Stinger closed cycle cryostat

Overview

On the measurement manipulators of both endstations, Bloch is using a ‘Stinger’ closed cycle helium cryostat. A schematic overview of the system is shown below:

There are two separate He gas loops, shown here as orange and green.

The first loop (orange) uses an F70L/H compressor (in the cupboard, lower level) to feed a Gifford-McMahon (GM) cryocooler in the Stinger ‘blue can’ mounted up on the platform. The GM cooler takes 300psi helium as input, expands it for cooling power then returns low pressure He. It cools two heat exchange surfaces within the blue can as ‘output’ - a first stage at 20K (16W capacity) and a second stage at approx 4K (1.25W capacity). This helium loop is never vented or refilled.

The second, totally isolated He circuit is powered by the HC-4E1 compressor (in the cupboard, upper level). It sends high pressure room temperature helium into the blue can. It is first pre-cooled by returning gas from this same circuit. It then passes through the heat exchangers of the GM cooler, before travelling through the flexible insert and undergoing a final Joule-Thomson (JT) expansion close to the tip of the cryostat insert. Exhaust gas is sent back up the flexible line into the blue can, then returned to the compressor for the cycle to repeat. An important advantage of this configuration is the decoupling of vibrations from the GM cryocooler from the cryostat.

The image below illustrates the gas flow within the cryostat:

Cold gas flows through the insert, with the JT expansion happening in a capillary inside the end of the insert. In our case this capillary has an inner diameter of about 480μm. The teflon gasket seal further up the insert is responsible isolating the outlet and return lines.

Technical details

A Branch	Manufacturer	Part number	Serial number
Stinger system	Coldedge		9191399-0133
Recirculator compressor	Sumitomo	HC-4E1	???
Cryocooler compressor	Sumitomo	F-70	FN02561
Cryocooler	Sumitomo	RDE-412D4	38D19058A

A Branch	Manufacturer	Part number	Serial number
Stinger system	Coldedge		9191399-0132
Recirculator compressor	Sumitomo	HC-4E1	???
Cryocooler compressor	Sumitomo	F-70	FN02560
Cryocooler	Sumitomo	RDE-412D4	38D19059A

Standard parameters
Manifold pressure	80-100 PSI
F70 pressure (idle)	190 PSI
F70 pressure (running)	270 PSI
HC-4E1 pressure	80-100 PSI
He gas flow (cold)	14 L/min
He gas flow (warm)	0.7 L/min

We have an inline Omega FMA1824A flowmeter measuring the He return flow from the cryostat. It is N2 calibrated and rated for 0-20L/min. The conversion factor for He flow is 1.45.