diff --git a/doc/changelog.rst b/doc/changelog.rst
index e3555b0ac150a2ae07c63b45be94238dda4cb4d3..43cf1a3dc2aa77147d2a492ff48cf9fe3fc0d1eb 100644
--- a/doc/changelog.rst
+++ b/doc/changelog.rst
@@ -25,6 +25,7 @@ unreleased
     - add BAM average and BAM feedbacks mnemonics, Viking mnemonics :mr:`305`, :mr:`306`
     - improved function to load PES spectra :mr:`309`
     - Gotthard-II mnemonics and pulse alignment :mr:`310`, :mr:`311`
+    - Adds ``AppleX`` polarization mnemonics :mr:`313`
 
 - **New Features**
 
diff --git a/src/toolbox_scs/constants.py b/src/toolbox_scs/constants.py
index ba0945c5cfe239c109fb5cc6ec187a9a6264615a..a59636f9ecdb80687a4e009f4dcf983c9a974440 100644
--- a/src/toolbox_scs/constants.py
+++ b/src/toolbox_scs/constants.py
@@ -156,6 +156,9 @@ mnemonics = {
     "MAG_CHICANE_DELAY": ({'source': 'SA3_XTD4_CHICANE/DOOCS/SXR2CPP',
                            'key': 'XFEL_MAGNETS_CHICANE_SXR2CPP.dtFs.value',
                            'dim': None},),
+    "AppleX": ({'source': 'SA3_XTD10_UND/DOOCS/PHOTON_ENERGY',
+                'key': 'actualPolarization.value',
+                'dim': None},),
 
     # PES
     "PES_1Araw": ({'source': 'SA3_XTD10_PES/ADC/1:network',