Status of SE61 ripple studies

1
Status of SE61 ripple studies

• Aim of the study is to compensate the natural
  modulation of beam intensity on the slow
  extracted beam for the East Hall.
• Ripple comes from the residual undulation on the
  power supplies.
• Leads to a variation in the working point during
  extraction.
• Critical for DIRAC experiment (lt10 ripple).

2
What was done in 1998(97)

• 1997
• natural ripple 85.
• harmonic compensation using air-cooled quad.,
  amplifier GFA.
• 50,100,150,200,300,400 600 Hz compensated.
• Ripple 10.

• 1998
• new quadrupole and amplifier installed.
• Natural ripple gt100.
• Spill structure never stable.
• With feed forward scheme ripple 50.

3
1997
Spill signal without correction
Spill spectrum without correction
Spill signal after correction
Spill spectrum after correction
4
1998
Spill structure without compensation
Spill structure using feed forward compensation
scheme
5
Search for cause of ripple

• All power supplies checked.
• Doubt on figure of 8 loop.
• Power supply frequency spectrum measurements.
• Correlation made with the spill (when possible).
• Feed forward LSD hardware verified.

6
What will be done in 1999

• New LSD hardware (R.M. V.P.).
• new PM tube, low loss cable, direct connection to
  MCR.
• New feed-forward correction programme (J.K.).
• aim to have automatic correction.
• Feedback system under study (J.D. R.S.).
• Empty bucket (200 MHz) scheme to be tested.
• Continue search for elements that are responsible
  for the ripple.