diff --git a/pymosa/noise_occupancy_scan.py b/pymosa/noise_occupancy_scan.py
index d76c815..780c399 100644
--- a/pymosa/noise_occupancy_scan.py
+++ b/pymosa/noise_occupancy_scan.py
@@ -85,7 +85,7 @@ def scan(self):
             for region in range(4):
                 self.fake_hit_rate_meas[plane, region] = self.hit_occ_map[m26_regions[region][0]:m26_regions[region][1], :, plane].sum() / 576. / 288. / self.scan_timeout / 1e6 * 115.2
 
-        self.hist_occ.stop.set()  # stop analysis process
+        self.hist_occ.close()  # stop analysis process
 
         # Log status (fake hit rate, noise occupoancy, threshold setting)
         self.print_log_status()
diff --git a/pymosa/online.py b/pymosa/online.py
index a312ffa..45671c9 100644
--- a/pymosa/online.py
+++ b/pymosa/online.py
@@ -330,11 +330,26 @@ def worker(self, raw_data_queue, shared_array_base, lock, stop):
             except queue.Empty:
                 continue
 
-    def __del__(self):
+    def close(self):
+        ''' Close process and wait till done. Likely needed to give access to pytable file handle.'''
+        logger.info('Stopping process %d', self.p.pid)
         self._raw_data_queue.close()
         self._raw_data_queue.join_thread()  # Needed otherwise IOError: [Errno 232] The pipe is being closed
         self.stop.set()
         self.p.join()
+        del self.p  # explicit delete required to free memory
+        self.p = None
+
+    def __del__(self):
+        if self.p and self.p.is_alive():
+            logger.warning('Process still running. Was close() called?')
+            self.close()
+
+    # def __del__(self):
+    #     self._raw_data_queue.close()
+    #     self._raw_data_queue.join_thread()  # Needed otherwise IOError: [Errno 232] The pipe is being closed
+    #     self.stop.set()
+    #     self.p.join()
 
 
 if __name__ == "__main__":