In large saucepan, melt butter; sauté onion and celery until tender (about 5 min.). Whisk in flour, stirring 1 min. Gradually add chicken broth and bring to a boil, stirring until slightly thickened. Stir in half-and-half, artichokes, carrots and salt; simmer about 15 min., stirring occasionally. Stir in sherry and tarragon.