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====== Tube oven annealing ======
The tube oven has a temperature range of 50-1200 °C and can fit 1 inch diameter tubes. Temperature regulation is done by a Eurotherm 2404 controller. 
Three different process gasses can be connected, at the moment H2 and Ar are connected. Gas flow of each gas is controlled by a mass flow controller (MFC), mixing is possible.
A dry vacuumpump is used to pump down the system, lowest pressure that can be achieved is roughly 1e-2mbar.
A pressure control valve can be used to control either the flow or pressure in the tube. Most often the pressure control valve is operated in the fully open state to achieve a pressure as low as possible. Pressure can be controlled between 1e-2mbar and 100mbar.

A Python program on the PC "hydrogen_annealing" can be used to set gas flows, the pressure set point and monitor and log the process.
To ensure safe handling of hydrogen, mulitple safety interlocks are present. If an interlock condition is not met, the main supply at the H2 gas cylinder will be closed automatically.

Temperature regulation of the oven is done with Eurotherm software; "iTools engineering studio".

====== Notes before usage ======
  * read safety notes below
  * Keep the vacuum components clean and do not use tubes that are not assigned to you
  * Make sure to mark or label your tube if you wish to keep it clean and keep it in the cupboard
  * Indicate whether samples are loaded or not
  * Check the specifications of the tube and boat before usage, make sure your tube and boat are suitable for your process (operating temperature) 
  * Place all vacuum parts in the small boxes near the oven

===== Tube specifications =====
Outer diameter: 25mm or 1 inch (25.4mm)\\
Length: between 62cm and 70cm

Operating temperatures:
  * Pyrex: 500°C (greenish color when viewing the edges)
  * Quartz: 1000°C
  * Al2O3: 1700°C


====== Safety ======
Most important safety points are:
  * hydrogen
  * high temperature
  * pressurized gas cylinders

==== Hydrogen safety ====
If a process requires hydrogen we need to make sure it doesn't escape into the lab and the gas is mixed with nitrogen at the inlet of the pump to achieve a H2/N2 mixture below LEL.

Flammable range of H2 in air is >4% (LEL) and <75%(UEL).\\

A flammable mixture of H2 and Air can be ignited on a hot surface if the temperature exceeds 500°C (in literature different values are mentioned, 500°C is chosen on the safe side).\\ 
Hence when working with Hydrogen do not use processes above this temperature. 

There should be adequate ventilation in the lab, the window should be open.

no sources of ignition close to the setup
  * Open flames
  * Mechanically generated impact/friction sparks
  * Electric sparks
  * Electrostatic discharge
  * Adiabatic compression
  * **High surface temperature**


Dangerous situations can occur when:
  * Leak in the system (anywhere between reducer and outlet) will result in H2 release into the lab.
  * Failure or low flow of purge gas will result in high concentration H2 into outlet and pump.
  * Vacuum pump failure, local buildup of H2
  * Nitrogen back streaming, outlet function is not working properly, local build up of high concentration H2

=== H2 safety interlocks ===
There is a safety valve directly behind the hydrogen cylinder in the safety cabinet, if one of the interlocks is not met the valve will close automatically. \\
When all safety interlocks are met, the valve can be openend manually from the GUI.

  -  h2 level in lab < 2%
  -  n2 flow > 100*h2 flow and 100*h2 setpoint
  -  fume hood exhaust = on
  -  vacuum pump in normal operation
  -  leak test interlock:  first achieve base pressure
       * if flow is on:  pressure should stay below 100mbar
       * when interlock has triggered, the interlock can be reset after achieving base pressure
  -  connection with PLC


==== High temperature safety ====
Always lock the oven when a process is running.
Let process cool down to 50°C before handling any components.
No organic solvents on the table when a process is running.
Work with clean tubes


==== Pressurized gas cylinders safety====
Do not attempt to change cylinders or connected equipment, always consult with a technician.


===== Setting up and starting the process =====


  * check that your tube and sample boat have a higher operating temperature specified than your process temperature
  * load tube with sample into furnace
  * connect the tube to the vacuumpump and the gaslines
    * you can run a process with just the vacuumpump connected, connect a blind flange to the right side
    * or you can run a process in air, you don't need to connect anything   
  * run the "hydrogen_annealing" python script from the desktop 
  * start iTools Engineering Studio, if the temperature controller is not found: use 'Scan' in the toolbar to find all connected devices
  * open pressure control valve in python script with the 'OPEN/CLOSE pressure control valve button'
    * depending on the manual switch on the electronic box on the wall, this button will either OPEN or CLOSE the pressure control valve 
    * if you want to use a pressure setpoint you can set the pressure control valve to setpoint mode.
  * start pump
  * pressure should reach <1e-1mbar, if not: find and solve the leaks (typically the tube connectors)
    
  * **if you want to use hydrogen:**
    * open hydrogen cylinder in yellow safety cabinet with the angle key
    * set 1 bar on the secundary gauge of the pressure reducer
    * close safety cabinet
    * open manual valve behind the hydrogen MFC
    * set nitrogen flow with the large round black needle valve on the wall; nitrogen flow should be >100x hydrogen flow setpoint to dilute the gas mixture going into the pump. 
        * When first opening the valve you will have a small burst of flow, set a high nitrogen flow ~20000sccm when starting, later you can lower this to 100x hydrogen flow setpoint.
    * make sure all safety interlocks are met; now you can open the hydrogen safety valve from the GUI


    * open manual valves near MFCs of the gasses you would like to use
    * set other process parameters with the GUI  
    * load temperature program from itools to the controller and run the program
      * hold the run/hold button for a few seconds to stop the controller, if the controller is in hold state the program will not load. 


===== Cool down and finish =====
Do the following steps ASAP if your process allows for it while the oven cools down, if you need gas flow when cooling down the sample; first turn of the oven and wait until the sample has cooled down to the desired temperature before following the steps below

  * **If you used hydrogen:**
      * close hydrogen cylinder in the yellow safety cabinet with the angle key, keep hydrogen flow on
      * wait **until hydrogen flow is almost zero**
      * 'OPEN hydrogen MFC' from GUI
      * wait **until hydrogen flow is zero**, indicating the gasline is empty
      * close pressure reducer on the hydrogen cylinder
      * close safety cabinet
      * close hydrogen safety valve from the GUI
      * close green manual valve near hydrogen MFC
      * stop nitrogen flow
      * pump down to <1e-1mbar
      * turn off oven and wait for oven to cooldown to <50°C (can take a few hours since there is no active cooling)
      * switch off pump
      * vent system
      * take out sample
      * take tube out of the oven, and store it in the cabinet, properly labeled
      * put blind flanges or aluminium foil on the open parts of the system and tube

  * If you did not use hydrogen:
      * set gas flows to zero and close green manual valves near the MFCs
      * pump down to <1e-1mbar
      * turn off oven and wait for oven to cooldown to <50°C (can take a few hours since there is no active cooling)
      * switch off pump
      * vent system
      * take out sample
      * take tube out of the oven, and store it in the cabinet, properly labeled
      * put blind flanges or aluminium foil on the open parts of the system and tube


===== Common problems =====

=== PLC not connected ===
The extra network card in the PC sometimes loses connection. Open the PC and unplug and plug back the network card. Restart the computer. Open the PLC program and try to connect to the PLC. LOGO!SoftComfort will recognize that the IPadres of the PLC is not in the same subnet mask and will ask to add this; acknowledge. Now you should have connection again.