diff --git a/Tools/dea_tools/dask.py b/Tools/dea_tools/dask.py
index 226b26d1c..534a4c675 100644
--- a/Tools/dea_tools/dask.py
+++ b/Tools/dea_tools/dask.py
@@ -21,7 +21,7 @@
     create_local_dask_cluster
     create_dask_gateway_cluster
 
-Last modified: March 2020
+Last modified: June 2022
 
 '''
 
@@ -111,9 +111,22 @@ def create_dask_gateway_cluster(profile='r5_L', workers=2):
         """
         try:
             gateway = Gateway()
+            
+            # Close any existing clusters
+            cluster_names = gateway.list_clusters()
+            if len(cluster_names) > 0:
+                print("Cluster(s) still running:", cluster_names)
+                for n in cluster_names:
+                    cluster = gateway.connect(n.name)
+                    cluster.shutdown()            
+            
             options = gateway.cluster_options()
             options['profile'] = profile
-            options['jupyterhub_user'] = os.getenv('JUPYTERHUB_USER')
+
+            # limit username to alphanumeric characters
+            # kubernetes pods won't launch if labels contain anything other than [a-Z, -, _]
+            options['jupyterhub_user'] = ''.join(c if c.isalnum() else '-' for c in os.getenv('JUPYTERHUB_USER'))
+
             cluster = gateway.new_cluster(options)
             cluster.scale(workers)
             return cluster