katrin - the ka rlsruhe tri tium n eutrino experiment

KATRIN - KATRIN -

The The KaKarlsruhe rlsruhe TriTritium tium NNeutrino Experimenteutrino Experiment

H.H. Telle

Department of Physics, University of Wales SwanseaSingleton Park, Swansea SA2 8PP

HHT – UK HEP “Dark Matter” (15/05/05) 1

What is KATRINWhat is KATRIN


The KATRIN experiment is designed to measure the mass of

the electron neutrino directly with a sensitivity of 0.2 eV.

It is a next generation tritium beta-decay experiment scaling

up the size and precision of previous experiments by an order

of magnitude as well as the intensity of the tritium beta

source.

10 m

http://www-ik.fzk.de/katrin/motivation/sensitivity.html

Who and WhereWho and Where


KATRIN is a joint effort of several European and U.S.

institutions.

Currently there are about 100 scientists, engineers,

technicians and students involved, including most of the

groups that have worked on tritium beta-decay experiments in

recent years.

KATRIN is being built at Forschungszentrum Karlsruhe in

Germany where much of the required technical infra-structure

is already available, especially for the tritium source.

The locationThe location


WhyWhy


The widely-used Standard Model (SM) of particle physics

originally assumed neutrinos to be mass-less.

However, actual investigations of neutrinos from the sun and of

neutrinos created in the atmosphere by cosmic rays have given

strong evidence for massive neutrinos indicated by neutrino

oscillations.

Neutrino oscillations imply that a neutrino from one specific

weak interaction flavour, e.g. a muon neutrino νµ, transforms

into another weak flavour eigenstate, i.e. an electron neutrino νe

or a tau neutrino ντ , while travelling from the source to the

detector.

Neutrino mass determination methodsNeutrino mass determination methods


Neutrino mass: a source for “hot” dark matter (HDM)Neutrino mass: a source for “hot” dark matter (HDM)


The contribution Ων from neutrino HDM to the total matter energy density Ω of the universe spans two orders of magnitude. The lower bound on Ων comes from the analysis of oscillations of atmospheric ν’s. The upper bound stems from current tritium β-decay experiments and studies of structure formation.

The experimentThe experiment


Overview of KATRIN set-upOverview of KATRIN set-up


1 2 3 4 5

scale

Overview of the KATRIN setup. The electron path is from left to

right. To minimise background, an ultra high vacuum of better than

10-11 mbar is necessary.

1 – the source1 – the source


T2 injection

2 – the transport section2 – the transport section


The electron transport

system adiabatically guides

beta decay electrons from

the tritium source to the

spectrometer, while at the

same time eliminating any

tritium flow towards the

spectrometer, which has to

be kept practically free of

tritium for background and

safety reasons.

3 – the pre-spectrometer3 – the pre-spectrometer


Between the tritium sources and the main spectrometer a pre-

spectrometer of MAC-E-Filter type will be inserted, acting as

energy pre-filter to reject all β electrons except the ones in the

region of interest close to the endpoint E0.

The MAC-E filterThe MAC-E filter


MAC-E-Filter = Magnetic Adiabatic Collimation combined

with an Electrostatic Filter

Varying the electrostatic

retarding potential allows

to measure the beta

spectrum in an integrating

mode.

The hardware status of the pre-spectrometerThe hardware status of the pre-spectrometer


4 – the main spectrometer (1)4 – the main spectrometer (1)


A key component of the new experiment will be the large

electrostatic spectrometer with a diameter of 10m and an

overall length of about 23m.

This high resolution MAC-E-Filter will allow to scan the tritium

endpoint with increased luminosity at a resolution of < 1eV,

which is a factor of 4 better than present MAC-E Filters.

4 – the main spectrometer (2)4 – the main spectrometer (2)


5 – the detector (1)5 – the detector (1)


All β particles passing the retarding potential of the MAC-E-

Filter will be guided by a magnetic transport system to the

detector.

The detector requirements are the following:

high efficiency for e-detection and simultaneously low

background,

energy resolution of ΔE < 600 eV for 18.6 keV electrons to

suppress background events at different energies,

operation at high magnetic fields,

5 – the detector (2)5 – the detector (2)


position resolution to map the source profile, to localize

the particle track within the spectrometer (for compensation of

inhomogeneities of electric potential and magnetic field in the

analyzing plane), and to suppress background originating

outside the interesting magnetic flux (e.g. coming from the

electrodes of the spectrometer),

for a measurement in a MAC-E-TOF mode, a reasonable

time resolution < 100 ns),

for test and calibration measurements ready to take high

count rates (up to total rate of order 1 MHz)

Time scheduleTime schedule


Numerous parts have been delivered and are under test

All major components (source and main spectrometer) have

been ordered

Work on new buildings commenced

Full commissioning and test of whole assembly in late 2007

Start of measurements: 2008

Duration of measurements: 3-5 years

CostsCosts


Capital investment – about € 32 M

(mostly provided by the Helmholtz Gesellschaft and the

German Federal Government)

Operating costs from 2007/8 onwards – about € 1.5 M p.a.

(to be shared by the participating countries)

The scientific contribution from the UKThe scientific contribution from the UK


Swansea

Development of a monitoring system for T2 purity

Calculation of trajectory distortion of -particles from

space charge and electrode edges

University College London

Calculation of final molecular state distributions in the

WGTS

CCLRC Daresbury

expertise in XUHV

Requirements for TRequirements for T22 analysis analysis


KATRIN requires T2 gas of high (>95%) purity.

Impurities include the other hydrogen isotopomers (H2, HT,

D2, DH, DT) and possibly small amounts of methane

isotopes CHxRy (R=H,D,T) from chemical reactions.

In the long-term, knowledge of the T2 purity to within ±0.1%

is needed, with Raman spectroscopy providing quantitative

information about the impurities.

Measurements of impurities to be done at the inlet* to the T2

source at a total pressure of ~10mbar

* Identified as the most convenient location for continuous

in-line analysis

Principles of Raman spectroscopyPrinciples of Raman spectroscopy


v=0

v=1

excited state

J

J

0

0

1

1

2

2

Vibrational states: v=0,1,2,3…

Rotational states: J=0,1,2,3…

Laser excites the molecule to an excited state which scatters:

either

to the same initial vibrational state, with J = 0,+2

or

to a higher vibrational state, with J = 0, ±2

las

er

ro

t

ro

-vib

Raman spectroscopy of HRaman spectroscopy of H22


~550,000

rotational ro-vibrational

S0 O1 Q1 S1

H2

Proposed experimental set-up at FZKProposed experimental set-up at FZK


WGTS

Monitoring Gas Cell

By-Pass

180cm

120cm

Area Allocated To

Raman Monitoring

T2 safety enclosure

Experimental set-up for realisation of HExperimental set-up for realisation of H22 / D / D22 / T / T22 Raman Raman


The test set-up for HThe test set-up for H22 / D / D22 Raman Raman


Test – Raman of ambient air (8mW laser)Test – Raman of ambient air (8mW laser)


Test – Raman of DTest – Raman of D2 2 (8mW laser)(8mW laser)


S1(Q) D2

S1(

Q)

N2

S1(

Q)

O2

S0(S) D2

Nd

:YA

G

Test – Raman of HTest – Raman of H22+D+D2 2 mixture (8mW laser)mixture (8mW laser)


Not yet sufficient resolution to follow rotational population of all isotopomers

Estimates for estimated Raman sensitivitiesEstimates for estimated Raman sensitivities


The remit of KATRINThe remit of KATRIN


KATRIN is expected to achieve the following sensitivities for the mass of the electron neutrino:

Sensitivity:

(90% upper limit if neutrino mass is zero)0.2 eV

with about equal contributions of statistical and systematical errors.

Discovery potential:

A neutrino mass of 0.35 eV would be discovered with 5 sigma significance.A neutrino mass of 0.30 eV would be discovered with 3 sigma significance.

Accuracy on mAccuracy on mνν22 for 3-year data taking (calculation -1) for 3-year data taking (calculation -1)


.

Accuracy on mAccuracy on mνν22 for 3-year data taking (calculation-2) for 3-year data taking (calculation-2)


.

Systematic uncertainties are expected to amount to an equal size as the statistical errors after a measuring time of 3 full years, using an analyzing interval of 30 eV below the endpoint. These are especially:

• Time variation of parameters of the Windowless Gaseous Tritium Source (WGTS),

• description of space charging within the WGTS,

• determination of scattering probabilities of β-electrons within the WGTS,

• description of the final state distribution of (3HeT)+ ions after tritium decay,

• variations of the retarding potential,

• and the limited uniformity of the magnetic and electrostatic fields in the spectrometer analyzing plane.

Summary of expectation from KATRINSummary of expectation from KATRIN


originally

now

katrin - the ka rlsruhe tri tium n eutrino experiment

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