An EUV radiation source that includes a fuel supply configured to supply fuel to a plasma formation location. The fuel supply includes a reservoir configured to hold fuel at a temperature that is sufficiently high to maintain the fuel in liquid form, and a pressure vessel configured to contain the reservoir, the pressure vessel being at least partially thermally isolated from the reservoir. The EUV radiation source also includes a laser radiation source configured to irradiate fuel supplied by the fuel supply at the plasma formation location.