Fast Light Sensors in Physics Experiments (Overview)

• Razmik Mirzoyan (MPP)

Room: New seminar room, downstairs Most experiments in physics are using some type of light detector. The Astro-particle physics group in Max-Planck-Institute for Physics (MPIP) has long traditions in light detector developments, several novel sensors were initiated by us. We have developed very high Quantum Efficiency (QE) Hybrid Photo Detectors (HPD) with GaAsP photocathode and Avalanche Photo Diodes (APD) matrixes in cooperation with industrial partners in the past. Also, in recent years we co-developed and strongly improved classical Photo Multiplier Tubes (PMT). Since mid 1960’s the QE of classical PMTs was stagnating on the level of ~25 % and the photo electron (ph.e.) Collection Efficiency (CE) was on the level of ~80 %. In recent ~10 years we initiated up to 85 % improvement of the Photon Detection Efficiency (PDE = QE x ph.e. CE) of bialkali type PMTs. The MAGIC project was the first to profit from these developments, the new PMTs allowed us operating the telescopes above a low energy threshold of 50 GeV. The most recent PMTs can provide an average peak QE of ~42 % and a ph.e. collection efficiency of 95-98 %. Along with vacuum tube technology in recent ~14 years we are closely cooperating with researchers, who were pioneering the emergence and developments of SiPM. Our cooperation, also with industrial partners, showed fruitful results, top-class sensors became available, setting new standards in Photon Detection Efficiency and cross-talk. In his presentation Razmik would like to go over the basics of light detection as well as over the development of different type sensors, focusing on super-bialkali PMTs and on SiPMs.

Germanium Detectors (Overview)

• Iris Abt (MPP)

Room: New seminar room, downstairs An overview of the physics and technology of germanium detectors is given. Germanium is compared to silicon. Different germanium detector types are introduced and there features are given to motivate the choice of technology for different applications.

From gated to continuous readout: an upgrade of the ALICE TPC (Overview)

• Piotr Gasik (TUM)

Room: New seminar room, downstairs A large Time Projection Chamber (TPC) is the main device for tracking and charged particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2019/20, the LHC will deliver Pb beams colliding at an interaction rate of about 50 kHz, which is about a factor of 100 above the present read-out rate of the TPC. This will result in a significant improvement on the sensitivity of rare probes that are considered key observables to characterise the QCD matter created in such collisions. In order to make full use of this luminosity, a major upgrade of the TPC is required. Since the TPC drift time of 100 μs is 5 times longer than the average time between interactions, the presently employed gating of the TPC wire chambers must be abandoned and continuously operated readout detectors using GEMs will be implemented. To fulfil the challenging requirements of the upcoming upgrade, a novel configuration of GEM detectors has been developed. It allows to maintain excellent particle identification and efficient ion trapping by stacking four GEM foils operated under specific field configuration. Results of an extensive R&D program concerning ion backflow suppression, dE/dx resolution and stability against discharges will be presented. The status of the upgrade of the online calibration and data reduction system, as well as the development of a new readout electronics will be reported. We will also discuss the detector production phase, which is just starting.

High-precision magnetic field detection with spin polarized atomic vapors.

• Michael Sturm (TUM)

Room: New seminar room, downstairs Known and widely used concepts for high precision magnetic field detection are usually based on the concepts of fluxgates or SQUIDS which can be magnetic and/or require cry-temperatures. Another approach at room temperature and with achievable sensitivities down to the femto-Tesla level is the use of spin polarized vapor samples. This talk will give an overview of the underlying quantum mechanical concepts and will show some application examples, also carried out at the Universe Cluster.

A novel Axion microwave experiment

• Olaf Reimann (MPP)

Room: New seminar room, downstairs Axions are hypothetical low-mass bosons which are predicted to exist by the Peccei-Quinn mechanism that can explain the absence of CP-violating effects in quantum chromodynamics (QCD). They could also provide the cold dark matter of the universe and as such are among the few particle candidates that solve simultaneously two major problems of nature. A novel concept based on the idea of axion photon conversion at the transition between two media in a static magnetic field will be presented. The hypothetical (cold) dark matter axion field is strongly coherent. A coupled cavity structure made out of layers with alternating dielectric constants is used to sum up the in-phase component of the generated photons. The predicted signal boost is large enough for an unambiguous detection of the microwave photons with state of the art radiometer technology. The experimental idea, the proposed design for an experiment in the 40µeV to 400µeV axion mass range, and some of the boundary conditions for the photon detection will be discussed in this talk.

Cryogenic detectors for rare event searches (Overview)

• Federica Petricca (MPP)

Room: New seminar room, downstairs Cryogenic detectors were introduced in rare events physics in the 1980s. During the last 30 years these detectors became crucial for a large number of neutrino physics and dark matter search applications. A cryogenic calorimeter composed of an absorber crystal and a temperature sensor, measures the energy of an impinging particle converted into phonons. This provides an energy collection mechanism that is more efficient than those used in other standard detectors, which translates into a much better energy resolution. This, together with the possibility of choosing a wide range of materials for the absorber crystal, make cryogenic calorimeters the ideal candidates for a large number of rare events applications in which the slowness of the response is not important for the measurement. The possibility of using cryogenic calorimeters with double read out (heat+light or heat+ionization) in scintillating or semiconducting crystals also allows extremely powerful radiation discrimination techniques. Recent upgrades are pushing the technique to a new era in which the large masses (~1000 channels for a tonne scale detectors) and extremely low thresholds (~0.1 keV) are opening the way to unexplored regions for dark matter and double beta decays searches.