共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Pohl F. Biraben C.A.N. Conde C. Donche Gay T.W. Hänsch F.J. Hartmann P. Hauser V.W. Hughes O. Huot P. Indelicato P. Knowles F. Kottmann Y. W. Liu F. Mulhauser F. Nez C. Petitjean P. Rabinowitz J.M.F. dos Santos L.A. Schaller H. Schneuwly W. Schott L.M. Simons D. Taqqu F. Trehin J.F.C.A. Veloso 《Hyperfine Interactions》2000,127(1-4):161-166
The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic
hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision
on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS
proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known.
The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of
long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that
in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of
the order of 1 μs.
The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon
entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength,
and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI
coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
K. R. Allakhverdiev M. Ö. Yetis T. K. Baykara S. M. T. Özbek E. Yu. Salaev 《Laser Physics》2011,21(3):598-600
Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described
and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra
(400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear
materials of GaSe
x
S1 − x
(0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding
to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working
or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation
of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3
ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10−4−1 × 10−4 W/cm2) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10−4−1.5 × 10−4 W/cm2) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10−4–4.6 × 10−4 W/cm2) at 1360 nm. Threshold damage density is more than 10 MW/cm2 at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators. 相似文献
3.
P. Kammel V. A. Andreev D. V. Balin R. M. Carey T. Case D. B. Chitwood S. M. Clayton K. M. Crowe J. Deutsch P. T. Debevec P. U. Dick A. Dijksman J. Egger D. Fahrni A. A. Fetisov S. J. Freedman V. A. Ganzha B. Gartner J. Govaerts F. E. Gray F. J. Hartmann W. D. Herold D. W. Hertzog V. I. Jatsoura A. G. Krivshich B. Lauss E. M. Maev O. E. Maev V. E. Markushin C. J. G. Onderwater C. Petitjean G. E. Petrov C. C. Polly R. Prieels S. M. Sadetsky G. N. Schapkin R. Schmidt G. G. Semenchuk M. Soroka A. A. Vorobyov N. I. Voropaev 《Hyperfine Interactions》2001,138(1-4):435-443
The aim of the μCap experiment is a 1% measurement of the singlet capture rate Λ
S
for the basic electro-weak reaction μ + p → n + νμ. This observable is sensitive to the weak form-factors of the nucleon, in particular to the induced pseudoscalar coupling
constant g
P
. It will provide a rigorous test of theoretical predictions based on the Standard Model and effective theories of QCD. The
present method is based on high precision lifetime measurements of μ− in hydrogen gas and the comparison with the free μ+ lifetime. The μ− experiment will be performed in ultra-clean, deuterium-depleted H2 gas at 10 bar. Low density compared to liquid H2 is chosen to avoid uncertainties due to ppμ formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and
detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering
75% of 4π.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
T. Prokscha E. Morenzoni K. Deiters F. Foroughi D. George R. Kobler V. Vrankovic 《Hyperfine Interactions》2004,159(1-4):385-388
At the Paul Scherrer Institute (PSI, Villigen, Switzerland) a new high-intensity muon beam line with momentum p < 40 MeV/c is currently being commissioned. The beam line is especially designed to serve the needs of the low-energy, polarized
positive muon source (LE-μ+) and LE-μ SR spectrometer at PSI. The beam line replaces the existing μ E4 muon decay channel. A large acceptance is accomplished
by installing two solenoidal magnetic lenses close to the muon production target E that is hit by the 590-MeV PSI proton beam.
The muons are then transported by standard large aperture quadrupoles and bending magnets to the experiment. Several slit
systems and an electrostatic separator allow the control of beam shape, momentum spread, and to reduce the background due
to beam positrons or electrons. Particle intensities of up to 3.5 × 108 μ+/s and 107 μ−/s are expected at 28 MeV/c beam momentum and 1.8 mA proton beam current. This will translate into a LE-μ+ rate of 7,000/s being available at the LE-μ SR spectrometer, thus achieving μ+ fluxes, that are comparable to standard μ SR facilities. 相似文献
5.
B. M. Forster J. M. Bailey G. A. Beer J. L. Beveridge J. H. Brewer W. N. Hardy T. M. Huber K. R. Kendall A. R. Kunselman J. A. Macdonald G. M. Marshall G. R. Mason A. Olin M. Senba J. B. Warren 《Hyperfine Interactions》1991,65(1-4):1007-1013
Muonic hydrogen isotopes (μ− p, μ− d, and μ−t) are simple quantum mechanical systems ideally suited for studies of numerous fundamental phenomena in electroweak and strong
interactions as well as in applied areas such as muon chemistry or muon catalyzed fusion.
Emission of muonic hydrogen isotopes into vacuum helps to overcome the limitations which are normally imposed on conventional
investigations with gaseous and liquid targets. A proof of principle experiment for this new technique was performed at TRIUMF
last year. Negative muons with 30 MeV/c momentum were stopped in a thin film of solid hydrogen and produced very low energy μ−d in vacuum. The distribution center of the normal velocity components of emitted μ−d atoms was measured to be ∼1 cm/μs. The yield of μ−d in vacuum is an increasing function of H2 film thickness δ up to a value of δ≥1 mm. 相似文献
6.
Hans-Kristian Walter Klaus Jungmann 《Zeitschrift fur Physik C Particles and Fields》1992,56(Z1):S135-S142
The experimental status of generation number violating muon and kaon decays is reviewed. We concentrate on three experiments
with a large PSI contribution, neutrinoless muon-electron conversion, muonium-antimuonium conversion and the decayK
+→π
+. The SINDRUM II experiment at PSI searches for the coherent conversion of a muon into an electron in titanium. The design
and construction of the SINDRUM II detector and the results of the first data-taking period in 89 are presented. In total
3.2 million events have been analyzed and no candidate for the processμ
−
Ti→e
+
Ti has been found. Using two independent determinations of the total number of muon stops an upper limit ofB
μe
<4.4×10−12 (90% C.L.) is obtained. The plans to lower the sensitivity by two orders of magnitude are discussed. A muonium-antimuonium
conversion experiment is being set up at PSI using the refurbished SINDRUM I detector. The goal of the experiment is to improve
the sensitivity for the effective coupling constant
by a factor of ∼100. Finally a new proposal E865 has been accepted at BNL to improve the sensitivity for the branching ratio
of the decayK
+→π
+ by a factor 70 to 3×10−12.
Representing the SINDRUM II Collaboration: (ETH Zürich, Univ. Zürich, Paul Scherrer Institute Villigen, RWTH Aachen, Univ.
Tbilisi) 相似文献
7.
E. M. Maev V. A. Andreev T. A. Case K. M. Crowe P. U. Dick A. Dijksman J. Egger D. Fahrni A. A. Fetisov V. A. Ganzha F. J. Hartmann P. Kammel A. G. Krivchitch O. E. Maev C. Petitjean G. E. Petrov R. Prieels S. M. Sadetsky G. N. Schapkin R. Schmidt G. G. Semenchuk M. Soroka A. A. Vorobyov N. I. Voropaev 《Hyperfine Interactions》2001,138(1-4):451-457
A new experiment is under preparation with the aim to improve considerably the present knowledge of the rate Λ
s
, which should be measured on a level of 1% or better, for the basic electroweak capture reaction of a negative muon on the
free proton μp
1s
→ n + νμ. The capture rate will be determined by measuring the lifetime of μ− stopped in ultra pure hydrogen at 10 bar pressure and comparing it with the lifetime of the unbound μ+. A new experimental method was developed for this project which should allow measuring the μ− lifetime with at least 10 ppm precision. The basic element of the detector is operating in the hydrogen gas time projection
chamber (TPC) surrounded by multi-wire proportional chambers (MWPCs) and scintillator counters. The arrival times and trajectories
of the incoming muons and the outgoing decay electrons are measured with this device providing effective suppression of background.
Using the TPC as an active target, we can monitor on-line the protium contamination by impurities with a sensitivity better
than 10−8. This can be done by detecting the charged products of the muon capture reaction on these impurities. It was demonstrated
that the TPC and MWPCs can operate in pure hydrogen under 10 bar pressure providing gas gain up to 10 000.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
H. Keller R. F. Kiefl Hp. Baumeler W. Kündig B. D. Patterson J. Imazato K. Nishiyama K. Nagamine T. Yamazaki R. I. Grynszpan 《Hyperfine Interactions》1986,31(1-4):461-466
The hyperfine field (B
μ
hf
) at the negative muon μ− in ferromagnetic iron was investigated by means of the zero-field μ− spin precession technique. In the temperature range 320–690 K,B
μ
hf
for μ− Fe departs from the magnetization curve of pure iron in the same way as the hyperfine field seen by a55Mn impurity in dilute MnFe measured by NMR. The hyperfine anomaly for μ− Fe relative to dilute (1.5 at.%)55Mn in iron is found to be −0.9(3)% and temperature independent over the temperature range investigated. 相似文献
9.
T. N. Mamedov V. G. Grebinnik V. A. Zhukov V. A. Kuz’min A. V. Stoikov S. G. Barsov A. L. Getalov V. P. Koptev G. V. Shcherbakov T. V. Tetereva R. A. Éramzhyan 《JETP Letters》1998,67(5):318-323
The lifetime of a negative muon in the 1S state in the isotopes 84Kr and 136Xe was measured. The values obtained, τ(84Kr)=139.2±2.9 ns and τ(136Xe)=111.0±4.6 ns, correspond to total nuclear capture rates Λc(84Kr)=6.75±0.15 μs−1 and Λ c(136Xe)=8.6±0.4 μs−1. Theoretical calculations of the rate of nuclear capture of a negative muon are performed for the Kr isotopes. The experimental
results are compared with the theoretical calculations.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 302–307 (10 March 1998) 相似文献
10.
L. N. Bogdanova V. R. Bom A. M. Demin D. L. Demin C. W. E. van Eijk S. V. Filchagin V. V. Filchenkov N. N. Grafov S. K. Grishechkin K. I. Gritsaj A. D. Konin A. V. Kuryakin S. V. Medved’ R. K. Musyaev A. I. Rudenko D. P. Tumkin Yu. I. Vinogradov A. A. Yukhimchuk S. A. Yukhimchuk V. G. Zinov S. V. Zlatoustovskii 《Journal of Experimental and Theoretical Physics》2009,108(2):216-225
The muon-catalyzed fusion (μCF) process in tritium was studied by the μCF collaboration on the muon beam of the JINR Phasotron.
The measurements were carried out with a liquid tritium target at the temperature 22 K and density approximately 1.25 of the
liquid hydrogen density (LHD). Parameters of the μCF cycle were determined: the ttμ muonic molecule formation rate λ
ttμ = 2.84(0.32) μs−1, the ttμ fusion reaction rate λ
f
= 15.6(2.0) μs−1, and the probability of muon sticking to helium ω
tt
= 13.9(1.5)%. The results agree with those obtained earlier by other groups, but better accuracy was achieved due to our unique
experimental method.
The article is published in the original. 相似文献
11.
Relative energies of muon probe sites in the chain region of RBa2Cu3O7 (RBCO) are investigated using a molecular quantum chemistry calculation for (Oμ)− embedded in a cluster of point charges to simulate local charge distributions in RBCO. Partial Cu−O chain covalency results
in a O-μ...O muon site between the chain and bridging oxygens. However, Cu-μ “hydride”-like sites are suggested by results
for nominally ionic clusters. 相似文献
12.
S. G. Karshenboim V. G. Ivanov U. D. Jentschura G. Soff 《Journal of Experimental and Theoretical Physics》1998,86(2):226-236
We examine the properties of an atomic system consisting of a muon and antimuon. Expressions are derived for the probability
of decay and the hyperfine splitting of the lower levels with allowance for the leading radiative corrections, which are of
relative order α. The results for the lifetimes and the ground-state energy are τ(13
S
1)=1.7907(8)×10−12 s, τ(11
S
0)=0.59547(33)×10−12 s, and E
hfs (1s)=4.23284(35)×107 MHz. The relative probabilities for the various decay channels are calculated; in particular, for the 1 3
S
1 level it is found that Γ (μμ→eeγ)/Γ(μμ→ee)≈15%. Finally, possible applications are discussed.
Zh. éksp. Teor. Fiz. 113, 409–431 (February 1998) 相似文献
13.
《Applied physics. B, Lasers and optics》1981,24(1):33-38
We report infrared laser emission in the region of 3 to 5 μm from sodium vapour optically pumped by a pulsed dye laser with
wavelengths ranging from 585 to 610nm. Twophoton excitation processes are believed to be responsible for the primary excitation.
Both molecular transitions (4 to 5 μm) between high lying states, and atomic transitions (52
S
1/2−42
P
3/2,1/2 at 3.41 μm) have been identified. 相似文献
14.
Bi2S3 nanotubes and de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite nanopowders were synchronously synthesized by a
one-pot self-assembly method. The powders were characterized by X-ray powder diffraction, infrared spectroscopy, and transmission
electron microscopy, respectively. Thermoelectric properties of the Bi2S3–PEDOT composite nanopowders with different Bi2S3 contents after being cold pressed into pellets were measured at room temperature. The sample with 36.1 wt% Bi2S3 has a highest power factor of 2.3 μWm−1K−2, which is higher than that of both pure PEDOT (0.445 μWm−1K−2) and Bi2S3 (1.94 μWm−1K−2). 相似文献
15.
G. M. Luke J. H. Brewer S. R. Kreitzman D. R. Noakes M. Celio R. Kadono E. J. Ansaldo 《Hyperfine Interactions》1991,64(1-4):721-727
We have studied the quantum diffusion of positive muons in pure copper over the temperature range 12 mK≤T≤150 K using weak longitudinal field μSR. Below 150 K, this technique has proved to be the most sensitive to the muon hop
rate. Our final results for the behaviour of the muon hop rate are well explained within the framework of theories for the
quantum diffusion of light interstitials in metals of Kondo, Yamada and others. In addition, the use of level-crossing resonance
has allowed us to measure the electric quadrupole interaction strength (and sign) of the copper nuclei, ωQ= −3.314(7) μS−1. These results have enabled us to show that the muon occupies the same octahedral site at all the temperatures studied, ruling
out the possibility of metastable muon sites contributing to any significant portion of the muon polarization. 相似文献
16.
V. R. Bom J. N. Bradbury J. D. Davies A. M. Demin D. L. Demin C. W. E. van Eijk V. V. Filchenkov A. N. Golubkov N. N. Grafov V. G. Grebinnik S. K. Grishechkin K. I. Gritsaj V. G. Klevtsov A. D. Konin A. A. Kukolkin S. V. Medved' V. A. Nazarov V. V. Perevozchikov A. N. Ponomarev V. Ya. Rozhkov A. I. Rudenko S. M. Sadetsky Yu. V. Smirenin N. I. Voropaev A. A. Yukhimchuk S. A. Yukhimchuk V. G. Zinov S. V. Zlatoustovskii 《Hyperfine Interactions》2001,138(1-4):213-223
Experiments on the study of the muon catalyzed fusion (μCF) process in a double D/T mixture of hydrogen isotopes in the temperature
range 300–800 K at densities 0.3–0.5 LHD are performed at the JINR phasotron. The values of the effective μCF parameters (cycling
rate λ
c
, neutron yield Y
n
, muon losses w) are obtained. Tentative dtμ-molecule formation rates on D2 and DT molecules (λ
dtμ−d
and λ
dtμ−t
) are obtained for different mixture temperatures and densities. The results obtained show that λ
dtμ−t
increases with temperature, but its value is smaller than theoretical predictions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Pogorelsky I. V. Polyanskiy M. N. Babzien M. Yakimenko V. Dover N. P. Palmer C. A. J. Najmudin Z. Schreiber J. Shkolnikov P. Dudnikova G. 《Laser Physics》2011,21(7):1288-1294
A picosecond CO2 laser was used successfully in a number of experiments exploring advanced methods of particle acceleration [1]. Proton acceleration
from gas-jet plasma exemplifies another advantage of employing the increase in laser wavelength from the optical to the mid-IR
region. Recent theoretical- and experimental-studies of ion acceleration from laser-generated plasma point to better ways
to control the ion beam’s energy when plasma approaches the critical density. Studying this regime with solid-state lasers
is problematic due to the dearth of plasma sources at the critical electron density ∼1021 cm−3, corresponding to laser wavelength λ = 1 μm. CO2 laser offers a solution. The CO2 laser’s 10 μm wavelength shifts the critical plasma density to 1019 cm−3, a value attainable with gas jets. Capitalizing on this approach, we focused a circular polarized 1-TW CO2 laser beam onto a hydrogen gas jet and observed a monoenergetic proton beam in the 1–2 MeV range. Simultaneously, we optically
probed the laser/plasma interaction region with visible light, revealing holes bored by radiation pressure, as well as quasi-stationary
soliton-like plasma formations. Our findings from 2D PIC simulations agree with experimental results and aid in their interpretation. 相似文献
18.
A. Golnik E. Albert M. Hamma E. Westhauser A. Weidinger E. Recknagel 《Hyperfine Interactions》1986,31(1-4):375-379
Transverse-field muon spin roation (μSR) is studied in Cd1−xMnxTe, x=0.4 and 0.6 mixed crystals. A large temperature dependent frequency shift and a strong relaxation of the μSR-signal
are observed. In the vicinity of the spinglass transition, the relaxation rate becomes so large that the signal disappears.
The rate of Mn spin fluctuations causing the μ+-line narrowing at high temperatures is estimated to be of the order of 109 S−1. 相似文献
19.
Machi I. Z. Connell S. H. Sellschop J. P. F. Bharuth-Ram K. 《Hyperfine Interactions》2001,136(3-8):727-730
We report on transverse field muon spin rotation measurements on a nitrogen-rich type Ia diamond, both before and after the
conversion of some of the aggregated nitrogen centres to nitrogen-vacancy complexes known as H2/H3-centres. The prompt fractions
f and the spin relaxation rates λ were determined for the diamagnetic (μd) and the paramagnetic (MuT) states in the temperature range 10–300 K. The production of the nitrogen-vacancy complexes had little effect on the parameters
of the MuT state for which f and λ remained unchanged at approximately 30% and 4 μs−1, respectively. For the μd state, on the other hand, the formation of the H2/H3-centres resulted in an increase of the prompt fraction from 10(2)% to
20(3)%, and (for the first time) the spin relaxation rate showed a non-zero value of 0.020(3) μs−1. These results show evidence of strong μd interactions with the nitrogen-vacancy complexes in diamond, and suggest a more complex structure for this state than a bare
μ+.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
20.
W. Schwarz E. H. Brandt K. -P. Döring U. Essmann K. Fürderer M. Gladisch D. Herlach G. Majer H. -J. Mundinger H. Orth A. Seeger M. Schmolz 《Hyperfine Interactions》1986,31(1-4):247-253
The diffusivityD
μ of positive muons (μ+) in the mixed state of superconducting high-purity, high-perfection niobium single crystals is investigated by measurements
of the relaxation of the transverse muon spin polarization (μ+SR). The method makes use of the strong magnetic field gradients existing in the mixed state of Type-II superconductors and
monitorsD
μ through the variation of the magnetic field felt by the μ+ during their diffusion through the crystals. For μ+ near the centres of the flux lines inNb it givesD
μ(4.6 K)=(8±2)·10−11m2S−1. The positive temperature coefficient ofD
μ indicates that at liquid-helium temperatures the diffusivity of μ+ inNb is mainly due to phonon-assisted tunnelling processes. 相似文献