Biomedical subjects

R W Boswell

Publications and source records attributed to R W Boswell.

3 recordsLinked to original sources

PubMed2006

Upstream ionization instability associated with a current-free double layer.

A low frequency instability has been observed using various electrostatic probes in a low-pressure expanding helicon plasma. The instability is associated with the presence of a current-free double layer (DL). The frequency of the instability increases linearly with the potential drop of the DL, and simultaneous measurements show their coexistence. A theory for an upstream ionization instability has been developed, which shows that electrons accelerated through the DL increase the ionization upstream and are responsible for the observed instability. The theory is in good agreement with the experimental results.

Journal Article↗

PubMed2005

Experimental evidence of a double layer in a large volume helicon reactor.

The self-consistently generated current-free electric double layer (DL) is shown to scale up with the source tube diameter and appears not to be affected by rf driving frequency and changes in reactor geometry. This Letter presents the first simultaneous measurements of local plasma potential and beam energy as a function of axial position. The DL is shown to be no more than 5 mm thick (20 D lengths) and positioned just downstream of the maximum in the magnetic field gradient. Furthermore, its position relative to the magnetic field is observed to be invariant as the magnetic field is translated axially. Measurements of the potential drop across the DL are presented for pressures down to 0.09 mTorr and the DL strength (phiDL/T(e)) is determined to be between 5 and 7.

Journal Article↗

PubMed1990

Sounds of the future? Ultrasonography in the field.

During the past two decades, the development and maturation of ultrasonography as a diagnostic tool has revolutionized the practice of radiology, cardiology, obstetrics and surgery. In fact, few areas of medicine have not been affected by this technology. Unlike the still-frame images of standard X-rays and computerized axial tomography (CAT) scans, ultrasound technology displays an ongoing cross-sectional image of an anatomic area in "real time," which can then be stored and played back on videotape. This ability to quickly assess function, as well as anatomy, has become invaluable in the management of critically ill patients.

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