Magnetic Pump Research Articles

The parametric excitation of kinetic Alfvén waves by a magnetic pump

The parametric decay of a magneto-acoustic pump wave into low-frequency waves modified by finite temperature effects is considered. The excited waves are the kinetic Alfvén wave and the ion-acoustic wave. The former wave plays an important role in linear heating schemes employing the mode conversion of magneto-acoustic waves at the Alfvén resonance. Here we calculate the parametric growth rates and pump thresholds for excitation of these waves. The main result is that finite temperature effects tend to reduce the growth rate of Alfvén waves.

The diffusive wiggler—a spatially periodic magnetic pump for free-electron lasers

Magnetic diffusion through a spatially periodic assembly of metal conductors yields a large-amplitude, quasi-static pump for use in free-electron lasers. The experimental observations are compared with predictions of a 2-D triangular mesh, finite-difference magnetic-diffusion code (TRIDIF).

A generalized formulation of free-electron lasers in the low-gain regime including transverse velocity spread and wiggler incoherence

It is shown that in the small-signal, low-gain regime, an analytic expression for the gain can be derived which is valid for a general electron distribution function and general longitudinal variation of the transverse magnetic field pump. This expression is used to evaluate the effects on the gain curve due to transverse momentum spread in the beam as well as inaccuracies (incoherence) in the magnetic pump phase and amplitude. The restricting criteria for the neglect of these effects are derived.

Theory of free-electron lasers

A general analysis is presented of free-electron lasers in which a static periodic magnetic pump field is scattered from a relativistic electron beam. The steady-state formulation of the problem is fully relativistic and contains beam thermal effects. Growth rates associated with the radiation field, efficiencies, and saturated-field amplitudes are derived for various modes of operation. Effects of space charge on the scattering process are included and shown to play a dominant role in certain situations. Scaling laws for the growth rates and efficiencies at a fixed radiation frequency as a function of the magnetic-pump amplitude are obtained. The shear in beam axial velocity due to self-fields is discussed, and various methods of reducing it are suggested. Finally, a detailed illustration of a far-infrared ($\ensuremath{\lambda}=2$ \ensuremath{\mu}m) two-stage free-electron laser using a 3-MeV electron beam and a 2-cm-wavelength magnetic pump field is presented.

Sampling Culturable Heterotrophs from Microcosms: a Statistical Analysis

The contributions of different sources of error in sampling mixed and unmixed bacterial microcosms were evaluated by using analysis of variance. Culturable heterotrophic bacteria from a turbid freshwater impoundment were sampled from 9-liter tanks that were unagitated or mixed with magnetic stirrers or pumps and from dilution bottles that were unagitated or agitated with a mechanical shaker. Axenic cultures of Enterobacter aerogenes were also sampled from manually shaken test tubes. In both agitated and unagitated tanks and in unagitated dilution bottles, dilutions made from the same sampling pipette were significantly different, showing a clumping of bacteria on the scale of millimeters. Also, microcosms within a single experiment differed from one another by a large margin. Dilution mean squares and tank or bottle mean squares were homogeneous for all types of tanks and unagitated bottles, indicating that the gentle mixing provided by pumps and stir bars did not reduce either millimeter scale or intermicrocosm variability over what prevailed in unagitated microcosms. By contrast, the vigorously shaken bottles and test tubes showed no millimeter scale variability. Intermicrocosm variability was undetectable in test tubes and two orders of magnitude less in shaken bottles than in unshaken bottles. When these facts are coupled with the inherent statistical advantage of replicating large rather than small experimental units, it is concluded that sampling error in the enumeration of aquatic bacteria in microcosms will be reduced by using numerous, small, violently agitated microcosms with a minimum of subsampling per microcosm.

Analysis of the reliability of magnetic electrical-discharge pumps

Analysis of the reliability of magnetic electrical-discharge pumps

A compact photochemical spectrometer cell

A compact silica cell and photochemical assembly have been constructed which permit the simultaneous measurement of absorption spectra and exposure to ultraviolet light. The attractive features of the cell include relatively small liquid volume (14 cm3), continuous stirring by magnetic stirring-bar pump, and thermostated water jacket. The compact design provides durability and convenience of use which is particularly well-suited to use in a glove box.

1267. A magnetic electrical-discharge pump: B G Bekker and S V Solov'ev,Soviet Patent, class H 01 j, 41/00, No. 371633, claimed 15 April 1968, publd 22 February 1973 ( in Russian)

1267. A magnetic electrical-discharge pump: B G Bekker and S V Solov'ev,Soviet Patent, class H 01 j, 41/00, No. 371633, claimed 15 April 1968, publd 22 February 1973 ( in Russian)

The cleaning of magnetic ion pumps by chemical etching

A chemical etching method is described to improve the speed and ultimate vacuum of sputter ion pumps. The entire pump is immersed in strong acid solution in order to avoid the difficult and unnecessary task of disassembly recommended by the manufacturers.

Behaviour of a flux pump using an automatic superconducting switch

A simple kind of magnetic flux pump, consisting of a small superconducting coil L 1 in parallel with a superconducting magnet L 2, has been constructed and tested. The device is attached to the secondary of a transformer and the entire assembly rests in a liquid helium bath. Persistent currents in L 2 are generated by a power supply which can be made particularly simple if an axial magnetic field H b is applied to L 1 to make its critical current sense-dependent. Circuits analysis shows that the rate of flux pumping is dependent on the magnitude of the power supply output and the final persistent current level is related to H b . These results are confirmed by experiments in which several circuit parameters were varied. A typical experiment generated 35 A in a small magnet in about 10 minutes. Suggestions are made for improvements on this behaviour.

996. Magnetic discharge pump: A I Shakun and V I Makhanov,USSR Patent No 305523, and 2 nd Sept 1968, publd 27 th July 1971

996. Magnetic discharge pump: A I Shakun and V I Makhanov,USSR Patent No 305523, and 2 nd Sept 1968, publd 27 th July 1971

524. Problem of argon instability of a diode magnetic discharge pump with a plane porous cathode: A I Skakun and V I Makhanov, Electronic Technology, Scient-Techn Collect, Technol and Organiz Product, No 3, 1971, 81–92 ( in Russian)

524. Problem of argon instability of a diode magnetic discharge pump with a plane porous cathode: A I Skakun and V I Makhanov, Electronic Technology, Scient-Techn Collect, Technol and Organiz Product, No 3, 1971, 81–92 ( in Russian)

678. Investigation of gas composition in the pumping system—device pumped by oil diffusion pump with a chracoal adsorption trao or magnetic electrical-discharge pump

678. Investigation of gas composition in the pumping system—device pumped by oil diffusion pump with a chracoal adsorption trao or magnetic electrical-discharge pump

268. An inbuilt magnetic discharge pump for powerful transmitting valves: A I Skakun and V I Makhanov, Electronic Technology, Scientific-Technical Collection of Articles on UHF Electronics, 1970, No 6, 136–144 ( in Russian)

268. An inbuilt magnetic discharge pump for powerful transmitting valves: A I Skakun and V I Makhanov, Electronic Technology, Scientific-Technical Collection of Articles on UHF Electronics, 1970, No 6, 136–144 ( in Russian)

Selection of a Vac-Ion Pump for a Terminal Ion Source

An 800 l/s electrostatic ion pump and a 500 l/s magnetic triode ion pump have been tested to determine which would be most suitable for pumping the hydrogen gas emanating from a duoplasmatron ion source. The ion source and pump will be located in the terminal of a High Voltage Engineering Corporation (HVEC) type MP tandem accelerator. The two pumps were mounted on a pump test stand with a manometer, two needle valves, and two ion gauge controllers. The hydrogen flow to each pump was increased slowly until the pump was near the point of pressure instability. Flow rates and pressure were recorded for approximately 1000 hours. The performance of the magnetic triode ion pump was superior to that of the electrostatic pump. The magnetic triode ion pump has undergone another test pumping the hydrogen gas from a duoplasmatron. Pumping speed measurements, modes of failure, and other details of these continuing tests will be presented.

The discharge mechanism in a magnetic ion pump: II The influence of electric field and gas concentration on the development of discharges

The discharge mechanism occurring under UHV conditions is examined with special reference to T 31 , the time required for the discharge to develop to an extent such that measurable pumping action is observed. This paper supplements a previous paper in three aspects. First, the rate of growth of the electron cloud is calculated using the more appropriate exponential growth theory rather than the previously used chain reaction theory. Second, the range of experimental measurements have been extended to show that the previously deduced relation of pressure and starting time, PT s =constant, is valid for the range of 10 −8 to 10 −11 torr. Third, the experimentally observed dependence of starting time on the applied electric field is shown to be consistent with field emission as the primary mechanism for provision of the initial electron for the avalanche.

The discharge mechanism in a magnetic ion pump: R D Craig, Associated Electrical Industries Ltd, Manchester, England

The discharge mechanism in a magnetic ion pump: R D Craig, Associated Electrical Industries Ltd, Manchester, England

Magnetoelastic Parametric Interaction due to the ΔE Effect

A calculation is presented for the instability of elastic waves parametrically pumped by a time-varying elastic modulus in long, thin nickel rods or tubes at kilocycle frequencies. The modulus is varied by varying the biasing magnetic field according to the ΔE effect. The instability has been observed in nickel tubes (but not in rods) by driving the parametric magnetic pump at twice the fundamental mechanical resonant frequency of the tube, and observing that the vibrations corresponding to fundamental resonance of the tube set in at a very definite value of the pump amplitude, i.e., the threshold value. The form of the curves of threshold amplitude vs dc bias field in annealed tubes is in agreement with theory, using the previously measured modulus vs field curves. The observed threshold amplitudes are in satisfactory agreement with the theoretical estimate. The form of the above curves and threshold amplitudes are quite different in tubes which presumably still retain some of the effects of cold work experienced in fabrication.

Magnetic gas circulation pump for pressure reactors

Magnetic gas circulation pump for pressure reactors

1245. A high-vacuum unit with a magnetic discharge pump: E M Rudnitskii and G S Selyakh,Instrum Exp Tech, Dec 1965, 645 (Transl from Pribory i Tekh Eksp, No 3, May/June, 1965)

1245. A high-vacuum unit with a magnetic discharge pump: E M Rudnitskii and G S Selyakh,Instrum Exp Tech, Dec 1965, 645 (Transl from Pribory i Tekh Eksp, No 3, May/June, 1965)