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RSS1992 Vol. 04, No. 01
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1992,
04: 5-14.
Abstract:
The Heavy Ion Research Facility of Lanzhou (HIRFL) consists of ion sources, injector Sector Focusing Cyclotron (SFC) and main accelerator Separated Sector Cyclotron (SSC). The beam produced by the ion sources is pre-accelerated by injector SFC, and injected into main accelerator SSC, after passing through the former beam line. Then, the beam is accelerated to the maximum energy and transported to the experimental terminals through the post beam lines. In this paper, the construction process, bean performances and the main structures of HIRFL are introduced. Then the beam commissioning process, the method and the operation status for SSC and the beam lines are described. At last, this paper discusses extensive applied prospects for HIRFL.
The Heavy Ion Research Facility of Lanzhou (HIRFL) consists of ion sources, injector Sector Focusing Cyclotron (SFC) and main accelerator Separated Sector Cyclotron (SSC). The beam produced by the ion sources is pre-accelerated by injector SFC, and injected into main accelerator SSC, after passing through the former beam line. Then, the beam is accelerated to the maximum energy and transported to the experimental terminals through the post beam lines. In this paper, the construction process, bean performances and the main structures of HIRFL are introduced. Then the beam commissioning process, the method and the operation status for SSC and the beam lines are described. At last, this paper discusses extensive applied prospects for HIRFL.
1992,
04: 15-32.
Abstract:
The project of RF superconducting cavities have been started at Peking University since 1988 and the progress has been obtained. The peparation and procedure for RF super-conducting experiments at low temperature are described in detail. RF superconducting experiments, microwave measurements, phase lock technique, the surface treatment of cavity, computer simulation for cavity design, control, data acquire and processing with computer are summaried. So far, an accelerating field of 8.6MV/m was abtained with CW mode and Q0 of 6.5×108, 2.25K.
The project of RF superconducting cavities have been started at Peking University since 1988 and the progress has been obtained. The peparation and procedure for RF super-conducting experiments at low temperature are described in detail. RF superconducting experiments, microwave measurements, phase lock technique, the surface treatment of cavity, computer simulation for cavity design, control, data acquire and processing with computer are summaried. So far, an accelerating field of 8.6MV/m was abtained with CW mode and Q0 of 6.5×108, 2.25K.
1992,
04: 33-40.
Abstract:
After passing through the Wiggler and the 180°bend, the electron beam is transported to a time-dependent energy spectrometer. The 180°bend is designed for both achromatic and isochronous to suffice measurements of energy and temporal distributions or time-resolution of macropulses. The time-dependent energy spectra system contains four matching quadrupoles, a two-slit device, a slow-deflector sweep coil, a 90°analyzing magnet with horizontal and vertical focus, a quarts plate at the focal-plane of the magnet, a vidican TV camera with microchannel-plate intensifiers and a picture display system with a on-line micro-computer. Energy-resolution ratio of the spectrometer is large than 1000, while time resolution less than 60 ns.
After passing through the Wiggler and the 180°bend, the electron beam is transported to a time-dependent energy spectrometer. The 180°bend is designed for both achromatic and isochronous to suffice measurements of energy and temporal distributions or time-resolution of macropulses. The time-dependent energy spectra system contains four matching quadrupoles, a two-slit device, a slow-deflector sweep coil, a 90°analyzing magnet with horizontal and vertical focus, a quarts plate at the focal-plane of the magnet, a vidican TV camera with microchannel-plate intensifiers and a picture display system with a on-line micro-computer. Energy-resolution ratio of the spectrometer is large than 1000, while time resolution less than 60 ns.
1992,
04: 41-46.
Abstract:
In this paper, a pulsed magnetic field device for controlling relativistic electron beam energy flux and uniformity is described. The device consists of magnetic field power supply, coils, and drift chamber of electron beam. Pulsed magnetic field is produced by capacitors discharge through six triggered vacuum switches to coils. The total energy storege of capacitors is 180kJ and the charging voltage is l0kV. When charging voltage is 7kV, magnetic field is 1.81T, with a risetime of 8.38ms. Influence of target meterials on distribution of the field is also discussed, and synchronizer between FLASH-Ⅱ and the magnetic field is introduced. The magnetic field device has been applied to FLASH-Ⅱ accelerator, and the reliability of the device has been proved by more than two hundreds of shots.
In this paper, a pulsed magnetic field device for controlling relativistic electron beam energy flux and uniformity is described. The device consists of magnetic field power supply, coils, and drift chamber of electron beam. Pulsed magnetic field is produced by capacitors discharge through six triggered vacuum switches to coils. The total energy storege of capacitors is 180kJ and the charging voltage is l0kV. When charging voltage is 7kV, magnetic field is 1.81T, with a risetime of 8.38ms. Influence of target meterials on distribution of the field is also discussed, and synchronizer between FLASH-Ⅱ and the magnetic field is introduced. The magnetic field device has been applied to FLASH-Ⅱ accelerator, and the reliability of the device has been proved by more than two hundreds of shots.
1992,
04: 47-52.
Abstract:
This paper has made an analytical research of mode locking in a kind of free electron laser （FEL）, given the condition of mode locking in the FEL and obtained that due to mode coupling the number of active cavity modes will be reduced by a factor of mc, the low gain will be increased by a factor of mc, the rate of the exponential growth will be increased by a factor of mc1/3, mc is a ratio of the repetition frequency of the electron beam micropulses and the frequency interval of the cavity modes, mc=△vr/△vc.
This paper has made an analytical research of mode locking in a kind of free electron laser （FEL）, given the condition of mode locking in the FEL and obtained that due to mode coupling the number of active cavity modes will be reduced by a factor of mc, the low gain will be increased by a factor of mc, the rate of the exponential growth will be increased by a factor of mc1/3, mc is a ratio of the repetition frequency of the electron beam micropulses and the frequency interval of the cavity modes, mc=△vr/△vc.
1992,
04: 53-58.
Abstract:
Eemittance formulas of a beam in a linear induction accelerator, in consideration of the guiding magnetic field, self electro -magnetic field, accelerating field and the field induced by the accelerating gaps for a uniformly distributed beam are derived.
The conclusion is that the phenomena of beam break up for a 20MeV electron beam is not serious the linear wake field case.
Eemittance formulas of a beam in a linear induction accelerator, in consideration of the guiding magnetic field, self electro -magnetic field, accelerating field and the field induced by the accelerating gaps for a uniformly distributed beam are derived.
The conclusion is that the phenomena of beam break up for a 20MeV electron beam is not serious the linear wake field case.
1992,
04: 59-64.
Abstract:
This paper discusses mirror coating nonuniformities caused by geometrical constraints in the chamber used and their effects on polarization of light beams for enhanced metal coatings. Phase distortions of 1.06-μm laser beam and 0.5893-μ beacon beam have been calculated. Phase distortions with same signs have been abtained using a modified design.
This paper discusses mirror coating nonuniformities caused by geometrical constraints in the chamber used and their effects on polarization of light beams for enhanced metal coatings. Phase distortions of 1.06-μm laser beam and 0.5893-μ beacon beam have been calculated. Phase distortions with same signs have been abtained using a modified design.
1992,
04: 65-70.
Abstract:
Based on the research beam control for synthetic aperture systems in free space, this paper analyzes and discusses effects of phasing errors on beams combination. The phasing errors include piston errors, tilt errors and focus errors. The corresponding physical models are developed.Finally results of numerical computations are given.
Based on the research beam control for synthetic aperture systems in free space, this paper analyzes and discusses effects of phasing errors on beams combination. The phasing errors include piston errors, tilt errors and focus errors. The corresponding physical models are developed.Finally results of numerical computations are given.
1992,
04: 71-76.
Abstract:
The basic techniques for x-ray imaging are reviewed. The development of imaging devices in recent years and results obtained in ICF experiments with the devices are introduced.
The basic techniques for x-ray imaging are reviewed. The development of imaging devices in recent years and results obtained in ICF experiments with the devices are introduced.
1992,
04: 77-85.
Abstract:
A new explanation on the quadrature expression for small signal gain(SSG) in a variable parameter undulator is given in terms of Madey's theorem and analogy between the FEL and a phased antenna array and the spontaneous emission spectrum is derived. The generalization of the SSG expression from one to three dimensions is carried out and the effect on SSG due to the collimation error among the axes of the optical,electron beam and undulator is included as well. It shows at three dimensional effects will reduce SSG severely. The comparison with Boeing's FEL experiment is carried out and it is also pointed out that a better operation condition may be obtained if the first uniform section of the Boeing's undulator is reduced a little to make the optimum energy mismatch shifted towards zero.
A new explanation on the quadrature expression for small signal gain(SSG) in a variable parameter undulator is given in terms of Madey's theorem and analogy between the FEL and a phased antenna array and the spontaneous emission spectrum is derived. The generalization of the SSG expression from one to three dimensions is carried out and the effect on SSG due to the collimation error among the axes of the optical,electron beam and undulator is included as well. It shows at three dimensional effects will reduce SSG severely. The comparison with Boeing's FEL experiment is carried out and it is also pointed out that a better operation condition may be obtained if the first uniform section of the Boeing's undulator is reduced a little to make the optimum energy mismatch shifted towards zero.
1992,
04: 86-92.
Abstract:
Experiments on the establishing and vanishing time features of thermal lens in the moving or static absorbing cell, the beam diverging features at far field through the blooming cell, the comparision of the beam distortion features of nonuniform absorption with that of uniform absorption are reported.
Experiments on the establishing and vanishing time features of thermal lens in the moving or static absorbing cell, the beam diverging features at far field through the blooming cell, the comparision of the beam distortion features of nonuniform absorption with that of uniform absorption are reported.
1992,
04: 93-100.
Abstract:
In this paper, we present the formula of a simplified electrostatic field configuration of a inclined field tube with variable gradient at the constraint conditions so called "zero-entrance and zero-exit" .
In this paper, we present the formula of a simplified electrostatic field configuration of a inclined field tube with variable gradient at the constraint conditions so called "zero-entrance and zero-exit" .
1992,
04: 101-106.
Abstract:
A general formula of the equation of RMS emittance change for an electron linac, taking both external and beam fields into account, has been induced, and analytic estimations of emittance changes have been discussed in the presence of only the external field or the space charge field, or the wake field respectively.
A general formula of the equation of RMS emittance change for an electron linac, taking both external and beam fields into account, has been induced, and analytic estimations of emittance changes have been discussed in the presence of only the external field or the space charge field, or the wake field respectively.
1992,
04: 107-113.
Abstract:
We have made some experiments to study the emission performance of velvet cathodes with long (120ns, 50ns) and short (3ns) pulses. The cathode current densities are 400 kA/cm2 and 7kA/cm2 respectively.
The voltage-current plot, cathode emission pattern, scanned electron microphotograph and the practical construction of velvet cathodes are presented.
Some ideas about emission mechanism of velvet cathodes have been suggested.
We have made some experiments to study the emission performance of velvet cathodes with long (120ns, 50ns) and short (3ns) pulses. The cathode current densities are 400 kA/cm2 and 7kA/cm2 respectively.
The voltage-current plot, cathode emission pattern, scanned electron microphotograph and the practical construction of velvet cathodes are presented.
Some ideas about emission mechanism of velvet cathodes have been suggested.
1992,
04: 114-118.
Abstract:
Four current monitors have been developed at CIAE. They are used to measure relativistic electron beams in a large area diode. Two Rogowski coils with a rectangular frame can be used to monitor electron beam currents without interrupting them. A shunt is made of stainless steel foil with a thickness of 15μm. It is set between two sections of outer cylinder of the Blumlein line. The shunt has a much longer lifetime than that made of carbon or metal film resistors.
Four current monitors have been developed at CIAE. They are used to measure relativistic electron beams in a large area diode. Two Rogowski coils with a rectangular frame can be used to monitor electron beam currents without interrupting them. A shunt is made of stainless steel foil with a thickness of 15μm. It is set between two sections of outer cylinder of the Blumlein line. The shunt has a much longer lifetime than that made of carbon or metal film resistors.
1992,
04: 119-126.
Abstract:
Effects of electron beam parameters, including radius, emittance and energy, on bremsstrahlung exposure angular-distributions at a distance of one meter in front of the target, are discussed in this paper. The fit formula for beam radius and emittance is obtained in order to get the maximum forward exposure. The higher the beam energy and the less the emittance, the better the distribution of exposure. The positions and angle spreads of all beamlets are calculated with both analytic and Monte-Carlo methods. The results are in agreement with each other.
Effects of electron beam parameters, including radius, emittance and energy, on bremsstrahlung exposure angular-distributions at a distance of one meter in front of the target, are discussed in this paper. The fit formula for beam radius and emittance is obtained in order to get the maximum forward exposure. The higher the beam energy and the less the emittance, the better the distribution of exposure. The positions and angle spreads of all beamlets are calculated with both analytic and Monte-Carlo methods. The results are in agreement with each other.
1992,
04: 127-130.
Abstract:
A fluid model is used to investigate microwaves excited by two REBs in a cylindrical waveguide. The dispersion relation is derived in the presence of an infinite axial magnetic field. The growth rate is given at the Cerenkov resonant point, and the results are discussed.
A fluid model is used to investigate microwaves excited by two REBs in a cylindrical waveguide. The dispersion relation is derived in the presence of an infinite axial magnetic field. The growth rate is given at the Cerenkov resonant point, and the results are discussed.
1992,
04: 131-136.
Abstract:
The frequency characteristics and growth rates of electrostatic waves in plasma wakefield accelerators are obtained in the condition of linear approximation and the physical explanation of the wakefield machanism is given in this paper.
The frequency characteristics and growth rates of electrostatic waves in plasma wakefield accelerators are obtained in the condition of linear approximation and the physical explanation of the wakefield machanism is given in this paper.
1992,
04: 137-140.
Abstract:
The method of lithium ion emitter preparation with β-eucryptite is presented.The emission performance of a β-eucryptite emitter is measured.
The method of lithium ion emitter preparation with β-eucryptite is presented.The emission performance of a β-eucryptite emitter is measured.
1992,
04: 141-147.
Abstract:
Thermomechanical response of Al plates under tension to high energy CW CO2 laser radiation is discussed. The combined loading experiment device, method, and results are presented.
Thermomechanical response of Al plates under tension to high energy CW CO2 laser radiation is discussed. The combined loading experiment device, method, and results are presented.
1992,
04: 148-152.
Abstract:
This paper discusses a new concept appeared recently: the diffraction-free beam, whose physical principles and future applications are also discussed.
This paper discusses a new concept appeared recently: the diffraction-free beam, whose physical principles and future applications are also discussed.
1992,
04: 153-156.
Abstract:
This paper makes a numerical evaluation for the approximative path equation of electron motions in a diode. The numerical evaluation results are used for designing a relativistic diode electron gun.
This paper makes a numerical evaluation for the approximative path equation of electron motions in a diode. The numerical evaluation results are used for designing a relativistic diode electron gun.
