1. SPS IMPEDANCE ESTIMATES
BY LUC VOS IN 1986 and 2003
E. Métral
How different are our predictions (for the vertical impedance) compared to the ones from L. Vos?
What are the remaining contributors to the vertical impedance?
Elias Métral, Informal SPS impedance meeting, 12/12/2007

2. from L. Vos (CERN-AB-2003-088 (ABP))
Only dipolar impedance here!!!  L. Vos made an assumption for the quadrupolar term!!!
from L. Vos (CERN-AB (ABP))
Lepton cavities,
all kickers IN
3 MKE OUT
2 MKA OUT,
partial shielding
1 MKA, 3 MKE,
MKLP, lepton
cavities OUT,
all shielding
1 MKE OUT
5 MKE IN
4 MKE IN
Elias Métral, Informal SPS impedance meeting, 12/12/2007

3. Vos’ assumptions
L. Vos considered that the vertical coherent tune shift is made up for 1/3 by the quadrupolar tune shift and for 2/3 by the collective tune shift (i.e. from the dipolar impedance)
Summary for the vertical impedance:
Total imped. meas. by Helmut [M/m]
Dipolar imped. (only) meas. by Helmut assuming factor 2/3 [M/m]
Dipolar imped. (only) computed by Vos assuming factor 2/3 [M/m]
Dipolar imped. (only) meas. quoted by Vos assuming factor 2/3 [M/m]
2001
19.1
12.7 10
12.2
2002
8.7
2003
22.2
14.8 15
2006
23.6
15.7 20
Elias Métral, Informal SPS impedance meeting, 12/12/2007

4. Conclusions and outlook (1/2)
Measurements from Helmut predicts an increase of the total impedance of 4.5 M/m or 3 M/m for the dipolar impedance (assuming the factor 2/3!) between 2001 and 2006
Our prediction for the total impedance increase is 5.2 M/m or 3.5 M/m for the dipolar impedance (assuming the factor 2/3!)
Vos’ prediction is 15 M/m for the total impedance increase or 10 M/m for the dipolar impedance (assuming the factor 2/3!) 
I think one can explain better the impedance increase since 2001
However, one has to look in detail to Vos’ estimate of the impedance in 2001, which seems quite close to the meas. from Helmut, to try and identify our missing contributors
Elias Métral, Informal SPS impedance meeting, 12/12/2007

5. Conclusions and outlook (2/2)
from L. Vos (CERN SPS/86-21(MS))
Elias Métral, Informal SPS impedance meeting, 12/12/2007