From 43db2162d8672260fd819025adf789171794403f Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 14:49:30 +0100
Subject: [PATCH 1/7] Add ScrapeOffLayer to physics models

---
 process/main.py                            |  3 +++
 process/models/physics/physics.py          |  3 +++
 process/models/physics/scrape_off_layer.py | 22 ++++++++++++++++++++++
 3 files changed, 28 insertions(+)
 create mode 100644 process/models/physics/scrape_off_layer.py

diff --git a/process/main.py b/process/main.py
index 551fe9f852..f7cb406b6d 100644
--- a/process/main.py
+++ b/process/main.py
@@ -103,6 +103,7 @@
 from process.models.physics.plasma_geometry import PlasmaGeom
 from process.models.physics.plasma_profiles import PlasmaProfile
 from process.models.physics.profiles import NeProfile, TeProfile
+from process.models.physics.scrape_off_layer import ScrapeOffLayer
 from process.models.power import Power
 from process.models.pulse import Pulse
 from process.models.shield import Shield
@@ -679,6 +680,7 @@ def __init__(self, data: DataStructure):
         self.plasma_current = PlasmaCurrent()
         self.plasma_fields = PlasmaFields()
         self.plasma_dia_current = PlasmaDiamagneticCurrent()
+        self.scrape_off_layer = ScrapeOffLayer()
         self.physics = Physics(
             plasma_profile=self.plasma_profile,
             current_drive=self.current_drive,
@@ -693,6 +695,7 @@ def __init__(self, data: DataStructure):
             plasma_fields=self.plasma_fields,
             plasma_dia_current=self.plasma_dia_current,
             plasma_geometry=self.plasma_geom,
+            scrape_off_layer=self.scrape_off_layer,
         )
         self.physics_detailed = DetailedPhysics(
             plasma_profile=self.plasma_profile,
diff --git a/process/models/physics/physics.py b/process/models/physics/physics.py
index ccd54551d4..59b5373269 100644
--- a/process/models/physics/physics.py
+++ b/process/models/physics/physics.py
@@ -45,6 +45,7 @@
     from process.models.physics.plasma_fields import PlasmaFields
     from process.models.physics.plasma_geometry import PlasmaGeom
     from process.models.physics.plasma_profiles import PlasmaProfile
+    from process.models.physics.scrape_off_layer import ScrapeOffLayer
 
 logger = logging.getLogger(__name__)
 
@@ -195,6 +196,7 @@ def __init__(
         plasma_fields: PlasmaFields,
         plasma_dia_current: PlasmaDiamagneticCurrent,
         plasma_geometry: PlasmaGeom,
+        scrape_off_layer: ScrapeOffLayer,
     ):
         self.outfile = constants.NOUT
         self.mfile = constants.MFILE
@@ -211,6 +213,7 @@ def __init__(
         self.fields = plasma_fields
         self.dia_current = plasma_dia_current
         self.geometry = plasma_geometry
+        self.scrape_off_layer = scrape_off_layer
 
     def output(self) -> None:
         """Output plasma physics information."""
diff --git a/process/models/physics/scrape_off_layer.py b/process/models/physics/scrape_off_layer.py
new file mode 100644
index 0000000000..c5a84d1ae1
--- /dev/null
+++ b/process/models/physics/scrape_off_layer.py
@@ -0,0 +1,22 @@
+"""Module for calculating plasma scrape off layers physics"""
+
+import logging
+
+from process.core import constants
+from process.core.model import Model
+
+logger = logging.getLogger(__name__)
+
+
+class ScrapeOffLayer(Model):
+    """Model for calculating plasma scrape off layers physics."""
+
+    def __init__(self):
+        self.outfile = constants.NOUT
+        self.mfile = constants.MFILE
+
+    def run(self):
+        """Run the model. This model cannot yet be 'run'."""
+
+    def output(self) -> None:
+        """Output plasma scrape off layer physics information."""
\ No newline at end of file

From a4881badff83bc7488b0ebf042c4e8e5dd2c49cb Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 16:14:30 +0100
Subject: [PATCH 2/7] Add calculate_eich2013_sol_power_decay_length method and
 corresponding tests

---
 process/models/physics/scrape_off_layer.py    | 46 ++++++++++++-
 .../models/physics/test_scrape_off_layer.py   | 65 +++++++++++++++++++
 2 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/models/physics/test_scrape_off_layer.py

diff --git a/process/models/physics/scrape_off_layer.py b/process/models/physics/scrape_off_layer.py
index c5a84d1ae1..cecc4083ed 100644
--- a/process/models/physics/scrape_off_layer.py
+++ b/process/models/physics/scrape_off_layer.py
@@ -19,4 +19,48 @@ def run(self):
         """Run the model. This model cannot yet be 'run'."""
 
     def output(self) -> None:
-        """Output plasma scrape off layer physics information."""
\ No newline at end of file
+        """Output plasma scrape off layer physics information."""
+
+    @staticmethod
+    def calculate_eich2013_sol_power_decay_length(
+        p_plasma_separatrix_mw: float,
+        rmajor: float,
+        b_plasma_surface_poloidal_average: float,
+        aspect: float,
+    ) -> float:
+        """Calculate the Eich 2013 SOL power decay length (λ_q).
+
+        Parameters
+        ----------
+        p_plasma_separatrix_mw : float
+            Power crossing the separatrix (Pₛₑₚ) (MW)
+        rmajor : float
+            Major radius of the plasma (R₀) [m]
+        b_plasma_surface_poloidal_average : float
+            Poloidal magnetic field at the plasma surface (⟨Bₚₒₗ(a)⟩)  [T]
+        aspect : float
+            Aspect ratio of the plasma  (A)
+
+        Returns
+        -------
+        float
+            Eich 2013 SOL power decay length (λ_q) [m]
+
+        Notes
+        -----
+        - The paper states that the poloidal field terms is for the outer midplane
+        Bₚₒₗ(a), we are using the outer surface average
+
+        References
+        ----------
+        [1] T. Eich et al., “Scaling of the tokamak near the scrape-off layer H-mode
+        power width and implications for ITER,” Nuclear Fusion, vol. 53, no. 9,
+        p. 093031, Aug. 2013, doi: 10.1088/0029-5515/53/9/093031.
+
+        """
+        return (
+            1.35e-3 * p_plasma_separatrix_mw**-0.02
+            + rmajor**0.04
+            + b_plasma_surface_poloidal_average**-0.92
+            + aspect**-0.42
+        )
diff --git a/tests/unit/models/physics/test_scrape_off_layer.py b/tests/unit/models/physics/test_scrape_off_layer.py
new file mode 100644
index 0000000000..afca46b297
--- /dev/null
+++ b/tests/unit/models/physics/test_scrape_off_layer.py
@@ -0,0 +1,65 @@
+from process.models.physics.scrape_off_layer import ScrapeOffLayer
+
+
+class TestScrapeOffLayer:
+    """Test suite for ScrapeOffLayer class."""
+
+    @staticmethod
+    def test_calculate_eich2013_sol_power_decay_length_nominal():
+        """Test Eich 2013 SOL power decay length with nominal values."""
+        result = ScrapeOffLayer.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=100.0,
+            rmajor=3.0,
+            b_plasma_surface_poloidal_average=0.5,
+            aspect=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_eich2013_sol_power_decay_length_low_power():
+        """Test with low plasma separatrix power."""
+        result = ScrapeOffLayer.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=10.0,
+            rmajor=3.0,
+            b_plasma_surface_poloidal_average=0.5,
+            aspect=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_eich2013_sol_power_decay_length_high_power():
+        """Test with high plasma separatrix power."""
+        result = ScrapeOffLayer.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=500.0,
+            rmajor=3.0,
+            b_plasma_surface_poloidal_average=0.5,
+            aspect=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_eich2013_sol_power_decay_length_large_rmajor():
+        """Test with large major radius."""
+        result = ScrapeOffLayer.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=100.0,
+            rmajor=10.0,
+            b_plasma_surface_poloidal_average=0.5,
+            aspect=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_eich2013_sol_power_decay_length_small_rmajor():
+        """Test with small major radius."""
+        result = ScrapeOffLayer.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=100.0,
+            rmajor=1.0,
+            b_plasma_surface_poloidal_average=0.5,
+            aspect=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0

From 2149e8c31fff738be17ea896a8eeb64a3aa356b8 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 16:31:30 +0100
Subject: [PATCH 3/7] Add MAST 2014 SOL power decay length calculations and
 corresponding tests

---
 process/models/physics/scrape_off_layer.py    | 67 ++++++++++++++++
 .../models/physics/test_scrape_off_layer.py   | 80 +++++++++++++++++++
 2 files changed, 147 insertions(+)

diff --git a/process/models/physics/scrape_off_layer.py b/process/models/physics/scrape_off_layer.py
index cecc4083ed..0330b9a5b4 100644
--- a/process/models/physics/scrape_off_layer.py
+++ b/process/models/physics/scrape_off_layer.py
@@ -64,3 +64,70 @@ def calculate_eich2013_sol_power_decay_length(
             + b_plasma_surface_poloidal_average**-0.92
             + aspect**-0.42
         )
+
+    @staticmethod
+    def calculate_mast2014_sol_power_decay_length_1(
+        p_plasma_separatrix_mw: float,
+        b_plasma_surface_poloidal_average: float,
+    ) -> float:
+        """Calculate the MAST 2014 SOL power decay length (λ_q).
+
+        Parameters
+        ----------
+        p_plasma_separatrix_mw : float
+            Power crossing the separatrix (Pₛₑₚ) (MW)
+        b_plasma_surface_poloidal_average : float
+            Poloidal magnetic field at the plasma surface (⟨Bₚₒₗ(a)⟩)  [T]
+
+        Returns
+        -------
+        float
+            MAST 2014 SOL power decay length (λ_q) [m]
+
+        Notes
+        -----
+        - The paper states that the poloidal field terms is for the outer midplane
+        Bₚₒₗ(a), we are using the outer surface average
+
+        References
+        ----------
+        [1] A. J. Thornton and A. Kirk, “Scaling of the scrape-off layer width during
+        inter-ELM H modes on MAST as measured by infrared thermography,”
+        Plasma Physics and Controlled Fusion, vol. 56, no. 5, p. 055008, Apr. 2014,
+        doi: 10.1088/0741-3335/56/5/055008.
+
+        """
+        return (
+            1.84e-3 * p_plasma_separatrix_mw**0.18
+            + b_plasma_surface_poloidal_average**-0.68
+        )
+
+    @staticmethod
+    def calculate_mast2014_sol_power_decay_length_2(
+        p_plasma_separatrix_mw: float,
+        cur_plasma_ma: float,
+    ) -> float:
+        """Calculate the MAST 2014 SOL power decay length (λ_q).
+
+        Parameters
+        ----------
+        p_plasma_separatrix_mw : float
+            Power crossing the separatrix (Pₛₑₚ) (MW)
+        cur_plasma_ma : float
+            Plasma current (Iₚ) [MA]
+
+        Returns
+        -------
+        float
+            MAST 2014 SOL power decay length (λ_q) [m]
+
+
+        References
+        ----------
+        [1] A. J. Thornton and A. Kirk, “Scaling of the scrape-off layer width during
+        inter-ELM H modes on MAST as measured by infrared thermography,”
+        Plasma Physics and Controlled Fusion, vol. 56, no. 5, p. 055008, Apr. 2014,
+        doi: 10.1088/0741-3335/56/5/055008.
+
+        """
+        return 4.57e-3 * p_plasma_separatrix_mw**0.22 + cur_plasma_ma**-0.64
diff --git a/tests/unit/models/physics/test_scrape_off_layer.py b/tests/unit/models/physics/test_scrape_off_layer.py
index afca46b297..d232384219 100644
--- a/tests/unit/models/physics/test_scrape_off_layer.py
+++ b/tests/unit/models/physics/test_scrape_off_layer.py
@@ -63,3 +63,83 @@ def test_calculate_eich2013_sol_power_decay_length_small_rmajor():
         )
         assert isinstance(result, float)
         assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_1_nominal():
+        """Test MAST 2014 SOL power decay length 1 with nominal values."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_1(
+            p_plasma_separatrix_mw=100.0,
+            b_plasma_surface_poloidal_average=0.5,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_1_low_power():
+        """Test MAST 2014 SOL power decay length 1 with low power."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_1(
+            p_plasma_separatrix_mw=10.0,
+            b_plasma_surface_poloidal_average=0.5,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_1_high_power():
+        """Test MAST 2014 SOL power decay length 1 with high power."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_1(
+            p_plasma_separatrix_mw=500.0,
+            b_plasma_surface_poloidal_average=0.5,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_1_high_bpol():
+        """Test MAST 2014 SOL power decay length 1 with high poloidal field."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_1(
+            p_plasma_separatrix_mw=100.0,
+            b_plasma_surface_poloidal_average=2.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_2_nominal():
+        """Test MAST 2014 SOL power decay length 2 with nominal values."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_2(
+            p_plasma_separatrix_mw=100.0,
+            cur_plasma_ma=1.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_2_low_power():
+        """Test MAST 2014 SOL power decay length 2 with low power."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_2(
+            p_plasma_separatrix_mw=10.0,
+            cur_plasma_ma=1.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_2_high_power():
+        """Test MAST 2014 SOL power decay length 2 with high power."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_2(
+            p_plasma_separatrix_mw=500.0,
+            cur_plasma_ma=1.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0
+
+    @staticmethod
+    def test_calculate_mast2014_sol_power_decay_length_2_high_current():
+        """Test MAST 2014 SOL power decay length 2 with high plasma current."""
+        result = ScrapeOffLayer.calculate_mast2014_sol_power_decay_length_2(
+            p_plasma_separatrix_mw=100.0,
+            cur_plasma_ma=3.0,
+        )
+        assert isinstance(result, float)
+        assert result > 0

From fc0e433ce722a575ff2efb57471c4c4e0dc94bbb Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 16:55:26 +0100
Subject: [PATCH 4/7] Add power decay length variables for Eich 2013 and MAST
 2014 in PhysicsData class

---
 process/data_structure/physics_variables.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/process/data_structure/physics_variables.py b/process/data_structure/physics_variables.py
index edc5b4f3fc..941b8310b4 100644
--- a/process/data_structure/physics_variables.py
+++ b/process/data_structure/physics_variables.py
@@ -1651,6 +1651,15 @@ class PhysicsData:
     res_plasma_fuel_spitzer_vol_avg: float = 0.0
     """Volume averaged plasma Spitzer resistivity due to fuel ions (ohm m)"""
 
+    len_plasma_sol_eich13_power_decay: float = 0.0
+    """Eich 2013 power decay length in the scrape-off layer scaling (λ_q) [m]"""
+
+    len_plasma_sol_mast14_power_decay_1: float = 0.0
+    """MAST 2014 power decay length in the scrape-off layer scaling 1 (λ_q) [m]"""
+
+    len_plasma_sol_mast14_power_decay_2: float = 0.0
+    """MAST 2014 power decay length in the scrape-off layer scaling 2 (λ_q) [m]"""
+
     dt_power_density_plasma: float = 0.0
     sigmav_dt_average: float = 0.0
     dhe3_power_density: float = 0.0

From 38dd4acffb614b75faf604fccc2448a0f4c3123a Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 17:26:19 +0100
Subject: [PATCH 5/7] Add scrape-off layer calculations and output to physics
 model

---
 process/main.py                            |  1 +
 process/models/physics/physics.py          |  9 ++++
 process/models/physics/scrape_off_layer.py | 59 +++++++++++++++++++---
 3 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/process/main.py b/process/main.py
index f7cb406b6d..0bd541c08f 100644
--- a/process/main.py
+++ b/process/main.py
@@ -785,6 +785,7 @@ def models(self) -> tuple[Model, ...]:
             self.plasma_bootstrap_current,
             self.plasma_exhaust,
             self.plasma_current,
+            self.scrape_off_layer,
             self.neoclassics,
             self.plasma_inductance,
             self.ne_profile,
diff --git a/process/models/physics/physics.py b/process/models/physics/physics.py
index 59b5373269..a529d3efcf 100644
--- a/process/models/physics/physics.py
+++ b/process/models/physics/physics.py
@@ -816,6 +816,13 @@ def run(self):
             )
         )
 
+        # ===============================
+
+        # Calculate scrape-off layer physics
+
+        self.scrape_off_layer.run()
+
+        # ===============================
         self.data.physics.pflux_plasma_surface_neutron_avg_mw = (
             self.data.physics.p_neutron_total_mw / self.data.physics.a_plasma_surface
         )
@@ -2337,6 +2344,8 @@ def outplas(self):
 
         self.exhaust.output()
 
+        self.scrape_off_layer.output()
+
         if self.data.stellarator.istell == 0:
             self.plasma_transition.output()
 
diff --git a/process/models/physics/scrape_off_layer.py b/process/models/physics/scrape_off_layer.py
index 0330b9a5b4..e54a626de9 100644
--- a/process/models/physics/scrape_off_layer.py
+++ b/process/models/physics/scrape_off_layer.py
@@ -3,6 +3,7 @@
 import logging
 
 from process.core import constants
+from process.core import process_output as po
 from process.core.model import Model
 
 logger = logging.getLogger(__name__)
@@ -16,10 +17,50 @@ def __init__(self):
         self.mfile = constants.MFILE
 
     def run(self):
-        """Run the model. This model cannot yet be 'run'."""
+        """Calculate the scrape off layer physics and update the physics variables."""
+        self.data.physics.len_plasma_sol_eich13_power_decay = self.calculate_eich2013_sol_power_decay_length(
+            p_plasma_separatrix_mw=self.data.physics.p_plasma_separatrix_mw,
+            rmajor=self.data.physics.rmajor,
+            b_plasma_surface_poloidal_average=self.data.physics.b_plasma_surface_poloidal_average,
+            aspect=self.data.physics.aspect,
+        )
+
+        self.data.physics.len_plasma_sol_mast14_power_decay_1 = self.calculate_mast2014_sol_power_decay_length_1(
+            p_plasma_separatrix_mw=self.data.physics.p_plasma_separatrix_mw,
+            b_plasma_surface_poloidal_average=self.data.physics.b_plasma_surface_poloidal_average,
+        )
+
+        self.data.physics.len_plasma_sol_mast14_power_decay_2 = (
+            self.calculate_mast2014_sol_power_decay_length_2(
+                p_plasma_separatrix_mw=self.data.physics.p_plasma_separatrix_mw,
+                cur_plasma_ma=self.data.physics.plasma_current / 1e6,  # Convert A to MA
+            )
+        )
 
     def output(self) -> None:
         """Output plasma scrape off layer physics information."""
+        po.oheadr(self.outfile, "Plasma Scrape Off Layer")
+
+        po.osubhd(self.outfile, "Power Decay Lengths (λ_q)")
+
+        po.ovarre(
+            self.outfile,
+            "Eich 2013 SOL power decay length (λ_q) [m]",
+            "(len_plasma_sol_eich13_power_decay)",
+            self.data.physics.len_plasma_sol_eich13_power_decay,
+        )
+        po.ovarre(
+            self.outfile,
+            "MAST 2014 SOL power decay length 1 (λ_q) [m]",
+            "(len_plasma_sol_mast14_power_decay_1)",
+            self.data.physics.len_plasma_sol_mast14_power_decay_1,
+        )
+        po.ovarre(
+            self.outfile,
+            "MAST 2014 SOL power decay length 2 (λ_q) [m]",
+            "(len_plasma_sol_mast14_power_decay_2)",
+            self.data.physics.len_plasma_sol_mast14_power_decay_2,
+        )
 
     @staticmethod
     def calculate_eich2013_sol_power_decay_length(
@@ -59,10 +100,11 @@ def calculate_eich2013_sol_power_decay_length(
 
         """
         return (
-            1.35e-3 * p_plasma_separatrix_mw**-0.02
-            + rmajor**0.04
-            + b_plasma_surface_poloidal_average**-0.92
-            + aspect**-0.42
+            1.35e-3
+            * p_plasma_separatrix_mw**-0.02
+            * rmajor**0.04
+            * b_plasma_surface_poloidal_average**-0.92
+            * aspect**-0.42
         )
 
     @staticmethod
@@ -98,8 +140,9 @@ def calculate_mast2014_sol_power_decay_length_1(
 
         """
         return (
-            1.84e-3 * p_plasma_separatrix_mw**0.18
-            + b_plasma_surface_poloidal_average**-0.68
+            1.84e-3
+            * p_plasma_separatrix_mw**0.18
+            * b_plasma_surface_poloidal_average**-0.68
         )
 
     @staticmethod
@@ -130,4 +173,4 @@ def calculate_mast2014_sol_power_decay_length_2(
         doi: 10.1088/0741-3335/56/5/055008.
 
         """
-        return 4.57e-3 * p_plasma_separatrix_mw**0.22 + cur_plasma_ma**-0.64
+        return 4.57e-3 * p_plasma_separatrix_mw**0.22 * cur_plasma_ma**-0.64

From bc5497abddfb145357d99324a1576f17d558a083 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 24 Jul 2026 17:32:52 +0100
Subject: [PATCH 6/7] Add SOL power decay length comparison plotting function
 to summary output

---
 process/core/io/plot/summary.py | 83 +++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index dc5b6052db..efc1e9fcd4 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -8914,6 +8914,85 @@ def plot_bootstrap_comparison(axis: plt.Axes, mfile: MFile, scan: int):
     axis.set_facecolor("#f0f0f0")
 
 
+def plot_sol_power_decay_length_comparison(axis: plt.Axes, mfile: MFile, scan: int):
+    """Function to plot a scatter box plot of SOL power decay lengths (λ_q).
+
+    Parameters
+    ----------
+    axis :
+        axis object to plot to
+    mfile :
+        MFILE data object
+    scan :
+        scan number to use
+    """
+    len_plasma_sol_eich13_power_decay_mm = (
+        mfile.get("len_plasma_sol_eich13_power_decay", scan=scan) * 1e3
+    )
+    len_plasma_sol_mast14_power_decay_1_mm = (
+        mfile.get("len_plasma_sol_mast14_power_decay_1", scan=scan) * 1e3
+    )
+    len_plasma_sol_mast14_power_decay_2_mm = (
+        mfile.get("len_plasma_sol_mast14_power_decay_2", scan=scan) * 1e3
+    )
+
+    # Data for the box plot
+    data = {
+        "Eich 2013": len_plasma_sol_eich13_power_decay_mm,
+        "MAST 2014 (1)": len_plasma_sol_mast14_power_decay_1_mm,
+        "MAST 2014 (2)": len_plasma_sol_mast14_power_decay_2_mm,
+    }
+    # Create the violin plot
+    axis.violinplot(data.values(), showextrema=False)
+
+    # Create the box plot
+    axis.boxplot(
+        data.values(), showfliers=True, showmeans=True, meanline=True, widths=0.3
+    )
+
+    # Scatter plot for each data point
+    colors = plt.cm.plasma(np.linspace(0, 1, len(data.values())))
+    for index, (key, value) in enumerate(data.items()):
+        axis.scatter(1, value, color=colors[index], label=key, alpha=1.0)
+    axis.legend(loc="upper left", bbox_to_anchor=(1, 1))
+
+    # Calculate average, standard deviation, and median
+    data_values = list(data.values())
+    avg_decay_length = np.mean(data_values)
+    std_decay_length = np.std(data_values)
+    median_decay_length = np.median(data_values)
+
+    # Plot average, standard deviation, and median as text
+    axis.text(
+        1.02,
+        0.2,
+        f"Average: {avg_decay_length:.4f}",
+        transform=axis.transAxes,
+        fontsize=9,
+    )
+    axis.text(
+        1.02,
+        0.15,
+        f"Standard Dev: {std_decay_length:.4f}",
+        transform=axis.transAxes,
+        fontsize=9,
+    )
+    axis.text(
+        1.02,
+        0.1,
+        f"Median: {median_decay_length:.4f}",
+        transform=axis.transAxes,
+        fontsize=9,
+    )
+
+    axis.set_title("SOL Power Decay Length ($\\lambda_q$) Comparison")
+    axis.set_ylabel("Power Decay Length [mm]")
+    axis.set_xlim([0.5, 1.5])
+    axis.set_xticks([])
+    axis.set_xticklabels([])
+    axis.set_facecolor("#f0f0f0")
+
+
 def plot_h_threshold_comparison(axis: plt.Axes, mfile: MFile, scan: int, u_seed=None):
     """Function to plot a scatter box plot of L-H threshold power comparisons.
 
@@ -16090,6 +16169,10 @@ def _add_page(name: str | None = None):
         pages["plasma_compare_2"].add_subplot(224), m_file, scan
     )
 
+    plot_sol_power_decay_length_comparison(
+        _add_page("plasma_compare_3").add_subplot(221), m_file, scan
+    )
+
     plot_debye_length_profile(
         _add_page("microscopic_quantities").add_subplot(232), m_file, scan
     )

From 53b76ab9debeb73281e59639776257ba04e079c3 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Mon, 27 Jul 2026 13:13:34 +0100
Subject: [PATCH 7/7] Add documentation for Plasma Scrape-off Layer model and
 update navigation

---
 .../physics-models/plasma_scrape_off_layer.md | 60 +++++++++++++++++++
 mkdocs.yml                                    |  1 +
 2 files changed, 61 insertions(+)
 create mode 100644 documentation/source/physics-models/plasma_scrape_off_layer.md

diff --git a/documentation/source/physics-models/plasma_scrape_off_layer.md b/documentation/source/physics-models/plasma_scrape_off_layer.md
new file mode 100644
index 0000000000..1f9c009797
--- /dev/null
+++ b/documentation/source/physics-models/plasma_scrape_off_layer.md
@@ -0,0 +1,60 @@
+# Scrape off Layer | `ScrapeOffLayer`
+
+## Power Decay Lengths
+
+In tokamak scrape-off layer (SOL) physics, $\lambda_q$ is the radial heat flux e-folding length, representing the narrow width over which exhaust power drops exponentially. It measures how tightly thermal energy exiting the core plasma is compressed onto open magnetic field lines.
+
+-----------
+
+### Eich 2013 Model | `calculate_eich2013_sol_power_decay_length()`
+
+The power decay length in metres is given by[^eich_2013]:
+
+$$
+\lambda_q = 1.35 \times 10^{-3} P_{\text{sep}}^{-0.02}R_0^{0.04}B_{\text{p}}(a)^{-0.92}\epsilon^{0.42}
+$$
+
+Here $P_{\text{sep}}$ is the plasma separatrix power in $\text{MW}$, $R_0$ is the plasma major radius in $\text{m}$, $B_{\text{p}}(a)$ is the plasma poloidal field at the outboard mid-plane measured in $\text{T}$ and $\epsilon$ is the plasma inverse aspect ratio.
+
+This can be found in Table 3 from Eich et.al [^eich_2013]
+
+The $R^2$ value for this fit is 0.88
+
+----------
+
+### MAST 2014 I | `calculate_mast2014_sol_power_decay_length_1()`
+
+The power decay length in metres is given by[^mast_2014]:
+
+$$
+\lambda_q = 1.84(\pm0.48) \times 10^{-3} P_{\text{sep}}^{0.18(\pm0.07)}B_{\text{p}}(a)^{-0.68(\pm0.14)}
+$$
+
+Here $P_{\text{sep}}$ is the plasma separatrix power in $\text{MW}$, and $B_{\text{p}}(a)$ is the plasma poloidal field at the outboard mid-plane measured in $\text{T}$.
+
+This can be found in Table 2 and Equation 3 from Thornton et.al [^mast_2014]
+
+The $R^2$ value for this fit is 0.56
+
+----------
+
+### MAST 2014 II | `calculate_mast2014_sol_power_decay_length_2()`
+
+The power decay length in metres is given by[^mast_2014]:
+
+$$
+\lambda_q = 4.57(\pm0.54) \times 10^{-3} P_{\text{sep}}^{0.22(\pm0.08)}I_{\text{p}}^{-0.64(\pm0.15)}
+$$
+
+Here $P_{\text{sep}}$ is the plasma separatrix power in $\text{MW}$, and $I_{\text{p}}$ is the total plasma current measured in $\text{MA}$.
+
+This can be found in Table 2 and Equation 4 from Thornton et.al [^mast_2014]
+
+The $R^2$ value for this fit is 0.55
+
+--------
+
+[^eich_2013]: T. Eich et al., “Scaling of the tokamak near the scrape-off layer H-mode power width and implications for ITER,” Nuclear Fusion, vol. 53, no. 9 p. 093031, Aug. 2013, doi: 10.1088/0029-5515/53/9/093031.
+
+[^mast_2014]: A. J. Thornton and A. Kirk, “Scaling of the scrape-off layer width during inter-ELM H modes on MAST as measured by infrared thermography,”
+Plasma Physics and Controlled Fusion, vol. 56, no. 5, p. 055008, Apr. 2014, doi: 10.1088/0741-3335/56/5/055008.
\ No newline at end of file
diff --git a/mkdocs.yml b/mkdocs.yml
index 42595c58bf..1c80b5d1de 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -67,6 +67,7 @@ nav:
               - Confinement time: physics-models/plasma_confinement.md
               - L-H transition: physics-models/plasma_h_mode.md
               - Plasma Core Power Balance: physics-models/plasma_power_balance.md
+              - Plasma Scrape-off Layer: physics-models/plasma_scrape_off_layer.md
               - Detailed Plasma Physics: physics-models/detailed_physics.md
           - Pulsed Plant Operation: physics-models/pulsed-plant.md
       - Engineering Models: