ArticlePDF Available

Status of the KATRIN experiment


Abstract and Figures

The aim of the Karlsruhe Tritium Neutrino experiment-KATRIN-is the direct measurement of the anti-neutrino mass with a sensitivity of 200 meV/c 2 (90% C.L.). It is based on the study of the endpoint region of tritium β decay where a non-vanishing anti-neutrino mass causes a distortion of the β spectrum. KATRIN will allow to probe a part of the cosmology-relevant neutrino mass parameter space and hence further constrain cosmological models and help to clarify the role of neutrinos as dark matter. KATRIN uses a windowless gaseous tritium source for production of β electrons in combination with an electrostatic filter for energy analysis. An overview of the status of the KATRIN experiment will be given.
Content may be subject to copyright.
Status of the KATRIN experiment
Sebastian Fischer
Karlsruhe Institute of Technology, Germany
The aim of the Karlsruhe Tritium Neutrino experiment - KATRIN - is the direct measurement of
the anti-neutrino mass with a sensitivity of 200 meV/c2(90% C.L.). It is based on the study of the
endpoint region of tritium βdecay where a non-vanishing anti-neutrino mass causes a distortion
of the βspectrum. KATRIN will allow to probe a part of the cosmology-relevant neutrino mass
parameter space and hence further constrain cosmological models and help to clarify the role of
neutrinos as dark matter. KATRIN uses a windowless gaseous tritium source for production of β
electrons in combination with an electrostatic filter for energy analysis.
An overview of the status of the KATRIN experiment will be given.
The 2011 Europhysics Conference on High Energy Physics-HEP 2011,
July 21-27, 2011
Grenoble, Rhône-Alpes France
for the KATRIN collaboration
Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Status of the KATRIN experiment Sebastian Fischer
1. Introduction
Cosmological observations and the detection of neutrino flavour oscillations have shown that
neutrinos are massive particles. Although the mass splittings between the neutrino mass eigenstates
are known to be |m312|= (2.32+0.12
0.08)×103eV2/c4[1] and m21 2= (7.41+0.21
0.19 )×105eV2/c4
[2], the overall mass scale is still unknown. A complementary approach is the study of the endpoint
region of tritium βdecay 3H3He +e+¯
νewhere a non-zero anti-neutrino mass mνcauses a
distortion of the βspectrum
dE dt p(E+mec2)(E0E)q(E0E)2m2
νc4with mν=
|Uei |2mi2
This measurement allows a direct and model-independent determination of mνand based on the
results of the Mainz [4] and Troitsk [5] experiments an upper limit of 2 eV/c2(95 % C.L.) can be
deduced [6]. The aim of the KArlsruhe TRItium Neutrino (KATRIN) experiment is the measure-
ment of mνwith 200 meV/c2design sensitivity (90% C.L.) [3]. By improving the sensitivity by
one order of magnitude in comparison to foregoing experiments, KATRIN will probe a cosmology-
relevant part of the neutrino mass parameter space.
2. The KATRIN experiment: Principle and status of the main components
The KATRIN experiment consists of four main sections (figure 1): The windowless gaseous
tritium source (1) in which the βelectrons are produced. The transport section (2) which reduces
the tritium flow rate by 14 orders of magnitude and adiabatically guides the electrons to the spec-
trometer and detector section (3) where the energy analysis is performed. The calibration and
monitoring system (4) monitors the activity of the WGTS and performs systematic studies. An
overview of the status of these main sections will be given in the following.
2.1 Status of the windowless gaseous tritium source
The main parameters of the windowless gaseous tritium source (WGTS), i.e. the source tem-
perature, the gas inlet and outlet flow rate and the isotopic composition of the inlet gas, have to
be stabilized to the 103level and accordingly monitored in order to reach the design sensitivity
of 200 meV/c2. The test experiment Demonstrator has proven that cooling concept of the WGTS
WGTS Cryostat Calibration
DPS2-F CPS Main Spectrometer Detector
Transport Section Spectrometer and detector section
Figure 1: Overview of the KATRIN experiment. The tritium loop system of the WGTS are not shown. For
further details see main text.
Status of the KATRIN experiment Sebastian Fischer
cryostat can achieve a temperature stabilization of the 30 K beam tube in the mK range (Require-
ment: 30 mK stability). After completing the tests, the Demonstrator will be upgraded to the final
WGTS by installing the tritium related parts and the magnets for electron guiding.
The precise knowledge of the composition of the tritium inlet gas of the WGTS is necessary to
account for systematic effects in the WGTS, e.g. Doppler broadening, elastic scattering, nuclear re-
coil and the final state distribution of the (3HeT)+daughter molecules. Laser Raman spectroscopy
(LARA) is the method of choice for the monitoring of the gas composition in KATRIN since it
allows the simultaneous monitoring of all hydrogen isotopologues (T2, DT, HT, D2, HD, H2) [7].
Laser Raman spectroscopy is based on Raman scattering, i.e. the inelastic scattering of photons
on molecules. In this process the wavelength of the scattered light changes due to the rotational-
vibrational (de-)excitation of the molecule which produces characteristic spectra for each hydrogen
isotopologue. As an optical method, Raman spectroscopy is non-invasive, i.e. no samples have to
be taken and hence no radioactive waste is produced.
The test of the LARA system in the closed tritium loop LOOPINO during 3 weeks of non-stop
operation showed that the required 0.1% precision is achieved under KATRIN-like conditions [8].
Further improvement of precision due to an optimisation of the laser beam path and the read-out
mechanism of the optical detector are expected. Experimental tests of calculated Raman scattering
cross-sections of all hydrogen isotopologues were made to improve the accuracy of the LARA
2.2 Status of the transport section
The transport section consists of the differential pumping sections (DPS1-F and DPS2-F) and
the cryogenic pumping section (CPS). After commissioning of the DPS2-F, the gas reduction factor
has been measured for D2, He and other noble gases at room temperature. The measured reduction
factors vary between (1.86 ±0.37)×104(for D2) and (5.6±1.1)×104(for Kr) [9]. A further
improvement of the gas reduction factor is expected when the complete beam tube instrumentation
of the DPS2-F is installed. The manufacturing of the CPS is ongoing and the delivery to KIT is
expected for 2012.
2.3 Status of the spectrometer and detector section
Two electrostatic filters, based on the MAC-E [10] principle, are used for energy analysis:
The pre-spectrometer will reject most of the electrons which have energies less than about 300 eV
below the endpoint, i.e. which do not contain information on the anti-neutrino mass. The retarding
potential of the main spectrometer will be varied to measure the spectrum in the last 30 eV below
the endpoint. The pre-spectrometer has been operated as a prototype for systematic investigations
and hardware developments which are also relevant for the main spectrometer. A radon induced
background signal, emerging from the material of vacuum getter strips, has been identified and
suitable experimental measures for suppression were found [11]. The test operation of the pre-
spectrometer is finished and it is ready for its final integration into the KATRIN setup.
The installation of the wire frame modules [12] in the main spectrometer, which are used for
reduction of muon induced electron background, is completed. The detector system has arrived
in Karlsruhe in summer 2011 and has been commissioned. The commissioning and first measure-
ments of the main spectrometer are scheduled for 2012.
Status of the KATRIN experiment Sebastian Fischer
2.4 Status of the calibration and monitoring system
The feasibility of source activity monitoring using βinduced X-ray spectroscopy has been
successfully demonstrated at Tritium Laboratory Karlsruhe. A technical design of the calibration
and monitoring section has been developed.
3. Conclusions
Test measurements of several main components of KATRIN have been successfully performed
and important milestones were achieved. The LARA system has reached 0.1% precision (1σ) under
KATRIN-like conditions and further imrovements are expected. With the upcoming measurements
at the main spectrometer in 2012 the commssioning of KATRIN main components will continue.
[1] P. Adamson et al., Measurement of the Neutrino Mass Splitting and Flavor Mixing by MINOS, Phys.
Rev. Lett. 106, 181801 (2011), doi:10.1103/PhysRevLett.106.181801.
[2] B. Aharmim et al., Combined Analysis of all Three Phases of Solar Neutrino Data from the Sudbury
Neutrino Observatory, arXiv:1109.0763v1 [nucl-ex] (2011).
[3] KATRIN Collaboration, KATRIN Design Report 2004, FZKA 7090 (2005).
[4] Ch. Kraus et al., Final Results from phase II of the Mainz Neutrino Mass Search in Tritium βDecay,
Eur. Phys. J. C 40 (2005) 447-468.
[5] V.M. Lobashev et al., Direct search for mass of neutrino and anomaly in the tritium beta-spectrum,
Phys. Lett. B 460 (1999) 227-235.
[6] C. Amsler et al. (Particle Data Group), Review of Particle Physics, Phys. Lett. B 667 (2008) and 2009
partial update for the 2010 edition.
[7] M. Sturm et al., Monitoring of All Hydrogen Isotopologues at Tritium Laboratory Karlsruhe Using
Raman Spectroscopy, Laser Phys. 20 2 (2010).
[8] S. Fischer et al., Monitoring of tritium purity during long-term circulation in the KATRIN test
experiment LOOPINO using laser Raman spectroscopy, Fusion Sci. Technol. 60 3 (2011) 925-930.
[9] S. Lukic et al., Measurement of the gas-flow reduction factor of the KATRIN DPS2-F differential
pumping section, arXiv:1107.0220v1 [physics.ins-det] (2011).
[10] P. Kruit, F. H. Read, Magnetic field paralleliser for 2πelectron-spectrometer and electron-image
magnifier, J. Phys. E: Sci. Instrum. 16 313 (1983).
[11] F.M. Fränkle et al., Radon induced background processes in the KATRIN pre-spectrometer, Astropart.
Phys. 35 3 (2011) 128-134doi:10.1016/j.astropartphys.2011.06.009.
[12] K. Valerius, The wire electrode system for the KATRIN main spectrometer, Progress in Particle and
Nuclear Physics 64 2 291-293 (2010) doi:10.1016/j.ppnp.2009.12.032.
... The KArlsruhe TRitium Neutrino mass experiment (KATRIN) will have a sensitivity on the electron neutrino effective mass, m β = i |U ei | 2 m 2 i , of 0.2 eV at 95% CL [42]. Cosmological limits today still allow for quasi-degenerate neutrino masses; however, this possibility will soon be confirmed or ruled out. ...
... The region allowed by the normal (inverted) mass ordering is in blue (red), the recent limit on |m ee | given by KamLAND-Zen [39] in gray and the region excluded by cosmology [41] in magenta. We also show the reach expected for the beta decay experiment Katrin [42], as well as the ultimate reach aimed by the neutrinoless double beta decay experiments GERDA and CUORE according to ref. [40]. ...
... The region allowed by the normal (inverted) mass ordering is in blue (red), and the recent limit on |m ee | given by KamLAND-Zen [39] in gray. We also show the reach expected for the beta decay experiment Katrin [42], as well as the ultimate reach aimed by the neutrinoless double beta decay experiments GERDA and CUORE according to ref. [40]. ...
Full-text available
A bstract We analyze the neutrino mass matrix entries and their correlations in a probabilistic fashion, constructing probability distribution functions using the latest results from neutrino oscillation fits. Two cases are considered: the standard three neutrino scenario as well as the inclusion of a new sterile neutrino that potentially explains the reactor and gallium anomalies. We discuss the current limits and future perspectives on the mass matrix elements that can be useful for model building.
Full-text available
This is a review paper about neutrino mass and mixing and flavour model building strategies based on discrete family symmetry. After a pedagogical introduction and overview of the whole of neutrino physics, we focus on the PMNS mixing matrix and the latest global fits following the Daya Bay and RENO experiments which measure the reactor angle. We then describe the simple bimaximal, tri-bimaximal and golden ratio patterns of lepton mixing and the deviations required for a non-zero reactor angle, with solar or atmospheric mixing sum rules resulting from charged lepton corrections or residual trimaximal mixing. The different types of see-saw mechanism are then reviewed as well as the sequential dominance mechanism. We then give a mini-review of finite group theory, which may be used as a discrete family symmetry broken by flavons either completely, or with different subgroups preserved in the neutrino and charged lepton sectors. These two approaches are then reviewed in detail in separate chapters including mechanisms for flavon vacuum alignment and different model building strategies that have been proposed to generate the reactor angle. We then briefly review grand unified theories (GUTs) and how they may be combined with discrete family symmetry to describe all quark and lepton masses and mixing. Finally, we discuss three model examples which combine an SU(5) GUT with the discrete family symmetries A4, S4 and Δ(96).
Full-text available
The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT4-nX n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium ß decay. A precision of 0.1% was achieved for the monitoring of the T2 Q1-branch, which fulfils the requirements for the KATRIN experiment and demonstrates the feasibility of high-precision Raman measurements with tritium inside a glove box. Compositional changes; Deuterated methanes; ; Gas-wall interactions; Gloveboxes; High-precision; Hydrogen isotope exchange reaction; Inner loops; Laser Raman spectroscopy; Measurement cell; Raman measurements; Total pressure; Tritium Laboratory Karlsruhe
Full-text available
We report results from a combined analysis of solar neutrino data from all phases of the Sudbury Neutrino Observatory. By exploiting particle identification information obtained from the proportional counters installed during the third phase, this analysis improved background rejection in that phase of the experiment. The combined analysis resulted in a total flux of active neutrino flavors from 8B decays in the Sun of (5.25 \pm 0.16(stat.)+0.11-0.13(syst.))\times10^6 cm^{-2}s^{-1}. A two-flavor neutrino oscillation analysis yielded \Deltam^2_{21} = (5.6^{+1.9}_{-1.4})\times10^{-5} eV^2 and tan^2{\theta}_{12}= 0.427^{+0.033}_{-0.029}. A three-flavor neutrino oscillation analysis combining this result with results of all other solar neutrino experiments and the KamLAND experiment yielded \Deltam^2_{21} = (7.41^{+0.21}_{-0.19})\times10^{-5} eV^2, tan^2{\theta}_{12} = 0.446^{+0.030}_{-0.029}, and sin^2{\theta}_{13} = (2.5^{+1.8}_{-1.5})\times10^{-2}. This implied an upper bound of sin^2{\theta}_{13} < 0.053 at the 95% confidence level (C.L.).
Full-text available
Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively.
An electron-optical device has been constructed in which electrons originally emitted over 2 pi steradians from a region of small volume are formed into a beam of half-angle 2 degrees . The instrument makes use of a magnetic field that diverges from 1 to 10-3 Tesla. The energies of the electrons parallelised in this way have been measured with a time-of-flight technique, giving energy resolutions as low as 15 meV. Electrons of energy 0-3 eV, formed in multiphoton ionisation, were used for these tests. The device can also act as an electron-image magnifier, giving a spatial resolution of a few mu m in the source plane. Detailed theoretical and computational results on the properties of the new apparatus are given.
We have recorded Raman spectra for all hydrogen isotopologues, using a CW Nd:YVO4 laser (5 W output power at 532 nm) and a high-throughput (f/1.8) spectrograph coupled to a Peltier-cooled (200 K) CCD-array detector (512 × 2048 pixels). A (static) gas cell was used in all measurements. We investigated (i) “pure” fillings of the homonuclear isotopologues H2, D2, and T2; (ii) equilibrated binary fillings of H2 + D2, H2 + T2, and D2 + T2, thus providing the heteronuclear isotopologues HD, HT, and DT in a controlled manner; and (iii) general mixtures containing all isotopologues at varying concentration levels. Cell fillings within the total pressure range 13–985 mbar were studied, in order to determine the dynamic range of the Raman system and the detection limits for all isotopologues. Spectra were recorded for an accumulation period of 1000 s. The preliminary data evaluation was based on simple peak-height analysis of the ro-vibrational Q1-branches, yielding 3σ measurement sensitivities of 5 × 10−3, 7 × 10−3, and 25 × 10−3 mbar for the tritium-containing isotopologues T2, DT, and HT, respectively. These three isotopologues are the relevant ones for the KATRIN experiment and in the ITER fusion fuel cycle. While the measurement reported here were carried out with static-gas fillings, the cells are also ready for use with flowing-gas samples.
Aims. KATRIN is a neutrino mass experiment based on the kinematics of tritium β-decay. This work presents the methods employed at KATRIN to reduce the spectrometer-related background.Methods. The electrode system of the main spectrometer includes a modular double-layer wire grid for electrostatic screening of background. The key features of the wire electrode and the underlying design criteria of the optimisation procedure are described.Status. Fabrication of the wire electrode modules is completed and installation into the KATRIN main spectrometer has started.
Results of the “Troitsk ν-mass” experiment on the search for the neutrino rest mass in the tritium beta-decay are presented. Study of time dependence of anomalous, bump-like structure at the end of beta spectrum reported earlier gives indication of periodic shift of the position of the bump with respect to the end-point energy with a period of 0.5 year. A new upper limit for electron antineutrino rest mass mν<2.5 eV/c2 95% C.L. is derived after accounting for the bump.
The gas-flow reduction factor of the second forward Differential Pumping Section (DPS2-F) for the KATRIN experiment was determined using a dedicated vacuum-measurement setup and by detailed molecular-flow simulation of the DPS2-F beam tube and of the measurement apparatus. In the measurement, non-radioactive test gases deuterium, helium, neon, argon and krypton were used, the input gas flow was provided by a commercial mass-flow controller, and the output flow was measured using a residual gas analyzer, in order to distinguish it from the outgassing background. The measured reduction factor with the empty beam tube at room temperature for gases with mass 4 is 1.8(4)E4, which is in excellent agreement with the simulated value of 1.6E4. The simulated reduction factor for tritium, based on the interpolated value for the capture factor at the turbo-molecular pump inlet flange is 2.5E4. The difference with respect to the design value of 1E5 is due to the modifications in the beam tube geometry since the initial design, and can be partly recovered by reduction of the effective beam tube diameter.