Cryogenic and Superconductive Techniques Laboratory

It’s convenient to explain principles of operation of the system with the help of Fig. 2. As described above, Compressor has three adsorbers. During the operation, each adsorber can be in one of two working states: cooling or heating. During the cooling, adsorber is freezed by liquid nitrogen that is circulating in a spiral heat exchanger. Speed of the cooling is controlled by a flow of gaseous nitrogen through the heat exchanger. The flow is induced by a small extra pressure of nitrogen in a liquid nitrogen reservoir which is placed in the center of compressor block (see photo in Fig. 4). The flow rate is controlled by mass-flow controllers MFC1-3. Output of spiral heaters and, respectively, speed of the heating is controlled by a pulse-width modulation method.

“Dirty” (contaminated) hydrogen from TPC flows through the first adsorber of Filter into an adsorber of Compressor that currently is in the cooling state. This process continues till the maximum possible saturation of adsorbent. Then, the cooling stops. Corresponding mass-flow controller closes the nitrogen flow and the heating begins. The cooling and the heating in the second and the third adsorbers proceeds simultaneously according to diagram (fig. 8).

Fig. 8. Compressor working cyclogram.

Direction of hydrogen flow is defined by check valves. System is equipped by the electro-pneumatic valves SV1-3 to cut-off the detector from the system. SV-2 valve is used as a bypass in this case. Hydrogen flow rate is controlled by the mass-flow controller MFC4 with respect to pressure reading of manometer PT1.