neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors

Neutron scattering systems for calibration of dark matter Neutron scattering systems for calibration of dark matter search and low-energy neutrino detectorssearch and low-energy neutrino detectors

A.Bondar, A.Buzulutskov, A.Burdakov, E.Grishnjaev, A.Dolgov, A.Makarov, S.Polosatkin, A.Sokolov, S.Taskaev, L.Shekhtman

Novosibirsk State UniversityBudker Institute of Nuclear Physics SB RAS

Novosibirsk State Technical University

International conference: Dark matter, dark energy and their detection, 22-26 July 2013

Outline:Outline:

A problem of calibration of WIMP detectorsA problem of calibration of WIMP detectors

Neutron scattering systems for liquid noble gas detector calibration Neutron scattering systems for liquid noble gas detector calibration

- based on DD generator- based on DD generator

- based on p- based on p77Li generator Li generator


WIMPs (weakly interacting massive particles) are a one possible WIMPs (weakly interacting massive particles) are a one possible candidate for Dark Matter candidate for Dark Matter

Theoretical models predict a mass of WIMPs in the range 10-1000 GeV/cTheoretical models predict a mass of WIMPs in the range 10-1000 GeV/c22

WIMPs expected to interact with matter by elastic scattering with WIMPs expected to interact with matter by elastic scattering with production on recoil nucleus with energies ~1-100 keV, the recoil production on recoil nucleus with energies ~1-100 keV, the recoil spectrum depend on mass of the WIMP and detector velocity in the spectrum depend on mass of the WIMP and detector velocity in the Galaxy frameGalaxy frame

Recoils spectrum measurements are required for estimation of WIMP Recoils spectrum measurements are required for estimation of WIMP mass and interpretation of experimental datamass and interpretation of experimental data


R.W.Schnee, arXiv: 1101.5205v1

0

~ exp rec

rec

ER

E E r

2

4 A

A

M Mr

M M

20 0 2E M v - most probable WIMP incident energy

Recoil spectrum measurements require calibration that is establishing of Recoil spectrum measurements require calibration that is establishing of energy scale of detector responseenergy scale of detector response

Such calibration can be done by measuring of detector response from Such calibration can be done by measuring of detector response from particles produced recoil nucleus with know energy particles produced recoil nucleus with know energy


A response to electrons and recoil nucleus is different for ionization and A response to electrons and recoil nucleus is different for ionization and scintillation detectorsscintillation detectors

This difference often specified by quenching factor LThis difference often specified by quenching factor Leffeff::

EEee [keV [keVeeee] = L] = Leff eff × E× Err [keV [keVnrnr]]

e+A e+A*eA+he+A++e

R+AR+A*R+A+hR+A++eR+A’

Electrons (gammas) Nucleus

Data of ionization and scintillation quenching factors below 10 keV for Data of ionization and scintillation quenching factors below 10 keV for liquid noble gases are insufficient and controversialliquid noble gases are insufficient and controversial


D.Gastler et al. // Phys. Rev. C. 2012. V. 85. 065811 A.Manzur et al. // Phys. Rev. C. 2010. V. 81. 025808. Lippincott W.H. et al. // Phys. Rev. C. 2012. V. 86. 015807

Ar Xe Ne

Scintillation quenching factors


The project of two-phase avalanche cryogenic detector suitable for DM The project of two-phase avalanche cryogenic detector suitable for DM search have proposed in Budker INPsearch have proposed in Budker INP

The prototype of the detector is constructed in the Laboratory of The prototype of the detector is constructed in the Laboratory of Cosmology and Elementary Particle Physics of NSUCosmology and Elementary Particle Physics of NSU

The prototype will be applied for measurements of quenching factors in The prototype will be applied for measurements of quenching factors in the noble gases for recoil energy range 1-100 keVthe noble gases for recoil energy range 1-100 keV

A.Buzulutskov et al. // this conf.

Volume: 50 l

Working gases: Ar, Xe, Ne, He

Sensitivity: up to single electron (~100 eV)

Spatial resolution: ~1 mm

Measurements: both scintillation (bottom PTMs) and ionization (side PMTs)

CrAD detector of dark matter


Primary recoil nucleus required for detector calibration can be produced Primary recoil nucleus required for detector calibration can be produced by neutronsby neutrons

Recoils is produced by elastic scattering on neutronsRecoils is produced by elastic scattering on neutrons

A source of neutrons with constant energy and low divergence is requiredA source of neutrons with constant energy and low divergence is required

Neutron source

Liquidargon

Scintillation detectorof scattered neutrons

Scattering event

02

21 θn

rec sc

n

m ME E cos

m M

DM detector calibration scheme


•Isotopes (Isotopes (252252Cf)Cf)•Nuclear reactorNuclear reactor

•DD neutron generator (2.45 MeV)DD neutron generator (2.45 MeV)•pp77Li neutron generatorLi neutron generator

Neutron sources

Wide spectrum of neutronsWide spectrum of neutrons


Utilizes nuclear fusion reaction D(D,n)Utilizes nuclear fusion reaction D(D,n)33He (EHe (Enn=2.45 MeV)=2.45 MeV)

Industrial neutron generators with neutron yield 10Industrial neutron generators with neutron yield 1066 n/s is produced for n/s is produced for geophysical applicationsgeophysical applications

Neutron spot size ~1 mmNeutron spot size ~1 mm

DD neutron generatorDD neutron generator(produced by Budker INP)(produced by Budker INP)

H ydrogen generator

H eated cathodeIon source

E xtractorS uppressor

Target

Ion beam

DD neutron generator

0 30 60 90 120 150 18010

-2

10-1

100


DD neutrons scattering

Elastic scattering:Elastic scattering:

n+Arn+Arn+Arn+Arrecrec

Inelastic scattering:Inelastic scattering:

n+Arn+Arn+Ar*n+Ar*n+Arn+Arrecrec++(1.46 MeV)(1.46 MeV)

0 30 60 90 120 150 1800

50

100

150

200

250

Scattering angle, deg.

Re

co

il

en

erg

y,

ke

V

Energy of Ar recoils


Cro

ss

-se

cti

on

, b

arn

Cross-section of scattering


DD scattering system

Neutron generator

Water-filled tank

Active region of WIMP detector

Scintillation detectors of scattered neutrons

Neutron generator: 10Neutron generator: 1066 n/s n/s

Scintillators: slilbeneScintillators: slilbene

Water shield: 40 cmWater shield: 40 cm

Baseline: 80 cmBaseline: 80 cm

Count rate of scattering events ~0.1 minCount rate of scattering events ~0.1 min-1-1

60 80 100 120 1400

0.2

0.4

0.6

0.8

Recoil energy, keV

Co

un

t ra

te,

10

-10

ke

V-1

Pulse height spectrum (90 scattering)


Background suppression

Neutron background (random coincidence):Neutron background (random coincidence): - Neutron collimation- Neutron collimation

Cosmic ray background:Cosmic ray background: - Pulse shape discrimination (scintillation detector)- Pulse shape discrimination (scintillation detector)

Neutron generator

Water-filled tank




Pulse shape discrimination

Scintillation pulses from gammas and neutrons Scintillation pulses from gammas and neutrons in stilbene have different shape and can be in stilbene have different shape and can be effectively distinguishedeffectively distinguished

-50 0 50 100 150 200 250Время, нс

Fast

Slow

n

-50 0 50 100 150 200 250Время, нс

Fast

Slow

n

Time, ns

0 2000 4000 6000 8000 100000

1

2

3

4

5

6x 10

4

Slow

Fas

t

0 2000 4000 6000 8000 100000

1

2

3

4

5

6x 10

4

Slow

Fas

t

w/o neutrons w/ neutrons

2.45 MeV


Calibration in low-energy range

Calibration below 10 keV is a challenge:Calibration below 10 keV is a challenge:

cos1

sin

rec

rec

E

E-Increase of “geometric” errors for low-angle scattering: -Increase of “geometric” errors for low-angle scattering:

-Failure to shield scintillation detector from neutron source-Failure to shield scintillation detector from neutron source

Neutron generator

Water-filled tank




Calibration by inelastic scattering

Recoils energy for inelastic scattering Recoils energy for inelastic scattering to small angle tend co constant value to small angle tend co constant value -8.3 keV-8.3 keV

2~rec

rec

E

E

0 10 20 30 400

5

10

15

20

25

30


Re

co

il

en

erg

y,

ke

V

Energy of Ar recoils

Escape of “geometric” error allow to increase Escape of “geometric” error allow to increase solid angle of scintillation detector without loss solid angle of scintillation detector without loss of accuracyof accuracy

100 times gain in count rate is estimated100 times gain in count rate is estimated

Recoils with energy 1.2 keV can be produced Recoils with energy 1.2 keV can be produced with 14 MeV DT neutronswith 14 MeV DT neutrons

0 2 4 6 8 10

101

102

103

recoil energy, keV

even

t ra

te 21

Pulse height spectrum for small-angle scattering


Calibration in low-energy range

Calibration below 10 keV is a challenge:Calibration below 10 keV is a challenge:

cos1

sin

rec

rec

E

E-Increase of “geometric” errors for low-angle scattering: -Increase of “geometric” errors for low-angle scattering:

-Failure to shield scintillation detector from neutron -Failure to shield scintillation detector from neutron sourcesource

Neutron generator

Water-filled tank




Generator of tagged neutrons

Tagged neutron generator should provide effective trigger for suppression Tagged neutron generator should provide effective trigger for suppression of random coincidenceof random coincidence

The generator of tagged neutrons in under development in Budker INPThe generator of tagged neutrons in under development in Budker INP

Neutron generating reaction:Neutron generating reaction:

D+DD+Dnn(2.45 MeV)(2.45 MeV)++33HeHe(0.8 MeV)(0.8 MeV)

Recorded by build-in detector


Generator of epithermal neutrons in the reaction Generator of epithermal neutrons in the reaction 1111B(p,n)B(p,n)1111Be have been Be have been developed in Budker INP for medical applications (neutron cancer therapy)developed in Budker INP for medical applications (neutron cancer therapy)

Tandem accelerator

HV power supply

H- ion source

Proton beam:1.9 MeV, 3 mA

Neutron yield 1011 n/s

p7Li neutron generator



Generator of epithermal neutrons in the reaction Generator of epithermal neutrons in the reaction 77Li(p,n)Li(p,n)77Be have been Be have been developed in Budker INP for medical applications (neutron cancer therapy)developed in Budker INP for medical applications (neutron cancer therapy)


77Li(p,n)Li(p,n)77BeBe: reaction threshold 1.822 MeV: reaction threshold 1.822 MeV

Neutron energy is determined by beam energy and neutron escape directionNeutron energy is determined by beam energy and neutron escape direction

Operation pointEn=77 keV


Neutron escape direction, degrees

Ne

utr

on

en

erg

y,

ke

V


Operation point for Ar detector calibration:Operation point for Ar detector calibration:

=110=110, E, Epp=2.077 MeV, En=77 keV=2.077 MeV, En=77 keV

4040Ar have a peak of scattering cross-section on 77 keVAr have a peak of scattering cross-section on 77 keV

Sulphur filter can be applied for additional monochromatizationSulphur filter can be applied for additional monochromatization

The system produces Ar recoils in the range 0 - 7.5 keV The system produces Ar recoils in the range 0 - 7.5 keV

Neutron energy, keV

Sc

att

eri

ng

cro

ss

-se

cti

on

, b

arn


Conclusion


Neutron scattering systems for calibration on liquid cryogenic Neutron scattering systems for calibration on liquid cryogenic detectors are under development in the Laboratory of Cosmology detectors are under development in the Laboratory of Cosmology and and Elementary Particle Physics of NSUand and Elementary Particle Physics of NSU

The systems will allow to measure ionization and scintillation yield The systems will allow to measure ionization and scintillation yield for liquid noble gases in the range of recoil energies 0.5-200 keV for liquid noble gases in the range of recoil energies 0.5-200 keV

neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors

Documents

dark energy

dark matter theoretical

recoil energy range

constant energy

detector velocity

primary recoil nucleus

recoil spectrum measurements

lowenergy neutrino detectorsa