Enhanced DNA Damage Induced by Secondary Electron Emission from a Tantalum Surface Exposed to Soft X Rays

2006 ◽  
Vol 165 (3) ◽  
pp. 365-371 ◽  
Author(s):  
Zhongli Cai ◽  
Pierre Cloutier ◽  
Darel Hunting ◽  
Léon Sanche
Keyword(s):  
Dna Damage ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
X Rays

scholarly journals The efficiency of secondary electron emission

1933 ◽  
Vol 139 (838) ◽  
pp. 436-447 ◽  
Keyword(s):  
Velocity Distribution ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Inelastic Collisions ◽  
Secondary Beam ◽  
X Rays ◽  
Secondary Electrons ◽  
The Third ◽  
Primary Electrons

The velocity distribution of the secondary electrons produced by bombarding a metallic face with a stream of primary electrons has been a matter of interest ever since the beginning of the study of secondary electron emission. As early as in 1908, Richardson and von Baeyer independently showed that slow moving electrons were copiously reflected from conducting faces. Farnsworth showed that for primary electrons having velocities less than 9 volts, most of the secondary electrons had velocities equal to the primary. As the primary potential was increased, the percentage of the reflected electrons decreased gradually but was appreciable at 110 volts. Davisson and Kunsman obtained reflected electrons even at primary potentials of 1000 and 1500 volts in the cases of some metal faces. At higher potentials we have also the electrons that undergo the Davisson and Germer scattering from the many crystal facets on the bombarded targets. As the potential is increased, the number of electrons with low velocities increases steadily and at large applied potentials, we have a large percentage of these in the secondary beam. These conclusions followed as a result of the work of Farnsworth who studied the distribution of velocities of the secondary electrons by the retarding potential method. He did not actually calculate the energy distribution from his curves but has drawn attention to the above conclusions. A careful investigation of the velocity distribution of the secondary electrons from various conducting faces was made by Rudberg at primary potentials ranging up to about 1000 volts. He adopted a magnetic deflection method similar to the one used in the analysis of the β rays and of the electrons excited by X-rays. The method had indeed been used by previous workers for the study of secondary emission, but Rudberg improved the technique considerably and obtained better focussing conditions. His results suggest that there are three groups of electrons in the secondary beam. The first group contains electrons returning with the same velocity as the primary. In the second group of electrons, we have those which undergo inelastic collisions with the orbital and structure electrons and hence are returned with some loss of energy. Richardson has drawn attention to the well-marked minimum between the two groups in Rudberg’s curves and infers that free electrons are not involved in the collisions. Finally there is the third group which contains the slow secondary electrons. The second and the third groups appear to be definitely connected with each other since they are both predominant at high primary potentials and become negligible at low primary potentials. Richardson suggests that the third group is the result of the excitation accompanying the inelastic collisions.

scholarly journals Total secondary electron emission from polycrystalline Nickel

1930 ◽  
Vol 128 (807) ◽  
pp. 41-56 ◽  
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Considerable Proportion ◽  
Secondary Beam ◽  
X Rays ◽  
Applied Potential ◽  
Polycrystalline Nickel ◽  
Low Velocity ◽  
Secondary Electrons

The importance of secondary electron emission in its relation to the excitation of soft X-rays has been pointed out in a recent paper by Prof. O. W. Richardson. He has shown that at every potential where there is an increased excitation of soft X-rays, there is correspondingly an increase in the emission of secondary electrons, and has discussed at some length the mechanism of the generation of secondary electrons. It was therefore felt that a much clearer idea of the phenomenon of soft X-ray excitation from metallic surfaces could be had by studying the secondary electron emission from polycrystalline and single crystal faces. As early as in 1908 Richardson showed that slowly moving electrons are reflected in considerable proportion from metallic plates. Davisson and Kunsman, in a series of papers commencing from 1921, showed that at low voltages up to about 9 volts most of the secondary electrons were purely reflected electrons with velocities the same as the incident electrons. The percentage of the reflected electrons fell rapidly as the applied potential was increased above 9 volts, while that of low velocity electrons increased steadily. Farnsworth, with improved apparatus, added much valuable information regarding the generation of secondary electrons and the conditions operating in such cases. These observers showed that the total emission of secondary electrons from a metal surface depended on the applied potential, the nature of the surface and the previous heat treatment of the metal. They also found that the ratio of the secondary beam to the primary increases with applied potential and becomes greater than 1 after a certain potential, depending on the nature of the bombarded metal, is reached.

Characteristics of secondary electron emission from CsI induced by x rays with energies up to 100 keV

1993 ◽  
Vol 74 (12) ◽  
pp. 7506-7509 ◽  
Author(s):  
A. Gibrekhterman ◽  
A. Akkerman ◽  
A. Breskin ◽  
R. Chechik
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
X Rays

scholarly journals Total secondary electron emission from a single crystal face of nickel

1930 ◽  
Vol 128 (807) ◽  
pp. 57-62 ◽  
Keyword(s):  
Single Crystal ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Experimental Results ◽  
X Rays ◽  
Polycrystalline Nickel ◽  
Crystal Face ◽  
Nickel Crystal

In an accompanying paper, secondary electron experiments on ordinary nickel are described. These were conducted mainly to study the conditions of secondary electron emission and to find how far the experimental results of Retry on a polycrystalline nickel target could be reproduced. It was found that a large number of inflections were obtained some of which coincided with Petry’s values. Most of these inflections had corresponding values in Thomas’s results for soft X-rays from nickel. In this paper, the results of experiments on total secondary electron emission from the 100 face of a nickel crystal are given.

Historical Introduction

1977 ◽  
Vol 35 ◽  
pp. 2-5
Author(s):  
R. D. Heidenreich
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
50Th Anniversary ◽  
Secondary Emission ◽  
Wave Nature ◽  
Nobel Prize In Physics ◽  
Primary Electrons ◽  
The U.S ◽  
Mutual Agreement

This program has been organized by the EMSA to commensurate the 50th anniversary of the experimental verification of the wave nature of the electron. Davisson and Germer in the U.S. and Thomson and Reid in Britian accomplished this at about the same time. Their findings were published in Nature in 1927 by mutual agreement since their independent efforts had led to the same conclusion at about the same time. In 1937 Davisson and Thomson shared the Nobel Prize in physics for demonstrating the wave nature of the electron deduced in 1924 by Louis de Broglie.The Davisson experiments (1921-1927) were concerned with the angular distribution of secondary electron emission from nickel surfaces produced by 150 volt primary electrons. The motivation was the effect of secondary emission on the characteristics of vacuum tubes but significant deviations from the results expected for a corpuscular electron led to a diffraction interpretation suggested by Elasser in 1925.

SEM and Auger microanalysis studies of Cu-Be dynode surfaces at each activation condition

1978 ◽  
Vol 36 (1) ◽  
pp. 524-525
Author(s):  
T. Koshikawa ◽  
Y. Fujii ◽  
E. Sugata ◽  
F. Kanematsu
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Life Time ◽  
Activation Process ◽  
Beam Diameter ◽  
Activation Temperature ◽  
Electron Multiplier ◽  
Activation Condition ◽  
Activation Conditions

The Cu-Be alloys are widely used as the electron multiplier dynodes after the adequate activation process. But the structures and compositions of the elements on the activated surfaces were not studied clearly. The Cu-Be alloys are heated in the oxygen atmosphere in the usual activation techniques. The activation conditions, e.g. temperature and O2 pressure, affect strongly the secondary electron yield and life time of dynodes.In the present paper, the activated Cu-Be dynode surfaces at each condition are investigated with Scanning Auger Microanalyzer (SAM) (primary beam diameter: 3μmϕ) and SEM. The commercial Cu-Be(2%) alloys were polished with Cr2O3 powder, rinsed in the distilled water and set in the vacuum furnance.Two typical activation condition, i.e. activation temperature 730°C and 810°C in 5x10-3 Torr O2 pressure were chosen since the formation mechanism of the BeO film on the Cu-Be alloys was guessed to be very different at each temperature from the results of the secondary electron emission measurements.

SEM analysis of DC magnetron sputtered beryllium films

1988 ◽  
Vol 46 ◽  
pp. 960-961
Author(s):  
E. F. Lindsey ◽  
C. W. Price ◽  
E. L. Pierce ◽  
E. J. Hsieh
Keyword(s):  
Fine Structure ◽  
Electron Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Ion Beam ◽  
Secondary Electron Emission ◽  
Sem Analysis ◽  
Fused Silica ◽  
Grain Structure ◽  
Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

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