status of the stereo experimentnow/now2016/assets/luis-manzanillas.pdf · status of the stereo...

Status of the STEREO experiment: search for a light sterile ν at the ILL

Luis Manzanillas (LAPP - IN2P3 - CNRS / Université Savoie Mont Blanc - Université Grenoble Alpes)

On behalf of the STEREO collaboration

NOW2016 Otranto - Italy, September 2016

09-09-2016 Luis MANZANILLAS 2

Short baselines anomaliesShort baselines anomalies

● The reactor antineutrino anomaly (RAA) and gallium anomaly (GA) both show discrepancies wrt expectations at ~3σ level

● Oscillations into a light sterile neutrino state (Δm2 ~1 eV2) could account for such deficits (blue line below)

3 ν4 ν

STEREO

J.Phys. G43 (2016) 033001Phys.Rev. D83 (2011) 073006


The STEREO experimentThe STEREO experimentGoal: Search for an oscillation by looking for a distortion of the reactor νe

energy spectrum at different baselines

Pν e→νe

3+1=1−sin2

(2θee)sin2(1.27Δ m41

2 L/E)

Δm2 = 2.3 eV2

sin2(2θee

) = 0.1714

reactorν flux

10 m

Oscillation parameters for these plots:

→Good energy resolution, segmented detector


The STEREOThe STEREO collaborationcollaboration


The STEREO inner detectorThe STEREO inner detector

IBD detection: νe + p→ e+ + n

Coincidence of Prompt ( E + annihilation) and Delayed (n-Gd ≈ γ cascade of 8 MeV) signals in a time window of 50 μs

2 m3 of Gd loaded liquid scintillator (LS) segmented in 6 cells surrounded by LS without Gd (gamma catcher, GC)

Gd loaded LS6 Cells

LSw/oGdGC

8 MeV

e+

kin

LSw/oGdGC

Border cells Center

cells

4 PMTs per cell


Detector responseDetector response

● Maximize uniformity among cells

● Expected resolution of 12% at 2 MeV

→Uniform response between central and border cells

● n capture efficiency: less than 4% difference between a central and a border cell

Detailed Geant4 simulation of the detector response for 1 MeV e+

68Ge

54Mn137Cs

60Co

n-Fe n-H

AmBe

09-09-2016 Luis MANZANILLAS 7S

TE

RE

O

B4C PE Lead

Heavy concrete

The STEREO site and ILL reactorThe STEREO site and ILL reactor✔ Very compact reactor core

(diameter = 37 cm)✔ 57 MW nuclear power, highly

235U enriched ✔ Water channel overburden, 15

m.w.e ✔ 10.2 m from reactor core to

center of STEREO

- High n and gamma flux

- Magnetic field from IN20

- →Need heavy shielding

(Lead + B4C + Polyethylene +soft iron, μ-metal)

B⃗


BackgroundBackground

● Mapping of the STEREO casemate using Ge, NaI, He3 and Ne213 detectors

● Measurements of muon rates● Mapping of magnetic field

● Main sources identified → extra protection added– D19: 10 cm of lead + B4C

– Front Wall: Plug in H7 neutron guideline + 10 cm of polyethylene + 10 cm of Lead

– IN20: 10 cm of borated polyethylene + 15 cm of Lead + B4C

– H13 casemate reinforced

● Installation completed ● New campaign of measurements finished → validate

(preliminary) shielding efficiency

Measured -spectrum in the casemate PN3


Internal shieldingInternal shielding● 65 tons of lead (delivered and mounted)● 6 tons of polyethylene (delivered and

mounted)● Magnetic shielding:

➢ μ-metal installed

➢ soft iron delivered (installation ongoing)

June 2016 ILLJune 2016 ILL

Supporting structure

July 2016 ILLJuly 2016 ILL

August 2016 August 2016 ILLILL


Muon vetoMuon veto

● 396x240x26 cm3 of pure water with wavelength shifter (4MU at 6 ppm)

● 20 PMTs with 2 layers of μ-metal

● Efficiency > 99%● μ-veto moved to the

ILL and ready for installation (September)

Feb 2016 LPSCFeb 2016 LPSC


Inner detectorInner detector

● Double stainless steel vessel● Acrylic buffer between PMTs and LS● VM2000 (reflector) in the cell walls● Mounted and moved to the ILL● Installed in shielding structure● Filling in September 2016

May 2016 May 2016 May 2016 LPSCMay 2016 LPSC

May 2016 LPSCMay 2016 LPSC


The STEREO liquidThe STEREO liquid

● Composition:➢ 75% LAB → solvent➢ 20% PXE → solvent➢ 5% DIN → solvent➢ PPO + bis-MSB → fluors➢ Gd complex (0.2% Gd) + 1% THF

● Light yield ≈ 6000 photons / MeV● Attenuation length > 5m in final

mixture● GC mixture done ● Target mixture ongoing

Good pulse shape discrimination (PSD)→rejection of fast neutrons


The STEREO PMTsThe STEREO PMTs

● HAMAMATSU R5912-100 (8'')➢ Quantum efficiency ≈ 30%

➢ Dark rate: 3000 Hz

➢ Peak / valley ratio: 2.7

➢ Transit time spread: 3.5 ns

Charge (pC)

Cou

nts

Pedestal: 20.92 pCSPE: 25.74 pCCharge per PE: 4.82 pC

All PMTs tested and installed in the inner detector

PMT test setup at MPIK Heidelberg


The calibration systemThe calibration system● Three subsystems:

➢ Automated circulation around detector→Energy scale (Each cell independently + GC)

➢ Automated 1d-movement under detector→n capture efficiency inter-calibration

➢ Three manual calibration tubes →Energy scale + n capture efficiency + vertical dependence (Two central and one border cell)

Sources: 68Ge, 137Cs, 54Mn, 60Co, AmBe, 252Cf ( n-H, n-Fe)System tested and moved to the ILL →installed in August

Calibration test Calibration test setupsetup


ElectronicsElectronics● Electronics hosted in a μTCA crate ● Front-end boards tested and validated

➢ Qtot, Qtail, tCFD and pulse shape waveform➢ 8-channel FADC 14 bits 250 MHz sampling➢ Gain x1 and x20 for SPE➢ Programmable first level trigger

● Trigger board: programmable second level taking into account Target, Gamma Catcher and μ-veto

● LED board for light calibration ( light injection at 3 vertical positions in each cell)

● Extensively tested using μ-veto

μTCA crate Trigger board ● Data acquisition software built on

standard ILL framework● Slow control and monitoring ready ● All the chain successfully

tested using LEDs


Installation statusInstallation statusTested detector and acquisition with LEDs in air→Fine tuning of simulation startedStructure and shielding mountedInner detector insertedShielding roof closedInstall muon vetoMove detector to STEREO casemateFilling STEREO with LS in September


Expected sensitivityExpected sensitivity

Possible to exclude the best fit parameters region with only 100 days of data (expected 1st half 2017)

● 400 ν events / day● Signal / Bkg ≈ 1.5● L0 = 10 m

● Eprompt > 2MeV

Edelayed > 5MeV

● All systematics of predicted spectra

● ΔEscale < 2%

● Total of 300 days of data taking

New reference for 235U spectrum with ~120 000 ν's


ConclusionsConclusions

● Installation nearing completion → mounting support structure and internal shielding finished + inner detector inserted

● Detector ready for data taking in October 2016!● Goal: commissioning in autumn 2016

→ 100 days of data taking before March 2017

→ First physics results, first half of 2017!


Thanks for your attention!Thanks for your attention!

STAY TUNED!!!


Backup: Mounting procedureBackup: Mounting procedure

Supportstructure

Lead Polyethylene B shielding +Inner Detector

Cabling, tests

STEREOin casemate

Filling withLS Calibration

system

Muon veto


Light collectionLight collection

Cell of LED: 87%Neighboring: ~11%GC: ~1%Other Cells: ~1%

LEDs → light in air → light leakage measurement

status of the stereo experimentnow/now2016/assets/luis-manzanillas.pdf · status of the stereo...

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