Crystal Growth Tube Furnace

A crystal growth tube furnace incorporating a programmable motion system to “rock” the complete hot zone for long durations while maintaining temperatures up to 1300°C in an oxidizing environment.

The heated zone consists of a 50″ long mullite tube with resistance type heating elements. The hot zone contains three independent heating elements.

The complete hot zone is able to continuously rock at 90° angles and is provided for growing crystal composites.

Once the rocking heat cycle is complete, a unique quenching system will drop the crystal composites to a controlled depth in a cooling medium for quick cooling.

Specifications

General specifications:

Tubular 4″ x 28″ usable hot zone
1300°C maximum in air atmosphere
90° continuous rotation with rocking drive mechanism
Quick quench mechanism for immediate cooling
+/- 1 Deg. C uniform hot zone

Details

Chamber and Hot Zone

The chamber and hot zone consists of a 50″ long mullite tube with resistance-type heating elements. The hot zone contains three independent heating elements. A center zone of 28″ with 10″ buffer zones at each side accomplish a uniformity of +/- 1°C over the complete 28″ and is capable of maintaining a temperature of 1300°C. The hot zone chamber is mounted in a clear enclosure for safety and clean environments.

The chamber houses a muffle tube which is captivated and centered in the hot zone by means of end plugs. This muffle tube contains the medium. One end of the muffle tube is covered with a plug, the other end is a spring loaded cover that will automatically be removed when the medium is ready for quenching. A center wire runs through the center of the tube and is attached to the crystal ampule, which allows for a programmable quenching speed and distance.

Motion Control System

The complete hot zone is able to continuously rock at 90° angles and is provided for growing crystal composites. The duration, acceleration, deceleration and speed of the rocking is programmable. Rotation is accomplished by a stepping motor and planetary gearhead, allowing for highly repeatable and accurate motion patterns. Once a motion pattern is complete, the hot zone can be programmed to automatically rotate to the vertical position to quench the hot zone materials.

Quenching Mechanism

While one end of the hot zone tube is plugged, the other end houses a spring loaded ceramic cover that will open automatically when the furnace system is rotated in the vertical position for quenching (immediate cooling in a medium) of the crystal ampule. An arm will contact the furnace ceramic board and move it free of the tube so the furnace materials have free access to the quenching medium. A wire running through the middle of the tube furnace is attached to the crystal ampule and is motor driven. Thus, when the furnace is in the vertical position and the tube cover is moved, the ampule can be quenched at a pre-set speed and can be decelerated until the ampule stops at a certain depth in the quenching medium and will not hit the bottom of the quenching bucket.

The spring loaded cover will ensure a maintained seal during the rocking operation. The quenching bucket and ampule can be easily removed by means of extension slides.

Power Supply & Instruments

The power supply and instruments are mounted in 19″ rack control consoles. This houses all circuit breakers, contactors, controllers and instruments. The center console contains a writing table and storage drawers. The power supply consists of three transformers with SCR’s to control temperatures in the three independent heat zones regions. Temperature control is accomplished by a Eurotherm controller with multiple loop control and multiple ramp-soak profile storage capabilities. Motion is controlled with a two axis indexer which can be programmed and configured through the operator panel. The two axis, one for hot zone rotation, the other for quenching, are synchronized and interlocked for safe and repeatable operation. Numerous other provisions are made to ensure safe and correct operation such as quenching level detection, limit switches on tube cover, stepping motor home switch, etc.

PC System

The provided PC system allows for data acquisition of process readings and is capable of configuring the control instruments. A full HMI system is available as well.