1 CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 7 January 2006, Cracow, Poland ● Introduction ● Neutrino mass determination ● The Karlsruhe TRItium Neutrino experiment KATRI ● Conclusions Status of the KATRIN experiment Jochen Bonn Johannes Gutenberg Universität Mainz [email protected]
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1 CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 7 January 2006, Cracow, Poland ● Introduction ● Neutrino mass determination ● The Karlsruhe.
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CRACOW EPIPHANY CONFERENCEON NEUTRINOS AND DARK MATTER5 - 7 January 2006, Cracow, Poland
● Introduction
● Neutrino mass determination
● The Karlsruhe TRItium Neutrino experiment KATRIN
Enrico Fermi (1934):dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – mν
2 ]1/2
Theoretical β-spectrum near endpoint Eo → no dependency on nuclear
structure for tritium β-decay
→ no need for absolute intensity
calibration mν = 0eV
mν = 1eV
-3 -2 -1 0 Ee-E0 [eV]
Experimental requirements:• high count rate near E0
• excellent energy resolution• long term stability• low back ground rate
~ mν2
~ mν
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Principle of an electrostatic filter withPrinciple of an electrostatic filter withmagnetic adiabatic collimationmagnetic adiabatic collimation (MAC-E) (MAC-E)
adiabatic magnetic guiding of ´s along field lines in stray B-field of s.c. solenoids:Bmax = 6 TBmin = 3×10-4 T
energy analysis bystatic retarding E-fieldwith varying strength:
high pass filter withintegral transmissionfor E>qU
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Electron spectrometers of MAC-E-Filter Type
Advantages:• High luminosity and high resolution simultaneously• No scattering on slits defining electron beam• No high energy tail of the response function
Disadvantages:• Danger of magnetic traps for charged particles
Integral spectra: low energy features superimposed on background from high energy part)
not important for endpoint region of β-spectrum
MAC-E-TOF mode is possibleMonoenergetic line at 17.8 keV
83Rb/83mKr
10 eV
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The Mainz neutrino mass experiment
frozen T2 on HOP graphite at T=1.86 K A=2cm2, d~130 monolayers (~45nm)20 mCi activity
spectrometer: 4 m lenght, 0.9 m diameterE=4.8 eV
mν2 = -0.7 ± 2.2 ± 2.1 eV2
mν < 2.3 eV @ 95% C.L.
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The requirements for a new direct mν experimentwith sub-eV sensitivity
The tritium β-decay is the best possible source:
• The low endpoint energy E0= 18.6 keV
dN/dE ≈ (1/E3) in the mass sensitive region
• No dependence on nuclear structure superalloved transition ½+ → ½+
• Known excited states for gaseous daughter ion (T3He)+
the first excited electronic state is at 27 eV but rotational-vibrational excitations of the ground (T3He)+ state with average energy of 1.6 eV and width of 0.4 eV
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• Known electron energy losses in gaseous tritium the last 12 eV of β-spectrum are free of inelastically scattered
electrons
• Tritium T½ = 12.3 y still acceptable specific activity of the source
Electron spectrometer: a very large MAC-E-Filter with superior parameters
In comparison with the present experiments at Mainz and Troitsk:10x better sensitivity on mν (2eV → 0.2eV)100 x better sensitivity on mν
2 (3eV2 →0.03eV2)
Improve both resolution and luminosity!
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The Karlsruhe TRItium Neutrino Experiment
Academy of Sciencesof the Czech Republic Forschungszentrum Karlsruhe
in der Helmholtz-Gemeinschaft
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KATRIN location at FZKarlsruhe
TLK now
TLK expanded (+ 2/3 of transport hall)
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Hole in the wall of the TritiumLaboratory KarlsruheSeptember 2005
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T2 injection rate:
1.8 cm3/s (± 0.1%)
Windowless Gaseous Tritium Source (WGTS)
16 m
T2 injectionT2 pumping
Total pumping speed: 12000 l/s
Magnetic field: 3.6 Tesla (± 2%)
Source tube temperature: 27 K (± 0.1% stable)
at pressure of 3.4 ·10-3 mbar
Isotopicpurity>95%
WGTS tube: stainless steel,10 m length, 90 mm diameter
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Requirements:adiabatic electron guiding T2 reduction factor of ~1011
Background due to tritium decay in the main spectrometer <1 mHz !
Filling rate of 1.7 · 1011Bq/s
4.7 · 1010 β-particles /sec are guided to spectrometers
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Test of the inner loop of the tritium gaseous source
Summer 2005
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Tandem of electrostatic spectrometers
pre-spectrometer main spectrometerfixed retarding potential ≈ 18.45kV variable retarding potential 18.5 – 18.6 kVØ = 1.7m; length = 3.5m Ø = 10m; length = 24mE ≈ 60 eV E = 0.93 eV (18.575keV)
5. WGTS charging due to remaining ions (MC: < 20mV)
- inject low energy meV electrons from rear side, diagnostic tools available
6. final state distribution
- reliable quantum chem. calculations
a fewcontributions
with each:m
2 0.007 eV2
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KATRIN sensitivity & discovery potential
m < 0.2eV (90%CL)
m = 0.35eV (5)
m = 0.3eV (3)
sensitivity
discovery potential
expectation:
after 3 full beam years syst ~ stat
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6.5
H.-V. Klapdor-Kleingrothaus et al., NIM A 522 (2004) 371
claim for <mee> = 0.4 eV (4.2)
[0.1-0.9eV] including matrix el.
E0=2039 keV
KATRIN sensitivity & discovery potential
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Absolute neutrino mass scale needed for particle physics and astrophysics/cosmologyby direct neutrino mass measurement (less model dependent & complementary)
Directmassmeasurement from tritiumdecay:●Mainz finished (all problems solved):
m(e) < 2.3 eV (95% C.L.)
● KATRIN: A large tritium neutrino mass experiment with sub-eV sensitivity m(
e) < 0.2 eV or m(
e) > 0 eV (for m(
e) 0.30 eV @ 3)
key experiment to fix the absolute neutrino mass scale design for most parts finished, first parts of the setup already installedmajor compenents have been ordered