diff --git a/images/greenPhoton.png b/images/greenPhoton.png
index a8f6eaf..08b6310 100644
Binary files a/images/greenPhoton.png and b/images/greenPhoton.png differ
diff --git a/images/greenPhoton_png.ts b/images/greenPhoton_png.ts
index 6b87fa5..8064bac 100644
--- a/images/greenPhoton_png.ts
+++ b/images/greenPhoton_png.ts
@@ -6,5 +6,5 @@ import asyncLoader from '../../phet-core/js/asyncLoader.js';
 const image = new Image();
 const unlock = asyncLoader.createLock( image );
 image.onload = unlock;
-image.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADIAAAAyCAYAAAAeP4ixAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAA3+SURBVGhD3Vp5bFzFGf/2Xh+763V8rG/HOZyDkAQSSICWO9A/ooIE5S5taaSKIqAEFARqRQtSS0pJJVoSVaitUCVOtSqI0ITUBBUi2pJCIOSAJHYcH2s7tne9u957t98x897bdU6av/p9mZ1v5s375vebb968eePYisUi/D/IOSWSL+ad/en+7oHMwLyB9MC8dDFVWSgW7HabvUDXg47gaIun9csub9feWmdtmG86R/I/ExnLjrX0RP5+y0eJ3dfui392WaqYrrbZbEBKonOSolbsMuRu7FtSdf57l/gveWO175K3XDZXWjX7SvKVifwz9uH1r4y9+tAn8U+uttuB/rEKBVQLGasIkSIU2Cqweu0V0TU11754c90tz4bcoT7V9KzkrIl8kvj48ueGn9vUl+xdjlMGHKhMAW2hoX6xTGKlQj2ZRCxUikIIG+euDlzz4rrQuseCztoRuevM5IyJxPKx4KahTb/ZGem53WEj+KicEwH8tRBhCxmcLCIF7NPldFMYIZ5JGERyxRznbrsnek/jPY/dMOvG59Vtp5UzIvJZ4tNLf9b/xEsTuUibU5GgnAjo3I7IhYoiZEyt0pjoiCxoWwy9o4chloox+DxpMc82EaLySt/Fb2xo3fBdv8M/oRycVE5LZHtk2x0bB57+A5ouJ7gYuCaCvxgVAo62yiUqemqVR0RI1Nc0QFdoLuw+8m9IpOMIWVHByBABTYTyJnfTwZ93Pv0NzHuVkxPKKYm8fvy1+58f+u2vHXaHzYmgXfgrFmpZROhXppcoRYREoiJC0fA4PbCkcxlOKzv86/CHkMomEbIQyWFEKCposY2/TMZn94d/OeeZqzs9nfuUqxkiT+QJ5O3JrXeXkqBouDAmqJRjctvcKlltSdTOY/OU1FG5O7QQVykvX8dhUdfYK9vatzXFCrHQo70bto1kwx0K3gw5YUQ+xpVpfe+PduA4OzUJioZMLYoG2TSdaHJRlCgi9JwY8cCI6EkmEaFoNAZC0F7faZR3HXof8gWZRhQJtjACOhLZEjuL06x53+a5Wy7CgUiwE4vMiMh4bjz0JD7YCEeRkEQk9AjxCHKuRl/V6dHlnNQou8Dv9sOcWfO4Hu/mAaBffb/VL6uyqZ0evKHM4KJNg89uUVBLZAaRZwd/9Xw0N9VkOiBnZiSEFOVmZyYZDd4DHjtNJZlOlOY3LMA6D4MkMo4CTisiRT41cFTdj/Rh9seK9rvRnjvfi+68ScE1pITIB1Pvr9019cGNPFXUdNEOTkiCATh5zhN4KhtkSJXdGmiHWd46qUOldo6ig30Y7TGZPiWZfetVUnRLePOmZCFZrWCzGERw3bBvHt6yUVYgUasT5VY6MAhJudJVBZ11sxGMBiY5RcKHU6qztssgYGixdFpZ/bF37put0jKmyexk66vHX1mvoLMYRN6N9Nw8mDm2gJkzeH6cTVX1fA3VmM+YbHncBAaaoa22UxHRyQXz6rrBa5NVishodSARvp/qlR9eFbFfKxlaMzlhWSFB0Hb4y/E/32+NikHk9eOvPyAvNOOtoICLIx4NVOqCp5hR5wJ7Edemgg1aalqhJdBqEKEpVeMJClilAp2mlt0goBP3QLmlP4MCroIyyIIrVUjVbpv823cUfCHSnz7afWB6/yrdiEedciaFDsgRKjm3jhCR0CBwjeSa1mAHNPmaIeAOIJEOBm0loAk5dUQUAYmE7glV4aBEyzr1J2hkkGlZ3x7ZfhezQGEiPZGeb+GbGJtLE8nJgU5Y0o6VEindOWkxjxtBVLJpis1t6OZnRJPQBIQORdGMiDH62h/2YwyeUqbAOEwsh5JfXjSUGeoyiHwU232Nhs8ELJYkrRJenbQSgEI+z7YGWumoMmwrAW3TqkUABThFWXxJb2r0aWitSV2XwRbE/4nvvoaJ4BvTcyC5bxXvXo2bbFDh8UJbYzumDgjNauKNXq2vDvwVNeDzBnDPVMH7JgJAQIq5AkMQGKIaPKk1InRNBkVsQ1U0jJFnqFY1Z4tQscGniT2XMxH8xp6PGwO3NDOZZjJZGI+MQ3VFNRJphpb6NibV2dwFXc1zobttIW7Fz4PFHUthQetiqPeHmISVCGk5Ca20akkkVDQwCUhSPfIzqdAgM0416EfSfUuYyNH00QVySVS23kImm8nAkf5DMBmVzwFrO63UzoVvcZcd5z2qJkOqiWi1kmmobISLWy+FVW2Xwap2TB2Xwcr21VDjDaIXAipg+bvGmtQ1reHU0Dx6B9onsuMhqpgJU2pwbwfh0SEYDPdDsVBQ12YqkbBqORkrCX2NVN8bxw+sz4f3QDwdEwKs9BBrW9eUWhnIeOP5eNCOLxUf1vEFyXUzRYRz/NSNT8GRgcOQSie5vlylnamaEKkmQzmB1/XUjgZqINIPB0f3QTaXpRrjfvF0Mkxi0e90ftpnzxQzHr5SJuU3kpXNZuDo0BGYiI6rOlPMdqWi6zUBEl1HW/nBaD+MxUeMOrqqRdeV59Y2JMjBa6+wV8zY259ScARHJ4ZhYKQfcvgtQWCkemZOqj5iaQpAFpXKpLpda00HLG25EHfHC3mbU+U294K6zekEOcTtlfaqKVVm0TeX5yY0sRLJGEcnmZ42gGmQWomA+jRiItqmerqu76GH2Of1I6l2WNS8BJa3r4Q5DfOh3tcILlzipddSLOYvQKW9MmYPuRuPUgMNkMRattpmDe+WIZNPw7GRPkik4lzWSkDLSVA0dK7rNaFydTgcEKyuhdkNc+CCzhWwrONC6GzowrpZ/K1vokASjurJKkdV1N7uaT8olVagpSruzZIksR1O3Gp4PNyCtJyEBq5JaNXXdXtS8SiayWf4YCKajEAyN80E/JV+aA42g9ddgS0Fbaun9SARsuG3sv2bn689ni6mg7w3wret7F71wYEuy/cFl0mxTPuk2Y1zIYBveyduOeLxGL8H6PvkRCuUkBewkdQETKYmaRcL07kEYP+QyMYhWUhzGR9g/E5H+pwwmphTG6OMmsa219Vev/mB5gfvpTPbwtLqZTvN0TC7KxYpoc0Jr/FxDY26jHxVVTV4KrwQnY7AkeEvYDQybIy2OfaiBAKXSQZAintGGI4Nwmg8DJPJCTXySYxEir1LEjz0S/2JrXASNtTlVct7KCK8Hq6svmgbHWPy0SUB1Uk5EJWy1OBqhStgZXU19IUPw7GxPgZBJx00WawESAl4ODYEB0Y+g+PJMSbqdLugCrc/chgnic+y9GCV9a8JaCqUcFuTXV5tIXJlzZWv4SRIG5FQyap8cEadco6ObQXoD/dCLDmljmtkzmvVBEiT+SQMTw1CCke79/gh6B0/xNOiLtAgLfX9OBCaFFOgfpCQJLKpThMswIW+FVt96jiVidDZ6urApX8l5roR3SA3qqSucTdYTuVSBniKBCWau3mbkLDqUPQYPgs4bdScH02EYd/wp/x8+KpqeCAkMqovTBId8S9XNAH8VeTW1Kz5I+EnkVctyu31t28s4vySsFJz5VjdbBBS11ixo1Iy8q4wKWQhlpmC0VjYfEgVmTg+2PvDe7mNeBBfnNDmPlW/MqASJZ4dqK3ulv30RyIF3yTSXdG9e4V/xVYFG5VOxcmBGh3qiBTByAgKUB0NiQi2KYvIwGQ/PuhComTVobyQgZGpYbaFhJCSPiUn1RHReCjd2nDHU7gj4z/pkRhESO5tum+9rWhLS1TodktSzoUQEVFkGJSAJkB0HSFyeSI5DhPT41zWJISUNYkPTUL8sqX6EeBMTGl3xYIPrqq56iUFm6WECL0cb2247RcEXOYorkAWx9qhAZ5sUgWKwaiIYA0MjB/lenqwS8FTEuJyP/9KbrH5HBhz8kiYqIyLa+aBlgd/gO8lebUrKSFC8u2Gu59aVLn4H5o9qTl30Sk71wQk6VFlYDa+AqNTIzCF3xYcAY7IzGgY96j7KdGAcU79aOU+ZWDXNa17eLZ39l4F15AZRHBtzv247Se3+p2BIQ1aOzMjoJKyBZjk1JYiMDBOz4aaTvgsSBsCrWxSLstAWG0ZONWH6pf0a4Gvv3TDrBufU1BLZAYRkjpX3dDGzo3XeWzeCXaiCAgZsqQDAxyqBpLDqTU0OWBsM5gMR8T6jEh7gwD7K00EXPdNuqRq6TuPtD5iHMiVyyn/YnUguX/l40cffyuRS9TrYxtWPrqRQwPaUdHZF+2q6Lu9e/ZCONT7BW9rzA8hU+SVK0ptaOrykorThlSmkCwwOhJLqs7f8UT7T2840d9FtJz2b4jH0sfmP9b76Nax3NicExHhbaEm4nBBjS8I0WiESbDitwaJ7sckghatjkIDidAvRUATIjsHV9Rc8aeHWh7+HvadZQcnkdMSIUnkE4FnBp95YdfU+zcxBX2Eo5WOZrjega2FgPnFbYpsgUjle4Yo8Q5CEWEqiojN5kiuC61bv7Z27Wa5+9RyRkS0vBN5584Xhn/3y2h+KkSgCT6RopwVR59yK42ZERESZDF0JMCE2KYpVYBFFeftvK/lvh92eDpO+sfPcjkrIiSJQsL/8tjLG96aePNe3AzWUGRMIkLDJHKyiFCfBB+fEYyAJtLmad97W/1tT14euOJVuePM5ayJaJlGQlsntn5/x+SOu/rSfcs4DoqInl6sKiIk1JdVKSL2oj290r/y7TXB636/yrf6TdX0rOUrE7FKf7p/we74R2v2JPZceWT68AWjubF2TadcXOBKNXmbv1xUuWgXrkY7V1Sv2O5z+E77PxtOJ+eESLngC7FiMjfZOJINy9+iUejIJugMjtS7Go6pqnMoAP8FUwtU6wEgXS8AAAAASUVORK5CYII=';
+image.src = 'data:image/png;base64,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';
 export default image;
\ No newline at end of file
diff --git a/js/photons/view/PhotonSprites.ts b/js/photons/view/PhotonSprites.ts
index 4b2bdbd..1b2bb00 100644
--- a/js/photons/view/PhotonSprites.ts
+++ b/js/photons/view/PhotonSprites.ts
@@ -28,7 +28,7 @@ import Photon from '../model/Photon.js';
 // constants
 const TARGET_PHOTON_VIEW_WIDTH = 10; // in screen coords, empirically determined to match the design
 
-export default class PhotonSprites extends Sprites {
+class PhotonSprites extends Sprites {
 
   private readonly spriteInstances: SpriteInstance[];
   private readonly photons: Photon[];
@@ -74,7 +74,7 @@ export default class PhotonSprites extends Sprites {
     // canvas.  That is an asynchronous process, so we need to wait for it to complete before adding the sprites.
     const outlineCircle = new Circle( TARGET_PHOTON_VIEW_WIDTH / 2, {
       stroke: QuantumMeasurementColors.photonBaseColorProperty.value,
-      lineWidth: 0.5
+      lineWidth: 1
     } );
     outlineCircle.toCanvas( canvas => {
       this.photonOutlineSprite = new Sprite( new SpriteImage(
@@ -138,10 +138,11 @@ export default class PhotonSprites extends Sprites {
           interiorSpriteInstance.matrix.setToAffine( scale, 0, xPos, 0, scale, yPos );
           interiorSpriteInstance.alpha = photonMotionState.probability; // Probability based opacity
 
-          // Update the matrix for the photon outline.  The outline is always fully opaque.
+          // Update the matrix for the photon outline.
           const outlineSpriteInstance = this.spriteInstances[ ( numberOfPhotonsDisplayed - 1 ) * 2 + 1 ];
           outlineSpriteInstance.sprite = this.photonOutlineSprite;
           outlineSpriteInstance.matrix.setToAffine( 1, 0, xPos, 0, 1, yPos );
+          outlineSpriteInstance.alpha = 1; // Always fully opaque
         }
       }
     }
@@ -157,4 +158,6 @@ export default class PhotonSprites extends Sprites {
   }
 }
 
-quantumMeasurement.register( 'PhotonSprites', PhotonSprites );
\ No newline at end of file
+quantumMeasurement.register( 'PhotonSprites', PhotonSprites );
+
+export default PhotonSprites;
\ No newline at end of file