New Measurements Of Independent Fission Fragment Yields And Energies, And Prompt And Delayed Gammas For
Stockpile Stewardship Data Needs
Adam HechtUniversity of New Mexico
2020 Stewardship Science Academic Programs SymposiumFebruary 26, 4:10 pm
Project Goals
• Leverage our fission spectrometer UNM-SPIDER to measure yields and energies for 235U and 239Pu
• Add gamma detectors for fission product correlated prompt and delayed gammas
• Develop stand alone parallel plate ionization chamber (PPIC) for higher energy neutrons beams, measure fission tagged prompt and delayed gammas
Project RoadmapNNSA grant DE-NA0003901Funding began July 2019. 7 month status.
Milestones and Deliverables:Year 1:• Improvement and testing of existing fission fragment spectrometer.
This will include improved mass resolution. • Development of PPIC for high efficiency fission tagging.• For both instruments:
- coupling to gamma ray detectors for fission tagged prompt and quasi-prompt gammas.• This includes tests with 252Cf.
Year 2:• Fielding of both detectors on the neutron beamline at the LANSCE.• Collection of preliminary improved fragment yield data on 235U or 239Pu, coupled with gamma data.• Collection of preliminary PPIC data on 235U or 239Pu, coupled with gamma ray data.• Preliminary data analysis of correlated data for distribution.Year 3:• Continued data collection on 235U and 239Pu, focus on the one not examined in Year 2, also coupled with gamma ray data.• Continued data analysis of correlated data for distribution.• Submit high resolution 235U(n,f) and 239Pu(n,f) data set with correlated E, v, A, Z, and gammas to data evaluators.• Submit prompt and quasi-prompt fission gammas for 235U(n,f) and 239Pu(n,f) over a range of neutron energies to data evaluators.Beyond Year 3:• Continued fission fragment spectrometer correlated measurements of other fission targets.• Data collection on fission tagged gammas (and cross sections) for other actinides using PPIC.
From July 2019:
Supporting• PhD student Phoenix Baldez• PhD student Mark Wetzel• Undergraduate Lauren Crabtree
Publications• Measurements of 252Cf fission product energy loss through thin silicon nitride and carbon foils, and
comparison with SRIM-2013 and MCNP6.2 simulations, P. Baldez, S. Fellows, R.E. Blakeley, M. Tanguay, M.L. Wetzel, A.A. Hecht, D. Mayorov, F. Tovesson, J. Winkelbauer, Nuclear Instruments and Methods B 456, 142-147 (2019); https://doi.org/10.1016/j.nimb.2019.06.027
Talks/Conference Proceedings• Developments in New Measurements of Fission Cross-Sections, Fragment Yields, and Prompt and
Quasi-Prompt Gammas for Nuclear Data Needs, Adam Hecht, Phoenix Baldez, Mark Wetzel, International Workshop on Fission Product Yields 2019, Santa Fe, NM, Sept. 30-Oct. 4, 2019.
• The UNM Fission Spectrometer for individual fission fragment identification from 239Pu and 235U with correlated A, Z, E, and fission tagged gamma-ray data, Phoenix Baldez, Mark Wetzel, Adam Hecht. ANS Winter Meeting, Washington DC, 2019.
Phoenix Baldez
MarkWetzel
linear scale235U + thermal n
log scale235U + thermal n
Find A, Z, gammas
UNM E-V fission spectrometer
Extract A:
Correlated E,A,Z,NMeasure TOF – TOF detection region v = L/TOFMeasure E directly – ionization chamber
Extract Z: Ionization chamber as TPC, active cathode and anode
Extract N: A and Z N
UNM E-V fission spectrometer
Extract A:
Correlated E,A,Z,NMeasure TOF – TOF detection region v = L/TOFMeasure E directly – ionization chamber
SPIDER Collaboration
• SPectrometer for Ion DEtermination in fission Research (SPIDER)
• LANL led collaboration
• LANL SPIDER Spectrometer – Paired arms: 2v – 2E measurement to
correlate both fragments– many arm pairs systems to increase
efficiency– Not currently equipped to measure Z
• In this presentation: Experiments performed on UNM spectrometer– 235U with LANSCE FP12 “cold” n beam– 252Cf at UNM
Transmission TOF Components
Microchannel plateDetector (MCP)
40 ug/cm2 C
Ionization Chamber
Fission Product
cathode
Frisch gridanode
200 nm SiN windows
4000 6000 8000 10000 12000 14000 16000
IC Channel
4000
6000
8000
10000
12000
14000
16000
ToF
Chan
nel
IC (ch) vs. ToF (ch)
Raw Data: 235U
4000 6000 8000 10000 12000 14000 16000
IC Channel
4000
6000
8000
10000
12000
14000
16000
ToF
Chan
nel
IC (ch) vs. ToF (ch)
Raw Data with cuts on scatter: 235U
Now find mass byM = 2E/v2
… with corrections
Light fragments
Heavyfragments
Energy loss corrections
200 nm (58 ug) SiN window to IC180 nm (40 ug) electron conversion carbon foil
(thin foils very hard to handle)
Thin windows/foilsreduce
E loss correction(and broadening)
ELSource
ELCover ELFoil #1 ELFoil #2 ELSiN
TOF region
Combine v in TOF and E in IC to find A, but E different in TOF and ICAddback fits also deal with pulse height defects
What are the energy loss corrections?
How to calculate energy loss corrections for fission products?
P. Baldez, S. Fellows, R.E. Blakeley, M. Tanguay, M.L. Wetzel, A.A. Hecht, D. Mayorov, F. Tovesson, J. Winkelbauer, Measurements of 252Cf fission product energy loss through thin silicon nitride and carbon foils, and comparison with SRIM-2013 and MCNP6.2 simulations, NIM B 456, 2019.
ELSource
ELCover ELFoil #1 ELFoil #2 ELSiN
TOF region
0
1
2
3
4
5
6
7
8
9
60 80 100 120 140 160 180
Yield (%)
Mass Number (A)
U-235 + nth Fission Product Yield (%)(3 Runs, 50K Counts)
England & Rider University Spectrometer Results
Plus: Highly correlated particle-by-particle for E, v, A, Z, N, gammas soon
Mass resolution?
• fwhm/M• Need to calibrate with ion beam
since 252Cf (etc) has broad mass distribution
• Simulations…
Eic vs ETOF
TOFEic
Eic vs TOF
TOF
96
95
94
Eic vs TOF
TOF
96
95
94
4000 6000 8000 10000 12000 14000 16000
IC Channel
4000
6000
8000
10000
12000
14000
16000
ToF
Chan
nel
IC (ch) vs. ToF (ch)
But don’t see single mass stripes yet…
Light fragments
Heavyfragments
Mass resolution?
• TOF 63.9 ns, fwhm 0.372 ns, 2δt/t = 0.0058 = 1.16%– This plot is distribution of times for many particles, not precision for single particle
• Better MCPs, CFD, TDC? CAEN VME
psps
1m TOF measurementα from 239Pu
= 1.1% for 1 amu light A
distribution of times for many particles
Mass resolution?
• Foil thickness vs. TOF distribution fwhm
Alpha TOF
Mass resolution?
• IC Trinuc alpha measurement• 1.18% fwhm/E• 0.26 - 0.31% light - heavy fragments ?
Ionization Chamber and Z determination- axial time projection chamber
4
Fission Product
Cathode not grounded
electron drift
Frisch Grid
Anode
“active cathode” isolated by Teflon standoffTiming from cathode, anodeExamine electrons’ drift time to FG to extract range
cathode
Stopping is charge dependent
Range & Z- Active cathode design enables timing measurements- Determination of penetration depth/range
80 90 100 110 120 130 140 150 160
Mass (amu)
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
9
Mea
n R(
A) (c
m)
Mean R(A)
Measured Range
TRIM Light
TRIM Heavy
235U
Dealing with charge state distributions,Q, of Fission Fragments, not directly with Z
Example variations through foil of just a single atom species
Fig: N.K. Skobelev, Instruments and Experimental Techniques, 51, pp 351-357, 2008.Qav: R.D. Evans, The Atomic Nucleus, 1955.
y = 0.0267x - 0.0057
-0.2
-0.1
0
0.1
0.2
-10 -5 0 5 10
dA Heavy
y = -0.142x + 0.3064
-0.6-0.4-0.2
00.20.40.60.8
11.2
-4 -2 0 2 4 6
dZ light
y = -0.0438x - 0.0072
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-6 -4 -2 0 2 4 6
dZ heavy
y = 0.0591x - 0.0029
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
-10 -5 0 5 10
dE Light
y = 0.058x - 0.0043
-0.4
-0.2
0
0.2
0.4
-10 -5 0 5 10
dE heavy
y = 0.0335x - 0.0043
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-10 -5 0 5 10
dA Light
Zi(R,A,E)Light = -7.04225*(Ri-8.52)+0.23592*(Ai-96)+0.416197*(Ei-90.563)+0.16507
Zi(R,A,E)Heavy = -22.8311*(Ri-7.41)+.609589*(Ai-139)+ 1.324201*(Ei-57.036)-.39269
dR
dA
dR dR dR
dR
dZ
dA dZ
dR
dE
dE
SRIM SIMULATIONS
Functional dependence of R(Z,A,E) to get Z(R,A,E)
Zi(R,A,E)Light = -7.04225*(Ri-8.52)+0.23592*(Ai-96)+0.416197*(Ei-90.563)+0.16507
Zi(R,A,E)Heavy = -22.8311*(Ri-7.41)+.609589*(Ai-139)+ 1.324201*(Ei-57.036)-.39269
For Light:
For Heavy:
Not bad
Needs better simulation/calibration
Gammas in coincidence with well characterized individual particles
quasi-prompt to delayed gamma detectionFF arrive ~ 50 ns post fissionPrompt gamma detection
Already have 3 Ortec GMX 25% HPGe (good around neutrons) and other gamma detectors
Detectors look good
Already have 3 Ortec GMX 25% HPGe (good around neutrons) and other gamma detectors
Parallel Plate Ionization Chamber (PPIC) for fission tagged gamma rays
Build IC based on Parallel Plate Ionization Chamber (PPIC) for fission tagging, good FF/α discrimination
F. Tovesson, T. S. Hill, Phys. Rev. C 75, 034610 (2007).
Fission spectrometer efficiency currently ~10 -4PPIC ~ 1
• Fission tagged gammas, but not v,Z,N coincidence• Discriminate alpha vs FF
• Mockup at UNM• The LANL PPIC may be available
Current Workmeasurements
• Testing IC at UNM with 252Cf• Examining 100 nm (replace 200 nm) windows
for improved resolution• Wrote beamtime proposal for 239Pu data at
LANSCE• Will calibrate FFS IC at LBL 88” cyclotron
– Test full FF Spectrometer?
Current Workequipment
• Ordered new MCPs for TOF• Acquired new SiN windows for IC
– designing new window layout with Norcada• Creating gas interlock – to run with thinner windows
– Ordered pressure gauge reader with logic output• Ordering CAEN power supply with
– overcurrent shutoff– logic input for shutoff– latch off at shutoff
• Will look at getting LANL PPIC running vs. building a new device
Plans• Improve mass resolution of full spectrometer• Get PPIC up and running• Test both with 252Cf and Ge detectors• Run 239Pu, 235U with fission tagging in PPIC and
with correlated data in full spectrometer• Look at target availability and measure others
Thank You!
Phoenix Baldez
Adam Hecht
MarkWetzel
Schmitt data from: H.W. Schmitt, J.H. Neiler, F.J. Walter, Phys. Rev. 141, 1966
Heavy fragment Z reconstruction too sensitive to small changes in E?
Zi(R,A,E)Light = -7.04225*(Ri-8.52)+0.23592*(Ai-96)+ 0.416197*(Ei-90.563)+0.16507
Zi(R,A,E)Heavy = -22.8311*(Ri-7.41)+.609589*(Ai-139)+ 1.324201*(Ei-57.036)-.39269
For Light:
For Heavy:
Not much Bragg peak for fission products
Do see range difference
140Xe, 70 MeV
90Sr, 115 MeV
80Ge, 121 MeV
Cathode not grounded
electron drift
FG Anode
Z determination - Active Cathode (> 0.5 MeV/amu)
Cathode not grounded
electron drift
Range Z dependent
Measure range from Cathode vs. anode time= IC ∆t
using e drift velocity
FG Anode
T. Sanami, M. Hagiwara, T. Oishi, M. Baba, M. Takada, NIM A 589, 2008.