Capacitance Dilatometry Processor

for Quantum Design PPMS® systems

Reduction, quality control, and plotting for capacitance dilatometry data measured in a Quantum Design PPMS with Küchler-type BeCu dilatometers (standard cell: RSI 83, 095102 (2012); uniaxial-stress cell: RSI 87, 073903 (2016); mini cell: RSI 88, 083903 (2017)).

From a raw PPMS .dat export it produces referenced thermal expansion ΔL/L₀(T), magnetostriction ΔL(B) loops, the linear expansion coefficient α(T), angle-resolved (polar) anisotropy figures, and a per-run provenance JSON with physical quality gates.

Install

Python ≥ 3.10 with the standard scientific stack:

pip install -r scripts/requirements.txt

Tkinter (bundled with python.org installers; python3-tk on Debian/Ubuntu) is needed only for the GUI launcher.

The full user guide — install variants (incl. fully offline machines), every workflow, troubleshooting — is docs/guide.html (open in any browser).

Quick start

GUI — pick a file, detect the cell, run reduction, inspect results:

python3 scripts/dilat_app.py

Standard/stress-cell run (single file):

python3 scripts/reduce_str_batch.py --data /path/to/folder --file myrun.dat \
        --L0 0.058 --transition 100

--L0 is the sample thickness in cm; --transition (optional) draws the transition line and splits the ferro/para magnetostriction panels. Outputs land in Output/str/<input-stem>_* (CSV + PNG + _provenance.json with the gate results).

Mini-cell rotation series (multi-angle): describe your angle files once in an angle_runs.json next to the data (required — there is no built-in run list):

{"stem": "MYSAMPLE_mini",
 "L0_cm": 0.02,
 "transition_K": 100.0,
 "runs": [{"angle_deg": 0,   "tag": "rot0",   "glob": "*rot0*.dat"},
          {"angle_deg": 45,  "tag": "plus45", "glob": "*plus45*.dat"},
          {"angle_deg": -45, "tag": "minus45","glob": "*minus45*.dat"}]}

python3 scripts/reduce_mini_batch.py --data /path/to/folder

Per-angle outputs plus combined overlay and polar-anisotropy figures are written to Output/mini/<stem>_*. An optional per-run "rescale" factor corrects raw δl converted with the wrong plate radius.

Interactive QC (trim, smooth, exclude curves, re-export) opens from the GUI's results table, or directly:

python3 scripts/qc_str_cell.py --data /path/to/folder --file myrun.dat

Calibration — bring your own cell

The empty-cell (Cu) background is read from scripts/calibrations.json. The shipped registry is a labelled example — the authors' dilatometers, not yours. Every script that loads it prints a banner and stamps example_registry: true into the run's provenance JSON until you replace it.

Build your own from empty-cell Cu reference runs. Describe the runs once in a cu_runs.json next to your Cu .dat files (same convention as angle_runs.json above; full field reference in the module docstring, and scripts/cu_runs.example.json is the worked example that produced the shipped registry):

{"runs": [
  {"key": "mycell_1mm", "path": "Cu_1mm_run.dat",
   "cell": "my_cell", "cu_length_mm": 1.0},
  {"key": "mycell_2mm", "path": "Cu_2mm_run.dat",
   "cell": "my_cell", "cu_length_mm": 2.0}]}

python3 scripts/cu_calibration_builder.py --data /path/to/cu/folder

This segments cool/warm branches, repairs offset steps, fits the per-branch polynomial backgrounds, runs the round-trip gate (each Cu run reduced with its own calibration must return Cu literature), writes QC figures to fig_calibration_QC/, and saves the registry to scripts/calibrations.json (or --out; point DILAT_CALIBRATIONS at it to keep several). Two Cu lengths per cell enable the Eq.-(7) thickness-matched virtual curves; optional transfer_pairs / eq7_pairs / hysteresis_pairs lists and a kind: "field" run (field-background envelope) are described in cu_calibration_builder.py --help and its module docstring. Per-branch manual repairs (exclusion windows, forced step rows, use: false) go in scripts/calibration_config.json, keyed <key>/c<cycle><w|c>.

The registry stores branch-aware (cool/warm) polynomial backgrounds, the P18 Eq. (7) length decomposition for thickness-matched virtual curves, and a field-background envelope. Selection at load time prefers an Eq.-(7) virtual curve at your sample thickness when its fitted T-range covers the run (≤ 5 K overhang tolerated), falling back to the closest-length record otherwise — the choice is recorded in each run's provenance JSON.

Layout

scripts/
  dilat_app.py                 Tkinter launcher (detect → reduce → QC)
  reduce_str_batch.py          headless reduction, standard/stress cell
  reduce_mini_batch.py         headless reduction, mini cell rotation series
  qc_str_cell.py               interactive QC, standard/stress cell
  qc_mini_cell.py              interactive QC, mini cell
  polar_figures.py             standalone polar/anisotropy figures
  reduce.py, cleanup.py, cells.py, detect.py, samples.py   shared core
  cu_calibration_builder.py    build calibrations.json from Cu runs
  calibration_bridge.py        minimal calibrations.json reader for any script
  plate_constant_audit.py      plate-constant audit (wrong-radius detector)
  calibrations.json            cell-background registry (EXAMPLE — see above)
  cu_runs.example.json         worked cu_runs.json (the runs behind the
                               shipped registry)
  samples.json                 sample registry (ships one EXAMPLE entry —
                               add your samples: T_C window, L0 hints)

Convention: qc_str_cell.py and qc_mini_cell.py are deliberate standalone twins — no shared QC module. Any change to their shared logic (QC window, plotting, calibration loading) must be replicated in both; parity is part of review.

Units

T in K; B in T; raw δl in 10⁻⁶ cm; sample length L₀ in cm inside the code (mm in the GUI); ΔL/L₀ dimensionless (plots ×10⁻³); α in 10⁻⁶ K⁻¹.

License and citation

Licensed under the MIT License (see LICENSE). If this software contributes to a publication, cite it (see CITATION.cff) together with the Küchler dilatometer papers above.