KArlsruhe TRIum Neutrino Experiment: Unique Closed T2 Cycle Facility for Neutrino Mass Measurement

1. KArlsruhe TRItium Neutrino Experiment at Forschungszentrum Karlsruhe. Unique closed T2 cycle facility: Tritium Laboratory Karlsruhe built for ITER. TLK ~ 75 m long Hamish Robertson, Sendai 2007

2. -decay electron spectrum… … shape determines the absolute neutrino mass squared: i K ~ [ gv2|MF|2 + gA2|MGT|2 ] F(E,Z) = Fermi function m = “mass” of electron (anti-)neutrino = i|Uei|2 mi = m in quasi-degenerate region. Present Limit: 2.3 eV (95% CL) Kraus et al. hep-ex/0412056

3. Experimental Arrangement 70 m Rear Source Transp/Pump Pre-spectrometer Main spectrometer Detector 3H e- e- 1 e- /s 103 e- /s β-decay e- e- 1010 e- /s 1010 e- /s 3He 3He 3He 3•10-3 mbar - 1 ± 1 kV 10-11 mbar - 1 - 18.4 kV 10-11 mbar -1 - 18.574 kV 0 kV Rear System: Monitor source parameters Pre-spectrometer: Rejection of low-energy electrons and adiabatic guiding of electrons Detector: Count electrons and measure their energy Source: Provide the required tritium column density Transp. & Pump system: Transport the electrons, adiabatically and reduce the tritium density significantly Main-spectrometer: Rejection of electrons below endpoint and adiabatic guiding of electrons

4. Molecular Windowless Gaseous Tritium Source (WGTS) Cu Tritium Kr beam pipe conzept: 2-Phasen Neon (sied. Flüssigkeit) T ≤±30 mK ! Helium vessel heater 2-phase Neon s.c. Conceptual design2 phase Neon cooling with operating temperature: 27–28 K • spatial (homogeneity):  0.1% • time (stability/hour):  0.1% WGTS has been ordered in Dec. 2004 Kn<<1: Hydrodynamic regime Kn~1: transitional flow Kn>>1: Free molecular regime

5. Cryogenic Pumping Section Objective: retention of remaining tritium flux, reduction factor 107 (tritium partial pressure in main spectrometer p < 10-20 mbar) Method: cryo-sorption on condensed Ar-frost Rate: <1 Ci T2 in 60 days (regeneration with warm He-gas) Cryocondensation T2 4K beam tube Cryosorption CPS-2 T2 CPS Argon snow

6. TRAP - TRitium Argon Frost Pump at FZK Inlet flow rate:  10-6 mbar l/s Isotopic composition: HT: 7% T2: 19% DT: 43% H2,D2,HD: 31% mbar 10-11 Ar 10-12 DT 10-13 6 days TRAP – experimental setup at TLK as of summer 2005 Pumping speed better than 107 l/s No tritium penetration observed !

7. Pre-spectrometer • Now onsite at FZK • Fixed retarding potential rejects low-energy electrons • Transmits electrons with energies within 300 eV of endpoint • Testbed for: • Vacuum • Heating/cooling • Electromagnetic design • Background supression electrode • Prototype detector ~4 m Please see Poster by Florian Habermehl, “Measurements with the KATRIN Pre-Spectrometer”

8. Wire Electrode in Pre-spectrometer

13. Main spectrometer • Analyzes energy of passing electrons with resolution of 0.93 eV 10 m x 30 m !

14. Transport of Main Spectrometer Manufactured just 400 km from Karlsruhe, but traveled 8800 km!

15. Arrival in Leopoldshafen: Nov 24, 2006

16. Precision Voltage Divider test at PTB, 2006 preliminary preliminary preliminary

17. Detector Section Silicon PIN diode detector • 9 cm active diameter • 500 m thick • 148 segments detector magnet B = 3-6 T “flux tube” e- pinch magnet B = 6 T post-acceleration electrode shielding & veto

18. Summary & Outlook • Goal is to determine absolute neutrino mass scale • Model independent • Sensitivity to m() = 0.2 eV (90% C.L) • 5 discovery potential if m() = 0.35 eV • Schedule: • 2009/10 Complete construction • 2010 Start of data-taking • 2011 First results • 2015 Ultimate sensitivity 5 countries 13 institutions 100 scientists

19. Fin

21. KATRIN Physics Implications Quasi-degenerate -masses m23 atm hierarchical -masses m12 solar m1 [eV] Cosmology • m as input for CMB/LSS data • Limit on  fraction of universe critical density (for m < 2.2 eV) 0.001 <  < 0.13 Particle Physics • Test if masses are quasi-degenerate 101 Mainz limit mi 100 mj [eV] Projected KATRIN sensitivity 10-1 m3 10-2 m2 m1 10-3 10-3 10-2 10-1 100 101

22. Near future weak kinematic searches Quasi-degenerate -masses Projected KATRIN limit m23 atm hierarchical -masses m12 solar m1 [eV] -decay experiments Tritium • KATRIN • Spectrometer • (rest of talk) 187Re • MARE (Microcalorimeter Arrays for a Rhenium Experiment) • Bolometer (source=detector) • Both expect to provide limit on m to 0.02 eV 101 Mainz limit mi 100 mj [eV] 10-1 m3 10-2 m2 m1 10-3 10-3 10-2 10-1 100 101

23. A window to work in Molecular Excitations

24. Systematic Uncertainties

25. Systematic Uncertainties Some of the largest uncertainties: syst,tot 0.01 eV2 Unaccounted variance 2(E) results in negative shift of m2: m2 = -22

26. Simulated KATRIN Signal • Integral spectrum is shown • 1 year run • Equal time at each HV setting • 10 mHz uniform background

27. KATRIN Overall Sensitivity Development of statistical uncertainty Total sensitivity, assuming syst 0.01 eV2 After 3 beam years (~5 calendar years), stat = syst

28. Improved sensitivity with larger system Discovery 90% CL UL

29. Pre-spectrometer • Status: • Vacuum 7•10-11 mbar (without getter) • Outgassing 7•10-14 mbar l/ s cm2 • Measurements in progress • Parameters: • Length: 3.4 m (flange to flange) • Diameter:1.7 m • Vacuum: < 10-11 mbar • Material: Stainless steel • Magnets: 4.5 T

30. Source and Transport System 3H  3He + e- + e B = 3.6 T • Windowless Gaseous Tritium Source WGTS • Purity > 95% T2 • Column density: 5x1017 T2/cm2 • 1010-decay electrons / s Forward going electrons: Rear-going electrons: absorbed here Cryogenic pumping to prevent gas from entering spectrometer Mechanical pumpingto close T2 loop

31. Transport and differential & cryo pumping sections Differentialpumping Cryogenic pumping for diagnostics: FTICR trap K. Blaum et al. max 2.5 10-14 mbar l/s requirements: • adiabatic electron guiding • T2 reduction factor of ~1014

32. Tritium Source • Tritium is an ideal -emitter: • Low endpoint energy E0 = 18.6 keV • (second lowest -decay endpoint) • Relatively short half-life t1/2 = 12.3 y • Simple molecular structures • precise calculations available • Super-allowed nuclear transition (allowed spectrum shape)

33. MAC-E-Filter Magnetic Adiabatic Collimation with an Electrostatic Filter (A. Picard et al., Nucl. Instr. Meth. 63 (1992) 345) Magnetic Adiabatic Collimation •  = E/B is adiabatically invariant for slow magnetic field variation • Bmin << Bmax converts cyclotron motion into longitudinal motion (E E||) Electrostatic Filter • Electrodes provide potential barrier, acting as integrating high-pass filter • Electrons will pass if E|| > qU High resolution: • E/E = Bmin/Bmax Size and shape determined by Conservation of Magnetic Flux:

34. Backgrounds Limit: 10 mHz total Detector Backgrounds • Natural Radioactivity 238U, 232Th • Cosmic Rays • Cosmogenics Limit to 1 mHz in Region of Interest Spectrometer Backgrounds • Electrons produced in analyzing volume of spectrometer mimic -electron signal Signal Detector Background Spectrometer Background Electrons can be post-accelerated by up to 30 keV

35. Institutions in KATRIN