Die Entwicklung neuer Turbomolekularpumpen mit erhöhter Vorvakuumbeständigkeit ermöglicht bei Auslaßdrücken von bis zu 30 mbar den Einsatz von bis zu 30 mbar den Einsatz von ölfreien Membranpumpen als Vorvakuumpumpen. Die Kombination von Weitbereich‐Turbomolekularpumpe und Membranpumpe stellt ein preiswertes, kompaktes und technisch trockenes HV‐ und UHV‐Pumpensystem dar. Das Zusammenwirken von Weitbereich‐Turbomolekularpumpen mit verschiedenen Membranpumpen wird im Hinblick auf Gasdurchsatz, Kompressionsverhältnis, Enddruck und Leistungsaufnahme diskutiert und Auswahlkriterien für die Vorpumpe werden aufgezeigt.

The modern diaphragm vacuum pump is established for the generation of rough and fine vacuum due to very good Vacuum technological data such as high pumping speed, high compression ratio, long lifetime of diaphragms and valves, ease of maintenance, totally oilfreeness and its environmental friendliness (especially of the chemistry version). The wider use of diaphragm pumps made it necessary to introduce a new standard for the measurement of the pumping speed of this type of oscillating pump for achieving high accuracy and reproducibility (DIN 28432, Acceptance specifications for diaphragm pumps, Beuth Verlag, Berlin, Germany). With this method pumping speed curves for Helium, Nitrogen and Argon and ultimate pressures for one to four stage diaghragm pumps have been measured and analysed on the basis of turbulent and laminar flow and thermal effects. Copyright (C) 1996 Elsevier Science Ltd.

According to all testing procedures which have been standardized so far, the pumping speed of vacuum pumps is measured by injecting a stationary flow of gas into a test dome and measuring the equilibrium pressure. This stationary method is difficult to automatize due to the problem of automatizing the generation of gas flows over the required range of several decades. Alternatively, the pumping speed of rough vacuum pumps can be measured by evacuating a large vessel and monitoring the pump-down curve. However, one disturbance has to be considered: in the evacuation process, the temperature drops due to the gas expansion and then slowly rises towards ambient temperature due to heat transfer from the surroundings. Since changes of temperature cause changes of pressure, the derived pumping speed is affected. This disturbance can be overcome by interrupting the pumping process by means of an electrically controlled valve and subsequent waiting for thermal equilibrium. The setup required for the intermittent pump-down method is rather simple and the testing procedure can easily be automatized. In the present work, the various physical and technical aspects of pumping speed measurements by both meth ods are carefully examined. Theoretical considerations show that both methods in fact yield the correct pumping speed if properly applied to rough vacuum pumps. This result is confirmed by comparative measurements. Copyright (C) 1996 Elsevier Science Ltd.

Both rotary vane and roots type pumps have proven excellent as vacuum pumps for many decades. However, the performance of oil sealed rotary vane pumps is limited when condensable or corrosive vapours are pumped or when contamination by backstreaming oil is critical. ‘Oil free’ roots pumps require a rather complicated set-up for compression to atmospheric pressure. Diaphragm pumps are totally oil free and can be made of materials highly resistant against chemical attack. Their performance is limited mainly by comparatively small pumping speeds and restricted ultimate vacuum. By connecting diaphragm pumps in series with rotary vane and/or roots pumps all the main properties of these types of pumps are combined, i.e. chemical resistance and low ultimate vacuum, high pumping speed and immensely reduced hydrocarbon background.

AbstractThe term pumping speed of a vacuum pump denotes the volume flow rate of gas removed by the pump. In a measurement of the pumping speed it has to be taken into account that the volume of a quantity of gas depends on pressure and temperature. The present article presents a critical investigation of two different procedures for measuring the pumping speed in the rough vacuum regime: In the first procedure, gas flows continuously through the test dome and the pump under investigation. The pumping speed is obtained from the stationary values of throughput and pressure in the test dome. This procedure is well established, technical details are described in various standards. In the second procedure, a large vessel with known volume is evacuated by the pump, and the pumping speed is derived from the pressure decrease with time. In order to avoid disturbances by thermal effects, the vessel may be pumped only during short time intervals with intermediate waiting for thermal equilibrium. The second procedure offers instrumental advantages and its practices are described in a new DIN standard. The physical basis and technical aspects of both procedures including disturbing thermal and other effects are investigated. If applied correctly at inlet pressures in the rough vacuum range, both procedures are expected to yield the same values of the pumping speed. Comparative measurements at a diaphragm pump confirm this expected behaviour within the experimental uncertainty of about 3% (2σ).

High-resolution inelastic-scattering measurements on 112Cd with polarized deuterons (20 MeV) and polarized protons (16 and 65 MeV) provide complete spectroscopic information. Transition moments are obtained from the angular distributions of the cross section and analyzing power in a coupled-channel reaction analysis. The results are compared with interacting boson model predictions aiming to describe intruder states, quadrupole-hexadecapole and quadrupole-octupole excitations.

High resolution inelastic scattering measurements with 20 MeV polarized deuterons and results of recent Coulomb excitation studies of Hasselgren et al. on 110Pd are compared with predictions from new IBA calculations, where configuration mixing or Q̂Q̂ interaction between like bosons was included to describe intruder states and triaxial features, respectively. The spectroscopic properties of the four low-energy collective bands are well described.

The reaction 113 Cd ( d , t ) 112 Cd has been studied using a 20 MeV polarized deuteron beam with an energy resolution of 5–9 keV. Angular distributions and analyzing powers for states up to ∼3.4 MeV are analyzed using DWBA calculations. Spin assignments, spectroscopic factors and strength distributions are deduced. F -spin collectivity of four 2 + states is discussed. Strength distributions for different j -transfers are compared with RPA calculations.

The excitation spectrum of 41Ca up to the emission threshold has been investigated in a magnetic spectrograph study of the 41Ca(d,p) reaction at Ed = 20 MeV with polarized deuterons. From DWBA and CCBA data analyses, experimental strength distributions are obtained for single-particle configurations in 41Ca. These results are compared to quasiparticle RPA calculations. The radial dependence of the form factors is studied with respect to the excitation energy behaviour with major shell mixing. We find that in general the observed occupation respectively depopulation of the orbitals can be well accounted for by the theoretical model.

Totally oil-free diaphragm pumps with optimized cylinder geometry and minimum dead volume are able to provide an ultimate pressure of 2 mbar and high volume flow rate. These extraordinary attributes rise to a large field of applications. The use of the diaphragm pumps as fore-pumps for systems with cryo-, turbomolecular and iongetter pumps opens the door to oil-free high and ultra-high vacuum systems. Possible applications in nuclear physics are for example evacuation of target chambers at accelerators to avoid carbon contamination on thin targets by backstreaming oil from forepumps or oxidation of target material with the extremely rare and expensive oxygen-17 isotope.

The use of chemically resistant oil-free diaphragm pumps to pump condensable vapours allows the recovery of these vapours on the high pressure side. Due to their limited ultimate pressure they mainly replace water jet pumps and thus drastically reduce water consumption and pollution. In addition they raise the efficiency of evaporators and, as a consequence, diminish the pollution of air. The combination of this type of diaphragm pump with an oil-sealed rotary vane pump (“HYBRID” pump) combines the advantages of both pumps, i.e. low ultimate pressure and high resistivity to chemicals. Thermodynamic considerations lead to this set-up, in which the dry pump evacuates the oil reservoir of the rotary vane pump and thus the oil is permanently distilled. Due to the elevated temperatures of the oil (50–70°C) and the reduced pressure (≈ 50 mbar) condensation is avoided or significantly reduced, thus enhancing oil lifetime and maintenance intervals.

The use of chemically resistant oil-free diaphragm pumps to pump condensable vapours allows the recovery of these vapours on the high pressure side. Due to their limited ultimate pressure they mainly replace water jet pumps and thus drastically reduce water consumption and pollution. In addition they raise the efficiency of evaporators and, as a consequence, diminish the pollution of air. The combination of this type of diaphragm pump with an oil-sealed rotary van pump ("HYBRID" pump) combines the advantages of both pumps i.e. low ultimate pressure and high resistivity to chemicals. Thermodynamic considerations lead to this set-up, in which the dry pump evacuates the oil reservoir of the rotary vane pump and thus the oil is permanently distilled. Due to the elevated temperature of the oil (50-70-degrees-C) and the reduced pressure (almost-equal-to 50 mbar) condensation is avoided or significantly reduced, thus enhancing oil lifetime and maintenance intervals.

The reaction 113Cd(d, t)112Cd has been studied using a 20 MeV polarized deuteron beam with an energy resolution of 5–9 keV. Angular distributions and analyzing powers for states up to ∼3.4 MeV are analyzed using DWBA calculations. Spin assignments, spectroscopic factors and strength distributions are deduced. F-spin collectivity of four 2+ states is discussed. Strength distributions for different j-transfers are compared with RPA calculations.

The -γ-ray spectrum emitted after thermal neutron capture in 31P was studied at the ILL high flux reactor with a pair spectrometer and an intrinsic Ge detector. A total of 212 transitions were assigned to the decay of 32P and 155 of these, representing 96.7% of the observed flux, were placed in a level scheme of 38 states. The neutron binding energy was determined as 7935.74 (16) keV. The densities of states observed in this reaction and in a recent (d, p) study are analyzed in the constant temperature Fermi-gas model. The primary E1 and M1 transition strengths in 32P are discussed and are compared to other sd-shell nuclei.

Neutron strength distributions of $^{41}\mathrm{Ca}$ have been obtained from a high resolution study of the $^{40}\mathrm{Ca}$(d\ensuremath{\rightarrow},p) reaction. They agree well with quasiparticle-phonon coupling calculations in a large configuration space including major shell mixing. We see no evidence of strong depopulation of closed shell orbitals.

Neutron pick-up measurements have identified the s12 and d32 holes states in 147Gd, 145Sm, and 143Nd. The results also locate the 12+ and 32+ members of the vf72×3− septuplet via their admixtures from these hole states. Additional energy perturbations of the septuplet result largely from a negative quadrupole moment of the octupole phonon, with a Z-dependence consistent with the microscopic structure of the 3− excitation in the N=82 nuclei.

The reaction 36S(d, p) has been studied at Ed = 20 MeV with enriched 36S using H2S gas targets and the Q3D magnetic spectrograph. We identify 35 excited states in 37S. Angular distributions for dσdΩ(θ) and Ay(θ) yield quantum numbers Jθ and spectroscopic factors for most of them. Comparison is made to the distribution of strength in 41Ca. From an additional (d,d′) experiment at Ed = 23 MeV we derive multipole moments for the 2+1 and 3−1, state in 36S.

Precise measurements of cross sections and complete sets of analyzing powers for the (d, α) reaction from 40Ca to the ground state 31+ and excited states 11+, 12+, 22+ of 38K at Ed = 20 MeV have been analyzed in a finite-range distorted-wave Born approximation, using full sd-shell-model wave functions and including a D-state amplitude for the deuteron clusters in the α-particle. Deuteron tensor potentials were included and the influence of two-step processes estimated. The results are compatible with the previous determination of D2 (4He) = − 0.19 ± 0.04 fm2 from the ground-state transition, which is found to be the most appropriate one for the determination of D-state effects.