intensity interferometry at southern connecticut state university
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Intensity Interferometry at Southern Connecticut State University. WORKING TOWARD THE INTERFEROMETER IN A SUITCASE Elliott Horch, Southern Connecticut State University. Collaborators. SCSU Undergraduates: Matthew Camarata , now at Boston University A.J. Guerra - PowerPoint PPT PresentationTRANSCRIPT
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Intensity Interferometry at Southern Connecticut State UniversityWORKING TOWARD THE INTERFEROMETERIN A SUITCASE
Elliott Horch, Southern Connecticut State University
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05.13.2014 HBT Workshop @ OCA
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CollaboratorsSCSU Undergraduates:
Matthew Camarata, now at Boston UniversityA.J. Guerra
Gerard van Belle (Lowell Observatory)Joe Ritter (University of Hawaii)Russ Genet (CalPoly)Bruce Holenstein (Gravic, Inc.)
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Origins of Stellar Interferometry1920’s: Albert Michelson
builds first stellar interferometer by using two sub-apertures of Mt. Wilson 100-inch telescope.
Measured several stellar diameters.
Tried to extend the baseline, but mechanical issues prevented progress.
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How Optical Interferometry is Done Today…
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Light is made to interfere prior to detection. (Michelson Interferometry).
Higher signal-to-noise, but expensive. Certainly NOT portable.
~300 m baselines. Much Larger? Hmmm…
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Intensity Interferomety There is a weak correlation in the
arrival times of photons when viewed by two different detectors. “Wave Noise.”
Related to beat frequencies, in the most extreme case.
This effect was used in astronomy in the 1970’s to measure diameters of bright stars.
One configuration of the two telescopes yields one Fourier component of the image
(well, |g|2). But, huge collectors were needed
to detect this weak signal on the photomultiplier tubes of the day.
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Sydney University Stellar Interferometer
Photo: J. Davis
P.S.: Only two stations, So no imaging!
05.13.2014 HBT Workshop @ OCA
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“Wave Noise”
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A lot has changed since 1974!S/N in Intensity Interferometry depends on
telescope size AND speed of electronics.Timing capabilities today are about 1000x
what they were in the 70’s.Can achieve the same result today with a
much smaller telescope! (Portable Instrument!)
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05.13.2014 HBT Workshop @ OCA
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Simulation Data
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Random Correlations
~|g|2
Data “Frames” ~0.4 ms long(8192 elements)
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Intensity Interferometry Revisited9
Picoquant Picoharp 300timing module.
Two SPAD detectors
Issues: Small size, dead time.
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Truly Portable
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53-m baselineSPAD
Anderson Mesa(Lowell Observatory)
Perkins Telescope
Two runs: Dec 2011 & June 2012Issues: Focus, Sky Position, Temp.
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Lowell Set-up and Data
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Big Glass is getting cheap!
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Three-Station Wireless Interferometer at SCSU
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GPSComputer Cards:~0.5mssynchronization
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Dirty Beam Simulation
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FWHM ~ 0.1 mas uv-plane coverage6-hour observation
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Kitt Peak: Another Possibility?
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Mayall+WIYN(3.8m + 3.5m)~700m baseline
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SPAD ArraysDeadtime and small size can be mitigated if you
have many SPADs all looking at the same source.Development of SPAD arrays is being started, e.g.
the SPADlab at Everyphotoncounts.com
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Optics Package for an 8-channel station
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Grating
Flat
Flat
Coll.Lens Filter
Reimager
SPAD Array
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Observation Time
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Conclusions Intensity Interferometry Opportunity Today
We’ve got intereting instrumentation for intensity interferometry: SPADs, Picoharp
Large Dobsonian Telescopes are affordable for on-campus observing.
Need to explore GPS Technology/atomic clocks for wireless operation.
Take timing correlator and the SPAD detectors to larger telescopes. “Interferometer in a suitcase.” Lowell: Already doing this. Kitt Peak: A possibility for the future.
Science: Imaging close binaries, stellar surfaces Imaging an exoplanet transit? (One fine day…)
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