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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