double beta decay - daughter ion detection on an optical ... · 3 ba+ levels in vacuum motivation...
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Double beta decay - daughter ion detection on an optical fiber for EXO
Brian MongShon Cook
William Fairbank
Xe136 → Ba++ + 2e-
Supported by NSF and DOE
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Outline
● Motivation● EXO – implementation● Detector development● Test data using R6G● Ion deposition setup
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Ba+ levels in vacuum
Motivation
● Successful identification of the ββ decay daughter eliminates all potential background sources except 2νββ
● Detecting a single Ba ion in 1028 Xe atoms is a unique challenge 493nm
650nm
54D3/2
62P1/2
62S1/2
Xe136 → Ba++ + 2e-
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Fiber optic detector schematic
Single-mode fiberDichroicmirror
LXe TPC
LXe136
ββ decay event
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Single-mode fiberDichroicmirror
LXe TPC
LXe136
Fiber optic detector schematic
Daughter ion is drawn to the detector
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Single-mode fiberDichroicmirror
LXe TPC
LXe136
Fiber optic detector schematic
Daughter ion is drawn to the detector
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Single-mode fiberDichroicmirror
LXe TPC
LXe136
Fiber optic detector schematic
Fiber tip is cooled to freeze the ion in xenon
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Single-mode fiberDichroicmirror
LXe TPC
LXe136
Fiber optic detector schematic
The fiber provides excitation light and collects fluorescence
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Laser
Coupler
spectrometer
CCD
D = 100μm
n>3
Single-mode fiberDichroicmirror
LXe TPC
LXe136
This is only one of 3 tagging methods being explored for EXO
Fiber optic detector schematic
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Testing the detector – R6G dye
● R6G is a convenient analog for Ba+ fluorescence● Similar lifetime● Similar cross-section● Absorption and emission
wavelengths
Optical fiber detector submerged in a dilute solution of R6G
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Signal and background of the fiber detector
Fluorescence
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Fluorescence
Silica Raman
Methanol Raman
Signal and background of the fiber detector
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Optical fiber detector test
100 molecule RAW signal
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Optical fiber detector test
Signal Components
100 molecule RAW signal
R6G Fluorescence
Silica Raman
Methanol Raman
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Optical fiber detector test
→100 molecule fluorescence
signal
100 molecule RAW signal
Subtract out the backgroundsSilica Raman Methanol Raman
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Single molecule results
Detection ~1 molecule level is possible
Repeating experiment this summer as an internship project
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Ion beam deposition setup
Barium Source
Einzel Lens
Deflection Plates
ExB Filter
Deflection Plates
Einzel Lens
Einzel Lens
Deceleration Lens
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END
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Ba+ in SAr results: see Ba
Filter cutoffFilter cutoff
Heated Ba source
Ion beam source
Definitely see Ba emissionHaven’t yet looked for Ba+ emissionNot sure if Ba due to Ba from ion source or neutralized Ba+