PARTICLES LOST IN THE FIRST TURN
Tracking 1e4 particles. 2~3% are lost in the first turn.
The starting point of the track is s=98.24m.
Most of the particles are lost in the first and second cell (lenght=196.88m)
PARTICLES LOST IN THE FIRST TURN
2~3% of particles are lost in the first turn.
We zoom into the first two cells of the histogram : 196.88m * 2
ALL particles are lost because the horizontal excursion goes further than -50mm away from the
center and hit the beam pipe. NONE hits the opposite side (+50mm).
1) The main location of particle losses is just after the entrance : 98.24~120m.
Explanation : Seems to be the energy loss because they only hit the low energy side.
If it was because of the beam divergence after the target I would expect to loose particles on both sides
of the pipe. So, maybe the energy is simply to low ? See next slide.
2) The second and third most common location of particle loss are close to the peak of horizontal dispersion
ηx.
Explanation : Might be the combination of energy loss and large dispersion. 0.55m*-10%=-55mm
PARTICLES LOST IN THE FIRST TURN
2~3% of particles are lost in the first turn.
The plot shows the energy of the particles and the location where they are lost, with dispersion superimposed.
Case a ) We are OK with particles down to -10% in energy to barely pass at least once through the lattice.
From Francesco’s study of Be target 3mm thick “checks with fluka” 2016/NOV/29 Page 9
https://agenda.infn.it/conferenceDisplay.py?confId=12427
This is equivalent to accept 97.9% of the particles, i. e., 2% particles lost in the first turn.
Some ideas :
1) Reduce dispersion to al least 0.2m, better at least one order of magnitude
2) Increase the beam pipe radius from 50mm to whatever is needed.
3) Correlate the energy with RF phase and compensate the energy loss with an RF cavity
Others...
PARTICLES LOST IN THE FIRST TURN
2~3% of particles are lost in the first turn.
The plot shows the energy of the particles and the location where they are lost, with dispersion superimposed.
Case b ) We want particles down to -20% to pass at least once through the lattice.
From Francesco’s study of Be target 3mm thick “checks with fluka” 2016/NOV/29 Page 9
https://agenda.infn.it/conferenceDisplay.py?confId=12427
This is equivalent to accept 98.6% of the particles, i. e., 1~2% particles lost in the first turn.
Some ideas :
Still dispersion should be lowered or beam pipe radius should be larger because the excursion in
the horizontal plane is in the order of cm !