diff --git a/src/toolbox_scs/constants.py b/src/toolbox_scs/constants.py
index 4d78bcb357428978744a831bbb77b5f784b54af8..f364dc23239519421dd6005e0ef6eff0a525ff41 100644
--- a/src/toolbox_scs/constants.py
+++ b/src/toolbox_scs/constants.py
@@ -188,7 +188,10 @@ 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_N_raw": ({'source': 'SA3_XTD10_PES/ADC/1:network',
                    'key': 'digitizers.channel_4_A.raw.samples',