Antihydrogen detector and simulations
Regarding the development of a new antihydrogen detector we developed an analysis framework to test various detector configurations on efficiency in finding real annihilation events and in suppressing the false identification of cosmic particles as antihydrogen annihilation. Distinguishing these two types of events is of great importance as the real event rate is lower than the cosmic rate and due to electromagnetic showers produced by the cosmic rays sophisticated methods for cosmic suppression have been developed. To distinguish these events the detector tracks are separated using a Hough analysis, after that the tracks are fitted with straight lines and statistically tested to their significance, this allows to define timing and multiplicity cuts that allow, together with information on energy deposit, to eliminate most false events while preserving a good efficiency for detecting real antihydrogen annihilations.
Based on the simulation results first ideas for a new antihydrogen detector were finalised and the construction of this detector is currently ongoing effort. On the hardware side new pre-amplifiers for the silicon photomultiplier have been developed and tested, a detailed description of this new devices that allow fine grain control of the amplification gain and self triggering with an onboard discriminator are presented in the advanced instrumentation chapter of this document.
During the year 2013 vast improvements on the simulation code for detector and beamline simulations have been achieved. Regarding the simulation of the microwave cavity we managed to implement the use of measured and simulated fieldmaps inside of the cavity volume together with an important improvement in calculation speed and numerical accuracy. For the first time we managed to include the simulation of higher excited quantum states for hydrogen inside the Geant 4 particle physics simulation toolkit. This type of novel simulations also includes the deexcitation of the higher excited states in vacuum as well as in weak and strong magnetic and electric fields, therefore allowing us to produce an accurate tracking simulation for newly produced antihydrogen atoms depending on their initial quantum state distribution. Also during 2013 an evaluation of the antiproton decay processes in Geant 4 has been started and is now under active work. First preliminary results show major differences within the annihilation codes already implemented in Geant 4 (FRITOF and CHIPS) and also in comparison to available annihilation data from crystal ball experiments. Additional effort was invested to develop a model for calculating Majorana transitions of particles traversing a magnetic field gradient. First preliminary simulations with the unfinished model indicate major influences for the polarisation of the antihydrogen atoms due to Majorana transitions. The work on this model is still ongoing.
Regarding the development of a new antihydrogen detector we developed an analysis framework to test various detector configurations on efficiency in finding real annihilation events and in suppressing the false identification of cosmic particles as antihydrogen annihilation. Distinguishing these two types of events is of great importance as the real event rate is lower than the cosmic rate and due to electromagnetic showers produced by the cosmic rays sophisticated methods for cosmic suppression have been developed. To distinguish these events the detector tracks are separated using a Hough analysis, after that the tracks are fitted with straight lines and statistically tested to their significance, this allows to define timing and multiplicity cuts that allow, together with information on energy deposit, to eliminate most false events while preserving a good efficiency for detecting real antihydrogen annihilations.
Based on the simulation results first ideas for a new antihydrogen detector were finalised and the construction of this detector is currently ongoing effort. On the hardware side new pre-amplifiers for the silicon photomultiplier have been developed and tested, a detailed description of this new devices that allow fine grain control of the amplification gain and self triggering with an onboard discriminator are presented in the advanced instrumentation chapter of this document.