CONDOR – A heterodyne receiver at 1.25-1.5 THz Wiedner, M. C.; Wieching, G.; Bielau, F. ...
Proceedings of the International Astronomical Union,
08/2006, Letnik:
2, Številka:
S237
Journal Article
Recenzirano
Odprti dostop
The CON+Deuterium Observations Receiver (CONDOR) is a heterodyne receiver that operates between 1250–1530 GHz. Its primary goal is to observe star-forming regions in CO, N+, and H2D+ emission.
CONDOR, the CO, N+, Deuterium Observations Receiver, is designed to make velocity-resolved observations of the CO, NII, and p-H2D+ lines in the 1.4 THz (200-240μm) atmospheric windows. CONDOR's first ...light observations were made with the APEX telescope in November 2005. The CONDOR beam on APEX (at ν = 1.5 THz) was expected to consist of a 4.3″ main beam and a 73″ error beam; this beam structure was verified from scans of Mars. The pointing accuracy, also determined from Mars scans, was better than 7″. The average atmospheric transmission during our Orion observations (elev~57°) was 19 ± 4% along the line-of-sight. A forward efficiency of Feff = 0.8 was determined from sky dips, and observations of the Moon and Mars were used to couple the CONDOR beam to sources of different sizes (ηc = 0.40 and ~0.10, respectively). For more information, see Wiedner et al. 2006.
The reciprocity approach is a powerful method to determine the expected signal power of axion haloscopes in a model-independent way. Especially for open and broadband setups like the MADMAX ...dielectric haloscope the sensitivity to the axion field is difficult to calibrate since they do not allow discrete eigenmode analysis and are optically too large to fully simulate. The central idea of the reciprocity approach is to measure a reflection-induced test field in the setup instead of trying to simulate the axion-induced field. In this article, the reciprocity approach is used to determine the expected signal power of a dish antenna and a minimal dielectric haloscope directly from measurements. The results match expectations from simulation but also include important systematic effects that are too difficult to simulate. In particular, the effect of antenna standing waves and higher order mode perturbations can be quantified for the first time in a dielectric haloscope.
VLBI at APEX: First Fringes Roy, Alan; Wagner, Jan; Wunderlich, Michael ...
1th European VLBI Network Symposium and Users Meeting, EVN Symposium 2012, Bordeaux, France,
2012, Letnik:
2012-October
Conference Proceeding
Superluminous supernovae (SLSNe) and long gamma ray bursts (LGRBs) have been proposed as progenitors of repeating Fast Radio Bursts (FRBs). In this scenario, bursts originate from the interaction ...between a young magnetar and its surrounding supernova remnant (SNR). Such a model could explain the repeating, apparently non-Poissonian nature of FRB121102, which appears to display quiescent and active phases. This bursting behaviour is better explained with a Weibull distribution, which includes parametrisation for clustering. We observed 10 SLSNe/LGRBs for 63 hours, looking for repeating FRBs with the Effelsberg-100 m radio telescope, but have not detected any bursts. We scale the burst rate of FRB121102 to an FRB121102-like source inhabiting each of our observed targets, and compare this rate to our upper burst rate limit on a source by source basis. By adopting a fiducial beaming fraction of 0.6, we obtain 99.99\% and 83.4\% probabilities that at least one, and at least half of our observed sources are beamed towards us respectively. One of our SLSN targets, PTF10hgi, is coincident with a persistent radio source, making it a possible analogue to FRB121102. We performed further observations on this source using the Effelsberg-100~m and Parkes-64~m radio telescopes. Assuming that PTF10hgi contains an FRB121102-like source, the probabilities of not detecting any bursts from a Weibull distribution during our observations are 14\% and 16\% for Effelsberg and Parkes respectively. We conclude by showing that a survey of many short observations increases burst detection probability for a source with Weibull distributed bursting activity.
We present 3D calculations for dielectric haloscopes such as the currently envisioned MADMAX experiment. For ideal systems with perfectly flat, parallel and isotropic dielectric disks of finite ...diameter, we find that a geometrical form factor reduces the emitted power by up to \(30\,\%\) compared to earlier 1D calculations. We derive the emitted beam shape, which is important for antenna design. We show that realistic dark matter axion velocities of \(10^{-3} c\) and inhomogeneities of the external magnetic field at the scale of \(10\,\%\) have negligible impact on the sensitivity of MADMAX. We investigate design requirements for which the emitted power changes by less than \(20\,\%\) for a benchmark boost factor with a bandwidth of \(50\,{\rm MHz}\) at \(22\,{\rm GHz}\), corresponding to an axion mass of \(90\,\mu{\rm eV}\). We find that the maximum allowed disk tilt is \(100\,\mu{\rm m}\) divided by the disk diameter, the required disk planarity is \(20\,\mu{\rm m}\) (min-to-max) or better, and the maximum allowed surface roughness is \(100\,\mu{\rm m}\) (min-to-max). We show how using tiled dielectric disks glued together from multiple smaller patches can affect the beam shape and antenna coupling.
MADMAX Status Report Beurthey, S; Böhmer, N; Brun, P ...
arXiv.org,
10/2020
Paper, Journal Article
Odprti dostop
In this report we present the status of the MAgnetized Disk and Mirror Axion eXperiment (MADMAX), the first dielectric haloscope for the direct search of dark matter axions in the mass range of 40 to ...400 \(\mu\)eV. MADMAX will consist of several parallel dielectric disks, which are placed in a strong magnetic field and with adjustable separations. This setting is expected to allow for an observable emission of axion induced electromagnetic waves at a frequency between 10 and 100 GHz corresponding to the axion mass. The present document orignated from a status report to the DESY PRC in 2019.
During February 2016, CSIRO Astronomy and Space Science and the Max-Planck-Institute for Radio Astronomy installed, commissioned and carried out science observations with a phased array feed (PAF) ...receiver system on the 64m diameter Parkes radio telescope. Here we demonstrate that the PAF can be used for pulsar observations and we highlight some unique capabilities. We demonstrate that the pulse profiles obtained using the PAF can be calibrated and that multiple pulsars can be simultaneously observed. Significantly, we find that an intrinsic polarisation leakage of -31dB can be achieved with a PAF beam offset from the centre of the field of view. We discuss the possibilities for using a PAF for future pulsar observations and for searching for fast radio bursts with the Parkes and Effelsberg telescopes.
Eur. Phys. J. C 79 (2019) no.3, 186 The axion emerges in extensions of the Standard Model that explain the
absence of CP violation in the strong interactions. Simultaneously, it can
provide naturally ...the cold dark matter in our universe. Several searches for
axions and axion-like particles (ALPs) have constrained the corresponding
parameter space over the last decades but no unambiguous hints of their
existence have been found. The axion mass range below 1 meV remains highly
attractive and a well motivated region for dark matter axions. In this White
Paper we present a description of a new experiment based on the concept of a
dielectric haloscope for the direct search of dark matter axions in the mass
range of 40 to 400 $\mu$eV. This MAgnetized Disk and Mirror Axion eXperiment
(MADMAX) will consist of several parallel dielectric disks, which are placed in
a strong magnetic field and with adjustable separations. This setting is
expected to allow for an observable emission of axion induced electromagnetic
waves at a frequency between 10 to 100 GHz corresponding to the axion mass.
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