摘要:

A direct digital synthesis technique has been used to accomplish rapid changes in transmitter frequency in NMR without loss of phase coherence.

ISSN:0034-6748    

DOI:10.1063/1.1134392

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We describe an automated calorimetry system for measuring heat capacity in the range 1–35 K. The system employs an on‐line computer for signal averaging and data reduction and is capable of performing rapid, accurate specific heat measurements on very small (1–100 mg) samples.

ISSN:0034-6748    

DOI:10.1063/1.1134393

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method to analyze multipole fields formed with flat‐face electrodes by using conformal mapping is described. Quadrupole fields of various parameter values which define the electrode shape are analyzed by this method, and the optimum parameter values for making distortion components of the field minimum are obtained. This result is also useful in designing the shapes of magnetic quadrupoles.

ISSN:0034-6748    

DOI:10.1063/1.1134394

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A high‐power, cw microwave magnetron is used to produce a discharge in a gas column flowing at high velocity. The large atom production rate obtained makes this a valuable atom source for chemical laser application.

ISSN:0034-6748    

DOI:10.1063/1.1134395

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A one‐dimensional x‐ray telescope of the Kirkpatrick–Baez design is described. The instrument consists of a grazing‐incidence x‐ray telescope and a multiwire proportional counter. The optics were provided with a gold reflecting surface to yield an energy response from below 0.25 to above 4.0 keV. The angular resolution of the system is 6′×9.5° over a 1.1°×9.5° field of view.

ISSN:0034-6748    

DOI:10.1063/1.1134402

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A tunable cw laser has been used to selectively remove either of the two metastable species,3P0,2, which are initially present in a neon metastable beam. The method is applicable to other rare gases and provides the opportunity for separate investigation of effects due to atoms in either the3P0or3P2state.

ISSN:0034-6748    

DOI:10.1063/1.1134403

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The relationships of microwave Hall mobilities and microwave conductivities in a semiconductor, placed at the center of a dual mode TE111cavity, are expressed in terms of the loaded and unloaded voltage reflection coefficients, the sample and the cavity dimensions, the ratio of the output power to the input power of the cavity, and the magnetic field. Scattering

ISSN:0034-6748    

DOI:10.1063/1.1134404

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An experimental technique for the measurement of Hall mobilities at microwave frequencies is described. The design of a dual mode TE111cavity is described, and a comparison among receivers for the detection system is given. A procedure for tuning the cavity for orthogonality, degeneracy, and equal quality factors is presented. With a superheterodyne receiver and a well designed gold plated, probe‐coupled cavity, the minimum detectable mobility is 0.07 cm2/V⋅sec for a high conductivity sample.

ISSN:0034-6748    

DOI:10.1063/1.1134405

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The counting rate dependent shift of pulse height distributions in cylindrical (flow) proportional counters has been studied. The effects of various counter tube constructional and operational parameters on this shift were investigated. Certain of these parameters also introduce time dependent features into the shift phenomenon. Space charge effects are not major causes of the shifts except under extreme operating conditions. Direct intervention of adsorbed molecules or molecular ions in the multiplication process may also be eliminated as major factors. It is hypothesized that the primary mechanism for the shift is the buildup on the anode wire of a loosely adherent sheath of polarizable molecules or molecular fragments of quench gas, which effectively increases the diameter of the anode wire, thereby decreasing the gas gain for a fixed applied voltage. The equilibrium thickness of the sheath is a function of counting rate, photon energy, gas gain, gas pressure, and wire diameter and surface condition. Calculation of the thickness of this sheath gives a reasonable result. By proper choice of anode wire diameter, material, and heat treatment, the shift can be made negligible. There is also some hope that a proper choice of quench gas can also reduce or eliminate the effect.

ISSN:0034-6748    

DOI:10.1063/1.1134406

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We have devised a new method for determining the heating effects of the electron beam on metal foils in a transmission electron microscope. Thin specimens of tin, lead, and zinc were melted in the electron microscope using the combination of heat from the electron beam in ’’normal’’ usage and a previously calibrated heating cartridge. The temperature rise due to the electron beam heating was the difference between the melting temperature of the metal foil and the ’’temperature contribution’’ of the heating element. For a given beam current the temperature rise of the metal foils due to be beam was determined to within ±10 °C using this technique. This technique appears to be valid provided the beam current is kept at the same constant value during calibration and operation.

ISSN:0034-6748    

DOI:10.1063/1.1134407

出版商:AIP    

年代:1975

数据来源: AIP