Double Chooz Near Detector Guillaume MENTION CEA Saclay

Double Chooz Near Detector Guillaume MENTION CEA Saclay, DAPNIA/SPP http: //doublechooz. in 2 p 3. fr/ Workshop AAP 2007 Friday, December 14 th, 2007

Double Chooz detector capabilities - Double Chooz experiment - The site - The 2 identical detectors - The reactors: powerful anti-neutrino sources - Expected performance - Detection of reactor anti-neutrinos: e+ and neutron - Anti-neutrino spectrum measurement (Far and Near detectors) - Thermal power measurement - Burn-up detection -Conclusions

Chooz power plant map Type # Cores Th. Power Operating since Load Factor PWR (N 4) 2 8. 5 GWth 1996/1997 78% Near site: D~380 m, overburden 120 mwe Far site: D~1. 05 km, overburden 300 mwe

The experiment site νν ν 380 m ν ν ν 1051 m

Double Chooz: 2 phases Timeline 2004 Site 2005 Proposal 2006 Design 2007 2008 Construction Far 2009 2010 2011 2012 Data Taking (Phase I) Cstr. Near Data Taking (Phase II) Double Chooz phase 1: far detector only may help to reach a higher precision on anti- e spectrum… Double Chooz phase 2: higher precision on anti- e spectrum ~ 2 105 events in 3 years

Reactors are abundant antineutrino sources 235 U 239 Pu Energy released per fission 201. 7 Me. V 210. 0 Me. V Average energy of e 2. 94 Me. V 2. 84 Me. V # e per fission > 1. 8 Me. V 1. 92 1. 45 239 Pu 235 U Fission percentages More than 1021 fissions/second 235 U 239 Pu 238 U Days 241 Pu

νe Detection technique 50 years of Physics ― νe identification: using coïncidences (allows strongly reducing backgrounds) (1) 0, 5 < Eprompt < 10 Me. V (3) 1 μs < Δt < 100 μs +1 Me Ee+ V Δt < 100 μs e+ n t Σ ≃ 8 Me. V (2) 6 < Edelayed < 10 Me. V

Detector structure Double Chooz: 2 identical detectors Calibration Glove-Box Outer Veto: plastic scintillator panels -Target: 10. 3 m 3 liquid scintillator doped with 0. 1% of Gd γ -Catcher: 4 Liquid Volumes 22. 6 m 3 liquid scintillator Buffer: 114 m 3 mineral oil with ~400 PMTs Inner Veto: 90 m 3 liquid scintillator with 80 PMTs Far detecto r Shielding: 15 cm steel

Backgrounds fast neutrons (CHOOZ data) ~ 8 Me. V μ → (9 Li, 8 He) → β-n γ t ~ ~ ~ ~ 9 ~ + u ne ~~ ~ ~ ~ e lik n tro en v e ~ ~ PM + rocks Accidentals Gd ~ Correlated proton recoils

Far detector capabilities Far site: phase I of Double Chooz Anti-neutrino spectrum measurement over 1. 5 years. (~ 22 000 anti-neutrinos): – – • • Require the knowledge of the average power over 1. 5 years Require the knowledge of the average fuel composition over 1. 5 years Would allow to measure the antineutrino rate at a statistical precision of 0. 7% (in case of no systematics) But also the shape of the spectrum, with a statistical precision of 2 to 3% per energy bin (with 8 bins between 1. 5 and 5. 5 Me. V). • Systematical uncertainties reduce this potential which is limited by the knowledge on the detector normalization (~ 2%) and on the reactor powers (~ 2%). • Backgrounds also lead to some systematical subtraction error around 1% per energy bin • The measured spectrum will include the oscillation effect. # anti- e in 1. 5 years • • - stat”+” syst Evis in Me. V

Map of the near site (Preliminary, still under study) • Distance to reactor cores: 456 m & 340 m 385 m (1 R. with 2 Pth) Near site location 4 160 m m m 56 34 0 Chooz NPP, mass map • Neutrino fluxes: w/o eff. 496 anti- e/day 2. 5 105 events in 3 years (all eff. included) • Depth: 120 m. w. e. (m flux: ~ 3 -4 m/m-2 s-1) Access tunnel

Thermal power measurement with the near detector • Thermal power is measured at ~2% (? ) by the nuclear power companies • Current measurement at reactor 3% but possibility of improvement • What can only neutrino do: • Independent method looking directly at the nuclear core, from outside • Cross calibration of different power plants from different sites ~ 10 000 events/month @ Double Chooz Near measurement Fig: Chooz cooling tubes With Double Chooz Near Average power measurement of both reactors: 5 -6% over 3 weeks = Assuming no knowledge on reactor (neither power nor fuel composition) Huber & Schwetz hep-ph/0407026 1 error on thermal power

235 U 239 Pu 238 U 241 Pu # anti- e in 10 days Fission percentages Following up the burn-up Days Evis in Me. V Detector efficiency included. Average spectra (analytical estimations), no statistical fluctuations here Question: How far can we see two different burn-up? Try to answer with non-parametric statistical test: Kolmogorov-Smirnov

Two extreme burn-up in 3 weeks (identical reactors) - 9980 events - 9370 events 239 Pu 238 U 241 Pu Days # anti- e in 3 weeks Fission percentages 235 U e r P i lim y r a n Evis in Me. V 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0. 66 235 U=0. 47 239 Pu=0. 24 239 Pu=0. 37 238 U=0. 08 241 Pu=0. 02 238 U=0. 08 241 Pu=0. 08 Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0: the two “burn-up” induce identical anti- e spectra • Shape only: PKS = 0. 81 (Max Distance = 0. 0093) Shapes are very close!!! • Rate and shape: PKS = 1. 3 x 10 -4 Rates are very different (~7% diff. on # of anti- e)

Two extreme Burn-up in 10 days (identical reactors) OR 16 days with R 1 ON R 2 OFF OR 29 days with R 1 OFF R 2 ON - 4750 events - 4460 events 239 Pu 238 U 241 Pu Days # anti- e in 10 days Fission percentages 235 U e r P i lim y r a n Evis in Me. V 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0. 66 235 U=0. 47 239 Pu=0. 24 239 Pu=0. 37 238 U=0. 08 241 Pu=0. 02 238 U=0. 08 241 Pu=0. 08 Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0: the two “burn-up” induce identical anti- e spectra • Shape only: PKS = 0. 99 (Max Distance = 0. 0093) Shapes look identical!!! • Rate and shape: PKS = 1. 8 x 10 -2 Rates are different (~7% diff. on # of anti- e)

Two closer burn-up in 3 weeks (identical reactors) - 9980 events - 9600 events 239 Pu 238 U 241 Pu Days # anti- e in 3 weeks Fission percentages 235 U e r P i lim y r a n Evis in Me. V 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0. 66 235 U=0. 54 239 Pu=0. 24 239 Pu=0. 32 238 U=0. 08 241 Pu=0. 06 Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0: the two “burn-up” induce identical anti- e spectra • Shape only: PKS = 0. 997 (Max Distance = 0. 006) Shapes look identical!!! • Rate and shape: PKS = 4. 2 10 -2 Rates are different (~4 % diff. on # of anti- e)

Two still closer burn-up in 3 weeks (identical reactors) - 9980 events - 9800 events 239 Pu 238 U 241 Pu Days # anti- e in 3 weeks Fission percentages 235 U e r P i lim y r a n Evis in Me. V 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0. 66 235 U=0. 61 239 Pu=0. 24 239 Pu=0. 28 238 U=0. 08 241 Pu=0. 02 238 U=0. 08 241 Pu=0. 03 Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0: the two “burn-up” induce identical anti- e spectra • Shape only: PKS = 1. 00 (Max Distance = 0. 002) Looks identical!!! • Rate and shape: PKS = 0. 55 Rates are too close, spectra match (~2 % diff. on # of anti- e)

Conclusion & Outlook - Neutrinos could “take a picture” of the nuclear cores Thermal power measurement & non proliferation applications - Thermal power measurement will rely on the absolute normalization (but time-relative measurement of interest for burn-up, cross calibration) - Non proliferation applications will rely on time-relative measurements (try to detect an ‘abnormal’ burn-up) - Double Chooz Near detector will provide an unrivalled anti- e spectrum measurement. These data will be an incredibly rich source of information in order to look for power, burn-up correlations with anti- e spectra as a first step toward isotopic core composition. - However more precise determination of reactor power and some hints of isotopic composition might be obtained only with a closer detector to a single reactor.

Thank you for your attention! It’s time for lunch now!

Systematics Chooz Reactorinduced Detector induced Analysis Double Chooz (relative) flux and 1. 9 % <0. 1 % Reactor power 0. 7 % <0. 1 % Energy per fission 0. 6 % <0. 1 % Solid angle 0. 3 % <0. 1 % Distance measured @ 10 cm + monitor core barycenter Target Mass 0. 3 % 0. 2 % Same weight sensor for both det. Density 0. 3 % <0. 1 % Accurate T control (near/far) H/C ratio & Gd concentration 1. 2 % <0. 2% Same scintillator batch + Stability Spatial effects 1. 0 % <0. 1 % ‘’identical’’ Target geometry & LS Live time few % 0. 25 % Measured with several methods From 7 to 3 cuts 1. 5 % 0. 2 - 0. 3 % (see next slide) 2. 7 % < 0. 6 % (Total ~0. 45% without contingency …. ) Total Two ‘’identical’’ detectors, Low bkg