Two low-cost, modular sub-λ test cryostats

Abstract

Abstract. Two general-purpose liquid helium (LHe) test cryostats have been developed in support of a major upgrade to the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). The cryostats are capable of sustained operation below 1.8 K and currently support tests of prototype superconducting rf (srf) cavities for the APS Upgrade's Short Pulse X-ray (SPX) initiative. To save cost, two existing test vessels were reconditioned: one "bucket dewar" supporting bare cavity tests and one shielded vacuum vessel with an integral LHe reservoir for jacketed/dressed cavity tests. A new feedbox containing a heat exchanger and associated valves was also designed and fabricated to support either cryostat. The resulting modular design permits tests on a wide variety of srf cavities in various states of completion, minimizing cost and maximizing use of the hardware. Together with a dedicated vacuum pump, control system, and helium supply via storage dewar or cryoplant, these cryostats are vital to the srf cavity development effort within the APS Upgrade.