摘要:

The production of simple and rugged photon‐counting detector arrays has been made possible by recent improvements in the performance of the microchannel array plate (MCP) and by the parallel development of compatible electronic readout systems. The construction of proximity‐focused MCP arrays of novel design in which photometric information from (n×m) picture elements is read out with a total of (n+m) amplifier and discriminator circuits is described. Results obtained with a breadboard (32×32) ‐element array employing 64 charge‐sensitive amplifiers are presented, and the application of systems of this type in spectrometers and cameras for use with ground‐based telescopes and on orbiting spacecraft discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134124

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A series of measurements were performed on two groups of transverse‐configuration Hall effect sensors, each group consisting of devices available from a particular commercial supplier. The Hall voltage output of the probes was measured as a function of magnetic field to 18 T at temperatures of 300, 77, and 1.5–4.2 K; at the same time, the probes were subjected to a program of abrupt thermal cycling and magnetic field cycling. With the aid of computer analysis of the data the following conclusions could be drawn: (1) the outputs of one group of probes were linear with magnetic field within a worst‐case value of ∼±1% up to 8 T, and for the second group, to within ±0.5% up to 8 T and ±1.4% up to 18 T; (2) statement (1) was true for any of the selected temperatures; in general, variations of sensor output with temperature proved to be an unimportant factor; (3) the degree of measurement repeatability between thermal cycles varied somewhat from probe to probe within a group, but was significantly different between the two groups; (4) for a limited number of thermal cycles (∼25), it is clear that a simple calibration procedure would suffice to maintain a field measurement accuracy of ±0.2% up to 14 T, at least for one group of probes.

ISSN:0034-6748    

DOI:10.1063/1.1134125

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Two methods, utilizing the optical detection of the ground state paramagnetism of ions in solids for field calibration and measurement of the homogeneity of superconducting magnets at liquid helium temperature, are described and demonstrated. This technique has an accuracy comparable to that of NMR and has advantages in simplicity and in measuring homogeneity.

ISSN:0034-6748    

DOI:10.1063/1.1134126

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A double‐beam interferometer has been designed for detecting changes of refractive index in transparent liquids associated with the absorption of ionizing radiation energy, due to short electron beam pulses from an accelerator. The response time of the interferometer is less than 0.2 &mgr;sec, and refractive index changes of the order of 10−7can be measured, corresponding to a temperature change of ∼10−3 °C and an absorbed dose in water of ∼350 rad. The interferometer can be used as either a real‐time or integrating radiation dosimeter, if the temperature coefficient of the refractive index (dn/dT) is known for the irradiated liquid in the temperature region of interest.

ISSN:0034-6748    

DOI:10.1063/1.1134127

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A temperature controlled centrifugal casting technique is used to quickly and reproducibly prepare thin polymer films which are suitable for transmission infrared spectroscopy. Films prepared by this method are shown to be without preferential orientation.

ISSN:0034-6748    

DOI:10.1063/1.1134128

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An apparatus which combines a liquid4He Dewar with an ultrahigh vacuum system used for LEED or AES surface analysis and ultrathin film deposition is described. A linear motion bellows seal allows the substrate for film deposition to be moved out of the radition shields, which makes ion bombardment cleaning possible. A He gas heat exchanger between the substrate holder and He reservoir provides a wide variation of temperatures.Insitumeasurements of superconducting transition temperatures below 2 K have been made with this apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1134129

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A simple solid state circuit was used to drive GaAs injection lasers by fast (∼100 nsec) square pulses of variable amplitude (0–25 A). The amplitudes of the current pulses and the corresponding emitted light pulses were measured by a dual peak detector circuit. Using these circuits we were able to plot automatically the current vs light curve and determine the threshold current of the laser diodes.

ISSN:0034-6748    

DOI:10.1063/1.1134130

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A rectangular slit jet impactor has been designed and fabricated for use as an airborne collector of supergiant aerosol particles. The width of the slit is variable, allowing the impactor size cutoff to be set so that only particles greater than a determined size are collected. The jet convergence angle was made to be 53° 13′ to ensure that the width of the slit is always the same as the distance from jet mouth to the impaction substrate. Experimental calibration of the impactor indicates that this configuration gives excellent impaction characteristics.

ISSN:0034-6748    

DOI:10.1063/1.1134131

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We describe a digitally programmable impedance bridge, used here for low‐temperature resistance thermometry, and a compatible digital programming and data logging interface. The bridge employs a commercial programmable ratio transformer to achieve high resolution with minimum circuit complexity. We measure the ratio of the resistances of a carbon thermometer and a fixed reference resistor, both near 2 K, with a resolution limited by Johnson noise in the resistors. The bridge circuit described here is suitable for a variety of programmable or self‐balancing impedance measurements.

ISSN:0034-6748    

DOI:10.1063/1.1134132

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Double chamber ovens having an additional gas feed line which allows generation of seeded K and KF beams with a variety of gases are described. The seed species partial pressure is kept at ?1 Torr, and the total pressure is varied up to 800 Torr. The beams are skimmed with heated nickel skimmers. The velocity and speed ratio of the beams and their dependence on seeding gas identity and pressure are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134133

出版商:AIP    

年代:1975

数据来源: AIP