Reference

This is the feature-by-feature reference for Asymmetry: what each part of the program does, the options it exposes, and the physics behind it. If you are new, start with Getting started; if you have data and want a worked end-to-end analysis, see Analysis workflows. If you are scripting or driving Asymmetry from an agent, the API cookbook collects copy-paste recipes that link out to the pages below.

Find a feature

If you know the task but not the page, this table maps the common goals to the reference page that documents them and, where it applies, the place in the graphical interface where the feature lives.

I want to…	Reference page	In the GUI
Load ISIS, PSI, or ROOT μSR files	Loading Data	File → Open Data File(s)…
Browse, sort, and annotate runs as a logbook	Logbook workflows	Data Browser
Group runs for batch fitting and organisation	GUI usage	Data Browser → context menu
Save a whole analysis session to reopen later	Project files	File → Save Project
Calibrate α from a transverse-field run	Grouping and calibration walkthrough, Alpha calibration	Grouping window → Estimate α
Define forward and backward detector groups	Detector Grouping and Layout	Detector Layout editor
Locate or override time-zero (t0)	Time-zero search	Grouping window → Find t0
Subtract a background before forming the asymmetry	Background correction, The background ladder: which stage removes what	Grouping window
Rebin histograms or set the fit time-range	Histogram binning, Data processing	Grouping window → Binning
Drop a dead or hot detector	Detector exclusion	Grouping window → Exclude Detectors
Map a multi-period pulsed-source file	Period mapping	Grouping window → Map periods…
Co-add or co-subtract runs (e.g. light-on − light-off)	Run arithmetic: co-add and co-subtract	Data Browser → context menu
Fit a model to a single asymmetry spectrum	Fitting engine	Fit dock → Single tab
Decide which model to fit	Fit wizard	Fit dock → Fit Wizard…
Fit one model across a run series	Global fit wizard, Asymmetry-domain global fit (scripting)	Fit dock → Batch tab → Global Wizard…
Judge whether a fit can be trusted	Assessing a Fit	Fit results
Build a multi-component model	Composite models	Build Fit Function dialog
Look up a fit-function form and its parameters	Fit functions	Build Fit Function dialog
Fit each detector group separately (Knight shift)	Grouped time-domain fitting	Individual Groups → Multi-Group Fit
Fit raw counts to free α or a single histogram	Count-domain fitting (α calibration & single histograms)	Multi-Group Fit → Fit target
Add a custom fit or trend function	User functions	Build Fit Function → user function
View a Fourier spectrum of the asymmetry	Fourier analysis	Frequency-domain workspace
Fit lines directly in the frequency domain	Frequency-domain fitting	Fourier panel
Read a muon hyperfine coupling from a radical	Muoniated-radical correlation spectrum	Fourier panel → Correlation (radical)
Trend a fitted parameter across a scan	Parameter trending	Fit Parameters panel
Decide where to measure next during a scan	Suggest next point	Model Fit dialog → Suggest next point
Fit λ(T) and superfluid density	Superconducting penetration depth models	Fit Parameters panel
Build an ALC / repolarisation field scan	Integral scan mode (avoided-level-crossing field scans)	Integral scan mode
Demodulate fast TF precession (rotating frame)	Rotating-reference-frame display	F-B Asymmetry plot → RRF
Generate synthetic runs to plan or rehearse	Synthetic runs and degraded statistics	File → Simulate Preset
Find a menu, panel, or keyboard shortcut	GUI usage	—

Scripting

Asymmetry is scriptable: almost everything in the GUI has a Python equivalent. The cookbook gathers short, copy-paste recipes for common tasks, each linking out to the reference page that explains it in full.

Scripting

• API cookbook

Data and projects

Everything starts with getting runs into the program and keeping track of them — reading the supported file formats, organising and annotating runs in the logbook, and saving a whole analysis (data, reduction, fits, and trends) to a project file so a session can be reopened exactly as it was left.

Data and projects

• Loading Data
• Logbook workflows
• Project files

Reduction and calibration

Before any fit, the raw detector histograms are turned into an asymmetry: detectors balanced and calibrated, backgrounds handled, time-zero located, bad detectors excluded, and pulsed-beam periods mapped. Every quantity here feeds all downstream analysis — a weak α estimate or a missed background degrades every fit made from the data — so each page is explicit about when its method applies and when it does not. The grouping walkthrough is the guided tour; the individual reduction pages below document each correction in isolation, and Exclusions: a glossary of six mechanisms disentangles the several “exclude” controls that recur across the program.

Reduction and calibration

• Grouping and calibration walkthrough
• Detector Grouping and Layout
• Data processing
• Alpha calibration
• Background correction
• The background ladder: which stage removes what
• Histogram binning
• Time-zero search
• Detector exclusion
• Period mapping
• Run arithmetic: co-add and co-subtract
• Exclusions: a glossary of six mechanisms

Setting up and running fits

The heart of the program: fitting a model to the asymmetry as a function of time. These pages run from building and judging a single fit, through the composite-model machinery and the fit-workflow diagnostics, to the grouped, global, and count-domain variants for when one forward–backward fit is not enough.

Setting up and running fits

• Fitting engine
• Assessing a Fit
• Fit workflow: asymmetric errors, chaining, and abort
• Composite models
• Grouped time-domain fitting
• Asymmetry-domain global fit (scripting)
• Count-domain fitting (α calibration & single histograms)
• User functions

Fit wizards

When you are unsure which model to reach for, the wizards fingerprint the data and recommend one. The single-fit wizard works from one spectrum; the global-fit wizard reasons across an ordered run series and proposes which parameters to share and which to let vary.

Fit wizards

• Fit wizard
• Global fit wizard

Fit-function library

The catalogue of fit components, mirroring the component picker in the Build Fit Function dialog: the relaxation and oscillation envelopes, the Kubo–Toyabe family, muonium and nuclear-dipolar (F–μ–F) models, backgrounds, and the frequency-domain lines.

Fit-function library

• Fit functions
  • Relaxation
  • Oscillation
  • Kubo–Toyabe
  • Muonium
  • Nuclear dipolar
  • Background
  • Frequency domain
  • Conventions
  • Documentation policy
  • Migrating from WiMDA

Frequency-domain analysis

When a signal is easier to read as a spectrum than a decay — several precession lines, or a vortex-lattice field distribution — these pages cover the Fourier transform and its apodisation, fitting directly in the frequency domain, the maximum-entropy estimator, the spectral moments that summarise a lineshape, and the correlation spectrum that reads a muoniated radical’s hyperfine coupling.

Frequency-domain analysis

• Fourier analysis
• Frequency-domain fitting
• Frequency-domain conditioning
• Spectral moments
• Muoniated-radical correlation spectrum

Trending and downstream models

A μSR study is rarely a single run. These pages cover following a fitted parameter across a temperature, field, or angle scan and fitting a physical model to the resulting trend — muonium kinetics, field-dependent transport, the superconducting penetration depth, and other consumers of a parameter series.

Trending and downstream models

• Parameter trending
• Suggest next point
• Muonium reaction kinetics at a pulsed source (scripting)
• Field-dependent transport models (DiffusionLF / BallisticLF)
• Superconducting penetration depth models

Specialised modes

Techniques that step outside the standard time-domain fit: integral-asymmetry field scans for avoided-level-crossing work, the rotating reference frame, full vector polarisation, and the lifetime-based analysis of negative muons.

Specialised modes

• Integral scan mode (avoided-level-crossing field scans)
• Rotating-reference-frame display
• Vector-polarisation mode
• Negative-muon capture-lifetime analysis (experimental)

Simulation

Asymmetry can generate synthetic data from any model it can fit — useful for planning a measurement, rehearsing a fitting strategy, or learning the program away from the beamline.

Simulation

• Synthetic runs and degraded statistics

The graphical interface

How the desktop application is laid out, and the conveniences that speed up everyday work — the docks and panels, and the small workflow aids the rest of this reference assumes you can find.

The graphical interface

• GUI usage
• Workflow conveniences