摘要:

We describe a simple marginal oscillator that operates at ultralow power dissipation (≥20 &mgr;W at 750 MHz) for use in ultrasensitive low noise magnetic resonance detection at very low temperatures. We have operated the circuit down to 0.6 K with the sample maintained below 20 mK and in magnetic fields up to 4.0 T. The samples are maintained at mK temperatures by physically separating the sample from the rf coil.

ISSN:0034-6748    

DOI:10.1063/1.1142980

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have developed a high‐density source of metastable neon and have selectively quenched both metastable species using a standing‐wave dye laser. The source is compact, stable, and produces an average intensity of 3.6×1014sr−1 s−1and a density on target of 7.7×106cm−3.

ISSN:0034-6748    

DOI:10.1063/1.1143000

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A novel calorimeter for millimeter wave radiation based on the photoacoustic effect has been investigated. Single pulses from a 3‐&mgr;s, 1‐MW gyrotron operating between 135 and 150 GHz were measured. The joulemeter has both a slow time response (<500 Hz), due to gas expansion, and a fast time response (≳500 Hz), due to acoustic modes of the resonator and windows. The slow time response, which was more suitable for power and energy measurements, was compared with a calibrated thermopile detector and was found to be linear over the range of 0.15–3 J, with an error of less than ±5% near 3 J. The calorimeter was also tested with modes having different power distributions in space; the response was found to be independent of spatial power distribution. The joulemeter is a simple, rugged device that can be used in transmission or absorption mode. Use in transmission mode is attractive for basic research on high‐power microwave sources.

ISSN:0034-6748    

DOI:10.1063/1.1142950

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An ultrahigh vacuum (UHV) surface analysis chamber coupled with a high pressure cell (HPC) is described. The UHV chamber has been designed using an octagonal format to utilize several surface analytical techniques. In addition, the single‐level surface analysis chamber design allows simple access to the HPC for carrying out kinetic studies at elevated pressures (≳1 atmosphere) withinsitutransfer from the UHV chamber. The UHV‐compatible HPC has been designed to facilitate the exchange of the sample or repair of the sample holder while maintaining the analysis chamber at UHV conditions.

ISSN:0034-6748    

DOI:10.1063/1.1142951

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A method is described that allows the efficient collection and focusing of ions, with kinetic energies between 1 and 5 eV, onto a nonmagnetic metal surface. Magnetic fields near the sample are used to focus the low‐energy ions and typical currents achieved thus far exceed 100 nA/cm2for 1‐eV ion energies. The magnetic field of a magnet placed behind the sample significantly reduces the problem of transverse displacement of the ions due to beam divergence and space‐charge effects. The magnetic field confines the particle to a circular orbit along the axial direction (cyclotron motion), while leaving the kinetic energy of the ion unaffected. We have utilized this method to interact Ar+and CH+3with 1‐eV translational energy and 100 nA of current on a Pt surface.

ISSN:0034-6748    

DOI:10.1063/1.1142952

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A sputtering source utilizing both microwave and dc planar magnetron plasmas is described. Microwave power is introduced into the plasma by a coaxial‐type cavity. The magnetron target is placed on the open end of the inner conductor. The microwave propagation from the surface of the plasma column produces additional gas ionization, resulting in a denser plasma at constant voltage. The operating pressure of this source is one‐tenth as low as that of a conventional magnetron source. Measured deposition uniformity for Cu is ±4.5% within a 10‐cm diameter at dc 100 W and microwave 800‐W discharge powers for a 15‐cm‐diam magnetron at 6×10−4Torr. The plasma impedance decreases with an increase in the inner conductor diameter and target diameter. The target‐plasma sheath potential can be controlled by microwave power.  

ISSN:0034-6748    

DOI:10.1063/1.1142953

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A self‐tuning algorithm is described and applied to a temperature servo control. It allows the regulator to adapt to slowly changing processes while keeping the response of the control system unaffected. Examples dealing with adaptions to set points with different dynamics and a reaction of the self‐tuner to changes in the gain of the power amplifier are provided.

ISSN:0034-6748    

DOI:10.1063/1.1142954

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The reflectivity of a multilayered structure on top of a silicon wafer has been measured in a rapid thermal processor at 0.6328 &mgr;m. This structure consisted of a Ge thin film sandwiched between SiO2and Si3N4films. The wafer has been submitted to thermal cycles around the melting point of Ge (938 °C). It has been shown that the onset of Ge melting which corresponds to an abrupt reflectivity change can be detectedinsituby monitoring the intensity of a reflected laser light. It has therefore been demonstrated that the detection of Ge thin‐film melting can serve as a tool for temperature sensor calibration in a rapid thermal processor.

ISSN:0034-6748    

DOI:10.1063/1.1142955

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A remote flow cell has been interfaced to a scanning uv‐visible absorbance detector for the detection of gas chromatography (GC) analytes. The unique optical bench, detection scheme, and thermal control allow low‐noise operation at flow cell temperatures of 350 °C. Noise of 1×10−5a.u. (peak to peak over a 1‐min period) and drift at the 1×10−4a.u./h level facilitate detection of coumarin in the gas phase at 40 pg/s. Flow cell volume was optimized for use with capillary GC columns. An effective band pass of <3 nm provides spectral resolution which shows solute absorbance fine structure to aid in compound identification.

ISSN:0034-6748    

DOI:10.1063/1.1142956

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A series of polyimide films irradiated by 170 keV N+and 120 keV B+with controlled and related implantation conditions were investigated with respect to their microstructures in modified layers, as well as their application prospects as temperature sensors. The sensitivities and sensitive ranges of these functional materials were correlated with the implantation conditions in terms of the Raman spectroscopic results. This well‐defined relationship was interpreted with perspectives of ion beam microstructural modification, which provides a deeper insight into the fundamental aspects for the synthesis of temperature‐sensitive materials out of polyimide precursor. It seems that greater irradiation dose, stronger beam current density, and higher target temperature constitute a set of favorable conditions for the fabrication of temperature sensors with a comparatively broad sensitive scope.

ISSN:0034-6748    

DOI:10.1063/1.1143829

出版商:AIP    

年代:1992

数据来源: AIP