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.
We report the first result from a dark photon dark matter search in the mass range from \({78.62}\) to \(83.95~\mathrm{\mu eV}/c^2\) with a dielectric haloscope prototype for MADMAX (Magnetized Disc ...and Mirror Axion eXperiment). Putative dark photons would convert to observable photons within a stack consisting of three sapphire disks and a mirror. The emitted power of this system is received by an antenna and successively digitized using a low-noise receiver. No dark photon signal has been observed. Assuming unpolarized dark photon dark matter with a local density of \(\rho_{\chi}=0.3~\mathrm{GeV/cm^3}\) we exclude a dark photon to photon mixing parameter \(\chi > 3.0 \times 10^{-12}\) over the full mass range and \(\chi > 1.2 \times 10^{-13}\) at a mass of \(80.57~\mathrm{\mu eV}/c^2\) with a 95\% confidence level. This is the first physics result from a MADMAX prototype and exceeds previous constraints on \(\chi\) in this mass range by up to almost three orders of magnitude.
MADMAX, a future experiment to search for axion dark matter, is based on a novel detection concept called the dielectric haloscope. It consists of a booster composed of several dielectric disks ...positioned with \(\mu\)m precision. A prototype composed of one movable disk was built to demonstrate the mechanical feasibility of such a booster in the challenging environment of the experiment: high magnetic field to convert the axions into photons and cryogenic temperature to reduce the thermal noise. It was tested both inside a strong magnetic field up to 1.6 T and at cryogenic temperatures down to 35K. The measurements of the velocity and positioning accuracy of the disk are shown and are found to match the MADMAX requirements.
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 (Cornell University),
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.
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