EXFOR 23675
last update: 2025-12-18
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0. OVERALL DESCRIPTION (23675.001)
last update: 2025-12-18
Title

New insights on fission of 235U induced by high energy neutrons from a new measurement at nTOF

Author
A.Manna, E.Pirovano, P.Console Camprini, L.Cosentino, M.Dietz, Q.Ducasse, P.Finocchiaro, C.Le Naour, D.Mancusi, C.Massimi, A.Mengoni, R.Nolte, D.Radeck, L.Tassan-Got, N.Terranova, G.Vannini, A.Ventura, O.Aberle, V.Alcayne, S.Amaducci, J.Andrzejewski, L.Audouin, V.Babiano-Suarez, M.Bacak, M.Barbagallo, S.Bennett, E.Berthoumieux, J.Billowes, D.Bosnar, A.Brown, M.Busso, M.Caamano, L.Caballero-Ontanaya, F.Calvino, M.Calviani, D.Cano-Ott, A.Casanovas, D.M.Castelluccio, F.Cerutti, E.Chiaveri, N.Colonna, G.Cortes, M.A.Cortes-Giraldo, S.Cristallo, L.A.Damone, P.J.Davies, M.Diakaki, C.Domingo-Pardo, R.Dressler, E.Dupont, I.Duran, Z.Eleme, B.Fernandez-Dominguez, A.Ferrari, V.Furman, K.Goebel, R.Garg, A.Gawlik-Ramiega, S.Gilardoni, I.F.Goncalves, E.Gonzalez-Romero, C.Guerrero, F.Gunsing, H.Harada, S.Heinitz, J.Heyse, D.G.Jenkins, A.Junghans, F.Kaeppeler, Y.Kadi, A.Kimura, I.Knapova, M.Kokkoris, Y.Kopatch, M.Krticka, D.Kurtulgil, I.Ladarescu, C.Lederer-Woods, H.Leeb, J.Lerendegui-Marco, S.J.Lonsdale, D.Macina, T.Martinez, A.Masi, P.Mastinu, M.Mastromarco, E.A.Maugeri, A.Mazzone, E.Mendoza, V.Michalopoulou, P.M.Milazzo, F.Mingrone, J.Moreno-Soto, A.Musumarra, A.Negret, F.Ogallar, A.Oprea, N.Patronis, A.Pavlik, J.Perkowski, C.Petrone, L.Piersanti, I.Porras, J.Praena, J.M.Quesada, D.Ramos-Doval, T.Rauscher, R.Reifarth, D.Rochman, C.Rubbia, M.Sabate-Gilarte, A.Saxena, P.Schillebeeckx, D.Schumann, A.Sekhar, A.G.Smith, N.V.Sosnin, P.Sprung, A.Stamatopoulos, G.Tagliente, J.L.Tain, A.Tarifeno-Saldivia, Th.Thomas, P.Torres-Sanchez, A.Tsinganis, J.Ulrich, S.Urlass, S.Valenta, V.Variale, P.Vaz, D.Vescovi, V.Vlachoudis, R.Vlastou, A.Wallner, P.J.Woods, T.Wright, P.Zugec
Institute
Universita di Bologna + INFN Bologna
Physikalisch-Technische Bundesanstalt, Braunschweig
ENEA Centro Ricerche Energia di Bologna
INFN Laboratori Nazionali del Sud, Catania
Univ. of Edinburgh, Scotland
Universite de Paris
CEA/Saclay
European Org. for Nuclear Research (CERN), Geneva
National Technical Univ. of Athens, Athens
ENEA Centro Ricerche Frascati, Frascati
Centro para Invest. Energ., Medio. y Tecnol. (CIEMAT)
Universita degli Studi di Catania + INFN Catania
Univ. of Lodz, Lodz
Universidad de Valencia, Valencia
Atominstitut der Technischen Universitaet Wien,Vienna
Universita degli Studi di Bari + INFN Bari
Univ. of Manchester, England
Univ. of Zagreb, Zagreb
Univ. of York, York
Universita degli Studi di Perugia + INFN Perugia
Universidad de Santiago de Compostela
Universitat Politecnica de Catalunya, Barcelona
Universidad de Sevilla, Seville
Osservatorio Astronomico di Collurania, Teramo
Paul Scherrer Institut, Villigen
Univ. of Ioannina, Ioannina
J.W.Goethe Univ., Frankfurt/Main
Instituto Tecnologico e Nuclear, Sacavem
Japan Atomic Energy Agency (JAEA)
EC Joint Research Centre (EC-JRC), Geel
Helmholtz-Zentrum Dresden-Rossendorf, Dresden
Karlsruhe Institute of Technology (KIT)
Charles Univ., Prague
INFN Laboratori Nazionali di Legnaro, Legnaro, Padova
Universita degli Studi di Trieste + INFN Trieste
Horia Hulubei National Institute (IFIN-HH), Magurele
Universidad de Granada, Granada
Universitaet Wien, Vienna
University of Basel, Basel
Univ. of Hertfordshire, Hatfield, Hertfordshire
Bhabha Atomic Research Centre (BARC), Trombay, Mumbai
Australian National University, Canberra
Italy

Consiglio Nazionale delle Ricerche, Bari

Reference
Phys.Lett.B 860 (2025) 139213
Related reference
E.Pirovano et al., J.Instrumentation 18 (2023) P11011
Reference to experimental instruments

Details on PPFC+RPT measurements

A.Manna et al., J.Instrumentation 18 (2023) P04024
Reference to experimental instruments

Details on PPAC+RPT measurements

Facility
Synchro cyclotron of European Org. for Nuclear Research (CERN), Geneva

CERN nTOF facility. Protons (7 to 8.5E+12 protons/pulse, pulse width of 7 nsec) were accelerated to 20 GeV/c with repetition rate of 0.8 Hz at maximum.

Incident particle source
Spallation

1E+6 neutrons/pulse were produced in a Pb spallation target coupled to water moderators.

The diameter of the neutron beam at sample position is 2 cm.

Incident spectrum
Heading Explanation
EN-RSL-HW
Half of bin width
Sample

Two 235U (92.699(5)%) and eight 235U (99.933(14)%) enriched samples mounted in PPFC and PPAC.

Two polyethylene sheets for n-p scattering measurement.

Method
Time-of-flight

Flight path of 185 m

Particle identification by 'E/Delta E' measurement

for separation of (n,p) events form (n,d), (n,t) and (n,a) events

Corrections

Corrected for 12C(n,p) events by an additional measurement using graphite samples

Standard
1H(n,el)1H angular distribution of particle specified (particle considered: protons)

n-p scattering cross section in the centre-of-mass system for proton at 20 and 25 deg in the laboratory system in LA150 library (VL40 wave analysis energy dependent phase-shift solution of Arndt above 26 MeV) interpolated by MCNP 

+----------------------------------------------------+
  Tlab (MeV)             sigma,cm (mb/sr)
              theta,lab=20.0 deg   theta,lab=25.0 deg
------------------------------------------------------
   20.0           151.1773             143.0919
   25.0           119.6774             112.3854
   30.0            98.2831              91.4940
   35.0            82.9424              76.5152
   40.0            71.5839              65.3763
   45.0            62.8253              56.8485
   50.0            55.9827              50.1418
   55.0            50.5020              44.8111
   60.0            46.0731              40.4603
   65.0            42.4019              36.9134
   70.0            39.3703              33.9688
   75.0            36.8074              31.5020
   80.0            34.6420              29.4214
   85.0            32.7947              27.6482
   90.0            31.2097              26.1335
   95.0            29.8372              24.8245
  100.0            28.6440              23.6949
  110.0            26.6841              21.8386
  120.0            25.1544              20.3961
  130.0            23.9333              19.2479
  140.0            22.9368              18.3085
  150.0            22.1063              17.5243
  160.0            21.3968              16.8537
  170.0            20.7786              16.2632
  180.0            20.2285              15.7369
  190.0            19.7309              15.2568
  200.0            19.2700              14.8089
  210.0            18.8391              14.3918
  220.0            18.4333              13.9956
  230.0            18.0407              13.6170
  240.0            17.6676              13.2522
  250.0            17.3040              12.8977
  260.0            16.9518              12.5551
  270.0            16.6048              12.2189
  280.0            16.2674              11.8915
  290.0            15.9355              11.5723
  300.0            15.6067              11.2609
  310.0            15.2859              10.9539
  320.0            14.9683              10.6510
  330.0            14.6563              10.3578
  340.0            14.3475              10.0676
  350.0            14.0429               9.7806
+----------------------------------------------------+
Standard reference
R.A.Arndt, Report NEANDC-305p. 39, OECD Nuclear Energy Agency (NEA), 1991
Status
Approved by author

Proofread by Elisa Pirovano and Alice Manna (2025-12-23)

History
Date Work Remark
2025-12-18 Data received at the data center
Data received from Elisa Pirovano
2025-12-18 Compiled at the data center
On+ED
1. DATA TABLE 23675.002.1
last update: 2025-12-18
Quantity given
235U(n,f) cross section

PPFC+3S-RPT dataset

Detector

.PPFC+3S-RPT dataset

Fission chamber

Parallel Plate Fission Chamber (PPFC) containing eight 235U samples (42 mm diam., 264 to 338 ug/cm2 determined by alpha counting), for measurement up to 145 MeV.

Counter telescope, Scintillation detector, Scintillation detector

Recoil proton telescope Triple-stage RPT (3S-RPT) at 25 deg

Comment

* By Alice Manna and Elisa Pirovano (2025-12-04):

.PPFC+3S-RPT dataset

The cross section obtained with PPFC and 3S-RPT. In this detection system, the recoil proton telescope was at a proton emission angle theta,p of 25 deg.

In this case, the measured fission cross section is proportional to the differential proton emission cross section dsigma/dOmega,p at theta,p) in the laboratory frame.

Therefore, it is possible to re-normalized it in case of change of the neutron-proton elastic scattering cross section at the corresponding neutron scattering angle.

Error analysis
Heading Lower limit (%) Upper limit (%) Correlation Remark
ERR-T
Total uncertainty
ERR-S
Statistical uncertainty
ERR-SYS
Total systematic uncertainty
ERR-2
Systematic uncertainty correlated between PPFC and PPAC datasets:
  • Isotopic composition of the PE samples (H/C ratio) 1.5%
  • Areal density of the PE samples, correlated component, depending on the sample used for each energy interval 0.2%-0.8%
  • Areal density of the C samples, correlated component, depending on the sample 0.3%-1.1%
  • Beam profile 0.5%
  • Beam transmission through PPFC, PPAC, energy dependent 0.2%-0.5%
ERR-1
PPFC/3S-RPT systematic uncertainty uncorrelated with PPAC/MSR-RPTs systematic uncertainty:
  • Isotopic composition of the uranium targets of the PPFC 0.0014%
  • Mass of the uranium targets of the PPFC 0.2%
  • Correction on the effective areal density of the uranium targets of the PPFC 0.6%
  • Areal density of the PE samples, uncorrelated component for the 3S-RPT, depending on the RPT configuration used for each energy interval 0%-0.4%
  • Areal density of the C samples, uncorrelated component for the 3S-RPT, depending on the RPT configuration 0%-0.9%
  • PPFC detection efficiency: zero-bias efficiency, weak energy dependence 1.0%-1.2%
  • PPFC detection efficiency: extrapolation below threshold 2.9%
  • PPFC dead-time correction, energy dependent 0.04%-0.2%
  • 3S-RPT angle 0.1%-0.6%
  • 3S-RPT distance 0.8%
  • 3S-RPT effective solid angle (area of the dEz detector) 0.4%-0.7%
  • 3S-RPT dead-time correction 0.6%-0.9%
  • 3S-RPT: event selection in the dE-E 0.2%-0.4%
  • 3S-RPT: efficiency calculation fit 2.4%
Status
Data presented by authors (Ref. A.Manna et al., Phys.Lett.B 860 (2025) 139213)
Data table (only first and last 5 data points are shown) 
------------------------------------------------------------------------------------------------
EN          EN-RSL-HW   DATA       1ERR-T      1ERR-S      1ERR-SYS    1ERR-1      1ERR-2       
MEV         MEV         MB          MB          MB          MB          PER-CENT    PER-CENT    
------------------------------------------------------------------------------------------------
  10.63       0.63                                                                              
  11.95       0.70                                                                              
  13.44       0.79                                                                              
  15.12       0.89                                                                              
  17.01       1.00                                                                              
 ..........  ..........  ..........  ..........  ..........  ..........  ..........  .......... 
 295.31      12.72                                                                              
 321.88      13.86                                                                              
 350.85      15.11                                                                              
 384.26      18.30                                                                              
 422.69      20.13                                                                              
------------------------------------------------------------------------------------------------
2. DATA TABLE 23675.002.2
last update: 2025-12-18
Quantity given
235U(n,f) cross section

PPAC+MSRPT dataset

Detector

.PPAC+MSRPT dataset

Parallel plate avalanche counter

Parallel Plate Avalanche Counter containing two 235U samples (80 mm diam., 263 ug/cm2 and 282 ug/cm2)

Counter telescope, Scintillation detector, Scintillation detector

Recoil proton telescope

  • Multi-stage RPT (MS-RPTL) at 25 deg
  • Multi-stage RPT (MS-RPTH) at 20 deg
Comment

* By Alice Manna and Elisa Pirovano (2025-12-04):

.PPAC+MSRPT dataset

The cross section obtained with PPAC and MS-RPTL and MS-RPTH. In this detection system two recoil proton telescopes were used, positioned at 25 deg and 20 deg, respectively.

In this case the normalization is not straightforward, therefore we are proposing a method (outlined in ????) for the re-normalization.

Miscellaneous columns
Heading Explanation
MISC
[w(20 deg)*phi(20 deg)]/[w(25 deg)*phi(25 deg)]
Error analysis
Heading Lower limit (%) Upper limit (%) Correlation Remark
ERR-T
Total uncertainty
ERR-S
Statistical uncertainty
ERR-SYS
Total systematic uncertainty
ERR-2
Systematic uncertainty correlated between PPFC and PPAC datasets:
  • Isotopic composition of the PE samples (H/C ratio) 1.5%
  • Areal density of the PE samples, correlated component, depending on the sample used for each energy interval 0.2%-0.8%
  • Areal density of the C samples, correlated component, depending on the sample 0.3%-1.1%
  • Beam profile 0.5%
  • Beam transmission through PPFC, PPAC, energy dependent 0.2%-0.5%
ERR-1
PPAC/MS-RPTs systematic uncertainty uncorrelated with PPFC/3S-RPT systematic uncertainty:
  • Mass of the uranium samples of the PPAC 1.0%
  • Areal density of the PE samples, uncorrelated component for the MS-RPTs, depending on the sample used for each energy interval 0.0%-0.3%
  • Areal density of the C samples, uncorrelated component for the MS-RPTs, depending on the sample 0%-0.5%
  • PPAC: reconstruction of the fission fragments trajectories 0.4%
  • PPAC efficiency calculation fit, energy dependent 2.0%-2.7%
  • PPAC anisotropy correction, energy dependent 0%-1.2%
  • MS-RPT position, depending on the RPT configuration 0.9%-1.2%
  • MS-RPT signal reconstruction, depending on the RPT detectors included in the analysis of each energy interval 0.5%-1.8%
  • MS-RPT: events selection in the dE-E matrix, depending on the RPT detectors included in the analysis 2.0%-5.0%
  • MS-RPT dead-time correction, depending on the RPT detectors included in the analysis 1.0%-2.0%
Status
Data presented by authors (Ref. A.Manna et al., Phys.Lett.B 860 (2025) 139213)
Data table (only first and last 5 data points are shown) 
------------------------------------------------------------------------------------------------------------
EN          EN-RSL-HW   DATA       2ERR-T      2ERR-S      2ERR-SYS    2ERR-1      2ERR-2       MISC       2
MEV         MEV         MB          MB          MB          MB          PER-CENT    PER-CENT    NO-DIM      
------------------------------------------------------------------------------------------------------------
  10.63       0.63       1795.       147.        88.         117.        6.5                      0.000     
  11.95       0.70       1768.       137.        73.         116.        6.5                      0.000     
  13.44       0.79       1887.       142.        71.         123.        6.5                      0.000     
  15.12       0.89       2040.       152.        73.         133.        6.5                      0.000     
  17.01       1.00       2094.       153.        69.         137.        6.5                      0.000     
 ..........  ..........  ..........  ..........  ..........  ..........  ..........  ..........  .......... 
 295.31      12.72       1579.        84.        53.          65.        4.1                      2.162     
 321.88      13.86       1378.        75.        48.          57.        4.2                      1.886     
 350.85      15.11       1501.        83.        54.          63.        4.2                      2.069     
 384.26      18.30       1620.        90.        59.          68.        4.2                      1.941     
 422.69      20.13       1481.        84.        55.          63.        4.2                      2.074     
------------------------------------------------------------------------------------------------------------
3. DATA TABLE 23675.003
last update: 2025-12-18
Quantity given
235U(n,f) cross section, Average
Analysis

Weighted average of PPFC/3SRPT and PPAC/MSRPT datasets

Miscellaneous columns
Weights used to calculated the weighted mean
Heading Explanation
MISC1
w(PPFC/3S-RPT)
MISC2
w(PPAC/MS-RPTL)
Error analysis
Heading Lower limit (%) Upper limit (%) Correlation Remark
DATA-ERR
The uncertainty results from the procedure to calculate the weighted average.
Comment

* By Alice Manna and Elisa Pirovano (2025-12-04):

The final cross section obtained as weighted average of the two independent results (in which we have a contribution from both the neutron-proton elastic scattering differential cross section).

This data set contains the weights used to calculate the weighted mean, which makes it possible to re-calculate the weighted mean of the re-normalized fission cross sections measured with the two experimental configurations PPFC/3S-RPT and PPAC/MS-RPTL(H).

As discussed in E.Pirovano et al. "Absolute cross section for neutron-induced fission of 235U in the energy range from 10 MeV to 400 MeV" (to be published in Phys.Rev.C and arXiv), these two data sets are partially correlated, as the same polyethylene samples and beam intensity monitors were employed.

However, a small re-normalization of the differential neutron-proton scattering cross section will not effect the stated relative uncertainty of the final fission cross section.

Status
Data presented by authors (Ref. A.Manna et al., Phys.Lett.B 860 (2025) 139213)
Dependent data (See EXFOR 23675.002)

Datasets from PPFC/3SRPT and PPAC/MSRPT

Data table (only first and last 5 data points are shown) 
------------------------------------------------------------------------
EN          EN-RSL-HW   DATA        DATA-ERR    MISC1       MISC2       
MEV         MEV         MB          MB          NO-DIM      NO-DIM      
------------------------------------------------------------------------
  10.63       0.63       1795.       147.        0.          1.         
  11.95       0.70       1768.       137.        0.          1.         
  13.44       0.79       1887.       142.        0.          1.         
  15.12       0.89       2040.       152.        0.          1.         
  17.01       1.00       2094.       153.        0.          1.         
 ..........  ..........  ..........  ..........  ..........  .......... 
 295.31      12.72       1579.        84.        0.          1.         
 321.88      13.86       1378.        75.        0.          1.         
 350.85      15.11       1501.        83.        0.          1.         
 384.26      18.30       1620.        90.        0.          1.         
 422.69      20.13       1481.        84.        0.          1.         
------------------------------------------------------------------------
4. DATA TABLE 23675.004
last update: 2025-12-18
Quantity given
235U(n,f) cross section, Average (data type: derived data)
Analysis

Averaged data processed by smoothing filter.

The smoothed data starts from 149 MeV, below this energy the averaged cross section is reported.

Error analysis
Heading Lower limit (%) Upper limit (%) Correlation Remark
DATA-ERR
The uncertainty on the smoothed data results from the fitting procedure.
Status
Data presented by authors (Ref. A.Manna et al., Phys.Lett.B 860 (2025) 139213)

U5vsnp-smo

Dependent data (See EXFOR 23675.003)

Averaged cross section

Data table (only first and last 5 data points are shown) 
------------------------------------------------
EN          EN-RSL-HW   DATA        DATA-ERR    
MEV         MEV         MB          MB          
------------------------------------------------
  10.63       0.63       1795.       147.       
  11.95       0.70       1768.       137.       
  13.44       0.79       1887.       142.       
  15.12       0.89       2040.       152.       
  17.01       1.00       2094.       153.       
 ..........  ..........  ..........  .......... 
 295.31      12.72       1475.        29.       
 321.88      13.86       1480.        31.       
 350.85      15.11       1485.        32.       
 384.26      18.30       1489.        37.       
 422.69      20.13       1490.        55.       
------------------------------------------------