%title: Cosmic Pi - A short intro
%author: James Devine
%date: 2021-08-21

-> # Cosmic Rays <-

When we started, we had a crazy idea.
Let's replicate CERN and put it in a box.
Accelerator + Detector + Data Analysis
Open source, both hardware and software.

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-> # What can we do with it?  <-

Cosmic rays are implicated in our climate system.
They can cause cloud nucleation.
Clouds are very important for our climate.

Two important questions: 

1) How many cosmic rays are there right now?
2) How many cosmic rays were there before we measured them?

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-> # Muons <-
==============

* High energy cosmic rays hit the atmosphere.
* They decay into lower energy particles.
* Muons can be detected at sea level.
* With a scintillator, you can 'see' muons.

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-> # Detector Technology  <-

When we started our project (2014), everyone was using GM tubes.
This is the cold-war tech you see in movies for radiation detectors.
We wanted to use current electronics from CERN detectors. 

1. Scintillator material (Muon -> Photons)
2. Silicon Photomultiplier - SiPM (Photons -> Electrons)
3. Front end (Electrons -> Digital signal)
4. Raspberry Pi (Digital signal -> Internet)

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-> # An embedded system  <-

Our version 1 was a simple PCB on top of a Raspberry Pi.

It didn't work. 

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-> # Challenges  <-

A working SiPM based muon detector needs:

* Controllable 30-70V Power supply (step up from 5V USB)
* Analogue amplifier stages (single photon detection)
* Trigger (screen out common mode noise)
* Timing system (ns resolution to be useful)
* ADC (we don't use it yet!)
* Other sensors (GPS, Accelerometer, Magnetometer, Humidity)

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-> # Timing Resolution  <-

c = 3e8m/s
timing bucket = 65ns
spatial resolution = 20m

This is about what is easily achievable with off the shelf electronic parts.
Good enough for our application.

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-> # Design Philosophy: Hardware  <-

Accelerometer   ----
                    |---- I2C Bus
Humidity Sensor ---- 

GPS --------------------- UART2

Voltage control --------- SPI

Raspberry Pi ------------ UART1

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-> # Design Philosophy: IoT  <-

The architecture of the system is critical to success:

* Hard Realtime - Arduino (minimum latency) - C
* Near Realtime - Raspberry Pi (lowish latency) - Python
* Archive/Presentation - Raspberry Pi/PC. (buffers) - Python

This is a very common architecture.
Many systems have this type of requirement. 

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-> # An internet telescope  <-

It took us a few years to make working hardware.
And then to build the infrastructure needed to harvest!

* Each detector has an MQTT client (lightweight IoT protocol)
* Single (or multiple) MQTT brokers (messaging bus)
* Server listens to bus and collects muon data via Python
* Build database + visualisation with InfluxDB and Grafana

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-> # We are now building up our dataset: <-

* Detector location (Lat/Long)
* Event time (ns precision)
* Detector orientation (Acceleration in X, Y and Z)
* Detector magnetic field (X, Y, Z)
* Air Pressure
* Humidity 
* Temperature

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Let me know if you are interested in our dataset!
cosmicpi.detector at gmail.com

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-> # Live demo? Yes please!  <-

MQTT: data.cosmicpi.org (port 1883)
cosmicpi
MuonsFROMSp8ce

Web: https://data.cosmicpi.org

Blog: https://cosmicpi.org

(a better server is in the post!)