S. A. Korff

Effect of Gaseous Impurities on BF3 Proportional Counters

The effect which SiF4, SO2, and SF6 have on the plateau and the pulse size distribution of a proportional counter were investigated. SiF4 was tested at three pressures, 30, 45, and 60 cm, of BF3 and its effect was found to be independent of the counter pressure for the range of value considered. From the variation in the plateau, the attachment probability for SiF4 was calculated to be h = 1.485×10−5 and its cross section for attachment to be σa = 5.12×10−20 cm2. The amount of these gases permitted, without the counter being affected beyond the limits of tolerance which are set up, were found to be 0.04% for SiF4, 0.01% for SO2, and 2.0×10−6% for SF6.

Deterioration of Boron Trifluoride Counters Due to High Counting Rates

Twenty‐two boron trifluoride counters were run at counting rates of about 106 counts per min in the proportional region until they had all lost their plateaus of voltage versus counting rate. This occurred in from 108 to 109 counts. The pulse heights decreased to the point at which maximum sensitivity of the circuitry failed to record more than 103 counts per min, although many more small pulses could be detected on an oscilloscope. Raising the voltage did not restore the pulse heights. The counters did not recover after inactive periods of up to four months. Gas samples from several of the counters were analyzed on a mass spectrometer. A theory is proposed which would explain the deterioration on the basis of a negative ion sheath which is formed when the BF3 dissociates.

Fast-Neutron Detector with Discrimination against Background Radiation

A detector that measures neutrons between 1 and 10 MeV in a mixed background of charged and neutral radiation was developed for use in cosmic‐ray studies. The detector consists of liquid scintillator NE213 surrounded by a thin shield of plastic phosphor NE102 for charged particle rejection. Both scintillators are viewed by a single photomultiplier, in an adaptation of the pulse‐shape discrimination technique.

The radiosonde: The stratosphere laboratory

Abstract The radiosonde, the most recently developed tool for use in the investigation of phenomena in the upper atmosphere, is described. The various merits and disadvantages of the three systems now in use for the transmission of physical data from the stratosphere are reviewed.In a discussion of present-day radiosonde technique are included descriptions of transmitters, receivers, meteorological and other observing instruments, and ballooning methods. Their application to the study of cosmic rays is given as a typical illustration of their usefulness in fields other than meteorological. A new formula for the upward velocity of a flight in terms of its free lift is developed, which shows that the observed constant rate of ascent of pilot type balloons is fortuitous, depending on a particular range of values of the Reynolds Number of the balloons.

High Altitude Observatories for Cosmic Rays and Other Purposes

The original proof that cosmic radiation was of extra-terrestrial origin came from balloon flights made by Hess and others, in the early years of this century. Since the cosmic radiation was attenuated by the atmosphere, it was clear that to study this radiation one should go up as high as feasible. From the first, balloon flights were used, but these can carry only limited loads and have hard-to-control trajectories and flight characteristics. We discuss these below. Aircraft could not attain high altitudes in the early years and only since about 1940 have been much used for high altitude studies. For example, a flight made by the present author in 1936, in the original DC-2, broke the then South American altitude record, reaching over 30000 feet, and this record stood for a number of years.

Plateau Slopes and Pulse Characteristics of Large, High‐Pressure BF3 Counters

Factors affecting the flatness of plateaus of BF3 neutron counters of large radius and at high pressure were investigated. Counters prepared using special purification techniques showed improved characteristics. Counters of cathode radius from 1.91 to 5.06 cm were filled to pressures of BF3 from 40 to 64 cm Hg, and their pulse‐height distributions were compared. Results are discussed in terms of electron attachment in BF3 and space charge effects.

An Improved Radiobarograph

A radiobarograph is described, which is accurate to 1 mm Hg pressure. This instrument employs a suspension giving increased sensitivity at low pressures, and rendering it free from backlash. Various tests on this barograph are described.

Canadian high‐altitude station at Sulphur Mountain

A recent and a most welcome addition to the roster of high‐altitude research facilities is the new Canadian station on Sulphur Mountain near Banff, Alberta, in the Canadian Rockies. This station is of particular importance because, in addition to being well supplied and equipped, it is also the only high‐altitude research facility in this area, and therefore is of so much importance in completing the world network of stations. The importance of the location was underscored at the 1954 Rome meeting of the Special Committee for the International Geophysical Year (CSAGI), by the Geographical Coordination Committee of which the present author was fortunate to be a member. This Committee considered what should be the optimum distribution of stations all over the world in order best to intercept cosmic‐ray impact zones and favorably to locate many other important IGY research activities such as auroral studies and ionospheric physics. The establishment of a station in the Rockies was recommended at that meeting.

THE EFFECTS OF COSMIC RAYS ON THE TERRESTIAL ISOTOPE DISTRIBUTION

The effects of the cosndic rays on the isotope distribution in the surface, atmosphere, and oceans of the earth are considered quantitatively. It is shown that cosmic rays build up both stable and radioactive isotopes, and the amounts to be expected are discussed. The amounts accumulated during the lifetime of the earth are calculated. The deuterium of the oceans, the tritium, and the helium-3 situation are considered. Dating with stable isotopes is discussed. The formation of spallation products in the atmosphere is considered briefly. (D.L.C.)

The world's high altitude laboratories

A recent survey article on high altitude laboratories has elicited so much correspondence that it was thought worth‐while to present todays roster of such stations in tabular form. In the table below and on the map on p 30 several stations now in operation are listed in order of ascending geomagnetic latitude. In addition four stations at present under study are mentioned, one or more of which may be in operation in the near future. Omitted from this list are such well‐known observatories as Mt. Wilson, Mt. Palomar and others, since their elevation is not particularly high. Also omitted are such cities which may happen to lie at high elevations, as for example La Paz, Bolivia, at which no formally organized high altitude laboratories are known to this writer. Finally, we do not list any observatories in countries behind the Iron Curtain, but only those which will welcome scientists of all nations. The majority of the stations have electric power available usually via transmission lines from generating st...