Beam Optics Simulations and Thermal Shielding for the AEGIS Antihydrogen Experiment

The AEGIS (Antimatter Experiments: Gravity, Interferometry, Spectroscopy) experi-ment at CERN’s Antiproton Decelerator aims at a direct measurement of the gravita-tional interaction of antihydrogen. This would be a novel test of the current theory ofgravity, General Relativity. It may also provide new insights in cosmological questionslike Dark Matter, Dark Energy and the matter-antimatter asymmetry.Via a free fall experiment on a beam of antihydrogen atoms the gravitational accelerationwill be determined with a precision of 1 %. The temperature of the antiprotons usedfor antihydrogen formation must be about 0.1 K to allow this precision. A cryogenicenvironment is mandatory to avoid heating of the trapped antiprotons through blackbody radiation. Along the antihydrogen beam line the temperature of the apparatuswill be significantly higher and black body radiation would reach the trap. To avoid thisa cryogenic shutter is foreseen that separates the trap and the beam line as long as noantihydrogen atoms leave the trap. In this thesis the design and characterization of aprototype for such a device are presented.Another topic of this thesis deals with the second goal of AEGIS. Aside from the gravitymeasurements the antihydrogen beam will be used for ground state hyperfine spec-troscopy. This intends to probe CPT symmetry with unprecedented precision.The Standard Model of particle physics is invariant with respect to replacing matter byantimatter (C) and simultaneous inversion of space (P) and time (T) coordinates. ThisCPT symmetry was tested in numerous precision experiments. In the present formal-ism of particle physics it was found to be a consequence of fundamental concepts likee.g. causality and Lorentz invariance. Hence a violation of CPT symmetry would bea first glimpse at new physics (e.g. string theory) that is based on radically differentprinciples. It was pointed that the ground state hyperfine splitting in antihydrogen maydeviate from the known splitting in hydrogen as a result of CPT violation.For these measurements the AEGIS antihydrogen beam will pass through a first sex-tupole magnet that either focuses or defocuses the atoms according to the spin orienta-tion of their positron. Only the ones that are focused reach a microwave cavity that caninduce a spin flip and therein a transition from one hyperfine state to another. This tran-sition is only induced if the microwave in the cavity is tuned to the transition frequency.After the cavity the beam passes through another magnetic sextupole field that focusesthe atoms that have not undergone a transition towards a detector. By measuring thecount rate in dependence of the microwave frequency the transition frequency can bedetermined.The task for this part of the thesis was to perform beam optics simulations of theantihydrogen beam in magnetic sextupole fields to find the ideal arrangement for thespectroscopy beam line. In addition it was studied whether the focusing properties of asextupole magnet could be used to enhance the count rate in the gravity experiment.