摘要:

Electromagnetically driven flux compression (EMC) devices are developed with a view to applications for experiments with megagauss fields, in particular for a study of magnetic bremsstrahlung. Fields of the order of 1.3 MG are reproducibly generated by means of a 27 kJ capacitor bank of uncomplicated design. In order to optimize the EMC configurations, extensive experimental parameter studies have been undertaken by varying the geometrical dimensions, the foil material, the coil design, and the capacitor bank voltage. A comparison is made between EMC and other methods for the generation of megagauss fields.

ISSN:0034-6748    

DOI:10.1063/1.1684228

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A new technique has been devised to examine deformation microstructures of thin walled metal cylinders subjected to internal impulsive loading. The cylinders are strained finite amounts but are not carried to fracture. The stressing device uses a rigid stainless steel cell as a container and an explosively driven Lucite core to produce specimens of metals and alloys that have undergone a high strain rate expansion and are in a form amenable to direct observation by transmission electron microscopy. The total strain in the specimen is controlled and loading conditions may be reproduced for comparison of different materials. This approach is particularly well suited to the detailed investigation of explosive forming processes and shock hardening phenomena in cylindrical bodies.

ISSN:0034-6748    

DOI:10.1063/1.1684285

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The pulse height to clock pulse converter is an electronic digital integrator and its application for gamma ray dosimetry (gamma ray pulse dosimeter) has been reported recently. In the present study, a new integration method was adopted for the pulse height to clock pulse converter in addition to its transistorization. The results of its application for neutron dosimetry are also described.

ISSN:0034-6748    

DOI:10.1063/1.1684231

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A differential generating voltmeter was developed to operate with the electrostatic accelerator of the Universidade de Sa˜o Paulo. It has an energy spread of 0.2% for 1 MeV protons. The calibration reproducibility of the system is 0.15% over all the accelerator voltage range and for a time period of eight months. The linearity of the energy calibration curve is 0.1% over the whole voltage range of the accelerator.

ISSN:0034-6748    

DOI:10.1063/1.1684262

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A spiral type continuous channel multiplier was used for pulse counting heavy positive ions. The shape of the output pulses was studied. The pulse risetime was found to be very long and composed of numerous after‐pulsing as revealed by the ``staircase'' appearance of the pulse. As a consequence, the count rate capability is greatly hampered. Detection of the positive ions by a catcher foil and collection of the secondary electrons lead to a smooth pulse clean of any after‐pulsing and to a greatly improved count rate capability.

ISSN:0034-6748    

DOI:10.1063/1.1684265

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Operation of a field emission scanning microscope in a secondary electron mode is described. The microscope uses only a field emission electron gun without auxiliary lenses and a silicon surface barrier detector to detect the secondary electron current. Resolution of 100 to 200 Å with beam currents of 10−11to 10−10A is reported. Micrographs of a variety of specimens are shown.

ISSN:0034-6748    

DOI:10.1063/1.1684266

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This paper presents a design for a small superconducting magnet. The magnet is used for dip experiments into a storage Dewar with the access tube removed from the neck. The solenoid is corrected by means of two extra coils wound on the outside. Correction coils increased the usable volume over which the field is uniform to 0.1% by a factor of about 50. The magnet is uniform to 0.1% over the full radial bore and for almost 2 cm along the axis. All the information necessary to wind the magnet is given; the magnet reported was wound by novices. The total cost of the magnet was about $20; the magnet achieved more than 15 kG.

ISSN:0034-6748    

DOI:10.1063/1.1684267

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This paper describes a means of signal processing specifically designed for use with electron microprobe analyzers. The method of ``pulse rate analysis'' (PRA) can, however, be applied to many areas of data gathering and signal processing where it is desired to suppress randomly distributed background noise pulses. A variable rate control allows selection of the incoming pulse rate required to produce an output signal at the display unit. The pulse rate range has been optimized for microprobe work and covers a PRF of 10 Hz to 40 kHz. A binary scaling arrangement extends this range by a factor of 2 or 4 while providing anS‐fold interval distribution. Improvement of up to 50:1 has been observed in the apparent signal‐to‐noise (S/N) ratio.

ISSN:0034-6748    

DOI:10.1063/1.1684268

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A dissimilarity in the risetime distribution of 8 to 10 MeV pulses from a 22.9 by 30.5 cm NaI(Tl) crystal due to fast neutrons and those due to gamma rays of equivalent energy has been observed. The time spectra were obtained using low and high level discriminators triggering at 100 keV and 2.5 MeV, respectively. The NaI (Tl) crystal was viewed by six matched RCA 4524 bialkali photomultiplier tubes. The time resolution of this system (using a small plastic scintillator to obtain one time reference) for 4.43 MeV gamma rays using leading edge timing is 2.5 nsec. The fast neutrons undergo inelastic collisions within the crystal prior to capture. The mean time between collisions for 3 MeV neutrons in NaI is 2.8 nsec; thus, the time interval between the two discriminators is longer for a typical fast neutron than for a gamma ray of equivalent energy. This results in a degradation of the time spectrum due to the fast neutrons. The 8 to 10 MeV gamma ray risetime distribution is symmetric, having a time resolution (FWHM) of 2.75 nsec. The neutron risetime distribution has a tail on the side corresponding to longer time intervals between the two discriminator outputs. It is shown that it is possible to reduce the number of pulses due to neutrons in the 8 to 10 MeV region by ⅓ by setting a time window. Estimates of an increased capability to discriminate through the use of a pulsed accelerator and a beam pickoff (thereby allowing the time interval between neutron emission and first inelastic scattering to be observed) are presented.

ISSN:0034-6748    

DOI:10.1063/1.1684269

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A spark cutter design which is both versatile and very inexpensive is reported. Complete information on all major parts is included. A novice could build the machine in about four days using the information from the note. The spark cutter reported has been used to cut single crystals of a wide variety of metals as well as to do sophisticated machining jobs.

ISSN:0034-6748    

DOI:10.1063/1.1684270

出版商:AIP    

年代:1970

数据来源: AIP