soli - wright laboratory · soli∂ detectors friday, 6 february 15. solid technology development...

Search for oscillations with 6Li detector at short distance from the BR2 MTR

reactorAntonin Vacheret

for the SoLid collaboration

SoLi∂

Friday, 6 February 15

Outline

• Anomalies in neutrino sector

• SoLid experiment overview

• SoLid technology

• recent developments


Recent anomalous results

Giunti Laveder 1006.3244J. Kopp et al., hep/ph:1303.3011

⌫̄e + p ! e+ + n

+4%

+1.5%+1%

• re-analysis of calibration source data • (L/E ~1m/0.1MeV)

• rate deficit of 14 ± 6 %

• Gallium anomaly

• 2011 re-evalatation of reactor antineutrino flux and update on cross-section parameters

• 3.5% new conversion of ILL beta spectra• 1.5% off-equilibrium• 1.5% neutron lifetime τn

• rate deficit 6.5 %• Reactor anomaly


2011 Reactor anomaly

• Oscillation in a new kind of matter ?

4

10 100distance from reactor [m]

0.7

0.8

0.9

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2.7σ deficit

?

PredictionActualOscillation into new state


Deficit explained : solar neutrinos oscillates into other neutrinos !

Are we in a similar situation ?

1988 Solar anomaly

5

~6σ deficit


Sterile neutrino hypothesis

• current rate anomalies due to unknown effect or to new physics ?

• additional(s) light fermion mixing with active neutrinos could be one explanation

• a generic extension of SM

• help with phenomenology (connection to DM is possible)

• tension exists between oscillation data sets

• in modest tension with PLANCK data

Energy2 3 4 5 6 7 8 9 10

A. U

.

00.20.40.60.81

1.21.41.61.82

Energy2 3 4 5 6 7 8 9

Ratio

Osc

/non

-Osc

0.5

0.6

0.7

0.8

0.91

1.1

[MeV]

J. Kopp et al., hep/ph:1303.3011

Δm2 ~ 1 eV2νe → νs

Pee = 1 − 2|Ue4|2(1 − |Ue4|2)

Effect as a function of distance

Δm2=2.35 eV2

sin22θee = 0.165

Effect as a function of energy


Allowed region

• Combined no oscillation disfavored at more than 99.9% C.L. (3.3σ)

• Two techniques in νe disappearance to address this on a short timescale:

• 1. Large source, large detector experiments

• 2. very short baseline [5-20] m reactor experiments

J. Kopp et al., hep/ph:1303.3011Sterile neutrino white paper arXiv:1204.5379

90, 95, 99 % CL.


Look for rate and energy variations

Need better experiments !

Energy2 3 4 5 6 7 8 9 10

A. U

.

00.20.40.60.81

1.21.41.61.82

Energy2 3 4 5 6 7 8 9

Ratio

Osc

/non

-Osc

0.5

0.6

0.7

0.8

0.91

1.1

[MeV]

Δm2=2.35 eV2

sin22θee = 0.165

Effect as a function of energy

8

Data scarce at short distance :

Control of background is key for best sensitivity


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Rat

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Recent reactor data

• Total rate measurements compatible with other experiments

• 2.4σ sigma deficit including Daya Bay nu2014 result

• Deviation in e+ spectrum observed at all three experiments (D-CHOOZ, RENO, Daya Bay)

• 4σ excess in [4,6] MeV window in Daya Bay data

• no effect on θ13 measurement

• Is it a real feature of the spectrum or something else ?

• Measurement with HEU and different technology

Daya Bay

D-Chooz

RENO

Eν ≃ Ee+ + mn - mp


New Reactor experiments

10

Prospect - ORNLNeutrino-4 - SM3DANSS - KNPP

POSEIDON - PIK

STEREO - ILL

SoLid - BR2

Korean projectCARR project


SoLi∂


SoLid Collaboration• 3 countries, 9 institutes, ~40 people

12

UK Belgium France


SCK•CEN BR2 reactor

• Tank in Pool MTR research reactor

• Licensed to run at power up to 100 MW

• variable operating power (45-80 MW)

• 6 cycles per year*

• Beam ports not in use

• Primary circuit pipes away from experimental site

• ~10 mwe overburden on level 3

Level 10m67on axis with reactor

Confinement building

* will increase from 2016


Aluminum pressure Vessel

Beryllium matrixand assemblies

1.0 m

BR2 Twisted core

BR2

ILL


BR2 background measurementsBackground rates at level 3

• Neutrons

• Large system to measure atm neutrons

• Rn ~ 1Hz En < 15 MeV

• Reactor ON : portable neutron counter :

• Rn < 10-5 Hz (2-20 MeV)

• Reactor ON gamma-rays

• HPGe detector w and w/o shielding

• Rgam ~ 0.4 Hz/cm2 (> 500 KeV) Pb 5cm

BR2Entries 12291Mean 773.1RMS 776.7

Energy [keV]1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

-210

-110

1

10

BR2Entries 12291Mean 773.1RMS 776.7

No shieldingPb shield 5 cm

BR2 HPGe detectorBR2 portable neutron detector Oxford Large

neutron detector

41Ar

60Co

208Tl24Na

40K


Crosscheck with Floor 1

• Ge energy efficiency checked with nitrogen decay gammas

• 1st floor just behind concrete wall

• 1 hour exposure time

• Rgam ~ 140 Hz/cm2 (> 500 KeV)

• rate x350 and hard spectrum

Energy (keV)1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Entri

es10

210


Reactor core calculations


SoLid experiment set up

• Baseline L = 5.5-11 m

• reconfigurable to reduce detector systematics

• 2.88 tonnes total fiducial mass

• Limit passive shielding

• Data taking in early 2016

BR2 coreSoLid

Detectors

Neutron shielding

lead wall

5.5m

• Good energy resolution Eres~ 17% @ 1 MeV

• Use high position resolution (<5cm)


Expected sensitivity• Event rate 416 νe/day/ton

• 2.88ton detector mass

• Energy resolution : 0.17 at 1 MeV

• 300 days running (140 days/year)

• Positron threshold (600 keV)

• S:B of 6:1 assumed

• Systematics

• Spectrum norm.: 1.8%

• Spectrum shape: 0.7-4%

• Thermal power: 3%

• Detection efficiency 2%


SoLi∂ technology


SoLid concept

• Neutron / gamma-ray discrimination from pulse

• distinctive response for prompt and delayed signal

• neutron used to trigger event read out

• Voxelisation of target volume

• neutron captured in neighboring cube increasing localisation of IBD event

s)µTime (0 5 10 15 20 25

Hei

ght (

ADC

)

02000400060008000

10000120001400016000180002000022000

s)µTime (0 5 10 15 20 25

Hei

ght (

ADC

)

0

200

400

600

800

1000

1200

Δt ~ 1-200 us

⌫̄e + p ! e+ + n

1 m 1 m


Optimisation of Voxel size

• Require good containment for e+ energy

• 85% are contained within one cube of 5 cm

• neutrons caught in proximity of positron

• reduce volume for event selection

• background reduction


Energy response

• Tested light yield for 5cm cube with 3mm2 MPPC read out using cosmics setup

• Large light yield measured on real dimension PVT cubes with BCF-91A fibre and MPPC read out

• 40-50PE @ 1 MeV (x2 MPPC)

• dE/E ~ 17%

• Optical model tuned on data

• Very good uniformity within cube (>95%)

• High IBD reconstruction efficiency

• Flat in energy both for e+ and neutron

S1

S2MPPC

fibre bundleEJ-200picoscope

muon

MC

DATAMC

Correction of MPPC linearity response not included !


Enabling imaging of interactions

• Locate precisely neutrino interaction

• New way to reject ALL class of backgrounds

• Mitigate unknown backgrounds

24

Fast n

νe

= 1 Hit + neutron capture

Fast n

= N x 3D Hits + neutron capture

Homogenous volume :

Volume divided in voxels :


Additional discrimination

25

n99.90% rejection

Reconstructed Visible Energy [NPE]0 20 40 60 80 100 120 140 160 180 200

Entri

es

10

210

310

96.86% rejection γ

MC

MC


Expected IBD efficiency

• IBD selection :

• Look for a neutron trigger

• apply time cut 300 ns < Δt < 100,000 ns

• Select MPPC pair E > ~600 keV around trigger

• apply position cut (2 cubes max around trigger)

cut Efficiency

n trigger 0.71

coincidence 0.58

Energy cut (20PE/600keV) 0.48

spatial cut 0.47

multiplicity cut 0.41


SoLi∂ detectors


SoLid Technology development

80 cm

20 cm

• NEMENIX 8kg 64 voxels, 32 chan.

• SoLid Module 1 (SM1) 288kg

9 Detector planes2304 voxels, 288 chan.

20x

5x

• SoLid modules 1.440 tonnes 11520 voxels, 1920 chan.

need 2x

2013

2014-2015

2016

Proof of concept of composite scintillator technique TRL 2-31. demonstrate neutron PID2. Measure bkgs3. measure PVT-n concidence

Large scale system TRL 3-51. demonstrate scalability and test production schedule 2. demonstrate segmentation capability3. do some physics ?


Current set up

SM1288kg

NEMENIX 8kg

PbHDPE

muon veto

muon veto


Oxford 2013 prototype

• 8 Kg, 64 cubes, 32 read out channels

30


NEMENIX PID

• 2013 : good dynamic range of signal but deadtime

• 2014 : new PVT cubes and upgraded DAQ with no deadtime but threshold slightly higher and dynamic range reduced for cosmics

• PID technique demonstrated

1

10

210

310

410

510

Peak amplitude [PE]0 100 200 300 400 500 600 700 800

Inte

grat

ed c

harg

e

0

10

20

30

40

50

60310×

neutrons

EM signal : γ,e±

cosmic muons

2013 campaign

2014 campaign


Reactor studies

• can monitor neutron and PVT events

• Accidentals from gamma-rays low as expected

• dominated by environmental background at R1 alcove

• Correlated signal measured

• more data on tape to be analysed

s]µ t(ZnS - PVT) [Δ-2000 -1500 -1000 -500 0 500 1000 1500 2000

Zns

- PVT

coi

ncid

ence

s

0

20

40

60

80

100

120

140

160

180

200reactor off

reactor on

2014 campaign2014

campaign

Pth = 60 MW~7 days

exposurecharge threshold

readjusted


2014 Large scale module (x20)• 0.3 Tonnes, 9 planes, 2304 cubes, 288 channels, Fast digitiser electronics

• 8 months from construction to commissioning !

33

cube filling

Commissioning at Gent November 2014Detector Plane assembly

Detectorframes design

frame machining @ Oxford

Sensor PCB production

Oxford

FE electronics Oxford


Construction and target mass

• All material composing planes weighed to better than 1%34


Plane testingOctober 2014

• First characterisation of plane response

• using final electronics !

• ON-OFF response

• using Cs and Co sources

• First measurement of attenuation length

• Indication of Latt ~15%/m

35


SM1 installation at BR2Detector wrapping Loading at Gent

alignment in front of R1position known to ~2mm

Detector in position 27th November 2014


SM1 outlook

• As of today SM1 currently under commissioning

• commissioning trigger

• BR2 running until end of February

• Rate measurement at 5.5m : Aim to reach <5% statistical accuracy

• measure IBD efficiency and reconstruct energy spectrum


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• The SoLid experiment can achieve unprecedented sensitivity to short baseline oscillations

• It is designed for high sensitivity

• if sterile neutrinos are the explanation it will be ground-breaking discovery !

• BR2 reactor well suited for a low risk and precise experiment

• Main phase of experiment planed for 2016

• Concept has been validated with first prototype

• Large scale module under commissioning at closest distance

• Technology has real potential for antineutrino detection which opens the path to various applications

Summary


The End


New reactor experimentsTech Reactor P [MW] L (m) M (tonnes)

Nucifer (Fr) LS+Gd OSIRIS 70 7 0.8

POSEIDON LS+Gd PIK 100 5-8 ~3

STEREO (Fr) LS+Gd ILL 57 8.8-11.2 1.75

Neutrino-4 (Ru) LS+Gd SM3 100 6-12 1.5

PROSPECT (US) LS + Gd/6Li ORNL HFIR 85 7-18 1 & 10

SoLid (UK/B/Fr) PVT + 6LiF:ZnSSCK•CEN

BR245-80 5.5-11 1.44/2.88

DANSS (Ru) PS + Gd KNPP 3000 9.7-12.2 0.9

Hanaro (KO) PS + Gd/6LiHanaro/

Younggwang30-2800 6-? ~1


soli - wright laboratory · soli∂ detectors friday, 6 february 15. solid technology development...

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