Bio-Rad PDS-1000 / He™ and Hepta™ Systems - Manual (Page 33)

Fig. 4.13. View of spent rupture disk within the retaining cap.
4.3 Removal of Residual Helium Pressure—Shut Down
After completing all bombardment(s), remove the helium pressure from the PDS-1000/He
system and close the helium cylinder valve. Perform the following steps to remove helium
pressure from the system.
1. Close the helium cylinder valve and chamber door.
2. With at least 5 inches of Hg of vacuum in bombardment chamber, remove residual line
pressure from the regulator, solenoid and PEEK tubing by activating the FIRE button.
3. Release the FIRE button on the apparatus, and remove all tension on the pressure adjust-
ment screw of the helium regulator, turning counter-clockwise, until it turns freely.
4. Vent any residual vacuum from the bombardment chamber by setting the vacuum switch
to the VENT position.
Section 5
Selection and Adjustment of
System Bombardment Parameters
5.1 Overview—Matrix of Variables
Factors affecting bombardment efficiency are numerous, and interact in complex ways.
All possible variables cannot be addressed in a single large factorial experiment. Instead, most
users will find it sufficient to prioritize variables by the magnitude of their effects, optimizing
them individually, and then testing their interactions on a more limited scale. Table 5.1 shows
some examples of conditions used in published protocols for a variety of target materials.
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