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  • Pre-cooling

We get the best transfer efficiencies when the transfer lines from the Liquifier to the magnet are sufficiently cold. We have tested two modes (paths) to pre-cool the system: the slow (Figure 1 left) and the fast (Figure 1 right) pre-cooling as well as a combination of these two modes which allows us to reduce the slow pre-cooling time.

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The slow pre-cooling has consistently given higher transfer efficiencies between 56 and 58% but requires long pre-cooling times (~ 4 to 5 hours) with the potential benefit of a slow filling which is still under study.  In this mode, the Liquifier Liquefier LHe level is maintained constant. During the slow pre-cooling, we can estimate when the system is cold enough through the behavior of the Tank T temperature. Figure 2 (left) shows an example of the Tank T behavior during a slow pre-cooling mode. We can consider the system to be sufficiently cold when the Tank T temperature has decreased after being raised when the slow pre-cooling started. It takes around 4 to 5 hours to decrease (see Figure 2 (left)).   

The fast+slow pre-cooling allows us to reduce the slow pre-cooling time by initially fast pre-cooling the first part of the transfer line and then transitioning to the slow pre-cooling. Figure 2 (right) shows an example of the Tank T behavior of a slow pre-cooling that followed a fast pre-cooling. It is observed that the Tank T temperature drops significantly faster when a fast pre-cooling is initially performed reducing the slow pre-cooling time to about 1 to 2 hours. The efficiency of this procedure is consistent with the standalone slow pre-cooling efficiency minus 1% given by the initial fast pre-cooling consumption of 4 additional liters of LHe on the LiquifierLiquefier. 

   

Figure 2: Tank T temperature behavior for slow pre-cooling (left) and fast+slow precooling (right) procedures. 

The reported efficiency values were obtained by performing the magnet fills from the seam to the level probe spike except for the fast pre-cooling where the final level was taken from the level probe since we were not able to fully fill the magnet. 

The different pre-cooling procedures are given below. Please confirm with the target expert Target Expert the pre-cooling mode to be conducted. 

Slow Pre-cooling:

1. Enable the Flow PID control of the Magnet Return Bypass at 65 slm.

2. Open VJVA/B, open VJVT and close VPC.

Note: Liquifier Liquefier A/B should be on Liquify mode. If at the time of starting the slow pre-cooling the Liquifier Liquefier A/B is on Idle mode, start the slow pre-cooling and when 4L are consumed on the Liquifier Liquefier then change it to Liquify mode.

Proceed to the filling steps anytime after the transfer lines are cold. The system is sufficiently cold once the Tank T temperature decreases after opening VJVT (about 4 hours).

Fast Pre-cooling:

1. Open VJVA/B (ensure VPC is already opened).

2. Wait for TX1 temperature to drop below 100K (~ 4 min with GV02 fully opened). 
     Once TX1 < 100 K, immediately transition to Step #3, otherwise (if you wait too long), then you will see the magnet gets pressurized up to 6psi.

3. Enable the 3. Enable the Flow PID control of the Magnet Return Bypass at 65 slm.

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5. Close VPC and proceed to the filling steps.

Fast+Slow pre-cooling:

1. Open VJVA/B (ensure VPC is already opened).

2. Wait for TX1 temperature to drop below 100K (~ 4 min with GV02 fully opened).
    Once TX1 < 100 K, immediately transition to Step #3, otherwise (if you wait too long), then you will see the magnet gets pressurized up to 6psi. 

3. Enable the Flow PID control of the Magnet Return Bypass at 65 slm.

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Proceed to the filling steps anytime after the transfer lines are cold. The system is sufficiently cold once the Tank T temperature decreases after opening VJVT (about 1 hour).

  • Filling

10.  Open the MagRetBypass valve fully by pressing the "Full OpenMagnet PS Main" button on "MagRetBypass_Main.vi" in CCP and wait until you can see it is fully open on the CCP panel. The magnet pressure will start decreasing. The FMR may spike momentarily.

2. After the FMR has stabilized, set the Liquifier A/B to "Manual + Idle", open SV501A/B (inlet valve), and set FC501A/B at 45 SLM. Ensure the outlet valve SVNA/B is closed and the cold heads of the Liquifier are off.

3. When the magnet level reaches 48%, open VPC, close VJVA/B, close VJVT.

4. Set the Liquifier A/B back to "Auto+ Liquefy".

5. Enable the Pressure PID auto control of the MagRetBypass valve at 0.9 psi.

  • Post-filling

Monitor the Liquifier A/B pressure until the cold-head temperatures are below 5.5 K ensuring the Liquifier A/B pressure doesn't go above 9 psi:

1. If the Liquifier A/B pressure rises, change the outlet Flow to 60slm on "Settings" and wait until the Dewar pressure is between 6-7 psi and the inlet flow is not zero.

2. Repeat step 1 reducing the flow by 10 SLM until reaching 2 SLM. If the pressure increases when the flow is reduced, change it back to the previous value.

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CCP,  and then change the magnet level probe reading option from "HOLD" mode to "CONT" mode.
     Image Added(Click on the field "HOLD", then you will see the two options "HOLD" and "CONT" )

           1. Open the MagRetBypass valve fully by pressing the "Full Open" button on "MagRetBypass_Main.vi" in CCP and wait until you can see it is fully open on the CCP panel. The magnet pressure will start
               decreasing. The FMR may spike momentarily.

2. After the FMR has stabilized, set the Liquefier A/B to "Manual + Idle", open SV501A/B (inlet valve), and set FC501A/BQM (see the box on the left of FC501A/B) at 45 SLM.
    Image Added
    Ensure the outlet valve SVNA/B is closed and the cold heads of the Liquefier are off.

3. When the magnet level reaches 48%, open VPC, close VJVA/B, close VJVT.

4. Set the Liquefier A/B back to "Auto+ Liquefy".

5. Enable the Pressure PID auto control of the MagRetBypass valve at 0.9 psi.
    Image Added


  • Post-filling

Monitor the Liquefier A/B pressure until the cold-head temperatures are below 5.5 K ensuring the Liquefier A/B pressure doesn't go above 9 psi:

1. If the Liquefier A/B pressure rises, change the outlet Flow to 60slm on "Settings" and wait until the Dewar pressure is between 6-7 psi and the inlet flow is not zero.

2. Repeat step 1 reducing the flow by 10 SLM until reaching 2 SLM. If the pressure increases when the flow is reduced, change it back to the previous value.

Note: Always confirm on the Liquefier screen whether the outlet flow on FCA/B gives what you set it to. If not, press the "Idle" button followed by the "Liquefy" button immediately after.


Filling Magnet Helium Space by Lowering the Liquifiers Pressure

In this procedure, only a fast precooling is done. This method gives a higher efficiency than performing the fill with a fast-precool without lowering the Liquifiers pressure which is generally used only when a magnet fill needs to be immediately done and there is not enough time to wait for the Liquifiers to reach a lower pressure set point.

Fast Pre-cooling:

1. Set the LiqA/B pressure at 3.0 PSI and in the IDLE model, around one hour before the fill and wait for the dewar pressure to go down to 3.0 PSI. Once you confirm you achieved this pressure proceed to the next step

2. Open VJVA/B (ensure VPC is already opened).

2. Wait for TX1 temperature to drop below 100K (~ 4 min with GV02 fully opened).

3. Open VJVT and close VPC and proceed to the filling steps.

4. Proceed to the Filling and Post-filling steps described above. 




——— Previous Procedures ———————


Use this .docx file (download and edit) to collect data during the fill:  

TypeForm
Filling from a single QT Dewar

Magnet_LHe_Fill_Checklist.docx (updated on  )

Filling from both QT Dewars

Magnet_LHe_Fill_Checklist_filling_from two_Dewars.docx(updated on  )


Older versions: Magnet_LHe_Fill_Checklist.docx

Condition

Procedure for filling from a Single Dewar(alternating each Dewar every other day)


Note: Select the Dewar that you are going to use to fill (Liq should contain at least 193-200 L of Helium).

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  1. After waiting ~30 mins, press the "Full Open" button on "MagRetBypass_Main.vi" in CCP, to open the MagRetBypass valve fully, and wait until you can see it is fully open on CCP panel.
    You will start seeing the magnet pressure start decreasing.
  2. Monitor the FMR and make sure the total flow is below 500 slm. If it is above 500slm then wait until it is below 500 slm. Also, ensure the PC 1 is also below 1.5 psi.
  3. Monitor the behavior of the magnet pressure, and once the magnet pressure is below 2psi, then  Switch the liquefier that you are filling, to "Manual + Idle" mode, and open SV501 solenoid valve, and after that set FC501 to 45slm.
    Note: Monitor the FMR and make sure the total flow is below 500slm. If it is above 500slm then use 40slm on FC501.
  4. Monitor the pressure difference (between magnet and delivery Dewar) using the "LHe Transfer page", and ensure it keeps increasing towards 3.0 psi.
    Ensure the FMR value doesn't exceed 500slm (~480slm would be ideal) and if it is increasing above 500slm, then reduce the "FC501" by a couple of 'slm' and continue to monitor.
  5. Monitor the parameters using https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/transfer.php
  6. You may need to reduce (increase) it if the pressure difference is increasing-faster (reducing) while monitoring the FMR; but 45 slm seems the nominal value based on the past fills.
  7. Keep monitoring the fill parameters: Magnet level, Delivery Dewar level, Pressure difference, FMR
  8. Maintain the pressure differential above 3 psi, by adjusting FC501A/B if necessary (after setting FC501A/B to 40slm is usually smooth until the end of the fill, but pay attention in-case you have to change it)
  9. Monitor everything, until the magnet level reaches 50%, and then observe a level-spike that confirms that you have filled the magnet up to the top level (145 L).
    In case you don't have enough liquid in the delivery dewar, you can stop before seeing the level-spike.
  10. Open VPC,  Close VJVA/B, Close VJVT.
    1. This is the end time of the transfer.  Record the time, the magnet level, and the Liq level.
  11. Enable the auto control of the MagRetBypass valve.  Change the set point to 0.9 psi.
  12. Change the Liq mode to "Auto+ Liquefy" mode:
    1. Change the Dewar Set pressure to 6.5 psi.
    2. Set the outlet flow is 40 SLM. Note: you will need to pay attention to this Liquefier for the next ~1 hr until you change this to 2 slm step-by-step while monitoring the Dewar pressure (follow Steps #17, #18).
      If the Dewar pressure is keep increasing beyond the Set pressure (6.5 psi), then you will need to increase this outlet flow to 60slm. When you change this, always confirm on the Liquefier screen's FCA/B whether it's flowing what you set to. If not, you will have to quickly press "Idle" button and then press "Liquefy" button immediately after.
    3. The Liquefier Compressors' coldhead heaters should be OFF, but it's better to confirm that on the "Helium Compressors" screen.
      If they are ON, please turn them off one-by-one (double tap/click on each button for heaters).
    4. If you change the mode of the other liquefier in step #4, then change it back to Liquefy mode.
  13. Wait until the Liquefier's Dewar pressure (PT503) gets slightly below 6.5 psi, and then check the actual inlet flow (FC501 A/B I) to the liquefier is above 40 SLM (FC501 A/B Q will be 60 slm).
    This indicates that you can change the Outlet Flow Set point to a lower value like 30slm (follow the next steps over the next ~40 mins).
    Note: Ensure the Dewar pressure doesn't go above 9 psig. If it is rising, you should change the Outlet Flow Set point to 60slm and wait until the Dewar pressure is between 6-7 psi.
  14. Repeat step #17 with outlet flows = 20, 10, 5slm, and and then to 2 SLM when the cold-head temperatures are below 5.5 K.
  15. Confirm that the Liq pressure stays around the set point (6.5 slm).
  16. Calculate the transfer efficiency using initial and final levels in the magnet and the Liquefier Dewar.
  17.  Post the filled Magnet_LHe_Fill_Checklist.docx file on uva-elog including the date of the fill as part of the file name (for example: Magnet_LHe_Fill_Checklist_03-29-2024.docx or .pdf file)
    If you don't have access to the uva-elog, then please send this file to the Target Expert on shift.

Tentative procedure for filling from two Dewars


  1. Download Magnet_LHe_Fill_Checklist_filling_from_two_Dewars.docx file, fill in all the "initial parameters" and get ready to fill the rest of the fields during the fill.
  2. You will see an alarm when Tank B at 4.6 K, at that time ensure that the Dewar B pressure at 3psi and the Dewar A pressure at 5.5 psi.
    This step needs some time estimate depending on how long each Dewar takes to reach the set pressure.
  3. Monitor the magnet level reaching the seam (when Tank B is around ~4.8 K)
  4. Switch the Magnet level probe to "CONT".
  5. At right before the fill, open the run valve to 2 turns for 3 mins and put it back to 0.8 turns.
  6. Start pre-cooling by opening VJVA first (this is to pre-cool the line A assuming that the line A is relatively colder then we switch filling from B→A; we will have to pre-cool line B in the next step).
  7. When TX1 reaches ~100 K, then pre-cool line B by opening VJVB and close VJVA.
  8. Ensure TX1 ~100 K or below, then open Mag return bypass fully, open VJVT, and close VPC.
  9. Switch the Dewar B to Manual mode and set FC501 B to 45slm, and monitor FMR.
  10. Monitor until the Dewar B level reaches 12 L, and then open VJVA to pre-cool until it reaches 9 L.
  11. Close VJVB. Now you are filling from A. Magnet Pressure may have a pressure spike. After the pressure spike set Dewar A to Manual mode and set FC501A to 45slm.
  12. Switch LQ-B to Auto + Liquefy mode, and set the Dewar pressure back to 6.5 psi.
  13. Adjust the flow FC501A  to keep FMR below 480slm, PC1 below 1.1 psi, and magnet pressure below 2.5 psi.
  14. At the end of the fill, Open VPC, Close VJVA, and VJVT. Also, ensure VJVB is closed.
  15. Switch LQ-A to Auto + Liquefy mode, and set the Dewar pressure back to 6.5 psi.
  16. Set the Magnet Bypass to pressure PID to 0.9 psi.
  17. Switch the Magnet level probe back to "HOLD" mode.

Procedure for filling from a Single Dewar(Since 03/29/2024)


Note: Select the Dewar that you are going to use to fill (Liq should contain at least 200 L of Helium), and then change Dewar Set pressure to 3 psi at least 3 hours before the fill.

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