The ARS manufactured LT3B Helitran® is a true UHV cold head (10-11 Torr) where all of the rubber o-ring seals have been replaced with welded joints and metal seals.
Like all of our LT3 liquid helium flow cryostats, the LT3B is an advanced liquid helium flow cryostat utilizing many unique features, such as the matrix heat exchanger and the co-axial shield flow transfer line, to achieve unparalleled efficiency and ultra low vibration levels.
The combination of true UHV and angstrom level vibrations makes the LT3B ideal for low temperature STM applications.
For UHV surface science where very long cold fingers are required, we have the LT3M with customizable length up to 1200 mm and rigid support tube to allow for cleaving and manipulation.
- Surface science
- True UHV (10-11 Torr)
- Open sample space
- Optional cold tip extensions
- Liquid helium flow
- Matrix heat exchanger for high cooling efficiency
- Co-axial shield flow
- 4 K liquid helium operation (1.7 K with pumping)
- 0.7 LL/hr liquid helium consumption at 4.2 K
- Liquid nitrogen compatible (77 K operation)
- Angstrom level vibrations
- Precision flow control
- Exhaust heater
- Operation in any orientation
- Fully customizable
- Cold head (LT3B)
- Co-axial shield flow liquid helium transfer line
- True UHV welded stainless steel instrumentation skirt with 2.75 in. rotatable CF flange
- Dewar adapter
- Flow meter panel for helium flow control and optimization
- Nickel plated OFHC copper radiation shield terminating 0.125 in. short of the cold tip
- Instrumentation for temperature measurement and control:
- 10 pin UHV feedthrough
- 36 ohm thermofoil heater
- Silicon diode sensor curve matched to (± 0.5 K) for control
- Calibrated silicon diode sensor (±12 mK) with 4 in. free length for accurate sample measurement
- Wiring for electrical experiments:
- 10 pin UHV feedthrough
- 4 UHV rated copper wires
- Sample holder for optical and electrical experiments
- Temperature controller
Options and Upgrades
- High flow transfer line
- 4.5 and 6 in. rotatable CF flanges available
- 450 K high temperature interface
- 800 K high temperature interface
- Custom temperature sensor configuration (please contact our sales staff)
- Custom wiring configurations (please contact our sales staff)
- Sample holder upgrades (custom sample holders available)
The ARS Advantage
The Helitran® incorporates an extended surface tip heat exchanger (Matrix Heat Exchanger) which provides efficient heat transfer between the helium and the sample mount. The liquid helium flows through this heat exchanger and as the latent heat of vaporization cools the sample mount, the liquid evaporates. The gas continues to flow through the exchanger, providing additional cooling by capturing the enthalpy of the gas. If the flow is optimized the helium gas will exit the Matrix Heat Exchanger at a temperature equal to the sample temperature.
Without an extended surface cryostat tip heat exchanger, the consumption of helium during initial cooldown is 40 times higher from 300 K (room temperature) to 4.2 K, and 14 times higher when cooling from 77 K to 4.2 K.
Conventional helium flow cryostats utilize a capillary tube in a vacuum jacket with super insulation to reduce the radiant heat load. However as the helium absorbs radiant heat, the liquid is vaporized and forms bubbles of gas which have a larger volume than the liquid, thus forming a temporary block to the flow of the liquid. This is called “vapor binding.” At the delivery end of the transfer line this results in the liquid/gas mixture being delivered in spurts, with accompanying pressure and temperature cycling.
The coaxial flow transfer line incorporates a shield flow surrounding the tip flow for the entire length of the transfer line. The entrance to the coaxial shield flow tube is provided with a nozzle which results in a pressure and corresponding temperature drop in the shield flow. This cools the tip flow in the center tube, which prevents boiling and gas bubble formation in the helium, even at very low flow rates. The helium is delivered at the sample end with the desired temperature stability and low vibrations.
Our high temperature interfaces use a unique combination of mechanical and thermodynamic properties to create a high temperature thermal disconnect between the cold head and the sample space. This allows for heating of the sample space far in excess of the maximum 355 K temperature of our cryocoolers.
450 K The Easy Way
Our 450 K interface is a simple semi-permanent addition to the cold tip that expands the upper sample temperature range by 95 K utilizing most of the same instrumentation as our standard cryocoolers.
800 K - Pouring on the Heat
Our specially designed 800 K interface goes beyond the standard techniques to provide a unique system that maximizes thermal conduction at low temperatures while minimizing heat transfer at high temperatures. Beyond the safe operating temperature of silicon diodes, the standard sensors are replaced with E-type thermocouples and platinum RTDs.
Our technicians painstakingly wrap each cold head for optimum thermal anchoring. We offer you the choice of a variety of wiring options, from our standard offerings of single strand copper and low noise coaxial wiring packages to any number of custom wiring configurations.
Typical instrumentation for temperature measurement and control include one 36 ohm thermofoil heater, one curve matched silicon diode for rough temperature control, and one free length calibrated diode for direct attachment to the sample or sample holder for accurate temperature measurement. Silicon diode sensors are favored heavily for most standard applications because of their low cost, durability, and stability, but we do offer a wide variety of other sensors for different applications such as Cernox sensors for high magnetic fields, E-type thermocouples for 4 K-800 K measurements, and platinum RTDs for accurate high temperature measurements.
Our wide selection of wiring and instrumentation is matched by an equally wide selection of temperature controllers from Cryocon, Lake Shore, and Scientific Instruments.
Whether the measurement is optical or electrical in nature, the sample large or small, we have a sample holder for almost any measurement. The LT3B can accept all but our largest sample holders. Like all of our cold fingers, the LT3 has a 1/4-28 threaded hole on the cold tip to mount the sample holder. So even if you do not find what you need from our wide variety of sample holders there is always the option of attaching a custom sample holder.
LT3B Helitran® Specifications
|LT3||Open Cycle Cryocooler, Helitran®
|Refrigeration Type||Liquid Helium Flow|
|Liquid Cryogen Usage||Helium, Liquid Nitrogen Compatible|
|LT3B||4.2 K - 350 K ( < 2 K with pumping)|
|With 800 K Interface||(Base Temp + 2 K) - 800 K|
|With 450 K Interface||(Base Temp + 2 K) - 450 K|
|*Based on bare cold head with a closed radiation shield, and no additional sources of experimental or parasitic heat load.|
Open radiation shield
Open radiation shield
|Sample Holder Attachment||1/4-28 screw|
|Sample Holder||View our Sample Holder Collection|
|Window Material||View our Wide Selection of Window Materials|
|Temperature Instrumentation and Control (Standard)-|
|Heater||1 - 36ohm Thermofoil Heater Anchored on Cold Tip|
|Control Sensor||1 - Curve Matched Silicon Diode|
|Sample Sensor||1 - Calibrated Silicon Diode|
|Custom Instrumentation||Contact ARS for available Options|
|Instrumentation Skirt||Welded Stainless Steel|
|Instrumentation Ports||2 - 1.33 mini-CF|
|Instrumentation Wiring||Contact our sales staff for wiring options|
|Diameter||N/A (at the sample space)|
|Width||N/A (at the sample space)|
|Optical Access||Open end
Radiation shield terminates 0.125" short of cold tip (customer specified)
|Overall Length||326 mm (12.84 in)
114 mm (4.5 in) standard Flange to Tip Dimension
|Motor Housing Diameter||N/A|
|Rotational clearance||121 mm (4.8 in) with "G" configuration|
Liquid Helium Flow Cryostat Specifications
|Cryogen||Liquid helium||Liquid nitrogen|
|Base Temperature||4.2 K||< 2 K with pumping||77 K|
|Nominal Helium Consumption at 4.2 K||0.7 LL/hr|
|Cooling Capacity-||0.7 LL/hr||2 LL/hr|
|4.2 K||0.5 W||1.5 W|
|20 K||3.0 W||8.0 W|
|50 K||7 W||20 W|
|Maximum Temperature||450K with cold gas flow through transfer line|
|Cooldown Time-||4.2 K||20 min|
|Weight||0.9 kg (2 lbs)|
True UHV Liquid Helium Flow Cryostat
Click on the images for full size.
Prof. Michael F. Crommie,
University of California at Berkeley
120 x 120 angstrom image of azobenzene molecules on Au(111) taken at T = 15 K
This LT3B liquid flow cryostat for UHV and ultra-low vibration applications was customized for a home-built STM instrument. The custom flanges were designed by the customer and integrated into the final cryostat design. ARS provided 3D models of this custom system to help the customer verify the system fit-up prior to production.
LT-3B and LT-3OM
A customer recently bought these two helium flow ARS cryostats. The one on the left is a liquid helium cold cryostat for optical microscopy with adaptations for mounting and thermally anchoring a diamond anvil cell. The one on the right is a liquid helium cooled cryostat for FTIR and THZ applications featuring a 10 mm CVD diamond window, spectrometer adapter flange, and Z-translator for three sample measurement.