For short duration plasmas, such as high-current theta and zeta pinches, it is necessary to use very short exposures to photograph the plasmas. These plasmas are very luminous, so there is sufficient light for sub-microsecond exposures. Several types of cameras were used. These include Kerr cell, image converter, framing and streak cameras. The Kerr cell camera takes only one picture, while the framing camera can take 25 pictures at the rate of 4x 10'6 per second. Examples of plasma photography will be shown, and the unique advantages and problems with each type of camera will be discussed.
This paper describes the design and operation of two photographic systems developed for use in recording data on small objects traveling at high speeds. The first system, developed primarily for measuring pitch and yaw, uses a single first surface mirror; the second, which records five images for 360° viewing of objects in flight, uses dual first-surface mirrors. Also described are two high-intensity lighting systems. One for use in obtaining photographic data during very short exposure times; the other for use with synchroballistic techniques.
This paper contains the results of several investigations conducted by the author with photoelastic circular cylindrical shells under axial compression. The onset of instability and the subsequent buckling process have been analyzed using high speed photography to record change in the photoelastic isoclinic patterns. Both qualitative and quantitative results are presented concerning the inception of buckling which have never been achieved by other means. The application of high speed photography to the photoelastic analysis of some structural stability problems is demonstrated and results compared with reflected light techniques and mechanical measurements.
The technique of image-dissection is one of many methods developed for photographically recording high speed phenomena. Patented by Kanolt in 1912, the principle involves dividing an image into a large number of small elements. These lines or dots are deposited on the recording medium with spaces between them which are large as compared to the element size. All that is then necessary is to displace subsequent images a distance equal to the size of one element before depositing their respective elements on the emulsion. High recording rates are achieved since the displacement of each image is quite small.
Extremely short and intense bursts of X-rays, light or electrons can be obtained from a recently developed electron accelerator. Thus high-speed photography is made more versatile since the type of radiation which best portrays a particular event can be selected. The basic system, from which the electron beam can be extracted for direct use or converted into an intense pulse of X-rays by bremsstrahlung, was described at the 8th Congress of High-Speed Photography; since that time light generating capability has been added by the development of semiconductor targets which convert the electron beam energy into Super Radiant Light (SRL).
A technique has been developed to determine the exact time a high speed projectile contacts a target to initiate an impact event. A high speed photograph is taken of the projectile just prior to impact. The time the photograph is taken is used in conjunction with the known projectile velocity and the projectile-target distance as measured from the photograph to determine initial contact time. The system is assured of being accurate within its time resolution when it operates correctly. Comparisons between this unit and more conventional impact sensors that use switch closures or impact flashes to sense impacts were made. Results indicate that the conventional sensors can be triggered improperly by finely divided debris slightly preceding the high speed projectiles.
An inexpensive digital film reader has been developed which can automatically record x and y coordinates of manually located points within a 2.5 cm x 2.5 cm area to within 20μ. The reader consists of a projection microscope with an instrumented movable stage. Positions of images on films clamped to the stage are determined by moving the stage until the target image point falls under a cross hair on the projection screen. Coordinates of the stage position are sensed with a digital voltmeter. The voltmeter drives a keypunch which records film position data in a form compatible with computer processing.
Although controlled rain erosion testing is one of many types of captive dynamic testing that is carried out for missile and space vehicle systems at the Holloman High Speed Track, it is unique in that the photographic recording of this artificial rain and its effects offer unusual problems not encountered in ordinary sled testing. The 6,000 foot rain test section normally used produces an artificial rain with a mean drop diameter of 1.5mm, and has controllable rain drop concentration outputs plus special nozzles and tanks for isolated rain simulations. Sleds traveling at speeds up to Mach 5.5 have carried various test items through this environment so that scientists can study the effects of the rain on test items at various stations along the sled path as well as the total erosion effects after the vehicles are recovered. Detailed photographs of the test object while in the environment are best recorded by synchroballistic techniques. By sampling at intervals along the path, progressive deterioration can be recorded with space-time correlations as the test item passes through the rain field. Aerodynamic characteristics are recorded using photographic shadowgraph techniques. Engineering and general surveillance data is provided by high speed cameras and various lighting techniques.