Double Chooz Near Detector

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Transcript Double Chooz Near Detector

Double Chooz Near Detector

Guillaume MENTION CEA Saclay, DAPNIA/SPP Workshop AAP 2007 Friday, December 14 th , 2007

http://doublechooz.in2p3.fr/

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 (N4) 2 8.5 GW th 1996/1997 78%

Near site: D~380 m, overburden 120 mwe Far site: D~1.05 km, overburden 300 mwe

The experiment site

380 m

ν ν ν ν ν ν ν ν

1051 m

Double Chooz: 2 phases

Timeline

2004

Site

2005

Proposal

2006

Design

2007 2008

Construction Far

2009 2010 2011

Data Taking (Phase I) Cstr. Near

2012

Data Taking (Phase II)

Double Chooz phase 1: far detector only  precision on anti n e spectrum… may help to reach a higher Double Chooz phase 2: higher precision on anti ~ 2 10 5 n e spectrum events in 3 years

Reactors are abundant antineutrino sources

Energy released per fission Average energy of n e 235 U 201.7 MeV 2.94 MeV 239 Pu 210.0 MeV 2.84 MeV # n e per fission > 1.8 MeV 1.92

1.45

More than 10 21 fissions/second 239 Pu 235 U

235 U 239 Pu 238 U 241 Pu

Days

ν e

Detection technique

50 years of Physics

ν e identification: using coïncidences (allows strongly reducing backgrounds)

(1) 0,5 <

E prompt

< 10 MeV E e+ (3) 1 μs <

Δt

< 100 μs

Δt < 100 μs

e + n t

Σ

≃

8 MeV

(2) 6 <

E delayed

< 10 MeV

Detector structure

Double Chooz: 2 identical detectors Calibration Glove-Box 4 Liquid Volumes

Outer Veto:

plastic scintillator panels n

-Target

: 10.3 m 3 liquid scintillator doped with 0.1% of Gd 

-Catcher

: 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

Shielding

: 15 cm steel

Backgrounds

fast neutrons proton recoils  ~ 8 MeV

μ → ( 9 Li, 8 He) → β n

PM + rocks γ

(CHOOZ data)

~ ~

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 MeV).

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.

- s stat - s stat ”+” s syst E vis in MeV

Map of the near site

(Preliminary, still under study)

• Distance to reactor cores: 456 m & 340 m  385 m • Neutrino fluxes: w/o eff. 496 anti n e /day  2.5 10 5 events in 3 years (all eff. included) • Depth: 120 m.w.e. ( m flux: ~ 3-4 m /m -2 s -1 ) (1 R. with 2P th ) Near site location Access tunnel 160 m

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

error on thermal power measurement

~ 10 000 events/month @ Double Chooz Near 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)

Following up the burn-up

235 U 239 Pu 238 U 241 Pu Days Detector efficiency included.

E vis in MeV 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)

235 U 239 Pu - 9980 events - 9370 events 238 U 241 Pu 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0.66

235 U=0.47

Days 239 Pu=0.24

239 Pu=0.37

238 U=0.08

E vis in MeV 241 Pu=0.02

241 Pu=0.08

Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0 : the two “burn-up” induce identical anti n e spectra • Shape only: P KS = 0.81 (Max Distance = 0.0093)  Shapes are very close!!!

• Rate and shape: P KS = 1.3 x 10 -4  Rates are very different (~7% diff. on # of anti n e )

235 U 239 Pu

Two extreme Burn-up in 10 days

(identical reactors)

OR 16 days with R1 ON R2 OFF OR 29 days with R1 OFF R2 ON

- 4750 events - 4460 events 238 U 241 Pu 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0.66

235 U=0.47

Days 239 Pu=0.24

239 Pu=0.37

238 U=0.08

E vis in MeV 241 Pu=0.02

241 Pu=0.08

Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0 : the two “burn-up” induce identical anti n e spectra • Shape only: P KS = 0.99 (Max Distance = 0.0093)  Shapes look identical!!!

• Rate and shape: P KS = 1.8 x 10 -2  Rates are different (~7% diff. on # of anti n e )

235 U 239 Pu

Two closer burn-up in 3 weeks

(identical reactors)

- 9980 events - 9600 events 238 U 241 Pu 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0.66

235 U=0.54

Days 239 Pu=0.24

239 Pu=0.32

238 U=0.08

E vis in MeV 241 Pu=0.02

241 Pu=0.06

Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0 : the two “burn-up” induce identical anti n e spectra • Shape only: P KS = 0.997 (Max Distance = 0.006)  Shapes look identical!!!

• Rate and shape: P KS = 4.2 10 -2  Rates are different (~4 % diff. on # of anti n e )

235 U 239 Pu

Two still closer burn-up in 3 weeks

(identical reactors)

- 9980 events - 9800 events 238 U 241 Pu 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0.66

235 U=0.61

Days 239 Pu=0.24

239 Pu=0.28

238 U=0.08

E vis in MeV 241 Pu=0.02

241 Pu=0.03

Kolmogorov-Smirnov Test on Burn-up: Null hypothesis H 0 : the two “burn-up” induce identical anti n e spectra • Shape only: P KS = 1.00 (Max Distance = 0.002)  Looks identical!!!

• Rate and shape: P KS = 0.55  Rates are too close, spectra match (~2 % diff. on # of anti n 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 (try to detect an ‘abnormal’ burn-up) measurements - Double Chooz Near detector will provide an unrivalled anti n e spectrum measurement. These data will be an incredibly rich source of information in order to look for power, burn-up correlations with anti n 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

Reactor induced

n flux and s Reactor power Energy per fission Solid angle

Detector induced Analysis

Target Mass Density H/C ratio & Gd concentration Spatial effects Live time From 7 to 3 cuts

Total Chooz

1.9 % 0.7 % 0.6 % 0.3 % 0.3 % 0.3 % 1.2 % 1.0 % few % 1.5 %

2.7 %

<0.1 % <0.1 % <0.1 % <0.1 % 0.2 % <0.1 % <0.2% <0.1 % 0.25 % 0.2 - 0.3 %

< 0.6 % Double Chooz (relative)

Two ‘’identical’’ detectors, Low bkg Distance measured @ 10 cm + monitor core barycenter Same weight sensor for both det.

Accurate T control (near/far) Same scintillator batch + Stability ‘’identical’’ Target geometry & LS Measured with several methods (see next slide)

( Total ~0.45% without contingency ….)