S800 Documentation

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====== Detector gas handling system ======

  * [[#General information]]
  * [[#LabView Control Program]]
  * [[#Preparation of Gas bottles|Preparation of Gas bottles for filling of detectors]]
  * [[#Filling Ion Chamber with Gas]]
  * [[#Filling CRDC1 and CRDC2 with Gas]]
  * [[#Removing Gas from Focal Plane Detectors]]
  * [[#Tracking Gas bottles pressures|Tracking Gas bottles pressures from Barney]]
  * [[#Replacing Gas bottles]]

===== General Information =====
Required controls and monitoring
  * LabView gas handling system application **FPGHS_TCPIP-II.vi** 
  * PanelMate **S800vac.ui page 07**: Focal Plane Detector

The gas handling systems for both Focal Plane gas-filled detectors – the [[Detectors#Ionization Chamber|Ionization Chamber]] and the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]] – are remotely controlled via a single LabView application running on the computer [[Software|S800FP-PC]] in the S3 vault. This computer can be accessed remotely from the desktop of computer [[Software#u6pc5 (data U6)|u6pc5]], by clicking in the icon **S800 Vault PC**, or by typing ''xfreerdp /u:s800 /v:35.9.56.104'' from a Linux terminal. A terminal will pop-up asking for the s800 password. Once the virtual session in S800FP-PC is open, the gas handling system can be opened by clicking in the corresponding icon on the desktop **FPGHS_TCPIP-II**. This icon opens the local directory ''C:/Users/s800/Desktop/FPGHS_TCPIP-II''. Once there, run the Labview executable **FPGHS_TCPIP-II.exe**. 

Note that since the same roughing pump drives the gas handling systems for both gas-filled detectors, extra precautions must be taken to protect one detector from the pressure of the other detector. The fact that the same pump drives both systems is not indicated on the graphics for the LabView control application

===== LabView Control Program =====
To start the gas handling system control application, click on the LabView icon **FPGHS_TCPIP_Corrected_V01** on the [[Software|S800FP-PC]] desktop.

  * A log file should be specified before operating the gas handling system
      * A window automatically pops up asking for the name of the log file when the program starts
      * Use the number of the current experiment (or "test") as the name of the log file and save in file /intranet/files/departments/operations/s800/TO_BE_SPECIFIED
      * The On indicator next to Is VI running? will flash until a log file is specified and the program initiates communications with the hardware

  * Click the **Valves** tab at the top of the LabView window to display the overview of the gas handling system (see Figure below)
      * The triangles on the valve control buttons (as well as the square valve status indicators near the control buttons) are red to indicate that a valve is closed (e.g., control 25 for the CRDC return above) and green to indicate a valve is open (e.g., control 22 for the CRDC bypass above)

  * The gas handling control application should always remain open during the entire time either detector is filled with gas to ensure the log file is continuously updated

  * Once both detectors are empty, this application can be closed with the “X” button on the upper right corner of the window.

{{:wiki:gas-handling-labview.png?800|Labview control panel of the gas handling system}} 


===== Preparation of Gas bottles =====

==== In Data-U6 ====
      * Ensure **I265GV** is closed (in PanelMate **S800vac.ui page 07**) to isolate focal plane vacuum chamber from the rest of the beamline
      * Confirm that the focal plane chamber is under vacuum
      * Confirm that the only open gas handling system valves are **4, 5, 6, 20, 21, and 22**
      * (Check section on [[vacuum control|vacuum control]] for further details.)

==== In the S3 vault ====
      * Ensure that the gas handling system roughing pump is running and has a good vacuum
           * The pump sits on the floor under the focal plane behind the south support post 
           * The display unit for the pressure at the pump has a needle indicator and is mounted under the [[Stations#Focal Plane Station|focal plane]] on the south support post 
      * Ensure that the main valves on the gas bottles are open (see pictures below)
      * Open valves downstream of regulators in each bottle
      * Ensure that the gas bottles are not empty
           * The gas regulators are not normally adjusted. They should all be set to provide a pressure around 20 psi
           * The bottle supplying the P-10 gas for the [[Detectors#Ionization Chamber|ionization chamber]] is secured to the cross-brace of the south support for the focal plane chamber. It has an electronic Ashcroft pressure gauge upstream of the regulator (toggle on and off with the "on/off" switch) and a mechanical pressure gauge downstream of the regulator 
           * The bottle supplying CF<sub>4</sub> (tetrafluoromethane) gas for the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]] is secured to the cross-brace of the south support for the focal plane chamber. It has an electronic Ashcroft pressure gauge upstream of the regulator (toggle on and off with the “on/off” switch) and a mechanical pressure gauge downstream of the regulator 
           * The bottle supplying isobutane (C<sub>4</sub>H<sub>10</sub>) for the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]] is secured to the south support post for the focal plane chamber. It sits on a scale for monitoring the isobutane consumption – the electronic display for the scale sits on the chiller unit under the focal plane chamber. It has a mechanical pressure gauge downstream of the regulator

{{:wiki:gas-bottle3.jpg?300}}
{{:wiki:gas-bottle1.jpg?300}}

===== Filling Ion Chamber with Gas =====

  * Follow instructions under [[#Preparation of Gas bottles|Preparation of Gas bottles]] 

  * Monitor the pressure of the focal plane vacuum chamber (as read out via the I264IG ion gauge in PanelMate **S800vac.ui page 07**) while detectors are being filled with gas; the pressure normally stays below 5E-5 Torr.

  * Confirm that the detector pressure as indicated by the display labeled P.T. #1 reads below a couple of Torr
      * To zero this display:
          * Click on the **Slot 3 (PT1)** tab to access the details page for PT #1
          * Click the **Zero Sensor** button
          * Click the **Valves** tab at the top of the LabView window to return to the overview display of the gas handling system

  * Close **valve 6**

  * Open **valve 2**; the flow reading at MFC #1 should jump momentarily

  * Fill Ion chamber
      * Enter the desired fill pressure and start the automatic filling process
          * Click on the tab labeled **Slot 8 (M-card) IC** to access the page with the pressure set point control
          * Enter the desired pressure (typically 300 Torr) in the field under the knob labeled Set Point
          * Click button labeled **Update Set Point**
          * Click button labeled **Return to AUTO Mode** on left to start filling/regulation
          * Click the **Valves** tab at the top of the LabView window to return to the overview display of the gas handling system to monitor filling. The flow readings for MFC #1 will increase and eventually disappear as the readout value overflows the display field (this is normal behavior)
      * Open **valve 9**
      * If necessary, the filling process can be stopped at any time by pressing the valve button labeled **Close MFC #1**
      * The filling process will take several minutes

  * When the detector is filled, close **valve 5**



===== Filling CRDC1 and CRDC2 with Gas =====

  * Follow instructions under [[#Preparation of Gas bottles|Preparation of Gas bottles]]

  * Monitor the pressure of the focal plane vacuum chamber (as read out via the I264IG ion gauge in PanelMate **S800vac.MT2 page 07**) while detectors are being filled with gas; the pressure normally stays below 5 x 10<sup>-5</sup> Torr.

  * Confirm that the detector pressure as indicated by the display labeled P.T. #2 reads below a couple of Torr
      * To zero this display:
          * Click on the **Slot 4 (PT2)** tab to access the details page for PT #2
          * Click the **Zero Sensor** button
          * Click the **Valves** tab at the top of the LabView window to return to the overview display of the gas handling system

  * Close **valve 22**
 
  * Open **valves 10 and 15**

  * Open **valve 12**; the flow reading at MFC #2 should jump momentarily

  * Open **valve 17**; the flow reading at MFC #3 should jump momentarily

  * Fill CRDCs
      * Enter the desired fill pressure and start the automatic filling process
          * Click on the tab labeled **Virtual Ch. 0 (CRDC)** to access the page with the pressure set point control
          * Enter the desired pressure (typically 40 Torr) in the field under the knob labeled **Set Point**
          * Click button labeled **Update Set Point**
          * Click button labeled **Return to AUTO Mode** on left to start filling/regulation
          * Click the **Valves** tab at the top of the LabView window to return to the overview display of the gas handling system to monitor filling. The flow readings for MFC #2 and MFC #3 will increase. The LabView application controls the gas mixing ratio based on the flow ratio (scaled with a calibration constant)
      * Open **valve 25**
      * If necessary, the filling process can be stopped at any time by pressing the valve button labeled **Close MFCs #2 & #3**
      * The filling process will take several minutes

  * When the detector is filled, close **valve 21**


===== Removing Gas from Focal Plane Detectors =====

  * Monitor the pressure of the focal plane vacuum chamber (as read out via the I264IG ion gauge in PanelMate **S800vac.MT2 page 07**) while gas is being removed from detectors; the pressure normally stays below 5E-5 Torr

  * Ensure that the system is in the normal state for flowing gas through the detectors
      * Confirm that the focal plane chamber is under vacuum
      * Confirm that **the only open** gas handling system valves are **2, 4, and 9 for the Ion Chamber** and **10, 12, 15, 17, 20, and 25 for the CRDCs**
      * Confirm that the detector pressures as indicated by the displays labeled P.T. #1 for the Ion Chamber and P.T. #2 for the CRDCs show the correct fill values (typically 300 Torr and 40 Torr, respectively)
	
  * Ensure that I265GV is closed to isolate focal plane vacuum chamber from spectrograph

  * Stop the gas flow into both detectors by clicking valve buttons labeled **Close MFC #1** and **Close MFCs #2 & #3**

  * Isolate the gas supply by closing **valves 2, 12, 17, 10, and 15**

  * Open **valves 5 and 21**

  * **IMPORTANT:** CLOSE **VALVE 25** to protect CRDCs from Ion Chamber pressure

  * Empty Ion Chamber to a pressure at or below the pressure of the CRDCs
      * Open **valve 8**
      * Wait for the Ion Chamber pressure to reach or drop below the pressure in the CRDCs; this process will take several minutes

  * Finish emptying both detectors
      * Open **valve 25**
      * Open **valve 24**
      * Wait for the pressure in both detectors as indicated by the displays labeled P.T. #1 and P.T. #2 to reach 0.5 Torr or less; this process will take at least an hour
	
  * Close **valves 9 and 25**

  * Close **valves 8 and 24**

  * Open **valves 6 and 22**

  * Enter S3 vault and close valves downstream of regulators in [[#Preparation of gas bottles|gas bottles]]: P-10 and CF<sub>4</sub> (tetrafluoromethane). Close the main valve for the C<sub>4</sub>H<sub>10</sub> bottle.

===== Tracking Gas bottles pressures =====
In order to track the status of the gas bottles for the [[Detectors#Ionization Chamber|ionization chamber]], the  [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]], and the [[Detectors#[Tracking Parallel Plate Avalanche Counters (TPPAC)]|TPPAC]], it is possible to monitor their remaining pressures from Barney. Just open the **A1900** page, then **Tools**, and then **Gas Status**. The following window will be displayed:



{{:wiki:gas-bottles-status.jpg?900|Barney display of pressures of all "supported" gas detectors in the lab}}




===== Replacing Gas bottles =====
In preparation
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