Building scientific experiments with F#, leveraging its powerful Async and Reactive programming features. From F# eXchange 2016.

1. Building scientific
experiments with F#
A. Tcholakov, B. L. Green, A. C. Frangeskou, C. J. Stephen, P. Diggle,
J. Lishman, T. Wheeler, M. E. Newton, and G. W. Morley

2. A. Tcholakov, B. L. Green, A. C. Frangeskou, C. J. Stephen, P. Diggle,
J. Lishman, T. Wheeler, M. E. Newton, and G. W. Morley
Building scientific
experiments with F#

3. A. Tcholakov, B. L. Green, A. C. Frangeskou, C. J. Stephen, P. Diggle,
J. Lishman, T. Wheeler, M. E. Newton, and G. W. Morley
Building scientific
experiments with F#

4. A. Tcholakov, B. L. Green, A. C. Frangeskou, C. J. Stephen, P. Diggle,
J. Lishman, T. Wheeler, M. E. Newton, and G. W. Morley
Building scientific
experiments with F#

5. A. Tcholakov, B. L. Green, A. C. Frangeskou, C. J. Stephen, P. Diggle,
J. Lishman, T. Wheeler, M. E. Newton, and G. W. Morley
Building scientific
experiments with F#

6. Anatomy of an experiment
PC
Output
device
Input
device
Science!
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7. • Concurrent control of multiple devices
• Cancellation
• Reporting of partial progress
• Signal processing
• Robust error handling
• Good performance
Requirements
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8. • Concurrent control of multiple devices
• Cancellation
• Reporting of partial progress
• Signal processing
• Robust error handling
• Good performance
Requirements… and solutions
Async<'T>
IObservable<'T>
Choice<'T1,'T2> or exn?
}
}
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9. • Software isn’t actually the key output
• Experiments start as prototypes
• Need path to fully-fledged application
Requirements (process)
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10. • National Instruments VISA
• C API + DLL import
• Typically very imperative and stateful
• Inherently Async, MailboxProcessor-like
Instrument I/O
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11. Command-request agent
• Module for creating MailboxProcessor agents
which process Command or Request messages
• Instrument APIs often have large surface area
• Propagates errors to caller without stopping the
agent
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12. Code…
Command-request agent
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13. Oscilloscope
• Essential tool in a
physics lab
• Records voltages
against time
• Has settings for
triggering, input
range, offset, etc.
Source: “Oscilloscope.” Wikipedia: The Free Encyclopaedia.
Wikimedia Foundation, Inc. 20 Mar 2016. Web. 13 Apr 2016.
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14. Code…
PicoScope agent
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15. PicoScope agent: review
• Async but still imperative
• Device is typically used in one of several modes:
streaming, block acquisition, etc.
• Functional approach:
- model acquisition configuration
- define workflow to run a general acquisition
- push sample blocks via IObservable<'T>
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16. Code…
PicoScope streaming
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17. @ant_pt

18. laser
to optical fibre
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19. laser
to optical fibre
sample
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20. laser
to optical fibre
sample
todetector
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21. laser
to optical fibre
sample
todetector
microwave oscillator
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22. laser
to optical fibre
sample
todetector
microwave oscillator
toantenna
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23. laser
to optical fibre
sample
todetector
microwave oscillator
toantenna
frequency tuning
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24. laser
to optical fibre
sample
todetector
microwave oscillator
toantenna
frequency tuning
magnet
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25. Code…
N-V-
spectrometer
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26. N-V-
spectrometer: review
• Declarative streaming API makes code
straightforward to read, write, and modify
• IObservable<'T> + FSharp.Control.Reactive
offer a powerful way to implement DSP
• FSharp.Charting is great for prototyping
• Async provides robust cancellation support
• MailboxProcessor ensures sequential I/O
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27. 397 GHz spectrometer
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28. 397 GHz spectrometer
• Irradiate sample with
397 GHz mm-waves
• Sweep field on
superconducting
magnet system
• Measure what comes
back and stream
data with PicoScope
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29. 397 GHz spectrometer
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30. Confocal microscope
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31. Confocal microscope
• 3-axis piezoelectric
scanning stage for
imaging
• Photon counting
detection
• Single molecule
sensitivity (for
fluorescent samples)
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32. Confocal microscope
Pulse length
(1ns resolution)
Integrated
photon counts
Acquisition
parameters
System development time: ~9 months
Oscillations represent
manipulation of a qubit!
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33. Performance
• Hasn’t really been a problem
• PicoScope streaming acquisition copes with 32ns
sample interval (fastest available) in .fsx
• Time tagging acquisition copes with several
million photon counts per second
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34. Towards open source…
• Aim to publish the code under Apache 2.0
• Wrappers for several common lab instruments
• First need to:
- migrate to Paket, FAKE
- make namespaces consistent
- consolidate git branches
- write some unit tests (?)
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35. Conclusions
• F# is a great fit for instrument control thanks to
powerful Async, Reactive programming features
• Functional paradigm + .fsx aids prototyping
• Units of measure are the cherry on top
• Working towards open source instrument
libraries
@ant_pt