Measurements of the ballistic-phonon component resulting from nuclear and electron recoils in crystalline silicon

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.3244· OSTI ID:286672

Lee, A T ^[1]; Cabrera, B; Dougherty, B L; Penn, M J ^[2]; Pronko, J G ^[3]; Tamura, S ^[4]

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1. Center for Particle Astrophysics and Department of Physics, University of California, Berkeley, California 94720 (United States)
2. Department of Physics, Stanford University, Stanford, California 94305-4060 (United States)
3. Lockheed Research and Development Division, 3251 Hanover Street, Palo Alto, California 94304 (United States)
4. Department of Applied Physics, Hokkaido University, Sapporo 060 (Japan)

We present measurements of the ballistic-phonon component resulting from nuclear and electron recoils in silicon at {approximately}380 mK. The detectors used for these experiments consist of a 300-{mu}m-thick monocrystal of silicon instrumented with superconducting titanium transition-edge sensors. These sensors detect the initial wavefront of athermal phonons and give a pulse height that is sensitive to changes in surface-energy density resulting from the focusing of ballistic phonons. Nuclear recoils were generated by neutron bombardment of the detector. A Van de Graaff proton accelerator and a thick {sup 7}Li target were used. Pulse-height spectra were compared for neutron, x-ray, and {gamma}-ray events. A previous analysis of this data set found evidence for an increase in the ballistic-phonon component for nuclear recoils compared to electron recoils at a 95{percent} confidence level. An improved understanding of the detector response has led to a change in the result. In the present analysis, the data are consistent with no increase at the 68{percent} confidence level. This change stems from an increase in the uncertainty of the result rather than a significant change in the central value. The increase in ballistic phonon energy for nuclear recoils compared to electron recoils as a fraction of the total phonon energy (for equal total phonon energy events) was found to be 0.024{sup +0.041}{sub {minus}0.055} (68{percent} confidence level). This result sets a limit of 11.6{percent} (95{percent} confidence level) on the ballistic phonon enhancement for nuclear recoils predicted by {open_quote}{open_quote}hot spot{close_quote}{close_quote} and electron-hole droplet models, which is the most stringent to date. To measure the ballistic-phonon component resulting from electron recoils, the pulse height as a function of event depth was compared to that of phonon simulations. (Abstract Truncated)

• OSTI ID: 286672
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 5 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
66 PHYSICS
ELECTRON COLLISIONS
ION COLLISIONS
MONOCRYSTALS
PERFORMANCE
PHONONS
RECOILS
SI SEMICONDUCTOR DETECTORS
SILICON