Slow Positron Beam with Small Energy Spread in the Magnetic Field Using Reflection Type Remoderator

1997 ◽  
Vol 255-257 ◽  
pp. 677-679 ◽  
Author(s):  
Yoshihide Honda ◽  
Masaki Maekawa ◽  
N. Kimura ◽  
T. Kozawa ◽  
S. Nishijima ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Positron Beam ◽  
Energy Spread ◽  
Small Energy ◽  
Slow Positron ◽  
The Magnetic Field

scholarly journals A total reflection high-energy positron diffraction station at the KEK-SPF

2014 ◽  
Vol 70 (a1) ◽  
pp. C1613-C1613
Author(s):  
Ken Wada ◽  
Masaki Maekawa ◽  
Yuki Fukaya ◽  
Izumi Mochizuki ◽  
Toshio Hyodo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Diameter ◽  
Small Diameter ◽  
Positron Beam ◽  
High Energy ◽  
Total Reflection ◽  
Present System ◽  
Slow Positron ◽  
Reconstructed Surface ◽  
The Magnetic Field

A high-intensity mono-energetic positron beam generated by using a linear electron accelerator (linac) provides total reflection high-energy positron diffraction (TRHEPD) researches at Slow Positron Facility (SPF), KEK [1,2]. A pulsed 50-Hz electron beam generated with a dedicated linac (operated at 55 MeV, 0.6 kW) is injected on a Ta converter and causes fast positron-electron pair creation through bremsstrahlung. The positrons showering down on 25 μm-thick W foils, are moderated to thermal energy, and a fraction spontaneously comes out of the foils with an energy of 3 eV owing to the negative work function. The positron converter/moderator assembly is held at an electrostatic voltage of 15 kV for TRHEPD experiment. The emitted positrons are consequently accelerated to 15 keV as they enter the grounded beam-line and are guided by the magnetic field of about 0.015 T to the TRHEPD station. For diffraction experiments, positrons transported by the magnetic field have to be first released into a nonmagnetic region. Since the released positron beam has a large diameter, a brightness-enhancement unit is effectively used to achieve a small-diameter and highly-parallel beam with a sufficient flux. The linac-based positron beam gives about 60 times intensified diffraction pattern from a Si(111)-7x7 reconstructed surface compared to a previous result with a Na-22-based positron beam [3]. An improved signal-to-noise ratio in the obtained pattern due to the intensified beam allowed an observation of clear fractional-order spots in the higher Laue-zones, which had not been observed previously. The much intensified beam with the present system allows adjustment of the sample orientation without accumulating the positron signals. With the brightness enhanced beam, several remarkable results have been obtained efficiently by users of this facility. (Everybody is invited to use KEK Slow Positron Facility through approval of his/her research proposal.)

scholarly journals Some initial results of simulating a positron beam system by using SIMION

2021 ◽  
Vol 7 (3) ◽  
pp. 17-24
Author(s):  
Thanh Long Cao ◽  
Trung Hieu Nguyen ◽  
Quoc Dung Tran ◽  
Dong Phuong Huynh
Keyword(s):  
Magnetic Field ◽  
Positron Beam ◽  
Material Research ◽  
Slow Positron ◽  
Beam Trajectory ◽  
Beam System ◽  
Simulation Results ◽  
Initial Results

Slow Positron Beam (PB) is an important device in the study of positron physics andtechniques, especially in material research. For the purpose of conceptual designing a PB system, we have simulated a PB system with the parameters of an existing system – SPONSOR, using SIMION software. The simulation results have been compared with the SPONSOR published results. The effect of magnetic field in controlling beam trajectory has been investigated in the preaccelerated and accelerated stages. The simulation results of using steering coils to adjust the beam trajectory are also presented in this report.

Electron energy spread in the magnetic field of a betatron

1972 ◽  
Vol 15 (8) ◽  
pp. 1199-1200
Author(s):  
V. V. Evstigneev ◽  
V. V. Kashkovskii ◽  
G. V. Milyutin
Keyword(s):  
Magnetic Field ◽  
Electron Energy ◽  
Energy Spread ◽  
The Magnetic Field

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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