Model OC 16-03
The continuous flow liquid helium (LHe) optical cryostat is designed for optical and magneto-optical investigations at cryogenic temperatures.
- Outer flat neck width (sample operation zone) of 16 mm (smallest among commercially available designs)
- Vertical sample position
- Samples size of up to 7 by 12 mm2
- Two UV- transparent fused quartz optical windows (or custom ordered)
- Windows transparency spectral range: 206 to 900 nm
- Window size: 10x17 mm2
- Angle between incident and reflected beams: 140°
- Operational temperature range: 5 K to 300 K
- Liquid helium consumption 0.2 to 1 liter per hour
- Sample stage 25 Ohm bifilar wound wire heater
- Temperature stability, defined the thermal controller and sensors used, but not worse than ±0.1 K
- Overall dimensions (approx.): 60 mm outer diameter, 500 mm length
- Mounting sites for temperature sensors and twisted-pair wiring
Overview of Components and Function
The continuous flow liquid helium (LHe) optical cryostat operates at temperatures ranging from 5 to 300 K. and maintains the sample-under-test in vacuum conditions. The temperature is regulated roughly by changing LHe flow rate and is adjusted finely by electrically heating the sample stage. The exact figures of the temperature-keeping accuracy depend mainly on the customer-supplied LHe transfer line (tube), temperature sensors and thermal controller. Anyway, the cryostat inner design ensures the temperature stability of not worse than ±0.1 K. The proper design including inner radiation shields results in low liquid helium consumption ranging from 0.2 to 1 liter of LHe per hour at 200 K and 10 K, respectively.
The two quartz windows located in the cryostat tip allow optical experiments in reflected and transmission light, both visible and UV. The cryostat is especially suitable for the measurements in high magnetic fields due to small outer size of its operational tip where the sample is situated. The tip is rectangular in its cross-section with the smallest dimensions among the most known commercially available optical cryostats from other manufacturers.
Easy removable vacuum jacket (attached with standard 55 mm-diameter clamp vacuum sealing) covers the copper radiation shield with removable tip head part which opens the access to the sample mounting zone. The sample-under-test is mounted onto the copper cold finger by gluing or with an additional user-made adapter. There are two provision tapped holes (M2) on the copper sample mount for this sake. Also, the hole is provided in the copper cold finger body to mount thermal sensors.
The working position of the cryostat is normally horizontal.
The cryostat is attached to a vacuum line (turbo pump is recommended, pressure of 10-4 – 10-5 Torr must be guaranteed) via evacuation port of internal vacuum valve with 40 mm-dia standard flange and clamp. The LHe commercial transfer line (tube) (9.5 to 10 mm in diameter and 500 mm or more in length) is inserted into the siphon arm and is fixed with coupling seal nut. The gas He vent line is attached to the cryostat via 40 mm-dia standard flange and clamp.
The 10-pin electrical feedthrough is provided to connect the temperature sensors and the heater inside the cryostat to an external circuit like a thermal controller. All the wiring inside the cryostat is made as the unshielded twisted pairs to exclude the electromagnetic interference.
The details of the cryostat specifications may be customized by order.
B.I. Verkin Institute for Low Temperature Physics and Engineering of NAS Ukraine
47 Nauky Ave., Kharkiv, 61103 , UKRAINE Tel: +(380)-57-340-22-23 Fax: +(380)-57-340-33-70