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A proposal for laser cooling antihydrogen atoms

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 Added by Makoto C. Fujiwara
 Publication date 2012
  fields Physics
and research's language is English
 Authors P. H. Donnan




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We present a scheme for laser cooling applicable for an extremely dilute sample of magnetically trapped antihydrogen atoms($bar{H}$). Exploiting and controlling the dynamical coupling between the $bar{H}$s motional degrees of freedom in a magnetic trap, three-dimensional cooling can be achieved from Doppler cooling on one dimension using the $1s_{1/2}-2p_{3/2}$ transition. The lack of three-dimensional access to the trapped $bar{H}$ and the nearly separable nature of the trapping potential leads to difficulties in cooling. Using realistic models for the spatial variation of the magnetic fields, we find that it should be possible to cool the $bar{H}$s to $sim 20$ mK even with these constraints.



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Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilated. The antiproton annihilations produce easily detected signals; we used these signals to prove that we trapped antihydrogen. However, our technique could be confounded by mirror-trapped antiprotons, which would produce seemingly-identical annihilation signals upon hitting the trap wall. In this paper, we discuss possible sources of mirror-trapped antiprotons and show that antihydrogen and antiprotons can be readily distinguished, often with the aid of applied electric fields, by analyzing the annihilation locations and times. We further discuss the general properties of antiproton and antihydrogen trajectories in this magnetic geometry, and reconstruct the antihydrogen energy distribution from the measured annihilation time history.
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