Stopping powers of polycarbonate for 0.36–5.94-MeV protons and 1.0–24.0-MeV α particles

2003 ◽  
Vol 94 (3) ◽  
pp. 2080-2085 ◽  
Author(s):  
J. Räisänen ◽  
W. H. Trzaska ◽  
T. Alanko ◽  
V. Lyapin ◽  
L. E. Porter
Keyword(s):  
Mev Protons ◽  
Α Particles

The Influence of the Extreme Fluences of 8 MeV Protons on Characteristics of SiC Nuclear Detectors Produced by Al Implantation

2007 ◽  
Vol 556-557 ◽  
pp. 961-964 ◽  
Author(s):  
Alexander M. Ivanov ◽  
Nikita B. Strokan ◽  
Alexander A. Lebedev ◽  
Vitalii V. Kozlovski
Keyword(s):  
Experimental Data ◽  
Collection Efficiency ◽  
Charge Collection ◽  
Carrier Localization ◽  
Charge Collection Efficiency ◽  
Radiation Induced ◽  
Nuclear Detectors ◽  
Two Parameter ◽  
Mev Protons ◽  
Α Particles

The charge collection efficiency (ССЕ) of SiC-detectors preliminarily irradiated with 8 MeV protons at a fluence of 1014 cm-2 has been studied. Nuclear spectrometric techniques with 5.4 MeV α-particles were employed to test the detectors. The concentration of primarily created defects was estimated to be 4×1016 cm-3. A strong compensation of SiC was observed, which allowed connection of the structure in the forward mode. The experimental data obtained were processed using a simple two-parameter model of signal formation. The model makes it possible to separate the contributions of electrons and holes to the ССЕ. An additional irradiation at a fluence of 2×1014 cm-2 reduced the ССЕ value by a factor of 2 and gave rise to polarization. The latter indicates that radiation-induced centers are not only actively involved in carrier localization (with a decrease in the lifetime), but also in transformation of the electric field within the detector.

Energy per ion pair for electrons in gases and gas mixtures

1952 ◽  
Vol 211 (1104) ◽  
pp. 75-85 ◽  
Keyword(s):  
Energy Expenditure ◽  
Close Agreement ◽  
Small Variation ◽  
Ion Pair ◽  
The Other ◽  
Ion Current ◽  
End Effect ◽  
Primary Electrons ◽  
Mev Protons ◽  
Α Particles

The energy expenditure per ion pair, V , for electrons in argon, helium, hydrogen, nitrogen, air, oxygen and methane is determined using ion chambers and proportional counters with terminals which correct for ‘end-effect’. Experiments using 37 A and tritium as sources of ionizing electrons are performed. Curves of ion current against percentage of argon admixed with the other gases are plotted. The variation of V with energy of the ionizing electrons is investigated for nitrogen between the limits 200 eV and 46*7 keV for the primary electrons and only a small variation is found. The ratio V gas/ V argon is given in each case and is found to be almost identical to the corresponding ratio for ionization by 340 MeV protons. Examination of previous work with α- particles suggests close agreement with the values for electrons and protons.

Uniformity of Properties of 4H-SiC CVD Films under Exposure to Radiation

2011 ◽  
Vol 679-680 ◽  
pp. 177-180
Author(s):  
Alexander M. Ivanov ◽  
Nikita B. Strokan ◽  
N.A. Scherbov ◽  
Alexander A. Lebedev
Keyword(s):  
Electrical Properties ◽  
Cross Section ◽  
Structural Defects ◽  
Physico Chemical ◽  
Radiation Induced ◽  
Spectrometry Technique ◽  
Final System ◽  
Radiation Centers ◽  
Mev Protons ◽  
Α Particles

Non-uniformities of electrical properties of 4H-SiC CVD films have been revealed using physico-chemical reactions occurring upon introduction of radiation-induced structural defects. Primary knocked-out atoms and vacancies actively interact with defects of the starting material and thereby form the final system of radiation centers. The samples were irradiated with 900 keV electrons and 8 MeV protons at doses not leading to conductivity compensation ( 7.5  1012 cm–2) and a dose of 6  1014 cm–2 causing deep compensation. Capacitance methods demonstrated that characteristics of samples ~3 mm in size are not identical. The nuclear spectrometry technique, which enables microprobing of samples, demonstrated individual behavior of separate parts of a film with areas of tens of square micrometers (the dimension of α-particles track cross-section).

Alignment of small He-Bubbles during in situ deformation of Al-foils

1978 ◽  
Vol 36 (1) ◽  
pp. 396-397
Author(s):  
E. Ruedl ◽  
P. Schiller
Keyword(s):  
Fusion Reactor ◽  
Matrix Material ◽  
Fusion Reactors ◽  
First Wall ◽  
Potential Matrix ◽  
In Situ Deformation ◽  
Α Particles ◽  
Metal Aluminium

The low Z metal aluminium is a potential matrix material for the first wall in fusion reactors. A drawback in the application of A1 is the rel= atively high amount of He produced in it under fusion reactor conditions. Knowledge about the behaviour of He during irradiation and deformation in Al, especially near the surface, is therefore important.Using the TEM we have studied Al disks of 3 mm diameter and 0.2 mm thickness, which were perforated at the centre by double jet polishing. These disks were bombarded at∽200°C to various doses with α-particles, impinging at any angle and energy up to 1.5 MeV at both surfaces. The details of the irradiations are described in Ref.1. Subsequent observation indicated that in such specimens uniformly distributed He-bubbles are formed near the surface in a layer several μm thick (Fig.1).After bombardment the disks were deformed at 20°C during observation by means of a tensile device in a Philips EM 300 microscope.

Formation of α clusters in dilute neutron-rich matter

Science ◽  
2021 ◽  
Vol 371 (6526) ◽  
pp. 260-264 ◽  
Author(s):  
Junki Tanaka ◽  
Zaihong Yang ◽  
Stefan Typel ◽  
Satoshi Adachi ◽  
Shiwei Bai ◽  
...  
Keyword(s):  
Cross Sections ◽  
Cluster Formation ◽  
Reaction Cross ◽  
Skin Thickness ◽  
Neutron Skin ◽  
Heavy Nuclei ◽  
Α Decay ◽  
Neutron Skin Thickness ◽  
Reaction Cross Sections ◽  
Α Particles

The surface of neutron-rich heavy nuclei, with a neutron skin created by excess neutrons, provides an important terrestrial model system to study dilute neutron-rich matter. By using quasi-free α cluster–knockout reactions, we obtained direct experimental evidence for the formation of α clusters at the surface of neutron-rich tin isotopes. The observed monotonous decrease of the reaction cross sections with increasing mass number, in excellent agreement with the theoretical prediction, implies a tight interplay between α-cluster formation and the neutron skin. This result, in turn, calls for a revision of the correlation between the neutron-skin thickness and the density dependence of the symmetry energy, which is essential for understanding neutron stars. Our result also provides a natural explanation for the origin of α particles in α decay.

scholarly journals Unusual enhancement of ~ 30 MeV proton flux in an ICME sheath region

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Mitsuo Oka ◽  
Takahiro Obara ◽  
Nariaki V. Nitta ◽  
Seiji Yashiro ◽  
Daikou Shiota ◽  
...  
Keyword(s):  
Shock Front ◽  
Energetic Particle ◽  
Leading Edge ◽  
Solar Energetic Particle ◽  
Interplanetary Shock ◽  
Proton Event ◽  
Sheath Region ◽  
Time Profiles ◽  
Energetic Particle Flux ◽  
Mev Protons

AbstractIn gradual Solar Energetic Particle (SEP) events, shock waves driven by coronal mass ejections (CMEs) play a major role in accelerating particles, and the energetic particle flux enhances substantially when the shock front passes by the observer. Such enhancements are historically referred to as Energetic Storm Particle (ESP) events, but it remains unclear why ESP time profiles vary significantly from event to event. In some cases, energetic protons are not even clearly associated with shocks. Here, we report an unusual, short-duration proton event detected on 5 June 2011 in the compressed sheath region bounded by an interplanetary shock and the leading edge of the interplanetary CME (or ICME) that was driving the shock. While < 10 MeV protons were detected already at the shock front, the higher-energy (> 30 MeV) protons were detected about four hours after the shock arrival, apparently correlated with a turbulent magnetic cavity embedded in the ICME sheath region.

SPALLATION YIELDS FROM HIGH ENERGY PROTON BOMBARDMENT OF HEAVY ELEMENTS

1957 ◽  
Vol 35 (1) ◽  
pp. 21-37 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Heavy Elements ◽  
Collective Effects ◽  
Comparison With Experiment ◽  
Energy Proton ◽  
Stringent Test ◽  
Neutron Evaporation ◽  
Nuclear Processes ◽  
Mev Protons

The Monte Carlo calculations of McManus and Sharp (unpublished) for the prompt nuclear processes occurring upon bombardment of heavy elements by 400 Mev. protons are combined with a description of the subsequent neutron evaporation to determine spallation cross sections for comparison with experiment. The model employed is a schematic one which suppresses the detailed characteristics of individual nuclei, but gives the over-all behavior to be expected. Many-particle and collective effects such as alpha particle emission and fission are ignored. The computed cross sections are presented in a variety of different graphical forms which illustrate quantitatively the qualitative picture of high energy reactions first given by Serber (1947). The calculations are in general agreement with existing data when fission is not an important effect, but the agreement does not imply a very stringent test of the various features of the model.

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