diff --git a/js/spin/model/ParticleSourceModel.ts b/js/spin/model/ParticleSourceModel.ts
index 8ba89a6..cfe2fa6 100644
--- a/js/spin/model/ParticleSourceModel.ts
+++ b/js/spin/model/ParticleSourceModel.ts
@@ -50,20 +50,19 @@ export default class ParticleSourceModel {
     this.sourceModeProperty = new Property<SourceMode>( SourceMode.SINGLE, {
       tandem: tandem.createTandem( 'sourceModeProperty' ),
       phetioValueType: EnumerationIO( SourceMode ),
-      validValues: SourceMode.enumeration.values
+      validValues: SourceMode.enumeration.values,
+      phetioFeatured: true
     } );
 
     this.isContinuousModeProperty = new DerivedProperty( [ this.sourceModeProperty ], sourceMode => sourceMode === SourceMode.CONTINUOUS );
 
     this.particleAmountProperty = new NumberProperty( 0.1, {
       tandem: tandem.createTandem( 'particleAmountProperty' ),
-      range: new Range( 0, 1 )
+      range: new Range( 0, 1 ),
+      phetioFeatured: true
     } );
 
-    this.positionProperty = new Vector2Property( position, {
-      tandem: tandem.createTandem( 'positionProperty' ),
-      phetioReadOnly: true
-    } );
+    this.positionProperty = new Vector2Property( position );
 
     this.exitLocalPosition = new Vector2( 0, 0 );
 
@@ -75,7 +74,8 @@ export default class ParticleSourceModel {
     this.spinStateProperty = new Property<SpinDirection>( initialSpinState, {
       tandem: tandem.createTandem( 'spinStateProperty' ),
       phetioValueType: EnumerationIO( SpinDirection ),
-      validValues: SpinDirection.enumeration.values
+      validValues: SpinDirection.enumeration.values,
+      phetioFeatured: true
     } );
 
     this.customSpinStateProperty = new Vector2Property( SpinDirection.spinToVector( initialSpinState ) );
diff --git a/js/spin/model/SpinModel.ts b/js/spin/model/SpinModel.ts
index 08247fa..33bd717 100644
--- a/js/spin/model/SpinModel.ts
+++ b/js/spin/model/SpinModel.ts
@@ -80,7 +80,8 @@ export default class SpinModel implements TModel {
     this.currentExperimentProperty = new Property<SpinExperiment>( SpinExperiment.EXPERIMENT_1, {
       tandem: providedOptions.tandem.createTandem( 'currentExperimentProperty' ),
       phetioValueType: EnumerationIO( SpinExperiment ),
-      validValues: SpinExperiment.enumeration.values
+      validValues: SpinExperiment.enumeration.values,
+      phetioFeatured: true
     } );
     this.isCustomExperimentProperty = new DerivedProperty(
       [ this.currentExperimentProperty ],
@@ -114,7 +115,7 @@ export default class SpinModel implements TModel {
     // This is needed for the number sliders to work properly.
     this.downProbabilityProperty = new NumberProperty( 1 - this.upProbabilityProperty.value );
 
-    const sternGerlachsTandem = providedOptions.tandem.createTandem( 'SternGerlachs' );
+    const sternGerlachsTandem = providedOptions.tandem.createTandem( 'sternGerlachs' );
     this.sternGerlachs = [
       new SternGerlach( new Vector2( 0.8, 0 ), true, sternGerlachsTandem.createTandem( 'firstSternGerlach' ) ),
       new SternGerlach( new Vector2( 2, 0.3 ), false, sternGerlachsTandem.createTandem( 'secondSternGerlach' ) ),
@@ -142,13 +143,6 @@ export default class SpinModel implements TModel {
       )
     ];
 
-    // Find the first inactive single particle and activate it
-    this.particleSourceModel.currentlyShootingParticlesProperty.link( shooting => {
-      if ( shooting ) {
-        this.particleSystem.shootSingleParticle();
-      }
-    } );
-
     this.expectedPercentageVisibleProperty = new BooleanProperty( false, {
       tandem: providedOptions.tandem.createTandem( 'expectedPercentageVisibleProperty' )
     } );
diff --git a/js/spin/view/ParticleSourceNode.ts b/js/spin/view/ParticleSourceNode.ts
index 5e7a850..ed52fd5 100644
--- a/js/spin/view/ParticleSourceNode.ts
+++ b/js/spin/view/ParticleSourceNode.ts
@@ -7,6 +7,7 @@
  * @author Agustín Vallejo
  */
 
+import BooleanProperty from '../../../../axon/js/BooleanProperty.js';
 import DerivedProperty from '../../../../axon/js/DerivedProperty.js';
 import Dimension2 from '../../../../dot/js/Dimension2.js';
 import { Shape } from '../../../../kite/js/imports.js';
@@ -21,6 +22,7 @@ import QuantumMeasurementColors from '../../common/QuantumMeasurementColors.js';
 import quantumMeasurement from '../../quantumMeasurement.js';
 import QuantumMeasurementStrings from '../../QuantumMeasurementStrings.js';
 import ParticleSourceModel from '../model/ParticleSourceModel.js';
+import { ParticleSystem } from '../model/ParticleSystem.js';
 import { SourceMode } from '../model/SourceMode.js';
 import HBarOverTwoNode from './HBarOverTwoNode.js';
 
@@ -30,6 +32,7 @@ export default class ParticleSourceNode extends Node {
 
   public constructor(
     particleSourceModel: ParticleSourceModel,
+    particleSystem: ParticleSystem,
     modelViewTransform: ModelViewTransform2,
     tandem: Tandem ) {
 
@@ -65,9 +68,11 @@ export default class ParticleSourceNode extends Node {
     particleSourceBarrel.rotateAround( particleSourceBarrel.center, Math.PI / 4 );
     particleSourceBarrel.center.y = particleSourceRectangle.center.y;
 
+    const currentlyShootingParticlesProperty = new BooleanProperty( false );
+
     // Button for 'single' mode
     const shootParticleButton = new RoundMomentaryButton<boolean>(
-      particleSourceModel.currentlyShootingParticlesProperty, false, true, {
+      currentlyShootingParticlesProperty, false, true, {
         scale: 0.7,
         baseColor: QuantumMeasurementColors.downColorProperty,
         visibleProperty: DerivedProperty.not( particleSourceModel.isContinuousModeProperty ),
@@ -75,6 +80,12 @@ export default class ParticleSourceNode extends Node {
         tandem: tandem.createTandem( 'shootParticleButton' )
       } );
 
+    currentlyShootingParticlesProperty.link( shooting => {
+      if ( shooting ) {
+        particleSystem.shootSingleParticle();
+      }
+    } );
+
     // Slider for 'continuous' mode
     const sliderRange = particleSourceModel.particleAmountProperty.range;
     const particleAmountSlider = new HSlider( particleSourceModel.particleAmountProperty, sliderRange, {
diff --git a/js/spin/view/SpinMeasurementArea.ts b/js/spin/view/SpinMeasurementArea.ts
index 1a2a544..1e04562 100644
--- a/js/spin/view/SpinMeasurementArea.ts
+++ b/js/spin/view/SpinMeasurementArea.ts
@@ -62,7 +62,12 @@ export default class SpinMeasurementArea extends VBox {
       180 // empirically determined
     );
 
-    const particleSourceNode = new ParticleSourceNode( model.particleSourceModel, modelViewTransform, tandem.createTandem( 'particleSourceNode' ) );
+    const particleSourceNode = new ParticleSourceNode(
+      model.particleSourceModel,
+      model.particleSystem,
+      modelViewTransform,
+      tandem.createTandem( 'particleSourceNode' )
+    );
 
     const sternGerlachNodes = [
       new SternGerlachNode(