Cryogenic phonon-mediated particle detectors for dark matter searches and neutrino physics

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:6978834

Lee, A T.J.

This work describes the development of cryogenic phonon-mediated particle detectors for dark matter searches and neutrino detection. The detectors described in this work employ transition-edge sensors, which consist of a meander pattern of thin-film superconductor on a silicon substrate. When phonons from a particle interaction in the crystal impinge on the sensor in sufficient density, sections of the line are driven normal and provide a measurable resistance. A large fraction of the thesis describes work to fully characterize the phonon flux from particle interactions. In one set of experiments, [approximately]25% of the phonon energy from 59.54 keV gamma-ray events was found to propagate [open quotes]ballistically[close quotes] (i.e., with little or no scattering) across a 300 [mu]m thick crystal of silicon. Gamma-rays produce electron recoils in silicon whereas with dark matter and neutrino experiments nuclear recoils are also of interest. Two experiments were done to measure the ballistic component that arises from neutron events, which interact via nuclear recoil. Measurements indicate that the fraction of energy that is ballistic is [approximately]50% greater for nuclear recoils than for electron recoils. Two novel detectors were fabricated and tested in an attempt to improve the sensitivity of the detectors. In the first detector, relatively large Al pads were linked by 2 [mu]m wide Ti lines in a meander pattern. Phonons impinging on the Al pads create quasiparticles which diffuse in the Al pad until they are trapped in the lower gap Tl links. The sensitivity of the detector was found to be increased by this [open quotes]funneling[close quotes] action. A second detector was built that incorporates 0.25 [mu]m wide lines defined by direct electron-beam exposure of the photoresist. If the superconducting line is sufficiently narrow, single phonons are capable of driving sections normal which should improve the sensitivity and linearity of the detector.

• Research Organization: Stanford Univ., CA (United States)
• OSTI ID: 6978834
• Country of Publication: United States
• Language: English

Related Subjects

440104* -- Radiation Instrumentation-- High Energy Physics Instrumentation
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
DESIGN
DETECTION
FILMS
MATTER
MEASURING INSTRUMENTS
NONLUMINOUS MATTER
RADIATION DETECTORS
SUPERCONDUCTING DEVICES
THIN FILMS