project 8: a radiofrequency approach to the neutrino mass ben monreal, uc santa barbara
TRANSCRIPT
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Project 8: a Project 8: a radiofrequency approach radiofrequency approach
to the neutrino massto the neutrino massBen Monreal, UC Santa BarbaraBen Monreal, UC Santa Barbara
Project 8: a Project 8: a radiofrequency approach radiofrequency approach
to the neutrino massto the neutrino massBen Monreal, UC Santa BarbaraBen Monreal, UC Santa Barbara
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Project 8 collaboration
• UCSB: Ben Monreal
• MIT: Joe Formaggio, Asher Kaboth, Daniel Furse
• University of Washington: Hamish Robertson, Peter Doe, Leslie Rosenberg, Michael Miller, Gray Rybka, Brent Vandevender, Adam Cox, Michelle Leber, Laura Bodine
• NRAO: Rich BradleyBM & JF, arxiv:0904.2860, shortly in PRD
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Neutrino massKurie, Richardson, & Paxton 1936
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Neutrino mass
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Liouville’s theorem
x
θ x
θ
x
θ
x
θSource area ΔθΔx
determines amount of T2
Δθ determines
energyresolution
Δx is the size of your
vacuum tank
The volume of phase space is conserved
for any system obeying T symmetry
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Nondestructive measurement
•Maxwell’s Demon
• Stochastic cooling
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Cyclotron motion
Pitch angle = 90
Pitch angle = 45
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Cyclotron radiation• accelerating charge = EM
radiation
• Coherent, narrowband
• High power per electron
• Electron energy contributes to velocity v, power P, frequency ω
• Can we detect this radiation, measure v, P, ω, and determine E ± 1 eV?
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Complications
• Frequency resolution?
•Doppler shift?
•Huge fluxes!
• Available power
Systematics?
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Frequency• Schawlow: “Never
measure anything but frequency”
• f ∙ΔE/E ~ Δf = 1/Δt
• 1 eV energy resolution
• Δf /f = 2x10-6 (easy!)
• Δt = 20µs (hard!)
• βc∙Δt = 1400 meters
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Radiative losses• E changes during
measurement (cyclotron radiation)
•Decay rate ΔE/Δt α B2
• Fourier limit ΔE Δt α B-1
•Prevents high-res experiment at high B
•~1 Tesla works for 0.5 eV
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Complications
• Frequency resolution?
•Doppler shift?
•Huge fluxes!
• Available power
store > 106 cycles
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redshift
ω0(1-βcosθ)
blueshift
ω0(1-βcosθ)
ω0 (no shift)
Doppler shift
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ω0
(no shift)Multiple
small antennae
= synthetic large
antenna
Doppler shift
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ω0
(no shift)Multiple
small antennae
= synthetic large
antenna
Doppler shiftElectron moves in and out
of antenna sensitivit
y= periodic change in amplitude
(AM modulation)
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In frequency space
Frequency
ωcenter = qB/γmωside = ωcenter /(1±βcosθ)
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Complications
• Frequency resolution?
•Doppler shift?
•Huge fluxes!
• Available power
store > 106 cycles
ω0 still obtainable
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The experiment
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Endpoint signalsFrequency ROI
noDoppler
e-energy
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Endpoint signalsFrequency ROI
withDopplere-
energy
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Endpoint signalwith
Dopplere-energy
Frequency ROI
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many overlappinglow-energy electrons
many overlappinglow-energy electrons
rare high-energyelectrons
rare high-energyelectrons
100,000 tritium electrons
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Complications
• Frequency resolution?
•Doppler shift?
•Huge fluxes!
• Available power
store > 106 cycles
ω0 still obtainable
do not fake signal in ROI
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Power• At 1T, 18 keV electron emits 10-
15 W
• A 1-eV-resolution experiment will see this power in a 50kHz band
• noise power = 6x10-19 W/K
• noise RMS = 6x10-21 W/K
•4K experiment seems possible
how much detected?
divided amonghow many channels?
Keep an eye on signal width: many
broadening sources may appear
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Complications
• Frequency resolution?
•Doppler shift?
•Huge fluxes!
• Available power
store > 106 cycles
ω0 still obtainable
do not fake signal in ROI
needs detailed RF design
Systematics?
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Systematics•Magnet inhomogeneity
and drift: should respond well to source calibrations
• e-T and e-wall scattering
a)Run at low densityb)Each scattering
event shifts/broadens the cyclotron frequency
c)fiducialize?
• Full differential spectrum; no first-order correction for source strength
•No electrostatics; source is grounded
• T2 molecular final state = irreducible 0.3 eV (+/- 0.01 eV?) blurring of endpoint
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Real-world designs
•Gray Rybka, UW: two-wire antenna
•Rich Bradley, NRAO: microwave receivers from radio astronomy
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Alternatives• Toroidal magnetic
field?
•Magnetic bottle?
•Ramsey spectroscopy?
• Bucket spectroscopy?
Measuring frequency in one pass: Δf = Δt-1
N passes of Δt each: Δf = (Δt√N)-1
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Bucket spectroscopy
• Shoot microwave beam (at ROI frequency) into magnet.
• Electron cyclotron in microwave field = electron bunch in synchrotron RF bucket
•Use “bucket” to grab and store ROI electrons, later accelerate to make detectable
•Decouples time constraints from detection constraints
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Conclusions
• UCSB: Ben Monreal
• MIT: Joe Formaggio, Asher Kaboth
• University of Washington: Hamish Robertson, Peter Doe, Leslie Rosenberg, Michael Miller, Gray Rybka, Brent Vandevender, Adam Cox, Michelle Leber, Laura Bodine
• NRAO: Rich BradleyBM & JF, arxiv:0904.2860, shortly in PRD