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NOSTOS: a spherical TPC to detect low energy neutrinos Igor G. Irastorza CEA/Saclay. NOSTOS A new concept: the spherical TPC. A first prototype: the Saclay sphere. Results and prospects. NOSTOS Scheme. Large Spherical TPC 10 m radius 200 MCi tritium source in the center - PowerPoint PPT Presentation
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LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
NOSTOS:NOSTOS: a spherical TPC a spherical TPC to detect low energy neutrinosto detect low energy neutrinos
Igor G. Irastorza Igor G. Irastorza CEA/SaclayCEA/Saclay
NOSTOSNOSTOS A new concept: the A new concept: the
spherical TPC.spherical TPC. A first prototype: the A first prototype: the
Saclay sphere.Saclay sphere. Results and Results and
prospects.prospects.
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA SaclayLRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
NOSTOS SchemeNOSTOS Scheme
Large Spherical TPCLarge Spherical TPC 10 m radius10 m radius 200 MCi tritium 200 MCi tritium
source in the centersource in the center Neutrinos oscillate Neutrinos oscillate
inside detector inside detector volume Lvolume L2323=13 m=13 m
Measure Measure 1313 and and more…more…
10m
E
Shield
HighVoltage
DriftGaseousVolume
TritiumSource
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
10m
E
Shield
HighVoltage
DriftGaseousVolume
TritiumSource
The spherical TPC conceptThe spherical TPC concept(I. Giomataris, J. Vergados, NIM A530 (04) 330-358 [hep-ex/0303045] )
Drifting charges
MICROMEGASreadout
(max E=1.27 keV)(max E=1.27 keV)
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
The spherical TPC concept: The spherical TPC concept: AdvantagesAdvantages
Natural focusing: Natural focusing: – large volumes can be large volumes can be
instrumented with a small instrumented with a small readout surface and few readout surface and few (or even one) readout (or even one) readout lineslines
44 coverage: better coverage: better signalsignal
Still some spatial Still some spatial information information achievable: achievable: – Signal time dispersionSignal time dispersion
Other practical Other practical advantages:advantages:– Symmetry: lower noise Symmetry: lower noise
and thresholdand threshold– Low capacityLow capacity– No field cageNo field cage
Simplicity: few Simplicity: few materials. They can be materials. They can be optimized for low optimized for low radioactivity. radioactivity.
Low costLow cost
The way to obtain large detector The way to obtain large detector volumes keeping low background and volumes keeping low background and
thresholdthreshold
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA SaclayLRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
SourceSource & Target & Target SourceSource: 200MCi (20 kg) Tritium: 200MCi (20 kg) Tritium TargetTarget: Several possibilities as target gas:: Several possibilities as target gas:
Detailed calculation/simulation in progress to Detailed calculation/simulation in progress to assess expected signal/sensitivity, taking into assess expected signal/sensitivity, taking into account atomic effects (Gounaris account atomic effects (Gounaris et al.et al. hep-ex/0409053)hep-ex/0409053)
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
Experimental challenges: Experimental challenges: within within
reachreach ThresholdThreshold easily achievable, to be easily achievable, to be
demonstrated with underground tests demonstrated with underground tests BackgroundBackground simulations planned, to be simulations planned, to be
demonstrated with underground testsdemonstrated with underground tests Radial resolutionRadial resolution being demonstrated being demonstrated
by Saclay sphereby Saclay sphere StabilityStability first results positive, more first results positive, more
plannedplanned Scaling upScaling up intermediate size prototypes intermediate size prototypes
being designedbeing designed ElectrostaticsElectrostatics some ideas being some ideas being
demonstrated by Saclay spheredemonstrated by Saclay sphere
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First prototype: First prototype: the Saclay spherethe Saclay sphere
D=1.3 m D=1.3 m V=1 mV=1 m3 3
Spherical vessel Spherical vessel made of Cu (6 made of Cu (6 mm thick)mm thick)
P up to 5 bar P up to 5 bar possible (up to possible (up to 1.5 tested up to 1.5 tested up to now)now)
Vacuum tight: Vacuum tight: ~10~10-6-6 mbar mbar (outgassing: (outgassing: ~10~10-9-9 mbar/s) mbar/s)
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA SaclayLRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
First prototype: the Saclay First prototype: the Saclay spheresphere
Simple multiplication structure: Simple multiplication structure: small (10 mm small (10 mm Ø) Ø) spheresphere
Internal electrode at HVInternal electrode at HV Readout of the internal electrodeReadout of the internal electrode
10 mm10 mm
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First testsFirst tests Mixtures tested: Mixtures tested:
– Ar+10% COAr+10% CO22
– Ar+2% IsobutaneAr+2% Isobutane Pressures from 0.25 Pressures from 0.25
up to 1.5 bar tested up to 1.5 bar tested up to nowup to now
High gains (>10High gains (>1044) ) achieved with simple achieved with simple spherical electrodespherical electrode
No need to go to very No need to go to very high V high V (better for (better for minimizing absorption)minimizing absorption)
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First resultsFirst results 5.9 keV 5.9 keV 5555Fe signalFe signal
• Very low electronic noise: low threshold
• Fit to theoretical curve including
avalanche induction and electronics: system
well understood
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First resultsFirst results
Runs of Runs of 5555Fe, Fe, 109109Cd Cd and Cosmic Raysand Cosmic Rays
Better resolution Better resolution obtained in more obtained in more recent tests with recent tests with Isobutane Isobutane (analysis in (analysis in progress)progress)
55Fe55Fe 5.9 keV5.9 keV
Ar Ar escapeescape
5555Fe Fe spectrum spectrum
with Ar+COwith Ar+CO22
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
Pulse deconvolutionPulse deconvolution
Response function Response function including the ion including the ion induction + electronics induction + electronics effects associated to effects associated to one single point charge.one single point charge.
Remove the slow tail of Remove the slow tail of the pulsesthe pulses
Recover the time Recover the time (=radial) structure of (=radial) structure of the primary ethe primary e-- cloud cloud
This analysis will not be This analysis will not be needed when a fast needed when a fast readout (MICROMEGAS) readout (MICROMEGAS) will be availablewill be available
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First resultsFirst results
Clear time Clear time dispersion effect dispersion effect observed in observed in deconvoluted deconvoluted pulses correlated pulses correlated with distance with distance drifteddrifted
60 cm drift
50 cm drift
40 cm drift
30 cm drift
20 cm drift
10 cm drift
Template pulses
(average of 20 sample
pulses)
In Ar+CO2
P=0.25 bar
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First resultsFirst results Even with a very Even with a very
simple (and slow) simple (and slow) readout, we have readout, we have proved the use of proved the use of dispersion effects dispersion effects to estimate the to estimate the position of the position of the interation (at least interation (at least at ~10 cm level).at ~10 cm level).
Further test are Further test are under preparation under preparation to better calibrate to better calibrate (external trigger (external trigger from Am source )from Am source )
Average time dispersion of 5.9 keV deconvoluted events
VS.
Distance drifted
No s
ou
rce r
un
(c
osm
ics)
Ar+CO2P=0.25 bar
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
First resultsFirst results
Stability: Stability: – tested up to ~2 months.tested up to ~2 months.– No circulation of gas. Detector working No circulation of gas. Detector working
in sealed mode. (1 pass through an in sealed mode. (1 pass through an oxysorb filter)oxysorb filter)
No absorption observedNo absorption observed– Signal integrity preserved after 60 cm Signal integrity preserved after 60 cm
drift.drift.– Not high E needed to achieve high gain.Not high E needed to achieve high gain.
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
Next stepsNext steps
ElectrostaticsElectrostatics
– Field shaping ringsField shaping rings
– More ambitious ideas in mind for the More ambitious ideas in mind for the future: charging systems without electrical future: charging systems without electrical contact contact (like the ones in electrostatic (like the ones in electrostatic accelerators)accelerators)
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
Next stepsNext steps: : Micromegas as NOSTOS Micromegas as NOSTOS
readoutreadout Very fast signals: will allow to measure precisely time Very fast signals: will allow to measure precisely time
(and space) dispersion, i.e. radial coordinate of event.(and space) dispersion, i.e. radial coordinate of event.
Spherical MICROMEGAS (?) (or series of flat elements)Spherical MICROMEGAS (?) (or series of flat elements)
2 Typical MICROMEGAS
pulses
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
NOSTOS Additional PhysicsNOSTOS Additional Physics
Neutrino Neutrino magnetic magnetic momentmoment
Test of weak Test of weak interaction at low interaction at low energy energy (Weinberg angle)(Weinberg angle)
Supernovae Supernovae (neutrino-nucleus (neutrino-nucleus scattering)scattering) McLaughlin & Volpe PLB 591 (04) 229
10-12B10-11B
NO MM
LRT2004 Sudbury, 12-14 LRT2004 Sudbury, 12-14 December 2004December 2004
Igor G. Irastorza, CEA SaclayIgor G. Irastorza, CEA Saclay
ConclusionsConclusions Spherical TPC concept introduced in the Spherical TPC concept introduced in the
framework of NOSTOS proposalframework of NOSTOS proposal Promising as a simple way to obtain large Promising as a simple way to obtain large
detector volumes, keeping low background detector volumes, keeping low background and low threshold and low threshold
First prototype already working in SaclayFirst prototype already working in Saclay First encouraging results: low threshold, First encouraging results: low threshold,
stability, no absorption, dispersion vs. drift stability, no absorption, dispersion vs. drift observed.observed.
To be done next: optimize electrostatics, To be done next: optimize electrostatics, develop more calibration systems, assess develop more calibration systems, assess background (test underground)background (test underground)