Position racks in the upper and lower thirds of the oven and preheat to 350°. In a medium bowl, break up the tuna with a fork and stir in the celery, jalapeños, mayonnaise and lemon juice.
Line 2 rimmed baking sheets with parchment paper. Arrange the potato chips on the prepared pans, sprinkle the cheese on top and bake until melted, 2 to 3 minutes. Dot the chips with the tuna salad; season with the chili powder.