The experiment entailed measuring interactions between high energy electrons and 3Helium gas (3He is an isotope of Helium gas with two protons and one neutron). The gas is pumped into the glass cell. The electrons enter and exit the cell through two 2 mil (1/500 of an inch) thick windows 1800 apart. The main goal is to scatter as many electrons in the gas as possible while minimizing the scattering in the glass windows. The number of electrons scattered in the glass is proportional to the glass thickness and the length of the path transversed by the electrons. Because the density of gas at one atmosphere is so much smaller than the density of glass the cell has to contain as many atmospheres as possible while the windows where the scattering will enter and exit must be as thin as possible.
Obviously these two requirements conflict with each other, since the more pressure one puts internally in the glass; the more glass is needed to prevent rupture. The other difficulty associated with these cells is the permeability of 3He through typical glass and the corrosive effects of akalai vapor metal Rb (Rubidium) at elevated temperatures that is present in the cell. The glass used for the cells have to be made from Aluminosilicate glass a rare and difficult glass to work.
The cell windows are inverted like the bottom of a champagne bottle. This is the optimum geometry for glass because the inner pressure is converted into compression. However due to this shape and its thinness, the widow thickness has to be measured by X-rays to exacting tolerances of +/- 1 micron. After the window is sealed it is pressure tested to 280 psi for a short period of time (10 minutes) before they are installed onto the cell. Moreover, every component of the cell is made from fully re-blown Aluminosilicate glass. This assures thinner walls and removes possible defects from the stock tubing.
The SLAC Cell as pictured under a Polariscope contains a pressure of nearly 150 psi and is shipped to SLAC where it's placed in the target sight and is scattered with an electron beam at a distance of 2 miles away from the cell.
A Polariscope is a device that defines pressure or stress by color When glass is subjected to unequal stress components operating on perpendicular planes, it becomes birefringent (that is, doubly refracting). The resulting birefringence of a plane-polarized light can be measured by birefringence compensators such as a quartz wedge, and from this measurement the magnitude of the stresses can be estimated. In a polariscope fitted with a tint plate, stressed glass displays colors; the distribution of these colors may also be used for recognizing stress patterns during quality-control operations.
Much of the Technology used in this project is also used to create highly magnetic gas for MRI Imaging of lungs. The cells used for this project, must also deliver high pressure gas as well as create and store them.
Currently the Glassblowing Shop is making vials for the Borexino Project ongoing at Laboratori Nazionali del Gran Sasso in Italy. These vial are made of Suprasil a synthetic quartz glass and are used to detect low energy nuetrinos. Synthetic Quartz is used due to its extreme purity and low radiation background.
