Search results for "Quantum efficiency"
showing 10 items of 92 documents
Breakthrough in the lifetime of microchannel plate photomultipliers
2015
Abstract Cherenkov detectors using the DIRC (Detection of Internally Reflected Cherenkov Light) principle are foreseen for particle identification in the P ¯ ANDA experiment at FAIR. Promising sensors for the detection of the Cherenkov light are the so-called micro-channel plate (MCP) photomultipliers (PMT). They have an excellent time resolution, can be operated at high gain for single photon detection and have a high resistivity against magnetic fields. The disadvantage of these devices was their limited lifetime, due to damage by feedback ions on the photocathode. The lifetime of various types of MCP-PMTs from different manufactures has been tested under conditions similar to that in the…
Recent developments with microchannel-plate PMTs
2017
Abstract Microchannel-plate (MCP) PMTs are the favored photon sensors for the DIRC detectors of the PANDA experiment at FAIR. Until recently the main drawback of MCP-PMTs were serious aging effects which led to a limited lifetime due to a rapidly decreasing quantum efficiency (QE) of the photo cathode (PC) as the integrated anode charge (IAC) increased. In the latest models of PHOTONIS and Hamamatsu an innovative atomic layer deposition (ALD) technique is applied to overcome these limitations. During the last five years comprehensive aging tests with ALD coated MCP-PMTs were performed and the results were compared to tubes treated with other techniques. The QE in dependence of the IAC was m…
Tremendously increased lifetime of MCP-PMTs
2017
Abstract Microchannel plate (MCP) PMTs are very attractive photon sensors for low light level applications in strong magnetic fields. However, until recently the main drawback of MCP-PMTs was their aging behavior which manifests itself in a limited lifetime due to a rapidly decreasing quantum efficiency (QE) of the photo cathode (PC) as the integrated anode charge (IAC) increases. In the latest models of PHOTONIS, Hamamatsu, and BINP novel techniques are applied to avoid these aging effects which are supposed to be mainly caused by feedback ion impinging on the PC and damaging it. For more than four years we are running a long-term aging test with new lifetime-enhanced MCP-PMT models by sim…
Lifetime of MCP-PMTs and other performance features
2018
The ANDA experiment at FAIR will use DIRC detectors for the separation of hadrons. The compactness of the ANDA detector requires the image planes of these detectors to be placed inside the magnetic field of the solenoid. Due to this and other boundary conditions MCP-PMTs were identified as the only suitable photon sensors. Until recently the major obstacle for an application of MCP-PMTs in high rate experiments like ANDA were serious aging problems which led to damage at the photo-cathode and a fast declining quantum efficiency as the integrated anode charge (IAC) increased. With new countermeasures against the aging, in particular due to the application of an atomic layer deposition (ALD) …
Effect of quantum efficiency on the performance of multijunction tandem cells
2015
New insight into the potential of practical solar cells can be given through alternative modeling approaches like Monte Carlo simulations. In the present work, the performance of three stacks of cells connected in series was examined at different levels of internal quantum efficiency. Incident photons, generated by employing the ASTM G173-03 and E490-00a data sets, are accounted for individually as they interact with the stack of cells. The values of the different bandgaps were chosen from a paper by K. Tanabe (2009), and the performance was studied based on photon dynamics.
Device-independent quantum reading and noise-assisted quantum transmitters
2014
In quantum reading, a quantum state of light (transmitter) is applied to read classical information. In the presence of noise or for sufficiently weak signals, quantum reading can outperform classical reading by enhanced state distinguishability. Here we show that the enhanced quantum efficiency depends on the presence in the transmitter of a particular type of quantum correlations, the discord of response. Different encodings and transmitters give rise to different levels of efficiency. Considering noisy quantum probes we show that squeezed thermal transmitters with non-symmetrically distributed noise among the field modes yield a higher quantum efficiency compared to coherent thermal quan…
Trapping and sympathetic cooling of single thorium ions for spectroscopy
2018
Precision optical spectroscopy of exotic ions reveals accurate information about nuclear properties such as charge radii and magnetic and quadrupole moments. Thorium ions exhibit unique nuclear properties with high relevance for testing symmetries of nature. We report loading and trapping of single $^{232}$Th$^+$ ions in a linear Paul trap, embedded into and sympathetically cooled by small crystals of trapped $^{40}$Ca$^+$ ions. Trapped Th ions are identified in a non-destructive manner from the voids in the laser-induced Ca fluorescence pattern emitted by the crystal, and alternatively, by means of a time-of-flight signal when extracting ions from the Paul trap and steering them into an ex…
High-precision x-ray spectroscopy of highly charged ions with microcalorimeters
2013
The precise determination of the energy of the Lyman α1 and α2 lines in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. To improve the experimental precision, the new detector concept of microcalorimeters is now exploited for such measurements. Such detectors consist of compensated-doped silicon thermistors and Pb or Sn absorbers to obtain high quantum efficiency in the energy range of 40–70 keV, where the Doppler-shifted Lyman lines are located. For the first time, a microcalorimeter was applied in an experiment to precisely determine the transition energy of the Lyman lines of lead ions at the experimental storage ring at GSI. T…
Source of Polarized Electrons for MAMI B
1991
A source of polarized electrons has been set up in order to inject polarized electrons into the 855 MeV c.w. electron accelerator MAMI B at the Mainz nuclear physics institute. It is based on photoemission of the 3/5 semiconductor GaAsP and will provide a d.c. current of 100 µA with a beam emittance of 1π mm mrad, and a polarization of about 40%.
Light trapping by plasmonic nanoparticles
2020
Abstract Metallic nanoparticles sustaining localized surface plasmon resonances are of great interest for enhancing light trapping in thin film photovoltaics. In this chapter, we explore the correlation between the structural and optical properties of self-assembled silver nanostructures fabricated by a solid-state dewetting process on various substrates relevant for silicon photovoltaics and later integrated into plasmonic back reflectors. Our study allows us to optimize the performance of nanostructures by identifying the fabrication conditions in which desirable circular and uniformly spaced nanoparticles are obtained. Second, we introduce a novel optoelectronic spectroscopic method that…