Direct Neutrino Mass Measurements 5 th International Symposium on - PowerPoint PPT Presentation

Direct Neutrino Mass Measurements 5 th International Symposium on Symmetries in Subatomic Physics, Groningen, June 17-22, 2012 Christian Weinheimer Institut für Kernphysik, Westfälische Wilhelms-Universität Münster weinheimer@uni-muenster.de Introduction ● The KArlsruhe TRItium Neutrino experiment KATRIN ● Other direct neutrino mass approaches ● Summary ● Photo: M. Zacher Christian Weinheimer SSP 2012, Groningen, June 21, 2012 1

Hot Dark Matter: neutrinos Their contribution depends on m ν Results of recent oscillation experiments: Θ 23 , Θ 12 , Θ 13 , Δ m 2 23 , Δ m 2 12 ν e ν µ ν τ ν 1 ν 2 ν 3 Relics from the hot plasma after the big bang (like CMB): 336 ν / cm 3 Ω 1 degenerated masses 0.1 cosmological relevant e.g. seesaw mechanism type 2 0.01 hierarchical masses Δ m 2 0.001 23 e.g. seesaw mechanism type 1 explains smallness of masses, Δ m 2 but not mixing 12 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 2

Three complementary ways to the absolute neutrino mass scale 1) Cosmology very sensitive, but model dependent compares power at different scales current sensitivity: Σ m( ν i )  0.5 eV e.g. S. Hannestad, Prog. Part. Nucl. Phys. 65 (2010) 185 Search for 0 νββ 2) Sensitive to Majorana neutrinos Evidence for m ee ( ν )  0.3 eV ? GERDA is running, EXO delivered 1 st limit ! m ββ ( ν ) = | Σ |U ei 2 | e i α (i) m( ν i )| 3) Direct neutrino mass determination: No further assumptions needed. no model dependence use E 2 = p 2 c 2 + m 2 c 4  m 2 ( ν ) is observable mostly most sensitive methode: endpoint spectrum of β -decay m 2 ( ν e ) = Σ |U ei 2 | m 2 ( ν i ) Christian Weinheimer SSP 2012, Groningen, June 21, 2012 3

Direct determination of m( ν e ) from β decay  (A,Z+1) + + e- + ν e β decay: (A,Z) Complementary to 0 νββ Complementary to 0 νββ and cosmology β electron energy spectrum: and cosmology dN/dE = K F(E,Z) p E tot (E 0 -E e ) Σ |U ei | 2  (E 0 -E e ) 2 – m( ν i ) 2 (modified by electronic final states, recoil corrections, radiative corrections) averaged neutrino mass Review: Review: E.W. Otten & C. Weinheimer E.W. Otten & C. Weinheimer Rep. Prog. Phys., 71 (2008) 086201 Rep. Prog. Phys., 71 (2008) 086201 Need: low endpoint energy  Tritium 3 H, ( 187 Re) very high energy resolution & very high luminosity &  MAC-E-Filter very low background (or bolometer for 187 Re) Christian Weinheimer SSP 2012, Groningen, June 21, 2012 4

Tritium experiments: source  spectrometer MAC-E-Filter ● Two supercond. solenoids compose magnetic guiding field ● adiabatic transformation: µ = E/B = const.  parallel e - beam ● Energy analysis by electrostat. retarding field Δ E = EB min /B max = 0.93 eV (KATRIN)  sharp integrating transmission function without tails  Magnetic Adiabatic Collimation + Electrostatic Filter (A. Picard et al., Nucl. Instr. Meth. 63 (1992) 345) Christian Weinheimer SSP 2012, Groningen, June 21, 2012 5

The Mainz Neutrino Mass Experiment Phase 2: 1997-2001 ⇓ After all critical systematics measured by own experiment (atomic physics, surface and solid state physics: inelastic scattering, self-charging, neighbour excitation): m 2 ( ν ) = -0.6 ± 2.2 ± 2.1 eV 2  m( ν ) < 2.3 eV (95% C.L.) C. Kraus et al., Eur. Phys. J. C 40 (2005) 447 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 6

The Troitsk Neutrino Mass Experiment windowless gaseous T 2 source, similar to LANL MAC-E-Filter, similar to Mainz Vladimir Mikhailovich Lobashev Δ E = 3.5eV Energy resolution: Luminosity: L = 0.6cm 2 1934-2011 3 electrode system in 1.5m (L = ΔΩ /2 π * A source ) diameter UHV vessel (p<10 -9 mbar) Re-analysis of Troitsk data (better source thickness, better run selection) Aseev et al, Phys. Rev. D 84, 112003 (2011) m β < 2.2 eV, 95% CL Christian Weinheimer SSP 2012, Groningen, June 21, 2012 7

The KATRIN experiment at KIT Aim: m( ν e ) sensitivity of 200 meV (currently 2 eV) ● very high energy resolution ( Δ E  1eV, i.e. σ = 0.3 eV)  source  spectrometer concept ● strong, opaque source  dN/dt ~ A source ● magnetic flux conservation (Liouville)  scaling law: A spectrometer / A source = B source / B spectrometer = E / Δ E = 20000 / 1 detector KATRIN Design Report 70 m main spectrometer Scientific Report FZKA 7090) pre tritium spectro- retention meter windowless gaseous 10m system molecular tritium source Christian Weinheimer SSP 2012, Groningen, June 21, 2012 8

Molecular Windowless Gaseous Tritium Source WGTS T 2 WGTS: tub in long superconducting solenoids  9cm, length: 10m, T = 30 K Tritium recirculation (and purification) p inj = 0.003 mbar, q inj = 4.7Ci/s allows to measure with near to maximum count rate using ρ d = 5  10 17 /cm 2 with small systematics check column density by e-gun, T 2 purity by laser Raman Christian Weinheimer SSP 2012, Groningen, June 21, 2012 9

Very successful cool-down and stability tests of the WGTS demonstrator cooling concept of WGTS: beam tube pressurized 2-phase Ne Ø=90mm arrival of WGTS demonstrator at KIT: April 2010 p r e l i m i n a r y S. Grohmann, S. Grohmann, Cryogenics 49, Cryogenics 49, No. 8 (2009) 413 No. 8 (2009) 413 Currently: tests of sc magnets, constructing of WGTS out of demonstrator Christian Weinheimer SSP 2012, Groningen, June 21, 2012 10

Transport and differential & cryo pumping sections Cryogenic Differential Molecular windowless pumping pumping gaseous tritium source with Argon snow at LHe temperatures (successfully tested with the TRAP experiment)  10 -7 mbar l/s FT-ICR Penning traps to FT-ICR Penning traps to T 2 -injection 1.8 mbar l/s (STP) measure ions from WGTS measure ions from WGTS = 1.7*10 11 Bq/s = 40 g/d < 2.5 10 -14 mbar l/s  adiabatic electron guiding & T 2 reduction factor of ~10 14 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 11

Commissioning of DPS2-F Ion test source: Ion test source: S. Lukic et al., S. Lukic et al., Rev. Scient. Instr. Rev. Scient. Instr. 82 (2011) 013303 82 (2011) 013303 FT-ICR Penning traps: FT-ICR Penning traps: M. Ubieto-Diaz et al., M. Ubieto-Diaz et al., Int. J. Mass. Spectrom. Int. J. Mass. Spectrom. 288 (2009) 1-5 288 (2009) 1-5 gas inlet outgoing gas flow ≈ 3 × 10 17 ≈ 3 × 10 12 molecules/s molecules/s First gas flow reduction measurements with Ar Currently: Problem of a broken diode S. Lukic et al., from the safety system Vacuum 86 (2012) 1126 of a superconducting coil Christian Weinheimer SSP 2012, Groningen, June 21, 2012 12

Electromagnetic design: magnetic fields B-field [T] 1:20000  Δ E = E  B min / B max = E  1 / 20000 = 0.93 eV -40 -30 -20 -10 0 +10 aircoils: distance from analysing plane [m] axial field shaping + earth field compensatio n Christian Weinheimer SSP 2012, Groningen, June 21, 2012 13

The detector Requirements VACUUM, CALIBRATION SYSTEM ● detection of β -electrons (mHz to kHz) ● high efficiency (> 90%) ● low background (< 1 mHz) ELECTRONICS (passive and active shielding) DETECTOR PINCH MAGNET DETECTOR ● good energy resolution (< 1 keV) MAGNET Properties electrons    ● 90 mm Ø Si PIN diode SUPPORT STRUCTURE ● thin entry window (50nm) ● detector magnet 3 - 6 T ● post acceleration (30kV) (to lower background in signal region) ● segmented wafer (145 pixels) → record azimuthal and radial profile of the flux tube → investigate systematic effects → compensate field inhomogeneities Christian Weinheimer SSP 2012, Groningen, June 21, 2012 14

KATRIN detector is being commissioned at KIT Christian Weinheimer SSP 2012, Groningen, June 21, 2012 15

Main Spectrometer – Transport to Karlsruhe Institute of Technology 8800 km Leopoldshafen, 25.11.06 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 16

KATRIN has a 100-times larger surface, but requests same bg → something new e - Secondary electrons from wall/electrode  µ  by cosmic rays, environmental radioactivity, ...  New: wire electrode on slightly more negative potential  γ    U- Δ U U Mainz V (2004) Mainz 2001-2004 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 17

Design, construction and mounting of the 690m 2 2-layer wire electrode system Requirements: - 200 µ m precision - out-bakeable 350 o C - 10 -11 mbar compatiible - 1 kV difference voltage - non magnetic - ... Foto: Peter Lessmann Christian Weinheimer SSP 2012, Groningen, June 21, 2012 18

Two-layer wire electrode modules installation inside main spectrometer All 248 modules are installed, January 31, 2012 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 19

Background from stored electrons: methods to avoid or to eliminate them Radon suppression by LN 2 cooled baffle Stored electron by magnetic mirrors F. Fränkle et al., Astropart. Phys. 35 (2011) 128 Nulling magnetic field by magn. pulse radial E x B drift due to electric dipole pulse Mechanical eliminating stored particles: M. Beck et al, Eur. Phys. J. A44 (2010) 499 Christian Weinheimer SSP 2012, Groningen, June 21, 2012 20