Warm Snake Commissioning    ... Some incomplete thoughts        ahrens   3mar04

 

 

Protons accelerating in AGS with the new snake off.

 

 ____            L15norm beam current signal displayed on scope.  Store a typical shot.

 

____    AGS Orbit Display program: save a typical orbit taken at 10 ms after injection.

 

____    AGS loss monitor program: save the loss pattern for a window looking enough after injection to avoid the injection caused losses. Set maybe window edges every 5 ms from injection to beyond 30 ms.

 

 

Bring  E20 snake to about full current. (Full current is 2671A).

 

Does the beam still survive? (more that 50% 20 ms after injection).

 

If no then reduce the snake current until answer is yes.

 

So now the answer is yes and hopefully the magnet current is not zero.

 

            Where are the new losses?

 

                        If right at the snake - scraping inside - try to reduce by shifting the ags orbit inside the snake. Since the loss is surely right at injection, cannot use the radial shifting provided by the rf. Could change AGS field, but possibly too painful at first. Use a bump in the AGS Orbit Control program to move horizontally at E20, and perhaps vertically at E20. I put some info in the presently active pp elog. Such a bump is already built. This will give probably a cm of motion before dipoles are used up. Learn from this at least which direction is the right one. One could shift the orbit with the field. In full glory, this would require a full redo of the injection setup - bumps. Since we are not yet "synchroed" to Booster, is a good thing to get done.

 

            Take a difference orbit against  the orbit saved with the snake off.

 

            Expect "cusps" in both h and v at E20 and resulting oscillations around the machine. Correct - minimize -the 8th and 9th harmonic components of the difference orbit.

 

            If working at less than full snake field, and if losses are removed, take 'er up.

 

            If losses appear, repeat previous steps.