We continue the investigations related to moving bump on the LVDT channels with the support of Gianmatteo in the West End Building.

Below the detail of the operations performed

• NIKHEF LVDT box
  • 2024-11-29-12h26m-UTC: switched OFF
  • 2024-11-29-12h29m-UTC: switched ON
  • None improvements observed : the line at 8500Hz remains at the same frequency and at the same level
• SWEB_DBOX_LC (Dbox_SN43)
  • 2024-11-29-12h30m-UTC: switched OFF
  • 2024-11-29-12h32m-UTC: switched ON
  • 2024-11-29-12h32m56-UTC   Reconfigure SWEB_DBOX_LC in SWEB_dbox_rack
  • None improvements observed : the line at 8500Hz remains at the same frequency and at the same level
• SWEB tank power supplies
  • 2024-11-29-12h38m14-UTC  Disable output of PowerUnit13 (Dboxes power supplies)
    • the line at 8500Hz  move at  9000Hz
  • 2024-11-29-12h40m24-UTC  Disable output of PowerUnit12 (Quadrants and Timing power supplies) 
  • 2024-11-29-12h41m21-UTC  Enable output of PowerUnit12 (Quadrants and Timing power supplies)
    • the noise is reduced when this power supply is OFF but return at the previous level when it is ON
    • second attempt of OFF/ON cycle
      • 2024-11-29-12h43m37-UTC  Disable output of PowerUnit12
      • 2024-11-29-12h44m12-UTC  Enable output of PowerUnit12
    • After this second attempt the noise floor is reduced and remains at the new level when this power supply is ON
  • 2024-11-29-12h46m25-UTC   Enable output of PowerUnit13 (Dboxes power supplies)
  • 2024-11-29-12h53m52-UTC   'Reload config' sent to SWEB_dbox_bench : reconfigure the SWEB tank Daq boxes
    • only the expect line at 9600Hz present with the same low noise floor
• SWEB_LC stopped and restarted
  • 2024-11-29-12h57m11-UTC  process:SWEB_LC stopped
  • 2024-11-29-12h57m22-UTC  process:SWEB_LC started
  • SWEB_LC and SBE loops successfully closed at 2024-11-29-12h58m10-UTC

According to this time sequence, the noise seems related to the  PowerUnit12 or the devices (Quadrants and timing) powered by it .

The last plot show the evolution of some small lines around 10KHz after the restart of the bench

While we were performing these operations, we forgot to disable the WEB ALS BPC. As consequence, the ALS on-call had to realign the SWEB ALS  BPC to allow the ITF lock