138 lines
No EOL
3.8 KiB
Markdown
138 lines
No EOL
3.8 KiB
Markdown
%title: Cosmic Pi - A short intro
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%author: James Devine
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%date: 2021-08-21
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-> # Cosmic Rays <-
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When we started, we had a crazy idea.
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Let's replicate CERN and put it in a box.
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Accelerator + Detector + Data Analysis
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Open source, both hardware and software.
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--------------------------------------------------
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-> # What can we do with it? <-
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Cosmic rays are implicated in our climate system.
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They can cause cloud nucleation.
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Clouds are very important for our climate.
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Two important questions:
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1) How many cosmic rays are there right now?
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2) How many cosmic rays were there before we measured them?
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-------------------------------------------------
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-> # Muons <-
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==============
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* High energy cosmic rays hit the atmosphere.
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* They decay into lower energy particles.
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* Muons can be detected at sea level.
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* With a scintillator, you can 'see' muons.
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-------------------------------------------------
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-> # Detector Technology <-
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When we started our project (2014), everyone was using GM tubes.
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This is the cold-war tech you see in movies for radiation detectors.
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We wanted to use current electronics from CERN detectors.
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1. Scintillator material (Muon -> Photons)
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2. Silicon Photomultiplier - SiPM (Photons -> Electrons)
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3. Front end (Electrons -> Digital signal)
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4. Raspberry Pi (Digital signal -> Internet)
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-------------------------------------------------
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-> # An embedded system <-
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Our version 1 was a simple PCB on top of a Raspberry Pi.
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It didn't work.
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-------------------------------------------------
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-> # Challenges <-
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A working SiPM based muon detector needs:
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* Controllable 30-70V Power supply (step up from 5V USB)
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* Analogue amplifier stages (single photon detection)
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* Trigger (screen out common mode noise)
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* Timing system (ns resolution to be useful)
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* ADC (we don't use it yet!)
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* Other sensors (GPS, Accelerometer, Magnetometer, Humidity)
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-------------------------------------------------
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-> # Timing Resolution <-
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c = 3e8m/s
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timing bucket = 65ns
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spatial resolution = 20m
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This is about what is easily achievable with off the shelf electronic parts.
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Good enough for our application.
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-------------------------------------------------
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-> # Design Philosophy: Hardware <-
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Accelerometer ----
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|---- I2C Bus
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Humidity Sensor ----
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GPS --------------------- UART2
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Voltage control --------- SPI
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Raspberry Pi ------------ UART1
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-------------------------------------------------
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-> # Design Philosophy: IoT <-
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The architecture of the system is critical to success:
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* Hard Realtime - Arduino (minimum latency) - C
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* Near Realtime - Raspberry Pi (lowish latency) - Python
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* Archive/Presentation - Raspberry Pi/PC. (buffers) - Python
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This is a very common architecture.
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Many systems have this type of requirement.
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-------------------------------------------------
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-> # An internet telescope <-
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It took us a few years to make working hardware.
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And then to build the infrastructure needed to harvest!
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* Each detector has an MQTT client (lightweight IoT protocol)
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* Single (or multiple) MQTT brokers (messaging bus)
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* Server listens to bus and collects muon data via Python
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* Build database + visualisation with InfluxDB and Grafana
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-------------------------------------------------
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-> # We are now building up our dataset: <-
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* Detector location (Lat/Long)
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* Event time (ns precision)
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* Detector orientation (Acceleration in X, Y and Z)
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* Detector magnetic field (X, Y, Z)
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* Air Pressure
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* Humidity
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* Temperature
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-------------------------------------------------
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Let me know if you are interested in our dataset!
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cosmicpi.detector at gmail.com
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-------------------------------------------------
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-> # Live demo? Yes please! <-
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MQTT: data.cosmicpi.org (port 1883)
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cosmicpi
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MuonsFROMSp8ce
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Web: https://data.cosmicpi.org
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Blog: https://cosmicpi.org
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(a better server is in the post!) |