Adding tandem to the particles, see #63

js/spin/model/ParticleSystem.ts

@@ -9,6 +9,7 @@
 
 import dotRandom from '../../../../dot/js/dotRandom.js';
 import Vector2 from '../../../../dot/js/Vector2.js';
+import Tandem from '../../../../tandem/js/Tandem.js';
 import quantumMeasurement from '../../quantumMeasurement.js';
 import { BlockingMode } from './BlockingMode.js';
 import { ParticleWithSpin } from './ParticleWithSpin.js';
@@ -37,18 +38,23 @@ export class ParticleSystem {
   private fractionalEmissionAccumulator = 0;
 
   public constructor(
-    model: SpinModel
+    model: SpinModel,
+    tandem: Tandem
   ) {
 
     this.model = model;
 
     // Create all particles that will be used in the experiment.  It works better for phet-io if these are created at
     // construction time and activated and deactivated as needed, rather than creating and destroying them.
-    this.singleParticles = _.times( MAX_NUMBER_OF_SINGLE_PARTICLES, () => {
-      return new ParticleWithSpin( Vector2.ZERO );
+    const singleParticlesTandem = tandem.createTandem( 'singleParticles' );
+    const multipleParticlesTandem = tandem.createTandem( 'multipleParticles' );
+    this.singleParticles = _.times( MAX_NUMBER_OF_SINGLE_PARTICLES, index => {
+      const particleTandem = singleParticlesTandem.createTandem( 'particle' + index );
+      return new ParticleWithSpin( Vector2.ZERO, particleTandem );
     } );
-    this.multipleParticles = _.times( MAX_NUMBER_OF_MULTIPLE_PARTICLES, () => {
-      return new ParticleWithSpin( new Vector2( PARTICLE_RAY_WIDTH * ( dotRandom.nextDouble() * 2 - 1 ), PARTICLE_RAY_WIDTH * ( dotRandom.nextDouble() * 2 - 1 ) ) );
+    this.multipleParticles = _.times( MAX_NUMBER_OF_MULTIPLE_PARTICLES, index => {
+      const particleTandem = multipleParticlesTandem.createTandem( 'particle' + index );
+      return new ParticleWithSpin( new Vector2( PARTICLE_RAY_WIDTH * ( dotRandom.nextDouble() * 2 - 1 ), PARTICLE_RAY_WIDTH * ( dotRandom.nextDouble() * 2 - 1 ) ), particleTandem );
     } );
 
   }

js/spin/model/ParticleWithSpin.ts

@@ -10,6 +10,7 @@
 import BooleanProperty from '../../../../axon/js/BooleanProperty.js';
 import Vector2 from '../../../../dot/js/Vector2.js';
 import Vector2Property from '../../../../dot/js/Vector2Property.js';
+import Tandem from '../../../../tandem/js/Tandem.js';
 import quantumMeasurement from '../../quantumMeasurement.js';
 
 export class ParticleWithSpin {
@@ -34,10 +35,16 @@ export class ParticleWithSpin {
   public velocityProperty: Vector2Property;
   public speed = 1;
 
-  public constructor( private readonly offset: Vector2 ) {
-    this.activeProperty = new BooleanProperty( false );
-    this.positionProperty = new Vector2Property( Vector2.ZERO );
-    this.velocityProperty = new Vector2Property( Vector2.ZERO );
+  public constructor( private readonly offset: Vector2, tandem: Tandem ) {
+    this.activeProperty = new BooleanProperty( false, {
+      tandem: tandem.createTandem( 'activeProperty' )
+    } );
+    this.positionProperty = new Vector2Property( Vector2.ZERO, {
+      tandem: tandem.createTandem( 'positionProperty' )
+    } );
+    this.velocityProperty = new Vector2Property( Vector2.ZERO, {
+      tandem: tandem.createTandem( 'velocityProperty' )
+    } );
 
     this.startPosition = Vector2.ZERO;
     this.endPosition = new Vector2( 1, 0 );

js/spin/model/SpinModel.ts

@@ -89,7 +89,7 @@ export default class SpinModel implements TModel {
 
     this.particleSourceModel = new ParticleSourceModel( new Vector2( -0.5, 0 ), providedOptions.tandem.createTandem( 'particleSourceModel' ) );
 
-    this.particleSystem = new ParticleSystem( this );
+    this.particleSystem = new ParticleSystem( this, providedOptions.tandem );
 
     this.derivedSpinStateProperty = new DerivedProperty(
       [