COUPP. Carbon and Fluorine Recoil Thresholds. Alan Robinson July 26, 2012 IDM 2012, Chicago, IL

Transcription

1 Alan Robinson July 26, 2012, Chicago, IL

2 Previous This calibration Prospects Bubble nucleation efficiency Definition: The probability for producing an observable bubble from a nuclear recoil. SRIM calculation of 15 kev fluorine recoils in CF3I Length scale at 15keV threshold Slide 2/16

3 Previous This calibration Prospects Calibration method Produce a spectrum of nuclear recoils. Neutron propagation simulated with MCNP Measure a count rate. Change the detector's threshold, repeat. Slide 3/16

4 Previous This calibration Prospects 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. Integrated nuclear recoil spectra from neutrons in CF3I Slide 4/16

5 Neutrons from Previous This calibration Prospects 9 88Y/Be Be ( γ, n) Q=1666keV n/s Y M. Fujishiro et al., Can. J. Phys. 60, 1672 (1982). Slide 5/16 Mono-energetic 152 kev neutrons. emitted / neutron emitted

6 Previous This calibration Prospects PICASSO's calibration PICASSO's detector response to monoenergetic neutrons 2 MeV 40 kev 4.8 kev Slide 6/16 Archambault et al., New J. Phys. 13, (2011).

7 Previous This calibration Prospects PICASSO's calibration (con't) Fit a functional form: { E r E thr P=1 exp α E thr P nucleation efficiency Ethr Er Slide 7/16 } fitted parameter calculated threshold energy recoil energy

8 Previous This calibration Prospects Slide 8/16 AmBe Using -4kg with AmBe neutrons. Fit to model, (dashed line) or Step function w/ length scale cutoff, (solid line). PICASSO D.A Fustin, Ph.D. Thesis Univ. of Chicago, 2012.

9 Previous This calibration Prospects Slide 9/16 Is CF3I different? Carbon and fluorine recoils produce longer tracks in CF3I than in C4F10.

10 Previous This calibration Prospects Calibration bubble chambers < 2mm moderating material. Pressure (threshold) scanning during each expansion. Sample expansion history trigger Slide 10/16

11 Previous This calibration Prospects Slide 11/16 Models Use: {( E r E thr P=1 exp α E thr is the PICASSO model )} β

12 Previous This calibration Prospects Slide 12/16 Count rates Normalized and background subtracted count rate for Y/Be neutrons on CF3I bubble chambers

13 Previous This calibration Prospects Slide 13/16 Systematics 15% uncertainty in recoil rate normalization, mostly from MCNP simulation. 0.5 C uncertainty in temperature (8% threshold uncertainty)

14 Previous This calibration Prospects Slide 14/16 Prospects 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.

15 Acknowledgements Juan I. Collar and C. Eric Dahl University of Chicago Brad DiGiovine, K. Ernst Rehm, and Claudio Ugalde Argonne National Lab Andrew Sonnenschein Fermilab Slide 15/16 NSERC PGS D fellowship.

16 Collaboration 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 Funding and support from: Slide 16/16

17 Extra slides

18 Extra Slides Slide 18/16 Consistency with AmBe and multiples

19 Extra Slides Slide 19/16 Length scale threshold A step threshold in length scale make a sharp turnon: Y/Be data is insensitive to a > 4.

20 Extra Slides Slide 20/16 Length scale threshold

21 Extra Slides Seitz model calculation Two steps: Critical radius of the bubble surface tension 2σ P g P l = Rc Energy Pl Pg Rc to form critical bubble Surface Slide 21/16 formation energy - dominant at high threshold. Heat of vaporization 4π 3 dσ 2 Q= r c ρ b (h b h l )+4 π r c σ T 3 dt ( )