摘要:

The use of microchannel electron multipliers in laboratory instrumentation as a detecting system coupled to an x‐uv monochromator or spectrograph, or to a low energy particle spectrometer, corresponds to a particular class of operation in which the detectors are exposed to a very low average input current and to stringent operational conditions, imposed by the instrument concept. It is shown in this paper that frequent vacuum breakings in the system containing the multiplier are not harmful to the stability of its performance. The monitoring of the strip current vs the applied potential is shown to be the simplest and most efficient way of assessing the state of the detector, as, in this particular regime of operation, it is necessary to follow a precise operating procedure to limit spurious secondary effects correlated to the water vapor contamination of its emissive surface.

ISSN:0034-6748    

DOI:10.1063/1.1686769

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The changes in the gain and strip current characteristics of a microchannel electron multiplier which are caused by outgassing due to ir baking were investigated. Baking at 200°C caused only reversible outgassing. Baking at 250°C for six hours produces irreversible changes. Detailed descriptions of the experimental set up and the controls performed during the baking are given.

ISSN:0034-6748    

DOI:10.1063/1.1686770

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Design, construction, and performance of a solid state marginal oscillator for detection of ions in ion cyclotron resonance experiments are described. Special design features include noise matching a high Q tank to an FET preamplifier which sacrifices voltage level for improved S/N ratio, amplitude limiting to remove noise from the feedback signal, and impedance matching the feedback resistor to the tank to minimize phase shift, parasitic capacitive coupling, and tank loading. A simple electrical circuit which simulates power absorption by ions for performance testing and comparison among marginal oscillators for icr applications is also described.

ISSN:0034-6748    

DOI:10.1063/1.1686771

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Two types of calorimeters developed to measure energy in high‐power laser pulses are described: solid‐absorber calorimeters, of designs capable of extension to large diameters, and stirrred‐liquid calorimeters. Results are given for measurements of 1.06 &mgr; pulses at power densities up to about 1011W cm−2. The calorimeters are calibrated by electrical heating; together with measurements of the specular reflection and thermal radiation losses, this permits performance of absolute measurements to an accuracy of better than 1%.

ISSN:0034-6748    

DOI:10.1063/1.1686772

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A two‐stage voltage divider having a voltage measuring capability on the order of 100 kV and a risetime of 250 psec has been used to measure submicrosecond pulses on a pulsed electron accelerator. The divider uses a copper sulphate solution high‐voltage divider, and a secondary divider made of carbon composition resistors. Measurements have been made indicating the solution divider is useful with fields of 30 kV/cm and with subnanosecond risetimes.

ISSN:0034-6748    

DOI:10.1063/1.1686773

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A device is described for measuring the time dependent, volume averaged density of a decaying plasma in a large multimode microwave cavity such as is typically used for plasma confinement studies. The technique consists of filling the cavity with microwave radiation and digitally counting the modes observed with a detector as the plasma decays. Since each mode corresponds statistically to a constant density increment, the density at a given time is proportional to the number of modes that appear as the density decays to zero. Experiments in a toroidal octopole show good agreement with density as measured by other methods.

ISSN:0034-6748    

DOI:10.1063/1.1686774

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An improved laser‐schlieren system for the measurement of shock‐wave velocities has been developed which employs a single detector. Calibration of multiple detectors has been obviated. The system has been shown to yield, in addition to the shock‐wave velocity, additional information on the arrival time of the contact surface. Shock‐tube performance is compared to the predictions of Mirels' theories.

ISSN:0034-6748    

DOI:10.1063/1.1686775

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new technique has been developed to produce an intense positron source by making use of the11B(p,n)11C reaction. Positrons with well‐defined low energies have been observed emerging from the irradiated boron target itself without any additional moderating materials. A description of the apparatus used to produce the11C and to detect the low energy positrons is given.

ISSN:0034-6748    

DOI:10.1063/1.1686776

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A ``dip‐stick'' for holding capsule type platinum thermometers during an ice point determination is described. It appears easy to obtain an ice point stable to ±0.0005°C over many hours.

ISSN:0034-6748    

DOI:10.1063/1.1686777

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Diffusion bonding of gold to gold was investigated at low pressures and temperatures. Mercury, indium, and gallium were the diffusing species; tests as a function of several surface finishes were made. Bonds that exceeded the yield point of gold were obtained with mercury.

ISSN:0034-6748    

DOI:10.1063/1.1686778

出版商:AIP    

年代:1974

数据来源: AIP