Very high E resolution

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Tritium ? decay end-point
Why tritium? 1- low E0 ?18.6 keV relative m??
effect larger 2- lowest Z
smallest Coulomb effect
3- low density gaseous source e- energy loss
small 4- high activity
T1/2 12.3 y
Very high E resolution counts
rate Very low background
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The Mainz experiment
Guiding magnets
High field electrodes
Electrons are magnetically guided around
magnetic field lines into the spectrometer.
Accepted solid angle 2 p. In spectrometer
broad beam of electrons almost parallel to
magnetic field lines and running against an
electrostatic potential. Integrating high-energy
pass filter Only the electrons which pass the
electrostatic barrier are reaccelerated and
collimated onto the detector. Scanning the
electrostatic retarding potential ? Ee spectrum
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status of present tritium experiments
Troitsk
Mainz gaseous T2-source
quench-condensed solid
T2-source
electrostatic retarding spectrometers with
magnetic adiabatic collimation
analysis 1994-99, 2001
analysis 1998/99, 2001
both experiments have reached their intrinsic
limit of sensitivity
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COMBINED ANALYSIS OF CMB, 2DF AND LY-ALPHA DATA
BY THE WMAP TEAM (astro-ph/0302209 )
95 c.l. but model dependant, systematics,
More conservative
Hannestad astro-ph/0303076 (also Elgarøy Lahav,
astro-ph/0303089)
Near future PLANCK (CMB)
SDSS (106 galaxies) ? 0.1 eV
sensitivity
A challenge for future direct mass measurements.