Ellinger, E.

Haußmann, N.

Helbing, K.

Hickford, S.

Klein, M.

Naumann, U.

Journal of Physics Conference Series

English

E. Ellinger

N. Haußmann

K. Helbing

S. Hickford

M. Klein

U. Naumann

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Monitoring the KATRIN source properties within the beamline

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Journal of Physics: Conference SeriesPAPER • OPEN ACCESSMonitoring the KATRIN source properties withinthe beamlineTo cite this article: E. Ellinger et al 2017 J. Phys.: Conf. Ser. 888 012229 View the article online for updates and enhancements.Related contentKATRIN: an experiment to determine theneutrino massR G H Robertson-Results of the first Cool-down of theKATRIN Cryogenic Pumping SectionCarsten Röttele-Measurements with the KATRIN pre-spectrometerF Habermehl and the KATRINCollaboration-This content was downloaded from IP address 129.13.72.197 on 15/01/2018 at 14:201Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd1234567890Neutrino2016 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 888 (2017) 012229  doi :10.1088/1742-6596/888/1/012229Monitoring the KATRIN source properties withinthe beamlineE. Ellinger1, N. Haußmann1, K. Helbing1, S. Hickford1, M. Klein2,and U. Naumann11 University of Wuppertal2 Karlsruhe Institute of TechnologyE-mail: ellinger@uni-wuppertal.deAbstract. The KArlsruhe TRItium Neutrino (KATRIN) experiment will measure the massof the neutrino with a sensitivity of 0.2 eV (90% CL). The Forward Beam Monitor (FBM)is a monitoring system which comprises of a complex mechanical setup capable of insertinga detector board into the KATRIN beamline at the end of the source and transport section.The detector board contains a Hall sensor, a temperature gauge, and two PIN diodes whichcan detect electrons from the source with a precision of 0.1% in less than a minute within anelectron flux density of 106 s−1mm−2.1. IntroductionThe mass of the neutrino is obtained by KATRIN by observing the β-electron spectrum fromthe decay of tritium in the Windowless Gaseous Tritium Source (WGTS). The β-electrons areemitted isotropically and guided magnetically through the beamline to the spectrometers[1].Monte Carlo simulations have been performed to understand scattering and other processesand to produce simulated spectra. Another crucial task of this beam transport is the efficientretention of tritium ions. During commissioning the detector board may be replaced by aFaraday cup to study the ion retention.The tritium source properties are required to be stable and known to a high precision, andwill therefore be monitored continuously by several systems, including the FBM[2]. The FBMwill measure real-time count rates and differential β-electron spectra. Analysis of such spectraresult in continuous monitoring of the tritium source with high energy resolution and precision.2. Monitoring of the tritium source with 0.1% precisionTwo key parameters of the WGTS which are required to be continuously monitored are• Column density, NThe number of molecules within a flux tube volume of unit cross section.• Tritium purity, εTThe ratio of tritium ions (T2) to the total sum of atoms (DT, HT, D2, HD, He).The FBM measures the count rate S from the source which can be used together with thetritium purity to monitor the column density viaS = C · εT ·N (1)21234567890Neutrino2016 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 888 (2017) 012229  doi :10.1088/1742-6596/888/1/012229where C is a proportionality constant encompassing experimental properties.3. The FBM detector boardThe Forward Beam Monitor is the only device of KATRIN capable of taking measurementsdirectly inside the β-electron flux tube. A 2m long UHV manipulator (figure 1) moves thedetector to any position within the flux tube with 0.1mm precision.Figure 1. The FBM (left) attached to the CPS (right). The detector board can be insertedinto the flux tube in the CPS.3.1. PIN diodes for electron detectionThe detector board is equipped with two Hamamatsu PIN diodes of different sizes to fulfil severalpurposes. As part of the monitoring system the FBM will determine the relative β-electron fluxwith a precision of 0.1% in less than 60 s. A differential β-electron spectrum can be obtainedwith an energy resolution of FWHM = 2.0 keV at a threshold of 6.5 keV1.Figure 2. Three day stability test using a83Rb source.Figure 3. 83Rb spectrum obtained with aHamamatsu PIN diode.3.2. Additional measurement capabilitiesThe FBM detector is equipped with further devices for supplementary measurements, including• Faraday CupAn alternative detector board, equipped with a Faraday cup[4], will be used duringcommissioning in order to check ion blocking, measure the radial ion distribution in thebeamline, and check the simulated source gas models by measuring secondary electrons.1 For x-rays the energy resolution is FWHM = 1.5 keV and the threshold is 4.0 keV.31234567890Neutrino2016 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 888 (2017) 012229  doi :10.1088/1742-6596/888/1/012229• Temperature gaugeTo monitor temperature for detector drifts and offline corrections.• Hall sensorTo measure the magnetic field inside the flux tube for relative position determination andvalidation of magnetic field models.• LEDTo find absolute position inside the beam tube.4. MC simulations of differential e− spectra from the KATRIN sourceSmall fluctuations of the source properties lead to changes in the shape of the differential e−spectrum. To understand these effects Monte-Carlo simulations have been performed using theKATRIN software package Kassiopeia.The acceptance angle for the FBM is expected to be 52.6◦, however the electrons undergoscattering effects which change their inclination angle. Therefore, electrons were generatedspherically and tracked through the WGTS. The amount of electrons leaving the WGTS towardsthe transport section are compared to those generated with particular inclination angle (figure4). A plateau can be seen between 60◦ and 110◦. The FBM will measure deep into the energyspectrum where electrons with a smaller kinetic energy are more likely to scatter in the sourceand change their respective inclination angle (figure 5).Fluctuations in the column density are expected to be in the 10−3 regime, which requireshigh statistics MC simulation to be resolved. Each electron with an energy between 1 keV and18.6 keV is tracked until it leaves the WGTS or is trapped inside the source, thereby undergoingelastic and inelastic scattering as well as ionisation of atoms.°starting angle / 0 20 40 60 80 100 120 140fraction / %020406080100°52.6Figure 4. Electron angular distribution.°starting angle / 0 20 40 60 80 100 120 140fraction / %020406080100Binning 1 - 2 keVBinning 2 - 3 keVBinning 3 - 4 keVBinning 4 - 5 keVBinning 5 - 6 keVBinning 6 - 7 keVBinning 7 - 8 keVBinning 8 - 9 keVBinning 9 - 10 keVBinning 10 - 11 keVBinning 11 - 12 keVBinning 12 - 13 keVBinning 13 - 14 keVBinning 14 - 15 keVBinning 15 - 16 keVFigure 5. Energy binning of starting angle.References[1] KATRIN design report, J. Angrik et al., 2004. 2005.[2] Monitoring of the operating parameters of the KATRIN Windowless Gaseous Tritium Source, M. Babutzka,M. Bahr, J. Bonn, B. Bornschein, A. Dieter, et al., New J. Phys., 14:103046, 2012.[3] Modelling of the response function and measurement of transmission properties of the KATRIN experiment,PhD thesis by Stefan Groh, KIT/IEKP, Jan 2015.[4] Faraday Cup, Manuel Klein, Neutrino 2016, 2016.

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Monitoring the KATRIN source properties within the beamline

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