CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 7 January 2006, Cracow, Poland

1. Status of the KATRIN experiment CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 7 January 2006, Cracow, Poland Jochen Bonn Johannes Gutenberg Universität Mainz Jochen.Bonn@uni-mainz.de • Introduction • Neutrino mass determination • The Karlsruhe TRItium Neutrino experiment KATRIN • Conclusions

2. ? e 1 2 3 normal hierarchy mi m2atmos m2solar Need for absolute n mass determination Results of recent oscillation experiments: 23, 12, m223, m212 degenerated masses cosmological relevant KATRIN sensitivity limit hierarchical masses

3. Previous β-spectroscopic searches for mν Enrico Fermi (1934): dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – mν2 ]1/2 Theoretical β-spectrum near endpoint Eo → no dependency on nuclear structure for tritium β-decay → no need for absolute intensity calibration ~ mν2 mν = 0eV ~ mν • Experimental requirements: • high count rate near E0 • excellent energy resolution • long term stability • low back ground rate mν = 1eV -3 -2 -1 0 Ee-E0 [eV]

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

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 83Rb/83mKr 10 eV Monoenergetic line at 17.8 keV

7. 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 diameter • E=4.8 eV mν < 2.3 eV@ 95% C.L. mν2 = -0.7 ± 2.2 ± 2.1 eV2

8. The requirements for a new direct mνexperiment with 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

9. 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 mν2 (3eV2→0.03eV2) Improve both resolution and luminosity!

10. TheKarlsruhe TRItium Neutrino Experiment Academy of Sciences of the Czech Republic Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft

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

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

13. Windowless Gaseous Tritium Source (WGTS) WGTS tube: stainless steel,10 m length, 90 mm diameter Source tube temperature: 27 K (± 0.1% stable) Magnetic field: 3.6 Tesla (± 2%) 16 m T2 pumping T2 injection T2 injection rate: 1.8 cm3/s (± 0.1%) Total pumping speed: 12000 l/s Isotopic purity >95% at pressure of 3.4 ·10-3 mbar

14. 4.7 · 1010β-particles /sec are guided to spectrometers Filling rate of 1.7 · 1011Bq/s Requirements: adiabatic electron guiding T2 reduction factor of ~1011 Background due to tritium decay in the main spectrometer <1 mHz !

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

16. Tandem of electrostatic spectrometers pre-spectrometer main spectrometer fixed retarding potential ≈ 18.45kV variable retarding potential 18.5 – 18.6 kV Ø = 1.7m; length = 3.5m Ø = 10m; length = 24m DE ≈ 60 eV DE = 0.93 eV (18.575keV) electrostatic pre-filtering & analysis of tritium ß-decay electrons ~1010b´s/sec ~103b´s/sec ~10 b´s/sec (qU=E0-25eV)

17. Minimisation of spectrometer background • UHV: p ≤ 10-11 mbar • „massless“ inner electrode system • to protect against secondary electrons from the walls Results from the Mainz spectrometer: 2.8mHz intrinsic det. bg 1.6mHz inner electrode installed in Mainz spectrometer for background tests

18. Vacuum in the main spectrometer • UHV: p ≤ 10-11 mbar • Bake up at 350º C for outgassing rate  10-12 mbar l s-1 cm-2 (400 kW power is needed, 12 cm increase in length) • Non-evaporable getter pumps: 5 ·105 l s-1 (mainly for hydrogen from the walls) • Turbomolecular pumps: 10 000 l s-1 (mainly for hydrogen set free during NEG activation)

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

20. Calibration and monitoringof the energy scale Calibration with gaseous 83mKr admixed to T2 Two independent ways of monitoring: • 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: Ekin = Eexc- Ebin and Ebin is sensitive to phys. & chem. environment Ebin up to a few eV!

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

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

23. Systematic uncertainties any not accounted variance s2 leads to negative shift of mn2: D mn2 = -2 s2 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 resolvede-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 fewcontributionswith each: m20.007 eV2

24. KATRIN sensitivity & discovery potential expectation: after 3 full beam years ssyst~sstat mn = 0.35eV (5s) mn = 0.3eV (3s) 5s discovery potential mn < 0.2eV (90%CL) sensitivity

25. KATRIN sensitivity & discovery potential E0=2039keV 6.5s claim for <mee> = 0.4 eV (4.2s) [0.1-0.9eV] including matrix el. H.-V. Klapdor-Kleingrothaus et al., NIM A 522 (2004) 371

26. Summary Absolute neutrino mass scale needed for particle physics and astrophysics/cosmology by direct neutrino mass measurement (less model dependent & complementary) Direct n massmeasurement 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) < 0.2 eV or m(e) > 0 eV (for m(e) 0.30 eV @ 3s) 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