- Email: [email protected]
Generation and extraction of microsecond intense relativistic electron beams
Classified abstracts 1629-1638
the steps taken to reduce noise and make the toroids temperature and radiation resistant. P J Tallerico, J Vac Sci Technol, 12 (6), 1975. 1200-1202. 33 1629. A T R I - - A Tesla-transformer-type electron-beam accelerator. (USA) An electron-beam transformer accelerator is described. Its high voltage terminal rises up to 1.2 MV with an input of 18 kV. The maximum electron-beam current is 16 kA; the pulse length is about 20 nsec. Aluminized Mylar anodes and foilless anodes are used. With foilless anodes the repetition rate is at present 3 pulses/sec. Pulse shape details are given and discussed to understand the behavior of the machine and its output characteristics. An improvement program is also presented. (Italy) ! Boscolo et al, J Vac Sci Technol, 12 (6), 1975, 1194-1196. 33 1630. Generation and extraction of microsecond intense relativistic electron beams. (USA) The Physics International Pulserad 1140 has been modified so that a pulse length of 1.7 t~sec can be obtained with a beam energy of 50 kJ. This modification involves substituting a pulse-forming network for the conventional Blumlein. This long-pulse generator has been used to study diode behavior on l ,usec time scales. The dependence of impedence on voltage and anode-cathode spacing is discussed here. A semiempirical model has been developed. The diode time history and closure velocity are discussed in terms of this model. R Schneider et al, J Vac Sci Technol, 12 (6), 1975, 1191-1193. 33 1631. 15-kJ LC generator: Low inductance device for a 100-GW pulsed electron accelerator. (USA) The design and construction of a 15-kJ LC generator is described. This type of generator is used for its low inductance compared with more conventional Marx generators. The generator described consists of 20 capacitors rated at 80 kV, 5 reversing switches, and l extrahigh-voltage transfer switch. The generator was built as a primary store for a high current, high power (300 kA, 100 GW) field-emission electron-beam generator. N W Harris and H I Milde, J Vac Sci Technol, 12 (6), 1975, I 183-1190.
34. ELECTRONICS A N D HIGH A L T I T U D E PHYSICS A N D TECHNOLOGY 34 1632. Evaluation of a LaB6 cathode electron gun. (GB) The brightness of the lanthanum hexaboride, LAB6, cathode electron gun of the Stereoscan S-4 scanning electron microscope has been evaluated. This gun is an indirectly heated Broers type of LaB6 gun design, and the several variables which affect its brightness have been evaluated using a cage device for the brightness measurements. The results indicate that when proper operating conditions are employed the LaB6 brightnesses are of the order of 15 to 20 times that of tungsten operated at 40 h life conditions, and that single crystal cathodes are more reliable for producing high brightnesses. (USA) J D Verhoeven and E D Gibson, JPhys E: Scient Instrum, 9 (1), 1976, 65-69. 34 1633. Electron-dispersion technique for observation of fast transient signals. (GB) It is shown that a single transient optical or electrical signal may be used to modulate an electron beam so that subsequent dispersion of the beam generates an output electrical signal similar to the input signal but lengthened in time. The design and performance of an instrument utilizing this principle to transform a 10 ns electrical signal are described. R D Prosser, JPhys E: Scient lnstrum, 9 (l) 1976, 57-59. 34 1634. Kitt Peak 60-cm vacuum telescope. (USA) Described is a major new tool for solar research, conceived and built during a time of budget restraint. The observation of magnetic and velocity (circulation) field structure on a synoptic basis and with diffraction-limited resolution is the aim. New optical features include the use of oversize mirrors and windows (to avoid thermal edge effects) and the placement of the coelostat feed outside the vacuum, mainly for economy. The site selected has prevailing winds that clear thermals from these mirrors. Test data in the form of the system
MTF and optical transmission, together with examples of full disk magnetograms and photoheliograms, show present performance capability. Measured MTF indicates a response of 0.2 at I sec of arc (whereas diffraction-limited response would be ~0.8). System transmission, including the accompanying spectrograph, is only 2-3700 (,~0.44-1.1 t~m). Thus, both the optical quality and efficiency are subject to improvement. W C Livingston et al, Appl Opt, 15 (I), 1976, 33-39. 34 1635. Study of a field-ionization source for microprobe applications. (USA) Operating parameters for a field-ionization source have bccn measured. Sensitivities of 5 × 10 -5 A sr - t torr - t were found at 77 K. Angular distributions are uniform near 0 = 0 ° and show the beam to be confined to 4- 20 ° . The beam signal-to-noise ratio was found to increase with increasing current. Calculations based on parameters of lenses in use indicate a resolution of 0.1/Lm at ~ 10-to A is possible. J H Orloff and L W Swanson, J Vac Sci Technol, 12 (6), 1975, 1209-1213. 34 1636. Secondary emission electron gun for high pressure molecular lasers. (USA) A new type of high voltage, large area electron gun is described. Ions are generated in a low pressure ion source, extracted by a grid, and accelerated by a - 1 3 0 kV continuously biased electrode. By secondary emission, these ions produce electrons which are accelerated toward the grid. They go through the ion source and an electron window (15 × 5 cm). Electron-beam density profiles display a good uniformity. The current density, limited only by the available power for the discharge, reaches presently l mA/cm 2. The advantages of this gun over others are moderate vacuum requirements and capability for both low current cw and high current pulsed beams with easy control at ground potential and small energy requirement. (France) D Pigaehe and G Fournier, J Vac Sci Technol, 12 (6), 1975, 1197-1199. 34 1637. OWL II pulsed-electron-beam generator. (USA) OWL is a water-dielectric line-type pulse generator capable of producing ~ 1 0 0 nsec electron beams with total energies of as much as 150 kJ. In its present form, OWL II consists of an oil-immersed, l/3-MJ Marx generator charging a 3.9--Q coaxial pulse-forming line which is series switched into either a two- or three-stage impedenee transformer. The output impedence is 1.9 or 1.1 .Q, depending upon which transformer is used, and nominal beam outputs in the two cases are 1.3 MV at 0.8 MA and 0.9 MV at 1.2 MA, respectively. The pulse width can be selected at either 60 or 120 nsec ( F W H M of power) by interchanging two available pulse lines. Shot-to-shot reproducibility in output of 4 - 2 ~ . with a mean electron energy ,~ 1.0 MeV is obtained with the 1.9 .O final transformer. A triggered multichannel water switch minimizes the risetime of pulses injected into the transformer section. G B Frazier, J Vac Sci Technol, 12 (6), 1975, 1183-1187. 34 1638. Some aspects of high-current relativistic electron-beam generation. (USA) Diode characteristics in two electron-beam generators, IT and ACE, are examined, with particular reference to the role of prepulse conditions. The advantages and limitations of field-enhanced edge emitters are discussed. In both low- and high-current-density applications, a stable impedence-time history is shown to be associated with a band of prepulse voltage which is a function of both its time variation and driving impedance. Above this band rapid impzdance collapse occurs, and below it long current switch-on times are experienced. This behavior is postulated to be dependent upon cathode plasma formation and growth during prepulse and early main pulse phases. The results of a preliminary investigation into the controlled use of prepulse for high-current-density beam production from fieldenhanced edges are examined. The characteristics of hollow cylindrical cathodes operating in pinched mode are shown to depend on prepulse conditions. In particular, the transfer of finite energy (of order tens of millijoules) to the diode during the prepulse phase is shown to be desirable for rapid establishment of the required diode impedance in the main pulse phase. (GB) D W Furster, J Vac Sci Technol, 12 (6), 1975, 1177-1182.
215
the steps taken to reduce noise and make the toroids temperature and radiation resistant. P J Tallerico, J Vac Sci Technol, 12 (6), 1975. 1200-1202. 33 1629. A T R I - - A Tesla-transformer-type electron-beam accelerator. (USA) An electron-beam transformer accelerator is described. Its high voltage terminal rises up to 1.2 MV with an input of 18 kV. The maximum electron-beam current is 16 kA; the pulse length is about 20 nsec. Aluminized Mylar anodes and foilless anodes are used. With foilless anodes the repetition rate is at present 3 pulses/sec. Pulse shape details are given and discussed to understand the behavior of the machine and its output characteristics. An improvement program is also presented. (Italy) ! Boscolo et al, J Vac Sci Technol, 12 (6), 1975, 1194-1196. 33 1630. Generation and extraction of microsecond intense relativistic electron beams. (USA) The Physics International Pulserad 1140 has been modified so that a pulse length of 1.7 t~sec can be obtained with a beam energy of 50 kJ. This modification involves substituting a pulse-forming network for the conventional Blumlein. This long-pulse generator has been used to study diode behavior on l ,usec time scales. The dependence of impedence on voltage and anode-cathode spacing is discussed here. A semiempirical model has been developed. The diode time history and closure velocity are discussed in terms of this model. R Schneider et al, J Vac Sci Technol, 12 (6), 1975, 1191-1193. 33 1631. 15-kJ LC generator: Low inductance device for a 100-GW pulsed electron accelerator. (USA) The design and construction of a 15-kJ LC generator is described. This type of generator is used for its low inductance compared with more conventional Marx generators. The generator described consists of 20 capacitors rated at 80 kV, 5 reversing switches, and l extrahigh-voltage transfer switch. The generator was built as a primary store for a high current, high power (300 kA, 100 GW) field-emission electron-beam generator. N W Harris and H I Milde, J Vac Sci Technol, 12 (6), 1975, I 183-1190.
34. ELECTRONICS A N D HIGH A L T I T U D E PHYSICS A N D TECHNOLOGY 34 1632. Evaluation of a LaB6 cathode electron gun. (GB) The brightness of the lanthanum hexaboride, LAB6, cathode electron gun of the Stereoscan S-4 scanning electron microscope has been evaluated. This gun is an indirectly heated Broers type of LaB6 gun design, and the several variables which affect its brightness have been evaluated using a cage device for the brightness measurements. The results indicate that when proper operating conditions are employed the LaB6 brightnesses are of the order of 15 to 20 times that of tungsten operated at 40 h life conditions, and that single crystal cathodes are more reliable for producing high brightnesses. (USA) J D Verhoeven and E D Gibson, JPhys E: Scient Instrum, 9 (1), 1976, 65-69. 34 1633. Electron-dispersion technique for observation of fast transient signals. (GB) It is shown that a single transient optical or electrical signal may be used to modulate an electron beam so that subsequent dispersion of the beam generates an output electrical signal similar to the input signal but lengthened in time. The design and performance of an instrument utilizing this principle to transform a 10 ns electrical signal are described. R D Prosser, JPhys E: Scient lnstrum, 9 (l) 1976, 57-59. 34 1634. Kitt Peak 60-cm vacuum telescope. (USA) Described is a major new tool for solar research, conceived and built during a time of budget restraint. The observation of magnetic and velocity (circulation) field structure on a synoptic basis and with diffraction-limited resolution is the aim. New optical features include the use of oversize mirrors and windows (to avoid thermal edge effects) and the placement of the coelostat feed outside the vacuum, mainly for economy. The site selected has prevailing winds that clear thermals from these mirrors. Test data in the form of the system
MTF and optical transmission, together with examples of full disk magnetograms and photoheliograms, show present performance capability. Measured MTF indicates a response of 0.2 at I sec of arc (whereas diffraction-limited response would be ~0.8). System transmission, including the accompanying spectrograph, is only 2-3700 (,~0.44-1.1 t~m). Thus, both the optical quality and efficiency are subject to improvement. W C Livingston et al, Appl Opt, 15 (I), 1976, 33-39. 34 1635. Study of a field-ionization source for microprobe applications. (USA) Operating parameters for a field-ionization source have bccn measured. Sensitivities of 5 × 10 -5 A sr - t torr - t were found at 77 K. Angular distributions are uniform near 0 = 0 ° and show the beam to be confined to 4- 20 ° . The beam signal-to-noise ratio was found to increase with increasing current. Calculations based on parameters of lenses in use indicate a resolution of 0.1/Lm at ~ 10-to A is possible. J H Orloff and L W Swanson, J Vac Sci Technol, 12 (6), 1975, 1209-1213. 34 1636. Secondary emission electron gun for high pressure molecular lasers. (USA) A new type of high voltage, large area electron gun is described. Ions are generated in a low pressure ion source, extracted by a grid, and accelerated by a - 1 3 0 kV continuously biased electrode. By secondary emission, these ions produce electrons which are accelerated toward the grid. They go through the ion source and an electron window (15 × 5 cm). Electron-beam density profiles display a good uniformity. The current density, limited only by the available power for the discharge, reaches presently l mA/cm 2. The advantages of this gun over others are moderate vacuum requirements and capability for both low current cw and high current pulsed beams with easy control at ground potential and small energy requirement. (France) D Pigaehe and G Fournier, J Vac Sci Technol, 12 (6), 1975, 1197-1199. 34 1637. OWL II pulsed-electron-beam generator. (USA) OWL is a water-dielectric line-type pulse generator capable of producing ~ 1 0 0 nsec electron beams with total energies of as much as 150 kJ. In its present form, OWL II consists of an oil-immersed, l/3-MJ Marx generator charging a 3.9--Q coaxial pulse-forming line which is series switched into either a two- or three-stage impedenee transformer. The output impedence is 1.9 or 1.1 .Q, depending upon which transformer is used, and nominal beam outputs in the two cases are 1.3 MV at 0.8 MA and 0.9 MV at 1.2 MA, respectively. The pulse width can be selected at either 60 or 120 nsec ( F W H M of power) by interchanging two available pulse lines. Shot-to-shot reproducibility in output of 4 - 2 ~ . with a mean electron energy ,~ 1.0 MeV is obtained with the 1.9 .O final transformer. A triggered multichannel water switch minimizes the risetime of pulses injected into the transformer section. G B Frazier, J Vac Sci Technol, 12 (6), 1975, 1183-1187. 34 1638. Some aspects of high-current relativistic electron-beam generation. (USA) Diode characteristics in two electron-beam generators, IT and ACE, are examined, with particular reference to the role of prepulse conditions. The advantages and limitations of field-enhanced edge emitters are discussed. In both low- and high-current-density applications, a stable impedence-time history is shown to be associated with a band of prepulse voltage which is a function of both its time variation and driving impedance. Above this band rapid impzdance collapse occurs, and below it long current switch-on times are experienced. This behavior is postulated to be dependent upon cathode plasma formation and growth during prepulse and early main pulse phases. The results of a preliminary investigation into the controlled use of prepulse for high-current-density beam production from fieldenhanced edges are examined. The characteristics of hollow cylindrical cathodes operating in pinched mode are shown to depend on prepulse conditions. In particular, the transfer of finite energy (of order tens of millijoules) to the diode during the prepulse phase is shown to be desirable for rapid establishment of the required diode impedance in the main pulse phase. (GB) D W Furster, J Vac Sci Technol, 12 (6), 1975, 1177-1182.
215