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Scintillation in Liquid Noble Gases

Alexander Neumeier1

Martin Hofmann1, Thomas Dandl2, Thomas Heindl2, Jochen Wieser3,Andreas Ulrich2

1Physik-Department E152Physik-Department E12

Technische Universitat Munchen3 Excitech GmbH Schortens, Germany

29.11.2013

1 Noble gases - An Overview

2 The Scintillation Process in Liquid Argon

3 Detector Concepts

4 Liquid Noble Gas Experiments

5 Summary and Conclusions

Motivations in Particle Physics

Liquefied noble gases well suited detector medium for rare eventsearch

Efficient scintillation medium with high light yields”Easily” scalableChemical purification up to a high level of purity

Good background suppression needed

⇒ Particle discrimination on an event-by-event basis

⇒ Detailed investigation of scintillation propertieswavelength- and time-resolved

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 3 / 18

Motivations in Particle Physics

Liquefied noble gases well suited detector medium for rare eventsearch

Efficient scintillation medium with high light yields”Easily” scalableChemical purification up to a high level of purity

Good background suppression needed

⇒ Particle discrimination on an event-by-event basis

⇒ Detailed investigation of scintillation propertieswavelength- and time-resolved

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 3 / 18

Scintillation of Noble Gases (e−-beam induced)

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 4 / 18

VUV Scintillation Efficiencies (e−-beam)

Morozov et al. J. Appl. Phys. 103, 103301 (2008)

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 5 / 18

Possible Candidates for Detectors

Helium and Neon1

Boiling temperature far below LN2 → cooling rather expensiveScintillation light dominantly emitted at λ <90 nm → no transparentwindow materials

ArgonSuitable candidateLow priceNatural atmospheric argon: 1Bq

kg of 39Ar (β-decay, T 12=269a,

Q=565keV)

KryptonIn principle suitable candidateBut non-negligible traces of 85Kr (β-decay, T 1

2=10.75a, Q=687keV)

XenonSuitable candidateHigh A → High σ for coherent WIMP scatteringHigh price due to low natural abundance

1LNe considered as an option in the MiniCLEAN experimentAlexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 6 / 18

Possible Candidates for Detectors

Helium and Neon1

Boiling temperature far below LN2 → cooling rather expensiveScintillation light dominantly emitted at λ <90 nm → no transparentwindow materials

ArgonSuitable candidateLow priceNatural atmospheric argon: 1Bq

kg of 39Ar (β-decay, T 12=269a,

Q=565keV)

KryptonIn principle suitable candidateBut non-negligible traces of 85Kr (β-decay, T 1

2=10.75a, Q=687keV)

XenonSuitable candidateHigh A → High σ for coherent WIMP scatteringHigh price due to low natural abundance

1LNe considered as an option in the MiniCLEAN experimentAlexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 6 / 18

Possible Candidates for Detectors

Helium and Neon1

Boiling temperature far below LN2 → cooling rather expensiveScintillation light dominantly emitted at λ <90 nm → no transparentwindow materials

ArgonSuitable candidateLow priceNatural atmospheric argon: 1Bq

kg of 39Ar (β-decay, T 12=269a,

Q=565keV)

KryptonIn principle suitable candidateBut non-negligible traces of 85Kr (β-decay, T 1

2=10.75a, Q=687keV)

XenonSuitable candidateHigh A → High σ for coherent WIMP scatteringHigh price due to low natural abundance

1LNe considered as an option in the MiniCLEAN experimentAlexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 6 / 18

Possible Candidates for Detectors

Helium and Neon1

Boiling temperature far below LN2 → cooling rather expensiveScintillation light dominantly emitted at λ <90 nm → no transparentwindow materials

ArgonSuitable candidateLow priceNatural atmospheric argon: 1Bq

kg of 39Ar (β-decay, T 12=269a,

Q=565keV)

KryptonIn principle suitable candidateBut non-negligible traces of 85Kr (β-decay, T 1

2=10.75a, Q=687keV)

XenonSuitable candidateHigh A → High σ for coherent WIMP scatteringHigh price due to low natural abundance

1LNe considered as an option in the MiniCLEAN experimentAlexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 6 / 18

The Excimer Potential

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 7 / 18

The Emission Spectrum of Liquid Argon

Hofmann et al. Eur. Phys. C (2013) 73:2618Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 8 / 18

Gas Kinetic Processes

Incident particle χ

? ? ?multiple ionisation

Ar + χ→Ar x+ + x · e− + χ′

excitation

Ar + χ→ Ar∗∗ + χ′ionisation

Ar + χ→Ar+ + e− + χ′

?ionic excimer

Ar+ + Ar → Ar+2

?-losses

recombination

Ar+2 + e− → Ar∗∗ + Ar

�

?de-excitation

Ar∗∗ → Ar∗

?� -excimer

Ar∗ + Ar → Ar∗2

resonance linesAr∗ ↔ Ar + γ

?third continuum

?first cont. / second cont. / LTP Ar∗2 → 2Ar + γ

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 9 / 18

Time Structure of the Second Continuum Emission

Hofmann et al. Eur. Phys. C (2013) 73:2618

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 10 / 18

Fitted Time Constants (Second Continuum Peak Emission)

projectile τs [ns] τt [ns] IsIt

Ref.

32S 6.47 ± 0.09 1224.0 ± 17.9 2.19 ± 0.07 (1)

p+ 3.20 ± 0.02 1355.8 ± 5.8 0.28 ± 0.01 (1)

e− <6.2 1300 ± 60 0.51 ± 0.05 (2)

IsIt

=

∫∞0 As ·exp{− t

τs}dt∫∞

0 At ·exp{− tτt}dt

(1) Hofmann et al. Eur. Phys. C (2013) 73:2618(2) Heindl et al. EPL, 91 (2010) 62002

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 11 / 18

Single Phase Detectors

Figure: arXiv:1206.2169v1 (2012)

Simple sphercial geometry:

→ Good self shielding→ Good optical coveragepossible

Particle identification:

Only time information→ Big difference between τsand τt necessary

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 12 / 18

Single Phase Detectors

Figure: arXiv:1206.2169v1 (2012)

Simple sphercial geometry:

→ Good self shielding→ Good optical coveragepossible

Particle identification:

Only time information→ Big difference between τsand τt necessary

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 12 / 18

Double Phase Detectors, (TPCs)

Figure: arXiv:1206.2169v1(2012)

Simultaneous measurement ofscintillation and ionization

3D vertex reconstruction →z-resolution: <1 mm, xy-resolution∼3 mm (XENON100)

Powerful background rejection:

FiducializationMulti scatter-identificationChargeLight → Particle identification

Pulse shape discrimination (LArdetectors)

Optical coverage and light yield smallercompared to single phase → increasedthreshold

Technical challenges of highvoltage system

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 13 / 18

Double Phase Detectors, (TPCs)

Figure: arXiv:1206.2169v1(2012)

Simultaneous measurement ofscintillation and ionization

3D vertex reconstruction →z-resolution: <1 mm, xy-resolution∼3 mm (XENON100)

Powerful background rejection:

FiducializationMulti scatter-identificationChargeLight → Particle identification

Pulse shape discrimination (LArdetectors)

Optical coverage and light yield smallercompared to single phase → increasedthreshold

Technical challenges of highvoltage system

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 13 / 18

Double Phase Detectors, (TPCs)

Figure: arXiv:1206.2169v1(2012)

Simultaneous measurement ofscintillation and ionization

3D vertex reconstruction →z-resolution: <1 mm, xy-resolution∼3 mm (XENON100)

Powerful background rejection:

FiducializationMulti scatter-identificationChargeLight → Particle identification

Pulse shape discrimination (LArdetectors)

Optical coverage and light yield smallercompared to single phase → increasedthreshold

Technical challenges of highvoltage system

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 13 / 18

Double Phase Detectors, (TPCs)

Figure: arXiv:1206.2169v1(2012)

Simultaneous measurement ofscintillation and ionization

3D vertex reconstruction →z-resolution: <1 mm, xy-resolution∼3 mm (XENON100)

Powerful background rejection:

FiducializationMulti scatter-identificationChargeLight → Particle identification

Pulse shape discrimination (LArdetectors)

Optical coverage and light yield smallercompared to single phase → increasedthreshold

Technical challenges of highvoltage system

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 13 / 18

Double Phase Detectors, (TPCs)

Figure: arXiv:1206.2169v1(2012)

Simultaneous measurement ofscintillation and ionization

3D vertex reconstruction →z-resolution: <1 mm, xy-resolution∼3 mm (XENON100)

Powerful background rejection:

FiducializationMulti scatter-identificationChargeLight → Particle identification

Pulse shape discrimination (LArdetectors)

Optical coverage and light yield smallercompared to single phase → increasedthreshold

Technical challenges of highvoltage system

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 13 / 18

Liquid Argon DM Experiments

Exp. Type Mass [kg] Veto Status Site

DarkSide TPC 50Water +B-doped LS

Comm.LNGS(Italy)

ArDM TPC 850Passive PEn-shield

Comm.Canfranc(Spain)

DEAP Single36001000

WaterCherenkov

Comm.SNOLab(Canada)

MiniCLEAN Single500150

WaterCherenkov

Comm.SNOLab(Canada)

DARWIN TPCtonscale

WaterCherenkov

R&D tba

MAX(Ar/Xe)

TPCtonscale

WaterCherenkov

R&DHomestake(USA)

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 14 / 18

Liquid Xenon DM Experiments

Exp. Type Mass [kg] Veto Status Site

ZEPLIN-III TPC125.1

Plasticscintillator

EndBoulby(UK)

XENON100 TPC16162

Passiveshield

ActiveLNGS(Italy)

XENON1T TPCtonscale

WaterCherenkov

R&DLNGS(Italy)

XMASS Single835100

WaterCherenkov

Re-Comm.

Kamioka(Japan)

LUX TPC370100

WaterCherenkov

ActiveHomestake(USA)

LZ TPCtonscale

tba R&D tba

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 15 / 18

Current WIMP cross-section Limits - Liquid noble Gases

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 16 / 18

The current Situation

http://luxdarkmatter.org/talks/20131030 LUX First Results.pdfAlexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 17 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18

Summary and Conclusions

Liquid noble gases → High density targets with high scintillationefficiency

Particle dependent scintillation of liquid argon investigated in ourgroup → switch over to ArXe mixtures, IR emission and pure xenon

Basically two detector concepts:

Single phase → Pulse shapeDual phase TPC → Charge

Light ratio

Bigger target volumes planned for the future → VUV lightattenuation measurements(A. Neumeier et al. Eur. Phys. C (2012) 72:2190)

Many of the DM experiments are based onLAr(upcoming)/LXe(established)

Most stringent limit at the moment in the WIMP parameter space →LUX

Alexander Neumeier (E15) JAPS-Scintillation in Liquid Noble Gases 29.11.2013 18 / 18