Application of CLTDs* for the investigation of Z-yield distributions - - PowerPoint PPT Presentation

Application of CLTDs* for the investigation of Z-yield distributions

• f fission fragments

NUSTAR Annual Meeting 2018, GSI (Germany) 26th Feb – 2nd Mar 2018

Talk by: Santwana Dubey (PhD) PhD Supervisor – Prof. Dr. Peter Egelhof

Institute of Physics, Johannes Gutenberg University Mainz GSI Helmholtz Center for Heavy Ion Research Darmstadt

*CLTDs – Calorimetric Low Temperature Detectors

Motivation

motivation for studying fission fragment yields:

• Various nuclear energy applications
• better understanding of the nuclear fission process
• data relevant for reactor physics

Application of CLTDs for fission studies!

neutron fission fragments target nucleus neutrons

Thermal neutron induced fission reactions

Outline

 Calorimetric Low Temperature Detectors:

• Concept
• Advantages
• Design

 Nuclear Charge Distribution Measurements:

• Experimental Set-up
• Preliminary results:
• First time direct Z-yield determination for heavy fragment masses
• Using passive absorber method
• Proton odd-even effect in masses approaching symmetric fission
• for 239Pu & 241Pu
• Important for nuclear model description near scission
• Precise 92Rb & 96Y yields
• for 235U, 239Pu, 241Pu (nth, f)
• Important for reactor antineutrino anomaly studies

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CLTDs: Introduction

particle phonons thermometer °

Calorimetric Detector → detecon of heat Idea: detection of particle energy independent of ionization processes

Interaction of ions with matter:

• Primary:

Ionizaon → ionizaon detectors

• Secondary:

thermalizaon → calorimetric detectors (conversion of energy to heat  detection of thermal phonons)

Potential Advantages:

• energy resolution
• energy linearity
• detection threshold
• variety of detector materials

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CLTDs: Advantages

30 60 3k 6k

Energy [MeV] Pulse height [ADC channels]

4He 13C 197Au 238U

C, Au, U

10 20 1k 2k

Energy [MeV] Pulse height [ADC channels]

13C 197Au 238U

15 20 25 300

Energy [MeV] Counts/bin E(FWHM)= 2808 keV

15 20 25 1k

Counts/bin Energy [MeV] E(FWHM) = 91 keV

CLTDs Si Detector Pulse Height Defect

(13C, 197Au, 238U )

Energy Resolution

(238U @ 20.7MeV) Plots from: Kraft-Bermuth et al., Rev. Sci. Instrum. 80, 103304 (2009)

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Losses at energy conversion: Due to dead layer, charge recombination More complete energy detection →Beer resoluon and linearity

CLTDs: Detection Principle

ΔT t2 t1

time thermal signal: temperature

Absorber: Particle energy is converted into heat,

• High sensitivity for small specific heat c and small mass
• c ̴ (T3/ƟD

3) from Debye law (for insulators, superconductors)

• Operation at Low Temperatures

m c E ΔT  

T  T + T

Thermometer Heat sink Incident particle Absorber

with energy E

6 Rise-Time 1 – 10 s Decay-Time (C/k) 100 s – 10 ms

CLTDs: Detection Principle

Thermometer: Transition Edge sensors are used.

• Resistance (superconductor) biased with constant current.
• ∆T→∆R(T)→∆V voltage signal is detected.
• Detector temperature stabilized in phase transition region  high dR/dT.

1.60 1.62 1.64 1.66 50 100 150

super- conducting normal state R [k] T [K] transition region: dR/dT  const

• peration

temperature

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T  T + T

Thermometer Heat sink Incident particle Absorber

with energy E

CLTDs: Current Detector Design

Heater strip 25μm Au/Cr strip Operational Temperature: 1.5 – 1.6 K

Transition Edge Sensor 10 nm thick meander shaped Al-layer R (T) Heat sink 3 x 3 x 0.43 mm3 T ~ 1 K Incident particle

Sapphire absorber

T  T + T

Thermometer

Sapphire absorber

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Active area: 15×15mm2

• S. Kraft-Bermuth et al., Rev. Sci. Instrum. 80, 2009

A.Echler et al., J. Low Temp. Phys. 167, 2012,

(25 pixels)

CLTDs: Current Detector Design

Operational Temperature: 1.5 – 1.6 K

T ~ 1 K Heat sink Incident particle

Sapphire absorber

T  T + T

Thermometer

Sapphire absorber

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windowless 4He bath cryostat

Z- distributions of fission fragments (nth,f)

symmetry region light fragment group heavy fragment group

K.H. Schmidt et al.

Methods for Z- separation:

• Radio chemistry
• -spectroscopy

restricted to particular nuclides

• Passive-absorber method
• U. Quade et al., Nucl. Phys. A487 (1988) 1

best Z-resolution with:

• Parylene C absorbers
• ionization chamber

restricted to light fragment group

energy

E(Z) = E0 - E(Z) Z2 Z1

residual energy

absorber E(Z) energy detector fission fragments A = const E0(Z)= const

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Z- distributions of fission fragments (nth,f)

symmetry region light fragment group heavy fragment group

K.H. Schmidt et al.

Methods for Z- separation:

• Radio chemistry
• -spectroscopy

restricted to particular nuclides

• Passive-absorber method
• U. Quade et al., Nucl. Phys. A487 (1988) 1

best Z-resolution with:

• Parylene C absorbers
• ionization chamber

restricted to light fragment group Preliminary results from CLTDs using SiN absorber foils:

• First time possible to measure in the heavy mass

region.

• New measurements in the light mass region

approaching symmetric fission for 239P(nth,f) and

241Pu(nth,f).

• Precise yield determination of 92Rb, 96Y.

SiN foils:

• Homogeneity
• High thermal stability
• Extreme hardness
• Chemical inertness

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Target cryostat Electrostatic deflector Dipole magnet High flux neutron source LOHENGRIN mass separator Filters a specific A, E and Q but not Z.

Investigation of Z- distributions of fission fragments (nth,f)

CLTD array SiN absorber foil stacks

10×16mm

Experimental Set-up

Manipulator for changing foil stacks

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Z-Resolution: Optimum thickness of SiN

1 2 3 4 5 6 7 8 9 20 30 40 50

A=96, Z=40 A=89, Z=35

 foil thickness [µm]

Systematic studies: Z-Resolution vs SiN foil thickness

3000 4000 100 200 300 36Kr 35Br 37Rb

8m

5000 6000 100 37Rb 36Kr 35Br

7µm

10000 11000 100 200 300 36Kr 35Br 37Rb

5m

7000 8000 100 200 300 400 36Kr 35Br 37Rb

6µm

12000 100 200 300 36Kr 35Br 37Rb

4m

21000 22000 100 200

1m

residual energy spectra A = 89, E= 94MeV counts Residual energy (a.u.)

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80 90 100 110 0.00 0.05 0.10 0.15

Sr Rb Kr

Q=20

isotopic yield [a.u.] Energy (MeV)

A = 92

Procedure for determining Z-yields

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30 35 50 100 150

241Pu

A=108 Counts/bin Residual Energy (MeV)

5 10 15 50 75 100

Burn-up Exponential fit Burn-up Time (Days)

235U

 fit of spectrum

• relative Z-Yield
• line shape from Tandem

experiment (for heavy masses)  Z-Identification  take into account

• energy dependence
• electronic charge state

dependence (ns-isomers)  absolute normalization

• target burnup

for Z-Yield of one mass:  upto 300 spectra to be analyzed

15 20 25 30 5 10 15

Sr Rb Kr

isotopic yield [a.u.] ionic charge state, Q

E = 94MeV

A = 92 90 100 110 12k 13k

peak position mass

Z=39

241Pu

E=100MeV

Z=41 Z=43

45Rh 44Ru 43Tc 42Mo

Resolution

Quality of Z-Separation

CLTD+SiN: good resolution & linearity →Possibility to measure in symmetry & heavy mass region

15 32 36 40 44 48 52 20 40 60

CLTD + SiN (ILL 2016, E = 94-100 MeV & 80 MeV for Z=52) CLTD + SiN (MLL 2016, E/A = 80/127 MeV/u)

• IC + Parylene C (Djebara et al., E = 101-106 MeV)

IC + Parylene C (Quade, E = 98 MeV)

Z/Z Nuclear Charge Z

80 90 100 110 120 130

Mass

Light mass region

37Rb 36Kr 35Br

A=89

7m SiN foils

Ein=94MeV 235U(nth,f)

45Rh 44Ru 43Tc 42Mo

A=108

6m SiN foils

Ein=100MeV

241Pu(nth,f)

counts Residual energy (a.u.)

Symmetry region Heavy mass region

A=130

51Sb 50Sn 52Te

Ein=88MeV 239Pu(nth,f)

6m SiN foils

• A. Djebara et al. Nuclear Physics A496 (1989) 346
• U. Quade et al., Nucl. Phys. A487 (1988) 1

Heavy mass analysis

First direct Z-yield measurements in Heavy mass region:

• Standard method for unresolved peaks: Constrained fits with
• good statistics (≈10000 counts)
• good knowledge of response function
• With same set-up, measurements at similar mass and energy at MLL tandem

tandem accelerator, allow to estimate the response function for the residual energy spectra.

• Stable fits for measured distributions.

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5000 5500 400 800

A = 130 E = 88MeV 6 SiN foils Counts Residual Energy (a.u.)

Z=51 Z=50 Z=52 5000 5500 200 400 600 A = 129

E = 88MeV 6 SiN foils Counts Residual Energy (a.u.)

Z=51 Z=50 Z=49 5000 5500 200 400 Z=49 Z=50

A = 128 E = 88MeV 6 SiN foils Counts Residual Energy (a.u.)

Z=51

Preliminary Results

Heavy masses Z-yields Analysis

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128 130 132 134 136 138 200 400 d1 d2

separation Mass

128 130 132 134 136 138 50 100

width parameter Mass

128 130 132 134 136 138 75 100 125 150

asymmetric parameter Mass

128 130 132 134 136 138 4250 4500 4750 55 54 53 52 51 50

xc1 xc2 xc3

Peak Position (a.u.) Mass

Z=49

Z-Identification width separation asymmetry

128 130 132 134 136 138 0.0 0.2 0.4 0.6 0.8 1.0

Relative Z-yields

Z=55 Z=51 Z=52 Z=53 Z=54

Mass

Z=50 Z=49

Heavy masses Z-yields: 239Pu(nth,f)

18 128 130 132 134 136 138 0.0 0.2 0.4 0.6 0.8 1.0

Z=54 Z=53 Z=52 Z=51

Relative Z-yields Mass

Our Expt.

• Prelim. Results

ELOH.=80MeV *A. Bail et al. Phys. Rev. C 84 (2011) 034605 Gamma Spectroscopy*

• Incl. all E & Q

Jeff Data base 3.1.1

128 130 132 134 136 138 0.0 0.2 0.4 0.6 0.8 1.0

Z=51 Z=50 Z=52 Z=53 Z=54 Z=55

Relative z-yields Mass

Z=50

241Pu(nth,f) Z-yield

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110 105 100 95 90 0.0 0.2 0.4 0.6 0.8 1.0 Our Expt Z=45 Z=42 Z=41 Z=40 Z=39 Z=38 Z=37 Z=43 Z=44

Relative Z-yields Mass

Z=36

First LOHENGRIN data on Z-yields for A > 89 were determined for 241Pu(nth,f)

Good comparison with P.Schilleebeeckx et.al. data – measurement with a different technique (Cosi-Fan-Tutte Spectrometer)

110 105 100 95 0.0 0.2 0.4 0.6 0.8 1.0

Z=43 Z=41

Relative Z-yields Mass

Z=39

Our Expt.

• P. Schillebeeckx et.al, Nucl. Phys. A580, 15(1994)
• Prelim. Results

239Pu(nth,f) Z-yield

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Also new data for A = 109 to 113 were determined for 239Pu(nth,f)

115 110 105 100 95 90 85 0.0 0.2 0.4 0.6 0.8 1.0 Z=46 Z=45 Z=44 Z=43 Z=42 Z=41 Z=40 Z=39 Z=38 Z=37 Z=36

Relative Z-yields Mass

Solid - Our Expt. Open - C. Schmitt et.al., Nuclear Physics A430, 21 (1984)

• Prelim. Results

Odd-Even effect near symmetry

21 115 110 105 100 95 90 85

• 1.4
• 1.2
• 1.0
• 0.8
• 0.6

Our Expt.

36 38 40 42

Z = ZUCD - <Z> Mass of Light Fragment

Z=44

241Pu(nth, f)

115 110 105 100 95 90 85

• 1.4
• 1.2
• 1.0
• 0.8
• 0.6

Z = ZUCD-<Z> Mass of Light Fragment

Our Expt.

• C. Schmitt et.al., Nucl. Phys. A430, 21(1984)

239Pu(nth,f)

Z=44 42 40 38 36

∆Z = deviation from “democratic” distribution of neutron excess ∆Z = ZUCD - <Z> ZUCD(241Pu) =

• ZUCD(239Pu) =
• Zheavy=50

Zheavy=50

symmetry symmetry

• Prelim. Results

Odd-Even effect near symmetry

22 115 110 105 100 95 90 85

• 1.4
• 1.2
• 1.0
• 0.8
• 0.6

Our Expt.

36 38 40 42

Z = ZUCD - <Z> Mass of Light Fragment

Z=44

241Pu(nth, f)

115 110 105 100 95 90 85

• 1.4
• 1.2
• 1.0
• 0.8
• 0.6

Z = ZUCD-<Z> Mass of Light Fragment

Our Expt.

• C. Schmitt et.al., Nucl. Phys. A430, 21(1984)

239Pu(nth,f)

Z=44 42 40 38 36

Zheavy=50 Zheavy=50 Rise in ∆Z towards corresponding heavy mass with closed shell, Z=50 For the first time in case of 239Pu, we observe a drop in ∆Z beyond Zheavy=50

symmetry symmetry

• Prelim. Results

92Rb & 96Y yield

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Motivation

Motivation for investigating Mass 92: The Reactor Antineutrino Anomaly  5.7% deficit of measured antineutrinos as expected from β-decay data of fission fragments

• G. Mention et al., Phys. Rev. D83 (2011) 073006

possible explanations:  4th non standard „sterile“ neutrino  wrong Z-yields of fission fragments

92Rb & 96Y yield

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• A. A. Sonzogni et al., Phys. Rev. C91 (2015) 011301 (R)

for 235U target: contribution of 92Rb to the β-spectrum at 5.5 MeV  JEFF 3.1.1 data basis: 21.6%  S.V.Tipnis et al. Phys. Rev. C 58, 905 (1998): 30.0%

• A. A. Sonzogni et. al.:

92Rb

96Y

92Rb yield

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92Rb

• Agreement with standard Data bases
• In case of 235U, disagreement with data by S.V.Tipnis et al. Phys.
• Rev. C 58, 905 (1998)

Several measurements at different kinetic energies and ionic charges were made to precisely determine the cumulative yields

96Y yield

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96Y

Our Expt. JEFF JAEA Tipnis 0.01 0.02 0.03 Our Expt. JEFF JAEA 0.01 0.02 0.03

235U(nth, f)

96Y independent yield dataset

241Pu(nth, f)

dataset

• In agreement with the standard Data bases.

S.V. Tipnis et al. Phys. Rev. C 58, 905 (1998)

Summary

• Successful application of CLTDs for Z-yield measurements.
• CLTD + SiN: First time direct Z-yield measurements of heavy

fragment masses. A new method to measure also masses inaccessible with current technology e.g. gamma spectroscopy.

• Odd-even effect approaching symmetric fission for 239Pu & 241Pu

Important measurements for nuclear fission model description near scission

• Precise 92Rb & 96Y yields for 235U, 239Pu, 241Pu (nth, f)

Highest contributor to neutrino oscillations and reactor antineutrino anomaly studies

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Thank you

• S. Dubey1,2, A. Echler1,2, P. Egelhof1,2, P. Grabitz1,2, M. Mutterer1, W.

Lauterfeld2, S. Stolte2, S. Kraft-Bermuth3, P. Scholz3, S. Bishop4, J. Gomez4, A. Blanc5, U. Köster5, F. Gönnenwein6

1GSI, Darmstadt, Germany 2University of Mainz, Germany 3University of Giessen, Germany 4Technical University Munich, Germany 5ILL Grenoble, France 6University of Tübingen, Germany

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