Beta-Delayed Neutron Emission Spectroscop with VANDLE and NEXT Neutron Arrays
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Beta-Delayed Neutron Emission Spectroscop with
VANDLE and NEXT Neutron Arrays DOE DE-NA0003899
06/2019-06/2022
Neutron dEtector PI: Robert Grzywacz
with xn Tracking(
University of Tennessee
Department of Physics and Astronomy
Supported:
Dr. Cory Thornsberry (until October 2019)
Dr. Kevin Siegl (from January 2020)
Dr. Joe Heideman (from January 2021)
M.Sc. T. King (until December 2021, now ORNL)
Graduate students:
Joe Heideman (NEXT) graduated (Dec 2020)
Shree Neupane (NEXT) (until Sep 2019, now NSF MRI)
Andrew Keeler (VANDLE) current
Ian Cox (VANDLE) current
Undergraduate students:
Donnie Hoskins, Corey Chalvers
NSF MRI Noritake Kitamura
Presentations given at conferences and meetings
APS, LECM
Ongoing collaborations with LANL, LLNL
in experiment and theory.
1
SSAP 2021 R. Grzywacz
Beta-delayed neutron emission
Beta-decay Neutron emission
(strength distribution model)
Neutron
separation
energy
2
SSAP 2021 R. Grzywacz
Beta-delayed neutrons and Hauser-Feshbach model
T. Kawano, P. Talou, I. Stetcu, and M. B. Chadwick,
Nuclear Physics A 913, 51 (2013).
M. R. Mumpower, T. Kawano, and P. Möller, Physical
Review C 94, 064317 (2016).
3
SSAP 2021 R. Grzywacz
Beta delayed neutron emitters
βxxn and the r-process
4
SSAP 2021 R. Grzywacz
Beta delayed neutron emitters
βxxn and the r-process
5
SSAP 2021 R. Grzywacz
Beta-decay strength measurements
Decay spectroscopy of 72Co and 70Co
(Analysis: A. Keeler and K. Siegl)
Probing the proton shell gap at Z=28
Preliminary neutron
spectrum deconvolution
72
Co
Preliminary extraction of B(GT)
6
SSAP 2021 R. Grzywacz
Beta-delayed neutron emission
Strong 1n emission from 2n unbound states observed in decays
of N>50 gallium isotopes.
●
Experimental investigation of neutron emission model through 1n/2n
●
Use LANL coh3 code (T. Kawano) to model 1n/2n competition.
Changes of r-process
abundance pattern
R. Yokoyama et al. Phys. Rev. C 100,
031302(R) (2019).
86
Ge 85
Ge Ge
84
86
Ga βx
n
n
Use statistical and shell-model
level densities !
7
SSAP 2021 R. Grzywacz
What is the mechanism of the neutron emission:
“direct” or via “compound nucleus” ?
Neutrons - no Coulomb barrier !
Direct - fast emission (broad), sensitive to nuclear structure.
conserved energy and angular momentum (light nuclei).
Compound - slow emission (narrow), non-sensitive to nuclear
structure, conserved energy and angular momentum.
“Bohr hypothesis: The properties of the C. N. do not depend upon the detailed way of formation.”
What happens near the doubly-magic nuclei where the
level-densities are low, but Pβxxn are strong !
T. Kawano, P. Talou, I. Stetcu, 137I
and M. B. Chadwick,
Nuclear Physics A 913, 51 (2013).
8
SSAP 2021 R. Grzywacz
In the decay of 134In excited states in
134
Sn, 133Sn and 132Sn are populated.
Neutron emission from 134Sn
“compound nucleus” (?)
GT states at ~ 7 MeV
Large:
P1n~0.8, P2n~0.1
9
SSAP 2021 R. Grzywacz
Population of single particle states in 133Sn
Test of the “compound nucleus” approach
Small spectroscopic overlap
between the 134In p-h state and
single particle states in 133Sn.
Decay of 133In:
Gamma emission from
Experiments at unbound states in 133Sn.
ISOLDE CERN M. Piersa et al. Phys. Rev. C 10
SSAP 2021 R. GrzywaczPopulation of single particle states in 133Sn
Neutron spectroscopy
Neutron spectrum
deconvolution
Determine branching ratios
to excited states in 133Sn
J. Heideman et al.
in preparation 11
SSAP 2021 R. GrzywaczPopulation of single particle states in 133Sn
Comparison with the coh3 model predictions
π Jπ=4-
J =3 -
π
J =5 - Jπ=6-
Jπ=7- Jπ=8-
J. Heideman et al.
in preparation
12
SSAP 2021 R. GrzywaczPopulation of single particle states in 133Sn
Shell effects in delayed neutron emission ?
Neutron emission proceeds through overlap of the
narrow GT state with states which have large widhts.
Signature: population of 133Sn excited states.
Calculate neutron emission
widths using optical model
and spectroscopic factors.
J. Heideman et al.
in preparation 13
SSAP 2021 R. GrzywaczTOF-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 !
14
SSAP 2021 R. GrzywaczNeutron 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
15
SSAP 2021 R. GrzywaczResolution 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
16
SSAP 2021 R. GrzywaczEssential components
●
n-γ discirminatin plastic (EJ276) array 8x4 segments
(UTK workshop and Agile Engineering)
●
Each segment 0.6x1.27x25.4 cm3
●
Separation with Enhanced Specular Reflector ESRTM (3M)
●
Hamamtsu H12700 multianode PMT
●
Anger logic with integrated amplifiers (10x) by Vertilon Co.
●
Digital data acquisition system (XIA Pixie16 RevF 250/16b)
(UTK/XIA/ORNL front-end, UTK analysis framework c++, root)
17
SSAP 2021 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)
●
Observed improvement in resolution after position correction
●
Effect limited by the start trigger time resolution (1 ns)
●
Efficiency curve: model vs. measurement
Thick target
Thin target
13 MeV
~100 ns, ∆T ~1 ns Joe Heideman
Josh Hooker
Shree Neupane
18
SSAP 2021 R. GrzywaczFirst Demonstration of NEXT in βxn emission
experiment at ANL CARIBU
S. Neupane, J. Heideman, K. Siegl and M. Cooper
19
SSAP 2021 R. GrzywaczVANDLE and NEXT at NSCL
(29F N=20 island of inversion: PI M. Madurga)
Yokoyama et al. NIM A
937, 93-97(2019)
20
SSAP 2021 R. GrzywaczVANDLE+NEXT experiment at NSCL
Technical complexity:
48 VANDLE modules at 100 cm
10 NEXT modules at 50 cm
3 clovers (ORNL)
YSO segmented implantation
array + ion veto detectors
Beta-trigger vetos
Two independent and
synchronized digital
data acquisition systems
COVID-19 restrictions !
21
SSAP 2021 R. GrzywaczNSCL experiment with 17N and 29F
OCT/NOV 2020 PI: M. Madurga
Implant/decay profiles in YSO
Preliminary analysis: S. Neupane, J. Heideman,
N. Kitamura
22
SSAP 2021 R. GrzywaczFRIB DECAY STATION initiator (FDSi) Discrete neutron spectroscopy at FRIB discovery potential 2
2020-2021 accomplishments
●
First measurement with NEXT at ANL with with refractory βxn-precursors
●
First measurement with NEXT at NSCL in N=20 island of inversion
●
VANDLE measurement in the island of inversion
●
J. Heideman graduated in December 2020
●
Development of βxn-emission model using SM+HF
●
A. Keeler near completion of his dissertation
●
Manuscripts in preparation
●
Completed 14 NEXT modules
●
Advances in triggering scheme for NEXT operations
●
New SiPM based trigger detector for NEXT
●
Timely progress on development of larger array of 40-50 detectors funded
through NSF MRI funding
●
Approved experiment to study decay of 134In at ISOLDE CERN
●
VANDLE to become a critical part of the FRIB Decay Station Initiator
24
SSAP 2021 R. GrzywaczYou can also read
