Damping Ring ImpedanceK. Bane 04/05/2007 ILC DR Impedance Group At SLAC a group has been meeting...
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Damping Ring Impedance K. Bane 04/05/20 ILC DR Impedance Group At SLAC a group has been meeting bi-weekly for ½ year to study ILC DR broad band impedance and impedance effects Focus on the microwave instability; want to insure that ILC operates below threshold Impedance calculations: C. Ng, Z. Li Impedance effects: S. Heifets, A. Novokhatski, G. Stupakov, K. Bane We have no engineering drawings. We generate vacuum chamber components by scaling from existing machines. Pseudo-Green function wakes obtained by numerical calculation. High priority: rf cavities with tapers, bpm’s, resistive wall wake Medium priority: collimators, masks, antichamber slots, feedback kickers, etc (K. Bane, 5 April 07)
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Damping Ring ImpedanceK. Bane 04/05/2007 DR Cavity: Sigma_z=6mm Min/Max = E+00/ 1.620E+00 V/pC Loss Factor = E+00 V/pC F0=650MHz ABCI
Transcript of Damping Ring ImpedanceK. Bane 04/05/2007 ILC DR Impedance Group At SLAC a group has been meeting...
Damping Ring Impedance K. Bane 04/05/2007
ILC DR Impedance GroupAt SLAC a group has been meeting bi-weekly for ½ year to study ILC DRbroad band impedance and impedance effects
Focus on the microwave instability; want to insure that ILC operates below threshold
Impedance calculations: C. Ng, Z. LiImpedance effects: S. Heifets, A. Novokhatski, G. Stupakov, K. Bane
We have no engineering drawings. We generate vacuum chamber components by scaling from existing machines. Pseudo-Green function wakes obtained by numerical calculation.
High priority: rf cavities with tapers, bpm’s, resistive wall wakeMedium priority: collimators, masks, antichamber slots, feedback kickers, etcLow priority: bellows, feedback pick-ups, etc
(K. Bane, 5 April 07)
Damping Ring Impedance K. Bane 04/05/2007
ILC Damping Ring Cavity
• Cornell Model (scaled)
• KEK Model
r= 92 mm r= 25 mm
f0= 650 MHz
(Z. Li)
Damping Ring Impedance K. Bane 04/05/2007
DR Cavity: Sigma_z=6mm
DR Cavity: sigma_z=6mm
-1.0-0.8-0.6-0.4-0.20.00.20.40.60.81.0
0.0 0.1 0.2 0.3 0.4 0.5s (m)
Wak
e_L
L WakeCharge
Min/Max = -2.638E+00/ 1.620E+00 V/pCLoss Factor = -1.455E+00 V/pC
F0=650MHz
ABCI
Damping Ring Impedance K. Bane 04/05/2007
Sigma_z=0.5mm
DR Cavity (scaled Cornell): sigma_z=0.5mm
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07s (m)
W_L
, Q
Long. WakeCharge
DR Cavity (scaled Cornell): sigma_z=0.5mm
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0.00 0.01s (m)
W_L
, Q
Long. WakeCharge
Min/Max = -2.205E+01/ 5.099E+00 V/pCLoss Factor = -1.617E+01 V/pC
F0=650MHz
ABCI
Damping Ring Impedance K. Bane 04/05/2007
ILC DR BPM
10 mm button25 mm
radius
Snapshots of beam transit
= 2 mm
(C. Ng)
T3P
Damping Ring Impedance K. Bane 04/05/2007
Pseudo-Green FunctionA. Novokhatski
Damping Ring Impedance K. Bane 04/05/2007
Outlook
Ideally would like to have wakes for an rms bunch length of ½ mm=> more calculations needed on the bpm’s.
With rf cavity, bpm, and resistive wall impedance we can make “baseline” (conservative) instability calculations. This allows us to find out how much headroom we have—how far below threshold are we with this minimal impedance?
The calculations for medium priority vacuum chamber objects will take some time: there are many objects, and how does one decide which designs will likely be chosen for the ILC?
