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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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Presentation on theme: "1 CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 7 January 2006, Cracow, Poland ● Introduction ● Neutrino mass determination ● The Karlsruhe."— Presentation transcript:

1 1 CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER January 2006, Cracow, Poland ● Introduction ● Neutrino mass determination ● The Karlsruhe TRItium Neutrino experiment KATRIN ● Conclusions Status of the KATRIN experiment Jochen Bonn Johannes Gutenberg Universität Mainz

2 2 Need for absolute mass determination e     ? Results of recent oscillation experiments:  23,  12,  m 2 23,  m 2 12 hierarchical masses degenerated masses cosmological relevant  m 2 solar  m 2 atmos normal hierarchy mimi KATRIN sensitivity limit

3 3 Previous β-spectroscopic searches for m ν Enrico Fermi (1934): dN/dE = K × F(E,Z) × p × E tot × (E 0 -E e ) × [ (E 0 -E e ) 2 – m ν 2 ] 1/2 Theoretical β-spectrum near endpoint E o → no dependency on nuclear structure for tritium β-decay → no need for absolute intensity calibration m ν = 0eV m ν = 1eV E e -E 0 [eV] Experimental requirements: high count rate near E 0 excellent energy resolution long term stability low back ground rate ~ m ν 2 ~ m ν

4 4

5 5 Principle of an electrostatic filter with magnetic adiabatic collimation (MAC-E) adiabatic magnetic guiding of  ´s along field lines in stray B-field of s.c. solenoids: B max = 6 T B min = 3×10 -4 T energy analysis by static retarding E-field with varying strength: high pass filter with integral  transmission for E>qU

6 6 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 possible Monoenergetic line at 17.8 keV 83 Rb/ 83m Kr 10 eV

7 7 The Mainz neutrino mass experiment frozen T 2 on HOP graphite at T=1.86 K A=2cm 2, d~130 monolayers (~45nm) 20 mCi activity spectrometer: 4 m lenght, 0.9 m diameter  E=4.8 eV m ν 2 = -0.7 ± 2.2 ± 2.1 eV 2 m ν < % C.L.

8 8 The requirements for a new direct m ν experiment with sub-eV sensitivity The tritium β-decay is the best possible source: The low endpoint energy E 0 = 18.6 keV dN/dE ≈ (1/E 3 ) in the mass sensitive region No dependence on nuclear structure superalloved transition ½ + → ½ + Known excited states for gaseous daughter ion (T 3 He )+ the first excited electronic state is at 27 eV but rotational-vibrational excitations of the ground (T 3 He )+ state with average energy of 1.6 eV and width of 0.4 eV

9 9 Known electron energy losses in gaseous tritium the last 12 eV of β-spectrum are free of inelastically scattered electrons Tritium T ½ = 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 m ν (2eV → 0.2eV) 100 x better sensitivity on m ν 2 (3eV 2 →0.03eV 2 ) Improve both resolution and luminosity!

10 10 The Karlsruhe TRItium Neutrino Experiment Academy of Sciences of the Czech Republic Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft

11 11 KATRIN location at FZKarlsruhe TLK now TLK expanded (+ 2/3 of transport hall)

12 12 Hole in the wall of the Tritium Laboratory Karlsruhe September 2005

13 13 T 2 injection rate: 1.8 cm 3 /s (± 0.1%) Windowless Gaseous Tritium Source (WGTS) 16 m T 2 injection T 2 pumping Total pumping speed: l/s Magnetic field: 3.6 Tesla (± 2%) Source tube temperature: 27 K (± 0.1% stable) at pressure of 3.4 ·10 -3 mbar Isotopic purity >95% WGTS tube: stainless steel,10 m length, 90 mm diameter

14 14 Requirements: adiabatic electron guiding T 2 reduction factor of ~10 11 Background due to tritium decay in the main spectrometer <1 mHz ! Filling rate of 1.7 · Bq/s 4.7 · β-particles /sec are guided to spectrometers

15 15 Test of the inner loop of the tritium gaseous source Summer 2005

16 16 Tandem of electrostatic spectrometers pre-spectrometer main spectrometer fixed retarding potential ≈ 18.45kVvariable retarding potential 18.5 – 18.6 kV Ø = 1.7m; length = 3.5m Ø = 10m; length = 24m  E ≈ 60 eV  E = 0.93 eV (18.575keV) electrostatic pre-filtering & analysis of tritium ß-decay electrons ~10 10  ´s/sec ~10 3  ´s/sec ~10  ´s/sec (qU=E 0 -25eV)

17 17 UHV: p ≤ mbar „massless“ inner electrode system to protect against secondary electrons from the walls inner electrode installed in Mainz spectrometer for background tests intrinsic det. bg 1.6mHz 2.8mHz Results from the Mainz spectrometer: Minimisation of spectrometer background

18 18 Vacuum in the main spectrometer UHV: p ≤ mbar Bake up at 350º C for outgassing rate  mbar l s -1 cm -2 (400 kW power is needed, 12 cm increase in length) Non-evaporable getter pumps: 5 ·10 5 l s -1 (mainly for hydrogen from the walls) Turbomolecular pumps: l s -1 (mainly for hydrogen set free during NEG activation)

19 19 CU + PB SHIELD SCINTILLATOR VETO The elements of the detector design

20 20 Calibration and monitoring of the energy scale Two independent ways of monitoring: 1)Precise measurement of the retarding high voltage but no HV dividers for tens of kV on ppm level are commercially available 2) Monitor spectrometer on the same HV + physical standard of monoenergetic electrons but no precision standards for region of tens keV Reason: E kin = E exc - E bin and E bin is sensitive to phys. & chem. environment  E bin up to a few eV! Calibration with gaseous 83m Kr admixed to T 2

21 21 The high precision HV divider The first test at Sept 2005: stable on sub-ppm level at 32 kV for 16 hours

22 22 Monitor Spectrometer Precise monitoring of the main spectrometer energy scale: precise measurement of retarding potential + comparison to reference energy pre spectrometer main spectrometer detector HV-supply voltage divider/ voltage measurement monitor spectrometer (magnified) reference source of nuclear or atomic transition reference detector Mainz spectrometer modified to 1 eV resolution β-particles

23 23 Systematic uncertainties any not accounted variance  2 leads to negative shift of m 2 :  m 2 = -2  2 1. inelastic scatterings of ß´s inside WGTS - requires dedicated e-gun measurements, unfolding techniques for response fct. 2. fluctuations of WGTS column density (required < 0.1%) - rear detector, Laser-Raman spectroscopy, T=30K stabilisation, e-gun measurements 3. transmission function - spatially resolved e-gun measurements 4. HV stability of retarding potential on ~3ppm level required - precision HV divider (PTB), monitor spectrometer beamline 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 few contributions with each:  m 2  eV 2

24 24 55 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

25  H.-V. Klapdor-Kleingrothaus et al., NIM A 522 (2004) 371 claim for = 0.4 eV (4.2  ) [ eV] including matrix el. E 0 =2039 keV KATRIN sensitivity & discovery potential

26 26 Absolute neutrino mass scale needed for particle physics and astrophysics/cosmology by direct neutrino mass measurement (less model dependent & complementary) Direct  mass  measurement from tritium  decay: ● 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 eV (for m( e )   )  key experiment to fix the absolute neutrino mass scale design for most parts finished, first parts of the setup already installed major compenents have been ordered Summary


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