TransTemp Transparent Tube Furnace

The TransTemp transparent tube furnace was originally developed at the Lincoln Laboratory on the campus of MIT. Unlike conventional furnaces, the TransTemp becomes transparent at approximately 600°C, which makes it possible to see a process as it takes place inside the furnace. TransTemp transparent furnaces use a gold mirror that reflects infrared radation and acts as an insulator. The use of only a gold mirror for insulation minimizes mass and allows for very fast heat up and cool down rates. The maximum recommended operating temperature of the TransTemp tube furnace is 1000°C.

Construction

TransTemp tube furnaces are constructed using three coaxially mounted tubes. The outermost tube is Pyrex glass that has a gold mirror on its inner surface. Gold is highly reflective of infrared energy and acts as an insulator. Gold is also ideal for a transparent furnace because it is a poor reflector of visible light. The second tube is a quartz shield that protects the gold mirror. Coaxially mounted inside of the quartz shield is a resistive element. The element is made up of a series of fixed brazed coils. The exact temperature profile will depend on the design of the element. The third tube is a quartz tube or muffle, which extends beyond the ends of the furnace and passes through the center of the heating element.

Temperature Uniformity

In conventional tube furnaces using packed or porous insulation, the temperature is generally uniform over only the central third of the heated length. Outside this region, the temperature decreases significantly due to heat loss at the ends. In the TransTemp tube furnace, uniform reflection of infrared radiation evenly distributes the heat throughout the entire length of the tube. Because the mirror is uniform, it has uniform radial heat loss. With the ends capped, the TransTemp tube furnace will provide a uniform temperature along 60% of its length.

The table below lists some of the more common sizes that we have built in the past. If you have a custom size request, please contact us and we will work with you to meet your specific needs.

FURNACE
MODEL

A
BCDEFGHWattsVoltsControl Model
TTL-1.5-0-12-1B
6.0" 152mm
5.625" 143mm
3.0" 76mm
8.375" 213mm
9.625" 244mm
12.0" 305mm
1.5" 38mm
16.0" 406mm
1575
110
1-1-40-110-E15PK
TTL-1.5-0-20-1B
6.0" 152mm
5.625" 143mm
3.0" 76mm
8.375" 213mm
9.625" 244mm
20.0" 508mm
1.5" 38mm
24.0" 610mm
2449
110

1-1-40-110-E15PK
TTL-2.25-0-20-1B
8.0" 203mm
5.825" 148mm
3.0" 76mm
8.375" 213mm
9.625" 244mm
20.0" 508mm
2.5" 64mm
24.0" 610mm
3419
220
1-1-40-220-E15PK

Typical Heating and Cooling Rate Graph for the TransTemp Tube Furnace

The TransTemp tube furnace has a very low thermal mass, which enables it to quickly heat up to temperature and cool down rapidly. The standard 305mm model with a 37mm inside diameter muffle will reach 1000°C in less than 15 minutes and cool to 600°C in less than 15 minutes.

Typical Uniformity Graph for the TransTemp Tube Furnace

In conventional tube furnaces using packed or porous insulation, the temperature is generally uniform over only the central third of the heated length. Outside this region, the temperature decreases significantly due to heat loss at the ends. In the TransTemp tube furnace, uniform reflection of infrared radiation evenly distributes the heat throughout the entire length of the tube. Because the mirror is uniform, it has uniform radial heat loss. With the ends capped, the TransTemp tube furnace will provide a uniform temperature along 60% of its length.

  • Integrated circuit breaker
  • Single set point controller
  • (optional programmable controller)
  • Table top control cabinet
Model Number 1-1-20-110-E15PK 1-1-20-220-E15PK
Electrical Requirements 110V 220V
Amperage Rating 20 amp 40 amp
Exterior Dimensions (WxDxH) 14”x14”x6” 14”x14”x6”

Why use a transparent furnace?

Developed originally for observing crystal growth, transparent furnaces are now used by those who want to take advantage of their unique properties.

  • Visibility Unobstructed viewing of samples, thermocouple placement and process procedures.
  • Low mass Heats up quickly, and possesses a compact design.
  • Cleanliness No contamination from fiber insulating material.
  • Uniformity At least +/- 2°C over 60% of the length of the heated chamber.

How are these furnaces used?

Originally developed for growing crystals, transparent furnaces are used for Liquid Phase Epitaxy (LPE), Chemical Vapor Deposition (CVD), and ampule growth. They are also used for annealing of wafers, gold wires and superconducting wires. The TransTemp tube furnace can be used for almost any application where a convention tube furnace would be used.

What about the gold mirror as insulation? How thick is the gold film?

The average thickness of the gold film is approximately 80 nm. Viewed on a molecular level, the gold mirror would look like a series of gold islands with open spaces between islands. The heavier the film, the less space between the gold islands. The visibility into the furnace is affected by the thickness of the coating. Lighter coatings allow for better visibility into the furnace, while heavier coatings produce a more efficient but opaque furnace.

What is the external temperature of the furnace during operation?

  • Internal temperature: 300°C = External temperature : 54°C
  • Internal temperature: 419°C = External temperature : 119°C
  • Internal temperature: 630°C = External temperature : 173°C
  • Internal temperature: 814°C = External temperature : 215°C
  • Internal temperature: 1000°C = External temperature : 287°C

What is the maximum operating temperature of the TransTemp transparent tube furnace?

The recommended maximum operating temperature is 1000°C. The TransTemp will operate at higher temperatures, but the lifespan of the gold film will be greatly reduced.

The melting point of gold is 1064°C, how can the gold mirror survive?

The innermost surface of the gold film may reach the operating temperature, but most of the energy is reflected, not transferred into the film. The relatively cool air surrounding the outside of the gold tube cools the glass, which keeps the gold film below its melting point. Always keep the outside of the furnace unobstructed so that natural cooling effect can take place or the gold mirror will crack!

Can you operate the entire furnace in a vacuum?

Yes… but the outside temperature of the gold mirror must stay below 600°C.

Can the furnace be operated as a vacuum furnace?

Many of our TransTemp owners insert a quartz tube through the furnace. Process tube end seals can be used on the tube and a vacuum or positive pressure can be created inside the tube. Please ensure that the process tube is designed for the intended operation.

What is the largest furnace and the smallest furnace and mirror you have made?

  • Longest = IBM Tokyo, Japan = 57mm OD x 7926mm
  • Largest Diameter = Aichi Steel, Japan = 200mm OD x 500mm
  • Smallest = NASA, Cleveland = 23mm OD x 50mm

Mirrors:

  • Longest single section = 1500mm
  • Largest Diameter = 300mm OD
  • Smallest Diameter = 25mm OD

 

All furnaces are of the same design. Only the dimensions change.

Do you have a customer reference list?

Partial list of our U.S. customers:

  • Minnesota Mining and Manufacturing
  • Naval Electronics Laboratory Center, South Dakota
  • Naval Research Center, Washington
  • Bell Telephone
  • North American Rockwell
  • Esso Research
  • Eastman Kodak
  • United States Bureau of Standards
  • U.S. Air Force, Hanscom Field
  • U.S.A.F. – Wright Patterson Air Force Base
  • EG & G, Inc.
  • Gillette
  • Grumman
  • Rockwell International
  • Marshall Space Flight Center
  • Landseas Corporation
  • Philip Morris
  • Hewlett Packard
  • Xerox
  • University of California – Berkeley
  • University of California – Los Angeles
  • Carnegie-Mellon University
  • University of Utah
  • University of Southern California at Los Angeles
  • Purdue University
  • Massachusetts Institute of Technology
  • Polytechnic Institute at Brooklyn
  • University of Washington
  • Colorado State University
  • Harvard University
  • University of Wisconsin

Partial list of our International customers:

  • Australia University of S. Wales University of Wollongong
  • Canada Bell Northern University of Toronto
  • England Feranti, Ltd. University of Reading
  • France French Atomic Energy Commission (C.E.A.) Universite de Strasbourg
  • Germany Preussag Aktiengesellschaft Berliner Handels-Kontor Heinz Lindenberg
  • India Indian Institute – Madras
  • Iran Arya-Mehr University of Technology
  • Israel Semi Conductor Devices Rotem Industries Isreal Atomic Energy
  • Japan Dinichi Trading Company Ishikawa Trading Company
  • Netherlands Kawecki-Billiton
  • New Zealand Department of Science and Industrial Research
  • Norway Elkem Carbon Teck Industries Trondheim Industries Norsk Hydro
  • Switzerland Interac Scole Polytechnique Federal de Lausanne
  • Venezuela Instituto Venezolano de Investigaciones Cientificas