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LT3

  • Overview
  • Specifications
  • Drawings
  • Pictures

The LT3 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 vibration levels.

Click here to download the LT3 data sheet (PDF).

The LT3 cryocoolers are typically equipped with a stainless steel instrumentation skirt, with our unique double o-ring design that allows for easy attachment, alignment, and removal of the vacuum shroud.

For goniometer users, the LT3K was designed to integrate with the Newport Kappa Goniometer and the LT3G was designed to fit into the Huber 5012.12 cryostat mount. The small radial clearance of the LT3G also makes it ideal for many other manipulator applications.

The ARS manufactured LT3B 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. 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.

Click here to see all Advanced Research Systems flow cryostats.

Features

  • Liquid Helium Flow
  • Matrix Heat Exchanger
  • Co-axial Shield Flow
  • 4 K Liquid Helium Operation (1.7 K With Pumping)
  • 0.7 LL/hr Liquid Helium Consumption at 4.2K
  • Liquid Nitrogen Compatible (77 K Operation)
  • Angstrom Level Vibrations
  • Precision Flow Control
  • Exhaust Heater

Standard Components

  • Cold Head (LT3)
  • Co-axial Shield Flow Liquid Helium Transfer Line
  • Dewar Adapter
  • Flow Meter Panel for Helium Flow Control and Optimization

Options and Upgrades

  • 450 K High Temperature Interface
  • 800 K High Temperature Interface

The ARS Advantage

Matrix Heat Exchanger
The Matrix Heat Exchanger is Imbedded in the Cold Tip of the Helitran Flow Cryostat

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.

Co-axial Shield Flow
A Schematic Representation of the Coaxial Shield Flow Transferline

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.

High Temperature Options
800K Interface Manufactured by ARS

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.

Liquid Helium Flow Cryostat Specifications

Cryostat Model LT3
   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)

Vibration Levels

LT3-110 with standard double o-rings

LT3
Standard with Double O-Ring Interface

LT3B
True UHV with 2.75 inch Conflat Flange

LT3-OM Optical Microscopy Cryostat with Continuously Adjustable Sample Height

LT3-OM
For Optical Microscopy

LT3M with Extended Length for Manipulators and Offer True UHV Vacuum Performance.

LT3M
Support Tube and Tight Rotational Clearance

Click on the Images for full size


Courtesy of:
Prof. Steve Collins,
Beamline I16 Diamond Light Source


CS202SK-DMX-2D

4 K closed cycle cryostat installed on a Newport Kappa Goniometer for x-ray diffraction experiments. This cryostat was fitted with beryllium domes for 2 pi steradian access.
LT3K for the Newport Kappa Goniometer with Beryllium Dome Sample Compartment

LT3K for the Newport Kappa Goniometer with Beryllium Dome Sample Compartment