摘要:

A novel liquid droplet generator, or atomizer, capable of generating either monodisperse droplet streams or a polydisperse spray, has been characterized using phase‐Doppler anemometry and two visualization techniques. The atomizer consists of a piezoelectric driver in a circular housing with an orifice plate across the end of the housing. Unlike conventional droplet generators or atomizers, this device directly induces a high‐amplitude velocity perturbation of the liquid jet. Orifice plates with a circular hole (diameter: 34 or 98 &mgr;m) or a rectangular hole (527×31 &mgr;m2) were used. In the low‐power mode, the atomizer with a circular orifice generated a stream of monodisperse water droplets with a diameter 1.5 to 3.4 times the jet diameter and a separation 2.3 to 26 times the jet diameter at 10 to 68 kHz. Droplets smaller than the minimum size predicted by Rayleigh’s criterion can be generated with an increased modulation power. The droplet velocity can be adjusted in a wide range (4 to 26 m/s), and a high Reynolds number (∼250) can be attained. In the high‐power mode, the atomizer produced a polydisperse water spray with a Sauter mean diameter less than half the jet (equivalent) diameter. The rectangular orifice required significantly less driving power to generate a spray. This atomizer is suitable for both fundamental studies and practical applications.  

ISSN:0034-6748    

DOI:10.1063/1.1144537

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An automated vibrating‐sample magnetometer is described where the variable magnetic field in excess of ±1.1 T is produced in a 26 mm bore by an assembly of nested, rotating permanent magnet cylinders. The homogeneity is better than 0.3%±4 mT in 1 cc. The instrument has dimensions 200×420×700 mm, and its mass is 20 kg. Sensitivity is better than 0.4 &mgr;J/T (4×10−4emu), which permits study of the susceptibility, magnetization, and hysteresis of a wide range of magnetic materials, including ferromagnetic thin films.

ISSN:0034-6748    

DOI:10.1063/1.1144538

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We have designed a probe to rotate a sample around two independent axes in a magnetic field of up to 8 T and at temperatures varying from 3 K to room temperature. The sample is in very good thermal contact with a thermometer and a regulated heater, enabling precise temperature control. Pogo pins enable quick electrical connections to the sample. Two computer‐controlled stepper motors rotate the sample around the two independent axes. This probe was primarily designed to investigate the anisotropy of the critical currents of superconducting thin films in a magnetic field.

ISSN:0034-6748    

DOI:10.1063/1.1144539

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We describe a time‐to‐digital converter able to measure intervals as great as 100 ns with a resolution of 4 ps rms. It achieves this large dynamic range by simultaneously sampling four sinusoidal wave forms (sine and cosine waves at 200 and 6.25 MHz) derived from a single quartz oscillator. Twelve‐bit analog‐to‐digital conversion of the 200 MHz waves yields the high time resolution. Eight‐bit conversion of the 6.25 MHz samples removes the cycle ambiguity of the 200 MHz data. The digital words are pipelined in a fully parallel data flow architecture. A first‐in first‐out stage in the pipeline derandomizes the random event arrival times. A subsequent stage in the pipeline uses an arctangent function to convert the sine and cosine pairs into linearized measures of event time. These are subtracted to yield start–stop time interval sizes for individual photoevents. The minimum start–stop interval is 50 ns, set primarily by the cycle time. Because the same processing is employed for the start and stop events, a large class of potential error and drift phenomena are eliminated. The digitizer provides an accurate way to decode the outputs of delay line detectors, offering high event throughput and extremely good long‐term timing accuracy. As a side benefit, the pipeline data flow architecture permits simple breadboarding and low‐throughput testing of the system stages with the arctangent work implemented in a personal computer. This arrangement is also very convenient for logging diagnostic evaluation data. The same front‐end and data flow architecture is directly applicable to very high‐speed applications where the event processing is implemented in a digital signal processor.

ISSN:0034-6748    

DOI:10.1063/1.1144540

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A single‐mode, frequency‐stabilized LNA (lanthanum neodymium magnesium hexaluminate) ring laser developed for application in optical pumping and optical manipulation of He(2 3S) metastable atoms is described. This laser routinely provides output powers ≳300 mW at 1.083 &mgr;m when pumped with 5 W from an argon‐ion laser.

ISSN:0034-6748    

DOI:10.1063/1.1144541

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An intense supersonic beam of atomic fluorine has been generated using nozzles fabricated from single‐crystal CaF2and MgF2. The latter material has been tested up to 1000 °C with no observable damage. This is ≳250 °C hotter than previously achieved, increasing the atomic beam intensity by ≳5×.

ISSN:0034-6748    

DOI:10.1063/1.1144542

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An inexpensive regulator circuit for high‐voltage but low‐current applications, such as biasing electrodes for the manipulation of charged‐particle beams, is described. Using multiple regulator circuits running in parallel, numerous outputs can be produced from a single high‐voltage supply, resulting in significant cost savings.  

ISSN:0034-6748    

DOI:10.1063/1.1144543

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The reliable operation of a spark gap at 300 Hz pulse repetition frequency by rotating a suitably configured dielectric plate between its electrodes is reported. The triggering of the spark gap has been achieved by the use of an optical sensor.  

ISSN:0034-6748    

DOI:10.1063/1.1144544

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

As the time duration of an electromagnetic pulse becomes shorter the bandwidth of the pulse increases. This presents a problem in the selection of a frequency for the calculation of the effectiveEfield. This paper discusses a method for calculating the effectiveEfield of a short electromagnetic pulse.  

ISSN:0034-6748    

DOI:10.1063/1.1144480

出版商:AIP    

年代:1994

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1145200

出版商:AIP    

年代:1994

数据来源: AIP