THE RANGE OF THE ALPHA-PARTICLES FROM URANIUM II

1931 ◽  
Vol 5 (5) ◽  
pp. 567-571 ◽  
Author(s):  
S. Bateson
Keyword(s):  
Direct Measurement ◽  
Alpha Particles ◽  
A Value ◽  
Scintillation Method ◽  
Good Agreement ◽  
Α Particles

The range of the α-particles from uranium II has been determined by a scintillation method to be 3.29 ± 0.08 cm. at 15 °C. and 760 mm. This is in good agreement with Laurence's value found with a Wilson chamber. From the Geiger-Nuttall relationship the period is calculated to be 28,000 years, a value considerably less than that found recently by direct measurement.

scholarly journals The scattering of alpha particles at small angles by helium

1932 ◽  
Vol 137 (833) ◽  
pp. 677-688 ◽  
Keyword(s):  
Classical Theory ◽  
Alpha Particles ◽  
Helium Nucleus ◽  
Wave Mechanics ◽  
Low Velocity ◽  
Expansion Chamber ◽  
Vector Quantity ◽  
Mechanical Scattering ◽  
Good Agreement ◽  
Α Particles

It has been shown by Mott on the basis of the wave mechanics, that in the case of collisions between identical particles the scattered particles should interfere with the projected particles travelling in the same direction. When α -particles are scattered in helium, if the scattered α -particles and projected helium nuclei of similar velocity are identical in all respects, there will be interference between the two streams of particles. For collisions in which the particles act upon each other with forces varying as the inverse square of the distance between them, the interference results in the scattering intensity varying above and below the classical value and rising to double the classical numbers at 45º. At small angles the scattering predicted by the quantum mechanics does not differ greatly from that given by the classical theory. An experiment carried out by Chadwick showed quite definitely that for sufficiently slow α -particles the amount of scattering at 45º was double that of the classical theory. For these α-particles of low velocity the results showed that the forces varied very little from Coulomb forces; hence it was evident that the discrepancy was due to the failure of the classical theory. The scattering of slow α -particles by helium has also been investigated by Blackett and Champion by means of an expansion chamber. The observed scattering was in good agreement with the wave mechanical scattering. These experiments verify the assumption upon which Mott s theory is based, namely, that it is impossible to distinguish between an α-particle and a nucleus of helium travelling at the same velocity. Thus the helium nucleus has no spin or vector quantity associated with it; its field of force is perfectly spherical.

scholarly journals The rate of emission of alpha particles from radium

1929 ◽  
Vol 125 (799) ◽  
pp. 713-730 ◽  
Keyword(s):  
Solid Angle ◽  
Alpha Particles ◽  
Compensation Method ◽  
Total Charge ◽  
A Value ◽  
Accurate Knowledge ◽  
The Subject ◽  
Α Particles ◽  
Number Of Particles

The number of disintegrations taking place per second in a gram of radium is a consatant of great importance in quantitative radioactive work, and an accurate knowledge of its value is accordingly essential. This constant, which is usually denoted by Z, has been the subject of numerous researches, but the results, even of comparatively recent measurements, have been disappointingly inconsistent. A discussion of the methods employed and the results obtained has been recently given in a paper by Braddick and Cave,* so that it is unnecessary to discuss them at length here. The most direct way of measuring Z is to determine the number of α-particles emitted per second by a known mass of radium: this may be done either ( a ) by measuring the charge carried by the particles emitted within a known solid angle, or ( b ) by directly counting the number of particles emitted within a known very small solid angle. The most recent measurements by the “total charge” method are those of Jedrzejowski and of Braddick and Cave. The former used sources of radium (B + C) prepared in a special way and measured the charge by a quartz piezo-electrique; a value for Z of 3·50 × 10 10 was obtained. Braddick and Cave, using active deposit sources, and measuring the charge by the Townsend compensation method obtained a value of 3·69 × 10 10 . The discrepancy between these two results obtained by similar methods remains at present unexplained.

scholarly journals Some experiments concerning the counting of scintillations produced by alpha particles.— Part I

1929 ◽  
Vol 122 (789) ◽  
pp. 304-319 ◽  
Keyword(s):  
Experimental Method ◽  
Atomic Structure ◽  
Alpha Particles ◽  
Γ Radiation ◽  
Modern Conception ◽  
Scintillation Method ◽  
Γ Rays ◽  
Α Particles

Among the various methods of detecting single a-particles, the scintillation method, because of its simplicity, is often the only one applicable. When the particles are to be counted in the presence of a strong β and γ radiation, the scintillation method is indispensable, for the scintillations produced by α-particles are easily detectable on the luminous background produced by the β and γ rays, while the electrical counter is seriously disturbed by these types of radiation. Though the counting of scintillations has been constantly used as an experimental method since 1908, and practically all the fundamental data on which the modern conception of atomic structure is based, were obtained by this method, very little systematic work has been done concerning the method itself and its limitations.

scholarly journals The rate of emission of alpha particles from radium

1928 ◽  
Vol 121 (787) ◽  
pp. 367-380 ◽  
Keyword(s):  
Heat Evolution ◽  
Alpha Particles ◽  
The Other ◽  
Decomposition Products ◽  
A Value ◽  
Considerable Portion ◽  
Γ Ray ◽  
Recoil Atoms ◽  
Energy Relations ◽  
Α Particles

A knowledge of the number, Z, of α particles disintegrations taking place in unit mass of radium in unit time is of considerable importance in the interpretation of radioactive changes, and, in particular, of the energy relations involved. The heat evolution of radium and its short-lived decomposition products has been studied by a number of workers. Most of the heat production is accounted for by the energy of the a particles and recoil atoms, and in any particular experiment an allowance may be made for the β and γ ray energy absorbed. The experimental results are in agreement with the energy calculated from the number and energy of the a particles if a value is assumed for Z of about 3.7 . 10 10 . If, on the other hand, the value 3.57.10 10 obtained by Rutherford and Geiger, or the value 3.40.1010 recently published by Geiger and Werner, be taken, the calculation leaves a considerable portion of the heating effect unaccounted for, and this would involve an unidentified heatproducing mechanism in the disintegration.

scholarly journals A determination of the absolute velocity of the alpha-particles from radium C'

1936 ◽  
Vol 157 (890) ◽  
pp. 183-194 ◽  
Keyword(s):  
Accurate Determination ◽  
Maximum Error ◽  
Atomic Weight ◽  
Alpha Particles ◽  
Absolute Velocity ◽  
Group V ◽  
A Value ◽  
Radioactive Substances ◽  
Α Particles

The first accurate determination of the velocity of expulsion of the α-particles from radioactive substances was made by Rutherford and Robinson, who, by measuring magnetic and electric deflexions, found for the α-particles from radium C' Hρ = 3∙983 × 10 5 E. M. U. and V = 1∙922 × 10 9 cm./sec., the accuracy being 1 in 400. In 1926 the writer measured Hρ for the same group of α-particles and found the value 3∙993 × 10 5 E. M. U. to 1 in 1000. This result, together with the value of the faraday and Aston’s determination of the atomic weight of helium, gave V = 1∙922 × 10 9 cm./sec. Absolute velocity determinations have been made for polonium by I. Curie, and for several groups by Rosenblum and Dupouy, who found for the radium C' group V = 1∙9218 × 10 9 cm./sec. with an accuracy greater than 1 in 1000. The velocities of over fifty α-particle groups have now been measured relative to the main radium C' group; these measurements have been summarized in a paper by Lewis and Bowden. The present paper describes a new determination of Hρ for this group. Using for E/M for the aparticle a value calculated from the faraday and the atomic weight of helium the velocity and energy have been calculated. The maximum error in Hρ is estimated to be of the order of 1 in 10 4 .

Standardisation of von Willebrand Factor in Therapeutic Concentrates: Calibration of the 1st International Standard for von Willebrand Factor Concentrate (00/514)

2002 ◽  
Vol 88 (09) ◽  
pp. 380-386 ◽  
Author(s):  
Dawn Sands ◽  
Andrew Chang ◽  
Claudine Mazurier ◽  
Anthony Hubbard
Keyword(s):  
Von Willebrand Factor ◽  
International Study ◽  
Expert Committee ◽  
International Standard ◽  
A Value ◽  
Significant Difference ◽  
Factor Concentrate ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Good Agreement

SummaryAn international study involving 26 laboratories assayed two candidate von Willebrand Factor (VWF) concentrates (B and C) for VWF:Antigen (VWF:Ag), VWF:Ristocetin Cofactor (VWF:RCo) and VWF:Collagen binding (VWF:CB) relative to the 4th International Standard Factor VIII/VWF Plasma (4th IS Plasma) (97/586). Estimates of VWF:Ag showed good agreement between different methods, for both candidates, and the overall combined means were 11.01 IU/ml with inter-laboratory variability (GCV) of 10.9% for candidate B and 14.01 IU/ml (GCV 11.8%) for candidate C. Estimates of VWF:RCo showed no significant difference between methods for both candidates and gave overall means of 9.38 IU/ml (GCV 23.7%) for candidate B and 10.19 IU/ml (GCV 24.4%) for candidate C. Prior to the calibration of the candidates for VWF:CB it was necessary to calibrate the 4th IS Plasma relative to local frozen normal plasma pools; there was good agreement between different collagen reagents and an overall mean of 0.83 IU per ampoule (GCV 11.8%) was assigned. In contrast, estimates of VWF:CB in both candidates showed large differences between collagen reagents with inter-laboratory GCV’s of 40%. Candidate B (00/514) was established as the 1st International Standard von Willebrand Factor Concentrate by the WHO Expert Committee on Biological Standardisation in November 2001 with assigned values for VWF:Ag (11.0 IU/ampoule) and VWF:RCo (9.4 IU/ampoule). Large inter-laboratory variability of estimates precluded the assignment of a value for VWF:CB.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

Device Modeling of a-Si:H Alloy Solar Cells: Calibration Procedure for Determination of Model Input Parameters

1998 ◽  
Vol 507 ◽  
Author(s):  
M. Zeman ◽  
R.A.C.M.M. Van Swaaij ◽  
E. Schroten ◽  
L.L.A. Vosteen ◽  
J.W. Metselaar
Keyword(s):  
Solar Cell ◽  
Material Properties ◽  
Calibration Procedure ◽  
Model Parameters ◽  
Model Input ◽  
A Value ◽  
Input Parameters ◽  
Simulated Material ◽  
Good Agreement

ABSTRACTA calibration procedure for determining the model input parameters of standard a-Si:H layers, which comprise a single junction a-Si:H solar cell, is presented. The calibration procedure consists of: i) deposition of the separate layers, ii) measurement of the material properties, iii) fitting the model parameters to match the measured properties, iv) simulation of test devices and comparison with experimental results. The inverse modeling procedure was used to extract values of the most influential model parameters by fitting the simulated material properties to the measured ones. In case of doped layers the extracted values of the characteristic energies of exponentially decaying tail states are much higher than the values reported in literature. Using the extracted values of model parameters a good agreement between the measured and calculated characteristics of a reference solar cell was reached. The presented procedure could not solve directly an important issue concerning a value of the mobility gap in a-Si:H alloys.

Low frequency acoustic thermometry in the range 4.2–20 K with implications for the value of the gas constant

1979 ◽  
Vol 365 (1722) ◽  
pp. 349-370 ◽  
Keyword(s):  
Low Frequency ◽  
Acoustic Thermometry ◽  
A Value ◽  
New Information ◽  
Thermodynamic Temperatures ◽  
Good Agreement ◽  
Gas Thermometry

Six acoustic isotherms have been plotted in the range 4.2–20 K. When thermodynamic temperatures are calculated from their intercepts on the basis of Batuecas’s value of the gas constant ( R = 8.31441 J mol -1 K -1 ), no significant systematic departure from the results of Berry’s gas thermometry is discernible. If one assumes Berry’s work to be thermodynamically correct and the present work to be thermodynamically linear, a value of the gas constant is implied only (7 ± 27 (lσ)) R / 10 6 higher than that of Batuecas, but 152 R / 10 6 lower than that of Quinn, Colclough & Chandler (Q. C. C.). Such a value is close to that expected from a forthcoming revision of the work of Q. C. C. and is in line with recent criticisms of Rowlinson et al . of their value. If this expectation is borne out gas and acoustic thermometry will be in good agreement in this range. Final results are quoted on the basis of Batuecas’s value of the gas constant and in terms of R to facilitate their recalculation as new information on the value of the gas constant becomes available.

scholarly journals The straggling of β-particles

1929 ◽  
Vol 125 (798) ◽  
pp. 420-445 ◽  
Keyword(s):  
Classical Theory ◽  
Experimental Investigations ◽  
Theoretical Treatment ◽  
A Value ◽  
Thin Foils ◽  
New Ideas ◽  
The Subject ◽  
The Individual ◽  
Individual Particles ◽  
Α Particles

When a beam of electric particles is passed through a sheet of matter the energy of the individual particles is reduced. The loss of energy is not the same for all the particles so that particles incident on the foil with the same energy emerge with different energies. This dispersion of the energy caused by the foil is known as the "straggling" of the particles. The straggling of α-particles has been the subject of several experimental investigations, and the theory in this case was adequately developed by Bohr in 1915. In the case of β-particles, however, the straggling was not experimentally investigated until quite recently and no theoretical treatment of the phenomenon has been given, the calculations of Bohr being, as he showed, applicable only to α-particles. The purpose of the work described in this paper is to develop a theory of the straggling of β-particles by thin foils and by means of it to interpret the results of experiment. The paper is arranged as follows. In 2 an account is given of the state of the experimental work on the subject, and in particular the effect of the complications introduced by "scattering" are considered. The formula derived by Bohr for the straggling of electric particles is given in 3 and its inapplicability to β-particles demonstrated. The present calculations of the straggling of β-particles are given in 4. The theory of the straggling of electric particles resolves itself into two parts. The first deals with the dynamics of collisions between electric particles and atoms, and is the same whether we are concerned with the straggling or some other phenomena such as ionisation of "stopping power." This may be called the fundamental theory and its requirements may be summarised in the function ϕ (Q) which express the frequency of collisions in which the electric particle loses energy of amount Q. The second part of the theory is the process of calculating the straggling by means of probability theory from the function ϕ . This may be regarded as the straggling theory proper and it is the main subject of 4. When the present calculations were started it was intended to calculate the straggling on the basis of classical theory only, the value of the function ϕ on this theory being definitely known. However, after some practice with the type of calculation involved it was decided to calculate the straggling for other forms of ϕ . From the results obtained it is possible to deduce the straggling corresponding to any form which ϕ may reasonably have, and if a new theory leads to a value of ϕ different from the classical value, the straggling on the new theory may readily be determined. Alternatively this fuller treatment may be used for the reverse process of calculating from the observed straggling the value of ϕ to which it corresponds. This is considered to be the most convenient procedure and in 5 the form of ϕ which explains the experimental results is deduced. this is compared in 6 with the value of ϕ on classical theory. A brief outline is given in 7 of certain new ideas concerning the nature of collisions of electric particles with electrons and atoms.

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