Experimental Quartz Chamber:

Manufactured by
PRECISION GLASS PRODUCTS CO.
for NASA;

features working quartz piston and cylinder

The above photograph clearly demonstrates Precision Glass Products' unique manufacturing capabilities. This remarkable device, produced in small quantities under contract to NASA, requires a high level of expertise in several quartz (or glass) fabrication technologies:

• Precision grinding of part geometry to ±0.0001.
• Assembly of individual quartz parts by fusion bonding with no loss of accuracy.
• Hermetic encapsulation of a metal core within a quartz cylinder.

The quartz chamber was produced for microgravity research experiments being conducted by NASA. Dubbed the Isothermal Dendritic Growth Experiment, or IDGE, these chambers are to be used to observe and record dendritic growth in materials under weightless conditions (aboard the space shuttle.) More information concerning IDGE can be obtained at http://www.rpi.edu/locker/56/000756. An E-mail address is also available at IDGE@rpi.edu.

The chamber, constructed from 15 separately generated synthetic quartz components (and one metal piece), has many unusual features. The large main housing is precision ground from a single piece of high grade material and then optically polished on several of its exterior as well as interior surfaces. Four holes are bored through the housing and honed to a high degree of accuracy and finish. These are used to provide access to the interior for the following four attachments:

1. Thermistor. A closed tube, open to the outside only, accepts a thermistor probe used to monitor the temperature of materials inside the chamber.
2. Stinger. Another precision tube which has one end finely ground to a sharp angled point. This tube is closed to the outside. Dendritic growth begins at the tip of the stinger tube.
3. Fill Tube. A quartz tube bent to a 90 degree angle and constricted to an hour-glass shape at one point. This tube is used to evacuate the chanber and to fill it with test material. It is then thermally closed off at the point of the constriction.
4. Pump. The pump is by far the most complex of the four attachments and is actually an operating piston and cylinder manufactured from 6 separate pieces of synthetic quartz. A metal core is encapsulated under a vacuum process within the quartz and this, after precision cylindrical grinding and lapping to an 8 microinch finish, becomes the piston. The metal core is required so that the pump can be electromagnetically driven. The cylinder for the piston is honed on its internal diameter to produce a uniform gap around the piston. Gaps from 0.0004 to 0.0012 inches ±0.0002 inches have been manufactured. Finally a fill tube and cylinder head are thermally bonded to one open end of the cylinder.

The four attachments are then thermally bonded to the main housing of the chamber. These bonds are accomplished under rigidly controlled conditions of heat and pressure and result in virtually no loss of optical properties or deformation of part geometry. After fine annealing, the final product is essentially a single piece of quartz. Optical windows are then frit bonded to the remaining open sides of the chamber.

For more information, please do not hesitate to contact Precision Glass Products Company at our phone, fax, or e-mail sites. Our technicians are always available to discuss your requirements.

Related Links

RPI-NASA IDGE Home Page

Microgravity Science Division Home Page

NASA Lewis Research Center Home Page

Download (ZIP) or view (PDF) NASA article featuring this product and the microgravity dendritic growth experiment.
Note: Document is in Adobe Acrobat (PDF) format. If you do not have the Acrobat viewer, click here to get it from the Adobe site.