# Power saturation analysis

A crucial step when recording cw-EPR spectra is to optimise the microwave power and to prevent saturation from distorting the signal shape. Therefore, usually a power saturation analysis is conducted, *i.e.* recording a series of spectra with systematically varying the microwave power.

From the resulting data, the EPR signal amplitude is extracted and plotted as function of the square root of the microwave power. As long as no saturation is occurring, there should be a linear dependency between signal amplitude and square root of microwave power. To further help with analysis, a linear regression covering the first *n* points can be performed and the results plotted together with the power saturation curve on one figure.

```
1format:
2 type: ASpecD recipe
3 version: '0.2'
4
5settings:
6 default_package: cwepr
7 autosave_plots: false
8
9directories:
10 datasets_source: ../../tests/io/testdata/
11
12datasets:
13- BDPA-2DFieldPower
14
15tasks:
16- kind: processing
17 type: BaselineCorrection
18- kind: singleanalysis
19 type: AmplitudeVsPower
20 apply_to:
21 - BDPA-2DFieldPower
22 result: power_sweep_analysis
23- kind: singleanalysis
24 type: FitOnData
25 properties:
26 parameters:
27 order: 1
28 points: 5
29 return_type: dataset
30 apply_to:
31 - power_sweep_analysis
32 result: fit
33 comment: Linear fit covering the first five data points.
34- kind: multiplot
35 type: PowerSweepAnalysisPlotter
36 properties:
37 properties:
38 drawings:
39 - marker: '*'
40 - color: red
41 grid:
42 show: true
43 axis: both
44 axes:
45 title: Overview
46 ylabel: '$EPR\ amplitude$'
47 yticklabels: []
48 apply_to:
49 - power_sweep_analysis
50 - fit
51 result: overview
52- kind: multiplot
53 type: PowerSweepAnalysisPlotter
54 properties:
55 properties:
56 drawings:
57 - marker: '*'
58 - color: red
59 grid:
60 show: true
61 axis: both
62 axes:
63 title: Detailed view
64 xlim: [0, 1.65]
65 ylim: [0, 70]
66 ylabel: '$EPR\ amplitude$'
67 yticklabels: []
68 apply_to:
69 - power_sweep_analysis
70 - fit
71 result: details
72- kind: compositeplot
73 type: CompositePlotter
74 properties:
75 plotter:
76 - overview
77 - details
78 filename: power_sweep_analysis.pdf
79 caption:
80 title: Power saturation analysis.
81 text: >
82 The left panel provides an overview of the entire measurement,
83 while the right panel provides a detailed view of the first points,
84 showing that 1 mW of microwave power already starts to saturate the
85 cw-EPR signal.
86 grid_dimensions: [1, 2]
87 subplot_locations:
88 - [0, 0, 1, 1]
89 - [0, 1, 1, 1]
```