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Load-Lock Systems |
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Load-Lock Systems Load-lock systems are atmosphere to vacuum sample staging and entry systems typically mounted to larger research or process systems. They are a convenient and practical method for transferring samples in and out of vacuum systems. MDC load-lock systems are available with both circular and rectangular entry ports. Circular port systems will accommodate sample sizes of 1-3/8", 2-3/8" and 3-3/4" in diameter. Rectangular port systems will accommodate sample sizes 8" in diameter. All load-lock systems are comprised of five basic components including a sample staging chamber, gate valve, sample transporter, quick-access door and an observation window. Sample Staging Chambers Spherical sample staging chambers are constructed with seven vacuum ports, six of these are arranged in a six-way cross pattern. Four of the seven ports are occupied by load-lock system components including a circular gate valve, magnetic transporter, a side mounted quick-access door and an observation viewport. Two additional ports are used for system pumpdown and venting. The seventh and final port is blanked off and available for customer disposition. Rectangular sample staging chambers are constructed with five vacuum ports, four of which are arranged in a four-way cross pattern. Three of the five ports are occupied by load-lock system components including a rectangular gate valve, magnetic transporter and a top mounted quick-access door with an integral observation window. The two remaining ports are used for system pumpdown and venting. Gate Valves The stainless steel vacuum gate valves used on load-lock systems incorporate a patented gate valve locking mechanism. No contact is made between the valve’s body and the locking mechanism, a feature which markedly decreases vibration and insures smooth valve operation. Valve low outgassing characteristics can be attributed to a fusion welded stainless steel body, edge welded stainless steel bellows as well as small cross-section o-rings and the elimination of blind internal cavities. The valve’s gate and carriage can be removed through the valve’s bonnet flange for gate seal replacement, cleaning, etc., without removing the valve body from the system. MDC gate valves require about half the number of moving parts found in comparable valves. This reduction in moving components minimizes wear and particulate generation which in turn provides valves of superior performance and reliability. Circular load-lock systems are offered with three gate valves sizes 1-1/2, 2-1/2 and 4 inch port diameters. Standard port mounts are Del-Seal™ CF metal seal flanges, which are ideal for ultrahigh vacuum systems. Gate valve actuation is manual with electropneumatic configurations available on request. Rectangular valves are designed for use in high vacuum applications including semiconductor processing. Flange-to-flange body thickness is 2.75" (70mm). Load-lock systems are offered with a slit port 1.00" tall by 8.30" wide. These gate valves are fitted with manual actuators but can be ordered in electropneumatic configurations. Magnetic Transporters All load-lock systems are supplied with UHV magnetically coupled sample transporters. Sample transporters provide manually actuated linear travel and a full 360° sample rotation, ideal for transporting samples between the sample staging chamber and a main process chamber. Linear positioning is controlled by sliding an external sleeve which is magnetically coupled with the transporter rod and sample holder inside the system. Optional linear guide rods can be added to circular entry load-lock systems. Rectangular entry loadlock systems include the guide rod option since rotation of large diameter samples is not possible on these systems. Guide rods prevent sample rotation during linear travel. Magnetic transporters come ready to accept the complete range of Cab-Fast® in-vacuum sample handling accessories. Cab-Fast® sample handlers are specifically designed for use with the transporters featured in this catalog. Sample holding accessories are not included with base load-lock systems and must be purchased separately. Reference page 444 for the complete line of Cab-Fast® sample handling components and their specifications. Quick-Access Doors Quick-Access doors provide convenient and fast manual loading of samples in and out of sample staging chambers. Circular load-lock systems are fitted with blank stainless steel quick-access doors while the rectangular systems have quick-access doors with integral glass observation ports. Circular load-lock systems can be fitted with viewport fitted doors if requested. All access doors are supplied with Viton® elastomer seals. High temperature Kalrez® elastomers can be used to increase the systems maximum temperature rating. Doors are hinged and use a swing-away hand knob locking mechanism. Viewport fitted doors are constructed with Corning type 7056 glass fused to Kovar® transition sleeves. Observation Viewports Load-lock system viewports are centered on the sample staging chamber directly above and perpendicular to the transporter’s axis of motion. They are observation ports that allow visual monitoring of the sample loading process as well as subsequent sample rotation during transfer between chambers. Circular load-lock systems are fitted with flange mounted viewports bolted to the staging chamber. Rectangular load-lock systems on the other hand have a limited number of ports and therefore have viewports installed directly to the quickaccess door. Regardless of the method of installation, all viewports are constructed of vacuum compatible materials suitable for high and ultrahigh vacuum service. The viewport windows are manufactured of optical grade Corning type 7056 glass which is suitable for most vacuum optical applications. These glass viewports are bakeable to 400°C and limited only by elastomer seals elsewhere in the system. The 7056 glass is fused to a Kovar® metal sleeve which in turn is fusion welded to a stainless steel Del-Seal™ CF flange or directly to a quick-access door. The Kovar® sleeve is a low expansion nickel-iron alloy ideally suited for glass to metal bonding. It provides flexibility necessary for the survival of the glass seal during thermal excursions. Care should be taken during the bakeout process of any glass to metal sealed component. The maximum recommended thermal gradient for glass to metal sealed components should not exceed 5°C per minute. Thermal gradients in excess of this can damage the glass to metal seal interface. Port Aligners Port aligners are adjustable port flange interfaces designed to correct mate-up between components with alignment imperfections. Load-lock gimbals are unique port alignment instruments specifically designed for the precision alignment of magnetically coupled transporters as used with circular and rectangular entry load-lock systems presented herein. Load-lock gimbal port aligners are fitted with precision micrometer adjustments for both horizontal tilt (above and below a horizontal plane of travel) and side to side parallel axial displacement. They include a stainless steel formed bellows adapter which mates between the magnetic transporter and the sample staging chamber. Other port alignment tools offered in this catalog include standard gimbals, precision off-axis and heavy duty off axis port aligners. Caution |
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