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  1. Purpose

    1. Goal
      1. The goal of this training module is to provide a detailed procedure on how to safely and efficiently bake an RGA cart. When a RGA cart doesn't meet the clean qualification requirement, baking is the 1st step to requalifying. The procedure will also include how to use a baking controller for ramping up and down in temperature.
    2. Capabilities Include 
      1.  Vacuum skills 
      2.  Designing skills
      3.  Baking skills
  2. Subject Matter Experts - May help provide instruction and guidance for this Training Module

    1.  Brady Robertson 
      1. bradyrob@slac.stanford.edu
    2. Ivan Curiel
    3. Ruben Curiel
    4. Cynthia Melendrez
    5. David Amaton
  3. Resource List

    1. RGA Cart Maintenance and Operation Document  (List of RGA cart Components)
    2. Amanda's doc: RGA Cart Maintenance and Operation (After baking is complete)

  4. Begin Training Content

Step1:

Clear the area for baking preparation and process. Baking temperatures can reach up to 250°C, therefore it is important to have a clear area for minimal supervision during long bakes.

...

Check that your system is under vacuum before bakingat a pressure of at least 10^-5 torr. The small molecules stuck adsorbed onto the walls and bouncing around your system will chambers inner surfaces and need an exit path after being excited by the ramping increase of heat. Baking without being under vacuum will both absorbs and remove any molecules from the wall of your chamber.

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An RGA device has a temperature bake out of about 250°C with and extender or electronics. For more about and RGA go to link:Theory (Brady Robertson)

Link: https://www.mksinst.com/mam/celum/celum_assets/resources/MicroVision2ds.pdf

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Prepare all the components needed for the bake.

List of Components
Tinfoil Aluminum Foil( a lot)
ThermalcouplesThermocouples
Gloves
Heater tape
Temperature PID controller (preference)
Variac Temp controller (preference)


Step4:

Add thermal couples thermocouples to your chamber and keep them in place using small aluminum strips spot welded onto the chamber. Where to place the thermal couples is up to you, but placing them where you believe the hottest area will be is sufficient. Type K thermocouples, which are made up of two metals Chromel and Alumel, is what we typical use as temperature sensors.

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Apply a thin layer of aluminum foil to the chamber and on top of thermal couplesthermocouples. Do not cover electronics or handles with aluminum and avoid areas that do not have high bakeout temperatures such as, turbos and roughing pumps. Applying a thin layer of aluminum helps spread the heat provided by the heater tape, since aluminum is a good conductor of heat. If the heater tape is applied directly to a steel chamber you can potentially have hot spots because steel is not a good conductor of heat. 

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When the bake is complete ramp the temperature of your system down to normal temp. When the ramp is complete remove tinfoil/heater tape and start adding electronics back.

Image Modified 

bakeout supplies in B758 (B757?)