking (NEXT)
NEXT concept: tiled thin scintillator with the side light readout.
Neutron time-of-flight detector with good timing
(~0.5 ns ) and neutron/gamma discrimination
capabilities for decay and reactions studies.
should measure100 keV to 10 MeV neutrons
Stop Stop
●
The interaction localization improves energy resolution
●
Ej276 plastic scintillator allows for neutron-gamma
discrimination.
Start
●
Light readout with segmented photomultipliers
(or silicon photomultipliers)
6
SSAP 2020 R. Grzywacz
Resolution improvements for NEXT
Timing and tracking
Relative timing and position resolution have to be comparable
ΔT 2Δ L
( )(
T
∼
L )
Design parameters
(cost and technical feasibility)
- reduce TOF length (L)
- optimal segmentation
- best timing resolution
- electronic readout
133
In
TO F
1
E∼ 2
TOF
7
SSAP 2020 R. Grzywacz
Prototype of NEXT
Segmented scintillator with multianode PMT
position sensitive light readout.
8
SSAP 2020 R. Grzywacz
NEXT prototypes and manufacturing
optimization
Six prototypes: 5x Ej276 (n-γ) and 1xEj200:
●
Fabrication of Ej276 pixels a lot more challenging than Ej200 due
to mechanical properties of the material.
●
Better pixel separation when double reflector layer applied
●
Image distortions are caused by photocatode inhomogeneities
and some manufacturing inconsistencies
Ej200, single layer ESR Ej276, double layer ESR
polished sides, adhesive un-polished sides, adhesive
4x8 segments 5x10 segments
Ej276, single layer ESR Ej276, double layer ESR Ej276, double layer ESR
polished sides, adhesive polished sides, adhesive polished sides, air gap
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SSAP 2020 R. Grzywacz
Measurement at the University of Kentucky
Position and timing of mono-energetic neutrons should have a E.E. Peters
linear relationship. A.P.D. Ramirez
Test with mono-energetic neutrons S.W. Yates
●
University of Kentucky Accelerator Laboratory (UKAL)
●
3H(p,n) 3He reaction produces angular-dependent neutron energies
●
Collimated neutron beam
10
SSAP 2020 R. GrzywaczMeasurement at the University of Kentucky
1 MeV 1.4 MeV
J. Heideman et al. NIM A 946 (2019), 162528
n
11
SSAP 2020 R. GrzywaczNEXT model - neutron scattering
Multiple interaction of neutron in a detector
lead to distortion of the time and position response.
(Geant 4 modelling, C. Thornsberry)
12
SSAP 2020 R. GrzywaczOhio University measurement
9
Be( d,n) 27Al(d,n) at 7 and 7.5 MeV at 5 m TOF
Multiple prototypes tested
- reliable data down to 250 keV
- efficiency for EJ200 (10”) and Ej276 (5”) compatible
with GEANT 4 predictions with 20 keVee threshold
- efficiency is lower for Ej276 (10”)
Ej276
Ej200
OU participants:
Tom Massey,
Doug Soltesz
Yenuel Alberty-Jones
Joseph Derkin
13
SSAP 2020 R. GrzywaczOhio U measurement with thin Al target (500 ug)
9
Be( d,n) and 27Al(d,n) at 7 and 7.5 MeV @ 5 m TOF
●
High energy neutrons (5-13 MeV) with very short detector transit time (1- 2 ns)
●
Observed improvement in resolution after position correction
●
Effect limited by the start trigger time resolution (1 ns)
Thick target
Thin target
13 MeV
Joe Heideman
~100 ns, ∆T ~1 ns Josh Hooker
Shree Neupane
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SSAP 2020 R. GrzywaczNEXT prototype array
( more modules in production to reach 12 total)
@ANL
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SSAP 2020 R. GrzywaczBeta delayed neutron detection with VANDLE
RIBF RIKEN (11/2018)
Beta delayed neutron emitters beyond 78Ni
Production: fission of relativistic 238U beam
Search for 1n emission from 2n unbound states.
VANDLE (48 detector)+ HAGRID(12 detectors)
Ga
84
78
Ni
16
SSAP 2020 R. GrzywaczToward FRIB Decay Station Initiator (FDSi)
Prepare VANDLE for FDSi (improve efficiency)
- construction of 30 new VANDLE modules
- test performance of 160 cm-long bars (120 cm)
- Geant4 model and optimization
- finalize the NEXT array (total of 12 modules)
- merging VANDLE with the NEXT array
- scaled up prototypes from Ej200
20”-long module (in production)
3”x3” prototype (light guide design needed)
NSCL experiment in August 2020
(29F, island of inversion, Madurga et al. )
Approved proposal at RIBF RIKEN in 60Ca region
(Grzywacz et al.)
Proposals submitted to CARIBU with NEXT array
REA6 proposals (reactions)
FRIB Day-One experiments in 2022
17
SSAP 2020 R. GrzywaczUnderstanding of the βn neutron process
Shell-model and statistical model
Calculations use Hauser Feshbach model (Kawano coh3 code) combined with
shell-model B(GT) with cross-shell excitation using (Brown, NushellX).
Framework for the interpretation of the beta-n data (example: 83Ga decays).
Conclusions: neutron emission from the “compound” nucleus.
Underlying mechanism:
mismatch between wave functions in emitter and residual nucleus.
M. Alshudifat
18
SSAP 2020 R. GrzywaczSummary and plans
NEXT will provide improved energy resolution for fast neutrons, neutron detector for FDS.
VANDLE - workhorse for beta delayed neutron emission studies
(experiments at ORNL, NSCL, RIBF, CERN, ANL, ND), core neutron detector for the FDSi
NEXT prototype array constructed (50%) with H12700 PSPMT and new Anger logic boards
●
Finalized details of the construction of the NEXT module
●
Extensive characterization studies (sources, UKentucky, OhioU, ANL)
●
Proposed first experiments (ANL, NSCL) in collaboration with ORNL and LLNL
●
NIM published, two manuscripts in preparation (efficiency and scattering)
●
Construct and characterize 20” long and 3”x3” modules
VANDLE
●
Finalize the data analysis from the past experiments (Siegl, Keeler)
●
Prepare for beta-delayed neutron emission program at FRIB
●
Construct 30 more VANDLE modules
●
βn process modeling, collaborations with LANL
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SSAP 2020 R. Grzywacz20 SSAP 2020 R. Grzywacz
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