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Mühlbauer, M.; Daniel, H.; Hartmann, F. J.; Hauser, Peter C.; Kottmann, F.; Petitjean, C.; Schott, W.; Taqqu, D.; Wojciechowski, Piotr

doi:10.1023/a:1012624501134

Cited by 35 publications

(24 citation statements)

References 14 publications

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“…They then crossed a stack of seven thin carbon foils (each with an areal density of 5 µg/cm 2 and 2 cm diameter) where a few electrons were released. A high voltage applied to the stack (∆U = 1800 V between successive foils) accelerated these electrons, and frictional cooling [22] enhanced the muon stop rate. After traversing the gas target, the electrons were detected in a microchannel plate (MCP).…”

Section: Smentioning

confidence: 99%

Observation of Long-Lived Muonic Hydrogen in the2SState

Pohl¹,

Daniel²,

Hartmann³

et al. 2006

Phys. Rev. Lett.

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The kinetic energy distribution of ground state muonic hydrogen atoms µp(1S) is determined from time-of-flight spectra measured at 4, 16, and 64 hPa H2 room-temperature gas. A 0.9 keVcomponent is discovered and attributed to radiationless deexcitation of long-lived µp(2S) atoms in collisions with H2 molecules. The analysis reveals a relative population of about 1 %, and a pressuredependent lifetime (e.g. 30.4 +21.4 −9.7 ns at 64 hPa) of the long-lived µp(2S) population, equivalent to a 2S-quench rate in µp(2S)+H2 collisions of 4.4 +2.1 −1.8 × 10 11 s −1 at liquid hydrogen density.PACS numbers: 36.10. Dr, 34.20.Gj A measurement of the Lamb shift in muonic hydrogen, i.e. the energy difference of 0.2 eV between the 2P -and 2S-states of µ − p atoms [1,2,3], is in progress at the Paul Scherrer Institute (PSI), Switzerland [4]. Vacuum polarization shifts the 2S-levels by 0.2 eV below the 2P -levels; fine and hyperfine splittings of the n = 2 levels are much smaller. The finite size effect is 2 % of the Lamb shift.The µp Lamb shift experiment is expected to give a precise value for the root-mean-square charge radius of the proton [5]. Together with recent advances in H-atom spectroscopy [6,7], this leads to a better determination of the Rydberg constant, and to a test of bound-state quantum electrodynamics on a new level of precision [8].The most important prerequisite for such an experiment, the availability of sufficiently long-lived µp(2S) atoms, has so far not been experimentally established. When muons are stopped in H 2 gas, µp atoms are formed at high n-levels and then deexcite predominantly to the ground state ("muonic cascade"). A fraction ε 2S of a few percent reaches the metastable 2S state whose lifetime is, in absence of collisions, essentially given by the muon lifetime of 2.2 µs.In a gas, there is collisional 2S-quenching, with very different rates depending on the µp kinetic energy being above or below the 2S-2P threshold (≈ 0.3 eV in the lab frame) [9]. Most µp(2S) atoms are formed at energies above this threshold [10], where collisional 2S → 2P Stark transitions (followed by 2P → 1S radiative deexcitation) lead to rather fast 2S-depletion. This is the "short-lived" 2S-component with a predicted lifetime [11] τ short 2S∼ 100 ns/p H2 [hPa]. There is, however, a competition between such Stark transitions and deceleration [9]. A fraction of the µp(2S) atoms should therefore survive the process of slowing down below 0.3 eV, where transitions to the 2P state are energetically forbidden. These µp(2S) atoms form the "long-lived" 2S-component, with a lifetime τ long 2S and a population ε long 2S (per µp atom).The 2S-population ε 2S is well determined from the measured µp X-ray yields [12,13,14]. ε long 2S can be derived from the measured 1S kinetic energy distributions [15] by using calculated elastic and inelastic µp(2S) cross sections [9]. At 16 hPa, for example, ε 2S = (4.40 ± 0.17) % and ε long 2S = (1.16 ± 0.12) %. Calculations of the radiative quenching process during collisions [16,17,18] predicted v...

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Section: Smentioning

confidence: 99%

Observation of Long-Lived Muonic Hydrogen in the2SState

Pohl¹,

Daniel²,

Hartmann³

et al. 2006

Phys. Rev. Lett.

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“…Frictional cooling has been proposed and studied theoretically [7,8] and experimentally [9,10] in the context of muons. For antiprotons, frictional cooling might be used to compensate for the large mismatch that exists between the average kinetic energy of the antiproton beam exciting the AD and the kinetic energy of particles that typically can be trapped-several MeV versus a few keV.…”

Section: Overview Of Frictional Cooling For Antiprotonsmentioning

confidence: 99%

Enhancing trappable antiproton populations through deceleration and frictional cooling

Zolotorev

Sessler

Penn

et al. 2012

Phys. Rev. ST Accel. Beams

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CERN currently delivers antiprotons for trapping experiments with the antiproton decelerator (AD), which slows the antiprotons down to about 5 MeV. This energy is currently too high for direct trapping, and thick foils are used to slow down the beam to energies which can be trapped. To allow further deceleration to $100 keV, CERN is initiating the construction of ELENA, consisting of a ring which will combine rf deceleration and electron cooling capabilities. We describe a simple frictional cooling scheme that can serve to provide significantly improved trapping efficiency, either directly from the AD or first using a standard deceleration mechanism (induction linac or rf quadrupole). This scheme could be implemented in a short time. The device itself is short in length, uses accessible voltages, and at reasonable cost could serve in the interim before ELENA becomes operational, or possibly in lieu of ELENA for some experiments. Simple theory and simulations provide a preliminary assessment of the concept and its strengths and limitations, and highlight important areas for experimental studies, in particular to pin down the level of multiple scattering for low-energy antiprotons. We show that the frictional cooling scheme can provide a similar energy spectrum to that of ELENA, but with higher transverse emittances.

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“…Frictional cooling is the bringing of charged particles to an equilibrium energy by the balancing of energy loss to a material with energy gain from an electric field [6]. Figure 1 shows the stopping power, T eq is the equilibrium energy.…”

Section: Frictional Coolingmentioning

confidence: 99%

“…One way to achieve this is using a series of thin foils with an electric field present between them, as was used by a previous experiment at PSI [6]. Although the average density is low, the density in the foils is large, so the lower-energy particles have a significant probability to stop and decay.…”

Section: Frictional Coolingmentioning

confidence: 99%

Low-energy μ+ via frictional cooling

Bao

Caldwell

Greenwald

et al. 2010

Nuclear Instruments and Methods in Physics Research Section A:

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Low-energy muon beams are useful for a range of physics experiments. We consider the production of low-energy µ + beams with small energy spreads using frictional cooling. As the input beam, we take a surface muon source such as that at the Paul Scherrer Institute. Simulations show that the efficiency of low energy µ + production can potentially be raised to 1%, which is significantly higher than that of current schemes.

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Cited by 35 publications

References 14 publications

Observation of Long-Lived Muonic Hydrogen in the2SState

Observation of Long-Lived Muonic Hydrogen in the2SState

Enhancing trappable antiproton populations through deceleration and frictional cooling

Low-energy μ+ via frictional cooling

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