64,740 research outputs found
Dependence of the thermoluminescent high-temperature ratio (HTR) of LiF:Mg,Ti detectors on proton energy and dose
The high-temperature ratio (HTR) is a parameter quantifying changes of the
shape of the high-temperature part of the LiF:Mg,Ti glow-curve after exposure
to densely ionizing radiation. It was introduced in order to estimate the
effective LET of an unknown radiation field and to correct the decreased
relative TL efficiency for high Linear Energy Transfer (LET) radiation. In the
present work the dependence of HTR on proton energy (14.5 to 58 MeV) and dose
(0.5 to 30 Gy) was investigated. All measured HTR values were at the level of
1.2 or higher, therefore significantly different from the respective value for
gamma rays (HTR is equal to 1), but HTR was found to be insensitive to changes
of proton energy above 20 MeV. As a result the relationship between HTR and
relative TL efficiency is not unequivocal. The HTR was found to be dependent on
absorbed dose even for the lowest studied doses.Comment: Manuscript has been presented at the 17th International Conference on
Solid State Dosimetry, Recife, Brasil, September 22-27,201
A geometry for optimizing nanoscale magnetic resonance force microscopy
We implement magnetic resonance force microscopy (MRFM) in an experimental
geometry, where the long axis of the cantilever is normal to both the external
magnetic field and the RF microwire source. Measurements are made of the
statistical polarization of H in polystyrene with negligible magnetic
dissipation, gradients greater than T/m within 100 nm of the magnetic
tip, and rotating RF magnetic fields over 12 mT at 115 MHz. This geometry could
facilitate the application of nanometer-scale MRFM to nuclear species with low
gyro-magnetic ratios and samples with broadened resonances, such as In spins in
quantum dots.Comment: 4 pages, 5 figure
An adjustable focusing system for a 2 MeV H- ion beam line based on permanent magnet quadrupoles
A compact adjustable focusing system for a 2 MeV H- RFQ Linac is designed,
constructed and tested based on four permanent magnet quadrupoles (PMQ). A PMQ
model is realised using finite element simulations, providing an integrated
field gradient of 2.35 T with a maximal field gradient of 57 T/m. A prototype
is constructed and the magnetic field is measured, demonstrating good agreement
with the simulation. Particle track simulations provide initial values for the
quadrupole positions. Accordingly, four PMQs are constructed and assembled on
the beam line, their positions are then tuned to obtain a minimal beam spot
size of (1.2 x 2.2) mm^2 on target. This paper describes an adjustable PMQ beam
line for an external ion beam. The novel compact design based on commercially
available NdFeB magnets allows high flexibility for ion beam applications.Comment: published in JINST (4th Feb 2013
Hot-carrier-induced deep-level defects from gated-diode measurements on MOSFETs
The reverse-bias current in the gated-diode configuration of hot-carrier degraded MOS devices was measured. It is shown that interface defects created by the degradation contribute predominantly to the generation current. The spatial distribution of the deep-level defects was obtained by means of device simulation
X-Raying the Dark Side of Venus - Scatter from Venus Magnetotail?
This work analyzes the X-ray, EUV and UV emission apparently coming from the
Earth-facing (dark) side of Venus as observed with Hinode/XRT and SDO/AIA
during a transit across the solar disk occurred in 2012. We have measured
significant X-Ray, EUV and UV flux from Venus dark side. As a check we have
also analyzed a Mercury transit across the solar disk, observed with Hinode/XRT
in 2006. We have used the latest version of the Hinode/XRT Point Spread
Function (PSF) to deconvolve Venus and Mercury X-ray images, in order to remove
possible instrumental scattering. Even after deconvolution, the flux from Venus
shadow remains significant while in the case of Mercury it becomes negligible.
Since stray-light contamination affects the XRT Ti-poly filter data from the
Venus transit in 2012, we performed the same analysis with XRT Al-mesh filter
data, which is not affected by the light leak. Even the Al-mesh filter data
show residual flux. We have also found significant EUV (304 A, 193 A, 335 A)
and UV (1700 A) flux in Venus shadow, as measured with SDO/AIA. The EUV
emission from Venus dark side is reduced when appropriate deconvolution methods
are applied; the emission remains significant, however. The light curves of the
average flux of the shadow in the X-ray, EUV, and UV bands appear different as
Venus crosses the solar disk, but in any of them the flux is, at any time,
approximately proportional to the average flux in a ring surrounding Venus, and
therefore proportional to the average flux of the solar regions around Venus
obscuring disk line of sight. The proportionality factor depends on the band.
This phenomenon has no clear origin; we suggest it may be due to scatter
occurring in the very long magnetotail of Venus.Comment: This paper has been accepted in The Astrophysical Journa
"Magnetoscan": A Modified Hall Probe Scanning Technique for the Detection of Inhomogeneities in Bulk High Temperature Superconductors
We present a novel technique for the investigation of local variations of the
critical current density in large bulk superconductors. In contrast to the
usual Hall probe scanning technique, the sample is not magnetized as a whole
before the scan, but locally by a small permanent magnet, which is fixed near
the Hall probe, during the scanning process. The resulting signal can be
interpreted as a qualitative measure of the local shielding currents flowing at
the surface.Comment: 8 pages, 4 figure
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