You need to first move the initialization, configure, and close to outside the loop. You'll probably also need to place the file write in a different loop and pass it data via a queue such as in the producer/consumer architecture (see examples and File>New...). The instrument also can do a multiple point acquisition. Lastly, you might need to use something a bit faster than a serial connection such as USB, Ethernet, or GPIB (whatever the instrument has besides serial).
