# The welcome demo experiment

A complete measurement on one PC, with no instrument attached: the first thing
to try on a new bench. It runs the PLESTY experiment `pol-pl` —
polarisation-resolved photoluminescence — which turns a half-wave plate and
takes a spectrum at each angle. Two **devices** take part: a device is one
instrument as the bench serves it. Here the rotation stage runs in its
simulator, and the spectrometer replays spectra really measured in the lab, so
the run, its data, its plots and its report are those of a real measurement.

## Start it

The first start of an empty bench opens **Welcome to PLESTY Bench**; *Help ▸
Welcome…* opens it again at any time.

```{image} imgs/gui/dialog-welcome.png
:width: 560px
:alt: The Welcome to PLESTY Bench dialog: what the demo does, an Operator field, Start the run once it is created, and Install the demo
```

1. **Operator**: your name. It is kept with the run, and proposed for the next
   one.
2. Leave **Start the run once it is created** ticked to measure at once.
   Unticked, the run is created and waits for **Run**
   ![Run](imgs/gui/btn-experiment-run.png){height=22px}.
3. Press **Install the demo**. **Not now** closes the page; it does not open
   by itself again.

It needs the network for a few minutes, and git, which the bench installs for
itself on Windows when it has none. Nothing leaves the PC.

## What it sets up

| | |
|---|---|
| **Experiment** | `pol-pl`, the module `plesty-pol-pl`, installed from its repository at the release tag `v0.2.0` and declared under that name. |
| **First run** | `pol-pl-<date>-001`, started from the module's `config/demo.yaml`. |
| **Stage** — `hwp` | The Thorlabs K10CR1 rotation stage, the released `plesty-k10cr1` 0.3.0, in its simulator. |
| **Spectrometer** — `spec` | A fixed commit of the `demo/pol-pl` branch of the LightField spectrometer module, which answers with spectra recorded on sample E098-SIL instead of exposing a camera. |

All three are pinned — the experiment by its release tag, the two devices by
that release's `setup.yaml` — so a bench runs the same demo however the
repositories move on.
| **Folder** | `<home>/demo/pol-pl` — the runs and the spectrometer replaying them share it. `<home>` is the bench's [home folder](cli/files.md#the-home-directory). |

The run measures quantum dot QD-002 with the half-wave plate turned from 0° to
178° in 2° steps — 90 angles, a 3 s exposure each. Those are the angles the
recording holds; the spectrometer refuses any other rather than answer with a
different spectrum. The experiment cannot tell the replay from an instrument,
and there is no demo mode in it: `config/demo.yaml` is the configuration a
hardware run takes, set to the sweep that was recorded.

The two devices are brought up by the run itself when it starts, from the
experiment's setup — they appear on the **Devices** tab while it measures.
The folders the spectrometer is given reach it only while the demo serves it;
another experiment that uses a spectrometer called `spec` does not inherit
them.

## Watch it

While the run measures, the banner across the top of the window names it, how
far it has got and how many of its devices are up —
*pol-pl · pol-pl-20261027-001 · 41/90 steps · devices 2/2 up*. Select the run
on the **Experiments** tab:

- **Log** — what the run prints, one line per angle.
- **Data** — each step's record: the angle, the spectrum's file and what the
  analysis found in it.
- **Visualization** — the experiment's own plots of the run.

Each pane is described in [The Experiments tab](gui/experiments.md#the-panes).

## The result

When the last angle is done the run reads `completed`, and its folder,
`<home>/demo/pol-pl/<run>`, holds:

- `raw/spec/` — the 90 spectra, one file per angle;
- the run's journal, records and configuration;
- `report.html` — the run's report: data, analysis, notes and device setup in
  one file. **Open run** ![Open run](imgs/gui/btn-experiment-open.png){height=22px}
  opens the folder; the **Report** pane names the file.

How to read it is in [Run results](usage/experiment.md#run-results).

## Afterwards

- **Measure again** — select the run and press **Duplicate**
  ![Duplicate](imgs/gui/btn-exp-duplicate.png){height=22px}, then **Run**; or
  **Create** ![Create](imgs/gui/btn-exp-create.png){height=22px} a new run of
  `pol-pl` and change its settings in **Configure** first. Each run is a new
  folder beside the first.
- **Across two PCs** — the same experiment with the spectrometer on another
  bench is [Run a cross-bench experiment](cross_bench.md).
- **Your own instrument** — [Set up a bench](usage/first_bench.md) from
  installing its module to a running device.
- **Remove it** — *Experiment ▸ Remove experiment* drops the declaration; its
  runs stay in `<home>/demo`. *Hub ▸ Installed modules…* then uninstalls the
  module.