700 MPa HP Stick Controllers
The 700 MPa liquid pressure stick controllers prevent the fluids injected into 700 MPa pressure cells at cryogenic temperatures from freezing inside cryostats. In most cases, the required sample temperature is greater than 100 K and the controller maintains the high-pressure capillary at 295 K and surrounded by an insulating vacuum of ≈10−6 mbar. To reach lower temperatures, the controller stops heating the capillary and fills the annular space of the stick with ≈20 cc of exchange gas. The base temperature of ≈1.8 K can then be reached in all cryostats.
When such a controller is used on an instrument, NOMAD sends sample temperature setpoints to this controller, which decides how best to proceed. It decides automatically whether it should evacuate or inject exchange gas in the annular space of the high-pressure capilary. Then, when conditions are appropriate, it requests sample temperature changes to the LakeShore temperature controller.
The operating mode is described in the article entitled "700 MPa sample stick for studying liquid samples or solid-gas reactions down to 1.8 K and up to 550 K", J. of Neutron Research 19 (2017) 77-84 — doi:10.3233/JNR-170044. The controller comes with a Magelis LCD Touch Panel HMI-S5T and a set of pumps, valves, He buffer and pressure sensors operated by a Schneider M251 logic controller.
PLC Registers (Schneider M251 Logic Controller)
|Cryostat regulation temperature (K)||X||40 001|
|Cryostat temperature setpoint (K)||X||X||40 003|
|High-pressure capillary temperature setpoint (K)||X||40 005|
|Vacuum pressure (hPa)||X||40 007|
|Sample temperature (K)||X||40 009|
|Equipment status — Idle bit||X||40 551.0|
|Equipment status — Running bit||X||40 551.1|
|Equipment status — Local/Remote bit||X||X||40 551.2|
|Equipment status — Fault bit||X||40 551.3|
|NOMAD flag||X||X||40 011.0|
|NOMAD tolerance range||X||X||40 553|