The spin precession frequency of muons stored in the (g-2) storage ring has been analyzed for evidence of Lorentz and CPT violation. Two Lorentz and CPT violation signatures were searched for a ...nonzero delta omega a(=omega a mu+ - omega a mu-) and a sidereal variation of omega a mu+/-). No significant effect is found, and the following limits on the standard-model extension parameters are obtained: bZ = -(1.0+/-1.1) x 10(-23) GeV; (m mu dZ0 + HXY)=(1.8+/-6.0) x 10(-23) GeV; and the 95% confidence level limits b perpendicular mu+ <1.4 x 10(-24) GeV and b perpendicular mu- <2.6 x 10(-24) GeV.
A Hall probe device has been built to measure the radial component of the magnetic field in the muon (g-2) storage ring at Brookhaven National Laboratory. The ultraprecise (g-2) magnet provides a ...dominantly vertical magnetic field of about
1.45
T
. In order to limit the vertical shift of the muon orbit, the average radial field component should be no more than 5×10
−5 of the vertical field. Our measurements with the Hall probe device achieved an accuracy of 1×10
−5, which is one of the most precise measurements with Hall probes. This provides adequate accuracy for shimming and control of the radial field.
The superconducting inflector for the BNL g-2 experiment Yamamoto, A; Makida, Y; Tanaka, K ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2002, Letnik:
491, Številka:
1-2
Journal Article
Recenzirano
The muon g-2 experiment at Brookhaven National Laboratory (BNL) has the goal of determining the muon anomalous magnetic moment, aμ(=(g-2)/2), to the very high precision of 0.35 parts per million and ...thus requires a storage ring magnet with great stability and homogeneity. A super-ferric storage ring has been constructed in which the field is to be known to 0.1ppm. In addition, a new type of air core superconducting inflector has been developed and constructed, which successfully serves as the injection magnet. The injection magnet cancels the storage ring field, 1.5T, seen by the entering muon beam very close to the storage ring aperture. At the same time, it gives negligible influence to the knowledge of the uniform main magnetic field in the muon storage region located at just 23mm away from the beam channel. This was accomplished using a new double cosine theta design for the magnetic field which traps most of the return field, and then surrounding the magnet with a special superconducting sheet which traps the remaining return field. The magnet is operated using a warm-to-cold cryogenic cycle which avoids affecting the precision field of the storage ring. This article describes the design, research development, fabrication process, and final performance of this new type of superconducting magnet.
Major components are in an advanced state of construction for a 7 meter radius 0.1 PPM precision storage ring. Detailed techniques are planned for static shimming of the assembly to at least 10 PPM ...magnetic field uniformity prior to the use of field correction coils. An air gap behind each ultra-pure iron pole piece strongly decouples the aperture field shape from the properties of the 1006 iron yoke. Iron wedges whose thickness varies across the width of the poles with slope of /spl sim/1/60 are used to eliminate the gradient produced by the C-magnet shape required for open access for the decay electron counter on the inside radius of the storage ring magnet. These wedges are 10 cm in azimuthal length and can be radially adjusted for short wavelength field adjustments. A horizontal motion of 50 /spl mu/m effectively adjusts the 10 cm half-gap aperture by 1 /spl mu/m (or 10 PPM). This and other techniques to adjust dipole, quadrupole, sextuple, etc. multipoles will be described.< >
The Booster requires highly variable magnet cycles. When B/spl dot/ is large, eddy current induced sextupole, etc., in the dipole vacuum chamber (VC) is large, with a much smaller contribution from ...magnet ends. Simple passive coils excited automatically by transformer action cancel the B/spl dot/ induced sextupole. A self correction coil is not required for the quadrupoles, since B/spl dot/ induced aberrations are very small (<1.0/spl times/10/sup -4/ at full aperture). Iron magnetization does not produce dipole or quadrupole magnet multipole aberrations, so these magnets have been effectively made independent of unwanted multipoles for all cycles. However, variations in the transfer functions and thus the Booster tune have not been automatically eliminated. Iron magnetization contributions are almost matched, but the B/spl dot/ induced field retardation in the dipoles VC is larger than in the quadrupoles. Results of measurements will be presented, plus a simple system to overcome the mismatch and make the tune independent of B/spl dot/. Properties of special lattice magnets and their corrections will also be described.< >
A muon g-2 experiment (E821) at the AGS requires knowledge of the magnetic field over muon orbits at the level of 0.1 ppm. The superconducting inflector involves a double cosine theta winding; this ...design approximately cancels its fringe field. Nevertheless its residual field would effect the homogeneity of the storage ring magnetic field. A method of using a superconducting sheet surrounding the inflector to further reduce the fringe field was proposed by one of the authors, W. Meng. An experimental program to explore this technique is described. Part of the test results are presented.< >
In the muon
(
g
-
2
)
experiment at Brookhaven National Laboratory, the spin precession frequency
ω
a
is obtained from a standard
χ
2
minimization fit applied to the time distribution of decay ...electrons. The unusually high accuracy
(
∼
0.5
ppm
)
of the experiment puts stringent requirements on the quality of the fit and the level of understanding of the statistical properties of the fitted parameters. We discuss the properties of the fits and their implications on the derived value for
ω
a
, including estimates of the effect of an imperfect fit function, methods of including additional external information to reduce the error, the effects of splitting the data into many smaller subsets of data, applying different weighting methods to the data using energy information, and various tests of data suitability.
Improved limit on the muon electric dipole moment Bennett, G. W.; Bousquet, B.; Brown, H. N. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
09/2009, Letnik:
80, Številka:
5
Journal Article
Summary
Background
Atopic dermatitis (AD) is an inflammatory skin disease arising as a result of immune system and skin barrier defects. Topical corticosteroids are safe and effective treatments for ...AD, when used in short courses. Prolonged use is associated with skin barrier damage. Topical calcineurin inhibitors are alternative immune‐modulating treatments for AD purported to have no negative effects on the skin barrier.
Objectives
To compare the effects of betamethasone valerate 0·1% cream (BMVc) and tacrolimus 0·1% ointment (TACo) on the skin barrier.
Methods
Twenty volunteers with quiescent AD (no active signs for 6 months) participated in a randomized observer‐blind study, wherein BMVc was applied to one forearm and TACo to the other, twice daily for 4 weeks. The biophysical/biological properties of the stratum corneum were assessed before and after treatment. Nine volunteers with active disease and 10 with healthy skin were assessed at untreated sites.
Results
BMVc significantly reduced skin barrier function, integrity and cohesion, and the levels of pyrrolidone carboxylic acid (PCA) and urocanic acid (UCA) towards the subclinical barrier defect observed in patients with AD (nonlesional sites). TACo preserved skin barrier function, integrity, cohesion and PCA and UCA levels, while significantly increasing skin hydration to levels comparable with healthy skin. Both treatments reduced skin surface pH and trypsin‐like protease activity, with TACo doing so to a significantly greater degree.
Conclusion
In quiescent AD, 4 weeks of BMVc treatment adversely affected the biophysical properties of the skin and reduced the levels of natural moisturizing factor, whereas TACo improved the condition of the skin barrier.
What's already known about this topic?
Skin barrier breakdown is a key event in the development of atopic dermatitis (AD).
Prolonged use of potent or moderately potent topical corticosteroids (TCS) disrupts the structure of the skin barrier, thins the stratum corneum (SC) and as a result reduces permeability barrier function.
The effect of topical calcineurin inhibitors (TCI) on the skin barrier is still unclear.
What does this study add?
In subjects with quiescent AD, application of betamethasone valerate reduced skin barrier function, SC integrity and natural moisturizing factor (NMF) levels towards the level of the subclinical barrier defect observed in active disease at nonlesional sites.
By comparison, a topical formulation containing tacrolimus preserved barrier function, SC integrity and NMF levels.
This raises the importance of better understanding how to combine TCS and TCI to optimize effects on the skin barrier.
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