Some random thoughts on dish antenna experiments Marek Kowalski Universität Bonn

10-6 Hz 10-8 Hz

Sensitivity With increasing A and constant angular reslution, Horns et al., JCAP 2013 With increasing A and constant angular reslution, the dimensions of the image, as well as the  detector noise increases linearly.

Example for a 20 cm f/4 dish @ 500nm PSF width (diffraction limited): 1.2 x f/8 x λ = 5 μm Focus spot size: 4 x (f/8)2 x λ = 128 μm Alligment light source at center of dish Allignement should not to be a problem Possible sensors: CCD, TE sensor or PMT?

Wide Field Camera 3 on the Hubble Space Telescope High quality, substrate-removed 1.7 μm HgCdTe arrays delivered to Goddard Space Flight Center Dark current (145K) = 0.02 e-/pix/sec Readout noise = 25 e- (single CDS)

Beletic

Photomultipliers Disadvantages: Limited wavelength range Advantages: Large size! Noise ~1 Hz per cm2 area (cooled to <-10oC) Possible variation: Light concentration through wavelength shifting lightguides, readout by small PMTs. Noise reduction by factor ~100 possible (development done in Bonn) Similar technique as in solar luminiscent concentration

Photomultipliers Disadvantages: Limited wavelength range Advantages: Large size! Noise ~1 Hz per cm2 area (cooled to <-10oC)

Transition Edge sensors Pros: Single photon sensitivity Limited energy information per photon Low noise (10-3 Hz or lower?) Disadvantages Limited Size Complicated operation

Figure of merit Example 1: Example 2: Adish = 0.2 m2 (0.5 m diam) Adetector = 200 μm2 Ndark = 500 Hz (using CCD) T=107 s FoM = 0.0071 Example 2: Adish = 7 m2 (3 m diameter) Adetector = 1 cm2 (~1 arcmin FoV) Ndark = 1 Hz (using PMT) T=107 s FoM = 0.0067