MPP Case of SSS009 installed in 33R7

1. MPPCase of SSS009 installed in 33R7 Status of SSS009 in33R7: NC History. Present problem: intermittent open circuit of V-tap EE212 Diagnostics in the tunnel (D. Bozzini and V.Chareyre). Independent diagnostics in the tunnel. Proposal to avoid the problem.

2. SSS009 - NC History • At warm there was no sign of the problem. • List of NC declared in MTF: • Voltage tap position • 13 kA Bus bar: bad condition • Jumper position error • Line X position error • The T value for V1 tube on lyre side is out of tolerance

3. Present problem • Voltage tap EE212: intermittent open circuit vs coil: • The voltage tap EE212 has been found several times open. • The location where the contact disappear seems to be inside the cold mass.

4. Diagnostics in the tunnel (D. Bozzini & V.Chareyre).Courtesy of Vincent Chareyre, presented at MARIC 28.02.2007 • EDMS document 823373 report about this problem: • During first phase of cool-down, the quench protection system of MQ.33R7 was triggered. The cause is an interruption of the voltage-tap EE212 attached to the MQD coil in the internal aperture. The open-circuit has been directly verified by pointing on the PCB in the instrumentation box (pin 23 and not 35 due to a non-conformity opened on surface, EDMS No 590797). • Time Domain Reflectometry shows that the problem is inside the cold mass. • The open-circuit then disappeared.The location of the fault (probably a bad contact) is likely in the cold connection box in the cold mass. This location is confirmed by TDR results.

5. Hardware Commissioning in Sector 7-8: NC in MQ.33R7 Courtesy of Vincent Chareyre, presented at MARIC 28.02.2007 • The Quench Protection System triggered in MQ.33R7 during the cool down phase • The voltage-tap EE212 attached to the MQD coil in the internal aperture of the SSS009 has been found interrupted: EDMS doc. 823373 • The fault appears and disappears: probably a bad contact • Time Domain Reflectometry shows that the fault is far inside the cold mass,very likely at the level of the v-tap connection to the coil • Comparison of TDR traces of a v-tap, a quench heater wire (same path but different system connected) and a free ceramic pin (IFS) Upwards deviation: signature of an open-circuit

6. Independent diagnostics in the tunnel (A.S. G.D. R.M. F.K.) • As decided during last MPP meeting, another independent diagnostic should be done: • Tue. 13th of March, A.S, R.M G.D and F.K confirmed the problem: • The V-tap EE212 was first found connected to coil (seems to be OK). • DC Current flowing through the V-tap EE212 and V-tap EE211 reproduced the problem. • By the time we connected the V-taps to the instruments for phase sensitive Time Domain Reflectometry measurement, the contact got closed again. • Many trials to reproduce the problem did not succeed: the contact remained closed. • The behavior of this contact indicates that the opening of the circuit is most probably due to a cold soldering at the coil level.

7. Proposal to avoid the problem • In order to begin operation with the highest possible degree of redundancy for the Quench Protection System, we propose to replace the non reliable tap EE212 by the potential wire from the by-pass diode busbar EE024 or I-tap EE022 of the same end of the inner coil as the broken wire. • This replacement can be done inside the IFS box. Then the routing of the wires does not require any additional changes. • The non reliable wire shall be isolated inside the IFS box. • As long as there is no current in the cold diode branch the potential of the two taps are identical. In this way the usual detection scheme of two independent signals to two independent detector cards can be maintained (In agreement with Knud DAHLERUP-PETERSEN recommendations). • This magnet should be treated as a specific case for post-mortem analysis.