The nTOF Collaboration www cern chn TOF nTOF

The n_TOF Collaboration, www. cern. ch/n. TOF n_TOF Experiment Report (2009/2011) Carlos GUERRERO (CERN) on behalf of the n_TOF Collaboration With several contributions, in particular from: E. Chiaveri (CEA/CERN), C. Lederer (U. Vienna), K. Fraval (CEA) and D. Tarrio (U. Santiago) 42 nd CERN INTC meeting (February 1, 2012) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Layout ① The n_TOF Collaboration Institutions ② n_TOF Facility Timeline ③ Facility improvements 2009 -2010 ④ n_TOF-Ph 2 experimental campaigns 2009 -2011 ⑤ Experimental Program in 2012 ⑥ Conclusions n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Collaboration institutions Members as of 2012: 33 Institutions (EU, USA, India) [Collaborations with Japan and Russia] 100 Scientists 16 Ph. D students Newcomers since 2009: Joint Research Center IRMM (Belgium) University of Zagreb (Croatia) University of Manchester (United Kingdom) University of York (United Kingdom) University of Frankfurt (Germany) PSI, Paul Scherrer Institute (Switzerland) University of Thessaloniki (Greece) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Feasibility CERN/LHC/9802+Add 2011 New Target construction Commissioning May 2009 2008 Commissioning TARC experiment May 1998 1996 EAR 2 design 1997 Concept by C. Rubbia CERN/ET/Int. Note 97 -19 Phase I Isotopes Capture: 25 Fission: 11 Papers: 21 Proc. : 51 Doc: 150 Problem Investigation Phase II 2009 Proposal submitted 2001 -2004 Aug 1998 1999 Construction started 2004 -2007 2010 1995 -1997 2000 n_TOF Facility Timeline Upgrades: Borated-H 2 O Second Line Class-A V. Vlachoudis n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Facility Improvements 2009 -2010 ① New Lead spallation target [2009] ② Improved cooling and ventilation systems [2009] → Heat dissipation optimized and corrosion risk controlled. ③ Separated moderation system: 10 B water as moderator [2010] → Reduction of the in-beam g-rays in a factor of 10. ④ Transformation of the EAR in Type-A laboratory [2010] → No need for certified sealing for radioactive samples. ⑤ Extended memory for flash-ADC digitizers in the [2010] → (n, g) measurements with C 6 D 6 down to thermal energies (0. 0253 me. V). n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Phase 2 (2009 -2011) Focus On Higher Quality And Accuracy Measurements (Combination Of Different Detectors) Capture (x 11) 54, 56, 57 Fe (C 6 D 6) 58, 60, 62 Ni, 63 Ni (C 6 D 6) – Measure angular distribution of FF. together with s(n, f) 235 U (TAC + MGAS) – Measure s(n, f) of very high activity samples 236 U (TAC & C 6 D 6) – Measure simultaneous capture and fission 238 U (TAC) – Extend our activities to (n, a) reactions [tests for (n, p) ongoing] – Measure complementary reactions (capture or fission) for isotopes measured in n_TOF-Ph 1 241 Am (TAC & C 6 D 6) Fission (x 6) 235, 238 U, 232 Th, 237 Np 240, 242 Pu Not measured (PPAC) (MGAS) (n, a) (x 2) 33 S (MGAS) 10 B (p. CVD-diamond) 232 Th 233 U 234 U 233 Th 234 Th 235 U 243 Cm 243 Am 240 Am 241 Am 242 Am 239 Pu 240 Pu 241 Pu 242 Pu 239 Np Capture Fission 242 Cm 236 Np 237 Np 238 Np 236 U 237 U 238 U 244 Cm Actinides at n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland) 245 Cm

n_TOF Experimental Campaigns 2009, 2011 and 2012 2009 Campaign (0. 7 x 1019 protons, Commissioning + 2 measurements) *Characterization of neutron fluence (water as moderator) *Characterization of the beam profile *Characterization of the Resolution Function The role of Fe and Ni for s-process nucleosynthesis: 56 Fe(n, g) and 62 Ni(n, g) 2010 Campaign (1. 2 x 1019 protons, Commissioning + 4 measurements) *Characterization of neutron fluence (water as moderator) *Characterization of the beam profile (after a new alignment of the overall beam optics) The role of Fe and Ni for s-process nucleosynthesis: 54 Fe(n, g) Neutron capture cross section measurements of 238 U, 241 Am and 243 Am at n_TOF: 241 Am Validation of simultaneous measurement of capture and fission reactions at n_TOF Angular distributions in the neutron-induced fission of actinides: 232 Th, 235, 238 U, 237 Np 2011 Campaign (1. 6 x 1019 protons, 10 measurements) The role of Fe and Ni for s-process nucleosynthesis: 57 Fe(n, g) and 58 Ni(n, g) The neutron capture cross section of the s process branch point isotope 63 Ni Measurement of the neutron capture cross-section of 236 U Measurement of the fission cross-section of 240 Pu and 242 Pu at CERN's n_TOF Facility Neutron capture cross section measurements of 238 U, 241 Am and 243 Am at n_TOF: 238 U Reference measurement of the high energy (n, α) cross section of 10 B with a CVD diamond detector Micro. Megas performance test for (n, a) measurements at n_TOF: 33 S(n, a) cross section Angular distributions in the neutron-induced fission of actinides: 232 Th, 235, 238 U, 237 Np n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Research fields of interest at n_TOF Cross Sections for Nuclear Technologies U cycle: 235 Un, g/f(TAC+MGAS), 237 Npn, f(PPAC), 238 Un, g(TAC), 241 Amn, g(C 6 D 6, TAC), 240, 242 Pun, f(MGAS) Thorium cycle: 232 Thn, f (PPAC), 236 Un, g (C 6 D 6, TAC) Cross Sections for Stellar Nucleosynthesis: The role of capture on stable Fe/Ni: 54, 56, 57 Fe, 58, 62 Ni (C 6 D 6) First branching points of the s-process: 63 Nin, g (C 6 D 6) The (n, a) reaction in the s-process branching point 59 Ni (s. CVD diamond) Neutron capture cross section of 25 Mg and its astrophysical implications (C 6 D 6) Basic Nuclear Physics Angular distribution of fission fragments from 232 Th, 235 U, 237 Np and 238 U (PPAC) Spin assignment of nuclear levels above Sn in 88 Sr (TAC) Test for measurements for INC model benchmarks: (n, *) reactions above 300 Me. V Nuclear medicine The 33 S(n, a) reaction for enhancing BNCT for cancer n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

In the weak s-process region the abundances of isotopes from Fe to Zr are highly affected by the knowledge of the cross section of every single isotopes: Conclusions can be drawn only when ALL cross sections are known! n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

63 Ni (unstable) represents first branching point in s-process reaction path: Highest uncertainty in 63, 65 Cu abundances comes from unknown 63 Ni(n, g) cross section Until 2011, measurements so far ONLY at thermal energies: • MACS are based on extrapolation of these cross sections from theoretical • MACS at 30 ke. V: KADo. Ni. S: 31± 6 mb Pred TENDL(2009): 68. 9 mb ictio ns Mengoni (th): 90. 8 mb The raw material is similar to the one measured at DANCE (LANL), but chemical purification (PSI@Switzerland) has been carried out in order to eliminate the 2% Cu impurities: now “just ” 62 Ni and 63 Ni (12%, 112 mg). n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Accurate g-ray energy calibrations at energies up to 10 Me. V (~Sn) Normalization at 4. 9 e. V tor. c a e r r a l nucle a t n e Ro. I. m i l r a e c i p s x y e h an op Yield via breeding in int!] in the Astr mple = nat ∙sra(n ching po : a S s on. T : i H g e r e G r u I t L b V a , t H g e n s ) s in the k fir HIG tent in 63 Ni(n, g) [ e c n 63 Ni inexis f a o n o s t s n e r e f ① asurem observation o e m t s r i ② F ental m i r e p x e ③ First 63 Ni-sample 62 Ni-sample n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

The sample (disk-shaped with 12. 2 mm diameter) consists on 32. 2 mg of 241 Am oxide embedded in a 305 mg Al 2 O 3 matrix and encapsulated in a 0. 5 mm thick aluminum canning. (3. 8 GBq) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Background subtracted // PHWF (efficiency) applied // Normalization to 197 Au performed bq) G 4 ~ ( e r p. ! r captu x o e f e l d r g o n i c _TOF re s covered in a s n : e l p e. V i ity sam M v i o t t c l a a h erm hig racy! TS: h u y t H r c 0 e. V. c e G 5 m I a v 1 L o r a d H d f e f n G v n o I o o o H : impr RR bey ements complete regi C R r A u d T s n a d e e t n to ex ①M t the C 6 D 6 a w a o h h l t i a e l w l i m t i t remen istics w t u a s t ② First a s e d m n bined tion a u l m o o s C e r d ③ dente e c e r p n ④ U Remains the comparison with previous data and evaluations n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

The criticality of current and fast future reactors must be known within 0. 3 -0. 5% for operation/safety. Sensitive mainly to the 235 U(n, g) below 2. 25 ke. V (RRR) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

The n_TOF Total Absorption Calorimeter The n_TOF Micro. Megas -4 p geometry (high tot. absorption effic. ) -40 Ba. F 2 crystals (segmentation) -Good energy resolution (back. discrimin. ) - Used extensively for (n, g) on actinides -Two gas regions: conversion & amplification - High gain and low noise - Possibility for several samples in parallel. - Used extensively for (n, f) and (n, a) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Ba. F 2 module Total – fission neu Background tro. Fission ns Capture dominated resonances High fission contribution MGA S wit 235 U sam h 3 ples Total - fission-backg. Fission MGAS signals n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

TOF _ n t a y nt of l e s u m o e e r n u s a mea imult s s u d n in o e r o e i u n t s a a a t c l i e l u b m n are n), Sim for pu : o i o d S i s e t T s t i a H f r p e o G d I c b N , ac ure an HIGHL Colla R t F E p O C a c T t _ a e n s TC. tim on he N t i I T t s ( r c y i . a b F l e a r d e t ① pprov fission rero e a r d ) e f n , u a n G ( e /. r ) 235 U(n, g ② C captu d e f c o u n d. o n i A -i stigat e v neutron hysical Journal n i e t omple n. P c a e a p r o o r f u l E roposa p w e n ③ A n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Angular distributions in the neutron-induced fission of actinides CERN-INTC-2006 -016 INTC-P-209 Nuclear Technology and Basic Nuclear Physics motivations Fission fragments are not emitted isotropically with respect to the beam direction, but with an angular distribution defined by the momentum conservation between initial and final states. In particular, large variations are exhibited when a new channel is open, since only a level above the barrier is available with a well-defined angular momentum. n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Angular distributions in the neutron-induced fission of actinides CERN-INTC-2006 -016 INTC-P-209 Starts from succesful n_TOF-Ph 1 meas. with PPAC (237 Np & 209 Bi up t 1 Ge. V among others) Limited ang. acceptance Signficant corrections due to uncertain ang. distributions n_TOF Ph-2 set-up: • Samples tilted 45 o wrt. neutron beam • 10 PPAC detectors with 9 targets in between (235 U, 238 U, 237 Np, 6 x 232 Th) • Segmented cathodes to study the ang. distributions of FF. , in addition to sn, f(En). n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Angular distributions in the neutron-induced fission of actinides CERN-INTC-2006 -016 INTC-P-209 232 Th f FF. o els). n d o i o t u m b i r r o t erest f lar Dis t u n g i INTC. n g A @ n f o y r o a t d s F 6 ( : o 23 U t e. V HTS n_TO HIGHLIG easurement at itr. Above 100 M n on 234 U and m. D tigatio s e v ① First er data on Ang n i e ontinu ev c t s o r i t F t n e ② perim x e w e n ③ A le! b a l i a o av s l a 7 p 3 2 N d n a 8 3 235, 2 U n o Data n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Experimental Program 2012 (8 -11 measurements) n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)

Conclusions Neutron-induced reactions are measured at n_TOF –Phase 2 since 2009: Nuclear Technology // Stellar Nucleosynthesis // Basic Nuclear Physics // Nuclear Medicine q. Several detection systems available q 19 isotopes studied 2009 -2011 q. Sim. (n, g)/(n, f) ongoing since 2010 q. FF. Ang. Dist. ongoing since 2010 q(n, a) reactions ongoing since 2011 q 16 Ph. D students at present n_TOF Experiment Report @ INTC meeting (Feb. 1 st 2012 Geneva, Switzerland)