The development of magnetic ion-source with high ionisation efficiency

Starting from the principle given by A. Th. F i n k e l s t e i n l) , M. yon Ardenne2) 3) and W. Maas4), further development of the magnetic ion-source has been undertaken. The instrument has been designed especially for use with a 800 kV neutron generator described by W. M a a s 4) and under normal operating conditions the source will have an output of 1 mA ion current. After increasing input power several milliamperes may be obtained. The principal advantages of the magnetic source turn out to be: 1. the power consumption is low, power is obtained from storage batteries. Consequently the source and its complete power supply can be put at a high potential with respect to the earth; 2. no artificial cooling is required; 3. gas-pressure and hence gas-consumption are low; 4. a homogeneous ion beam -- with respect to ion velocity -- is obtained

The crystal counter : A new apparatus in nuclear physics for the investigation of β- and γ-rays. Part II

AgCl crystals were irradiated with monochromatic β-rays in a magnetic β-ray spectrograph. The results show that under suitable experimental conditions in the crystal all β-rays of a certain energy cause ionisation pulses of the same value within the errors of measurement. The magnitude of an ionisation pulse is proportional to the energy of the β-particle. This means that the amount of energy necessary for the formation of one conduction electron is independent of the energy of the β-rays. This amount was found to be 7,6 eV. The measurements of the ionization pulses caused in AgCl by α-rays showed that many of the α-particles caused an ionization pulse smaller than normal. We ascribed this effect to a thin irregular surface layer which is less effective than the crystal's interior. Many of the crystals we investigated showed a thicker surface layer. This layer also influenced the ionization by β-particles, which then showed the same effect as the α-rays. The nature and the circumstances under which this hypothetical surface layer appears or can be removed are not yet clear and still form a point of investigation

Mirror quiescence and high-sensitivity position measurements with feedback

We present a detailed study of how phase-sensitive feedback schemes can be used to improve the performance of optomechanical devices. Considering the case of a cavity mode coupled to an oscillating mirror by the radiation pressure, we show how feedback can be used to reduce the position noise spectrum of the mirror, cool it to its quantum ground state, or achieve position squeezing. Then, we show that even though feedback is not able to improve the sensitivity of stationary position spectral measurements, it is possible to design a nonstationary strategy able to increase this sensitivity.Comment: 25 pages, 11 figure

Optomechanical scheme for the detection of weak impulsive forces

We show that a cooling scheme and an appropriate quantum nonstationary strategy can be used to improve the signal to noise ratio for the optomechanical detection of weak impulsive forces.Comment: 4 pages, Revtex, 1 figur

The influence of microseismic perturbations on a cold damped electrometer

It is proved that the excess fluctuation of an electrometer above the electrical and mechanical Brownian movements found in a former investigation was due to microseismic movements of the soil. A theory is developed of the influence of mechanical perturbations on a cold damped 1) electrometer. This theory predicts a characteristic connection between the course of the excess fluctuation with the damping and the Fourier spectrum of the microseismic movement; this connection was checked experimentally. A further proof is the fact, that the Fourier spectrum of the microseismic movement deduced from the spectrum of a recording of the fluctuation of our electrometer is in agreement with a Fourier analysis of a seismogram

An infrared isotope analyzer

The shift in the infrared absorption bands of isotopic molecules is used in a new method for determining the isotope ratios in tracer experiments. The infrared absorption is measured with a non-dispersive filter instrument containing as selective detector a gas cell filled with a concentrated sample of the component to be measured. An instrument is devised according to this method, to measure the 13C/12C ratio in carbon dioxide. It permits the measurement of the 13C abundance in 30 mg carbon dioxide with an error of 0.005 at.% in the neighbourhood of the natural abundance of 1.1 at.%. This precision is sufficient for the majority of tracer experiments. A more detailed account of this study is to be found in the thesis 5) of one of us

The quantitative determination of the spectral distribution of phototactic sensitivity in the purple bacterium Rhodospirillum rubrum

By using a compensation method, the action spectrum (spectral distribution of stimulating efficiency in a quantitative measure) of phototaxis in the purple bacterium Rhodospirillum rubrum (Esmarch) Molisch Strain 4 was determined. Two differently coloured adjacent small light fields were projected in a slide chamber containing a (dilute) suspension of moving spirilla. One of the fields acted as a standard, whereas in the other one the intensity as well as the wave-length of the light could be varied. The principle of the determination of the spectral sensitivity in the spirilla was based upon the adjustment to equivalence of the two fields for different wave-lengths. Shock reactions of the spirilla at the boundary between the fields were used as an “indicator” as to how far the fields were adjusted. A mathematical derivation was given. It showed that the action spectrum of phototaxis is identical with the absorption spectrum of the light acceptor active in the phototactical reaction. The action spectrum shows maxima at about 8800, 6900, 5900, 5250, 4900, 4600, and at about 4000 A