Michael Przyrembel

A solenoid retarding spectrometer with high resolution and transmission for keV electrons

Abstract We have built an electrostatic electron spectrometer combining both high resolution and large luminosity. The instrument consists essentially of two superconducting solenoids separated by a system of ring electrodes of 4 m in length. Source and detector are placed in the high-field regions of the superconducting solenoids, whereas the repellent analyzing electrostatic potential of the ring electrodes peaks at the minimum of the magnetic field in between these solenoids. The magnetic guiding field provides (i) the acceptance of the full foreward solid angle of 2π, (ii) the transformation of the transverse cyclotron motion into longitudinal motion parallel to the magnetic field. The energy resolution of the electrostatic filter is determined by the ratio of the magnetic fields at the source and in the analyzing plane. It is typically 5 × 10 3 in our case. The spectrometer will serve first of all to investigate the limits of the rest mass of the electron antineutrino from 3 H 2 s-decay. It has been tested by measuring conversion lines from a 83m Kr source which yielded an energy of Eγ = 32151.5(11) eV for the corresponding nuclear transition.

Improved limit on the electron-antineutrino rest mass from tritium β-decay

Abstract The endpoint region of the β-spectrum of tritium was remeasured by an electrostatic spectrometer with magnetic guiding field. It enabled the search for a rest mass of the electron-antineutrino with improved precision. The result is m2v=−39±34stat±15syst(eV/c2)2, from which an upper limit of mv m( T )−m( 3 He )=18 591±3 eV /c 2 .

Status and perspectives of the Mainz neutrino mass experiment

Abstract The Mainz measurement in 1994 is discussed in the view of the problem of “negative m ν 2 ” obtained in the analysis for larger energy intervals below the endpoint of the β spectrum. A possible explanation due to a roughening transition of the T 2 film is given. The very recent improvement of the Mainz setup and a first 4 weeks measurement is presented. An outlook to the perspectives of the present setup and into the future is given.

Precision measurement of the conversion electron spectrum of83m Kr with a solenoid retarding spectrometer

This paper reports on precision measurements of conversion lines in the decay of83mKr with nuclear transition energies of 32.1 keV and 9.4 keV, respectively. The spectra were taken from a submonolayer surface of83mKr frozen onto a cold backing, using the new Mainz solenoid retarding spectrometer. The high luminosity and resolution of this instrument enables the observation of all allowed conversion lines up to theN-shell and to fully separate the elastic component from inelastic satellites. The combined analysis of the data yields the transition energiesEy=32151.5±1.1 eV and 9405.9±0.8 eV, respectively. The experiment served also to pilot the application of this spectrometer to the question of a finite neutrino rest mass, searched for in theβ-decay spectrum of tritium and to problems in precision electron spectroscopy in general.

Structural Stability of Solid Deuterium Films

The wetting behavior of quenched-condensed solid D2 films has been investigated by means of light scattering. On the substrates used here (graphite and aluminum) molecular deuterium displays triple point wetting and hence dewets in the solid state, provided the temperature is high enough that thermally activated diffusion processes can take place. This manifests itself in a coarse-graining of the D2 film. In order to avoid this process and to obtain complete wetting of solid D2 we have modified the adsorbate-substrate interaction potential by preplating the substrates with thin inert layers of Ne, Ar, CH4 or C2H6. The predicted change in the wetting properties was not observed, however, suggesting that the existing picture of triple point wetting of van der Waals systems is not complete. The implications of these results for a neutrino mass experiment where quenched-condensed molecular tritium films are used as a source are discussed.

Wetting behavior of solid hydrogen films

We have studied the dewetting of quench-condensed solid hydrogen films on bare and Ne plated Ag substrates. Information about the morphology of the films during the dewetting process is obtained from measurements of photoelectron tunneling through the films and complementary surface plasmon resonance data. Plating the Ag substrate with Ne films of various thickness allows to tune the strength of the van der Waals interaction with the hydrogen and thus to change the H2 films from a state of incomplete to complete wetting.

A new upper limit of the electron antineutrino rest mass from tritium β-decay

Abstract A new upper limit of the electron antineutrino rest mass has been deduced from the tritium β-decay spectrum. A source of molecular tritium has been investigated with a new solenoid retarding spectrometer. The results are m v e 2 = −39 ± 34 stat ± 15 syst ( eV ) 2 c 4 from which we conclude m v e ≤ 7.2 eV with 95% c.l. Our β-endpoint corresponds to a 3 H 3 He atomic mass difference of Δm( 3 H  3 He ) = 18591 ± 3 eV/c 2 (1σ).

Stability of solid T2 films

Abstract Films of molecular tritium, physisorbed on a cold substrate, have been investigated by means of ellipsometry. A significant effect of the radioactive decay processes on the desorption kinetics and the low temperature stability of these films is not observed.

New results from the mainz neutrino mass experiment

The present status of the Mainz tritium β decay experiments is given. The very recent improvement of the Mainz setup and the first results from tritium data are presented. The former trend towards negative values of m ν 2 for increasing data intervals was identified to be a roughening transition of the quench-condensed T 2 film, which now can be avoided.

A new upper limit of the electron anti neutrino rest mass from tritium β-decay

Abstract A new upper limit of the electron anti neutrino rest mass has been deduced from the tritium β-decay spectrum. A source of molecular tritium has been investigated with a new solenoid retarding spectrometer. The results are m ν ϵ 2 = −38.8 ± 34.1 stat ± 15.1 syst (eV) 2 /c 4 from which we conclude m ν ϵ ≤ 7.2 eV/c 2 with 95% c.l. Our β-endpoint corresponds to a 3H-3He atomic mass difference of Δm( 3 H- 3 He) = 18590.8 ± 3 eV/c 2 (1σ) .