1
CONSIDERATIONSON WARM MAGNET MEASURED
DOSES
2012 September 3rd
Francesco Cerutti
for the team
key contributions by
TE-MSC Davide Tommasini and Pierre Thonet
DGS-RP Julia Trummer, Christophe Tromel, Frederic
Jaquenod
Markus Brugger Luigi Esposito
2012 September 3rd F. Cerutti CWG#147 2
• losses sharing (additional passive absorber in P3?)
• losses scaling (warm magnet lifetime)
• measurements vs expectations
• reasons for caution
OUTLINE
2012 September 3rd F. Cerutti CWG#147
2012 (until June) from the TCP HL dosimeters
Proton losses in P3 of the order of [several] % wrt P7 tight collimator
settings
beam 1 / beam 2 ratios consistent with 2011
measured MQW doses reflect the P3 vs P7 sharing 6.5 kGy vs 60 kGy (~10%) for beam 1
and the lack of TCAPC in P3: 2.5 kGy vs 45 kGy (~5%) for beam 2
3
2011 from the TCP BLMs
Proton losses in P3 and in P7 of the same order (within a factor of 3)
beam 1 / beam 2 ~ 2 in P3 and ~ 0.5 in P7
LOSSES SHARING
>
?
P3 P7
measured MBW doses reflect the P3 vs P7 sharing: 9-16 kGy vs 100-400 kGy (~5%) for beam 1
2-5 kGy vs 330-490 kGy (~1%) for beam 2
additional passive absorber in P3 not justified with this P3 vs P7 sharing, BUT
the latter (dramatically) depends on the collimator settings (see 2011)
2012 September 3rd F. Cerutti CWG#147 4
2012 (until June) from BCT & LUMI (injected ― dumped ― collided)
1.45 [1.7] 1015 beam 1 [2] protons lost (in the collimators) for ~7fb-1 per experiment
LOSSES SCALING
not the factor of 2?tentative extrapolations (assuming linearity between losses and luminosity, despite the energy upgrade):
1.1 1016 for 50fb-1 (one year?) projected MBW dose: 5 MGy including a factor of 2 for 7TeV operation
projected MQW dose: 0.7 MGy
6.5 1016 for 300fb-1 (until LS3??) projected MBW dose: 30 MGy
projected MQW dose: 4-5 MGy
2012 September 3rd F. Cerutti CWG#147
100-400 kGy
60 kGy
one would getby normalizing to1.4 1015 beam 1 protons lost in P7
IP7TCP.D C B 6L7.B1
v h s
MBW
MQW
beam 1
s
TCAP
5
assuming a horizontal halo
for 1.15 1016 lost protons per beam
MEASUREMENTS VS EXPECTATIONS
peak dosefor intermediatecollimator settings
taking for 4 TeVwith tight settings
2 250kGy
0.5 60 kGymeasured
2012 September 3rd F. Cerutti CWG#147 6
RADIAL AND AZIMUTHAL GRADIENT (MBW)
M. Brugger, Jun 2008
397.5 kGy
> 500 kGy
106.3 kGy
119.8 kGy
J. Trummer
beam 1 entering
x
beam 1 pointing outwards
0.2h beam lifetime
250kGy
250kGy
~3 MGy
assuming a horizontal halo
0.5mm x 0.5mm transverse
resolution
1cm x 1cm transverse
resolution
2012 September 3rd F. Cerutti CWG#147
fallen off(487.3 kGy)
25.7 kGy
100.4 kGy
59.6 kGy
7
RADIAL AND AZIMUTHAL GRADIENT (MQW)
J. Trummer
beam 1 entering
x 60kGy
1cm x 1cmtransverse resolution
~ MGy0.5mm x 0.5mm transverse
resolution
beam 1 pointing outwards
x
2012 September 3rd F. Cerutti CWG#147 8
REASONS FOR CAUTION
252.7 kGy
289.7 kGy171.8 kGy
26.5 kGy
J. Trummer
factor 1.7 ?
factor 10 ??
(much more) controlled loss term: p-p collision debris (vertical crossing)
P1
Conversely, BLMs indicates the expected left-right symmetry
2012 September 3rd F. Cerutti CWG#147 9
CONCLUSIONS Measured doses on the MQWs in Point 3 do not exceed 10% of the ones in Point 7
for the 2012 Feb-Jun collimator settings implying a (strongly) asymmetric sharing of losses
(in P3 few-several percent of P7). Different operation conditions can move the MQW weak point
in P3, with
peak doses – for the same number of integrated losses – possibly higher than those measured in
P7
Doses on the D1 MBWs in P1 (and P5) are of the same order as in the collimation region
400 kGy on the MBW and 50 kGy on the MQW for 1.5 1015 lost protons (corresponding to 7fb-
1)
give a projection of 30 MGy on the MBW and 5 MGy on the MQW for 6.5 1016 lost protons (300fb-
1), at
the levels of the expected failure thresholds. These estimates have to be intended in terms of
orders of
magnitude due to the uncertainties in measurements and losses extrapolation (barely within a
factor of 2) A quite reasonable consistency with predictions from simulations was found (though this,
contrary to others
already available, is far from being a clean benchmarking case)
A hard limit of 0.5 MGy on the HLDosimeters’ reading would imply their timely
replacement. Calibration
up to 5 MGy viable?