text: turning to fig1 , an exploded perspective view of a disk drive of the present invention is shown . the disk drive assembly 10 generally comprises a cover 12 and base plate 14 . the base plate has perimeter walls 16 which define an inner chamber 18 . when the cover plate is secured to the base plate , the inner chamber is filled with a low density gas such as helium to create a pressurized low density gas environment for operation of the disk drive components . the cover plate and base plate are provided with aligned apertures 20 equally spaced around the perimeter of each for securing the cover to the base plate . the apertures within the base plate are typically threaded to receive fasteners ( not shown ). additionally , it has been determined that a metal c - shaped seal 22 is more suitably adapted to maintaining the pressurized low density gas environment within the chamber 18 than a conventional rubber seal . in the preferred embodiment , the cover and base plate are secured by the fasteners with a force of 400 pounds per circumferential inch in order to maintain a seal over the intended lifetime of the disk drive . in general terms , a disk drive contains a disk stack 24 comprising one or more circular hard disks 26 . the disk stack is mounted to and rotate about a spindle shaft 28 . a disk clamp 30 secures the disk stack to the hub ( not shown ). in the embodiment shown in fig1 , the base plate further includes an interior wall 32 which is configured to closely match the perimeter edges of the hard disks to enshroud a substantial circumferential portion of the disks . this interior wall reduces air turbulence caused by the spinning of the disks during operation of the disk drives and helps reduce track misregistration . the disk drive also generally includes an actuator assembly 34 . the actuator assembly comprises an actuator arm or e block 36 . the actuator arm is mounted on an actuator shaft 38 . the actuator arm rotates about the shaft under the direction of a voice coil motor 40 . a flex circuit 42 carries signals between read / write elements 44 positioned at the end of the actuator arm and processors associated with the disk drive positioned on a printed circuit board ( not shown ) mounted underneath the base plate . a capture plate 46 is shown , in one embodiment , in fig1 , 2 and 8 - 11 . the capture plate comprises a first planar portion 48 and a second raised planar portion 50 which are shaped or configured to cover the top area of the disk stack . the perimeter edge of the first planar portion includes a plurality of apertures 52 which receive fasteners 54 to secure the perimeter edge to threaded openings 56 in the upper surface of the interior wall 32 which adds structural rigidity to the capture plate . the second raised portion 50 is provided with two apertures 58 , 60 configured to receive fasteners 62 , 64 , respectively , to secure the upper ends of the spindle motor shaft 28 and the actuator shaft 38 . proper alignment of apertures 58 , 60 assists in alignment of the spindle shaft relative to the actuator shaft which , in turn , assists in proper registration of the read / write element 44 relative to the data tracks on the surfaces of the disks . alignment is further achieved independent of the cover . in the embodiment shown in fig1 , 2 and 8 - 11 , the capture plate is also provided with a ledge 70 to secure the capture plate to the upper voice coil plate 72 via two fasteners 74 positioned in additional securement apertures 52 . the ledge portion 70 facilitates reducing and damping vibration induced into the capture plate during operation of the disk drive . as also shown in fig8 , in one embodiment , the first planar portion 48 may be provided with a lateral extension or protrusion 76 to provide stability to an actuator latch pin 78 . the protrusion 76 extends laterally away from the perimeter of the capture plate to abut against the latch pin 78 secured to the base plate as shown in fig1 . from fig8 it is appreciated that the aperture 60 is provided with a counter bore 80 to accommodate the head of the securement fastener 64 to secure the upper end of the actuator shaft . as also shown in fig1 and 12 , the aperture 58 is similarly provided with a counter bore 82 to accommodate the fastener 62 for the spindle shaft 28 . as shown in fig3 and 4 , the inside of the cover 12 has a first recess 90 designed to accommodate the structures within the inner chamber 18 of the base plate 14 and a second , deeper recess 92 configured to accommodate the second raised portion of the capture plate . the recesses or counter bores 80 , 82 reduce the overall height added to the assembled components by the capture plate and minimizes the depth of the recess 92 in the cover . with reference to fig5 , a second embodiment of a base plate 14 is shown . in this embodiment , four partial interior walls 94 are formed on the base plate to reduce air turbulence and to provide threaded apertures 56 for purposes of securing the capture plate 46 . here , the partial interior walls 94 do not fully shroud the perimeter edge of the disk stack to the extent shown in fig1 and 2 . alternatively , the walls 94 may be configured in a variety of shapes and sizes to fully enclose the perimeter of the disk stack , as shown in fig1 and 2 , partially enclose the disk stack as shown in fig5 , or something in between for purposes of reducing turbulence . as further shown , the walls 16 of the base plate are provided with a step or ridge 96 to accommodate the c - seal 22 . the base plate further comprises a cylindrical recess 98 to accommodate the spindle motor and hub ( not shown ) for securing and rotating the disk stack 24 . a mounting bushing 100 secures one end of the spindle shaft 28 to the base plate . a second bushing 102 secures one end of the actuator shaft to the base plate . bushings 104 are also used to secure the upper and lower voice coil motor plates ( not shown ). a recess 106 having an array of apertures 108 is configured to receive a multi - pin input / output connector ( not shown ) for interconnecting a printed circuit board containing numerous electronic components disposed on the opposite surface of the base plate to the flex circuit . a method and apparatus for hermetically sealing the apertures 108 is disclosed in co - pending application ser . no . 10 / 839 , 606 entitled “ method for controlled fabrication of hermetically sealed pcb connector ”. with the cover 12 in secured place on the base plate , the interior chamber 18 is filled with a low - density gas , such as helium , through port 110 . fig6 and 7 illustrate port 110 . one method and apparatus used to fill the disk drive with a low - density gas is disclosed in co - pending application ser . no . 10 / 839 , 548 entitled “ method for a hermetically sealable fill valve ”, the entirety of which is incorporated herein by reference as if fully disclosed herein . once filled with a low - density gas and fully sealed , the disk drive is ready for testing and use . fig1 and 14 show alternative embodiments of the capture plate 46 . in the embodiment of fig1 , the ledge 70 has been eliminated such that the capture plate is not secured to the upper voice coil plate 72 . this has the effect of reducing cost and complexity if the additional structural support is not required . fig1 and 14 also illustrate a frustro conical - shaped bushing 112 extending from the interior surface proximate the aperture 56 to provide a more stable connection to the spindle shaft 28 . the frustro conical bushing 112 is inserted to an opening in the spindle shaft 28 ( not shown ) to center and align the spindle shaft 28 and capture plate relative to each other , as well as to provide additional physical rigidity to the connection between the capture plate and the spindle shaft . as a further alternative , the bushing 112 may be secured to the spindle shaft without a fastener , but by a friction or snap - fit as would be appreciated by one of skill in the art upon review of this disclosure . a similar conical bushing may also be used in securing the capture plate to the actuator shaft 38 . a further alternative embodiment is shown in fig1 . in this embodiment , there are three distinct planar portions . a first perimeter planar portion 114 , which includes apertures 52 for securing the capture plate to the base plate , a second raised planar portion 116 , and a third planar portion 118 , which includes apertures 58 and 60 , allowing the capture plate to be secured to the spindle shaft and actuator shaft , respectively . those of skill in the art will appreciate that the capture plate may take on other configurations , with differently configured planar portions for reducing and / or damping vibrations . one issue raised by utilization of the capture plate is , rather than securing the spindle shaft and actuator shaft to the cover plate , is the desire to maintain lateral or in - plane stiffness . with a relatively thin member , such as the capture plate , securing the spindle shaft and actuator shaft , rather than using the cover , vibration can be induced in the capture plate which , in turn , may cause movement of the spindle and actuator shafts . one manner of handling this issue is to form the capture plate of multiple members laminated together . fig1 illustrates such a laminated structure . in one embodiment , the structure comprises two outer metal layers 120 and an inner layer 122 of damping material , such as 3m scotch damp viscoelastic damping polymer , sample type 242f01 - 04 . another alternative is to add damping material at least to those areas where the spindle shaft and actuator shaft are attached to the capture plate . one example of this embodiment is shown in fig1 . a third alternative is to provide a capture plate with different planar portions to enhance in - plane stiffness of the capture plate . examples of this are illustrated in fig8 - 15 . a further alternative is to configure the capture plate such that the frequencies generated by the flexing of the capture plate ( oil canning ) are at a high enough level to permit the servo system of the disk drive to compensate . it is preferred that the capture plate be made from aluminum to match the thermal expansion of the other components of the disk drive and avoid creating problems from thermal expansion . in addition , the capture plate may also be provided with slot 120 to permit servo track writing with the capture plate secured to the base plate in position . maintaining a seal for the disk drive such that it may maintain the low density gas environment over an intended lifespan can further be enhanced by impregnating the cover and base plate castings . such methods for the epoxy impregnation of the base and cover plates are discussed in co - pending application ser . no . 10 / 839 , 608 entitled “ process to seal aluminum die castings to contain low density gas ”. the disclosure of this application is incorporated by reference in its entirety . the foregoing discussion of the invention has been presented for purposes of illustration and description . the foregoing is not intended to limit the invention to the form or forms disclosed herein . in the foregoing detailed description for example , various features of the invention are grouped together in one or more embodiments for the purpose of streamlining the disclosure . this method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim . rather , as the following claims reflect , inventive aspects lie in less than all features of a single foregoing disclosed embodiment . thus , the following claims are hereby incorporated into this detailed description , with each claim standing on its own as a separate preferred embodiment of the invention . moreover , though the description of the invention has included description of one or more embodiments and certain variations and modifications , other variations and modifications are within the scope of the invention , e . g . as may be within the skill and knowledge of those in the art , after understanding the present disclosure . it is intended to obtain rights which include alternative embodiments to the extent permitted , including alternate , interchangeable and / or equivalent structures , functions , ranges or steps to those claimed , whether or not such alternate , interchangeable and / or equivalent structures , functions , ranges or steps are disclosed herein , and without intending to publicly dedicate any patentable subject matter .