Fission studies at R3B using the SOFIA setup NUSTAR week 2019 Gif - - PowerPoint PPT Presentation

Fission studies at R3B using the SOFIA setup

NUSTAR week 2019

Gif -sur-Yvette, France

September 25 2019

• A. Chatillon (CEA, DAM, DIF) for the R3B/SOFIA collaboration

SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Why studying fission at R3B ?

I - Large physics case: applications, r-process, understanding the reaction for models SOFIA@R3B: correlation of several fission observables for a complete description (A1,Z1) (A2,Z2)

FF1 FF2 neutrons gamma

YIELDS: Y(Ai,Zi) EVOLUTION WITH E* BARRIER

T . I c h i k a w a e t a l . , P R C 8 6 ( 2 1 2 ) 2 4 6 1

PES: static properties dynamics propagation

P R O M P T E M I S S I O N

(A,Z,E*)

compound nucleus Transient time

PROBABILITY

NUSTAR week SOFIA: Fission@R3B

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Why studying fission at R3B ?

II - To avoid the limitation due to direct kinematics DIRECT KINEMATICS: FF WITH LOW RECOIL ENERGY IN THE LAB. FRAME

Beam = neutrons, light charged particles, γ & Target = actinides

Isotopic yields are incomplete nuclear charge from energy loss measurement: ⇒ limitation to Z≤42 mass from total energy measurement: ⇒ resolution around 4 mass unit FWHM targets limited to long-lives nuclei very low efficiency due to the 4-π emission ⇒ low statistics

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Why studying fission at R3B ?

II - To avoid the limitation due to direct kinematics... ... thanks to the powerful tool of the inverse kinematics at relativisitic energy INVERSE KINEMATICS AT 700 A.MeV: (Z,A) IDENTIFICATION FROM ∆E-Bρ-ToF

Radioactive beam & Surrogate reactions

FRS + R3B : (Z,A) identification of the compound nucleus and both fission fragments after neutron emission ∆Z = 0.35 charge unit FWHM ∆A = 0.5 to 0.8 mass unit FWHM

1000 2000 3000 4000 5000 6000 7000 8000 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64

counts nuclear charge (Z)

analysis by L. Grente electromagnetic induced fission

total prompt neutron multiplicity from ACN = AFF1 − AFF2 Use of radioactive beams: broad range of fissioning nuclei Use of surrogate reactions to produce the compound nucleus: ⇒ coulex induced fission: accurate measurement of Y(A,Z) and νtot at E ∗

CN ∼14 MeV

⇒ (p,2pf): first experiment in 2020 to measure E∗ in coincidence: Complementary experiment! very high geometrical efficiency: around 90 % (from 236U(γ,f) data in 2014)

NUSTAR week SOFIA: Fission@R3B

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Two experiments in 2012 and 2014 at R3B with ALADIN

2012: Coulex-induced fission in the uranium and thorium regions (J. Taieb et al.) 2012: Spallation-fission of 208Pb (J. Benlliure et al.) 2014: Coulex-induced fission of 236U (J. Taieb et al.)

∆E-Bρ-ToF applied at FRS

2.56 2.565 2.57

A / Z

90.5 91 91.5 92 92.5 93 93.5

n u c l e a r c h a r g e

5 10 15 20 25 30 35 40 45 50 x10

3

236U 234Pa

analysis by L. Grente

counts

∆E-Bρ-ToF applied at Cave C

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Accurate yields along the uranium chain

Error bars are shown in figures ⇒ Elemental yields: σasym ≤ 1% and σsym ≤ 2% ⇒ Isotopic yields: σlight ≤ 2%, σsym ≤ 3% and σheavy ≤ 5%

1.6 2 2.4 2.8 43 44 45 46 47 48 49

Y(Z) [%] nuclear charge (Z)

234U 235U 236U 238U

10 11 12 13 14 15 16 52 53 54 55 56

Y(Z) [%] nuclear charge (Z)

234U 235U 236U 238U

2 4 6 8 10 12 14 16 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64

Y(Z) [%] nuclear charge (Z)

234,235 234,235 236 238

analysed by : J.-F. Martin ( U), G. Boutoux ( U), L. Grente ( U) and E. Pellereau ( U) 234U 235U 236U 238U 0.5 1 1.5 2 2.5 3 3.5 45 50 55 60 65 70 75 80 85 90 95

Y(Z,N) [%] number of neutrons (N)

235

analysed by : J.-F. Martin ( U) Z=32 Z=33 Z=34 Z=35 Z=36 Z=37 Z=38 Z=39 Z=40 Z=41 Z=42 Z=43 Z=44 Z=45 Z=46 Z=47 Z=48 Z=49 Z=50 Z=51 Z=52 Z=53 Z=54 Z=55 Z=56 Z=57 Z=58 Z=59 Z=60

J.-F. Martin, J. Taieb et al., Eur. Phys. J. A 51 (2015) 541

• E. Pellereau, J. Taieb et al., Phys. Rev C 95 (2017) 054603

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

From asymmetric to symmetric fission along the thorium chain (I)

First observed from Y(Z) measurement in the 90’s (K.-H. Schmidt et al., NPA 665 (2000) 221) SOFIA: measurement of Y(Z), Y(N), Y(A) and prompt-neutron multiplicity

Y(Z) [%]

5 10 15 20 35 40 45 50 55

nuclear charge (Z)

Schmidt et al. SOFIA 35 40 45 50 55 35 40 45 50 55

Y(N) [%]

2 4 6 8 10 12 50 55 60 65 70 75 80 85

number of neutron (N)

50 55 60 65 70 75 80 85 50 55 60 65 70 75 80 85

Y(A) [%]

230Th 2 4 6 8 80 90 100 110 120 130 140 150

mass (A)

226Th 80 90 100 110 120 130 140 150 222Th 80 90 100 110 120 130 140 150

• A. Chatillon, J. Taieb et al., Phys. Rev C 99 (2019) 054628

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

From asymmetric to symmetric fission along the thorium chain (II)

Probe the scission configuration thanks to νtot(Z) ⇒ νtot(Z) increases with the Q2-deformation of the fission-fragments Prompt neutron multiplicity drops at symmetry

5 10 15 35 40 45 50 55 60

Y(Z) [%]

35 40 45 50 55 35 40 45 50 55

nuclear charge (Z)

35 40 45 50 55 3 4 5 6 7

〈νtot〉

236U 230Th 226Th 222Th

• A. Chatillon, J. Taieb et al., in preparation

new compact scission configuration at symmetry for the light thorium totaly different from the known elongated symmetric scission mode in uranium region

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

208Pb(p,f) at 500 A.MeV Application: characterize the spallation neutron sources and secondary beam facilities Understanding of the dynamics in fission through the dissipation parameters Isotopic identification of both FF: Z1+Z2 are obtained unambigously in coincidence with ⇒ fission cross section ⇒ neutron excess in the fission fragments

Ground to saddle dynamics

cross section

• J. L. Rodriguez-Sanchez et al., Phys. Rev C 91 (2015) 064616

Saddle to scission dynamics

neutron excess

• J. L. Rodriguez-Sanchez et al., Phys. Rev C 94 (2016) 061601 (R)

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Accepted proposal for Fission@R3B (s455)

• 1. Temperature dependance of shell effects in the PES and energy sharing between FF:

⇒ (p,2p) induced fission of 238U primary beam

• 2. Fission barrier around N=126 in Po isotopes:

⇒ (p,2p) induced fission of radioactive beams

• 3. Symmetric to asymmetric fission in neutron deficient A=180-210 nuclides:

⇒ coulex induced fission of radioactive beams

Setup based on a common basis

primary beam

238

U fragmentation target (Be) stripper (Nb) stripper (Cu) degrador (Al) scintillator

flight path ~ 138m (beam)

(∆E,Θ)

(x1,y1)

T win MUSIC

MWPC 1

GLAD with He

MWPC 3 T

• F wall

central cathode anode planes

1,2 1,2

(x3,y3)

1,2

MWPC0 (x,y) Triple-MUSIC (ΔE, Θ) cathode anode plane scintillator

flight path ~ 8 m (fission-fragments)

(x2,y2)

MWPC 2

1,2

(Θ,Φ)

1,2

Anodes U C

Active T arget: coulex

TARGET AREA

LH2+Si+CALIFA: (p,2pf)

NUSTAR week SOFIA: Fission@R3B

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

(p,2p) induced fission of primary 238U beam. J. Benlliure et al.

Damping of the shell effects with E ∗ & Energy sharing between FF AIM: Evolution of the fission observables as a function of E ∗ : from Bf to 80 MeV Yields and prompt-neutron multiplicity depends on E ∗ and (ACN,ZCN) BUT: Difficult to study such effect in direct kinematics SOLUTION: Couple R3B/SOFIA with LH2 target, the Si tracker and CALIFA ⇒ 238U(p,2pf): tracking of the protons to measure E ∗ ⇒ R3B/SOFIA: isotopic identification of both FF and total prompt-neutron multiplicity NeuLAND can be used to measure the prompt-neutron multiplicity per fragment Describe the evolution of the shell effects as a function of the excitation energy How the additional excitation energy is shared between the FF ?

NUSTAR week SOFIA: Fission@R3B

• A. Chatillon

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

(p,2p) induced fission of polonium around N=126. D. M¨

uchner et al. Fission barrier: strong test of the models Fission barriers are known: ⇒ for few nuclides only ⇒ mostly close to the stability valley And for the exotic nuclei? ⇒ key data for the r-process cycling simulation ⇒ but no experimental data ⇒ rely on models ⇒ but strong divergence of the predictions New measurements are mandatory to qualify the models

Mamdouh et al., Nucl. Phys. A 679, 337 (2001) NUSTAR week SOFIA: Fission@R3B

• A. Chatillon

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Coulex-induced fission of neutron deficient pre-actinides. J. Taieb et al.

Yields and νtot from symmetric fission (Ac) down to asymmetric fission (Hg)

stable nuclei mass distributions charge distributions HEAVY ACTINIDES: asymmetric fission LIGHT ACTINIDES: asymmetric to symmetric fission

K.-H. Schmidt et al., NPA 665 (2000) 221

• A. Andreyev et al., PRL 105 (2010) 252502

NEUTRON DEFICIENT PRE-ACTINIDES: ?

70’s: role of the FF shell effects in asymmetric fission in heavy actinides 90’s: first experiment using inverse kinematics at relativistic energy: ⇒ transition from asymmetric to symmetric fission along the thorium ⇒ expected symmetric fission for lighter nuclei 2010: unexpected asymmetric fission in Hg 2020: characterization of the symmetric to asymmetric fission with SOFIA@R3B ⇒ deformation at scission of the symmetric and symmetric fission modes ⇒ underlying p- and n- shell effects of these fission modes ⇒ pairing effect in these systems having a high fission barrier

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

242Pu beam

Accurate yields and prompt-neutron multiplicity of Pu and Am nuclides

⇒ data beyond A=238 ⇒ important nuclides for the nuclear technology ⇒ especially for the fast-neutron Gen-IV reactor

Pu source: interest for part of the NUSTAR community

⇒ beams around 132Sn produced by fission with one order of magnitude higher than with U ⇒ a factor 10 in the statistics... ⇒ you should tell in case you could be interested by such a source

242Pu available at the Oakridge National Laboratory

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

FAIR + R3B is a unique facility for the fission studies Relativistic secondary beams:

⇒ high intensity 1 A.GeV 238U beam ⇒ production of a broad range of of actinides and pre-actinides ⇒ possibility to study the fission of nuclei unreachable in direct kinematics

R3B/SOFIA coupled to standard R3B

⇒ identification of both fission fragments in coincidence with νtot ⇒ fission observable as a function of E∗

Fission@R3B can:

⇒ probe the scission configuration ⇒ study the p- and n- shell effects ⇒ extract the fission barrier ⇒ probe the fission dynamics

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SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion

Thank you !

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Fission modes 2014 Setup Triple-MUSIC 2016

Fission in the heavy actinides (U) region proposed by Brosa

3 fission modes in the actinides region:

• 2 asymmetric modes: ST1 and ST2
• 1 symmetric mode: SL

each fission mode:

• proper path in the equipotentiel energy surface
• different structure effects
• different scission configurations

standard 1 (ST1)

• quasi-spherical heavy FF

⇒ AH ∼132, ZH ∼50, NH ∼ 82

• deformed light FF

standard 2 (ST2)

• deformed heavy FF

⇒ AH ∼140, ZH ∼54

• p shell in Q30-deformed

fragments

superlong (SL)

• less shell influence (LDM)
• increases with E∗
• very long path

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Fission modes 2014 Setup Triple-MUSIC 2016

Fission in the heavy actinides (U) region proposed by Brosa

3 fission modes in the actinides region:

• 2 asymmetric modes: ST1 and ST2
• 1 symmetric mode: SL

each fission mode:

• proper path in the equipotentiel energy surface
• different structure effects
• different scission configurations

standard 1 (ST1)

• quasi-spherical heavy FF

⇒ AH ∼132, ZH ∼50, NH ∼ 82

• deformed light FF
• short path: compact

HIGH TKE, LOW ν

standard 2 (ST2)

• deformed heavy FF

⇒ AH ∼140, ZH ∼54

• p shell in Q30-deformed

fragments INTERMEDIATE TKE

superlong (SL)

• less shell influence (LDM)
• increases with E∗
• very long path
• large elongation

LOW TKE, HIGH ν Yields + TKE or νtot: PROBE OF THE SCISSION CONFIGURATION

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Fission modes 2014 Setup Triple-MUSIC 2016

Neutron multiplicity and TKE: 235U case

Analysis by J.-F. MARTIN (PhD)

TKE vs (NFF,ZFF)

high TKE for ST1 mode ⇒ compact configuration low TKE for SL mode ⇒ large deformation

νtot vs (NFF,ZFF)

high νtot when TKE is low ⇒ deformation energy is converted into excitation energy in the fission fragments

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Fission modes 2014 Setup Triple-MUSIC 2016

Setup upstream ALADIN

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Fission modes 2014 Setup Triple-MUSIC 2016

Setup downstream ALADIN

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Fission modes 2014 Setup Triple-MUSIC 2016

List of the detectors (2014), resolution are given FWHM

3×MWPCs

MWPC0 MWPC1 MWPC2 beam FFs FFs dimension 200×200mm2 200×200mm2900×600mm2 x resolution 200µm 200µm 300µm y resolution 1 mm 1 mm 1 mm

Twin-MUSIC: energy loss and angle of both fission fragments

⇒ dimensions: (2×) 110×220×400 cm3 ⇒ resolutions: ∆Z∼0.2, ∆x∼60µm, ∆θ∼0.3mrad

Triple-MUSIC: energy loss and angle of the secondary beam

⇒ dimensions: (3×) 85×85×150 cm3 ⇒ resolutions: ∆Z∼0.2, ∆x∼40µm

Scintillators at S2

⇒ dimensions: 200×32×1 mm3 ⇒ resolution: ∆x∼3mm

Time-of-flight wall

⇒ dimensions: (28×) 660×32×5 mm3 ⇒ resolution: ∆y∼3mm, ∆ToF∼35 ps

Scintillators at Cave C

⇒ dimensions: 50×32×1.5 mm3 ⇒ resolution: ∆x∼1mm

Active target

⇒ dimensions: 10 cm diameter, 2 cm gap ⇒ fission vertex

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Fission modes 2014 Setup Triple-MUSIC 2016

Secondary beam identification: new Triple-MUSIC and MWPC

minimization of the material in the beam path

gazeous detector if possible if not, as thin as possible detectors (degrador at S2, plastic at S2 and cave C)

why a Triple-MUSIC ?

three independant energy losses measurement in one detector avoid mis-identification of secondary beam, due to the charge states

coupled with an absolute position measurement (MWPC)

stripper+field cage

TOP VIEW

section 1 section 2 section 3

field cage

K FG A

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Fission modes 2014 Setup Triple-MUSIC 2016

Secondary beam identification: new Triple-MUSIC and MWPC

stripper+field cage

TOP VIEW

section 1 section 2 section 3

field cage

K FG A

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Fission modes 2014 Setup Triple-MUSIC 2016

Results from 2016: Sn setting, 450 A MeV

peak / valley = 200

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Fission modes 2014 Setup Triple-MUSIC 2016

Results from 2016: Sn setting, 450 A MeV

peak / valley = 200 some charge state tail in between peaks

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Fission modes 2014 Setup Triple-MUSIC 2016

Results from 2016: Sn setting, 450 A MeV

peak / valley = 200 some charge state tail in between peaks ∆Z ∼ 0.23 charge unit (FWHM) for low rate

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Fission modes 2014 Setup Triple-MUSIC 2016

Results from 2016: Si setting

peak / valley = 1000 ∆Z = 0.19 charge unit (FWHM)

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Fission modes 2014 Setup Triple-MUSIC 2016

Results from 2016: C beam

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