COUPP Carbon and Fluorine Recoil ... - University of Chicago · PICASSO model, (dashed line) or...
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Carbon and Fluorine Recoil Thresholds Alan Robinson July 26, 2012 IDM 2012, Chicago, IL COUPP
Transcript of COUPP Carbon and Fluorine Recoil ... - University of Chicago · PICASSO model, (dashed line) or...
Carbon and FluorineRecoil Thresholds
Alan RobinsonJuly 26, 2012 IDM 2012, Chicago, IL
COUPP
Slide 2/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Definition:
The probability for producing an observable bubble from a nuclear recoil.
● Method
● Previous calibrations
● This calibration
● Prospects
Bubble nucleation efficiency
SRIM calculation of 15 keV fluorine recoils in CF3I
Length scaleat 15keV threshold
Slide 3/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Produce a spectrum of nuclear recoils.
► Neutron propagation simulated with MCNP
● Measure a count rate.
● Change the detector's threshold, repeat.
Calibration method
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 4/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Nuclear recoil spectra
● 152 keV neutrons from 88Y/Be give:► Hard upper limit on recoil energy (31 keV on F)
► Only C & F recoils at >5keV, the ROI.
● Method
● Previous calibrations
● This calibration
● Prospects
Integrated nuclear recoil spectra from neutrons in CF3I
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IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Neutrons from 88Y/Be
Be9 ( γ , n) Q=1666keV
M. Fujishiro et al., Can. J. Phys. 60, 1672 (1982).
Y88 →
● Mono-energetic 152 keV neutrons.
● emitted / neutron emitted
70 n/s
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 6/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
PICASSO's calibration
PICASSO's detector response to monoenergetic neutrons● Method
● Previous calibrations
● This calibration
● Prospects
4.8 keV
40 keV2 MeV
Archambault et al., New J. Phys. 13, 043006 (2011).
Slide 7/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
PICASSO's calibration (con't)
● Fit a functional form:
►P – nucleation efficiency
► – fitted parameter
►Ethr – calculated threshold energy
►Er – recoil energy
P=1−exp {−αE r−E thrE thr }
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 8/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Using COUPP-4kg with AmBe neutrons.
► Fit to
▻ PICASSO model, (dashed line) or
▻ Step function w/ length scale cutoff, (solid line).
AmBe calibrations
D.A Fustin, Ph.D. ThesisUniv. of Chicago, 2012.
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 9/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Carbon and fluorine recoils produce longer tracks in CF3I than in C4F10.
Is CF3I different?
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 10/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Calibration bubble chambers
● < 2mm moderating material.
● Pressure (threshold) scanning during each expansion.
● Method
● Previous calibrations
● This calibration
● Prospects
Sample expansion history
trigger
Slide 11/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Use:
► is the PICASSO model
Models
P=1−exp {−(α E r−E thrE thr )β
}● Method
● Previous calibrations
● This calibration
● Prospects
Slide 12/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Count rates
Normalized and background subtracted count ratefor Y/Be neutrons on CF3I bubble chambers
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 13/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● 15% uncertainty in recoil rate normalization, mostly from MCNP simulation.
● 0.5°C uncertainty in temperature (8% threshold uncertainty)
Systematics
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 14/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Obtain a nucleation efficiency calibration at low energy using a consistent threshold model.
● Use a monoenergetic neutron beam to calibrate at other energies.
● Study the response of other fluids with Y/Be.
Prospects
● Method
● Previous calibrations
● This calibration
● Prospects
Slide 15/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
● Juan I. Collar and C. Eric Dahl
University of Chicago
● Brad DiGiovine, K. Ernst Rehm, and Claudio Ugalde
Argonne National Lab
● Andrew Sonnenschein
Fermilab
● NSERC PGS D fellowship.
Acknowledgements
Slide 16/16
IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Collaboration
Funding and support from:
M. Ardid and M. Bou-Cabo
E. Behnke, T. Benjamin, E. Grace,C. Harnish, I. Levine, and T. Nania
J.I. Collar, R. Neilson, and A.E. Robinson
J. Brice, D. Broemmelsiek, P.S. Cooper,M. Crisler, J. Hall, W.H. Lippincott,E. Ramberg, and A. Sonnenschein
C.E. Dahl
D. Maurya and S. Priya
E. Vázquez Jáuregui
Extra slides
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IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Consistency with AmBe and multiples
Extra Slides
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IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Length scale threshold
● A step threshold in length scale make a sharp turnon:
● Y/Be data is insensitive to a > 4.
Extra Slides
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IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Length scale threshold
Extra Slides
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IDM 2012
COUPP Carbon and Fluorine Recoil Thresholds
Seitz model calculation
Extra Slides ● Two steps:
► Critical radius of the bubble
– surface tension
► Energy to form critical bubble▻ Surface formation energy - dominant
at high threshold.
▻ Heat of vaporization
P g−P l=2σRc
Pg
Pl Rc
Q=4π3r c3ρb(hb−hl)+4π rc
2(σ−Td σdT )
