Download MPP_Orbit_07052008

MPP
Result of the investigation in the orbit
correctors faults.
 RCBV27.L6B2 – High value of
magnet resistance during PNO.a1
 RCBCV10.L6B1 – EE811 voltage tap
missing
MPP Meeting 07/05/2008
G. D’Angelo – R. Mompo
RCBV27.L6B2 – Status of PNO.a1 analysis on 16/04/2008
Status faced when the test PNO.a1 was executed (16/04/2008):
The resistance of the magnet is higher than the criteria !!
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBV27.L6B2 – PNO.a1 – Current cycle and circuit
R_Cable_Pos
R_Lead_Pos
U_LEAD_POS
RCBV27.L6B2 - PNO.a1
LCIRCUIT
V_MEAS
U_LEAD_NEG
6
R_Cable_Neg
U_TOT
80
R_Lead_Neg
60
V_MEAS
4
U_LEAD_POS
40
U_LEAD_NEG
I_MEAS
20
0
0
200
400
600
800
1000
1200
1400
1600
0
1800
-20
-2
-40
-4
-60
-6
MPP Meeting 07/05/2008
-80
time [s]
G.D’Angelo – R. Mompo
Current [A]
Voltage [V]
2
RCBV27.L6B2 – PNO.a1 – Criteria and calculation
U_TOT = V_MEAS – (U_LEAD_POS +
U_LEAD_NEG) – U(R_serie)
During plateau:
R_Magnet = U_TOT / I_PNO
<3.5 e-3 Ohm
Edms : 874724
Data from 16/04/08 during plateau:
V_Meas= 2.63 V; U_LEADs=0.068 V
U(R_serie)= 2.81 V.
R_Magnet = -4.5e-3 Above the limit and
negative !!
R_Cable_Pos
R_Lead_Pos
U_LEAD_POS
V_MEAS
LCIRCUIT
U_LEAD_NEG
R_Cable_Neg
R_Lead_Neg
R_serie = R_Cable_Pos
+ R_Cable_Neg
LHC Layout Database
(05.05.2008)
R_serie=0.051 Ohm
Measurement of R_serie repeated
05/05/2008  0.0475 Ohm
R_Magnet updated: 1.08 e-3 Ohm, OK !!
(with offset corrections)
MPP Meeting 07/05/2008
U_TOT
LHC Layout Database
(05.05.2008 )
R_serie=0.0475 Ohm
G.D’Angelo – R. Mompo
RCBV27.L6B2 – PNO.a1 – PASSED with the updated R_serie
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBV27.L6B2
 Conclusion:
The PNO.a1 cycle should be repeated on RCBV27.L6B2 in order to
make sure that the measurement of DC warm cables performed
on 05/05/2008 did not altered the circuit.
Then the NC should be closed.
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
MPP
Result of the investigation in the orbit
correctors faults.
 RCBV27.L6B2 – High value of magnet
resistance during PNO.a1
 RCBCV10.L6B1 – EE811 voltage tap
missing
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBCV10.L6B1 – EE811 voltage tap missing



Chronology of events:
On 11/03/2008, RCBCV10.L6B1 circuit was successfully qualified
by ELQA team.
On 14/04/2008, AB/PO can not power this circuit, they have a
fault on the PC.
On 16/04/2008, EE811 (cold voltage tap) is found open, directly
from the feed through pin coming from the cover flange => NC
908215 opened.
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBCV10.L6B1 – EE811 voltage tap missing

On 05/05/2008:
Intervention to perform a time domain reflectometry to localize
precisely the defect. It is repairable if it is at the level of the cover
flange.
Surprise! The voltage tap EE811 is back!
Impossible to make a reflectometry as there is no defect
anymore, so I did a few ohmic measurements to check all the
voltage taps.
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBCV10.L6B1 – EE811 voltage tap missing

Measurements on the external « sick » orbit dipole:

For comparison, measurements on the internal dipole:
*: Measurement performed with a portable multimeter.
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo
RCBCV10.L6B1 – EE811 voltage tap missing
 Conclusion:
AB/PO have no more interlocks, they can now power the magnet
to qualify the circuit (checked with V. Montabonnet) with the
circuit as is.
Proposal:
We could try to reproduce the defect, by feeding a current of 2
Amps through the voltage taps.


If the voltage tap remains connected, we close the NC.
If we manage to open the vtap, we perform a time domain reflectometry.
MPP Meeting 07/05/2008
G.D’Angelo – R. Mompo