From 6262e53952e13828e175a7febd151841aba8d958 Mon Sep 17 00:00:00 2001
From: Jonathan Maddock <78556175+jonmaddock@users.noreply.github.com>
Date: Tue, 11 Mar 2025 11:22:00 +0000
Subject: [PATCH] Continuous kludge to keep pdivt > 0

---
 process/physics.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/process/physics.py b/process/physics.py
index eadcc389b8..ebec167d15 100644
--- a/process/physics.py
+++ b/process/physics.py
@@ -2240,9 +2240,12 @@ def physics(self):
             - physics_variables.p_plasma_rad_mw
         )
 
-        # The following line is unphysical, but prevents -ve sqrt argument
-        # Should be obsolete if constraint eqn 17 is turned on
-        physics_variables.pdivt = max(0.001e0, physics_variables.pdivt)
+        # KLUDGE: Ensure pdivt is continuously positive (physical, rather than
+        # negative potential power), as required by other models (e.g.
+        # Physics.calculate_density_limit())
+        physics_variables.pdivt = physics_variables.pdivt / (
+            1 - np.exp(-physics_variables.pdivt)
+        )
 
         # if double null configuration share the power
         # over the upper and lower divertor, where physics_variables.ftar gives